piperidines and mepiquat

In the present study, new methylating agents for the formation of N,N-dimethylpiperidinium (mepiquat) were evaluated in both model and mushroom systems. Mepiquat levels were monitored using five model systems; alanine (Ala)/pipecolic acid (PipAc), methionine (Met)/PipAc, valine (Val)/PipAc, leucine (Leu)/PipAc, and isoleucine (Ile)/PipAc. The highest level of mepiquat was 1.97% at 260 °C for 60 min (Met/PipAc model system). Piperidine can actively combine with methyl groups in thermal reactions to form N-methylpiperidine and mepiquat. Additionally, mushrooms rich in amino acids were oven baked, pan cooked, and deep fried, respectively, to investigate the formation of mepiquat. Oven baking led to the highest mepiquat content of 63.22 ± 0.88 μg/kg. In summary, food constituents are the main source of precursors for mepiquat formation, the mechanism of which has been presented in both model systems and mushroom matrices rich in amino acids.

Topics: Agaricales; Amino Acids; Cooking; Isoleucine; Leucine; Methionine; Piperidines

Mepiquat chloride (DPC) enhances the resistance of cotton plants, and it is widely used as a growth regulator. DPC can stimulate photosynthesis, stabilize the structure of cotton leaves, and affect population reproduction and energy substances in Aphis gossypii Glover (cotton aphids), but interactions between DPC and cotton aphids remain unclear. In this study, we analyzed the physiological responses of cotton to DPC, and the toxicity of DPC toward cotton aphids, before and after feeding, to explore the DPC-induced defense mechanism against cotton aphids.. Measurements of protective enzyme activity in cotton showed that the soluble protein contents, peroxidase (POD) activity, and catalase (CAT) activity in cotton treated with different concentrations of DPC were higher than in the control. Superoxide dismutase (SOD) activity was higher than that of the control when the concentration of DPC was < 0.1 g/L. Under aphid feeding stress, POD activity in cotton treated with a low insect population density was significantly lower than in the controls, but the reverse was true for cotton treated with a high insect population density, and SOD activity was positively correlated with population density. The activities of detoxification enzymes in field and laboratory experiments showed that DPC promoted the specific activity of glutathione S-transferase (GST) in cotton aphids, while the specific activities of carboxylesterase (CarE) and acetylcholinesterase (AchE) were decreased.. DPC enhanced the aphid resistance in cotton by increasing the soluble protein content and the activity of protective enzymes. It also had a toxic effect on cotton aphids by increasing GST activity (the main DPC target). DPC increased the soluble protein content and protective enzymes activity in cotton under aphid stress, and thereby enhanced tolerance to cotton aphids. It conclude that DPC interferes with cotton aphids through indirect (DPC induced cotton defense responses) and direct (DPC toxicity to cotton aphids) ways, which plays a positive role in interfering with cotton aphids.

Topics: Acetylcholinesterase; Animals; Aphids; Gossypium; Piperidines; Superoxide Dismutase

Mepiquat chloride (MC) is a plant growth regulator widely used in cotton production to control vegetative overgrowth of cotton plants to achieve ideal plant architecture required for high yielding. Cotton varieties respond differently to MC application, but there is little information about the molecular mechanisms underlying the varietal difference. In this study, comparative transcriptome analysis was conducted by using two Upland cotton varieties with different sensitivity (XLZ74, insensitive; SD1068, sensitive) to MC treatment, aiming to understand the molecular mechanisms responsible for varietal difference of MC sensitivity. RNA-seq data were generated from the two varieties treated with MC or water at three time points, 1, 3 and 6 days post-spray (dps). Genes differentially expressed between the MC and mock treatments of XLZ74 (6252) and SD1068 (6163) were subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses to compare the enriched GO terms and KEGG pathways between the two varieties. Signal transduction of phytohormones, biosynthesis of gibberellins (GAs) and brassinosteroids (BRs) and profiles of transcription factors (TFs) seemed to be differentially affected by MC in the two varieties. The transcriptomic results were further consolidated with the content changes of phytohormones in young stem. Several GA catabolic genes,

Topics: Gene Expression Profiling; Gene Expression Regulation, Plant; Gossypium; Piperidines; Plant Growth Regulators; Transcriptome

Cotton (Gossypium hirsutum L.) is one of the most important cash crops primarily grown for fiber. It is a perennial crop with indeterminate growth pattern. Nitrogen (N) is extremely important for vegetative growth as balanced N-nutrition improves photosynthesis, resulting in better vegetative growth. Excessive N-supply results in more vegetative growth, which increases the incidence of insect pest and diseases' infestation, pollute surface and ground water, delays maturity and produces low crop yield with poor quality. The use of plant growth regulators (PGRs) is an emerging option to control excessive vegetative growth. The PGRs help in improving plant architecture, boll retention, boll opening, yield and quality by altering growth and physiological processes such as photosynthesis, assimilate partitioning and nutrients dynamic inside the plant body. Mepiquat chloride (1,1-dimethylpiperidinum chloride) is globally used PGR for canopy development and control of excessive vegetative growth in cotton. This study investigated the effect of mepiquat chloride (MC) and N application on yield and yield components of transgenic cotton variety 'BT-FSH-326'. Two N rates (0, 198 kg ha-1) and five MC rates (0, 30,60, 90 and 120 g ha-1) were included in the study. Results revealed that MC and N application improved boll weight, number of bolls per plant, and seed cotton and lint yields. The highest seed cotton and lint yields (3595 kg ha-1 and 1701 kg ha-1, respectively) were observed under foliar application of 198 kg ha-1 N and 120 g ha-1 MC. Fiber length, fiber strength, micronaire and uniformity were significantly improved with foliar application of MC and N. In conclusion, foliar application of MC and N could be helpful in improving yield and fiber quality of cotton.

Topics: Cotton Fiber; Gossypium; Nitrogen; Piperidines; Plant Growth Regulators

N,N-dimethylpiperidinium (mepiquat) is an important food contaminant formed from natural ingredients during thermal processing. In this study, mepiquat formation in meat (pork and beef) and vegetables (potatoes and broccoli) was investigated via HPLC-MS/MS; the investigated cooking methods were oven baking, pan cooking, deep frying, and microwaving. The results showed that, among all foods, oven-baked potatoes showed the highest mepiquat level of 1064 μg/kg, which appeared after 20 min at 240 °C. The residual rates of mepiquat precursors, pipecolic acid (PipAc), betaine, choline, and trigonelline, were determined in oven-baked potatoes to investigate their correlation with mepiquat formation. The PipAc levels reduced by 99.8% at 260 °C after 30 min of oven baking, exhibiting a significantly high decomposition rate. Therefore, PipAc could be used as a marker of quality for the detection of mepiquat in thermally processed foodstuffs.

Topics: Animals; Cattle; Hot Temperature; Meat; Piperidines; Tandem Mass Spectrometry; Vegetable Products

Mepiquat chloride (DPC) is a chemical that is extensively used to control internode growth and create compact canopies in cultured plants. Previous studies have suggested that DPC could also inhibit gibberellin biosynthesis in sugarcane. Unfortunately, the molecular mechanism underlying the suppressive effects of DPC on plant growth is still largely unknown.. In the present study, we first obtained high-quality long transcripts from the internodes of sugarcane using the PacBio Sequel System. A total of 72,671 isoforms, with N50 at 3073, were generated. These long isoforms were used as a reference for the subsequent RNA-seq. Afterwards, short reads generated from the Illumina HiSeq 4000 platform were used to compare the differentially expressed genes in both the DPC and the control groups. Transcriptome profiling showed that most significant gene changes occurred after six days post DPC treatment. These genes were related to plant hormone signal transduction and biosynthesis of several metabolites, indicating that DPC affected multiple pathways, in addition to suppressing gibberellin biosynthesis. The network of DPC on the key stage was illustrated by weighted gene co-expression network analysis (WGCNA). Among the 36 constructed modules, the top positive correlated module, at the stage of six days post spraying DPC, was sienna3. Notably, Stf0 sulfotransferase, cyclin-like F-box, and HOX12 were the hub genes in sienna3 that had high correlation with other genes in this module. Furthermore, the qPCR validated the high accuracy of the RNA-seq results.. Taken together, we have demonstrated the key role of these genes in DPC-induced growth inhibition in sugarcane.

Topics: Gene Expression Profiling; Gene Expression Regulation, Plant; Piperidines; Saccharum; Transcriptome

The present study aimed at incorporating active renal excretion via the organic cation transporter 2 (OCT2) into a generic rat physiologically based kinetic (PBK) model using an in vitro human renal proximal tubular epithelial cell line (SA7K) and mepiquat chloride (MQ) as the model compound. The Vmax (10.5 pmol/min/mg protein) and Km (20.6 μM) of OCT2 transport of MQ were determined by concentration-dependent uptake in SA7K cells using doxepin as inhibitor. PBK model predictions incorporating these values in the PBK model were 6.7-8.4-fold different from the reported in vivo data on the blood concentration of MQ in rat. Applying an overall scaling factor that also corrects for potential differences in OCT2 activity in the SA7K cells and in vivo kidney cortex and species differences resulted in adequate predictions for in vivo kinetics of MQ in rat (2.3-3.2-fold). The results indicate that using SA7K cells to define PBK parameters for active renal OCT2 mediated excretion with adequate scaling enables incorporation of renal excretion via the OCT2 transporter in PBK modelling to predict in vivo kinetics of mepiquat in rat. This study demonstrates a proof-of-principle on how to include active renal excretion into generic PBK models.

Topics: Animals; Cell Line; Epithelial Cells; Humans; Kidney; Kidney Tubules, Proximal; Models, Biological; Organic Cation Transporter 2; Piperidines; Plant Growth Regulators; Rats

Potassium deficiency causes severe losses in yield and quality in crops. Mepiquat chloride, a plant growth regulator, can increase K+ uptake in cotton (Gossypium hirsutum), but the underlying physiological mechanisms remain unclear. In this study, we used a non-invasive micro-test technique to measure K+ and H+ fluxes in the root apex with or without inhibitors of K+ channels, K+ transporters, non-selective cation channels, and plasma membrane H+-ATPases. We found that soaking seeds in mepiquat chloride solution increased the K+ influx mediated by K+ channels and reduced the K+ efflux mediated by non-selective cation channels in cotton seedlings. Mepiquat chloride also increased negative membrane potential (Em) and the activity of plasma membrane H+-ATPases in roots, due to higher levels of gene expression and protein accumulation of plasma membrane H+-ATPases as well as phosphorylation of H+-ATPase 11 (GhAHA11). Thus, plasma membrane hyperpolarization mediated by H+-ATPases was able to stimulate the activity of K+ channels in roots treated with mepiquat chloride. In addition, reduced K+ efflux under mepiquat chloride treatment was associated with reduced accumulation of H2O2 in roots. Our results provide important insights into the mechanisms of mepiquat chloride-induced K+ uptake in cotton and hence have the potential to help in improving K nutrition for enhancing cotton production.

Topics: Cell Membrane; Gibberellins; Gossypium; Hydrogen Peroxide; Piperidines; Plant Roots; Proton-Translocating ATPases

Use of growth retardants enables post-planting optimization of vegetative growth, which is particularly important given ongoing climate change. Mepiquat chloride is an economical and safe retardant widely applied in cotton farming, but it is not uniformly effective. Here, identification of its molecular target as the ent-copalyl diphosphate synthase that initiates gibberellin biosynthesis enabled the introduction of selective agrochemical inhibition, leaving intact more specialized metabolism important for resistance to biotic and abiotic stresses.

Topics: Alkyl and Aryl Transferases; Arabidopsis; Edible Grain; Gibberellins; Gossypium; Herbicides; Piperidines; Plant Proteins; Plants, Genetically Modified; Zea mays

N,N-dimethylpiperidinium (mepiquat) is a new process-induced compound formed from natural constituents during the cooking process. Mepiquat was first found in coffee and cereal products, but its formation mechanism in coffee is still unclear. In the current study, Arabica and Robusta coffee beans were roasted at different temperatures (215, 220, and 230 °C) to study the effect of roasting process on mepiquat formation. The highest mepiquat content, 1,020 µg/kg, was found in dark roast (230 °C) Indonesia Wahana, while 430 µg/kg of mepiquat was detected in medium roast (220 °C) Vietnam Robusta. At the same roasting temperature, higher level of mepiquat was observed in Arabica than in Robusta. In both species, substances related to mepiquat formation, including betaine, choline, trigonelline, lysine, carnitine, pipecolic acid (PipAc), pipecolic acid betaine (PipBet), were also detected. The lysine-based Maillard reaction and decarboxylation in Arabica and Robusta promoted mepiquat formation through the degradation of choline and trigonelline, and the formation of intermediate products. Results from both the model system and selected commercial beans showed that choline and trigonelline had a significant correlation (P < 0.01) with mepiquat formation in Arabica. PRACTICAL APPLICATION: Mepiquat is considered as a new process-induced compound resulting from typical roasting conditions, but its formation mechanism in coffee is still unclear. This work demonstrates the formation mechanism of mepiquat by many precursor substances contained in Arabica and Robusta. It is very important to figure out how mepiquat is ''naturally" present in daily diets, especially in those processed at high temperatures.

Topics: Alkaloids; Coffea; Coffee; Cooking; Hot Temperature; Indonesia; Maillard Reaction; Pipecolic Acids; Piperidines; Seeds

Mepiquat chloride (MC), a plant growth regulator, enhances root growth by promoting lateral root formation in cotton. However, the underlying molecular mechanisms of this phenomenon is still unknown.. In this study, we used 10 cotton (Gossypium hirsutum Linn.) cultivars to perform a seed treatment with MC to investigate lateral root formation, and selected a MC sensitive cotton cultivar for dynamic monitor of root growth and transcriptome analysis during lateral root development upon MC seed treatment.. The results showed that MC treated seeds promotes the lateral root formation in a dosage-depended manner and the effective promotion region is within 5 cm from the base of primary root. MC treated seeds induce endogenous auxin level by altering gene expression of both gibberellin (GA) biosynthesis and signaling and abscisic acid (ABA) signaling. Meanwhile, MC treated seeds differentially express genes involved in indole acetic acid (IAA) synthesis and transport. Furthermore, MC-induced IAA regulates the expression of genes related to cell cycle and division for lateral root development.. Our data suggest that MC orchestrates GA and ABA metabolism and signaling, which further regulates auxin biosynthesis, transport, and signaling to promote the cell division responsible for lateral root formation.

Topics: Gene Expression Profiling; Gene Expression Regulation, Plant; Gossypium; Homeostasis; Organogenesis, Plant; Piperidines; Plant Growth Regulators; Plant Roots

In this study, a two-dimensional liquid chromatography tandem mass spectrometry method was developed and validated for the determination of pesticide residues and contaminants in whole wheat grains and oats. The samples were extracted with a mixture of acetonitrile and water and were injected into the two-dimensional LC-MS/MS system without any further clean-up or sample preparation. Samples were analyzed with four different matrix matched calibrations. Matrix effects were evaluated by comparing analyte signals in the respective matrix matched standard with the neat solvent standards. The final method was validated according to the current Eurachem validation guide and SANTE document. The number of successfully validated analytes throughout all three validation levels in oats and wheat, respectively, were as follows: 330 and 316 out of 370 pesticides, 6 and 13 out of 18 pyrrolizidine alkaloids and 7 out of 9 regulated mycotoxins. Moreover, both plant growth regulators mepiquat and chlormequat as well as the tropane alkaloids atropine and scopolamine met the validation criteria. The majority of pesticides showed limits of detection below 1 µg kg

Topics: Avena; Chlormequat; Chromatography, Liquid; Food Analysis; Food Contamination; Limit of Detection; Mycotoxins; Online Systems; Pesticide Residues; Piperidines; Plant Growth Regulators; Pyrrolizidine Alkaloids; Reproducibility of Results; Tandem Mass Spectrometry; Triticum; Tropanes

Topics: Calibration; Chlormequat; Chromatography, Liquid; Diquat; Food Analysis; Hordeum; Paraquat; Pesticides; Piperidines; Quaternary Ammonium Compounds; Tandem Mass Spectrometry; Triticum

Carnitine is demonstrated as an effective methyl donor in the formation of the plant growth regulator N, N-dimethylpiperidinium (mepiquat), encompassing either N-methylation/decarboxylation of pipecolic acid, or Maillard pathways followed by transmethylation reactions. The formation of mepiquat and the intermediate compounds was monitored (180-300 °C, up to 180 min) using HPLC-MS/MS in different binary or ternary model systems composed of (i) lysine/fructose/carnitine, (ii) lysine/glucose/carnitine, or (iii) pipecolic acid (PipAc)/carnitine. The highest yield of mepiquat was 2.4% after 120 min incubation at 290 °C (PipAc/carnitine model system). The highest yield was recorded in fructose and glucose (Maillard) systems after 180 min at 230 °C. The full-scan mode was used to monitor the formation of the corresponding intermediates (piperidine and N-methylpiperidine, the demethylated intermediates of carnitine). The new pathways of mepiquat formation indicate that the occurrence of low levels of this thermally induced compound is potentially more widespread in some selected cooked foodstuffs. For the first time, mepiquat was detected in oven-cooked beef, reaching up to 82.5 μg/kg. These amounts are not expected to significantly contribute to the overall exposure via different foodstuffs, as reported in previous studies.

Topics: Carnitine; Chromatography, High Pressure Liquid; Hot Temperature; Maillard Reaction; Methylation; Pipecolic Acids; Piperidines; Plant Growth Regulators; Tandem Mass Spectrometry

Mepiquat chloride (MC) is a plant growth regulator widely used in cotton (Gossypium hirsutum L.) production to suppress excessive vegetative growth, increase root growth and avoid yield losses. To increase root growth, cotton seeds were treated with MC to increase the number of lateral root (LRs) and improve drought resistance. An increased indole-3-acetic acid (IAA) pool appeared to correlate with LR growth, and the principal source of IAA in germinating seeds is IAA conjugates. Here, the role of IAA homeostasis and signaling was investigated in cotton seedlings treated with MC.. In the present research, MC significantly increased endogenous IAA levels in the roots, which promoted lateral root initiation (LRI) by upregulating GhARF7/19 and GhLBD18s and subsequently increasing LR quantity and elongation. The levels of IAA-amide conjugates significantly decreased in MC-treated seedlings compared with untreated control seedlings. Sixteen members of the cotton IAA amidohydrolase (IAH) gene family were identified, of which GhIAR3a, GhIAR3b, GhILR1, GhILL3 and GhILL6 were expressed during cotton seed germination. Compared with those in untreated control seedlings, the expression levels of GhIAR3a, GhIAR3b, GhILR1 and GhILL6 in the MC-treated seedlings were markedly elevated. The GhIAR3a/b and GhILR1 genes were cloned and expressed in Escherichia coli; these recombinant proteins exhibited hydrolytic activity that could cleave IAA-phenyalanine (Phe), IAA-methionine (Met), IAA-glycine (Gly) and IAA-leucine (Leu) in vitro, while only GhIAR3a hydrolyzed IAA-alanine (Ala) efficiently. The content of GhIAR3a, as detected via an established sandwich enzyme-linked immunosorbent assay (ELISA), increased in the MC-treated seedlings compared with the untreated control seedlings. In addition, the Arabidopsis iar3 mutant was less responsive to MC-induced LR growth than was wild type.. These findings suggested that MC application could mediate IAA homeostasis via increased IAA levels from IAA-amide conjugate hydrolysis by accelerating IAH gene expression, which might promote LRI and increase the LR quantity and elongation.

Topics: Amidohydrolases; Animals; Antibodies, Monoclonal; Arabidopsis; Arabidopsis Proteins; Cloning, Molecular; Enzyme-Linked Immunosorbent Assay; Gene Expression Regulation, Plant; Gossypium; Homeostasis; Indoleacetic Acids; Mice; Mutation; Piperidines; Plant Growth Regulators; Plant Proteins; Plant Roots; Seedlings

Mepiquat (N,N-dimethylpiperidinium) is a plant growth regulator registered for use as its chloride salt in many countries on cereals and other crops. Recent model system studies have shown that natural chemicals present in crop plants, such as pipecolic acid and pipecolic acid betaine, may furnish mepiquat through different chemical pathways, when subjected to temperatures in the range of 200°C. In this study, we cooked raw vegetables that did not contain mepiquat to a palatable state using different traditional cooking methods, and detected mepiquat in 9 out of 11 oven-cooked vegetables, reaching up to 189μg/kg dry wt in oven-cooked broccoli. Commercial oven potato fries generated mepiquat during cooking, typically in the range of 20-60μg/kg. Only traces of mepiquat (<5μg/kg) were found in commercial potato crisps. This work demonstrates that mepiquat occurs at μg/kg levels in a variety of cooked vegetables, including potatoes.

Topics: Betaine; Cooking; Hot Temperature; Pipecolic Acids; Piperidines; Solanum tuberosum; Vegetables

This study described the development and validation of a simple, rapid, specific and sensitive method for detecting chlormequat chloride (CQ) and mepiquat chloride (MQ) residues in tomato cultivation matrices covering soil, water, seedling samples. The dissipation rates of CQ and MQ in tomato cultivation matrices were also determined in this study. A Hydrophilic Interaction Liquid Chromatography (HILIC) column was used for chromatographic separation. A triple quadrupole mass spectrometer equipped with an electrospray ionisation source in positive ion mode by multiple reaction monitoring was used for detection. Soil samples were extracted with accelerated solvent extraction (ASE) and cleaned up with WCX phase extraction column; water samples were extracted with WCX phase extraction column; seedling samples were extracted with methanol-ammonium acetate solution. LODs and LOQs of CQ and MQ were 0.02μg/kg and 0.1μg/kg in soil samples, 0.005ng/mL and 0.02ng/mL in water samples, and 0.05μg/kg and 1.0μg/kg in seedling samples, respectively. The mean recovery rate of CQ in soil, water and seedling samples ranged from 76.98% to 111.60%. While the mean recovery rate of MQ in soil, water and seedling samples ranged from 96.90% to 105.40%. The fastest to the slowest metabolising rates of CQ and MQ were as follows: soil samples>seedling samples>water samples. In conclusion, this study provided a new potential method for detecting CQ and MQ in tomato cultivation matrices using ultra-performance liquid chromatography-tandem mass spectrometry.

Topics: Agriculture; Chlormequat; Chromatography, High Pressure Liquid; Drug Residues; Limit of Detection; Linear Models; Piperidines; Plant Growth Regulators; Reproducibility of Results; Seedlings; Soil; Solanum lycopersicum; Solid Phase Extraction; Tandem Mass Spectrometry

This study describes, for the first time, the role of pipecolic acid betaine and pipecolic acid, naturally present in some foods, in the formation of the plant growth regulator N,N-dimethylpiperidinium (mepiquat) under dry thermal conditions. The formation of mepiquat and intermediate compounds was investigated in model systems using high performance liquid chromatography-quadrupole/time-of-flight mass spectrometry. Mepiquat is released with a yield of up to 0.66mol% after thermal treatment (>150°C) of pipecolic acid betaine. Similar conversion rates are attained with the congener piperidine-2-carboxylic acid (dl-pipecolic acid), albeit in the presence of alkylating agents, such as choline, glycine betaine or trigonelline, that are fairly widespread in food crops. These new pathways to mepiquat indicate that the occurrence of low levels of this thermally induced compound is probably more widespread in processed foods than initially suspected (see Part 2 of this study on the occurrence of mepiquat in selected foodstuffs).

Topics: Betaine; Chromatography, Liquid; Decarboxylation; Food Handling; Hot Temperature; Mass Spectrometry; Pipecolic Acids; Piperidines

Mepiquat, a growth regulator widely used in agriculture, is also known as a process-induced byproduct formed in coffee from natural constituents during heat treatments such as roasting. This study examines mepiquat formation in cereal-based foodstuffs treated at sufficiently high temperature to trigger methyl transfer reactions that involve glycine betaine and choline naturally present in cereals. Color measurements of roasted barley grains revealed a correlation between thermal treatment and mepiquat content. Trials at industrial scale on instant beverages composed of roasted cereals demonstrated significant increases in mepiquat during the thermal process (in the range of 140-205 μg/kg in final products). A targeted survey of commercial products showed mepiquat in the range 69-381 μg/kg in powdered cereal instant drinks and 42-168 μg/kg in mugicha tea, a roasted barley infusion. These findings will not significantly affect the exposure of consumers to mepiquat due to the low amounts detected.

Topics: Betaine; Beverages; Cooking; Edible Grain; Hordeum; Hot Temperature; Piperidines

This preliminary study reports for the first time the formation of N,N-dimethylpiperidinium (also termed mepiquat, a plant growth regulator used widely on cereal crops) by Maillard-driven degradation of lysine under dry thermal conditions and in the presence of the naturally occurring alkaloid trigonelline. The heat treatment was carried out at 240°C, and the resulting samples were analysed by liquid chromatography coupled to a high-resolution mass spectrometer (LC-HRMS) operating based upon Orbitrap technology. Results confirmed that lysine undergoes cyclisation by decarboxylative deamination in the presence of a carbonyl source (e.g. reducing sugars) to yield piperidine. Moreover, methyl rearrangement in the presence of trigonelline and under typical temperatures of roasting generates detectable amounts of mepiquat, identified by detailed mass fragmentation studies. The essential role of lysine in the formation of mepiquat was confirmed in a model system using (13)C₆-lysine, which showed the expected incorporation of five (13)C atoms into the mepiquat nitrogen heterocycle. These findings are relevant to the potential occurrence of mepiquat in roasted products such as coffee and cereals.

Topics: Alkaloids; Food Analysis; Hot Temperature; Lysine; Piperidines; Plant Growth Regulators

Previous work in model systems has demonstrated that mepiquat can be formed under typical roasting conditions from the amino acid lysine via the Maillard reaction and trigonelline, the latter alkaloid serving as a methyl donor. This study shows for the first time that mepiquat is formed in low mg kg(-1) amounts during the coffee roasting process and consequently can be detected in roast and ground as well as soluble coffee up to levels of 1.4 mg kg(-1). Darker roast coffees contain relatively higher amounts of mepiquat versus light roasted beans, with an excellent correlation of mepiquat formation to roast colour (r(2) = 0.99) in robusta beans. A survey of 20 of the major green coffee origins (robusta and arabica coffees) showed the absence of mepiquat (<0.005 mg kg(-1)). Preliminary studies indicate that mepiquat is not formed during processing (thermal treatment) in most of the cereal-based foods such as pizza and ready-to-eat cereals, but was detected in barley after roasting (0.64 mg kg(-1)). Mepiquat can therefore be considered a process-induced compound formed from natural constituents during the roasting process. Even considering a high intake of seven cups per day of soluble coffee containing 1.4 mg kg(-1) mepiquat in the coffee powder (the highest amount measured in this study), the resulting intake would exhaust less than 0.2% of the ADI of mepiquat.

Topics: Coffee; Food Analysis; Hordeum; Hot Temperature; Molecular Sequence Annotation; Piperidines; Plant Growth Regulators

Cotton (Gossypium hirsutum) has indeterminate growth. The growth regulator mepiquat chloride (MC) is used worldwide to restrict vegetative growth and promote boll formation and yield. The effects of MC are modulated by complex interactions with growing conditions (nutrients, weather) and plant population density, and as a result the effects on plant form are not fully understood and are difficult to predict. The use of MC is thus hard to optimize.. To explore crop responses to plant density and MC, a functional-structural plant model (FSPM) for cotton (named CottonXL) was designed. The model was calibrated using 1 year's field data, and validated by using two additional years of detailed experimental data on the effects of MC and plant density in stands of pure cotton and in intercrops of cotton with wheat. CottonXL simulates development of leaf and fruits (square, flower and boll), plant height and branching. Crop development is driven by thermal time, population density, MC application, and topping of the main stem and branches.. Validation of the model showed good correspondence between simulated and observed values for leaf area index with an overall root-mean-square error of 0·50 m(2) m(-2), and with an overall prediction error of less than 10% for number of bolls, plant height, number of fruit branches and number of phytomers. Canopy structure became more compact with the decrease of leaf area index and internode length due to the application of MC. Moreover, MC did not have a substantial effect on boll density but increased lint yield at higher densities.. The model satisfactorily represents the effects of agronomic measures on cotton plant structure. It can be used to identify optimal agronomic management of cotton to achieve optimal plant structure for maximum yield under varying environmental conditions.

Topics: Computer Simulation; Demography; Flowers; Fruit; Gossypium; Models, Biological; Piperidines; Plant Leaves; Plant Stems

The use of gibberellic acid (GA3) and N, N-dimethyl piperidinium chloride (DPC) in combination with prometryn would likely increase the control of black nightshade in cotton fields. Experiments were designed to investigate the physiological and biochemical responses of black nightshade at the three- to four-leaf stage to prometryn applied at different rates, either alone or in combination with GA3 or DPC, in a greenhouse environment. These studies demonstrated that prometryn applied in combination with DPC at low rates (7.2 g ai ha(-1)) led to increased fresh weight and visible injury of black nightshade compared with prometryn applied alone or in combination with GA3; however, at rates of 36, 180, and 900 g ai ha(-1), prometryn in combination with DPC caused the least visible injury among all treatments and prometryn in combination with GA3 caused the greatest visible injury. These results suggest that black nightshade suffered more severe damage when prometryn was applied in combination with GA3, which is supported by the reduced soluble protein content, lower antioxidant enzyme activities, and higher malondialdehyde (MDA) content in the plants treated with prometryn plus GA3. These results indicate that the application of GA3 in combination with prometryn to black nightshade may have the potential to lower the levels of prometryn tolerance in these plants.

Topics: Dose-Response Relationship, Drug; Gibberellins; Piperidines; Plant Growth Regulators; Plant Proteins; Prometryne; Solanum nigrum

The growth regulator mepiquat chloride (MC) is globally used in cotton (Gossypium hirsutum L.) canopy manipulation to avoid excess growth and yield loss. However, little information is available as to whether the modification of plant architecture by MC is related to alterations in gibberellic acid (GA) metabolism and signaling. Here, the role of GA metabolism and signaling was investigated in cotton seedlings treated with MC. The MC significantly decreased endogenous GA3 and GA4 levels in the elongating internode, which inhibited cell elongation by downregulating GhEXP and GhXTH2, and then reducing plant height. Biosynthetic and metabolic genes of GA were markedly suppressed within 2-10d of MC treatment, which also downregulated the expression of DELLA-like genes. A remarkable feedback regulation was observed at the early stage of MC treatment when GA biosynthetic and metabolic genes expression was evidently upregulated. Mepiquat chloride action was controlled by temporal translocation and spatial accumulation which regulated GA biosynthesis and signal expression for maintaining GA homeostasis. The results suggested that MC application could reduce endogenous GA levels in cotton through controlled GA biosynthetic and metabolic genes expression, which might inhibit cell elongation, thereby shortening the internode and reducing plant height.

Topics: Down-Regulation; Gene Expression; Gene Expression Regulation, Plant; Genes, Plant; Gibberellins; Gossypium; Piperidines; Plant Cells; Plant Growth Regulators; Plant Proteins; Plant Stems; Seedlings; Signal Transduction

This study is the first to examine the role of choline and glycine betaine, naturally present in some foods, in particular in cereal grains, to generate N,N-dimethylpiperidinium (mepiquat) under Maillard conditions via transmethylation reactions involving the nucleophile piperidine. The formation of mepiquat and its intermediates piperidine - formed by cyclisation of free lysine in the presence of reducing sugars - and N-methylpiperidine were monitored over time (240°C, up to 180 min) using high-resolution mass spectrometry in a model system comprised of a ternary mixture of lysine/fructose/alkylating agent (choline or betaine). The reaction yield was compared with data recently determined for trigonelline, a known methylation agent present naturally in coffee beans. The role of choline and glycine betaine in nucleophilic displacement reactions was further supported by experiments carried out with stable isotope-labelled precursors (¹³C- and deuterium-labelled). The results unequivocally demonstrated that the piperidine ring of mepiquat originates from the carbon chain of lysine, and that either choline or glycine betaine furnishes the N-methyl groups. The kinetics of formation of the corresponding demethylated products of both choline and glycine betaine, N,N-demethyl-2-aminoethanol and N,N-dimethylglycine, respectively, were also determined using high-resolution mass spectrometry.

Topics: Alkaloids; Betaine; Carbon Radioisotopes; Choline; Chromatography, High Pressure Liquid; Deuterium; Hot Temperature; Kinetics; Lysine; Maillard Reaction; Methylation; Models, Chemical; Molecular Structure; Molecular Weight; Piperidines; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry

A modified LC-MS method for the analysis of mepiquat residue in wheat, potato, and soil was developed and validated. A hydrophilic interaction liquid chromatographic column has been successfully used to retain and separate the mepiquat. Mepiquat residue dynamics and final residues in supervised field trials at Good Agricultural Practice (GAP) conditions in wheat, potato, and soil were studied. The limits of quantification for mepiquat in all samples were all 0.007 mg kg(-1), which were lower than their maximum residue limits. At fortification levels of 0.04, 0.2, and 2 mg kg(-1) in all samples, recoveries ranged from 77.5 to 116.4% with relative standard deviations of 0.4-7.9% (n = 5). The dissipation half-lives (T 1/2) of mepiquat in soil (wheat), wheat plants, soil (potato), and potato plants were 4.5-6.3, 3.0-5.6, 2.2-4.6, and 2.4-3.2 days, respectively. The final residues of mepiquat were below 0.153 mg kg(-1) in soil (wheat), 0.052-1.900 mg kg(-1) in wheat, below 0.072 mg kg(-1) in soil (potato), and below 1.173 mg kg(-1) in potato at harvest time. Moreover, pesticide risk assessment for all the detected residues was conducted. A maximum 0.0012% of acceptable daily intake (150 mg kg(-1)) for national estimated daily intake indicated low dietary risk of these products.

Topics: Environmental Monitoring; Half-Life; Pesticide Residues; Piperidines; Plant Growth Regulators; Soil; Soil Pollutants; Solanum tuberosum; Triticum

¹H Nuclear Magnetic Resonance spectroscopy has been used to profile urinary metabolites in male Fischer F344 rats in order to assess the metabolic changes induced by oral exposure to two benzimidazole fungicides (carbendazim and thiabendazole) and two bipyridyllium herbicides (chlormequat and mepiquat). Exposure levels were selected to be lower than those expected to cause overt signs of toxicity. We then compared the sensitivity of the metabolomics approach to more traditional methods of toxicity assessment such as the measurement of growth and organ weights. Separate, acute exposure experiments were conducted for each pesticide to identify potential metabolic markers of exposure across four doses (and a control). Growth, organ weights and feeding/drinking rates were not significantly affected by any compounds at any dose levels tested. In contrast, metabolic responses were detected within 8 and 24h for chlormequat and mepiquat, and after 24h for carbendazim and thiabendazole. These results demonstrate the potential for the use of metabolomics in food toxicity testing.

Topics: Animals; Benzimidazoles; Biomarkers; Carbamates; Chlormequat; Dose-Response Relationship, Drug; Food Contamination; Fungicides, Industrial; Herbicides; Magnetic Resonance Spectroscopy; Male; Metabolomics; Pesticide Residues; Piperidines; Principal Component Analysis; Random Allocation; Rats; Rats, Inbred F344; Thiabendazole; Toxicology; United Kingdom

Because the farmer is typically excluded from the experimental research setting, experimental research may face challenges in evaluating pest management tactics whose costs and benefits hinge on farmer decision-making. In these cases an ecoinformatics approach, in which observational data collected from the commercial farming setting are "mined" to quantify both biological variables and farmer behavior, can complement experimentation as a useful research tool. Here I analyze such an observational data set to characterize associations between early- (June) and mid-season (July) Lygus hesperus Knight populations and farmer decisions to apply plant growth regulators and defoliants. Previous experimental work suggested the hypothesis that Lygus herbivory, by inducing abscission of young flower buds, might generate increased use of plant growth regulators and defoliants. Cotton's ability to compensate for loss of flower buds may, however, increase as plants grow. On upland cotton, June Lygus populations were associated with increased use of plant growth regulators, as expected, but this relationship was not observed for July Lygus populations. June Lygus populations were not associated with the use of defoliants, whereas, surprisingly, July Lygus populations were associated with decreases in defoliant use. In contrast to these positive and negative associations observed on upland cotton, on Pima cotton Lygus populations exhibited no associations with use of either plant growth regulators or defoliants. These results suggest that cotton responses to Lygus herbivory, as demonstrated in previously published experimental studies, can translate into economically meaningful changes in farmer decisions to apply agricultural chemicals.

Topics: Agriculture; Animals; California; Cost-Benefit Analysis; Decision Making; Defoliants, Chemical; Gossypium; Herbivory; Heteroptera; Nymph; Piperidines; Plant Growth Regulators; Population Density

To investigate the effect of plant growth regulators on the growth and quality of Angelica dahurica var. formosana.. Five plant growth regulators: chlormequat chloride (CCC), Mepiquat chloride (PIX), Gibberellic acid (GA3), Paclobutrazol (PP333) and Maleic Hydrazide (MH) were sprayed in rosette stage, the effects of these plant growth regulators (PGRs) on the growth, yield and quality of A. dahurica var. formosanaw were observed. The biological traits were first measured and then imperatorin and isoimperatorin contents in roots were determined by HPLC.. Low concentration GA3 increased the yield while not influenced the premature bolting rate and the coumarin content.. Spraying of GA3 (30 mg x L(-1)) could guarantee the growth and development of A. dahurica var. formosana to have a higher yield and maintain the active ingredients content in the root as well.

Topics: Angelica; Chlormequat; Gibberellins; Maleic Hydrazide; Piperidines; Plant Growth Regulators; Triazoles

A simple, accurate and highly sensitive analytical method was developed in this study for determining the residues and dissipation dynamics of mepiquat chloride in soil and cotton crops (including plant and seed). The samples in this method were directly extracted with methanol-ammonium acetate solution and followed by analysis of high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The intra-day and inter-day recoveries of mepiquat chloride were in the range of 76.58-98.87 percent and 73.48-104.7 percent with relative standard deviations (RSDs) of 0.89-5.04 percent and 3.84-10.7 percent, respectively. The limit of quantification (LOQ) was 0.05mgkg(-1) for soil and 0.1mgkg(-1) for cotton plant and seed. The half-life of mepiquat chloride in cotton plants and in soil was 2.51-3.85 days and 7.56-10.50 days, respectively. The final residues of mepiquat chloride in all cotton seeds were below the MRLs of EU (5mgkg(-1)), Japan and America (2mgkg(-1)) over 14 days after the last spraying, and were below 1mgkg(-1) (the MRLs set by Argentina and Australia) over 21 days after the last spraying at recommended dosage. The final residues in soil were below the LOD (0.01mgkg(-1)) over 21 days after the last spraying.

Topics: Chromatography, High Pressure Liquid; Gossypium; Half-Life; Limit of Detection; Piperidines; Plant Growth Regulators; Soil; Soil Pollutants; Tandem Mass Spectrometry

To study the effect of plant growth regulator mepiquat chloride (DPC) on the growing development of plant and the content of active compounds in Scutellaria baicalensis.. After spraying DPC during the seedling period, the length of taproot, fresh weight of root, diameter of taproot and the length of stem were measured. The contents of baicalin, baicalein and wogonin were determined by HPLC, respectively. Total flavonoids and scavenging DPPH were determined with ultraviolet spectrophotometry.. After spraying DPC, fresh weight of S. baicalensis root was significant increased, and root diameter was also increased. The contents of baicalin and total flavonoids were significantly increased and baicalein and wogonin were decreased remarkably. Compared with controls, scavenging activity of ethanol extracts on DPPH free radical was no significant changed after spraying DPC.. Plant growth regulator DPC could regulate the growth on the ground and underground effectively, and could enhance the content of flavonoids compounds of S. baicalensis.

Topics: Chromatography, High Pressure Liquid; Piperidines; Plant Growth Regulators; Scutellaria baicalensis

Ion-pair reagent was used as mobile phase for the simultaneous separation of chlormequat chloride and mepiquat chloride in plants. The rapid separation was performed on a Dionex IonPac NG1 guard column and a Dionex IonPac NS1 analytical column using 1.0 mL/min of the eluent mixture of 1.00 mmol/L nonafluoropentanoic acid (as ion-pair reagent) and 7% acetonitrile, and the detection was achieved by a suppressed conductivity detector. The method provided good resolution of the analyte peaks without any interference. The detection limits of chlormequat chloride and mepiquat chloride were 0.154 6 mg/L and 0.171 4 mg/L, respectively. The linear calibration curves were obtained in the range of 1 - 100 mg/L. The mean recoveries in the ranges of 96.06% - 104.6% for chlormequat chloride and 98.53% - 103.7% for mepiquat chloride were obtained in real samples. The method requires only simple sample preparation and the technique is suitable for routine quality control analysis.

Topics: Chlormequat; Chromatography, Ion Exchange; Drug Residues; Piperidines; Plant Growth Regulators; Plants

A liquid chromatography-mass spectrometry (LC-MS) method for the identification and quantification of chlormequat (CQ) and mepiquat (MQ) in source waters with high sensitivity and specificity was established using WCX cartridges (150 mg/6 mL) for pre-concentration of the samples and using the CAPCELL PAK CR 1:4 (2.0 mm×150 mm 5 μm, SCX:C18=1:4) column containing strong cationic exchange resins and C18 for separation. The method could solve the problem for pre-concentrating ionic compounds from water samples and avoid the MS instrument fouling problem accompanied with the use of ion-pair reagents. After the optimization of analytical conditions, quantification was achieved in the positive electrospray ionization mode using selected ion monitoring. The samples were analyzed with multi-channel mode with quantification performed at 30 V cone voltage to ascertain the sensitivity and qualitative analysis performed at 60 V cone voltage simultaneously. The method detection limits (MDLs) of CQ and MQ in source water were determined to be 14 and 22 ng L(-1). Finally, the method was used to quantify CQ and MQ in several source waters, which gave a level ranging from below the quantitation limit to 28 ng L(-1).

Topics: Chlormequat; Chromatography, High Pressure Liquid; Fresh Water; Piperidines; Reproducibility of Results; Solid Phase Extraction; Spectrometry, Mass, Electrospray Ionization; Water Pollutants, Chemical

In this work a LC-MS/MS method for the determination of two quaternary ammonium growth regulators (chlormequat and mepiquat) in food is reported. The separation was based on hydrophilic interaction liquid chromatography (HILIC) without the use of ion-pair reagents. A gradient elution of acetonitrile and formic acid/ammonium formate buffer from 60 to 40% acetonitrile was enough to achieve a resolution >1.5 in less than 4.0min. The HILIC system was coupled to a triple quadrupole mass spectrometer equipped with a heated electrospray probe (H-ESI) providing sub-pg LODs in SRM mode. A straightforward sample treatment (SPE C18 clean-up) was enough to provide MLODs at low ppb levels when analysing a range of food samples that covered different kinds of matrices such as fresh fruit, vegetables, fruit juices, baby food, bread, coffee and beer. Chlormequat was found in seven samples (0.8-126ng/g) but mepiquat was only detected in bread and coffee samples (0.9-166ng/g).

Topics: Chlormequat; Chromatography, Liquid; Food Analysis; Piperidines; Tandem Mass Spectrometry

A simple, fast and precise High Performance Liquid Chromatographic method with diode array detector was developed and single laboratory validated for the determination of mepiquat chloride in soluble concentrate pesticide formulations. From the results obtained, the repeatability of the method expressed as relative standard deviation (%RSD) was found to be 0.3%, and the limit of detection was 0.02 microg/mL. The accuracy of the whole procedure estimated by the comparison of the results obtained with the reference values, and was found to be acceptable as t(cal) < t(crit). The precision of the method also considered acceptable as the experimental repeatability relative standard deviation (RSD(r)) was lower than the interlaboratory relative standard deviation (RSD(R)), calculated by the Horwitz equation.

Topics: Chromatography, High Pressure Liquid; Pesticides; Piperidines; Reproducibility of Results; Spectrophotometry, Ultraviolet

To evaluate the effects of a worldwide used plant growth regulator mepiquat chloride on the nutrition value and safety of seeds of transgenic Bt cotton, inorganic element components and contents in seeds of Bt cotton (Gossypium hirsutum cv. Guoxin 6) under field condition were determined using ICP-MS. In Bt cotton seeds, 54 kinds of inorganic elements were identified by ICP-MS, and 5 kinds of major elements, K, P, Mg, Ca and Na, were in range from 138.3 to 13,835.1 microg x g(-1). The contents of 14 kinds of microelements were determined as in descending order of Si, B, Mn, Sr, Zn, Ni, Cu, Mo, Fe, Co, Se, V, I and Sn, in the range from 14.2 ng x g(-1) to 81.7 microg x g(-1). Five kinds of heavy metals were detected with the contents from 0.14 to 55.3 ng x g(-1), and their order from high to low is Pb, Cd, Cr, As and Hg. Other 30 kinds of elements were also detected in Bt cotton seeds by ICP-MS, including Rb, Be, La, Ce, Pr, Nd, Sm, Gd, Ge, Rh, Ag, Sb, W, U and Y. Foliar application of mepiquat chloride significantly reduced the contents of Ca, Fe, Si, Mn, Co, Ni, Cu and I, and remarkably decreased heavy metals Pb, Cd and Cr in the cotton seeds, by 68%, 67% and 54% respectively. While mepiquat chloride did not change the contents of most major and micro elements, it heightened 8 kinds, but lowered 7 kinds of the other 30 trace elements. This research indicated that mepiquat chloride application strengthened the security regarding the cotton seed as the material of cooking oil.

Topics: Animals; Gossypium; Immunity, Innate; Insecta; Mass Spectrometry; Piperidines; Plant Diseases; Plant Growth Regulators; Plants, Genetically Modified; Seeds; Trace Elements

An intercomparison study of the determinations of glyphosate, chlormequat and mepiquat residues in cereals was performed. Four samples comprising one blank, two incurred and one spiked sample were sent to six participating laboratories. For glyphosate, two laboratories reported considerably lower results than the other four. One of the two laboratories with low results also reported low recoveries. The results of a sample spiked with 0.80 mg kg-1 glyphosate and an incurred sample, ranged from 0.23-0.87 mg kg-1 and 0.11-0.25 mg kg-1 respectively. The strong correlation between the two samples (r2 = 0.95) indicates a systematic between-laboratory variation. Several different principles were used for the analysis of glyphosate using different clean-up techniques and GC/MS, HPLC-fluorescence or LC/MS for detection. The results of the chlormequat residues showed more consistency. All but one laboratory obtained comparable results. However the correlation between the results for the sample spiked with 0.38 mg kg-1 (range: 0.26-0.65 mg kg-1) and the incurred samples (range: 0.19-0.45 and 0.15-0.23 mg kg-1, respectively) again showed a strong correlation (r2 = 0.99 and 0.88) indicating a systematic component. For mepiquat, results above the limit of quantification were only reported for the spiked sample. The results ranged from 0.29-0.92 mg kg-1 (spiked concentration = 0.38 mg kg-1). Three laboratories had results that deviated less than 25% from the fortified concentration. Two laboratories reported results 38% and 141% above the fortified concentration, respectively.

Topics: Chlormequat; Chromatography, Liquid; Edible Grain; Food Contamination; Glycine; Glyphosate; Herbicides; Humans; Mass Spectrometry; Pesticide Residues; Piperidines; Plant Growth Regulators

A simple and rapid method was developed for the analysis of mepiquat chloride in grape, wine and juice by high-performance liquid chromatography with electrospray tandem mass spectrometry (LC/MS/MS). Mepiquat chloride was extracted with water-methanol (1:1). Extracted solution was adjusted to pH 10 with ammonia solution. A part of the extracted solution was cleaned up on a styrenedivinylbenzene (SDVB) cartridge for LC/MS/MS. The LC separation was performed on a C18 column (50 mm x 2 mm i.d.) using 0.1% IPCC-MS7-methanol (60:40) as the mobile phase at a flow rate of 0.2 mL/min. The mass spectral acquisition was done in the positive ion mode by applying selected reaction monitoring (SRM). The recoveries of mepiquat chloride from fresh grape, wine and juice fortified at 5 microg/kg and 50 microg/kg were 84.5-96.1%. The lower limit of quantification was 1 microg/kg. Fourteen fresh grape samples, 14 wines (white), 36 wines (red) and 11 juice samples were analyzed by this method. Mepiquat chloride was detected in 5 fresh grape samples, 3 wines (white) and 1 wine (red) at the level of 12.8-199 microg/kg, 5.7-47.7 microg/kg and 24.1 microg/kg, respectively.

Topics: Beverages; Chromatography, High Pressure Liquid; Drug Residues; Food Analysis; Food Contamination; Piperidines; Plant Growth Regulators; Spectrometry, Mass, Electrospray Ionization; Vitis; Wine

A sensitive and selective method is presented for the simultaneous analysis of the pesticides chlormequat and mepiquat at trace levels in tomato, pear, and wheat flour. The method entails direct injection of the food extract onto an on-line solid-phase extraction (SPE) instrument (Prospekt) using a strong cation-exchange resin. Analyte separation and detection is done by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS). Surrogate standards (d9-chlormequat, d6-mepiquat) are employed to compensate for recovery losses and potential MS-MS signal suppression. The method achieves a limit of quantification for both cationic analytes at or below 5 microg/kg, and good intra- and inter-assay precision with mean variability values <7% over a concentration range up to 195 microg/kg. This study also addresses potential analyte carry-over in an SPE on-line system, as well as the robustness of the procedure and its applicability in routine quality control operations.

Topics: Calibration; Chlormequat; Chromatography, Liquid; Fruit; Piperidines; Plant Growth Regulators; Reproducibility of Results; Sensitivity and Specificity; Spectrometry, Mass, Electrospray Ionization; Triticum

Gas-phase cluster formation between the quaternary ammonium pesticides paraquat, diquat, difenzoquat, chlormequat and mepiquat, and chloride and acetate anions present in a liquid chromatography (LC) mobile phase, has been studied using electrospray mass spectrometry. The clusters of paraquat, mepiquat and chlormequat were revealed over the entire m/z range of the mass spectrometer, and their formation is dependent on the concentrations of both the cationic and the anionic species. Mepiquat and chlormequat form clusters of the type [2M(q)(+) + A(-)](+), where M(q)(+) is the quaternary ammonium cation and A(-) is the anion. Paraquat forms a cluster species with ammonia and also an ion-pair complex with chloride anions. Diquat and difenzoquat did not form observable ion-pair complexes or clusters with any of the anions studied. Competitive binding of acetate and chloride anions reflects the higher charge density of chloride, which forms the dominant clusters with mepiquat and chlormequat. The formation of cluster species has implications for the quantification of quaternary ammonium pesticides and may have an influence on the linearity of calibrations.

Topics: Acetates; Cations; Chlorides; Chlormequat; Chromatography, Liquid; Diquat; Molecular Structure; Paraquat; Pesticides; Piperidines; Pyrazoles; Quaternary Ammonium Compounds; Spectrometry, Mass, Electrospray Ionization

An LC-MS/MS method for analysing glyphosate and aminomethylphosphonic acid (AMPA) in cereals was developed. The method is based on extraction with water and detection of the ions from the fragmentation m/z 170-->88 (glyphosate) and m/z 112-->30 (AMPA), using electrospray interface in the positive mode. Investigation from the harvests of 1998 and 1999 showed residues of glyphosate and/or its degradation product AMPA in more than half of the cereal samples produced in Denmark. The average concentration of glyphosate in 46 samples from the 1999 harvest was 0.11 mg/kg compared with 0.08 mg/kg for the 1998 harvest (n = 49). Thus, the figures were well below the maximum residue limit (MRL) and no violations were observed. The plant growth regulators chlormequat and/or mepiquat were investigated in cereals from the Danish harvest of 1999 where 83% of the samples contained chlormequat (n = 46) compared with 87% of the samples from the 1997 harvest (n = 52). The average concentration of chlormequat in 1999 was 0.32 mg/kg compared with 0.23 mg/kg in 1997. At 2.9 mg/kg, one sample of wheat bran was exceeding the MRL of 2 mg/kg for wheat. The intakes of the pesticides through the diet of cereals were estimated to comprise 0.04% of the acceptable daily intake (ADI) for glyphosate and 1% of the ADI for chlormequat for an adult Dane.

Topics: Chlormequat; Chromatography, High Pressure Liquid; Denmark; Edible Grain; Glycine; Glyphosate; Herbicides; Humans; Mass Spectrometry; Maximum Allowable Concentration; Piperidines; Plant Growth Regulators; Reproducibility of Results

Topics: Air Pollutants, Occupational; Photometry; Piperidines; Plant Growth Regulators