naphthoquinones and 1-2-naphthoquinone-4-sulfonate

This paper revises the derivatization approaches for the determination of biogenic amines in wines. Since most of these amines display poor spectroscopic features to be detected by UV absorption or emission (fluorescence) spectroscopy, derivatization is necessary to attain the desired sensitivity. Reagents such as o-phthaldialdehyde, fluorenylmethylchloroformate, dansyl-Cl and dabsyl-Cl have widely been used for analytical labeling through amino group. A comparison of features of off- and on-line pre- and post chromatographic/electrophoretic labeling is given using 1,2-naphthoquinone-4-sulfonate (NQS) as an example. The evaluation of the influence of the wine sample composition on the derivatization process indicates that pre-column labeling may undergo more severe matrix effects.

Topics: Biogenic Amines; Chromatography, Liquid; Electrophoresis, Capillary; Naphthoquinones; Wine

A sensitive and stable signal multiplied quinone-linked immunosorbent assay (Multi-QuLISA) was developed. In Multi-QuLISA, an oligomerized quinone linked to biotin, namely biotin-8mer-naphthoquinone (Bio8mer-NQ), is used as a signal-generating label. Bio8mer-NQ is formed from a dendrigraft poly-l-lysine generation 1 (DPLL G1), a controlled branched oligomer composed of eight lysine moieties with nine free amino groups as a backbone. One of the nine amino groups of DPLL G1 is attached to biotin moiety, while the other eight are attached to 1,2-naphthoquinone-4-sulfonate (NQS). Bio8mer-NQ labels a biotinylated detection antibody using avidin as a co-binder. Then, multi-quinones in Bio8mer-NQ undergo a redox cycle with dithiothreitol and luminol, generating strong chemiluminescence. Standard ELISA uses a label enzyme that suffers from vulnerability in different conditions and poor stability. Bio8mer-NQ showed better stability than the enzyme (biotin-HRP) under different drastic pH and temperature conditions, hydrolytic enzymes, etc. Furthermore, Bio8mer-NQ was used as both chemiluminescence and colorimetric label based on the redox cycle of quinone, and it had LODs of 1.5 and 6.5 nM, respectively. The method could detect biotinylated immunocomplex in an in-house designed immunoassay down to 0.2 nM, which is about 25 times more sensitive than biotin HRP. Eventually, Bio8mer-NQ was applied successfully in Multi-QuLISA for detecting β-casein with a sensitivity of 3.2 ng/mL, while the conventional ELISA had an LOD of 35 ng/mL. Overall, Bio8mer-NQ is a stable compound that could be used as an excellent replacement for the enzyme in immunoassay and can be used in both colorimetric and chemiluminescence assays with good sensitivity.

Topics: Biotin; Immunosorbents; Naphthoquinones; Polylysine

The development of in situ analytical devices has gained outstanding scientific interest. A solid sensing membrane composed of 1,2-naphthoquinone-4-sulfonate (NQS) derivatizing reagent embedded into a polymeric polydimethylsiloxane (PDMS) composite was proposed for in situ ammonium (NH

Topics: Colorimetry; Dimethylpolysiloxanes; Naphthoquinones; Polymers; Urea; Urease; Water

A colorimetric composite device is proposed to determine the widely used biocide N-(3-aminopropyl)-N-dodecyl-1,3-propanediamine (ADP).This sensing device is based on a film of 1,2-Naphthoquinone-4-sulfonate (NQS) embedded into polydimethylsiloxane-tetraethylortosilicate-SiO2 nanoparticles composite (PDMS-TEOS-SiO2NPs). Semiquantitative analysis can be performed by visual inspection. Digitalized image or diffuse reflectance (DR) measurements can be carried out for quantitative analysis. Satisfactory detection limit (0.018%, w/v) and relative standard deviations <12% were achieved. The proposed device has been applied for the determination of ADP in detergent industrial formulations with recovery values between 80% and 112%. The method has been successfully validated, showing its high potential to control and monitor this compound because the device is easy to prepare and use, robust, portable, stable over time and cost effective. This device allows a green, simple and rapid approach for the analysis of samples without pretreatment and does not require highly trained personnel. These advantages give the proposed kit good prospects for implementation in several industries.

Topics: Chemistry, Pharmaceutical; Colorimetry; Detergents; Dimethylpolysiloxanes; Disinfectants; Kinetics; Naphthoquinones; Propylamines; Silanes; Silicon Dioxide

Two rapid, simple and sensitive spectrophotometric methods for the quantitative analysis of moxifloxacin (MOX) in pharmaceutical formulations have been described. The first method (A) involves reaction of MOX with 1,2-naphthoquinone-4-sulphonate (NQS) in alkaline medium (pH 11.0) which results in an orange-coloured product exhibiting maximum absorption (lambda(max)) at 411 nm. The second method (B) is based on the oxidation of the MOX with a known excess of cerium (IV) sulfate and the residual oxidant is determined by treating with a fixed amount of methyl orange, and measuring the absorbance at 507 nm. The molar absorptivities for methods A and B were 4.9 x 10(3) and 6.5 x 10(4) L mol(-1) cm(-1), respectively. Under the optimized reaction conditions, Beer's law correlation of the absorbance with MOX concentration was obtained in the range of 2.5-20 and 0.5-30 microgmL(-1) for method A and B respectively. The intra-day precision expressed as relative standard deviation (RSD) was < 1.6% for both methods. The methods were validated in terms of accuracy and precision and were successfully applied to the determination of MOX in its pharmaceutical dosage form. The proposed methods are useful for routine analysis of MOX in quality control laboratories.

Topics: Aza Compounds; Chemistry, Pharmaceutical; Fluoroquinolones; Hydrogen-Ion Concentration; Molecular Structure; Moxifloxacin; Naphthoquinones; Quinolines; Spectrophotometry, Ultraviolet

Two new simple, sensitive, accurate, and precise spectrophotometric methods have been developed and validated for the determination of cefdinir (CFD) in bulk drug and in its pharmaceutical formulations. The first method was based on the reaction of CFD with 1, 2- napthaquinone-4- sulfonic acid sodium (NQS) in an alkaline medium (pH 11) to form an orange-coloured product that was measured at 490 nm. The second method depends on hydrolysis of CFD using 0.5 M NaOH at 100 °C and subsequent reaction of the formed sulfide ions with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) to form a yellow-coloured chromogen measured at 390 nm. Different variables affecting the reactions of CFD with both NQS and NBD-Cl (e.g. NaOH concentration, hydrolysis time, NQS or NBD-Cl concentration and diluting solvent) were studied and optimized. Under optimum conditions, good linear relationships with good correlation coefficients (0.9990-0.9999) were found in the range of 10-80 and 5.0-30 µg ml(-1) for NQS and NBD-Cl, respectively. The limits of assay detection and quantitation ranged from 1.097 and 0.280 and 3.656 and 0.934 µg ml(-1) for NQS and NBD-Cl, respectively. The accuracy and precision of the proposed methods were satisfactory. The proposed method is simple, rapid, precise and convenient and was successfully applied for analysis of CFD in its pharmaceutical formulations and the recovery percentages ranged from 99.25 to 100.20%.

Topics: 4-Chloro-7-nitrobenzofurazan; Anti-Bacterial Agents; Cefdinir; Cephalosporins; Chemistry, Pharmaceutical; Hydrogen-Ion Concentration; Hydrolysis; Kinetics; Limit of Detection; Linear Models; Naphthoquinones; Reproducibility of Results; Sodium Hydroxide; Solvents; Spectrophotometry, Ultraviolet; Temperature

A simple, sensitive, and selective spectrophotometric method has been developed for the determination of gabapentin (GBP) in capsules. The method is based on the reaction of GBP and sodium 1,2-naphthoquinone-4-sulfonate (NQS) in the presence of Clark and Lubs buffer of pH 11 to form an orange-coloured product which was measured at 495 nm. The parameters that affect the reaction were carefully optimized and under the optimized conditions, linear relationship was obtained in the concentration range of 7.5-75 µg ml(-1) GBP. The molar absorptivity, limits of detection (LOD) and quantification (LOQ) and Sandell sensitivity are also reported. The proposed method was successfully applied to the determination of GBP in capsules with good accuracy and precision and without detectable interference from common excipients. The reliability of the proposed method was further established by parallel determination by the reference method and also by recovery studies. The reaction mechanism is proposed and discussed.

Topics: Amines; Anticonvulsants; Buffers; Capsules; Cyclohexanecarboxylic Acids; Gabapentin; gamma-Aminobutyric Acid; Hydrogen-Ion Concentration; Naphthoquinones; Pharmaceutical Preparations; Reproducibility of Results; Sensitivity and Specificity; Spectrophotometry

Boron determination by a charge transfer spectrophotometric method is described. Accompanied the reaction, a charge transfer complex can be formed by lysine with sodium 1, 2-naphthoquinone-4-sulfonate and boron in alkaline solution (pH 12.00). Subsequently, a new reaction mechanism has been proposed and discussed. The absorbance at the maximal absorption wavelength is 574 nm and boron concentration agrees well with Beer's law in a range of 2.16-43.24 μg mL(-1). The linear regression equation is A=-0.01867+0.01326C (μg mL(-1)), with a linearly correlation coefficient of 0.9935. The relative standard deviation (R.S.D.) of eleven parallel determinations is 2.1% with a detection limit (3σ/k) of 2.00 μg mL(-1). The recovery ranges from 96.4% to 104.5% with the satisfactory results. This method has been successfully applied to determine boron in pharmaceutical samples directly.

Topics: Boron; Calibration; Hydrogen-Ion Concentration; Limit of Detection; Lysine; Naphthoquinones; Solutions; Spectrophotometry; Temperature

Spectrophotometric study was carried out, for the first time, to investigate the reaction between the antidepressant fluvoxamine (FXM) and 1,2-naphthoquinone-4-sulphonate (NQS) reagent. In alkaline medium (pH 9), an orange-colored product exhibiting maximum absorption peak (lambda(max)) at 470nm was produced. The kinetics of the reaction was investigated and its activation energy was found to be 2.65kcalmol(-1). Because of this low activation energy, the reaction proceeded easily. The stoichiometry of the reaction was determined and the reaction mechanism was postulated. This color-developing reaction was successfully employed in the development of simple and rapid spectrophotometric method for determination of FXM in its pharmaceutical dosage forms. Under the optimized reaction conditions, Beer's law correlating the absorbance (A) with FXM concentration (C) was obeyed in the range of 0.6-8microgml(-1). The regression equation for the calibration data was A=0.0086+0.1348C, with good correlation coefficient (0.9996). The molar absorptivity (epsilon) was 5.9x10(4)lmol(-1)cm(-1). The limits of detection and quantification were 0.2 and 0.6microgml(-1), respectively. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 2%. The proposed method was successfully applied to the determination of FXM in its pharmaceutical tablets with good accuracy and precisions; the label claim percentage was 100.47+/-0.96%. The results obtained by the proposed method were comparable with those obtained by the official method. The proposed method is superior to all the previously reported spectrophotometric methods for determination of FXM in terms of its simplicity and sensitivity. The method is practical and valuable for its routine application in quality control laboratories for analysis of FXM.

Topics: Antidepressive Agents, Second-Generation; Dosage Forms; Fluvoxamine; Molecular Structure; Naphthoquinones; Reproducibility of Results; Spectrophotometry

A new HPLC method for determining biogenic amines in wines is developed. This method is based on pre-column amine derivatization, further separation of derivatives and on-line hyphenation of HPLC to atmospheric pressure chemical ionization mass spectrometry (APCI-MS). Biogenic amines have been derivatized with 1,2-naphthoquinone-4-sulfonate at 65 degrees C and pH 9.2 for 5 min. The separation of derivatives has been accomplished in a C(18) analytical column using an elution gradient based on increasing the percentage of methanol. Derivatives have been ionized in positive mode and detected by selected ion monitoring. The operating conditions of the APCI-MS system (voltages, temperatures and gases) have been thoroughly optimized to obtain the maximum sensitivity for all analytes. In the selected conditions, APCI-MS spectra display little fragmentation and good signal-to-noise ratio. Depending on the amine characteristics, the main spectral peaks are due to mono- and di-derivative products. Figures of merit of the method have been established under the selected conditions using red wine samples. Recoveries ranging from 94% to 106% have been obtained which prove excellent accuracy of the method in the determination of histamine, putrescine, cadaverine, tryptamine, phenylethylamine, tyramine and serotonin in red wines. The proposed method has been applied to the analysis of commercial wines from different Spanish regions.

Topics: Analytic Sample Preparation Methods; Biogenic Amines; Chromatography, High Pressure Liquid; Histamine; Mass Spectrometry; Naphthoquinones; Phenethylamines; Putrescine; Spain; Tyramine; Wine

A novel and simple spectrophotometric method for the determination of Captopril with sodium 1,2-naphthoquinone-4-sulfonate is established in this paper. The detailed reaction mechanism is proposed and discussed. It is based on the fact that captopril can catalyze the reaction between sodium 1,2-naphthoquinone-4-sulfonate and hydroxyl ion to form 2-hydroxy-1,4-naphthoquinone in buffer solution of pH 13.00. Beer's law is obeyed in a range of 0.64-80 mugmL(-1) at the maximal absorption wavelength of 442 nm. The equation of linear regression is A=0.05815+0.00589C (mugmL(-1)), with a linear regression correlation coefficient of 0.9981. The detection limit is 0.3 mugmL(-1), R.S.D. is 0.77% and the recovery rate is in range of 96.0-103.8%. Furthermore, the method has been validated and successfully applied to the determination of captopril in pharmaceutical samples.

Topics: Angiotensin-Converting Enzyme Inhibitors; Captopril; Catalysis; Hydrogen-Ion Concentration; Hydroxides; Mass Spectrometry; Naphthoquinones; Spectrophotometry; Spectrophotometry, Infrared

A rapid, simple and sensitive method for the determination of lysine (Lys) using sodium 1,2-naphthoquinone-4-sulfonate (NQS) and tetradecyl benzyl dimethyl ammonium chloride (Zeph) is presented in this paper. The method is based on the russety product formed from Lys, NQS and Zeph in a buffer solution of pH 9.60, and the stoichiometric ratio of the product is 1:2:2. Beer's law is obeyed in a range of 0.09-18 microg ml(-1) of Lys at the maximum absorption of 474 nm (epsilon(474) is 8.1 x 10(5)l mol(-1)cm(-1)). The equation of linear regression is A=0.40427+0.06112C, with a linearly correlation coefficient of 0.9972. The limit of detection is 0.07 microg ml(-1), R.S.D. 0.8%, and average recovery rate in a range of 98.9-100.1%. This paper further optimizes the determination of Lys compared with the previous methods, and the reaction mechanism is studied intensively. The proposed method has been successfully applied to the determination of Lys in pharmaceutical and biological samples. The common components as nutritional additives in pharmaceuticals and other compounds in biological samples nearly do not interfere with the proposed method.

Topics: Benzalkonium Compounds; Body Fluids; Buffers; Calibration; Colorimetry; Humans; Hydrogen-Ion Concentration; Lysine; Naphthoquinones; Pharmaceutical Preparations; Solutions; Solvents; Spectrum Analysis

A new method has been established for the determination of aminomethylbenzoic acid using sodium 1,2-naphthoquinone-4-sulfonate as the chemical derivative chromogenic reagent. This method is based on the formation of a pink compound from the reaction of aminomethylbenzoic acid and sodium 1,2-naphthoquinone-4-sulfonate. The nucleophilic substitution reaction proceeds quantitatively in pH 12.0 buffer solution. The stoichiometric ratio of the reaction, maximum absorption wavelength and the value of epsilon(430) were 1:1, 430 nm, and 2.87 x 10(3)L mol(-1)cm(-1), respectively. Beer's law was obeyed in the range of 0.80-80 mg/L of aminomethylbenzoic acid. The data have been filled to a linear regression equation A=0.03183+0.01658C (mg/L), with a correlation coefficient of 0.9996. The detection limit is 0.11 mg/L, R.S.D. is 0.54%, and average recovery is over 99.6%. This paper further improves the determination of aminomethylbenzoic acid compared to the previous methods. The kinetic property and reaction mechanism have also been discussed. This proposed method has been successfully applied to the determination of aminomethylbenzoic acid in injection of aminomethylbenzoic acid with satisfactory results.

Topics: 4-Aminobenzoic Acid; Calibration; Chromogenic Compounds; Humans; Hydrogen-Ion Concentration; Kinetics; Naphthoquinones; para-Aminobenzoates; Reproducibility of Results; Solutions; Solvents; Surface-Active Agents; Temperature; Time Factors

A spectrophotometric method for simultaneous analysis of glycine and lysine is proposed by application of neural networks on the spectral kinetic data. The method is based on the reaction of glycine and lysine with 1,2-naphthoquinone-4-sulfonate (NQS) in slightly basic medium. On the basis of the difference in the rate between the two reactions, these two amino acids can be determined simultaneously in binary mixtures. Feed-forward neural networks have been trained to quantify considered amino acids in mixtures under optimum conditions. In this way, a one-layer network was trained. Sigmoidal and linear transfer functions were used in the hidden and output layers, respectively. Linear calibration graphs were obtained in the concentration range of 1 to 25microgml(-1) for glycine and 1 to 19microgml(-1) for lysine. The analytical performance of this method was characterized by the relative standard error. The proposed method was applied to the determination of considered amino acids in synthetic samples.

Topics: Algorithms; Glycine; Kinetics; Lysine; Multivariate Analysis; Naphthoquinones; Neural Networks, Computer; Principal Component Analysis; Regression Analysis; Signal Processing, Computer-Assisted; Spectrophotometry, Ultraviolet

A new method has been established for the determination of dopamine hydrochloride (DPH) using sodium 1,2-naphthoquinone-4-sulfonate (NQS) and tetradecyl benzyl dimethyl ammonium chloride (Zeph). This method is based on the formation of a pink compound from the reaction of DPH, sodium 1,2-naphthoquinone-4-sulfonate and Zeph. The condensation reaction proceeds quantitatively in pH 9.40 buffer solution. The maximum absorption wavelength and the value of epsilon491 were 491 nm, and 7.51x10(3) l mol(-1) cm(-1), respectively, when the stoichiometric ratio of the reaction was 1:1:1. Beer's law was obeyed in the range of 0.16-40 mg l(-1) of DPH. The data have been filled to a linear regression equation A=0.5781+0.0254 C (mg l(-1)), with a correlation coefficient of 0.9993. The detection limit is 0.12 mg l(-1), R.S.D. is 0.64% (40 mg l(-1), n=11), and average recovery is over 99.7%. This paper further improves the determination of DPH compared to the previous methods. The kinetic property and reaction mechanism have also been discussed. This proposed method has been successfully applied to the determination of DPH in injection and biological samples with satisfactory results.

Topics: Benzalkonium Compounds; Chromogenic Compounds; Dopamine; Hydrogen-Ion Concentration; Indicators and Reagents; Naphthoquinones; Spectrophotometry

A sensitive CE method for determining biogenic amines in wines based on in-capillary derivatization with 1,2-naphthoquinone-4-sulfonate is presented. In this method, reagent and buffer solutions are introduced hydrodynamically into the capillary whereas the sample is injected electrokinetically, thus, allowing a selective preconcentration of the analytes by field-amplified sample stacking. Amines are labeled inside the capillary using a zone-passing derivatization approach in mixed tandem mode. The most relevant variables influencing on the derivatization and separation as well as significant interactions have been evaluated using experimental design. Multi-criteria decision making is utilized for the simultaneous optimization of interacting variables through overall desirability response surfaces. The validation of the method has proven an excellent separation performance and accuracy for the determination of biogenic amines such as histamine, tryptamine, phenylethylamine, tyramine, agmatine, ethanolamine, serotonin, cadaverine, and putrescine in red wines. Detection limits range from 0.02 mg/L for ethanolamine to 0.91 mg/L for serotonin. The RSDs for migration time and peak area are around 1.2 and 6.2%, respectively. Red wines from different Spanish regions have been analyzed using the proposed method.

Topics: Biogenic Amines; Buffers; Electrophoresis, Capillary; Naphthoquinones; Wine

A liquid chromatographic method with post-column derivatization for the determination of biogenic amines in wines is proposed. The method is based on the separation of amines by ion-pair chromatography using sodium heptanesulfonate (SHS) and on-line labeling of analytes with 1,2-naphthoquinone-4-sulfonate. The principal factors influencing the separation (acetonitrile and SHS concentration) have been considered for the optimization of the elution gradient through factorial design and multicriteria decision-making. Figures of merit have been established using red wine samples. Detection limits range from 0.2 to 3 mg L(-1), the peak area run-to-run repeatability from 1.6 to 4.6% and the retention time repeatability lower than 1.2%. Recoveries ranging from 92 and 108% prove the accuracy of the method for determining ethanolamine, ethylamine, histamine and tyramine in commercial red wines. The proposed method has been applied to the analysis of wines from different Spanish regions.

Topics: Biogenic Amines; Chromatography, Liquid; Naphthoquinones; Sensitivity and Specificity; Spain; Wine

Spectrophotometric determination of dapsone is described. The dapsone reacts with sodium 1,2-naphthoquinone-4-sulfonic in pH 6.98 buffer solution to form a salmon pink compound, and its maximum absorption wavelength is at 525 nm, epsilon525=3.68 x 10(4) l mol(-1) cm(-1). The absorbance of dapsone from 0.40 to 10 microg ml(-1) obeys Beer's law. The linear regression equation of the calibration graph is C=0.2334 A + 0.01288, with a linear regression correlation coefficient of 0.9998, the detection limit is 0.24 microg ml(-1), and recovery is from 99.2 to 102.4%. Effects of pH, surfactant, organic solvents, foreign ions, and standing time on the determination of dapsone have been examined. This method is simple and can be used for the determination of dapsone in injection solution of dapsone. The results obtained by this method agreed with those by the official method (dead-stop titration method [The Chinese Pharmacopoeia, Pharmacopoeia Commission, Ministry of Health, vol. 2, fifth ed., PRC Chemical Industry Press, Beijing, 2000, p.720]).

Topics: Antimalarials; Chromogenic Compounds; Dapsone; Drug Compounding; Drug Stability; Hot Temperature; Hydrogen-Ion Concentration; Indicators and Reagents; Ions; Leprostatic Agents; Naphthoquinones; Solvents; Spectrophotometry; Surface-Active Agents

Spectrophotometric determination of ampicillin sodium is described. The ampicillin sodium reacts with sodium 1,2-naphthoquinone-4-sulfonic in pH 9.00 buffer solution to form a salmon pink compound, and its maximum absorption wavelength is at 463 nm, epsilon463 = 1.14 x 10(4). The absorbance of ampicillin sodium from 2.0-80 microg ml(-1) obeys Beer's law. The linear regression equation of the calibration graph is C = 40.24A - 2.603, with a linear regression correlation coefficient is 0.9997, the detection limit is 1.5 microg ml(-1), recovery is from 97.23 to 104.5%. Effects of pH, surfactant, organic solvents, and foreign ions on the determination of ampicillin sodium have been examined. This method is rapid and simple, and can be used for the determination of ampicillin sodium in the injection solution of ampicillin sodium. The results obtained by this method agreed with those by the official method (HPLC).

Topics: Absorption; Ampicillin; Chromatography, High Pressure Liquid; Chromogenic Compounds; Hot Temperature; Hydrogen-Ion Concentration; Ions; Molecular Structure; Naphthoquinones; Reproducibility of Results; Sensitivity and Specificity; Sodium; Solvents; Spectrophotometry; Surface-Active Agents; Time Factors

A new method for dimethylamine determination in air is reported. The proposed assay is based on the employment of C18-packed solid phase extraction cartridges for sampling. The retained amine is then derivatized inside the cartridges with the reagent 1,2-naphthoquinone-4-sulfonate. By observing the coloured area of the cartridge, a semiquantitative estimation of the amine can be made. It was also possible to distinguish between primary and secondary amines by visual inspection. Quantitative tests entailed desorption from the cartridges of the derivatives formed, and measurement of the absorbance of the collected extracts. The selected conditions were applied to quantify dimethylamine up to 100 microg, the quantification and detection limits being 6.7 and 2 microg, respectively. Satisfactory linearity and precision were obtained. Possible interferences by ammonia, primary amines and diethylamine were tested. The applicability of the procedure was demonstrated by estimating the concentration of dimethylamine in generated and real air samples. The procedure was useful for short-term exposure limit and threshold limit value estimations.

Topics: Air; Dimethylamines; Naphthoquinones; Reproducibility of Results; Sensitivity and Specificity; Spectrophotometry; Volatilization

Spectrophotometric determination of procaine hydrochloride is described. The procaine hydrochloride reacts with 1,2-naphthoquinone-4-sulfonic acid in pH 3.60 buffer solution to form a salmon pink compound, and its maximum absorption wavelength is at 484 nm, epsilon(484)=5.22 x 10(3).The absorbance for procaine hydrochloride from 0.30 to 100 microg ml(-1) obeys Beer's law. The linear regression equation of the calibration graph is C=19.23A-0.03, with a linear regression correlative coefficient is 0.9996, the detection limit is 0.28 microg ml(-1); recovery is from 98.0 to 105.2%. Effects of pH, surfactant, organic solvent, foreign ions, and standing time on the determination of procaine hydrochloride have been examined. This method is rapid and simple, and can be used for the determination of procaine hydrochloride in injection solution of procaine hydrochloride. The results obtained by this method agreed with those by the official method (dead-stop titration).

Topics: Hydrogen-Ion Concentration; Indicators and Reagents; Naphthoquinones; Pharmaceutical Preparations; Procaine; Solvents; Spectrophotometry

This paper examines the potentiality of in-capillary derivatization for improving the sensitivity of the spectrophotometric detection of amino acids in capillary zone electrophoresis. 1,2-Naphthoquinone-4-sulfonate was selected as the labeling agent of amino acids. The underivatized sample and the reagent solution segments are injected by pressure into the capillary prior to applying the running voltage. The corresponding derivatization reaction occurs inside the capillary once the potential is applied, as it induces mixing of the sample with the reagent. Several introduction modes consisting of tandem or sandwich configuration have been evaluated. These techniques result in a straightforward and automated way of carrying out a derivatization. Furthermore, in-capillary procedures may become much more attractive than conventional pre-capillary derivatization in terms of sensitivity and reproducibility. The optimum operation mode found consists of a sandwich system where the sample is injected in between two reagent segments. The method was applied to the determination of amino acids in feed samples. Results show a good concordance with those given by a standard amino acid analyzer.

Topics: Amino Acids; Electrophoresis, Capillary; Indicators and Reagents; Naphthoquinones; Sensitivity and Specificity

The application of chemometric techniques to the resolution of overlapped peaks in capillary electrophoresis (CE) is described. When a physical separation can not be completely accomplished, chemometrics might still resolve the determination of the analytes mathematically. CE with diode array detection can provide a large amount of data consisting of spectra registered over time. In this study, the capillary electrophoretic separation of 1,2-naphthoquinone-4-sulfonate derivatives of amino acids is studied. Most of the common amino acid derivatives can be separated at 30 kV in a fused-silica capillary by using a 40 mM sodium tetraborate + isopropanol (3:1 v/v) solution as background electrolyte. However, peaks of certain derivatives (Phe, His, Leu and Ile) still overlap. A multivariate curve resolution method based on an alternating least squares optimization procedure is used for the resolution of the overlapped electrophoretic peaks. The method takes advantage of spectral and electrophoretic differences of analytes to recover their pure electrophoretic and spectral profiles. In addition, each analyte in the mixture can be quantified using the corresponding standards.

Topics: 2-Propanol; Amino Acids; Borates; Electrophoresis, Capillary; Least-Squares Analysis; Multivariate Analysis; Naphthoquinones

A liquid chromatographic method for the determination of aniline in cyclamate sweeteners based on a pre-column derivatization with 1,2-naphthoquinone-4-sulfonate (NQS) is proposed. Aniline traces were extracted from the cyclamate samples using dichloromethane. After solvent evaporation, the dry residue was derivatized with NQS at pH 9.5 and 85 degrees C for 1 min. The aniline derivative, which was extracted from the reacting mixture, was redissolved in the eluent solution and injected into the chromatographic system. The separation of aniline derivative from other amine impurities was carried out in a C18 column using a 2% acetic acid-methanol (40:60, v/v) mobile phase. Results from the analysis of aniline in the sweetener samples with the proposed method were compared with those from the standard method. A good concordance between the two methods was observed.

Topics: Aniline Compounds; Chromatography, High Pressure Liquid; Cyclamates; Indicators and Reagents; Methylene Chloride; Naphthoquinones; Sensitivity and Specificity

Topics: Cell Division; Cell Membrane Permeability; Ferricyanides; HeLa Cells; Humans; Naphthoquinones; Oxidants; Ruthenium Compounds; Transferrin; Tumor Cells, Cultured

A rapid, sensitive and simple spectrophotometric method is proposed for the determination of hydrolysis products of paracetamol (PRL) and phenacetin (PHN) with sodium 1,2-naphthoquinone-4-sulphonate and cetyltrimethyl ammonium bromide (CTA) in alkaline medium. The absorbances are measured at 570 and 500 nm and the molar absorptivities found to be 1.118 x 10(4) and 4.54 x 10(3) l mol-1 cm-1 for PRL and PHN, respectively. The coloured species conforms to Beer's law over the range 1-20 micrograms ml-1 for PRL and 2-24 micrograms ml-1 of PHN. The sensitivity is enhanced by the addition of CTA. The method is successfully employed for determination of PRL or PHN in various pharmaceutical preparations and laboratory made tablets and results have been statistically compared with those obtained by the official method.

Topics: Acetaminophen; Alkalies; Analgesics, Non-Narcotic; Drug Stability; Hydrolysis; Isoniazid; Naphthoquinones; Phenacetin; Spectrophotometry

Anionic dyes, notably acid fuchsine, strongly stain the nuclei and cytoplasm of neurons severely damaged by injury or disease. We provide detailed instructions for staining nervous tissue with toluidine blue and acid fuchsine for optimal demonstration of injured neurons. Degeneration was induced in the hippocampus of the mouse by systemic administration of kainic acid, and the resulting acidophilia was investigated using paraffin sections of the Carnoy- or Bouin-fixed brains. The affected cells were bright red with the toluidine blue-acid fuchsine sequence. Their nuclei were stainable also with alkaline Biebrich scarlet and with the 1,2-naphthoquinone-4-sulfonic acid-Ba(OH)2 method; all staining was blocked by benzil but was relatively refractory to deamination by HNO2. These properties indicated an arginine-rich protein. The nuclei were strongly acidophilic in the presence of a high concentration of DNA (strong Feulgen reaction), and acidophilia could not be induced in normal neuronal nuclei by chemical extraction of nucleic acids. The cytoplasmic acidophilia of degenerating hippocampal neurons was due to a protein rich in lysine (extinguished by alkalinity, easily prevented by deamination, and unaffected by benzil). Stainable RNA was absent from the perikarya of the affected cells, but normal neuronal cytoplasm did not become acidophilic after extraction of nucleic acids. We suggest that kainate-induced cell death is preceded by increased production of basic proteins, which become concentrated in the nucleus and perikaryon. Groups of small, darkly staining neurons were seen in the cerebral cortex in control and kainate-treated mice. These shrunken cells were purple with the toluidine blue-acid fuchsine stain, and were attributed to local injury incurred during removal of the unfixed brain.

Topics: Animals; Azo Compounds; Benzenesulfonates; Brain; Coloring Agents; Female; In Vitro Techniques; Indicators and Reagents; Kainic Acid; Mice; Naphthols; Naphthoquinones; Neurons; Staining and Labeling; Tolonium Chloride

Cefotaxime was derivatised with 1,2-naphthoquinone-4-sulphonate (NQS), extracted into solid-phase cartridges (C18) and detected using a UV-visible detection system. Optimum conditions for this new procedure were: hydrogencarbonate-carbonate buffer, pH 10.5, 5-min reaction time at 25 degrees C and an NQS concentration of 7.1x10(-3) mol l(-1). The accuracy and the precision of the liquid-solid procedure were tested. The procedure was used to measure cefotaxime in pharmaceutical and urine samples. The results obtained were contrasted with those reported for a HPLC method for urine samples. The generalized H-point standard additions method was used to measure cefotaxime in urine samples.

Topics: Adult; Cefotaxime; Cephalosporins; Chromatography, High Pressure Liquid; Humans; Indicators and Reagents; Naphthoquinones; Pharmaceutical Preparations; Sensitivity and Specificity; Spectrophotometry

Methods of biochemical and physicochemical analysis were applied for studying the role of Micrococcus luteus cell structure in gold accumulation. It was shown that membrane proteins were the main factors in this process. Moreover, different quinones played the main role in the redox transformation of gold.

Topics: Absorption; Bacterial Proteins; Biotransformation; Butanols; Cell Membrane; Gold Colloid; Membrane Proteins; Micrococcus luteus; Naphthoquinones; Oxygen; Spheroplasts

A liquid-solid procedure is proposed for sample clean-up and derivatization of amphetamine and methamphetamine in urine samples. The reagent was 1,2-naphthoquinone 4-sulphonate, and a commercial C18 packing cartridge was used. The samples derivatized at room temperature were chromatographed on a 5-microns Hypersil ODS (250 x 4 mm I.D.) with an elution gradient of acetonitrile-water containing propylamine. Under these conditions, the amines were eluted with short retention times. The procedure was used to determine amphetamine, or methamphetamine with its metabolite amphetamine, in spiked urine samples. The detection limit (at a signal-to-noise ratio of 3) for amphetamine (0.1 microgram/ml) was similar to that obtained with liquid-liquid derivatization and to those obtained with immobilized reagents on a polymeric solid support. The detection limit for methamphetamine (0.4 microgram/ml) was higher than with the liquid-liquid procedure because of the lower reactivity on the cartridge. The precision and accuracy of the method were also studied.

Topics: Amphetamine; Chromatography, High Pressure Liquid; Humans; Indicators and Reagents; Methamphetamine; Naphthoquinones; Substance Abuse Detection

A rapid method is described for the identification and determination of amphetamine and methamphetamine in human urine samples by liquid chromatography with UV-Vis detection. The samples were transferred onto a C18 solid-phase extraction column and chromatographed on a Hypersil ODS RP C18, 5 microns (250 x 4 mm I.D.) with an acetonitrile-water elution gradient containing propylamine. Under these conditions, the amines are eluted with a short retention time. The procedure has been applied to the determination of amphetamine and methamphetamine in the range 0.3-4.0 micrograms/ml in spiked urine samples. The detection limits at 280 nm were 4 and 2 ng/ml for amphetamine and methamphetamine, respectively. The intra-day and inter-day precision and accuracy of the method were studied.

Topics: Amphetamine; Chromatography, High Pressure Liquid; Humans; Indicators and Reagents; Methamphetamine; Naphthoquinones; Reproducibility of Results; Spectrophotometry, Infrared

A new chromatographic method for the determination of amino acids is proposed. The method is based on the separation of amino acids by means of ion-pair liquid chromatography and post-column derivatization using 1,2-naphthoquinone-4-sulfonate. The analytical column was a Spherisorb ODS 2. Amino acids were separated by an elution gradient with four linear steps based on increasing the concentration of 2-propanol. Two eluents were used to create the gradient profile: eluent A was an aqueous solution of 20 mM H3PO4 + 20 mM H2PO4(-) + 15 mM dodecyl sulfate and eluent B was a mixture of aqueous (25 mM H3PO4 + 25 mM H2PO4(-) + 18.5 mM dodecyl sulfate)-2-propanol (1:1, v/v). The injection volume was 100 microl and the total flow-rate for the mobile phase was 0.8 ml/min. The chromatographic outlet was coupled on-line to the two-channel derivatization system which delivered reagent and buffer solutions. The reaction took place at 65 degrees C in a reaction coil of 4 m x 1.1 mm I.D. The spectrophotometric detection was performed at 305 nm. The separation of common amino acids was done in 90 min, although an additional period of 15 min was required to stabilize the column. The repeatability of the method for lysine is 2.1% and the reproducibility is 2.6%. The detection limit for lysine is 0.09 nmol. The linear range for lysine is up to 32 nmol with a correlation coefficient of 0.999. The method was applied to the determination of amino acids in animal feed and powdered milks. The results of the method are in good agreement with those obtained with the standard amino acid autoanalyzer method.

Topics: Amino Acids; Animal Feed; Autoanalysis; Chromatography, Ion Exchange; Dairy Products; Indicators and Reagents; Naphthoquinones; Spectrophotometry, Ultraviolet

Topics: Amines; Chemical Phenomena; Chemistry; Chromatography, High Pressure Liquid; Electrochemistry; Indicators and Reagents; Naphthoquinones

A new postcolumn derivatization system using 1,2-naphthoquinone-4-sulfonate as fluorogenic reagent for the fluorometric determination of guanidino compounds is described. The guanidino compounds were separated by reversed-phase ion-pair high-performance liquid chromatography with an isocratic mobile phase containing the fluorogenic reagent and octane-sulfonate as the counterion. Fluorophors were derived from a condensation of guanidino compounds with the fluorogenic reagent in an alkaline solution. The chromatographic system using the mobile phase containing the fluorogenic reagent was simplified because only two pumps were required to deliver the mobile phase and the alkaline solution. Separation of guanidino compounds was completed within 25 min using a Nucleosil C8 column (5 microns, 15 cm X 4.6 mm i.d.). This method was applied to serum obtained from patients on hemodialysis therapy.

Topics: Chromatography, High Pressure Liquid; Fluorescent Dyes; Guanidines; Humans; Naphthoquinones; Renal Dialysis; Spectrometry, Fluorescence; Uremia

Topics: Chloromercuribenzoates; Erythrocytes; Glyoxal; Humans; Hypoxanthine Phosphoribosyltransferase; Kinetics; Naphthoquinones; Oxidation-Reduction; Protein Binding; Protein Conformation; Sulfhydryl Reagents

Topics: Chemistry, Pharmaceutical; Cresols; Naphthoquinones; Phenols; Research; Resorcinols; Sodium

Topics: Alkanesulfonates; Chemistry, Pharmaceutical; Indicators and Reagents; Naphthoquinones; Pharmacy; Quinones; Research; Sodium

Topics: Chemistry Techniques, Analytical; Chemistry, Pharmaceutical; Colorimetry; Naphthoquinones; Pharmacy; Phenols; Research; Resorcinols; Sodium; Sulfonic Acids

Topics: Abstracting and Indexing; Alkanesulfonates; Anesthetics; Anesthetics, Local; Colorimetry; Naphthoquinones; Sodium

Topics: Alkanesulfonates; Benzidines; Hazardous Substances; Naphthalenes; Naphthoquinones; Occupational Diseases; Potassium