2-methylisoborneol and 2-isopropyl-3-methoxypyrazine

Topics: Actinomycetales; Camphanes; Chemical Phenomena; Chemistry; Fresh Water; Naphthols; Nocardia; Odorants; Pyrazines; Pyrones; Species Specificity; Streptomyces; Water Microbiology; Water Pollution

Taste and odor (T&O) compounds are widespread in water environments and have attracted considerable public attention. Nowadays, the standard detections of these chemicals rely mainly on off-line methods such as GC-MS or evaluation by trained analysts' senses. In this study, we report a method for the rapid detection of T&O compounds in water by exploiting a newly invented chemi-ionization source, in combination with headspace vapor measurement at room temperature. The calibrated limits of detection (LODs) of 2-methylbutyraldehyde, methyl tert-butyl ether (MTBE), methyl methacrylate (MMA), 2-isobutyl-3-methyoxypyrazine (IBMP), and 2-isopropyl-3-methoxypyrazine (IPMP) are in the range of 3.5-50.2 ng L

Topics: Aldehydes; Camphanes; China; Diterpenes; Limit of Detection; Mass Spectrometry; Naphthols; Odorants; Pyrazines; Reproducibility of Results; Rivers; Taste; Water Pollutants, Chemical

Rapid and direct, in situ headspace screening for odoriferous volatile organic compounds (VOCs) present in fresh grapes and in wines is a very promising method for quality control because the economic value of a wine is closely related to its aroma. Long used for the detection of VOCs in complex mixtures, miniature differential ion mobility spectrometry (DMS) seems therefore adequate for in situ trace detection of many kinds of VOCs of concern appearing in the headspace of selected foodstuffs. This work aims at a rapid detection, identification, and quantification of some natural and volatile contaminants of wine such as geosmin, 2-methylisoborneol (2-MIB), 1-octen-3-ol, 1-octen-3-one, and pyrazines (2-isopropyl-3-methoxypyrazine, IPMP, and 3-isobutyl-2-methoxypyrazine, IBMP). In the present study, these compounds were spiked at a known concentration in wine and analyzed with a hyphenated trap-GC-DMS device. The detection of all target compounds at concentrations below the human olfactory threshold was demonstrated.

Topics: Camphanes; Gas Chromatography-Mass Spectrometry; Humans; Ketones; Naphthols; Octanols; Olfactometry; Pyrazines; Smell; Vitis; Volatile Organic Compounds; Wine

An automated technique based on purge-and-trap coupled to gas chromatography with mass spectrometric detection has been developed and optimized for the trace determination of five of the most important water odorants; 2-isopropyl-3-methoxypyrazine, 2-isobutyl-3-methoxypyrazine, 2-methylisoborneol, 2,4,6-trichloroanisole and geosmin. The extraction method was absolutely solvent-free. Analytes were purged from 20 ml of water sample containing sodium chloride at room temperature by a flow of He and trapped on a Tenax sorbent. The desorption step was performed with helium and temperature programming and desorbed analytes were directly transferred to a gas chromatograph coupled to a mass spectrometer for separation and determination. The method was reproducible (RSD<8%) and linear over the calibration range (10-200 ngl(-1)). The relative recoveries of the analytes from ground water sample were calculated and were between 80 and 103% and limits of detection (LOD) below odor thresholds were achieved for most of the compounds.

Topics: Anisoles; Automation; Camphanes; Gas Chromatography-Mass Spectrometry; Naphthols; Odorants; Online Systems; Pyrazines; Sensitivity and Specificity; Water

The removal of four earthy-musty compounds, 2-methylisoborneol (MIB), 2,4,6-trichloroanisole (TCA), 2-isopropyl-3-methoxy-pyrazine (IPMP), and 2-isobutyl-3-methoxy-pyrazine (IBMP), by powdered activated carbon (PAC) were investigated under the simulative condition of Xicun water plant, Guangzhou. The adsorption kinetics of odor compounds by two PACs show that main removal of odor compounds occurs within contact time of 1 h. Compared with the wood-based PAC, the coat-based PAC evidently improves the removal efficiency of poorly adsorbed compounds like MIB. The effects on removal efficiency such as optimum PAC dosage, initial concentration of the organics, chlorine residual, background organics, and changes of water quality were investigated. The percent removal of trace odorants at any given time for a particular carbon dosage is irrelative to the initial concentration of the odor compounds. Adsorptive capacity of PAC for target compounds is reduced by chlorine residual and background organics. Characteristics of raw water have vast influence on the removal of target compounds by PAC.

Topics: Adsorption; Anisoles; Camphanes; Carbon; China; Chlorine; Odorants; Pyrazines; Rivers; Water Pollutants, Chemical; Water Purification