Automatic gas chromatographic determination of N-methylcarbamates in milk with electron capture detection

Abstract

A new analytical method that combines on-line derivatization-extraction and gas-liquid chromatography for the determination of N-methylcarbamates is reported. The hydrolysis products of N-methylcarbamates (phenols) are derivatized and extracted in a continuous fashion using pentafluoropropionic anhydride (derivatizing reagent) in n-hexane as an extractant. The thermal instability of N-methylcarbamates is overcome by forming fluoro derivatives that can be identified and quantified at the nanogram per milliliter level with an ECD detector. Application of the proposed method to six mixtures of N-methylcarbamates yielded detection limits between 2 and 20 ng/mL and a relative standard deviation of 2.35-3.70%. Average recoveries of N-methylcarbamates added to cow's milk at concentrations between 50 ng/mL and 2 micrograms/mL ranged from 93.7 to 100.8%.

Trace level analysis of micropollutants in aqueous samples using gas chromatography with on-line sample enrichment and large volume injection

“…values of 1.9-3.9%. In a further study, the use of ECD and pentafluoropropionic anhydride as derivatization reagent improved the detection limits to the low p~g/l level [67]. This method was applied to the determination of N-methylcarbamates in cow milk.…”

Multiresidue determination of thermolabile insecticides in cereal products by gas chromatography–mass spectrometry: Evaluation with on‐column injection and conventional hot splitless injection

“…However, some thermolabile pesticides are easily degraded during gas chromatographic analysis if their stabilities are not improved through prior derivatization or other techniques [4], since relatively high temperatures have to be used in conventional GC to vaporize sample components. This severely limits multiresidue analysis of thermolabile species by conventional GC -MS techniques.…”

Chemiluminescence determination of carbofuran at trace levels in lettuce and waters by flow-injection analysis

“…Gas chromatography (GC) has been less used, since these compounds are somewhat polar and thermally unstable. Different authors propose methods based on GC with derivatization reactions [9,10], but it seems that the direct determination of carbamate pesticides is possible at very low concentrations [11,12]. Recently, mass spectrometry (MS) is becoming the detection system of choice for liquid chromatography, and has been applied for the monitoring of traces of this pesticide in fruits, vegetables [13] and water samples [14].…”