Large Volume Cold On-Column Injection for Gas Chromatography−Negative Chemical Ionization−Mass Spectrometry Analysis of Selected Pesticides in Air Samples

A new gas chromatographic method is described for the analysis of fungicides captan, captafol, and folpet from organic extracts of air samples using large volume injection (LVI) via a cold on-column (COC) inlet coupled with gas chromatography−negative chemical ionization−mass spectrometry (GC-NCI-MS). Although standard split/splitless injection due to high injection port temperatures (>225 °C) have been shown to degrade these thermally labile fungicides, COC injection minimizes degradation. Insecticides such as chlorpyrifos and diazinon were also examined to show added selectivity. By using a solvent vapor exit with the COC inlet, injection volumes of 10−100 μL can be made to lower detection levels. GC-NCI-MS was compared to GC−electron impact ionization−mass spectrometry for each pesticide using LVI-COC injections and was found to be 2−80 times more sensitive, depending on the pesticide. Method detection limit (MDL) values with 100 μL injections were 2.5 μg L-1 for captan, folpet, and diazinon, 5.0 μg L-1 captafol, and 1.0 μg L-1 for chlorpyrifos, with the normal working range examined for sample analysis from MDL to 100 μg L-1. Detection of all pesticides except captafol, used only in the United States but not Canada, was demonstrated from air samples taken from Abbotsford, British Columbia, Canada. Keywords: Cold on-column; large volume injection; gas chromatography−mass spectrometry; pesticides; fungicides