Wylie P L
Hewlett-Packard Co., Wilmington, DE 19808-1610, USA.
J AOAC Int. 1996 Mar-Apr;79(2):571-7.
Gas chromatographic (GC) analysis of 6 organophosphorus pesticides (methamidophos, acephate, omethoate, diazinon, dimethoate, and chlorpyrifos) was performed with cool on-column, splitless, and pulsed splitless injections and with nitrogen-phosphorus or mass-selective detection. The pulsed splitless technique uses a high column flow rate during injection to sweep the sample out of the inlet rapidly, reducing analyte loss due to adsorption or thermal decomposition. After injection, the column flow rate is automatically reduced to normal values for chromatographic analysis. Pesticide recoveries for splitless and pulsed splitless injections were determined by comparison of GC peak areas with those obtained with cool on-column injection. With conventional splitless injection at a column flow rate of 5 mL/min, recoveries of acephate, omethoate, and methamidophos were only 57, 63, and 71%, respectively. Pulsed splitless methods with very fast injection flow rates dramatically improved recoveries, with all 6 pesticides falling in the 97-102% range. Because column flow rates are much less for GC with mass spectral detection (GC/MS), recoveries with splitless injection were lower and improvements with pulsed splitless injection were less dramatic for GC/MS. When splitless injection was used, recoveries of the 6 pesticides spiked into a green bean matrix were better than those of pesticides dissolved in pure solvent, presumably because matrix compounds compete with pesticides for active sites in the inlet. By using pulsed splitless injection of solvent standards with very fast initial column flow rates, systematic analyte losses in the inlet were eliminated, making recoveries of pesticides from solvent and green bean matrix very similar.
采用冷柱头进样、不分流进样和脉冲不分流进样，并结合氮磷检测或质量选择检测，对6种有机磷农药（甲胺磷、乙酰甲胺磷、氧乐果、二嗪农、乐果和毒死蜱）进行气相色谱（GC）分析。脉冲不分流技术在进样期间使用高柱流速，以便迅速将样品从进样口吹扫出去，减少由于吸附或热分解导致的分析物损失。进样后，柱流速自动降至正常色谱分析值。通过将不分流进样和脉冲不分流进样的气相色谱峰面积与冷柱头进样获得的峰面积进行比较，测定农药回收率。在柱流速为5 mL/min的常规不分流进样条件下，乙酰甲胺磷、氧乐果和甲胺磷的回收率分别仅为57%、63%和71%。采用极快速进样流速的脉冲不分流方法显著提高了回收率，所有6种农药的回收率均在97%至102%范围内。由于采用质谱检测（GC/MS）的气相色谱柱流速要低得多，因此不分流进样的回收率较低，而脉冲不分流进样对GC/MS的回收率提高幅度较小。当采用不分流进样时，添加到绿豆基质中的6种农药的回收率优于溶解在纯溶剂中的农药回收率，推测是因为基质化合物与农药竞争进样口中的活性位点。通过使用具有极快速初始柱流速的溶剂标准品脉冲不分流进样，消除了进样口中分析物的系统损失，使得从溶剂和绿豆基质中回收农药的情况非常相似。
