Pesticide analysis with the pulsed-flame photometer detector and a direct sample introduction device

New methods for fast, sensitive, and informative pesticide analysis in food products are described. These methods are based on sampling with a novel direct sample introduction device (DSI), gas chromatographic analysis, and pesticide detection with the pulsed flame photometric detector (PFPD). Sampling with the DSI is based on introduction of blended fruit or vegetable in a small glass vial that retains the harmful nonvolatile residue and is disposed of after the analysis. The DSI-GC-PFPD combination provides several new features that are demonstrated and discussed:  (a) Extract-free analysis is achieved with the DSI, which serves as an effective alternative to sample extraction and cleanup methods. (b) Faster analysis is achieved through the use of the DSI due to the reduction of the upper GC program temperature, since the low-volatility compounds are retained in the sample vial. (c) Relatively efficient and uniform DSI thermal extraction and PFPD detection can be achieved, allowing the use of internal standards for pesticide calibration. (d) Higher sensitivity is provided by the PFPD as well as through the use of the DSI for sampling larger volumes of extract solutions. (e) Sulfur interference is eliminated with the PFPD in its phosphorus-selective detection mode, using software exploiting differences in S and P delayed pulsed flame emission time dependence. (f) Sulfur pesticides are effectively analyzed by the PFPD in its sulfur-selective detection mode at the usual required levels and with less matrix interference than with NPD in the nitrogen mode. (g) Simultaneous sulfur and phosphorus pesticide analysis is demonstrated, including heteroatom identification and the provision of P and S atom ratio information in the analyzed pesticide.