Amirav A, Jing H
School of Chemistry, Tel Aviv University, Israel.
J Chromatogr A. 1998 Jul 24;814(1-2):133-50. doi: 10.1016/s0021-9673(98)00415-4.
Analysis of pesticides by simultaneous pulsed flame photometric detection (PFPD) and mass spectrometric (MS) detection was performed with column-effluent splitting between these two detectors. The resulting PFPD chromatograms were always much simpler due to the PFPD selectively and were further characterized by better sensitivity than that of MS. Accordingly, the PFPD chromatogram served as a marker for the exact elution time of the suspected pesticide. At this exact elution time, the resulting mass spectra were examined of unique high-mass peaks and a precise background subtraction was performed for improved library identification. If no definite identification was achieved, reconstructed mass chromatograms were performed, inspected for suspected major ions and confirmed with the PFPD chromatogram. A sequential search was then performed with the NIST library. The presence of P or S atoms was introduced into the search algorithm and two of the major suspected fragment mass peaks were included with an estimate of their minimum relative abundance. Under these conditions, the library search provided the correct pesticide identification, at a considerably lower concentration than achievable with standard GC-MC analysis. If only information on a single ion was available, such as with very pronounced matrix interferences, or with single-ion monitoring MS analysis, the NIST library sequential search was operated with this single-on information and PFPD provided information on both P and S (the majority of organophosphorus pesticides contain both P and S). The incorporation of one major ion and two heteroatoms' (P and S) information enabled an effective library identification, at an even further reduced pesticide concentration. The simultaneous PFPD-MS analysis approach is demonstrated and discussed with several examples of authentic pesticides in vegetable and spices. The merits of this method are analyzed and discussed with an emphasis on the unique suitability of PFPD for combination with MS.
采用同时脉冲火焰光度检测（PFPD）和质谱（MS）检测对农药进行分析，在这两个检测器之间进行柱流出物分流。由于PFPD具有选择性，得到的PFPD色谱图总是简单得多，并且其灵敏度比MS更好。因此，PFPD色谱图可作为可疑农药准确洗脱时间的标记。在这个准确的洗脱时间，检查得到的质谱图中的独特高质量峰，并进行精确的背景扣除以改进谱库识别。如果未实现明确识别，则进行重建质量色谱图，检查可疑的主要离子并用PFPD色谱图进行确认。然后使用NIST谱库进行顺序搜索。将P或S原子的存在引入搜索算法，并包括两个主要的可疑碎片质量峰及其最低相对丰度估计值。在这些条件下，谱库搜索提供了正确的农药识别结果，浓度比标准GC-MS分析所能达到的浓度低得多。如果仅获得关于单个离子的信息，例如存在非常明显的基质干扰，或进行单离子监测MS分析时，NIST谱库顺序搜索使用此单离子信息进行，而PFPD提供关于P和S的信息（大多数有机磷农药同时含有P和S）。纳入一个主要离子和两个杂原子（P和S）的信息能够在更低的农药浓度下实现有效的谱库识别。通过蔬菜和香料中几种真实农药的实例展示并讨论了同时进行PFPD-MS分析的方法。分析并讨论了该方法的优点，重点强调了PFPD与MS联用的独特适用性。
