Gas-Phase Ion Association Provides Increased Selectivity and Sensitivity for Measuring Perchlorate by Mass Spectrometry

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• 作者：P. Kalyani Martinelango ; Jared L. Anderson ; Purnendu K. Dasgupta ; Daniel W. Armstrong ; Rida S. Al-Horr ; and Rosanne W. Slingsby
• 刊名：Analytical Chemistry
• 出版年：2005
• 出版时间：August 1, 2005
• 年：2005
• 卷：77
• 期：15
• 页码：4829 - 4835
• 全文大小：286K
• 年卷期：v.77,no.15(August 1, 2005)
• ISSN：1520-6882

文摘

Perchlorate (ClO<SUB>4^-) competitively inhibits the uptake ofiodide by the thyroid gland. Trace quantities of perchlorateare being increasingly detected in food and environmentalsamples. There is great concern that perchlorate contamination may be far more widespread than believed untilnow. Increasingly sensitive and unambiguous methodsare needed for measuring perchlorate. We report here anion chromatography-ion association-electrospray ionization-mass spectrometry (IC/IA-ESI-MS) method of substantially greater selectivity and sensitivity than otheravailable single-stage MS approaches. A long chain dipositive cationic agent (D²⁺) is added postcolumn in lowconcentration. This ion associates with perchlorate, evenin the gas phase. Perchlorate is, thus, detected as DClO₄⁺in the positive ion mode at an m/z value between 300and 400 (depending on the choice of D²⁺). This resultsin much better S/N and selectivity, as compared todetecting ³⁵ClO₄^- at m/z 99, where H³⁴SO₄^- also responds. We show results for various dicationic agentswhich vary in their selectivity and affinity for ClO₄^-,typically being at least 1 order of magnitude more selectivefor ClO₄^- over HSO₄^-. For a 100-s/entities/mgr.gif">L injected standard,limits of detection (LOD, S/N = 3) are as good as 25 ng/Lon a single quadrupole mass spectrometer. Calibrationfor concentrations up to 100 s/entities/mgr.gif">g/L displays an r² value ofs/entities/ge.gif">0.9993. We show applicability to various real samples.A number of the studied reagents are suitable for suchapplications.