Determination of Arsenobetaine in Fish Tissue by Species Specific Isotope Dilution LC-LTQ-Orbitrap-MS and Standard Addition LC-ICPMS

An accurate and precise method for the determination of arsenobetaine (AsB, (CH3)3+AsCH2COO−) in fish samples using exact matching species specific isotope dilution (ID) liquid chromatography LTQ-Orbitrap mass spectrometry (LC-LTQ-Orbitrap-MS) and standard addition LC inductively coupled plasma mass spectrometry (LC-ICPMS) is described. Samples were extracted by sonication for 30 min with high purity deionized water. An in-house synthesized 13C enriched AsB spike was used for species specific ID analysis whereas natural abundance AsB, synthesized and characterized by quantitative 1H NMR (nuclear magnetic resonance spectroscopy), was used for reverse ID and standard addition LC-ICPMS. With the LTQ-Orbitrap-MS instrument in scan mode (m/z 170−190) and resolution set at 7500, the intensities of [M + H]+ ions at m/z of 179.0053 and 180.0087 were used to calculate the 179.0053/180.0087 ion ratio for quantification of AsB in fish tissues. To circumvent potential difficulty in mass bias correction, an exact matc...