Gas chromatography–inductively coupled plasma time-of-flight mass spectrometry for the speciation analysis of organometallic compounds

An inductively coupled plasma time-of-flight mass spectrometer was combined with a capillary gas chromatograph for the speciation analysis of organotin and organolead compounds. The ability to produce complete mass spectra at a high frequency (typically >20 000 mass spectra per second) makes time-of-flight mass spectrometry nearly ideal for the detection of transient signals such as those produced by high speed chromatographic techniques. In this study, GC-ICP-TOFMS instrumental figures of merit were determined for the separation of tetramethyltin, tetraethyltin and tetraethyllead. Data acquisition speed of the current system was limited to 78 integrated complete mass spectra (255 individual spectra summed) per second. However, because all mass-to-charge ratios are detected, collection of a data point every 12.75 ms is sufficient for the measurement of all but the fastest transient signals (peak widths <50 ms). A tin isotope-ratio accuracy of 0.28% and a precision of 2.88% (RSD) were calculated for a 1 s gas chromatographic peak of tetramethyltin. Limits of detection for all three analytes were found to be in the low femtogram region, with a dynamic range of greater than six orders of magnitude.