Mercury speciation by capillary gas chromatography coupled with time-of-flight ICP-MS for evaluation of high precision isotope ratio measurements

An in-house transfer line was designed for coupling a gas chromatograph (GC) to an inductively coupled plasma time-of-flight mass spectrometer (ICP-TOFMS) to test the system as a viable option for organomercury speciation. Particular emphasis concentrated on assessing the ability of the ICP-TOFMS for measuring high precision isotope ratios from a transient source for mercury speciation analysis. Delivery of short duration signals into an ICP-MS, such as those produced from chromatographic instruments, provides a real challenge for making high precision isotope ratio measurements. Integration of transient peaks deny mass spectroscopists the luxury of measuring isotopes over an extended period, a feature continuous nebulization enjoys, and has been shown to improve precision in isotope ratio measurements. A decrease in the statistical variance for isotope ratio measurements is especially desirable in low level environmental analysis, as lower relative standard deviations (RSDs) improve the isotope dilution method and provides added validity to tracer studies. (Abstract shortened by UMI.).