Comparison of flame ionization and inductively coupled plasma mass spectrometry for the detection of organometallics separated by capillary supercritical fluid chromatography.

Organotin compounds are separated by capillary supercritical fluid chromatography (SFC) and a comparison of the detection by flame ionization (FID) and inductively coupled plasma mass spectrometry (ICP-MS) is presented. Resolution, detection limits, linear dynamic range and reproducibility are the parameters compared between SFC-FID and SFC-ICP-MS, for the detection of tri- and tetraorganotin compounds. The resolution obtained in the SFC-FID system is not always observed in SFC-ICP-MS. Degradation in resolution is due to fluctuations in transfer line temperature. Baseline resolution for the organotins considered is achieved in both systems by using a longer column. Detection limits (DLs) are calculated as 3 sigma/S, where sigma is the standard deviation of the blank signal and S is the slope of the calibration curve. Detection limits of 10.3, 12.5, 12.0 and 9.0 pg are obtained for tetrabutyltin, tributyltin chloride, triphenyltin chloride and tetraphenyltin, respectively, using SFC-FID. An improvement in detection limits of one order of magnitude is achieved by SFC-ICP-MS for the same organotins (0.26, 0.80, 0.57 and 0.20 pg, respectively). The relative standard deviations using SFC-FID for five 50-nl injections, containing 0.5 ng Sn, ranged from 3.2 to 6.4%. Using SFC-ICP-MS, five replicate injections of 0.05 ng Sn give R.S.D.s from 1.3 to 3.4%.