Comparison of three coupled gas chromatographic detectors (MS, MIP-AES, ICP-TOFMS) for organolead speciation analysis

An automatic unit for the screening of rainwater is used for the determinat ion of organolead compounds using different detectors coupled to a gas chro matograph. A systematic overview is given of the advantages and disadvantag es of several detectors (electron ionization mass spectrometry, ELMS; micro wave induced plasma atomic emission spectrometry, MIP-AES; and inductively coupled plasma time-of-flight mass spectrometry, ICP-TOFMS, for the speciat ion of organolead compounds on the basis of sensitivity, selectivity and re liability. C-60 fullerene and RP-C-18 were used as sorbent materials for th ese compounds. The primary assets of the fullerene sorbent, as compared to C-18 sorbent, are high sensitivity and selectivity resulting from efficient adsorption due to large surface area and interstitial volume. Among the de tection systems, GC/ICP-TOFMS is the most sensitive, with absolute detectio n limits of similar to 15 fg of organolead compounds (as lead) using 5-mL s ample volumes. Except for diethyllead, similar sensitivities were obtained by MIP-AES. GC/MS is intrinsically the most specific option, because the sp ecies are detected directly from molecular information. The precision is si milar for all detectors. The screening of rainwater from different location s showed that samples collected in countries in which leaded gasolines are now banned contain organolead species at concentrations below 2 pg/ml, leve ls that can be detected only for sample volumes of 25 mL and using MIP-AES or ICP-TOFMS as detectors, their determination being impossible by GC/MS.