mu Flow-injection-ICP collision cell MS determination of molybdenum, nickel and vanadium in petroleum samples using a modified total consumption micronebulizer

An interface based on a total consumption micronebulizer was developed for the introduction of xylene solutions into ICP MS. The increase in the nebulizer capillary diameter and the elimination of the internal connections reduced the problem of clogging, pressure instability and memory effects. The xylene carrier could be introduced for several hours at a rate of 30 ml min(-1). The sample (2.5 mu l) was injected into the carrier flow to produce peaks of 5 s at half-height (20 s at the base) which allowed a throughput of ca. 100 h(-1) for the simultaneous determination of Mo, Ni and V. Calibration curves with good linearity (R-2 > 0.999) over at least three orders of magnitude and detection limits at the sub-ng ml(-1) levels were obtained. The method was validated by the analysis of a sample by an independent (ICP AES) method and by the analysis of a NIST CRM 1085c lubricating oil material. The use of a helium-pressurized collision cell was essential to obtain good accuracy for Ni and V but was not required for Mo.