GC-ICP-MS/MS Instrumental Setup for Total and Speciation Sulfur Analysis in Gasolines using Generic Standards

Quantitative characterization of sulfur-containing petroleum derivatives is mainly limited by the large number of potential targets present and the matrix effects suffered due to the high-carbon-containing matrices. Herein we describe the instrumental modifications required in a commercial GC-ICP-MS/MS instrument, and their corresponding optimization, for turning it into a compound-independent quantitative technique for both total and speciation sulfur analysis in gasolines. Additionally, carbon-derived matrix effects were made negligible for direct and fast total S analysis, making the use of relatively complex isotope-dilution strategies not necessary anymore. An absolute detection limit of 0.3 pg of S was achieved, which is, to the best of our knowledge, more than 1 order of magnitude below the ones reported for other sulfur GC selective detectors. The precision was below 3% RSD. Total analysis was performed by flow-injection analysis through a transfer line and external calibration, whereas speciation analysis was carried out by chromatographic separation and internal standardization. In both cases, simple generic standards were used, which enabled us to get rid of specific S-containing standards, which were sometimes not available or unstable. The proposed method was successfully applied to total and speciation sulfur analysis of a commercial gasoline sample and validated with a certified-reference-material (ERM-EF213) gasoline. The approach has proved to be simple, fast, robust, and convenient for implementation in routine laboratories, as demonstrated by the successive analyses of 50 gasoline samples in 3 h without any instrumental drift.