The use of dried matrix spot for determination of Pb and Ni in automotive gasoline by solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry

In this work a simple and practical method for the determination of Pb and Ni in automotive gasoline by solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry was investigated. In the proposed method, disks of filter paper were used to pre-concentrate and store Pb, Ni and other trace elements from automotive gasoline samples. For this, a volume of sample was deposited and dried out on a filter paper disk previously adapted into a polytetrafluoroethylene mold, and then the gasoline-embedded filter paper was either cut into small pieces or pulverised and introduced directly into the graphite furnace for trace element determination. Temperature program, use of chemical modifier, chromatographic effect and volume of sample were investigated. Calibration curves using organic and inorganic standards of the analytes as well as external and internal calibration methods were evaluated. Using optimised conditions, characteristic masses and limits of detection of 6 and 11 pg, and 0.5 and 2.1 mu g L-1. were found for Pb and Ni, respectively. The accuracy of the method was evaluated with spike-recovery tests and a certified reference material of wear lubricant oil. The spike-recovery tests were accomplished for 9 samples and the best results were obtained with the pulverised filter paper. A second method that employs a transversely heated filter atomiser was applied as a comparative one. The filter paper was shown to be a simple and inexpensive tool for storage and transportation of gasoline samples, and it allowed the pre-concentration of the analytes, since a larger volume of sample can be dried out on it.