Determinação de cloreto em petróleo por espectrometria de absorção molecular de alta resolução com forno de grafite e fonte contínua

Abstract

In this work some procedures were proposed in order to enable the determination of chlorine in petroleum by using high resolution continuum source graphite furnace and molecular absorption spectrometry (HR-GF-MAS). Determinations were performed by molecular absorption measurements of diatomic AlCl, InCl and SrCl molecules, using Sr as chemical modifier. Some parameters such as pyrolysis and vaporization temperatures; Cl characteristic mass in solution and petroleum samples, in order to evaluate the possibility of calibration with aqueous standards. Moreover, the effect of chemical modifier in absorption signal; and evaluation of the sample mass range, limit of detection and calibration range for each molecule evaluated were carried out. Pyrolysis and vaporization curves were set as 600 and 2300 °C for AlCl, 700 and 2000 °C for InCl and 600 and 2000 °C for SrCl, respectively. Analyses were performed at 261,4180, 267,2181 and 635,8620 nm, for AlCl, InCl and SrCl, respectively. Accuracy was evaluated by analysis of certified reference material o petroleum, containing a non certified concentration of chlorine. In addition, the results obtained by HR-GF-MAS were compared to that obtained by IC after sample decomposition by MIC, and results obtained for petroleum samples with all the molecules evaluated were very concordant with the comparative method (MIC-IC). The better limit of detection (0.5 mg kg-1) and the lower characteristic mass (0.16 ng) were obtained using SrCl molecule. The proposed procedure enables direct analysis of petroleum with minimal sample handling, contributing to suitable limit of detection for the proposed application, aiming the determination of chlorine in trace level in complex samples, such as petroleum.