Flow injection visible diffuse reflectance quantitative analysis of total sulfur in biodiesel, in plant leaves and in natural waters

Abstract

Flow injection (FI) methodology, using diffuse reflectance in the visible region of the spectrum, for the analysis of total sulfur in the form of sulfate, precipitated in the form of barium sulfate, is presented. The method was applied to biodiesel, to plant leaves and to natural waters analysis. The analytical signal (S) correlates linearly with sulfate concentration (C) between 20 and 120 ppm, through the equation S= 1.138+0.0934 C (r = 0.9993). The experimentally observed limit of detection is about 10 ppm. The mean R.S.D. is about 3.0 %. Real samples containing sulfate were analyzed and the results obtained by the FI and by the reference batch turbidimetric method using the statistical Student's t-test and F-test were compared.

Greener procedures for biodiesel quality control

“…117 Quantication was carried out in a ow system employing diffuse reectance spectrometry by exploiting the highly reproducible formation of barium sulphate suspensions. 117 Quantication was carried out in a ow system employing diffuse reectance spectrometry by exploiting the highly reproducible formation of barium sulphate suspensions.…”

“…In spite of being time-consuming and requiring high energy consumption, calcination was also exploited for sample preparation in the determination of total S by means of conversion to sulphate. 117 Quantication was carried out in a ow system employing diffuse reectance spectrometry by exploiting the highly reproducible formation of barium sulphate suspensions. However, because biodiesel generally has a low content of S in the organic form, the determination of free sulphate (from the sulphuric acid used in the trans-esterication reaction) could be exploited to evaluate the product quality.…”