Expanding the potentialities of standard dilution analysis: Determination of ethanol in gasoline by Raman spectroscopy

Abstract

This work describes the application of standard dilution analysis (SDA) in Raman spectroscopy, demonstrating the versatility of this new calibration method. A flow system (FA) was developed for ethanol determination in gasoline employing liquid-liquid extraction (LLE) and acetone as the internal standard (IS). Applying LLE eliminated the intense fluorescence background, allowing for ethanol determination using a portable 785-nm-laser Raman system. The SDA-LLE-FA method was applied to commercial gasoline samples and the results were compared with values obtained using the ABNT NBR 13992 reference method. No statistically significant differences were observed for ethanol concentrations determined using the two methods (paired t-test at the 95% confidence level). SDA's accuracy was also evaluated by comparing results from analyses using the same LLE-FA system combined with the traditional calibration methods of matrix matching (MM), standard additions (SA) and internal standardization (IS). Recoveries from spike experiments were in 98.6-104.1% (SDA-LLE-FA), 94.7-171.1% (ABNT NBR 13992), 106.8-114.1% (MM-LLE-FA), 103.7-108.4% (IS-LLE-FA), and 114.7-125.8% (SA-LLE-FA) range. The relative standard deviation (RSD, n = 12, 25.5% v/v −1 ethanol in gasoline), limits of detection and quantification calculated for the SDA-LLE-FA method were 2%, 0.5% and 1.8% (v/v −1 ), respectively.

Traditional Calibration Methods in Atomic Spectrometry and New Calibration Strategies for Inductively Coupled Plasma Mass Spectrometry

“…Thus, SDA, MICal and MSC accuracies are comparable and often better than the traditional EC, IS, and SA methods (Jones et al, 2015 ; Virgilio et al, 2018 ; Williams and Donati, 2018 ). SDA may be more broadly applicable than MICal and MSC, as it has been successfully used in UV-vis, FAAS, MIP OES, ICP OES, and Raman spectroscopy in addition to ICP-MS (Jones et al, 2015 ; Fortunato et al, 2016 , 2017 ; Gonçalves et al, 2016b ; Virgilio et al, 2016a , b ; Althoff et al, 2017 ; Table 4 ). Because it employs an internal standard, it is also capable of correcting for signal fluctuations due to instrument variations.…”

Automated standard dilution analysis using a four-port switching valve for fast inductively coupled plasma optical emission spectrometry determination

“…15 By employing fewer calibration solutions compared to SA, SDA is a faster, greener alternative, as it requires fewer resources and produces less waste, while equally combatting matrix effects. 15,[20][21][22][23][24] In SDA, matrix matching is achieved by using two calibration solutions (S1 and S2) containing each 50% by volume of sample. The other 50% by volume is either a standard solution containing the analytes and an internal standard (for S1), or a blank solution containing a second internal standard (for S2).…”

“…15 By employing fewer calibration solutions compared to SA, SDA is a faster, greener alternative, as it requires fewer resources and produces less waste, while equally combatting matrix effects. 15,20–24…”

Real‐time Raman analysis of cleaning solution: Determination of Al/Alq3 residue in cleaning mixture

“…As the application of light has become more diverse, laser spectroscopic techniques have been employed to overcome the disadvantages of other analytical instruments. Raman spectroscopy has been widely used and studied in the past, but its widespread use is hampered due to limitations in the laser power and restriction of the prism reception . However, by upgrading these systems, measurements can be easily performed in a short time.…”