The presence of chloride in crude
oil can result in a number of
drawbacks, with technical and economic impacts on the production of
petroleum derivatives. For this reason, it must be carefully monitored
in this kind of sample. In this work, we developed a simple and efficient
method for the determination of chloride in crude oil by ion chromatography
with conductivity detection after microwave-assisted extraction. The
method was optimized using a multivariate strategy based on the use
of a two-level full factorial design for the screening of significant
factors and a Doehlert matrix for their optimization. Four factors
were selected in this study: mass of the sample, extraction temperature,
extraction time, and the volume of toluene employed to disperse the
sample. Under optimized conditions, 1.10 g of the sample was dispersed
in 3.0 mL of toluene and 10 mL of deionized water was added. The mixture
was irradiated for 25 min at 146 °C (extraction temperature).
After cooling, the mixture was centrifuged for 15 min at 5000 rpm
for separation of the phases, and the aqueous extract was filtered
and analyzed by ion chromatography. The limits of detection and quantification
of the method were 0.13 and 0.39 μg g–1, respectively.
The method was applied in the determination of chloride in four samples
of crude oil, and the obtained results were statistically similar
to those obtained by the reference method (ASTM D6470).
The present work reports the development of ion chromatography conductivity based detection analytical method for the determination of some inorganic anions (chloride, sulfate and phosphate) in vegetable oils. The analytes were extracted from samples prior to injection into the chromatographic system, employing a simple two-step procedure. In the first step, 4.5 g of the sample was vigorously mixed with 15 mL of deionized water and then mixed for 15 min on a horizontal roller. Afterwards, the mixture was sonicated for 15 min in an ultrasonic bath. Then, the mixture was centrifuged for 15 min at 5000 rpm and, after filtration through a 0.22 μm membrane, the aqueous phase was used for the determination of the analytes. A clean-up step was introduced in the analysis of olive oils in order to correct an increase of the baseline of the chromatograms. The limits of detection and quantification of the proposed method were, respectively, 0.005 and 0.02 μg g for chloride, 0.02 and 0.06 μg g for phosphate and 0.008 and 0.03 μg g for sulfate. Vegetable oils from corn, canola, soybean, sunflower and olive were analyzed and recovery tests (94.8 ± 10.1% mean recovery) were performed to attest the accuracy of the proposed method.
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