Direct determination of Cu and Fe in jet fuel by electrothermal atomic absorption spectrometry with injection of sample as detergent emulsions

AbstractThis paper reports the development of a method for the determination of copper and iron in jet fuels employing the electrothermal atomic absorption spectrometry (ETAAS). In order to allow the direct determination of the analytes, the samples were injected into the graphite furnace as detergent emulsions in order to avoid their volatilization during analysis. The results obtained in this work indicated that a stable emulsion can be formed by mixing 1mL of a 7% m/v Triton X-100 solution containing 10% v/v HNO3 with 4mL of jet fuel. The injection of emulsions provided integrated absorbance signals with suitable sensitivity and precision for 300min at least. The addition of chemical modifier was not necessary because background values were always very low, allowing the use of pyrolysis temperature around 1000°C for both analytes. Both Triton X-100 and HNO3 concentrations in the solution used to form the emulsion had remarkable influence on the sensitivity as well as the heating rate employed in the drying step. Under the best conditions established in the present work, limits of detection of 0.50 and 0.46μgL−1 were observed for copper when oil-based and aqueous standards were added to the emulsions for calibration, respectively. For iron, the limits of detection were 0.88 and 0.90μgL−1 for oil-based and aqueous standards, respectively. The method was applied in the determination of Cu and Fe in five samples of jet fuels and a recovery test was performed, producing recovery percentages between 95% and 105%

Novel spectrophotometric method for the determination of azithromycin in pharmaceutical formulations based on its charge transfer reaction with quinalizarin

This paper proposes a new method for simple and fast spectrophotometric determination of azithromycin in pharmaceutical formulations. The method is based on the charge transfer reaction between the azithromycin and quinalizarin in methanol medium. In order to achieve maximum sensitivity the effect of some chemical variables such as the type of solvent, reagent concentration and reaction time were evaluated. The reaction was characterized in terms of stability of the product formed and its stoichiometry, and the apparent molar absorptivity and association constant were derived. Best conditions for the analytical determination of azithromycin were observed in methanol medium with a quinalizarin concentration of 50 mg L-1. At these conditions, the radical anion (absorbing specie) was formed in the medium immediately after mixing of the reagents and showed maximum absorption at 564 nm. The method presented a limit of detection of 0.35 mg L-1 and a limit of quantification of 1.2 mg L-1. It was successfully applied in the determination of azithromycin in three commercial pharmaceutical formulations of azithromycin and no matrix interferences were observed

Microwave-Assisted Extraction of Chloride Followed by Ion Chromatography as an Alternative to the ASTM D6470 Method for the Determination of Crude Oil Salinity

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 twolevel 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).UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Químic

Estudo da sorção do corante catiônico violeta cristal por espuma de poliuretano em meio aquoso contendo dodecilsulfato de sódio Sorption of crystal violet by polyurethane foam from aqueous medium containing sodium dodecylsulfate

<abstract language="eng">This work presents a detailed study about the sorption of crystal violet (CV) cationic dye onto polyether type polyurethane foam (PUF). The sorption process was based on the formation of an ionic-pair between cationic dye and dodecylsulfate anion (SDS), which presented high affinity by PUF. Set-up employed in the study was built up by adjusting a 200 mg cylinder of PUF to the arm of an overhead stirrer. The system was characterized in relation to equilibrium and kinetic aspects and it was modeled by employing Langmuir and Freundlich isotherms. Obtained results showed that the ratio between SDS and MB concentrations played an important role on the sorption process. According to results found it was possible to retain up to 3.4 mg of dye from 200 mL of a 5.0 x 10-5 mol L-1 CV solution containing 1.25 x 10-4 mol L-1 SDS, which represented a removal efficiency of around 92%

Development of an extraction method for the determination of inorganic anions (chloride, sulfate and phosphate) in edible oils from different origins by ion chromatography

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-1 for chloride, 0.02 and 0.06 μg g-1 for phosphate and 0.008 and 0.03 μg g-1 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.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Químic

Determination of acetate and formate in vegetable oils by ion chromatography after multivariate optimization of the extraction process using a Doehlert design

In this work, we present the development of a method for the determination of acetate and formate in vegetable oils by ion chromatography with conductometric detection following their extraction from samples using a diluted KOH solution. The extraction procedure was optimized using a multivariate approach. The application of a 24 full factorial design showed that the mass of sample, extraction time, and KOH concentration presented significant influence on the extraction of both acetate and formate, whereas the temperature presented little influence on the process. As a result, we set the extraction temperature at 22 °C and performed the multivariate optimization of the other variables using a Doehlert design. The optimum conditions were: 4.8 g of sample, 8 mmol L−1 KOH solution and 19 min extraction time. Six samples of vegetable oils (soybean, corn, canola, sunflower and olive) were analyzed and recovery tests provided recovery percentages in the range of 82–118%.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Químic

Simple Spectrophotometric Determination of Iron in Diesel Oil after Sample Preparation Employing Extraction Induced by Emulsion Breaking

This work reports the development of a simple and fast method for the spectrophotometric determination of Fe in diesel oil using the classic reaction with 1,10-phenanthroline after its extraction induced by emulsion breaking (EIEB). The extraction parameters of EIEB were optimized (concentration of HNO3 and Triton X-100® in the emulsifying solution) as well as the adjustment of the pH of the final solution, a necessary step to complete the colorimetric reaction. The developed method presented a limit of detection of 0.004 mg L-1 and a limit of quantification of 0.013 mg L-1 and was applied in the analysis of six samples of diesel oil with different specifications. The results were statistically similar to those obtained by graphite furnace atomic absorption spectrometry (GF AAS). A recovery test was also performed by spiking the samples with 1.0 mg L-1 of Fe in the form of an organometallic compound, yielding recovery percentages between 83 and 108%.</div

Determination of adulterants of cocaine in Real banknotes in Brazil by HPLC-DAD

Cocaine is a tropane alkaloid extracted from coca leaves, a common bush found in Andean regions of South America. Many medicines are added to the final product to increase the profits, keeping similar or higher effects than cocaine alone. Stimulants, anesthetics, and sedatives are the most found adulterants. The goal of this work was to propose a novel analytical methodology to determine cocaine and the main medicines found in street cocaine in Real banknotes using high-performance liquid chromatography with diode array detection (HPLC-DAD). Under optimized conditions, the target substances were extracted with acetonitrile, and the cleanup of the obtained extracts was carried out by separating the fatty layer at low temperature (–20 °C). The volume of extract was reduced under nitrogen flow and adjusted to 2.5 mL with a solution containing 95% (v/v) of phosphate buffer (10 mmol L−1, pH = 2.5) and 5% (v/v) of acetonitrile. Under these conditions, it was possible to identify and quantify cocaine and its adulterants in the samples, with limits of quantification of 0.29, 0.012, 0.16, 0.22, 0.026, 0.078, and 0.14 µg per banknote for acetaminophen, levamisole, caffeine, lidocaine, cocaine, diltiazem, and phenacetin, respectively. We analyzed 158 samples, and only one did not present any of the tested substances. Higher amounts of the tested substances were verified in banknotes of lower value.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Químic