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Infrared thermal imaging was combined with disposable microplates to perform enthalpimetric analysis using an infrared camera to monitor temperature without contact. The proposed thermal infrared enthalpimetry (TIE) method was used to determine the total, fixed and volatile acidities of vinegars. Sample preparation and analysis were performed in the same vessel, avoiding excessive sample handling and reducing energy expenditure by more than ten times. The results agreed with those of the conventional method for different kinds of vinegars, with values of 1.7%, and 2.3% for repeatability and intermediate precision, respectively. A linear calibration curve was obtained from 0.040 to 1.30 mol L −1 . The proposed method provided rapid results (within 10 s) for four samples simultaneously, a sample throughput of up to 480 samples per hour. In addition, the method complies with at least eight of twelve recommendations for green analytical chemistry, making TIE a promising tool for routine vinegar analysis. [ABSTRACT FROM AUTHOR]

Edible seaweed has been widely consumed around the world through oriental cuisine and it is important to monitor the levels of some elements, especially halogens. This study proposes, for the first time, the development of an analytical method using the vortex-assisted matrix solid-phase dispersion (VA-MSPD) combined with alkaline extraction of halogens (F, Cl, Br, and I) in edible seaweed for further determination by ion chromatography. The proposed method was evaluated using edible seaweed of the Nori (Porphyra spp.) type and applied to samples of the Wakame (Undaria pinnatifida), Kombu (Laminaria ochroleuca), and Hijiki (Hizikia fusiformis) types. Important VA-MSPD parameters were investigated and using 0.1 g sample, 1 g sea sand as solid support, 50 mmol L−1 (NH 4) 2 CO 3 as extraction solution, and 5 min of maceration, higher extraction efficiencies were obtained. The method was linear within the evaluated range (R2 > 0.99) for all elements and no matrix effect was observed. The detection limits of the method were 27, 26, 19, and 28 μg g−1 for F, Cl, Br, and I, respectively. The accuracy was evaluated by a recovery test (ranging from 92 to 108%) and analysis of certified reference materials for apple leaves (NIST 1515) and peach leaves (NIST 1547), which had a good agreement (ranging from 97 to 101%) with the certified values. Comparing the results with those obtained by inductively coupled plasma-mass spectrometry after microwave-induced combustion, no significant difference was found between the results, and the relative standard deviations were lower than 12%. The proposed method proved to be efficient for the determination of halogens in different algae species, showing advantages such as simplicity and low cost, combined to the use of a material from renewable sources (sea sand) as a solid support, contributing to the principles of Green Analytical Chemistry. [Display omitted] • VA-MSPD was proposed for the extraction of halogens from edible seaweed samples. • Determination of F, Cl, Br, and I by IC was carried out. • Sea sand was used as a solid green support in the sample preparation. • Simple, quick, low-cost, and green method is presented. [ABSTRACT FROM AUTHOR]

Abstract: In this study, microwave-induced combustion (MIC) of extra-heavy crude oil is proposed for further chlorine and sulfur determination by inductively coupled plasma optical emission spectrometry (ICP OES). Combustion was carried out under oxygen pressure (20 bar) in quartz vessels using ammonium nitrate (50 µl of 6 mol l−1 solution) as ignition aid. Samples were wrapped with polyethylene film and placed on a quartz holder positioned inside the quartz vessels. The need for an additional reflux step after combustion and the type and concentration of absorbing solution (water, 0.02 to 0.9 mmol l−1 H2O2, 10 to 100 mmol l−1 (NH4)2CO3 or 0.1 to 14 mol l−1 HNO3) were studied. The influence of sample mass, O2 pressure and maximum pressure attained during the combustion process were investigated. Recoveries from 92 to 102% were obtained for Cl and S for all absorbing solutions. For comparison, Cl and S determination was also performed by ion chromatography (IC) using 25 mmol l−1 (NH4)2CO3 as absorbing solution. Using MIC with a reflux step the agreement was better than 95% for certified reference materials of similar composition (crude oil, petroleum coke, coal and residual fuel oil). Microwave-assisted digestion and water extraction in high pressure closed vessels were also evaluated. Using these procedures the maximum recoveries were 30 and 98% for Cl and S, respectively, using microwave-assisted digestion and 70% for Cl and less than 1% for S by water extraction procedure. Limits of detection by ICP OES were 12 and 5 µg g−1 for Cl and S, respectively, and the corresponding values by IC were 1.2 and 8 µg g−1. Using MIC it was possible to digest simultaneously up to eight samples resulting in a solution suitable for the determination of both analytes with a single combustion step. [Copyright &y& Elsevier]