Applicability and Limitations of a Capillary-LC Column-Switching System Using Hybrid Graphene-Based Stationary Phases.

Graphene oxide sheets fixed over silica particles (SiGO) and their modification functionalized with C18 and endcapped (SiGO-C18ec) have been reported as sorbents for extraction and analytical columns in LC. In this study, a SiGO column was selected as the extraction column and a SiGO-C18ec as the analytical column to study the applicability and limitations of a column-switching system composed exclusively of columns packed with graphene-based sorbents. Pyriproxyfen and abamectin B1a were selected as the analytes, and orange-flavored carbonated soft drinks as the matrix. The proposed system could be successfully applied to the pyriproxyfen analysis in a concentration range between 0.5 to 25 µg/mL presenting a linearity of R2 = 0.9931 and an intra-day and inter-day accuracy of 82.2-111.4% (RSD < 13.3%) and 95.5-99.8% (RSD < 12.7%), respectively. Furthermore, the matrix composition affected the area observed for the pyriproxyfen: the higher the concentration of orange juice in the soft drink, the higher the pyriproxyfen the signal observed. Additionally, the SiGO extraction column presented a life use of 120 injections for this matrix. In contrast, the proposed system could not apply to the analysis of abamectin B1a, and the SiGO-C18ec analytical column presented significant tailing compared to a similar approach with a C18 analytical column.

Infrared thermal imaging combined with paper microzone plates and natural reagent extracts for simple, fast, and green enthalpimetric analysis.

Paper microzone plates and thermal infrared enthalpimetry (TIE) were combined with potato juice as natural reagent extract to perform the determination of hydrogen peroxide in pharmaceutical, bleaching, and toiletry products. A multichannel pipette was used for reagent addition simultaneously in multiple zones of paper devices, and the temperature rise was determined using an infrared camera. In order to provide suitable measurements, some parameters were optimized such as pH, volume of reagents, and stability of the extract. Results for the hydrogen peroxide were compared with those obtained using methods from official compendia (United States Pharmacopeia and ASTM D2180-17), with agreements ranging from 96 to 103%. The green analytical procedure index was used to compare the greenness of the proposed method with official ones, with clear advantages for TIE. Only microliters of samples and natural reagent extracts were required for analysis, and it was found that waste generation could be greatly reduced. After analysis, the paper device could be directly disposed since the final products of the reaction were O2 and water. According to these features, the proposed method could be considered a promising alternative to routine analysis in agreement with green analytical chemistry principles.

A simple and rapid direct injection method for the determination of glyphosate and AMPA in environmental water samples.

Glyphosate is currently the most widely used herbicide in the world, yet screening of environmental waters for this chemical is limited by the need for specialized derivatization and measurement methods that can be tedious and time-consuming. In this work, we present a novel method for the detection and quantification at trace levels of glyphosate and aminomethylphosphonic acid (AMPA) in environmental water samples. The detection and quantification of the analytes was performed by liquid chromatography (LC) coupled with tandem mass spectrometry (MS/MS). Chromatographic separation was achieved with an ion-exchange column and a pH-gradient elution of a solution of ammonium hydroxide and ammonium acetate. The limit of detection for glyphosate and AMPA was 0.25 µg L-1 and the limit of quantification was 0.5 µg L-1with a 20-µL injection. The method was used to investigate the levels of glyphosate and AMPA in surface water samples from the Yarra River catchment area and urban constructed stormwater wetlands. The results indicate that at the time of sampling, no glyphosate or AMPA was present in the samples from the Yarra River catchment area (n = 10). However, glyphosate was detected above the limit of quantification in 33% of the wetland samples (n = 12), with concentrations ranging from 1.95 to 2.96 µg L-1. Similarly, AMPA was quantified in 83% of the wetland samples, with concentrations ranging from 0.55 to 2.42 µg L-1. To our knowledge, this is the first report of a pH-gradient LC-MS/MS method for glyphosate and AMPA analysis at ultratrace levels, with minimal sample processing, avoiding costly, time-consuming derivatization and preconcentration steps. Graphical abstract ᅟ.

Quantificação de benzeno, tolueno, etilbenzeno e xilenos no ar de ambientes internos / Quantification of benzene, toluene, ethylbenzene and xylenes in the air of indoor environments

RESUMO A poluição do ar não está restrita a ambientes abertos, podendo existir elevadas concentrações de poluentes do ar derivados do petróleo, como o benzeno, tolueno, etilbenzeno e xilenos (BTEX), em ambientes internos. Os BTEX, mesmo quando presentes em baixas concentrações, na ordem de parte por bilhão (ppb), causam problemas à saúde humana. O objetivo deste trabalho foi aplicar uma técnica de quantificação dos BTEX, no nível de ppb, em apenas oito horas de amostragem em um ambiente interno. Para tal fim, foram usados tubos amostradores passivos associados a análise por dessorção térmica, cromatografia gasosa e espectrometria de massas. O método de calibração desse sistema analítico também foi apresentado. O uso dessa metodologia permitiu quantificar os BTEX em um laboratório de pesquisa de motores de combustão, em concentrações de 4,64, 7,87, 10,47 e 21,36 ppb respectivamente. Esses resultados estão próximos da faixa encontrada em ambientes internos por outros estudos no Brasil. A avaliação dos BTEX no laboratório de combustão, além de levar apenas 16 horas, somando a amostragem e análise das amostras, confirmou a sensibilidade da metodologia usada.

ABSTRACT Air pollution is not restricted to open air areas. High concentrations of petroleum-based air pollutants may occur, such as benzene, toluene, ethylbenzene and xylenes (BTEX), in indoor environments. The BTEX, even in low concentrations, of the order of parts per billion (ppb), cause human health problems. The objective of this work was to apply a technique of measurement of BTEX, at ppb level, using only eight hours of sampling in an indoor environment. To this end, passive tube samplers were used associated with analysis by thermal desorption, gas chromatography and mass spectrometry. The calibration method applied to this analytical system was also presented. The use of this method allowed the quantification of BTEX in a combustion engines research laboratory, at concentrations of 4.64, 7.87, 10.47 and 21.36 ppb, respectively. These results are close to the range found by other indoor studies in Brazil. The evaluation of BTEX in the combustion laboratory, besides it only takes 16 hours, considering the sampling and the analysis procedures, confirmed the sensitivity of the methodology used.

Ultrafast gas chromatography method with direct injection for the quantitative determination of benzene, toluene, ethylbenzene, and xylenes in commercial gasoline.

Benzene, toluene, ethylbenzene, and xylenes are some of the most hazardous constituents found in commercial gasoline samples; therefore, these components must be monitored to avoid toxicological problems. We propose a new routine method of ultrafast gas chromatography coupled to flame ionization detection for the direct determination of benzene, toluene, ethylbenzene, and xylenes in commercial gasoline. This method is based on external standard calibration to quantify each compound, including the validation step of the study of linearity, detection and quantification limits, precision, and accuracy. The time of analysis was less than 3.2 min, with quantitative statements regarding the separation and quantification of all compounds in commercial gasoline samples. Ultrafast gas chromatography is a promising alternative method to official analytical techniques. Government laboratories could consider using this method for quality control.

Proanthocyanidin Characterization and Bioactivity of Extracts from Different Parts of Uncaria tomentosa L. (Cat's Claw).

Apart from alkaloids, bioactive properties of Uncaria tomentosa L. have been attributed to its phenolic constituents. Although there are some reports concerning low-molecular-weight polyphenols in U. tomentosa, its polymeric phenolic composition has been scarcely studied. In this study, phenolic-rich extracts from leaves, stems, bark and wood (n = 14) of Uncaria tomentosa plants from several regions of Costa Rica were obtained and analysed in respect to their proanthocyanidin profile determined by a quadrupole-time-of-flight analyser (ESI-QTOF MS). Main structural characteristics found for U. tomentosa proanthocyanidins were: (a) monomer composition, including pure procyanidins (only composed of (epi)catechin units) and propelargonidins (only composed of (epi)afzelechin units) as well as mixed proanthocyanidins; and (b) degree of polymerization, from 3 up to 11 units. In addition, U. tomentosa phenolic extracts were found to exhibit reasonable antioxidant capacity (ORAC (Oxygen Radical Absorbance Capacity) values between 1.5 and 18.8 mmol TE/g) and antimicrobial activity against potential respiratory pathogens (minimum IC50 of 133 µg/mL). There were also found to be particularly cytotoxic to gastric adenocarcinoma AGS and colon adenocarcinoma SW620 cell lines. The results state the particularities of U. tomentosa proanthocyanidins and suggest the potential value of these extracts with prospective use as functional ingredients.

Ochratoxins determination in beers by direct injection of the sample using a IS-anionic column chromatography / Determinação de ocratoxinas em cervejas, por injeção direta da amostra empregando uma coluna cromatografica IS-aniônica

Ochratoxin A is nephrotoxic and has been found in corn, soy, wheat, barley, rice, sorghum and peanut samples. Brazilians consume in average 49 liters of beer yearly, barley being the main raw material, besides maize and rice in a second level. The determination of the ochratoxins A and B in alcoholic beverages require clean-up or immunoaffinity columns. A new analytical method by direct injection of the sample of beer, using liquid chromatography of high efficiency, with a IS-anionic chromatographic column (Internal Surface Reverse Phase) was developed. The considered method presented a recovery that varied from 78.5 to 92.1% for the levels of ochratoxin A in the range of 0.25 to 4.00µg.L-1; and 76.5 to 93.1% for the ochratoxin B at the level of 1.25 to 20.00µg.L-1. The limits of detection were 0.15 and 0.35µg.L-1 and the limits of quantification 0.25 and 0.60µg.L-1 for ochratoxins A and B, respectively. In a total of 42 samples of beers commercialized in Bauru and region, 2.4% of the samples of national beers and 11,1% of the imported ones were contaminated with ochratoxin A above the of quantification, being the level detected between 0.32 and 0.80µg.L-1. ochratoxin B was detected in only 2.4% of national beer samples at the level of 0.78µg.L-1.

A ocratoxina A é nefrotóxica e tem sido encontrada em milho, soja, trigo, cevada, arroz e amendoim. O brasileiro consome em média 49 litros de cerveja por ano, sendo que a matéria-prima principal é a cevada, além de milho e o arroz. A determinação das ocratoxinas A e B em bebidas requerem o clean up ou colunas de imunoafinidade. Um método analítico, por injeção direta da amostra, empregando cromatografia líquida de alta eficiência, com uma coluna cromatográfica IS-aniônica (Internal Surface Reverse Phase) foi desenvolvido. A recuperação do método variou de 78,5 a 92,1% para os níveis de ocratoxina A na faixa de 0,25 a 4,00µg.L-1; e de 76,5 a 93,1% para a ocratoxina B na faixa de 1,25 a 20,00µg.L-1; limites de detecção de 0,15 e 0,35µg.L-1 para ocratoxina A e B, e os limites de quantificação 0,25 e 0,60µg.L-1, respectivamente. Num total de 42 amostras de cervejas comercializadas em Bauru e região 2,4 % das amostras de cervejas nacionais, e 11,1 % das cervejas importadas estavam contaminadas com ocratoxina A entre 0,32 e 0,80µg.L-1. Quanto a ocratoxina B, foi encontrada apenas em 2,4% das amostras de cervejas nacionais, no nível de 0,78µg.L-1.