Screening of seized cocaine samples using electrophoresis microchips with integrated contactless conductivity detection.

This study describes the development of a new analytical method for the separation and detection of cocaine (COC) and its adulterants, or cutting agents, using microchip electrophoresis (ME) devices coupled with capacitively coupled contactless conductivity detection (C4 D). All the experiments were carried out using a glass commercial ME device containing two pairs of integrated sensing electrodes. The running buffer composed of 20 mmol/L amino-2-(hydroxymethyl) propane-1,3-diol and 10 mmol/L 3,4-dimethoxycinnamic acid provided the best separation conditions for COC and its adulterants with baseline resolution (R > 1.6), separation efficiencies ranging from (2.9 ± 0.1) to (3.2 ± 0.2) × 105 plates/m, and estimated LOD values between 40 and 150 µmol/L. The quantification of COC was successfully performed in four samples seized by the Brazilian Federal Police Department and all predicted values agree with values estimated by the reference method. Some other interfering species were detected in the seized samples during the screening procedure on ME-C4 D devices. While lidocaine was detected in sample 3, the presence of levamisole was observed in samples 2 and 4. However, their concentrations were estimated to be below the LOQ. ME-C4 D devices have proved to be quite efficient for the identification and quantification of COC with errors lower than 10% when compared to the data obtained by a reference method. The approach herein reported offers great potential to be used for on-site COC screening in seized samples.

High performance separation of quaternary amines using microchip non-aqueous electrophoresis coupled with contactless conductivity detection.

This study describes the development of an analytical methodology for the separation of quaternary amines using non-aqueous microchip electrophoresis (NAME) coupled with capacitively coupled contactless conductivity detection (C4D). All experiments were performed using a commercial microchip electrophoresis system consisting of a C4D detector, a high-voltage sequencer and a microfluidic platform to assemble a glass microchip with integrated sensing electrodes. The detection parameters were optimized and the best response was reached applying a 700-kHz sinusoidal wave with 14Vpp excitation voltage. The running electrolyte composition was optimized aiming to achieve the best analytical performance. The mixture containing methanol and acetonitrile at the proportion of 90:10 (v:v) as well as sodium deoxycholate provided separations of ten quaternary amines with high efficiency and baseline resolution. The separation efficiencies ranged from 8.7×104 to 3.0×105 plates/m. The proposed methodology provided linear response in the concentration range between 50 and 1000µmol/L and limits of detection between 2 and 27µmol/L. The analytical feasibility of the proposed methodology was tested in the determination of quaternary amines in corrosion inhibitor samples often used for coating oil pipelines. Five quaternary amines (dodecyltrimethylammonium chloride, tetradecyltrimetylammonium bromide, cetyltrimethylammonium bromide, tetraoctylammonium bromide and tetradodecylammonium bromide) were successfully detected at concentration levels from 0.07 to 6.45mol/L. The accuracy of the developed methodology was investigated and the achieved recovery values varied from 85 to 122%. Based on the reported data, NAME-C4D devices exhibited great potential to provide high performance separations of hydrophobic compounds. The developed methodology can be useful for the analysis of species that usually present strong adsorption on the channel inner walls.

Authenticity screening of seized whiskey samples using electrophoresis microchips coupled with contactless conductivity detection.

This report describes for the first time the use of microchip electrophoresis (ME) devices integrated with capacitively coupled contactless conductivity detection (C4 D) to investigate the authenticity of seized whiskey samples, which were probably adulterated by simple dilution with tap water. The proposed microfluidic platform was explored for the monitoring of anionic species (Cl- and F- ) in both original and tampered samples. The best separations were achieved within 70 s using a running buffer composed of lactic acid and histidine (pH = 5.9). ME-C4 D devices were used to analyze samples from three different brands (five samples each). Based on the presence of inorganic anions like Cl- , F- , SO42- and NO2- in different amounts, the authenticity of seized whiskeys was compared to original samples. According to the reported data, the proposed microfluidic platform can be useful to help regulatory authorities in the investigation and monitoring of authenticity of commercialized whiskey beverages.

Eugenia dysenterica DC. (Myrtaceae) exerts chemopreventive effects against hexavalent chromium-induced damage in vitro and in vivo.

CONTEXT: Eugenia dysenterica DC. (Myrtaceae) has been widely used in the folk medicine and it presents phytochemicals constituents associated to antioxidant properties. OBJECTIVE: The objective of this study was to investigate the protective effects of E. dysenterica leaf hydroalcoholic extract (EDE) in vitro and in vivo using AMJ2-C11 cells and Swiss mice exposed to hexavalent chromium [Cr(VI)], respectively. MATERIALS AND METHODS: AMJ2-C11 cells were pretreated with EDE and exposed to Cr(VI) to evaluate cytotoxicity and the pathways involved in the chemopreventive effects of the extract. Mice were daily pretreated with EDE and then exposed to Cr(VI). Survival analysis, histopathological examination and determination of Cr levels in biological tissues were carried out. RESULTS: In vitro studies showed that pretreatment of the AMJ2-C11 cells with EDE protected against the cytotoxicity and oxidative stress induced by Cr(VI). Consequently, the pretreatment with EDE reduced reactive oxygen species and apoptosis triggered by Cr(VI), probably by a marked antioxidant and chelating activities demonstrated by EDE. Regarding in vivo studies, pretreatment for 10 days with EDE increased survival of the mice exposed to Cr(VI). In addition, EDE prevented liver and kidney pathological damages, in parallel with reduction in chromium levels found in these organs and plasma. EDE also showed a marked antioxidant potential associated with the presence of polyphenols, especially flavonoids and tannins, as confirmed by HPLC-PDA. CONCLUSION: The study showed that EDE protects against Cr(VI)-induced damage in vitro and in vivo supporting further studies for the development of therapeutic products applied to prevent the damage induced by toxic metals, especially Cr(VI).

Monitoring of nitrite, nitrate, chloride and sulfate in environmental samples using electrophoresis microchips coupled with contactless conductivity detection.

This report describes the development of an analytical methodology on microchip electrophoresis (ME) devices coupled with capacitively coupled contactless conductivity detection (C(4)D) to monitor inorganic anions in environmental samples. The buffer composition as well as detection operating parameters were optimized to achieve the best separation selectivity and detector sensitivity, respectively. Electrophoretic separations of Cl(-), NO3(-), SO4(2-) and NO2(-) were successfully performed within 60s using a running buffer composed of 30mmol L(-1) latic acid and 15mmol L(-1)l-histidine (His). The best detectability levels were found applying a sinusoidal wave with 1100-kHz-frequency and 60-Vpp amplitude. Quantitative analyzes of inorganic anions were carried out in the presence of Cr2O7(2-) ion as internal standard (IS), which ensured great repeatability in terms of migration times (<1%) and peak areas (6.2-7.6%) for thirty consecutive injections. The analytical performance revealed a linear behavior for concentration ranges between 0-120µmol L(-1) (Cl(-), NO2(-) and NO3(-)) and 0-60µmol L(-1) (SO4(2-)) and limits of detection (LODs) varying from 2.0 to 4.9µmol L(-1). The concentration levels of anionic species were determined in aquarium, river and biofertilizer samples with recovery values between 91% and 105%. The nitrification steps associated with conversion of ammonium to nitrite followed by the conversion of nitrite to nitrate were successfully monitored in a simulated environment without fishes during a period of twelve weeks. Lastly, the monitoring of anionic species was carried out during eight weeks in an aquarium environment containing ten fishes from Danio rerio (Ciprynidae). The recorded data revealed the absence of nitrite and a gradual increase on the ammonium and nitrate concentration levels during eight weeks, thus suggesting the direct conversion of ammonium to nitrate. Based on the data herein reported, the proposed analytical methodology can be used for routine environmental analysis.