Evaluation of digoxin-boronate ester formation through in-capillary derivatisation-large volume sample stacking-capillary zone electrophoresis.

Determination of digoxin through in-capillary derivatisation based on the formation of o-tolyl- and 2-naphthyl-anionic boronate esters in combination with large volume sample stacking-capillary electrophoresis is proposed. The derivatisation reaction was performed at basic pH values to obtain compounds with a charge and chromophore group during the stacking process. After stacking, the species were separated and detected at 225 nm using p-nitrophenol as an internal standard. Stacking and derivatisation parameters such as pre-concentration time, preconcentration voltage and injection time (relation between the analyte and the derivatisation agent) were evaluated using a Box-Behnken design. Under optimal conditions, the proposed method exhibits a linear range of 1.08-50.00 µM with a limit of detection of 0.36 µM; additionally, adequate repeatability and reproducibility was obtained (%RSD ≤ 5.0%). The methodology was validated by comparing it to an HPLC-UV established methodology and was successfully applied for the determination of digoxin in pharmaceutical tablets and blood serum samples, showing a positive performance for these matrices.

Fluorescence assay for acrylamide determination in fried products based on AgInS2/ZnS quantum dots.

AgInS2/ZnS quantum dots were synthesized via solvothermal aqueous phase method using 3-mercaptopropionic acid as the stabilizer. AgInS2/ZnS quantum dots were employed for acrylamide sensing under two strategies: (1) quenching of the fluorescence signal by the synthesis of polyacrylamide under UV light and (2) use of 2-naphthalenethiol for quenching of the fluorescence signal of quantum dots followed by a recovery of the signal after the addition of acrylamide. Both methodologies display adequate limits of detection, 15.6 and 4.8 µg L-1, respectively. However, the 2-napthalenethiol based method exhibited better precision and selectivity compared to the other methodology. Both methodologies were applied for acrylamide detection in fried snack products and acceptable accuracy was obtained using 2-napthalenethiol method.

Micro flow injection analysis of leucomalachite green in fish muscle using modified henequen fibers as microfluidic channels.

In this work a simple and novel procedure for leucomalachite green determination based on micro flow injection analysis (µFIA) with amperometric detection is presented. The method involves the use of henequen modified fibers as microfluidic channels. The µFIA system proposed offers a simple, rapid, and low-cost alternative for the determination. Capillary and gravitational forces across the modified henequen fibers control the flow rate, eliminating the need for external pumps. This technique requires low reagent consumption and allows portability for in situ measurements. The flow system is described, and the operational variables were studied and optimized using a Taguchi parameters design to increase analytical sensitivity. Under optimal conditions a limit of detection of 1.16 µg kg-1 was achieved with adequate repeatability and reproducibility (expressed as %RSD <5.0%, n = 3, n = 9 respectively) in all cases. The effect of interfering species and the accuracy of the method were also investigated. The proposed methodology was validated and applied to determine LMG in tilapia muscle samples.

Chromium(VI) Removal from Aqueous Solution by Magnetite Coated by a Polymeric Ionic Liquid-Based Adsorbent.

An evaluation of the chromium(VI) adsorption capacity of four magnetite sorbents coated with a polymer phase containing polymethacrylic acid or polyallyl-3-methylimidazolium is presented. Factors that influence the chromium(VI) removal such as solution pH and contact time were investigated in batch experiments and in stirred tank reactor mode. Affinity and rate constants increased with the molar ratio of the imidazolium. The highest adsorption was obtained at pH 2.0 due to the contribution of electrostatic interactions.

Application of an activated carbon-based support for magnetic solid phase extraction followed by spectrophotometric determination of tartrazine in commercial beverages.

A method is presented for magnetic solid phase extraction of tartrazine from nonalcoholic beverages. The method involves the extraction and clean-up by activated carbon covered with magnetite dispersed in the sample, followed by the magnetic isolation and desorption of the analyte by basified methanol. The tartrazine eluted from the magnetic support was determined by spectrophotometry. Under optimal conditions, the linear range of the calibration curve ranges from 3 to 30 mg L(-1), with a limit of detection of 1 mg L(-1). The method was validated by comparing the results with those obtained by HPLC. A precision of <5.0% was obtained in all cases and no significant differences were observed (P < 0.05).