The development and application of a new simultaneous injection- effective mixing flow analysis (SIEMA) is described. The manifold is based on one syringe pump with a two-way solenoid valve, a set of holding coils and three-way solenoid valves, two multiport connectors, a mixing coil and a detector. The system is compact and is controlled by a laptop computer. Some analytical features of SIEMA are compared with other flow-based systems in terms of mixing efficiency, reagent consumption and sample throughput. Applications of the SIEMA system are demonstrated for environmental and clinical analysis.
This mini-review introduces electrochemical property and analytical applications of the track-etched microporous membrane electrodes. The electrodes were prepared by using a track-etched microporous membrane filter as a template which has a porous structure. The coating of platinum or gold was produced by sputter deposition onto both sides of the membrane filters. The electrode enables efficient electrolysis under a flow condition when the sample solution flows through the cylindrical pores of the electrode. Efficiency of electrolysis becomes remarkably higher by using the smaller pore size. This property would be attributed to the limitation of growth of the diffusion layer at the entrances of pores. Three-electrode and four-electrode system was fabricated by alternately piling up the electrodes and the membrane filters. Insertion of a membrane filter as a spacer between the electrodes avoids short-circuits and keeps a completely uniform distance between the electrodes. An immobilized enzyme reactor is also able to be mounted in the proposed electrode system. The simplicity and flexibility of arrangement of the electrodes as well as high efficiency of electrolysis is the greatest feature of the track-etched microporous membrane electrodes.
The simultaneous determination of As(III) and As(V) in aqueous solution based on the acidic permanganate and luminol chemiluminescence (CL) detection systems have been applied to a split microfluidics flow injection (µFI) with dual-channel manifolds at rapid sampling rate. The µFI-CL system consisted of two halves of micro-conduit platforms, which ran on a simple device made from small pieces of the laser engraved polymethylmethacrylate (PMMA) and polydimethylsiloxane (PDMS). The specific CL reaction for As(III) was produced by the oxidation of acidic potassium permanganate in the presence of sodium hexametaphosphate media, while the CL reaction for As(V) was generated based on the oxidation of luminol with a vanadomolybdoarsenate heteropoly acid (AsVMo-HPA) complex in an alkaline solution. The µFI method involved the injection of the mixed standard solution into an acid carrier stream where it was then splitted and merged with the reagent solutions of each reaction systems on a spiral-designed microfluidic platform. The solution mixtures were passed through each spiral flow channel, where the CL intensity of both resulting reaction mixtures were measured with two photomultiplier tubes. Linear calibratons for As(III) and As(V) were established over the concentration ranges of 20-60 µg L-1. The limits of detection (signal-to-noise ratio of 3) of As(III) and As(V) were found to be 4 µg L-1 and the limits of quantification (signal-to-noise ratio of 10) were found to be 10 µg L-1, respectively. The proposed procedure was successfully applied for the determination of As(III) and As(V) in ground water samples.
A sequential injection analysis (SIA) system with spectrophotometric detection was developed as an alternative method for estimating the concentration of lipid hydroperoxides, which are the primary products of the lipid peroxidation process. The lipid hydroperoxide quantification was based on a ferric thiocyanate method. Benzoyl peroxide was used to produce a standard calibration curve for the estimating the lipid hydroperoxide concentrations. The linear range was up to 0.5 mmol/L, for benzoyl peroxide standard, and the limit of detection (3S/N) was 0.015 mmol/L. The relative standard deviation, at 0.3 mmol/L, was 1.3% for 11 injections, and the recoveries were found to be in the range of 97.2–99.5%. The lipid hydroperoxide concentrations in eight edible oils determined using the proposed SIA system were significantly correlated with peroxide values obtained using a conventional American Oil Chemists’ Society’s method (r = 0.987, n = 8, p < 0.01).