An electrochemical assay for the determination of Se (IV) in a sequential injection lab-on-valve system

College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, China.
Analytica chimica acta (Impact Factor: 4.31). 10/2009; 649(1):75-9. DOI: 10.1016/j.aca.2009.06.055
Source: PubMed

ABSTRACT A sequential injection lab-on-valve (LOV) unit, integrating a miniaturized electrochemical flow cell (EFC), has been constructed for the determination of trace amounts of Se (IV) by employing cathodic stripping voltammetry (CSV) technique. The procedure is carried out on a mercury film coated glassy carbon electrode. The analyte solution and electrolyte solution were continuously aspirated and merged in the holding coil (HC) by using a single syringe pump, which were afterwards pushed into the EFC, where the peak current was generated during the subsequent deposition/stripping procedure and measured as the basis of quantification. Assay parameters were optimized in order to achieve the best analytical performance, including mercury film preparation, supporting electrolyte composition, deposition potential and deposition time, and flow variables in the LOV. By loading a sample volume of 500 microL, a linear calibration graph was derived within 1-600 microg L(-1), and a detection limit (3b) of 0.11 microgL(-1) was achieved along with a sampling frequency of 20 h(-1). By integrating the EFC into the LOV unit, the assembling system not only minimized the sample/reagent consumption and waste generation, but also enhanced the sampling frequency. The work itself extended the applications of electrochemical detection techniques and provided a good platform for Se (IV) electrochemical analysis.

  • [Show abstract] [Hide abstract]
    ABSTRACT: In this work, a novel chemically modified electrode is constructed based on metal-organic frameworks and β-cyclodextrin (Cu3(BTC)2/β-CD, BTC = benzene-1,3,5-tricarboxylate) composite material. The electrode was used for simultaneous determination of guanine and adenine in a sequential injection lab-on-valve format and exhibited sensitive responses to guanine and adenine oxidation due to the π-π stacking interaction of Cu3(BTC)2 and the inclusion behavior of β-CD. The analytical performance was assessed with respect to the supporting electrolyte and its pH, accumulation time and accumulation potential, and the fluid flow rates. Under optimal conditions, linear calibration ranges for both guanine and adenine were from 1.0 × 10(-7) to 1.0 × 10(-5) mol L(-1), and detection limits (S/N = 3) were found to be 5.2 × 10(-8) and 2.8 × 10(-8) mol L(-1), respectively. The proposed sensor showed advantages of high sensitivity, simple sample preparation protocol, enhanced throughput and good reproducibility. Finally, the practical application of the proposed sensor has been performed for the determination of guanine and adenine in real samples with satisfactory results.
    The Analyst 10/2014; 139(23). DOI:10.1039/c4an00901k · 3.91 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: An approach for the immobilization of a chromogenic reagent on solid phase micro-beads is performed via a sulfonation reaction. The product as an optical sensor is applied in lab-on-valve bead injection spectroscopy. The benzene ring structure exists in various chromogenic reagents, which facilitates the introduction of a sulfonic acid group via sulfonation. Chromogenic reagents ranging from neutral to anionic can be immobilized on anion exchanger micro-beads. As a model of application, micro-beads of Sephadex QAE A-25 loaded with the chromogenic reagent 1-(2-pyridylazo)-2-naphthol-sulfonic acid (PAN-S) are employed for the determination of trace cobalt by lab-on-valve bead injection spectroscopy. The characteristics of the micro-beads and some important parameters governing the performance of the method are investigated. With a sample volume of 1.0 mL, a detection limit of 8 μg L−1 and a linear range of 20–500 μg L−1 are obtained for cobalt, along with a RSD value of 2.8% (at the 200 μg L−1 level). The accuracy and practical applicability of the present method are validated by analysing a certified reference material of soil GBW07404, vitamin B12 injection and mecobalamin tablets, and further demonstrated by spiking recovery of cobalt in two water samples.
    Analytical methods 05/2012; 4(6):1718-1724. DOI:10.1039/C2AY25159K · 1.94 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A precise, accurate, and reliable flow-batch spectrophotometric method for the determination of selenium (IV) was developed using o-phenylenediamine as a reagent with a sequential injection monosegmented flow system incorporating a simple heating unit. The reaction zones of selenium(IV) and o-phenylenediamine were mixed and heated in a chamber at 62°C for 5 minutes. The piaselanol complexes were then detected at a maximum absorption wavelength of 335 nm. In-line single standard calibration and standard addition procedures were developed employing the monosegmented flow technique. Under the optimized conditions, a linear calibration graph in a range of 0.1–4.0 mg L−1 selenium (IV) was obtained with limits of detection and quantitation of 0.01 and 0.1 mg L−1, respectively. Relative standard deviations were 2% [for both 0.1 and 0.5 mg L−1 selenium (IV) (n = 11)]. A sample throughput of 2 h−1 using four standard addition levels was achieved. The developed system was successfully applied to raw selenium-enriched yeast samples. The analyses performed by the developed method agreed well with those obtained from a standard inductively coupled plasma mass spectrometry method.
    Analytical Letters 07/2013; 46(11). DOI:10.1080/00032719.2013.775652 · 0.98 Impact Factor