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Sensitive determination of chromium (VI) in paint samples using a membrane optode coupled to a multisyringe flow injection system.

Universidad Autónoma de Nuevo León, UANL, Facultad de Ciencias Químicas, Cd. Universitaria, San Nicolás de los Garza, Nuevo León, C.P. 66451, Mexico.
Talanta (Impact Factor: 3.5). 09/2012; 99:730-6. DOI: 10.1016/j.talanta.2012.07.012
Source: PubMed

ABSTRACT In this work, the potential of a membrane optode coupled to a multisyringe flow injection system (MSFIA) was assessed for determining the Cr(VI) concentration in paint samples. The detection is based on the color obtained from the reaction of Cr(VI) with 1,5-diphenylcarbazide in the presence of sulfuric acid (H(2)SO(4)). The redox product was immobilized on a poly(styrene-divinylbenzene) (SDB-XC) membrane optode. The analyte in the sample was then directly quantified at the surface of the disk by measuring the intensity of reflected incident light using a bifurcated optical fiber at 540nm. Experimental parameters (concentration of reagents, sample volume, flow rate of sample solutions, eluent concentration, and effect of diverse ions) were studied in detail. The overall time required for the complete procedure was 4min and only required 0.2mL of the sample volume. The dynamic working response of Cr(VI) was found within the concentration range of 2.4-1000μgL(-1) with a limit of detection (LOD) of 0.7μgL(-1), while the relative standard deviation (RSD) for 400μgL(-1) Cr(VI) was lower than 2% (n=6). This developed method was used to determine Cr(VI) concentrations in the paint samples, for which an alkaline extraction procedure was proposed. The extraction procedure was based on the use of a 7.5% Na(2)CO(3)/5% NaOH solution at 90°C for 30min. Under optimal conditions, the recoveries ranged from 99% to 101%. The complete method was validated using a certified reference material (ERA-QC540, soil sample) and by comparing the results with those obtained using atomic absorption spectrometry (AAS).

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    ABSTRACT: A fully automated method for the determination of chromate is described. It is based on the selective reaction of Cr(VI) with diphenylcarbazide in acidic media to form a colored complex of Cr(III) with the oxidation product diphenylcarbazone. The reaction was performed within the syringe of an automatic burette containing a magnetic stirrer for homogenization of the sample and the required reagents. In-syringe stirring was made possible using a specially designed driving device placed around the syringe barrel to achieve a rotating magnetic field in the syringe, forcing the stirrer to spin. In a second step, the reaction mixture in the syringe was neutralized to allow in-syringe magnetic-stirring-assisted dispersive liquid-liquid microextraction of the complex into 125 μL of n-hexanol. After phase separation by droplet flotation over 30 s, the organic phase was propelled into a coupled spectrophotometric detection cell. The entire multistep procedure including in-system standard preparation was done within 270 s. The method was used for the analysis of natural waters, achieving average analyte recovery of 103 %, a limit of detection of 0.26 μg L(-1), and a repeatability of less than 4 % relative standard deviation.
    Analytical and Bioanalytical Chemistry 06/2013; · 3.66 Impact Factor

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May 22, 2014

Laura Hinojosa Reyes