Browsing by Author "Sharma, P.S."

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    Electrochemical sensor for uric acid based on a molecularly imprinted polymer brush grafted to tetraethoxysilane derived sol-gel thin film graphite electrode
    (2009) Patel, A.K.; Sharma, P.S.; Prasad, B.B.
    Determination of uric acid in human serum and urine is useful to provide treatment guidelines to hyperuricemic patients. An electrochemical sensor was developed for selective and quantitative recognition of uric acid by using a preanodised sol-gel coated graphite electrode with a molecularly imprinted polymer brush of poly(melamine-co-chloranil) grafted to its exterior surface. During a preconcentration step at (+ 2.0 V versus saturated calomel electrode), the encapsulated analyte recapture involved hydrophobically induced hydrogen-bondings in outwardly exposed MIP cavities in aqueous environment (pH 7.0), instantly oxidised as dications, and then cathodically stripped off as corresponding lactam responding differential pulse, cathodic stripping voltammetric signal. The uric acid was selectively detected without any cross reactivity in the windows of 14.56-177.42 μg mL- 1 (aqueous medium), 4.78-106.96 μg mL- 1 (blood serum), and 7.81-148.42 μg mL- 1 (urine) indicating detection limits in the range of 3.71-4.10 μg mL- 1 (3σ, RSD = 1.9%). © 2008 Elsevier B.V. All rights reserved.
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    Highly sensitive and selective detection of creatinine by combined use of MISPE and a complementary MIP-sensor
    (2007) Sharma, P.S.; Lakshmi, D.; Prasad, B.B.
    Guanidinoacetate methyltransferase deficiency is a recently discovered inborn defect of creatine biosynthesis which reduces serum creatinine concentrations to as low as 0.58 μg mL-1 (or 0.00058 μg mL -1 after 1,000-fold dilution). To measure ultra trace levels of creatinine in diluted samples, molecularly imprinted solid-phase extraction (MISPE) and molecularly imprinted polymer (MIP) sensor techniques have been found to be inadequate. A combination of these techniques (i.e. MISPE hyphenated with use of an MIP-sensor), reported in this paper, has been found to be highly suitable for direct assay of creatinine in highly diluted human blood serum without complicated pretreatment of the sample. The proposed technique has the potential to enhance the sensitivity of creatinine measurement from μg mL-1 to ng mL-1 in highly dilute aqueous samples in which the concentrations of interfering constituents are reduced to negligible levels. In this work the sensitivity to creatinine was found to be improved compared with that of the MIP-sensor method alone (limit of detection, LOD, 0.00149 μg mL-1). After preconcentration by MISPE and use of the sensor the detection limit for creatinine was as low as 0.00003 μg mL-1 (RSD = 0.94%, S/N = 3; 50-fold preconcentration factor) in aqueous samples. © 2007 Friedr. Vieweg & Sohn Verlag/GWV Fachverlage GmbH.