Determination of tartaric acid in wines by FIA with tubular tartrate-selective electrodes

Improvisation of a spectrophotometric method to quantify hydroxycitric acid

Existing spectrophotometric method to quantify hydroxycitric acid (HCA), although is specific and sensitive; finds limited use owing to poor stability of HCA-metavanadate complex. Present study describes improvisation of this method with respect to source of HCA standard and assay parameters. Assay system consisting of HCA and metavanadate reagent was modified to include 1 M NaOH to neutralize excess acidity. Resulting complex showed λ_max at 485 nm, obeying Beer-Lambert's law within concentration range of 33-677 μg/ml, with linear calibration curve showing a good coefficient of determination (R² = 0.998). Moreover, HCA-metavanadate complex showed enhanced stability retaining up to 70% absorbance even after 60 min of its formation. Similar consistency in scaled-down assay system renders the method suitable for high-throughput screening of HCA-producing microbes. Of the tested metabolites and media components, only tartrate interfered with the spectrophotometric estimation of HCA; a correction factor to eliminate which was also established. Accordingly measured HCA level in the culture supernatant of a bacterial isolate IT6 was comparable to that determined using the standardized HPLC method. The proposed procedure therefore is a convenient, sensitive, accurate and high-throughput method suitable for primary screening of HCA producing microbes; the only ecofriendly alternative source of optically pure HCA.

Flow injection potentiometric determination of chlorpromazine

New chlorpromazine selective electrodes with a tubular arrangement and no internal reference solution are proposed. Selective membranes are of poly(vinyl chloride) (PVC) with the tetraphenylborate.chlorpromazine (TPB.CPZ) ion-exchanger dissolved in o-nitrophenyl octyl ether (oNPOE). Analytical features of the electrodes were evaluated on a single-channel flow assembly having 500 microl injection volumes and flow-rates of 4.5 ml min(-1). For a carrier solution of 3.3 x 10(-3)M in sodium sulphate, Nernstian response was observed over the concentration range 1.0 x 10(-5) to 1.0 x 10(-2)M. Average slopes were about 59 mV decade(-1) and squared correlation coefficients were >0.9984. Slight hiper-Nernstian behaviour was observed in buffer solutions of 4.4 pH; average slopes were of 62.06 mV decade(-1). The electrode displayed a good selectivity for CPZ, with respect to, several foreign inorganic and organic species. The selective electrodes were successfully applied to the analysis of pure solutions and pharmaceutical preparations. Proposed method allows the analysis of 84 samples h(-1), producing wastewaters of low toxicity. The proposed method offers the advantage of simplicity, accuracy, applicability to coloured and turbid samples, and automation feasibility.