A quantitative method for the detection and validation of catalase activity at physiological concentration in human serum, plasma and erythrocytes.

A novel method has been proposed to develop a simple, rapid, sensitive and affordable chromogenic attempt for the quantification of catalase (CAT) activity in blood samples. The method is based on the oxidation of pyrocatechol (PC) to give quinone form which by oxidative coupling with aminyl radical of 4-aminoantipyrine (4-AAP) resulting from H2O2/CAT to produce a pink colored quinone-imine product with λmax = 530 nm in a 100 mmol/L of tris buffer of pH 9.8 at room temperature (30 °C). The linearity of CAT assay was between 0.316 and 10 U/mL. The accuracy ranges for CAT having concentrations of 1.25, 5 and 7.5 µmol/L were 89-105.52, 90-107%, and 91-104.58% respectively. Within-run and between-run precision studies showed CV's of 1.98-3.02% (n = 7) and 2.97-4.40% (n = 7), respectively. The detection and quantification limits of CAT were 0.12 and 0.225 µmol/L, respectively. The Michaelis-Menten constant and maximum velocity of the reaction was Km = 1.052 mM and Vmax = 0.168 µmol/min, respectively. The present method provides a convenient means for investigating the usefulness of CAT measurements in biological sample assessing the potential for free radical-induced pathology.

Ninhydrin-sodium molybdate chromogenic analytical probe for the assay of amino acids and proteins.

A sensitive method has been proposed for the quantification of amino acids and proteins using ninhydrin and sodium molybdate as chromogenic substrates in citrate buffer of pH5.6. A weak molybdate-hydrindantin complex plays the role in the formation of Ruhemann's purple. The linear response for the amino acid, amino acid mixture and Bovine serum albumin is between 0.999 and 66.80µM, 1.52 and 38µM and 5 and 100µg/L, respectively. The molar absorptivity of the individual amino acid by the proposed reaction extends from 0.58×104 to 2.86×104M-1cm-1. The linearity equations for the proposed ninhydrin-molybdate for amino acid mixture is Abs=0.021×Conc (µM)-0.002. The applicability of the proposed method has been justified in food and biological samples in conjunction with Kjeldahl method.

A spectrophotometric assay method for vanadium in biological and environmental samples using 2,4-dinitrophenylhydrazine with imipramine hydrochloride.

A simple, rapid, and sensitive method involving the interaction of 2,4-dinitrophenylhydrazine with imipramine hydrochloride in presence of vanadium (V) in sulfuric acid medium has been proposed for the determination of vanadium. The purple-colored product developed showed an absorption maximum at 560 nm and was stable for 24 h. The working curve was linear over the concentration range of 0.1-2.8 µg ml( - 1), with sensitivity of detection of 0.0124 µg ml( - 1). Molar absorptivity and Sandell's sensitivity were found to be 2.6 × 10(4) l/mol cm and 0.0039 µg cm( - 1), respectively. The accuracy of the proposed method was assessed by Student's t test and variance ratio F test, and the results were on par with the reported method. The method was successfully used in the determination of V in water, human urine, soil, and plant samples, and it was free from interference by various concomitant ions.

Development of a selective and sensitive spectrophotometric method for the trace determination of thallium(III) using 3-methyl-2-benzothiazolinone hydrazone hydrochloride and N-(1-naphthyl)-ethylenediamine dihydrochloride.

A simple, selective, sensitive, and rapid spectrophotometric method has been developed for the determination of thallium(III) using 3-methyl-2-benzothiazolinone hydrazone hydrochloride and N-(1-naphthyl)-ethylenediamine dihydrochloride. The obtained product had an absorption maximum of 590 nm. Beer's law was valid over the concentration range of 0.15-8 microg/mL. The molar absorptivity and Sandell's sensitivity of the colored system were 2.93 x 10(4) L/mol x cm and 0.00723 microg/mL, respectively. The effect of different acids on the sensitivity of the method, interference by foreign substances, the optimum reaction conditions, and other analytical parameters were evaluated. The proposed method has been successfully applied in the analysis of T1(III) in standard reference materials, synthetic mixtures, and water and urine samples. The performance of the proposed method was evaluated in terms of Student's t-test and variance ratio F-test, which indicated the significance of the proposed method over reported methods.