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A very simple, rapid, ultra-sensitive, highly selective and non-extractive spectrofluorimetric method for the determination of N-acetyl-4-aminophenol (paracetamol) at ultra-trace levels has been developed. This method was based on the oxidation of paracetamol in presence of slightly acidic (0.05 – 0.15 M H2SO4) aqueous solution with a prompt oxidizing agent, cerium(IV) for the direct spectrofluorimetric determination of paracetamol and the fluorescent species is an oxidation product of parcetamol, has excitation and emission wavelength at λex = 255 nm and λem = 350 nm, respectively. The fluorescence intensity of oxidation product reaches a constant value (after heating for 5 min at 45 ± 5°C) within 15 min remains stable for over 24 h. Numerous variables influencing the reaction’s conditions e.g. the concentrations of cerium(IV), temperature, effect of acidity, time of the reaction and solvents were cautiously experimented and optimized. Linear calibration graphs were obtained for 10–700μgL-1 of paracetamol, having a detection limit of 2μgL-1; the quantification limit of the reaction system was found to be 10μgL-1; the RSD was 0 – 2 % and the correlation coefficient, R2 = 0.9999. A large excess of over 40 potentially interfering excipients, commonly present in dosage forms were tested in the determination of paracetamol at 100μgL-1 level, do not intervene in the determination process. The developed method was successfully applied to the determination of paracetamol in commercial pharmaceutical formulations and biological fluids. The results of the proposed method for pharmaceuticals and biological analyses were analogous with that of spectrophotometric method and the Official method stated in the British Pharmacopoeia, and was found to be in an excellent agreement. more...

A very simple, ultra-sensitive and highly selective non-extractive spectrophotometric method for the determination of trace amount of zinc using 5,7-dibromo-8-hydroxyquinoline (DBHQ) has been developed. DBHQ reacts in a slightly acidic solution (0.000001-0.000007 M H2S04) with zinc to give a pale-yellow chelate, which has an absorption maximum at 391 nm. The reaction is instantaneous and absorbance remains stable for over 24 hrs. The average molar absorption co-efficient and Sandell's sensitivity were found to be 1.62 x 105 L mol -1 cm -1 and 10 ng cm-2 of Zn, respectively. Linear calibration graphs were obtained for 0.02-4 mg L-1 of Zn having detection limit of 5 µg L-1 and RSD 0 - 2%. The stoichiometric composition of the chelate is 1:2 (Zn : DBHQ). A large excess of over 50 cations, anions and some common complexing agents (such as chloride, azide, tartrate, EDTA, oxalate, SCN- etc) do not interfere in the determination. The method was successfully used in the determination of zinc in several Standard Reference Materials (alloys and steels) as well as in some environmental waters (potable and polluted), biological samples (human blood and urine), soil samples, milk samples, pharmaceutical samples and complex synthetic mixtures.The results of the proposed method for biological samples were comparable with AAS and were found to be in excellent agreement.The method has high precision and accuracy (s = ± 0.01 for 0.5 mg L-1). more...

A very simple, ultra-sensitive, highly selective and non-extractive spectrophotometric method for the determination of trace amounts copper(II) has been developed. Salicylaldehy debenzoyl hydrazone (SAL-BH) has been proposed as a new analytical reagent for the direct non-extractive spectrophotometric determination of copper(II). SAL-BH reacts with copper in a slightly acidic (0.0001-0.005 M H2SO4) in 40% 1,4-dioxane media with copper(II) to give a highly absorbent greenish yellow chelate with a molar ratio 1:1(CuII: SAL-BH) The reaction is instantaneous and the maximum absorption was obtained at 404 nm and remains stable for 72 h. The average molar absorptivity and Sandell’s sensitivity were found to be 1.4×105 L mol-1 cm-1 and 5.0 ng cm-2 of copper(II), respectively. Linear calibration graphs were obtained for 0.01 – 18 mg L-1 of CuII. The detection limit and quantification limit of the reaction system were found to be 1 ng mL-1 and 10 µg L-1, respectively. A large excess of over 50 cations, anions and complexing agents (e.g., tartrate, oxalate, citrate, phosphate, thiocyanate etc.) do not interfere in the determination. The method is highly selective for copper and was successfully used for the determination of copper in several standard reference materials (steels and alloys) as well as in some environmental waters (portable and polluted), biological (human blood and urine), food and soil samples and solutions containing both copper(I) and copper(II) as well as some complex synthetic mixtures. The results of the proposed method for biological and food samples were comparable with AAS and were found to be in good agreement. The method has high precision and accuracy (s = ± 0.01 for 0.5 mg L-1). more...

Photoelectrochemcal sensors were developed for the rapid detection of oxidative DNA damage induced by titanium dioxide and polystyrene nanoparticles. Each sensor is a multilayer film prepared on a tin oxide nanoparticle electrode using layer- by-layer self assembly and is composed of separate layer of a photoelectrochemical indicator, DNA. The organic compound and heavy metals represent genotoxic chemicals leading two major damaging mechanisms, DNA adduct formation and DNA oxidation. The DNA damage is detected by monitoring the change of photocurrent of the indicator. In one sensor configuration, a DNA intercalator, Ru(bpy)2 (dppz)2+ [bpy=2, 2′ -bipyridine, dppz=dipyrido( 3, 2-a: 2′ 3′-c) phenazine], was employed as the photoelectrochemical indicator. The damaged DNA on the sensor bound lesser Ru(bpy)2 (dppz)2+ than the intact DNA, resulting in a drop in photocurrent. In another configuration, ruthenium tris(bipyridine) was used as the indicator and was immobilized on the electrode underneath the DNA layer. After oxidative damage, the DNA bases became more accessible to photoelectrochemical oxidation than the intact DNA, producing a rise in photocurrent. Both sensors displayed substantial photocurrent change after incubation in titanium dioxide / polystyrene solution in a time – dependent manner. According to the data, damage of the DNA film was completed in 1h in titanium dioxide / polystyrene solution. In addition, the titanium dioxide induced much more sever damage than polysterene. The results were verified independently by gel electrophoresis and UV-Vis absorbance experiments. The photoelectrochemical reaction can be employed as a new and inexpensive screening tool for the rapid assessment of the genotoxicity of existing and new chemicals. more...

A very simple, selective and highly sensitive capillary electrophoretic method for the simultaneous determination of chromium(III) and vanadium(V) with Mo(VI)-P(V) reagent has been developed. A Mo(VI)-P(V) reagent reacted with a mixture of trace amounts of chromium(III) and vanadium(V) to form the stable heteropolyanions in 0.1M acetate buffer (pH 2.0) at room temperature(25±5 0C). Both anionic forms of chromium(III) and vanadium(V) can be determined simultaneously by capillary electrophoresis with direct UV detection at 254nm. The pre-column complex formation reaction is instantaneous and absorbance remains stable for 24h. Linear calibration curves were obtained in the concentration ranges of 0.06 – 60 mgL-1 and 0.05 – 80 mgL-1 of Cr(III) and V(V), respectively; the detection limits were 6.0 µg L-1 and 5.0 µg L-1 , respectively. The influence of several experimental parameters on both sensitivity and efficiency was investigated. The interference from over 50 cations, anions and complexing agents has been discussed at 1 mgL-1 of Cr and V, respectively. The unique selectivity and sensitivity of the method allowed its direct application to the determination of Cr and V in complex matrices of certified reference materials and synthetic seawater.. The developed was also used successfully in the determination of chromium and vanadium in environmental waters (tap and lake). The method has high precision and accuracy (s =±0.02 for 0.5 mg L-1 ). more...

A very simple, ultra-sensitive and fairly selective non-extractive spectrophotometric method for the determination of trace amounts of lead with 2,5-dimercapto-1,3,4-thiadiazole (DMTD) has been developed. DMTD reacts in slightly acidic (0.0015-0.01 M HCl) aquatic media with lead(II) to give a greenish-yellow chelate, which has an absorption maximum at 375 nm. The reaction is instantaneous and absorbance remains stable for 24 h. The average molar absorption coefficient and Sandell's sensitivity were found to be 4.93x10(4) lmol(-1)cm(-1) and 15 ngcm(-2) of Pb, respectively. Linear calibration graphs were obtained for 0.1-40 mugml(-1) of Pb; the stoichiometric composition of the chelate is 1:2 (Pb-DMTD). The interference from over 50 cations, anions and complexing agents has been studied at 1 mugml(-1) of Pb. The method developed was used successfully in the determination of lead in several standard reference materials (alloys and steels), environmental waters (potable and polluted), biological samples (human blood and urine), soil samples, solutions containing both lead(II) and lead(IV) and complex synthetic mixtures. The method has high precision and accuracy (S=+/-0.01 for 0.5 mugml(-1)). more...