Humaira Khan

A simple spectrophotometric method for the determination of trace level lead in biological samples in the presence of aqueous micellar solutions

A very simple, ultra-sensitive and fairly selective new spectrophotometric method has been developed for the rapid determination of lead(II) at ultra-trace level using 1,5-diphenylthiocarbazone (dithizone) in presence of aqueous micellar solutions. The proposed method enabled the determination of lead down to µg l−1 in human blood and urine in aqueous media without resource of any “clean-up” step. The most remarkable point of this method is that the presence of micellar system avoids the previous steps of solvent extraction and reduces the cost, toxicity while enhancing the sensitivity, selectivity and the molar absorptivity. The complex formation of lead in blood with dithizone was completed within a minute at room temperature and the absorbance remains stable for 24 h. The average molar absorption coefficient and Sandells sensitivity were found to be 3.99×105 l mol−1 cm−1 and 30 ng cm−2 of Pb, respectively. Linear calibration graphs were obtained for 0.06–60 mg l−1 of PbII; the stoichiometric composition of the chelate is 1:2 (Pb:dithizone). The interference from over 60 cations, anions and complexing agents has been studied at 1 mg l−1 of PbII. The method was successfully used in the determination of lead in several biological samples (human blood and urine and bovine liver), solution containing both lead(II) and lead(IV) and complex synthetic mixtures. The results of biological analyses by the spectrophotometric method were in excellent agreement with those obtained by AAS. The results of lead concentration in biological samples were varied with age, sex and place which have been discussed.

On-line preconcentration and determination of ultra trace amounts of mercury using surfactant coated alumina modified by dithizone with cold vapor atomic absorption spectrometry

The potential of an inexpensive dithizone immobilized on ammonium lauryl sulfate alumina adsorbent to separate and preconcentrate traces of mercury from vegetables and ground water has been evaluated. A cartridge filled with 100 mg of adsorbent was incorporated to an on-line vapor generation accessory system. Traces of mercury in sample solutions were pumped through the cartridges for 2 min (flow rate of 5 mL min−1) and then eluted from the cartridges with 1 M hydrochloric acid for 1 min at a flow rate of 1 mL min−1. At the same time that mercury is eluted from the cartridges, the eluate is mixed with a 0.02% (m/v) sodium borohydride solution and the mercury cold vapor is swept through the atomization cell with a nitrogen flow of 50 mL min−1. The overall procedure (mercury separation–preconcentration and mercury cold vapor generation–atomization) is completed in around 3 min. The developed method achieves an enrichment factor of 125 with a limit of detection of 0.12 ng mL−1. The repeatability and the accuracy of the overall procedure were successfully assessed.

Online Preconcentration Using Surfactant Coated Alumina Modified with 1,5-Diphenylthiocarbazone and Determination of Cadmium in Environmental Samples by Flame Atomic Absorption Spectrometry

A rapid and sensitive method for the determination of trace levels of cadmium in cigarettes, soil, and blood samples by flame atomic absorption spectrometry (FAAS) has been developed. It is based on the online sorption of Cd(II) ions on a minicolumn packed by sodium dodecyl sulfate–coated alumina modified with dithizone. The optimum experimental parameters for the adsorption and desorption of cadmium were investigated. The recovery obtained was found to be 96% with preconcentration factor of 150. The calibration curve was linear between 50–600 µg/L Cd with a detection limit of 3 µg/L, sample frequency of 30 h−1 and reuse of column for 10 times without loss of sensitivity. The accuracy of the method was confirmed by applying the standard addition method and quantitative recoveries (95–99%) were obtained.

Determination of cadmium and zinc in vegetables with online FAAS after simultaneous pre-concentration with 1,5-diphenylthiocarbazone immobilised on naphthalene.

The concentration of cadmium and zinc in vegetables was determined by using an online flame atomic absorption spectrophotometer after simultaneous pre-concentration based on the complexation of Cd and Zn with 1,5-diphenylthiocarbazone immobilised on naphthalene. The effect of pH, sample flow rate and amount of 1,5-diphenylthiocarbazone on adsorption was investigated. After pre-concentration, Cd and Zn were eluted from the sorbent with hydrochloric acid. A pre-concentration factor of 20 and 33 was achieved for Cd and Zn, respectively. The calibration curve was linear in the range of 0.2–1 µg ml−1 for Cd and Zn. The regression coefficients for the lines were 0.9914 and 0.9989 for Cd and Zn, respectively. The detection limits were calculated as three times the standard deviation of nine replicates of blanks: 0.00123 µg ml−1 for Cd and 0.00176 µg ml−1 for Zn.

A Simple and Selective Spectrophotometric Method for the Determination of Trace Gold in Real, Environmental, Biological, Geological and Soil Samples Using Bis (Salicylaldehyde) Orthophenylenediamine

A simple high sensitive, selective, and rapid spectrophotometric method for the determination of trace gold based on the rapid reaction of gold(III) with bis(salicylaldehyde)orthophenylenediamine (BSOPD) in aqueous and micellar media has been developed. BSOPD reacts with gold(III) in slightly acidic solution to form a 1:1 brownish-yellow complex, which has an maximum absorption peak at 490 nm in both aqueous and micellar media. The most remarkable point of this method is that the molar absorptivities of the gold-BSOPD complex form in the presence of the nonionic TritonX-100 surfactant are almost a 10 times higher than the value observed in the aqueous solution, resulting in an increase in the sensitivity and selectivity of the method. The apparent molar absorptivities were found to be 2.3 × 104 L mol−1 cm−1 and 2.5 × 105 L mol−1 cm−1 in aqueous and micellar media, respectively. The reaction is instantaneous and the maximum absorbance was obtained after 10 min at 490 nm and remains constant for over 24 h at room temperature. The linear calibration graphs were obtained for 0.1–30 mg L−1 and 0.01–30 mg L−1 of gold(III) in aqueous and surfactant media, respectively. The interference from over 50 cations, anions and complexing agents has been studied at 1 mg L−1 of Au(III); most metal ions can be tolerated in considerable amounts in aqueous micellar solutions. The Sandell’s sensitivity, the limit of detection and relative standard deviation (n = 9) were found to be 5 ng cm−2, 1 ng mL−1 and 2%, respectively in aqueous micellar solutions. Its sensitivity and selectivity are remarkably higher than that of other reagents in the literature. The proposed method was successfully used in the determination of gold in several standard reference materials (alloys and steels), environmental water samples (potable and polluted), and biological samples (blood and urine), geological, soil and complex synthetic mixtures. The results obtained agree well with those samples analyzed by atomic absorption spectrophotometry (AAS).

Online preconcentration of nickel(II) in textile effluent and soil samples by SDS coated alumina modified with dithizone mini-column coupled with FAAS

A simple, sensitive and low cost, flow injection time-based method was developed for on-line preconcentration and determination of nickel in textile effluent and soil samples. At the optimum pH, the nickel was retained on the sodium dodecyl sulphate coated alumina modified with dithizone, and subsequently eluted with HCl and determined by flame atomic absorption spectrometry. At a sample frequency of 30 h−1 and a 60 s preconcentration time, the enhancement factor was 100 and the detection limit was 0.54 μg L−1 (3σ). The accuracy of the developed method is sufficient and evaluated with spiked environmental samples.

Development of Online Method for Simultaneous Preconcentration of Cd, Cu, Ni and Zn in Environmental Samples Using Modified Alumina

Abstract A sensitive and simple method for online simultaneous preconcentration of trace heavy metal ions in some of the environmental samples by flame atomic absorption spectrometry has been reported. In present study ammonium lauryl sulphate is used as a new surfactant for modification of alumina with dithizone as a adsorbent for simultaneous preconcentration of Cd, Cu, Ni and Zn. The adsorbed metals on modified alumina were eluted using 1 mL of 1 mol L-1 hydrochloric acid. The influences of the analytical parameters including pH, flow rate of sample, type and volume of eluent and sample volume were investigated. The calibration curve was linear in the range of 0.05–0.5 μg mL-1 for Cd, Cu, Ni and Zn. The limits of detection were 1, 0.5, 1.1 and 0.61 ng mL-1 for Cd, Cu, Ni and Zn respectively. The preconcentration factor of 100 for Cu and 150 for Cd, Ni and Zn was achieved. The developed method was successfully applied for the determination of trace metal ions in soil, water and plant samples.