Determination of As, Hg and Pb in herbs using slurry sampling flow injection chemical vapor generation inductively coupled plasma mass spectrometry.
Analysis of herbs for As, Hg and Pb has been carried out using slurry sampling inductively coupled plasma mass spectrometry (ICP-MS) with flow injection vapor generation. Slurry containing 0.5% m/v herbal powder, 0.1% m/v citric acid and 2% v/v HCl was injected into the VG-ICP-MS system for the determination of As, Hg and Pb that obviate dissolution and mineralization. Standard addition and isotope dilution methods were used for quantifications in selected herbal powders. This method has been validated by the determination of As, Hg and Pb in NIST standard reference materials SRM 1547 Peach Leaves and SRM 1573a Tomato Leaves. The As, Hg and Pb analysis results of the reference materials agreed with the certified values. The precision obtained by the reported procedure was better than 7% for all determinations. The detection limit estimated from standard addition curve was 0.008, 0.003, and 0.007 ng mL(-1) for As, Hg and Pb, respectively.
Biosorption of Zn2+, Ni2+ and Co2+ from water samples onto Yarrowia lipolytica ISF7 using a response surface methodology, and analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES)
A response surface methodology (RSM) based on a central composite design with five variables and five levels was employed to interpret the biosorption efficiency of Zn2+, Ni2+ and Co2+ ions onto Yarrowia lipolytica ISF7. Independent variables, viz. pH, temperature, and Zn2+, Ni2+ and Co2+ ion concentrations were transformed into coded values and a quadratic model was built to predict the responses. Analysis of variance (ANOVA) and t-test statistics were used to test the significance of the independent variables and their interactions. The predicted maximum biosorption efficiencies (99.65, 99.30 and 98.78% for Zn2+, Ni2+ and Co2+ ions, respectively) under the optimum recommended conditions (pH 6.0, 25 °C, 30, 25 and 30 mg L−1 of Zn2+, Ni2+ and Co2+ ions) following 24 h mixing were very close to the experimental values (99.65, 99.30 and 98.78% for Zn2+, Ni2+ and Co2+ ions, respectively). The equilibrium equation was extensively investigated and found to be efficiently represented by a Langmuir model with maximum monolayer biosorption capacities of 31.96, 24.40 and 25.77 mg g−1 for Zn2+, Ni2+ and Co2+, respectively. The biosorption data trend closely followed a pseudo-second-order kinetic model. FTIR and scanning electron microscopy coupled with X-ray energy dispersed analysis (SEM-EDX) provided proof of progress of ion biosorption on the yeast surfaces.
Flow injection atomic absorption spectrometry with air compensation
Flow injection atomic absorption spectrometry (FI-AAS) with air compensation was studied and compared with Fl-AAS using solvent compensation and with conventional AAS. It seems clear that air compensation offers important advantages, as the great increase in nebulisation efficiency improves the sensitivity and selectivity. The reproducibility obtained for both peak height and peak area is similar to or better than that obtained using other FI-AAS systems and comparable to that given by conventional AAS. The problem of using a pumping flow-rate lower than that of the nebuliser aspiration (necessary for chromatographic and solvent extraction procedures coupled with FI-AAS) is solved using the air compensation method with advantages over other procedures.