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Analytical and Bioanalytical Chemistry (v.362, #7-8)
Use of thermal ionization isotope dilution mass spectrometry (TI-IDMS) as an oligo-element method for the determination of photographically relevant trace elements in AgCl emulsions by F. Vanhaecke; J. Diemer; K. G. Heumann; L. Moens; R. Dams (pp. 553-557).
Thermal ionization isotope dilution mass spectrometry (TI-IDMS) was used as an oligo-element method for the determination of Cr, Cd and Pb in photographic AgCl emulsions. After addition of an appropriate amount of isotopically enriched spikes (53Cr, 116Cd and 206Pb) to the solid samples, the latter were completely dissolved in NH3 solution, permitting isotopic exchange to take place. Thereafter, AgCl was selectively removed by precipitation, whereby ultrasonic treatment was used to enhance the recovery of the elements of interest. Despite the use of concentrated HNO3 and H2O2 during further sample processing, preliminary experiments indicated the presence of a substantial remainder of the organic matrix (gelatine). Hence, the analytes of interest were isolated by means of electrolytic deposition on Pt electrodes. Subsequently, the deposits were dissolved from the Pt electrodes using a mixture of concentrated HNO3 and H2O2 and the solutions evaporated to dryness. The solid residues were taken up in diluted HNO3 and loaded onto Re filaments. In order to improve the ionization yield, prior to the sample, a silicagel suspension containing AlCl3 was loaded onto the filament and after sample loading, both H3BO3 (for Cr and Pb) and H3PO4 (for Cd and Pb) were added as further ionization aids. Finally, the isotope ratios of interest (52Cr/53Cr, 114Cd/116Cd and 206Pb/208Pb) were determined using thermal ionization mass spectrometry, whereby all three analyte elements were vaporized from the same filament. The limits of detection obtained using this procedure range from 0.4 ng (for Cd) to 4 ng (for Pb). Four different AgCl emulsions were analyzed. For Cr, the concentration found was quite similar for all emulsions analyzed, as it varied between ∼ 40 and ∼ 100 ng/g only. For Cd, very low values were found for all samples analyzed (≤ 3 ng/g). Finally, for Pb a much larger variation from ∼ 10 ng/g up to ∼ 5.5 μg/g was observed. For the sample with the highest Pb content, an excellent agreement could be established between the results obtained using quadrupole-based ICP-IDMS and those using TI-IDMS. For the determination of Cr by means of quadrupole-based ICP-IDMS, an instrument equipped with a ShieldTorch system was used to avoid spectral overlap of the 52Cr+ and 40Ar12C+ ion signals. Also in this case, the results obtained are in very good agreement with those obtained using TI-IDMS. The comparison between TI-IDMS and ICP-IDMS also made clear that sample inhomogeneity limits the between-sample precision attainable.
Comparison of microwave-assisted acid leaching techniques for the determination of heavy metals in sediments, soils, and sludges by D. Florian; R. M. Barnes; G. Knapp (pp. 558-565).
Microwave-assisted EPA method 3051 for nitric acid leaching of environmentally key elements from sediments, soils, and sludges was tested, and the influence of leaching temperature and time on element recovery for an estuarine sediment (CRM 277) was investigated. The extraction efficiencies for four certified reference materials applying EPA method 3051, an optimized nitric acid procedure, and an aqua regia (HCl/HNO3 3:1) procedure were compared. Digestions were carried out in a high-pressure microwave system offering simultaneous temperature and pressure control for all digestion vessels employed. Eight elements (Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn) were determined by ICP-AES and ICP-MS. Extraction efficiency strongly depended on the applied leaching parameters and varied for certain elements among different materials when a nitric acid procedure was applied. In general, element recoveries obtained from the aqua regia procedure were superior to those obtained from nitric acid procedures and showed good agreement with the 95% confidence interval of the certified value for most of the elements investigated.
Chemiluminescence determination of sulfite in sugar and of sulfur dioxide in air using the tris(2,2′-bipyridyl)ruthenium-KIO4 system by F. Wu; Zhike He; H. Meng; Liangjie Yuan; Xiaoyan Li; Yun’e Zeng (pp. 566-570).
The chemiluminescence (CL) detection for the determination of sulfite using the reaction of Ru(bipy)3 2+(bipy=2,2′-bipyridyl)-SO3 2–-KIO4 is described. The concentration of sulfite is proportional to the CL intensity from 1.0 × 10–7 to 1.0 × 10–4 mol/L. The limit of detection is 2.0 × 10–8 mol/L and the relative standard deviation is 4.4% for a 2 × 10–5 mol/L sulfite solution (n = 9). This method has successfully been applied to the determination of sulfite in powdered sugar (sucrose) and of sulfur dioxide in air by using triethanolamine (TEA) as absorbent material.
Flow injection analysis of Zn and Co in beverages, biological, environmental and pharmaceutical samples by S. G. Aggarwal; K. S. Patel (pp. 571-576).
A new, simple, rapid and selective flow injection analysis (FIA) method for the spectrophotometric quantification (speciation of inorganic and organic form) of Zn and Co with ammonium thiocyanate and malachite green (MG) in the presence of surfactants (CPC and TX-100) is described. The value of apparent molar absorptivity of the Zn- and Co- complexes are (1.23) × 104 and (8.67) × 103 L mol–1cm–1 at absorption maximum, 635 nm, respectively. The detection limit (amount causing a peak height > 3 s) is 15 ppb Zn and 20 ppb Co, whereas their optimum working ranges for the quantitative determinations are 0.05–2.0 ppm Zn and 0.07–2.5 ppm Co in the real samples. The sample thoughput of the method is 120 samples/h at the flow rate of 5.0 mL/min with rel. std. dev. of < ± 1%. The method is free from interferences of almost all ions which are commonly associated with these metals in the complex materials. The composition of the complexes and their reaction mechanism involved are discussed. The effect of FIA and analytical variables for the determination of the metals are optimized. The method has been applied to the quantification of Zn and Co in beverages, biological, environmental, and pharmaceutical samples.
Determination of diclofenac salts in pharmaceutical formulations by R. Bucci; A. D. Magrì; A. L. Magrì (pp. 577-582).
Two methods for the determination of the diclofenac salts [sodium (DS) or diethylammonium (DA)] in three pharmaceutical formulations (tablets, suppositories and gel) are presented. In the first, diclofenac salt is determined both, by measuring the absorbance of the solutions at a fixed wavelength (λ = 276 nm) and using a multi-wavelength computational program to process the spectrophotometric data in a selected range (λ = 230– 340 nm). The above method can not be applied to the analysis of gel formulations because of the opalescence of these solutions. In this case, the analysis is performed measuring the peak-to-peak amplitude in the first-derivative UV spectrum (1D 261.296). In the second method, diclofenac (DH) is precipitated in acid medium and determined by the analysis of the endothermic peak (tp = 182 °C) in the DSC curve obtained in nitrogen atmosphere. Finally, some aspects of chemical (solubility, acid-base equilibria, redox reaction), spectroscopic (UV, IR) and thermoanalytical (TG, DSC) behaviour of DS and DH and the values of the parameters which enable to calculate the UV spectrum of DS in aqueous solution are reported.