Preconcentration and preseparation procedure for platinum determination at trace levels by neutron activation analysis

A procedure that simultaneously allows both preconcentration and preseparation of platinum for its determination by neutron activation analysis at trace levels (<0.1 microg x g(-1)) in environmental related matrixes is developed. The method is mainly based on a two-step chemical procedure: (i) a preirradiation concentration/separation based on a column chromatography separation where the platinum is previously retained and subsequently separated from Au, Ca, Na, Br, and P; (ii) a postirradiation separation/purification of the 199Au at 158.4 keV used for the platinum determination via [198Pt (n,gamma)-->199Pt (beta-)-->199Au]. The method eliminates the following radionuclides with the gamma lines in the region of 158 keV: 47Sc (daughter of Ca) at 159.3 keV; 199Au (produced by double neutron capture onto the natural 197Au) at 158.4 keV; 123m Te at 158.8 keV. In addition, the background activity deriving from 24Na, 32p, and 82Br is drastically reduced. The method was tested by the analysis of certified rock material and then applied for platinum determination in airborne particulate matter.     

Simultaneous determination of thiabendazole and mebendazole in tablets by high-performance liquid chromatography

Reversed-phase high performance liquid chromatography using an RP 18 column (4 × 125 mm), tetrahydrofuran-acetonitrile-0.5% formic acid (5:25:70, v/v/v) as mobile phase and UV detection at 254 nm enabled the simultaneous determination of thiabendazole (TZ) and mebendazole (MZ) in tablets. The method showed linearity over 4.0 to 40.0 μg TZ/ml and 6.0 to 60.0 μg MZ/ml. The correlation coefficient r was .9999 for both TZ and MZ. The coefficient of variation (CV) was 0.59-0.80% for TZ and 0.49-0.67% for MZ. The average recovery was 100.54-101.17% for TZ and 100.35-101.13% for MZ. The excipients of the tablets did not interfere in the proposed method. The developed method is precise, accurate, and selective for the determination of both benzimidazoles analyzed.     

Evaluation of radiochemical neutron activation analysis methods for determination of arsenic in biological materials

Radiochemical neutron activation analysis (RNAA) with retention on hydrated manganese dioxide (HMD) has played a key role in the certification of As in biological materials at NIST. Although this method provides very high and reproducible yields and detection limits at low microgram/kilogram levels, counting geometry uncertainties may arise from unequal distribution of As in the HMD, and arsenic detection limits may not be optimal due to significant retention of other elements. An alternate RNAA procedure with separation of arsenic by solvent extraction has been investigated. After digestion of samples in nitric and perchloric acids, As(III) is extracted from 2 M sulfuric acid solution into a solution of zinc diethyldithiocarbamate in chloroform. Counting of (76)As allows quantitation of arsenic. Addition of an (77)As tracer solution prior to dissolution allows correction for chemical yield and counting geometries, further improving reproducibility. The HMD and solvent extraction procedures for arsenic were compared through analysis of SRMs 1577c (bovine liver), 1547 (peach leaves), and 1575a (pine needles). Both methods gave As results in agreement with certified values with comparable reproducibility. However, the solvent extraction method yields a factor of 3 improvement in detection limits and is less time-consuming than the HMD method. The new method shows great promise for use in As certification in reference materials.     

Determination of trace elements in BGO by neutron activation analysis

We report on the determination of trace elements in a set of Bi₄Ge₃O₁₂ (BGO) crystals by neutron activation analysis. By using doped polycrystalline BGO powders as calibration standards, we have measured the concentrations of Al, Mn, Cu, Co, Cr and Fe in the crystals with a sensitivity of 0.5–500 ppb, and we have determined the segregation coefficients. We have also studied the correlation between the trace elements and the “radiation damage” (color center formation) effect.     

离子色谱法测草酸二甲酯中痕量氯离子

建立了离子色谱测定草酸二甲酯中的痕量氯离子的分析方法,用双氧水和碳酸钠在加热条件下对草酸二甲酯进行水解氧化的预处理,选用AS-23离子色谱柱,4.5m M碳酸钠/0.8m M碳酸氢钠作为淋洗液对样品中的氯离子进行分离测定。该方法的回收率为94.1%~105.4%,实际样品测定相对标准偏差RSD为3.61%(n=6)。