RESUMEN
A new method for speciation analysis of tellurium(IV) and Te(VI) using high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) has been developed. Tellurium(IV) and Te(VI) were completely separated using a reversed-phase column with an L-cysteine eluent under an isocratic elution condition. The detection limits (3σ) of Te(IV) and Te(VI) monitored by HPLC-ICP-MS at m/z 125 were 1.4 and 0.5 ng g-1, respectively. The proposed determination method was precisely applied to assessing total concentrations and chemical species of Te in several standard solutions. The recovery rates of Te(IV) and Te(VI) were almost 100% from the results of the addition-recovery examinations, even when a high matrix sample such as seawater was measured. The method was applied to seawater samples and electronic products, and was proved quite effective for environmental risk assessment.
RESUMEN
For accurately determining nutrients in seawater by continuous flow analysis (CFA), the characteristic of the calibration curve was examined in detail. Under absorbance below 0.8, the calibration curve and the bracketing methods showed more accurate results that the bias fell below 0.5%. The analytical results of dissolved silica in seawater from the nutrient maximum layer of the Pacific Ocean obtained by the proposed methods showed good agreement with those obtained by an ion exclusion chromatography postcolumn absorption spectrophotometry (IEC-postcolumn) and an ion exclusion chromatography isotope dilution ICP mass spectrometry (IEC-ID-ICP-MS). From the results, the analysis of nutrients in seawater could be accurately carried out by CFA with an expanded uncertainty of below 1% using both the calibration curve and the bracketing methods with an appropriate absorbance range.
RESUMEN
The determination of dissolved silica in seawater was investigated by an ion-exclusion chromatography with a post-column derivatization/silicomolybdenum yellow method. To determine dissolved silica in seawater accurately, the experimental conditions, such as the volume of a reaction coil, the eluent concentration and the sample dilution factor, were optimized. This is the first report that has examined the details of the experimental condition for the measurement of dissolved silica in seawater by ion-exclusion chromatography with silicomolybdenum-yellow detection. The developed method was compared with the widely used continuous flow analysis and an ion-exclusion chromatography isotope dilution inductively coupled plasma mass spectrometry, which is a primary method of measurement. The analytical results by the three methods were in good agreement, considering the expanded uncertainty with a coverage factor, 2. The validity of the three methods was confirmed with each other. The developed method can give a quantitative value with less than 1% of the expanded uncertainty, and can be used for the determination of dissolved silica in candidate reference materials having a seawater matrix.
RESUMEN
Ion exclusion chromatograph (IEC) isotope dilution (ID) inductively coupled plasma mass spectrometry (ICP-MS) (IEC-ID-ICP-MS) was developed for measurement of dissolved silica in seawater, which was applied to production of certified reference materials (CRMs) of three concentration levels of nutrients (high, medium and low levels). IEC-ICP-MS has been employed to separate dissolved silica from seawater matrix. In the present study, in order to solve substantial problems due to spectral interference in ICP-MS and to improve the accuracy of IEC-ICP-MS beyond standard addition or conventional calibration methods, ID method was coupled with ICP-sector field mass spectrometry (operated under medium resolution,i.e., m/Δm=4000). In addition, effects of various operating parameters in ICP-MS on a silicon background level were also investigated to obtain lower background equivalent concentration (BEC). As a result, 3 ng g(-1) of the BEC and 0.5 % of relative standard uncertainties were achieved in the analyses of dissolved silica in seawater samples at concentration levels from 4.0 mg kg (-1) to 0.8 mg kg(-1) as silicon. The developed method was successfully validated by analyses of an artificial seawater containing a known amount of silicate and the seawater certified reference material MOOS-2 produced by the National Research Council Canada.