Speciation of chromium by high-performance thin-layer chromatography with direct determination by laser ablation inductively coupled plasma mass spectrometry

It is of considerable importance to be able to distinguish metallic species because their toxicity depends on their chemical form. Therefore, the analysis of environmental samples can be enhanced by the combination of high-performance thin-layer chromatography (HPTLC) with laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). In this study, Cr (3+) and Cr (6+) were separated on silica gel HPTLC plates using aqueous mobile phases. Separation was achieved in seconds with retardation factors ( R f ) of 0 and 1 for Cr (3+) and Cr (6+), respectively. LA was used to volatilize the chromium species directly from the chromatographic material prior to ICPMS detection. A linear calibration was obtained, and detection limits (3sigma) of 6 ng for Cr (6+) and 0.4 ng for Cr (3+) were achieved with precision ranging from 3 to 40% at the 95% confidence level. The silicon present in the stationary phase was used as an internal standard. This procedure allows for a rapid separation and quantification, requires only 0.5 muL of sample, and lower detection limits can be achieved through preconcentration.     

Fraunhofer effect atomic absorption spectrometry

The dark lines in the solar spectrum were discovered by Wollaston and cataloged by Fraunhofer in the early days of the 19th century. Some years later, Kirchhoff explained the appearance of the dark lines: the sun was acting as a continuum light source and metals in the ground state in its atmosphere were absorbing characteristic narrow regions of the spectrum. This discovery eventually spawned atomic absorption spectrometry, which became a routine technique for chemical analysis in the mid-20th century. Laboratory-based atomic absorption spectrometers differ from the original observation of the Fraunhofer lines because they have always employed a separate light source and atomizer. This article describes a novel atomic absorption device that employs a single source, the tungsten coil, as both the generator of continuum radiation and the atomizer of the analytes. A 25-microL aliquot of sample is placed on the tungsten filament removed from a commercially available 150-W light bulb. The solution is dried and ashed by applying low currents to the coil in a three-step procedure. Full power is then applied to the coil for a brief period. During this time, the coil produces white light, which may be absorbed by any metals present in the atomization cloud produced by the sample. A high-resolution spectrometer with a charge-coupled device detector monitors the emission spectrum of the coil, which includes the dark lines from the metals. Detection limits are reported for seven elements: 5 pg of Ca (422.7 nm); 2 ng of Co (352.7 nm); 200 pg of Cr (425.4 nm); 7 pg of Sr (460.7 nm); 100 pg of Yb (398.8 nm); 500 pg of Mn (403.1 nm); and 500 pg of K (404.4 nm). Simultaneous multielement analyses are possible within a 4-nm spectral window. The relative standard deviations for the seven metals are below 8% for all metals except for Ca (10.7%), which was present in the blank at measurable levels. Analysis of a standard reference material (drinking water) resulted in a mean percent recovery of 91%. This report attempts to give an historical perspective on the development of a novel atomic spectrometer based on the Fraunhofer effect.     

原子吸收法测定催化剂中的镧含量

工业上经常采用镧金属钝化剂防止催化剂失活,但必须严格控制钝化剂的添加量,否则会起副作用.采用高温酸消解法处理平衡剂,然后用火焰原子吸收光谱法测定催化剂中镧含量,考察了温度、消解酸度等对测量结果的影响,优选出了最佳分析测试条件.所建方法简便、灵敏、准确,该方法回收率在96%～101%之间,变异系数小于2.1%.最小检出限为0.048 mg/L.     

New developments in atomic absorption spectrometry

We consider some new methods and measuring instruments used in atomic absorption spectrometry: flame atomizer/annular-slot burner, rapidly heated graphite furnace with ballast, high resolution spectrometers with continuum source, and also the new standard GOST R 8.649-2008 of January 1, 2010.     

Combining laser ablation/liquid phase collection surface sampling and high-performance liquid chromatography-electrospray ionization-mass spectrometry

This letter describes the coupling of ambient pressure transmission geometry laser ablation with a liquid phase sample collection method for surface sampling and ionization with subsequent mass spectral analysis. A commercially available autosampler was adapted to produce a liquid droplet at the end of the syringe injection needle while in close proximity to the surface to collect the sample plume produced by laser ablation. The sample collection was followed by either flow injection or a high-performance liquid chromatography (HPLC) separation of the extracted components and detection with electrospray ionization mass spectrometry (ESI-MS). To illustrate the analytical utility of this coupling, thin films of a commercial ink sample containing rhodamine 6G and of mixed isobaric rhodamine B and 6G dyes on glass microscope slides were analyzed. The flow injection and HPLC-ESI-MS analysis revealed successful laser ablation, capture, and with HPLC, the separation of the two compounds. The ablated circular area was about 70 μm in diameter for these experiments. The spatial sampling resolution afforded by the laser ablation, as well as the ability to use sample processing methods like HPLC between the sample collection and ionization steps, makes this combined surface sampling/ionization technique a highly versatile analytical tool.     

Speciation and determination of thallium by on-line microcolumn separation/preconcentration by flow injection-flame atomic absorption spectrometry using immobilized oxine as sorbent

A flow injection analysis (FIA) system incorporation a microcolumn of immobilized oxine on surfactant-coated alumina had been devised for performing rapid thallium enrichment/matrix removal in flame atomic absorption spectrometry (FAA). The preconcentration is based on the deposition of thallium(I) on microcolumn and subsequent elution with 500 microl of sodium thiosulfate (1 moll(-1)). In the presence of EDTA, only Tl(I) was retained on the microcolumn. Total thallium was determined after reduction of Tl(III) to Tl(I) by hydroxyl amine hydrochloride. A sample volume of 25 ml resulted in a preconcentration factor of 77. Precision at 30 microgl(-1) was 2.6% RSD (n=10). With 25 ml sampling volume a detection limit of 2.5 microgl(-1) was determined. The effect of potential interfering ions on the determination was studied. The method was applied for the determination of thallium in water, waste water, hair, nail, coal, and standard reference alloys. The accuracy was assessed through recovery experiment, independent analysis by Furnace-AAS, and analysis of certified reference alloys.     

原子吸收光谱法测定红树林中的重金属

本文采用原子吸收光谱法测定白骨壤(Avicenia marina),秋茄树(Kandelia candel)两种红树林中的铜、锌、铅、镉四种重金属含量。回收率在98.3%～104%之间,相对标准偏差在1.57%～3.92%之间,该方法快速、灵敏、准确.     

Speciation of chromium in water samples with cloud point extraction separation and preconcentration and determination by graphite furnace atomic absorption spectrometry

A novel method has been developed for the speciation of chromium in natural water samples based on cloud point extraction (CPE) separation and preconcentration, and determination by graphite furnace atomic absorption spectrometry (GFAAS). In this method, Cr(III) reacts with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one (PMBP) yielding a hydrophobic complex, which then is entrapped in the surfactant-rich phase, whereas Cr(VI) remained in aqueous phase. Thus, separation of Cr(III) and Cr(VI) could be realized. Total chromium was determined after the reduction of Cr(VI) to Cr(III) by using ascorbic acid as reducing reagent. PMBP was used not only as chelating reagent in CPE procedure, but also as chemical modifier in GFAAS determination of chromium. The detection limit for Cr(III) was 21 ng L(-1) with an enrichment factor of 42, and the relative standard deviation was 3.5% (n=7, c=10 ng mL(-1)). The proposed method has been applied to the speciation of chromium in natural water samples with satisfactory results.     

The use of slurry sampling for the determination of manganese and copper in various samples by electrothermal atomic absorption spectrometry

Manganese and copper in multivitamin-mineral supplements and standard reference materials were determined by slurry sampling electrothermal atomic absorption spectrometry. Slurries were prepared in an aqueous solution containing Triton X-100. The effects of different parameters such as ratio of solid to liquid phase volume, total slurry volume and addition of Triton X-100 as a dispersant on the analytical results were investigated. The graphite furnace programs were optimized for slurry sampling depending on the analytes and their concentrations in the samples. The linear calibration method with aqueous standard solutions was used for the quantification. At optimum experimental conditions, R.S.D. values were below 5%. The analytes were determined in the limits of 95% confidence level with respect to certified values in coal and soil standard reference materials and to those found by wet-digestion in multivitamin-mineral supplements. Detection limits (3delta) for Mn and Cu were 0.10 microg L(-1) and 1.82 microg L(-1) for 10 microL coal standard reference material slurry, respectively.     

多动症儿童发锌含量测定

本文采用原子吸收光谱法测定了多动症儿童发锌含量,精密度为0.34%,回收率为99.5%,结果表明,多动症儿童有发锌降低的倾向。     

石墨炉原子吸收法测定头发中硒

利用优级纯硝酸浸润,放置过夜,适当水浴加热的方法,将头发样品制备成溶液,用石墨炉原子吸收法测定头发中硒,在选定的测定条件下检出限0．004mg／l,精密度3．7％,回收率在91．1％-98．2％之间。     

Analysis of high-purity cadmium and cadmium dioxide by atomic absorption spectrometry

To ensure high-speed analytical support to the technology of cadmium tungstate single crystal growth, we have developed an electrothermal atomic absorption spectrometry technique for analysis of high-purity cadmium and cadmium oxide for the technologically important impurities Ag, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Sn with detection limits from 2 × 10^–7 to 6 × 10^–6 wt %.