Application of manganese(IV) dioxide microcolumn for determination and speciation of nitrite and nitrate using a flow injection analysis-flame atomic absorption spectrometry system

A flow injection (FI) method with flame atomic absorption spectrometry (FAAS) detection was developed for the determination and speciation of nitrite and nitrate in foodstuffs and wastewaters. The method is based on the oxidation of nitrite to nitrate using a manganese(IV) dioxide oxidant microcolumn where the flow of the sample through the microcolumn reduces the MnO₂ solid phase reagent to Mn(II), which is measured by FAAS. The absorbance of Mn(II) are proportional to the concentration of nitrite in the samples. The injected sample volume was 400 μL with a sampling rate of analyses was 90 h⁻¹ with a relative standard deviation better than 1.0% in a repeatability study. Nitrate is reduced to nitrite in proposed FI-FAAS system using a copperized cadmium microcolumn and analyzed as nitrite. The calibration curves were linear up to 20 mg L⁻¹ and 30 mg L⁻¹ with a detection limit of 0.07 mg L⁻¹ and 0.14 mg L⁻¹ for nitrite and nitrate, respectively. The results exhibit no interference from the presence of large amounts of ions. The method was successfully applied to the speciation of nitrite and nitrate in spiked natural water, wastewater and foodstuff samples. The precision and accuracy of the proposed method were comparable to those of the reference spectrophotometric method.     

Separation and Detection of Arsenic and Selenium Species in Environmental Samples by HPLC-ICP-MS

A method is presented for arsenic speciation analysis of an oyster sample using ion chromatography coupled with an inductively coupled plasma mass spectrometry (ICP-MS) instrument. A strong anion exchange resin was employed with a step gradient elution of 0.1 mM/0.1 M K 2 SO 4 at pH 10.2. Arsenobetaine and dimethylarsinic acid were determined following extraction based on trypsin enzymolysis with 95-100% extraction efficiency. Limits of detection in the range 0.1-0.3 mg kg m 1 of arsenic were obtained for organic arsenic species. No inorganic arsenic was detected. Validation was performed using TORT-2 as a certified reference material. Although high performance liquid chromatography (HPLC) coupled to ICP-MS is an effective method for speciation analysis it is not always necessary to obtain such a detailed picture. A simple liquid chromatographic separation technique based upon mini-column technology is presented. It was developed to obtain a fast, efficient and reliable separation of inorganic from organic, i.e. assumed toxic from non-toxic, arsenic and selenium species suitable for use as an initial screening method for environmental analysis. Two types of strong anion exchange resin were tested. Excellent separation was obtained for both min-column resins and analysis times were within 7 min. Limits of detection obtained for inorganic arsenic, organic arsenic, selenomethionine, Se IV and Se VI were 1.6, 1.8, 66, 32 and 22 µg kg m 1 , respectively.     

微型柱现场预富集流动注射火焰原子吸收测定环境水样中的铅和镉

文章以负载8-羟基喹啉(8-HQ, Oxine)、二乙基二硫代氨基甲酸盐(DDTC)和吡咯啶二硫代氨基甲酸铵(APDC)三种螯合剂的活性炭(AC)为微型柱的吸附材料,采用微型柱现场采样 (MFS)分析技术实现了连续现场富集环境水样中的痕量Pb和Cd,并在实验室中采用流动注射(FI) -火焰原子吸收(FAAS)联用技术对吸附柱中富集的Pb和Cd进行测定。该方法用于水中微量元素(GBW—08608)和南湖水样中Pb和Cd的测定均获得了满意的结果。10 mL富集的检出限(3σ)Pb：1.58 μg·L-1;Cd：0.062 μg·L-1 ,相对标准偏差Pb：1.62%;Cd：1.96%。     

基于FIA-ISE测定WACR交换性能的研究

基于FIA-ISE测定痕量Na~+原理,建立了一种自动测定弱酸性阳离子交换树脂(WACR)交换性能的方法.本研究对WACR交换性能的各影响因素进行考察,优选出其测定条件:微型交换柱内径3.0mm、长80mm;交换反应温度33℃;树脂填充量0.1762g;样品为NaOH溶液(Na~+浓度10mg/L),流速0.92mL/min;再生剂(HCl)浓度4%,流速1.25mL/min,用量40mL.本方法实现了一次测定同时获得WACR平衡交换容量(E_q)、全交换容量(E_t)和利用率(η)等多个指标.与GB法对比,二者相关性好(r=0.9904).