Inter-method comparison for the determination of antimony and arsenic in peat samples

Four analytical approaches, based on different physical principles, for the determination of antimony (Sb) and arsenic (As) in ancient peat samples were critically evaluated: (a) open vessel digestion/hydride generation-atomic absorption spectrometry (HG-AAS), (b) closed-pressurized digestion in a microwave oven followed by sector field-inductively coupled plasma-mass spectrometry (SF-ICP-MS), (c) digestion in a microwave autoclave and subsequent quadrupole-inductively coupled plasma-mass spectrometry (Q-ICP-MS) measurements and (d) instrumental neutron activation analysis (INAA). The quality control scheme applied, always included the use of adequate plant reference materials to ensure the accuracy and precision of the analytical procedures. Additionally, two internal peat reference materials were analyzed using all four analytical approaches, generally showing good agreement for both elements. Method detection limits for As and Sb provided by all procedures were approximately 5 and 2 ng g⁻¹ which is sufficiently low for the reliable quantification of both elements in ancient, pre-anthropogenic peat samples. A comparison of As and Sb concentrations in a set of peat samples determined by INAA, HG-AAS and SF-ICP-MS revealed that INAA underestimated the values in a systematic manner, whereas HG-AAS and SF-ICP-MS data agreed very well. Best precision of the results was obtained by analytical procedures involving HG-AAS or Q-ICP-MS and varied from 3.6 to 4.3% and 7.1 to 7.5% for As (at about 0.5 μg g⁻¹) and Sb (at about 0.1 μg g⁻¹), respectively. The highest sample throughput (40 samples per run accomplished in 2 h) combined with low risk of sample contamination could be realized in the high-pressure microwave autoclave. The amount of sample required by all approaches was 200 mg, except for INAA which needed at least 25 times more sample mass to achieve comparable detection limits. For the quantification of As and Sb, inductively coupled plasma-mass spectrometry (ICP-MS) was preferred over INAA and HG-AAS, mainly because (a) less sample is needed and (b) As and Sb can be determined simultaneously. In addition, ICP-MS offers the possibility to measure concurrently a wide range of other elements which also are of environmental interest.     

Improved determination of selenium in plant and peat samples using hydride generation-atomic fluorescence spectrometry (HG-AFS)

A robust, accurate and sensitive analytical procedure for the determination of Se in plant and peat samples by hydride generation-atomic fluorescence spectrometry (HG-AFS) was developed. Aliquots (200 mg) of dried samples were digested with 3 mL nitric acid and 0.5 mL hydrogen peroxide in closed, pressurized PTFE vessels in a microwave oven at 220 °C. Addition of HBF₄ or HF to the digestion mixture was not required because experiments demonstrated that Se was not hosted in the silicate fraction of the investigated sample matrices. Selenium(VI) was directly reduced to Se(IV) in the undiluted digestion solutions after addition of 3.8 mL of 4 M HCl in a microwave oven at 103 °C for 3 min. Other reduction reagents, such as hydroxylamine hydrochloride or urea, were not necessary to cope with potential interferences from nitrogen oxides that could hamper the reliable determination of Se by HG-AFS. Optimum hydride generation of Se was achieved by using 0.9% NaBH₄ and 4.5 M HCl. A solution detection limit of 11 ng L⁻¹ was obtained under the optimized experimental conditions which corresponds to a method detection limit of 2.8 ng g⁻¹ in solid peat and plant materials. The precision of replicate measurements was better than 3% at Se concentrations of 50 ng L⁻¹. The analytical procedure was critically evaluated by analysing two certified plant reference materials (SRM 1515 Apple Leaves and SRM 1547 Peach Leaves) as well as three peat reference materials. Excellent agreement between the experimental values ranging from 50 ng g⁻¹ to ∼2 μg g⁻¹ and the certified concentrations was obtained.     

氧弹燃烧-氢化物发生-原子吸收法测定硫磺中砷

研究了氧弹燃烧、NaOH溶液吸收预处理硫磺样品的方法,优化了HG-AAS法测定砷的最佳条件。     

Analytical procedures for the determination of selected major (Al, Ca, Fe, K, Mg, Na, and Ti) and trace (Li, Mn, Sr, and Zn) elements in peat and plant samples using inductively coupled plasma-optical emission spectrometry

A simple, robust and reliable analytical procedure for the determination of Al, Ca, Fe, K, Li, Mg, Mn, Na, Sr, Ti, and Zn in peat and plant materials by inductively coupled plasma-optical emission spectrometry (ICP-OES) was developed. A microwave heated high pressure autoclave was used to digest powdered sample aliquots (approximately 200 mg) with different acid mixtures including nitric acid (HNO₃), tetrafluoroboric acid (HBF₄) and hydrogen peroxide (H₂O₂). The optimized acid mixture for digestion of plant and peat samples consisted of 3 mL HNO₃ and 0.1 mL HBF₄, in addition to H₂O₂ which was sub-boiled into the PTFE digestion tubes during heating of the autoclave. Using HNO₃ alone, recoveries of Al and Ti were too low by 40 and 160%, respectively, because HNO₃ could not fully liberate the analytes of interest from the silicate fraction of the plant and peat matrix. However, for all other elements (such as Mn, Sr, and Zn), the use of HBF₄ was less critical. The accuracy of the analytical procedure developed was evaluated with peat and plant reference materials of different origin and composition. The ICP-OES instrument was optimized using solutions of plant reference materials considering RF power, nebulizer pressure, auxiliary gas flow and rinse time. Scandium was used as an online internal standard (IS) as it provided accurate results and showed less than 3% drift in sensitivity over time which was lower compared to other potential IS such as Rh (20%) and In (6%). The combination of most sensitive and less sensitive wavelengths allowed to obtain low detection limits and highest possible dynamic range. The achieved procedure detection limits ranged from 0.05 μg g⁻¹ (Li) to 15 μg g⁻¹ (Ca) and allowed a precise quantification of all elements. Comparative X-ray fluorescence spectrometric measurements of solid peat and plant samples generally agreed well with results obtained by digestion/ICP-OES. To overcome interferences caused by Na, K, and Li, a solution of 10 μg g⁻¹ CsCl₂ was successfully used as an ionization buffer. The good agreement between the found and certified concentrations in plant and peat reference materials indicates that the developed analytical procedure is well suited for further studies on the fate of major elements in plant and peat matrices.     

微波消解样品-氢化物发生-原子吸收光谱法测定苦荞中微量硒

苦荞样品经硝酸消化处理后,用6 mol.L-1盐酸溶液将稳定态的硒(Ⅵ)还原成硒(Ⅳ),然后再以硼氢化钾为还原剂,盐酸(1+99)溶液为载液,用氢化物发生-原子吸收光谱法测定硒含量。在优化的试验条件下,硒的质量浓度在5~40μg.L-1范围内与其吸光度呈线性关系,检出限(3S/N)为0.083μg.L-1。用此方法分析了3个苦荞试样,加标平均回收率为97.3%。     

出口食用甲鱼中有害元素As、Hg的同时测定

建立了微波消解-氢化物发生原子荧光光谱法(HG-AFS)同时测定出口食用甲鱼中As、Hg残留量的方法,并对HG-AFS工作参数及条件进行了优化和选择。As检出限为0.056μg/L,Hg检出限为0.0071μg/L;相对标准偏差As为0.4%(n=11,ρAs=20μg/L),Hg为0.7%(n=11,ρHg=10μg/L);回收率范围为92%~99%。本法已用于出口食用水生活甲鱼中As、Hg残留量的检测。     

Speciation of arsenic in ground water samples: A comparative study of CE-UV, HG-AAS and LC-ICP-MS

The performance of capillary electrophoresis-ultraviolet detector (CE-UV), hydride generation-atomic absorption spectrometry (HG-AAS) and liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS) have been compared for the speciation of arsenic (As) in groundwater samples. Two inorganic As species, arsenite (As^III), arsenate (As^V) and one organo species dimethyl arsenic acid (DMA) were mainly considered for this study as these are known to be predominant in water. Under optimal analytical conditions, limits of detection (LD) ranging from 0.10 (As^III, AsT) to 0.19 (DMA) μg/l for HG-AAS, 100 (As^III, DMA) to 500 (As^V) μg/l for CE-UV and 0.1 (DMA, MMA) to 0.2 (As^III, As^V) μg/l for LC-ICP-MS, allowed the determination of the above three species present in these samples. Results obtained by all the three methods are well correlated (r² = 0.996*** for total As) with the precision of <5% R.S.D. except CE-UV. The effect of interfering ions (e.g. Fe²⁺, Fe³⁺, SO₄²⁻ and Cl⁻) commonly found in ground water on separation and estimation of As species were studied and corrected for. Spike recovery was tested and found to be 80-110% at 0.5 μg/l As standard except CE-UV where only 50% of the analyte was recovered. Comparison of these results shows that LC-ICP-MS is the best choice for routine analysis of As species in ground water samples.     

微波辅助消解-原子荧光法测定玻璃中的镉砷铅

光学玻璃中的各种元素对玻璃的光学性能有不同的影响。如加入镉可以提高玻璃折射率;砷的引入能增加玻璃的透光度,含铅玻璃具有低成本、高折射性等优点。但是镉、砷、铅均为有毒元素,玻璃加工和处理过程以及毒废弃物的处理都可能引起水、土壤、大气的污染并给人体带来一定的危害     

微波消解ICP-AES法测量铁锰结壳中的砷

借助微波密闭消解技术和电感耦合等离子体原子发射光谱(ICP-AES)方法,研究试样溶解和仪器测定的最佳工作条件,建立了快速测定海底铁锰结壳中微量砷的方法.结果表明,微波密闭消解法处理铁锰结壳,效率高、损失少、空白低.微波密闭消解和ICP-AES相结合,分析操作简单,结果准确,并能多元素同时测定.该方法相对标准偏差小于5% (n=5),砷的回收率在102%～107%之间,检出限为5.55 μg/L,适合铁、锰含量高的海底结壳样品中砷的定量分析.     

Dry ashing of organic rich matrices with palladium for the determination of arsenic using inductively coupled plasma-mass spectrometry

A dry ashing procedure is developed for the determination of As in organic rich matrices such as wheat flour, lichen and tobacco leaves. The volatility of As during dry ashing is avoided by the addition of palladium nitrate [Pd(NO₃)₂]. The recovery of both As(III) and As(V) is found to be near quantitative. The residue after dry ashing is dissolved in nitric acid (HNO₃) and analysed by inductively coupled plasma-mass spectrometry (ICP-MS). The process blank and limit of detection (LOD) are 11 and 6.6 ng g⁻¹, respectively. The procedure is applied for the determination of As in certified reference materials namely wheat flour NIST SRM 1567a (National Institute of Standards and Technology Standard Reference Material), lichen BCR CRM 482 (Institute for Reference Materials, European Commission) and Virginia tobacco leaves CTA-VTL-2 (Poland Academy of Sciences). The results obtained by the present procedure are in good agreement with the certified values and also determined after complete dissolution of samples using closed microwave digestion.     

Extraction of antimony and arsenic from fresh and freeze-dried plant samples as determined by HG-AAS

Six extraction media (acetic acid, EDTA, tetrabutylammonium hydroxide, NaOH, MeOH/H₂O, acetonitrile/H₂O) were tested for their ability to extract antimony (Sb) and arsenic (As) from freeze-dried poplar leaves, pine shoots and spruce shoots, as well as from a peat matrix. Additionally, the extraction efficiency of Sb and As in fresh and freeze-dried elder leaves and poplar leaves was compared. Total concentrations of Sb and As of aliquots (～220 mg) of the freeze-dried samples were analysed by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS) after open vessel digestion with adequate mixtures of nitric, sulfuric, hydrochloric, and perchloric acid. Three reference materials GBW 07602 Bush Branches and Leaves, GBW 07604 Poplar Leaves, and SRM 1575 Pine Needles were analysed with every batch of samples to ensure the accuracy and precision of the applied analytical procedures. The use of hydrofluoric acid in the digestion mixture leads to distinctly lower As values (down to 40%) than actual concentrations in the investigated plant materials. Extraction efficiencies were generally low and lower for Sb than for As. Solutions of 0.66 mol L^–1 NaOH liberated highest amounts of Sb with ～10% for poplar leaves, and ～19% each for pine shoots and spruce shoots. Distinctly higher concentrations of As in NaOH extracts of poplar leaves (22%), pine shoots (32%), and spruce shoots (36%) were quantified. Extraction experiments resulted in yields of 7–9% from fresh elder and poplar leaves, respectively, and 8–13% for freeze-dried samples for Sb. The corresponding values for As were 10–35% for the fresh material and 7–37% for the freeze-dried samples.     

Extraction of antimony and arsenic from fresh and freeze-dried plant samples as determined by HG-AAS

Six extraction media (acetic acid, EDTA, tetrabutylammonium hydroxide, NaOH, MeOH/H2O, acetonitrile/H2O) were tested for their ability to extract antimony (Sb) and arsenic (As) from freeze-dried poplar leaves, pine shoots and spruce shoots, as well as from a peat matrix. Additionally, the extraction efficiency of Sb and As in fresh and freeze-dried elder leaves and poplar leaves was compared. Total concentrations of Sb and As of aliquots (approximately 220 mg) of the freeze-dried samples were analysed by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS) after open vessel digestion with adequate mixtures of nitric, sulfuric, hydrochloric, and perchloric acid. Three reference materials GBW 07602 Bush Branches and Leaves, GBW 07604 Poplar Leaves, and SRM 1575 Pine Needles were analysed with every batch of samples to ensure the accuracy and precision of the applied analytical procedures. The use of hydrofluoric acid in the digestion mixture leads to distinctly lower As values (down to 40%) than actual concentrations in the investigated plant materials. Extraction efficiencies were generally low and lower for Sb than for As. Solutions of 0.66 mol L(-1) NaOH liberated highest amounts of Sb with approximately 10% for poplar leaves, and approximately 19% each for pine shoots and spruce shoots. Distinctly higher concentrations of As in NaOH extracts of poplar leaves (22%), pine shoots (32%), and spruce shoots (36%) were quantified. Extraction experiments resulted in yields of 7-9% from fresh elder and poplar leaves, respectively, and 8-13% for freeze-dried samples for Sb. The corresponding values for As were 10-35% for the fresh material and 7-37% for the freeze-dried samples.     

氢化物发生-原子吸收光谱法测定柠檬酸中微量铅

柠檬酸样品经硫酸处理及在550℃灼烧灰化,残渣溶于盐酸(5+95)溶液中。用铁氰化钾将溶液中铅(Ⅱ)氧化成铅(Ⅳ),然后再以硼氢化钾为还原剂,盐酸(1+99)溶液为载流,用氢化物发生-原子吸收光谱法测定铅含量。在优化的试验条件下,铅的质量浓度在20μg·L~(-1)以内与其吸光度呈线性关系,检出限(3σ)为2.6μg·L~(-1)。用此方法分析了3个柠檬酸样品,测定值的相对标准偏差(n=6)小于5%,加标回收率在90.5%～110.0%之间。     

Simultaneous determination of arsenic and selenium in biological samples by HG-AFS

A new method is proposed for simultaneous determination of traces of arsenic (As) and selenium (Se) in biological samples by hydride-generation double-channel non-dispersive atomic-fluorescence spectrometry (HG-AFS) from tartaric acid media. The effects of analytical conditions on fluorescence signal intensity were investigated and optimized. Interferences from coexisting ions were evaluated. Under optimum conditions linear response ranges above 20 g L^–1 for As and 32 g L^–1 for Se were obtained with detection limits of 0.13 and 0.12 g L^–1, respectively. The precision for elevenfold determination of As at the 4 g L^–1 level and of Se at the 8 g L^–1 level were 2.7 and 1.9% (RSD), respectively. Recoveries of 92.5–95.5% for As and 101.2–108.4% for Se were obtained for four biological samples and two certified biological reference materials. The proposed method has the advantages of simple operation, high sensitivity, and high efficiency; it was successfully used for simultaneous determination of As and Se in biological samples.     

赶酸对微波消解-氢化物发生-原子荧光法测定谷物中砷元素的影响

在利用氢化物发生-原子荧光分测定谷物类样品中砷元素时,硫脲-抗坏血酸的还原效果会受到硝酸含量的影响,试液中硝酸含量过高,会与硫脲-抗坏血酸溶液发生氧化还原反应,降低其还原效率。本研究通过对赶酸时间和赶酸温度进行试验,获得最佳的赶酸条件,结合微波消解技术,利用氢化物发生-原子荧光光谱法测定谷物中的微量砷,结果表明,谷物中砷浓度与荧光强度呈线性关系,线性方程为 y=0.0028x-0.1728,线性相关系数R2=0.9993,检出限为1.72ng/g。 通过对9份样品进行检测,其相对标准偏差RSD在4.32-7.59%之间,其准确度相对误差RE均小于±6.50%。经多次检测证实该方法较稳定,可用于谷物类样品中砷元素的快速测定。     

超声雾化-ICP-AES测定植物样品中的微量元素

研究了超声雾化-ICP-AES测定植物样品中As、Pb、Se、Bi、Ge、Mo的方法。对样品的测定条件进行了优化。在选定的仪器工作参数下,加标回收率达到95.5%~103%,RSD均小于3%。     

Use of hydride generation-atomic absorption spectrometry to determine the effects of hard ions, iron salts and humic substances on arsenic sorption to sorghum biomass

At present, there is a great interest in studying new sorbent materials for the removal of arsenic from aqueous solutions because of its high toxicity and adverse effects on human health. In previous research, sorghum biomass was found to be an efficient and economic sorbent for the removal of arsenic from aqueous solutions. In this investigation, the effects of CaCl₂, MgCl₂, FeSO₄, MgSO₄, Fe(NO₃)₃, and humic substances (peat moss, humin and humic acids) on arsenic binding to sorghum biomass were evaluated. Among these compounds, only iron salts were found to positively increase the sorption of arsenic to sorghum biomass. In addition, the sorption equilibrium was reached faster when the reaction mixture contained iron salts. However, an overall reduction of 21% of arsenic sorption to sorghum biomass was observed in the presence of MgSO₄. This interference may be due to the presence of sulfate ions, instead of the hard cations, that could be in competition with As for the same interaction sites or ligands. Peat moss, humins and humic acid, extracted from sphagnum peat moss, significantly decreased the arsenic sorption to sorghum biomass.     

氢化物发生电加热石英管原子吸收法测定包头铁矿中的砷、锑、铋

研究了氢化物发生原子吸收法测定包头矿中痕量砷、锑、铋的分析方法,试验确立了反应条件,建立了以KI、抗坏血酸、硫脲为还原体系,消除试样中共存元素的干扰,利用KMnO4消除锑对砷的干扰.砷、锑、铋的检出限可分别达到:0.15,0.28,0.15 ng/mL.方法已用于包头矿分析.     

Microwave-assisted digestion of organoarsenic compounds for the determination of total arsenic in aqueous, biological, and sediment samples using flow injection hydride generation electrothermal atomic absorption spectrometry

A microwave assisted wet digestion method for organoarsenic compounds and subsequent determination of total arsenic in aqueous, biological and sediment samples by means of flow injection hydride generation electrothermal atomic absorption spectrometry (FI-HG-ETAAS) is described. Sodium persulfate, sodium fluoride and nitric acid serve as digestion reagents, which allow a quantitative transformation of organoarsenic compounds to hydride forming species in a commercial microwave sample preparation system. The maximum operating pressures of the applied tetrafluorometoxil (TFM) liners are 75 bar (high pressure vessels) and 30 bar (medium pressure vessels), corresponding to maximum solution temperatures of 300 and 260 °C. For the investigated samples, digestion temperatures of 210-230 °C (medium pressure vessels) and 240-280 °C (high pressure vessels) were obtained.In medium pressure vessels, arsenic recovery from aqueous testing solutions of dimethylarsinic acid (DMA), phenylarsonic acid (PAA) and tetraphenylarsonium chloride (TPA) at initial concentrations of 100 and 10 μg l⁻¹ is complete, even in the presence of an excess of organic carbon (potassium hydrogen phthalate, 2000 mg l⁻¹) or fatty acids (linolenic acid 70%; linoleic acid ≈20-25%; Oleic acid ≈3%, 900-4500 mg l⁻¹).Arsenic recovery from aqueous arsenobetaine (ASB) solutions with the same initial concentrations is also complete if high pressure vessels and a higher concentration of fluoride ions are used, whereas the addition of organic carbon (potassium hydrogen phthalate, 2000 mg l⁻¹, fatty acids, 900-4500 mg l⁻¹) leads to a decrease in arsenic recovery of about 2-5%. In all cases, residual carbon contents are close to the limit of detection for the applied analytical method (15 mg l⁻¹).Results of arsenic analysis in reference standard materials revealed a significant dependence on the material’s nature (sediment samples, plant materials and seafood samples). Sediment samples and plant materials show recoveries for arsenic around 100% after a single-step digestion in medium pressure TFM liners. Seafood (fish/lobster/mussel samples) usually require either the use of high pressure vessels or a second digestion step, if medium pressure vessels are used.     

微波消解-氢化物发生原子荧光法同时测定土壤中的砷汞

建立了微波消解-氢化物发生原子荧光法同时测定土壤中As、Hg的分析方法。用体积分数35%的王水作为消解溶剂,在设定的微波消解条件下,可以将土壤中的As、Hg提取完全,有效解决了消解液中剩余酸过多的问题。方法用体积分数5%的HCl作为反应介质,20 g/L NaBH4作为还原剂。通过测定国家标准参考物质和加标回收实验,对方法进行了验证。已用于土壤中As、Hg的测定。