AB-DTPA浸提-原子荧光法测定土壤中有效砷和有效硒

硒和砷是土壤中重要元素,目前关于提取测定有效硒和有效砷的报道还比较缺乏。本文采用原子荧光光谱法,以AB-DTPA为浸提剂,建立了一种准确测定本地区土壤中有效硒和有效砷的分析方法。通过考察浸提剂加入量,即土液比（m/v）;浸提时的振荡时间和振荡频率的影响,确立了适用于本地区土壤有效硒和有效砷提取分析的有效方法,结果表明：随着浸提剂的不断加入,所测土壤中有效硒和有效砷含量逐渐增大,当土壤称样量和浸提剂使用体积比为1:5时,所测土壤有效硒和有效砷含量最高,继续加入浸提剂后形成稀释效应导致测量结果偏低,故将土液比（m/v）定位1:5;当振荡时间不断增大时,所测所测土壤中有效硒和有效砷含量逐渐增大,振荡时间在30min时,浸提效果最佳,继续增加振荡时间到50min时对浸提效果影响不大,故将30min确立为最佳振荡时间;随着振荡频率的增大,有效硒和有效砷提取量逐渐增加,振荡频率在90-130r/min之间时,浸提效果最好,继续增大振荡频率,所测土壤中有效硒和有效砷含量变化不大。通过上述条件探索,选取五种土壤标准物质（GBW07441,GBW07442,GBW07443,GBW07444,GBW07445）进行验证,结果表明五种不同的土壤标准物质中有效硒和有效砷含量测定值准确,测定误差在-2.84~1.03mg/Kg,相对标准偏差为5.32%~8.85%,精密度和准确度均满足国家相关标准要求。     

原煤中有效态砷的提取方法

以1.0 mol/l,HNO3作为提取剂,用氢化物发生.原子荧光法(HG-AFS)测定提取液中砷的含量,建立了原煤中有效态砷的提取方法.考察了提取剂浓度、超声提取时间、液固比对原煤中有效态砷的提取效果的影响,在提取剂HNO3浓度为1 mol/L,超声提取时间1 h,液固比为15:1时提取效果最好.样品加标回收率为95.8%～98.O%.方法的线性范围为20～100 ng/mL,相关系数为0.9999,检出限为0.63 ng/mL(3σ,n=11).     

直接火焰原子吸收法测定石灰性土壤中有效态铜镉铅锌

土壤中有效态金属系指能被植物吸收的金属,它与植物及人体关系极为密切,对其进行监测在污染评价中很有意义。有效态金属常用浸提剂浸提后进行测定。浸提剂种类很多。近年来已有报导,将 DTPA 浸提剂用于碱性或石灰性土壤中有效态镉、铅、铜、锌的测定,其提取量与植物体中的量具有较好的相关性。本文以北京地区石灰性土壤为试样,试以 DTPA 为浸提剂,对浸提剂浓度、浸提时间、土水比及直接火焰原     

SDS对镍在HNO3/Cl-/H2O体系中电化学振荡行为的影响

阴离子表面活性剂十二烷基硫酸钠(SDS)能够控制金属镍在0.5 mol•L-1 HNO3/0.005 mol•L-1 Cl-/H2O溶液中的电流振荡行为. 在电流振荡过程中, 镍电极微分电容和电导等均出现明显的振荡特性. 随着SDS浓度的增大, 镍表面微分电容和溶液电导振幅等值均逐渐减小. 并且对SDS在镍电流振荡和钝化过程中的作用原理给予解释.     

酸度对氢化物发生-原子荧光光谱法测定砷镉汞铅硒的影响

对用氢化物发生-原子荧光光谱法测定砷、镉、铅、汞、硒五元素时,溶液酸度对相关元素荧光强度的影响进行了试验,并提出了测定各元素时的最佳条件,所述酸度实际是指原子化前试液的综合酸度。试验结果表明,测定铅的溶液酸最严格,应控制在cHNO30．20～0．22 mol·L-1之间,与此相比,测定镉的酸度范围较宽,可允许在cHCl 0．20～0．31 mol·L-1范围内。而对砷、硒、汞的测定,酸度的影响最小,依次在cHCl>0．1 mol·L-1,cHCl>0．12 mol·L-1及cHNO3>0．16 mol·L-1的酸度条件下均能获得满意结果。     

海产品油脂中无机砷提取方法的优化研究

目前海产品中测定无机砷的主要方法是原子荧光光谱法,而无机砷的提取是至关重要的一步。本文在GB 5009.11-2014的基础上,综合了水浴和超声波振荡两种提取方法,选择6mol·L~(-1)的盐酸作为浸提液,建立了盐酸浸提-水浴超声提取法,进一步优化了试样的提取方法,以满足海产品中无机砷含量准确测定的需要。试验结果发现,水浴超声提取法是一种新的适用于海洋性动物油脂的无机砷检测的预处理方法,样品的加标回收率和精密度均要高于水浴振荡法。海产品油脂中无机砷的最佳提取条件为:60℃水浴下超声提取1h。     

高速逆流色谱分离金果榄中巴马亭

用高速逆流色谱分离金果榄中巴马亭,以氯仿∶甲醇∶0.2mol·L-1盐酸(2∶1∶1)溶剂体系,上相为固定相,下相为移动相,流速2ml·min-1,仪器转速800r·min-1,进样量100mg,2h后分离出了16.8mg巴马亭(组分Ⅱ),并经HPLC测定,组分纯度>99.6%,并由UV、IR、MS和1H NMR确定结构。     

钙对氟污染酸性土壤的改良效应

对珠三角典型土壤（潮土和水稻土）加入一系列硝酸钙、氧化钙和碳酸钙进行室内培养,采用连续化学提取方法对原土及添加上述成分后各种形态氟进行提取,并采用极谱测定方法进行检测,研究各形态的转化行为。试验结果表明：加入氧化钙和碳酸钙可使两种土壤pH值明显上升,有利于改善土壤酸性;但使两种土壤有效态氟（水溶态氟、可交换态氟）含量上升,而铁锰结合态氟总体下降。故氧化钙不适用于该类高氟土的酸性改良,而碳酸钙的适用性则由土壤理化性质决定。硝酸钙的加入使各形态氟含量均呈下降趋势,在施用剂量大于20mg／25g时,对土壤中有效态氟有较好的抑制作用,但对土壤酸化没有改善。     

Mehlich3方法测定土壤养分的影响因素研究

Mehlich 3浸提剂被应用于浸提测定土壤多种有效养分,但对方法的影响因素研究报道较少。选择重庆紫色土和河北的潮土两种土壤样品,采用正交试验设计L9( 34 )正交试验,设置液土比（A）、振荡时间（B）、振荡温度（C）、浸提液pH（D）四个因素,对Mehlich 3法的浸提条件进行研究,浸提液使用电感耦合等离子发射光谱仪测定元素含量。结果表明：对于土壤中的养分浸提影响因素依次为浸提液pH＞浸提液体积＞振荡时间＞振荡温度,结合经济效益以及显著性,综合各因素最优组合为A1B1C1D1,即加入pH为2.5的浸提液25 mL,在25 ℃下振荡5 mim。该方法除B元素外,其他元素测定值的相对标准偏差RSD%小于5%,精密度良好。     

氟离子-乳酸-丙酮-Mn^2＋-BrO3^——H2SO4振荡反应及其在分析中的应用

氟离子对乳酸-丙酮-Mn2+-BrO-3-H2SO4化学振荡反应的周期和振幅有显著的影响,F-的浓度在8.00×10-5～1.00×10-3 mol·L-1范围内与振荡反应周期的改变值△tp和振幅的改变值△H均有良好的线性关系,是一线性范围宽、灵敏度高的动力学分析测试体系.获得振荡反应诱导期、周期的表观活化参数Ein、Ep分别为55.71 kJ·mol-1、67.41 kJ·mol-1,探索了该振荡体系可能的反应机理.     

超高效液相色谱-串联质谱法测定水稻基质中阿维菌素残留量

建立了超高效液相色谱-串联质谱法(UPLC-MS/MS)测定水稻基质中阿维菌素残留量,考察了基质效应,并对实际样品进行了检测.稻田土、稻壳、糙米和稻杆经乙腈振荡提取,稻田水经乙酸乙酯液液分配提取后,用C18固相萃取小柱或弗罗里硅土柱净化,采用UPLC-MS/MS正离子扫描测定残留的阿维菌素.稻田土、稻田水和糙米的3种添加浓度(1.0,10.0和100 μg/kg或μg/L)的平均回收率为84％～107％,相对标准偏差为4.7％～13.6％.稻壳和稻杆的2档添加浓度(10.0和100 μg/kg)的平均回收率为90％和103％,相对标准偏差为8.4％～12.9％.本方法在稻田水、糙米和稻田土中的检出限为0.3μg/kg在稻壳和稻杆中检出限为3.0 μg/kg,低于欧盟和日本在稻米中制定的阿维菌素最大残留限量值.阿维菌素在2.0～100 μg/L范围内线性关系良好( r＞ 0.999).     

液相色谱-电感耦合等离子体质谱法测定稻米中的5种砷形态

建立了稻米中砷酸根[As（Ⅴ）]、亚砷酸根[As（Ⅲ）]、砷甜菜碱（AsB）、一甲基砷（MMA）和二甲基砷（DMA）的液相色谱-电感耦合等离子体质谱（LC-ICP-MS）检测方法。以0.3 mol/L硝酸水溶液为提取试剂,样品在石墨消解仪中于95 ℃消解1.5 h,上清液供LC-ICP-MS分析。5种砷形态采用Dionex IonPac AS19阴离子交换柱（250 mm×4 mm）分离,经ICP-MS检测。比较了4种提取液对稻米中5种砷形态的提取效率,并对提取溶剂的浓度、提取温度和提取时间等条件进行了优化。通过加标回收试验结合测定标准物质考察了方法准确度及精密度,在2个加标水平上各形态的回收率为89.6%~99.5%,RSD（n=5）不大于3.6%,大米标准物质中各形态之和的测定结果与其标准值吻合,5种砷形态的线性范围AsB和DMA为0.05~200 μg/L,As（Ⅲ）和MMA为0.10~400 μg/L,As（V）为0.15~600 μg/L,方法检出限为0.15~0.45 μg/kg。结果表明,本方法简单、灵敏、耐用,可用于稻米中5种砷形态的准确定量和风险评估。     

Comparison of mild extraction procedures for determination of plant-available arsenic compounds in soil

In this work three mild extraction agents for determination of plant-available fractions of elements in soil were evaluated for arsenic speciation in soil samples. Pepper (Capsicum annum, L.) var. California Wonder was cultivated in pots, and aqueous solutions of arsenite, arsenate, methylarsonic acid, and dimethylarsinic acid, at a concentration of 15 mg As kg^–1 soil, were added at the beginning of the experiment. Control pots (untreated) were also included. Deionized water, 0.01 mol L^–1 CaCl₂, and 0.05 mol L^–1 (NH₄)₂SO₄ were used to extract the plant-available fraction of the arsenic compounds in soil samples collected during the vegetation period of the plants. Whereas in control samples the extractable arsenic fraction did not exceed 1% of total arsenic content, soil amendment by arsenic compounds resulted in extraction of larger amounts, which varied between 1.4 and 8.1% of total arsenic content, depending on soil treatment and on the extracting agent applied. Among arsenic compounds determined by HPLC–ICPMS arsenate was predominant, followed by small amounts of arsenite, methylarsonic acid, and dimethylarsinic acid, depending on the individual soil treatment. In all the experiments in which methylarsonic acid was added to the soil methylarsonous acid was detected in the extracts, suggesting that the soil bacteria are capable of reducing methylarsonic acid before a further methylation occurs. No significant differences were observed between analytical data obtained by using different extraction procedures.     

Extraction and speciation of arsenic in plants grown on arsenic contaminated soils

A sequential arsenic extraction method was developed that yielded extraction efficiencies (EE) that were approximately double those using current methods for terrestrial plants. The method was applied to plants from two arsenic contaminated sites and showed potential for risk assessment studies. In the method, plants were extracted first by 1:1 water-methanol followed by 0.1 M hydrochloric (HCl) acid. Total arsenic in plant and soil samples collected from contaminated sites was mineralized by acid digestion and detected by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and hydride generation-atomic absorption spectrometry (HG-AAS). Arsenic speciation was done by high performance liquid chromatography coupled with HG-AAS (HPLC-HGAAS) and by HPLC coupled with ICP-mass spectrometry (HPLC-ICP-MS). Spike recovery experiments with arsenite (As(III)), arsenate (As(V)), methylarsonic acid (MA) and dimethylarsinic acid (DMA) showed stability of the species in the extraction processes. Speciation analysis by X-ray absorption near edge spectroscopy (XANES) demonstrated that no transformation of As(III) and As(V) occurred due to sample handling. Dilute HCl was efficient in extracting arsenic from plants; however, extraction and determination of organic species were difficult in this medium. Sequential extraction with 1:1 water-methanol followed by 0.1 M-HCl was most useful in extracting and speciating both organic and inorganic arsenic from plants. Trace amounts of MA and DMA in plants could be detected by HPLC-HGAAS aided by the process of separation and preconcentration of the sequential extraction method. Both organic and inorganic arsenic compounds could be detected simultaneously in synthetic gastric fluid extracts (GFE) but EEs by this method were lower than those of the sequential method. The developed sequential method was shown to be reliable and applicable to various terrestrial plants for arsenic extraction and speciation.     

Electroanalytical methods for determination of the metal content and acetic-acid-available metal fractions in soils

The pseudo-total and available arsenic, cadmium, and lead content of soils have been determined by stripping voltammetry with a hanging-mercury-drop electrode and by atomic absorption spectrometry with electrothermal atomization. For determination of pseudo-total metals microwave digestion with a mixture of HNO3 and HClO4, with and without addition of HF, was investigated. The single-extraction procedure with 0.43 mol L-1 CH3COOH, proposed by BCR, was used to assess the availability of metals in soils. The results obtained were validated by analysis of a certified reference material.     

The extraction and speciation of arsenic in rice flour by HPLC-ICP-MS

Several solvent mixtures and techniques for the extraction of arsenic (As) species from rice flour samples prior to their analysis by HPLC-ICP-MS were investigated. Microwave-assisted extraction using water at 80 °C for 30 min provided the highest extraction efficiency. Total recoveries of extracted As species were in good agreement with the total As concentrations determined by ICP-MS after microwave-assisted acid digestion of the samples. Arsenite [As(III)], arsenate [As(V)] and dimethylarsinic acid (DMAA) were the main species detected in rice flour samples.     

Speciation of arsenic in a contaminated soil by solvent extraction

Soil collected from a disused cattle dip in northern New South Wales was studied with the aim of developing an inexpensive, yet effective method for quantitative determination of arsenic(III), arsenic(V) and total organic arsenic in a contaminated soil. Hydrochloric acid extractions were used as a method for removal of the arsenic from the soil in a form suitable for speciation. It was found that the extraction efficiency varied with the ratio of soil to acid, and the concentration of the acid. Arsenic(III), as arsenic trichloride, was selectively extracted into chloroform from a solution highly concentrated in hydrochloric acid. This was followed by back-extraction of the arsenic into water. Total inorganic arsenic was determined in a similar manner after the reduction of arsenic(V) to the trivalent state with potassium iodide. Arsenic(V) was determined by the difference between the results for arsenic(III) and total inorganic arsenic. All analyses for the various arsenic species were performed by hydride generation-atomic absorption spectroscopy; concentrations of total arsenic in the soil were confirmed using X-ray fluorescence spectrometry. It was found that all the arsenic in the soil was present as inorganic arsenic in the pentavalent state. This reflects the ability of arsenic to interchange between species, since the original species in cattle dipping solution is arsenic(III).     

Differential determination of arsenic(III) and total arsenic using flow injection on-line separation and preconcentration for graphite furnace atomic absorption spectrometry

Arsenic(III) can be quantitatively extracted using sodium diethyldithiocarbamate (NaDDTC) as the complexing agent and C18 reversed phase packing as the column material for solid phase extraction. Arsenic(V) must be reduced to its trivalent oxidation state prior to extraction. A mixture of sodium sulphite, hydrochloric acid, sodium thiosulphate and potassium iodide was found to be optimum for on-line reduction. When the sorbent extraction is carried out without and with the addition of the reduction mixture, arsenic(III) and total arsenic can be determined sequentially by graphite furnace atomic absorption spectrometry with detection limits (3 σ) of 0.32 ng for As(III) and 0.43 ng for total arsenic. A 7.6-fold enhancement in peak area compared to direct injection of 40 μl samples was obtained after 60 s preconcentration. Results obtained for sea water standard reference materials, using aqueous standards for calibration, agree well with certified values. A precision of 5.5% RSD was obtained for total arsenic in a sea water sample (1.65 As). Results obtained for synthetic mixtures of trivalent and pentavalent arsenic agreed well with expected values.