石墨炉原子吸收光谱法测定痕量钒的研究

本文采用石记原子吸收光谱对钒吸收线的特征，普通石墨管和热解石墨管中钒的原子化行为，灰化和原子化条件，基体效应等进行了研究，综合应用基体改进剂，光控升温和解石墨管技术，提高了电热原子吸收测定钒的灵敏度，特征质量为２４ｐｇ／０．００４４Ａ。     

石墨炉原子吸收法测定钢铁及合金中微量钒

探讨了石墨炉子吸收法测定钢铁及合金中微量钒的各种实验条件及影响因素。实验表明，采用热解涂层管与光控升温相结合并在温度稳定的情况下原子化，可改善信号峰形，提高灵敏度，消除记忆效应。方法用于钢铁及合金中钒的分析，结果令人满意。     

石墨炉原子吸收法快速测定钢中钒

研究了塞曼效应石墨炉原子吸收法测定钢中钒的条件,拟定了相应的方法,采用热解涂层石墨管,省去灰化阶段並延长原子化时间,从而消除了记忆效应、方法简单、快速、准确可靠。工作曲线的线性浓度范围为0.05—0.5微克/毫升。以基体匹配工作曲线法或     

热解石墨涂层石墨管在石墨炉原子吸收中的应用

热解石墨涂层石墨管在WFD-Y_3型原子吸收分光光度计上试用,经试验证明:采用2000℃或2109℃沉积温度,涂层厚度0.18—0.21毫米之间的热解石墨涂层石墨管使用寿命很长、重现性好、稳定性好。对高温元素如希土等使用热解石墨涂层石墨管的灵敏度比未涂层石墨管提高十倍左右。石墨炉原子吸收法是无火焰原子吸收分光光度法中最有前途的方法。环化所研制的Y_3型石墨炉能在4秒内升温到3000℃以上,为高温元素的分析打下了良好的基础。当时我们使用的石墨管是用哈尔滨电碳厂生产的高强,高密、高纯石墨制成。我们使用竖向表皮层来车制石墨管,其余部位不能使用,但这和石墨管分析高温元素时寿命不长。L＇vov等人指出,热解石墨就下述特性优于普通石墨:高的升华点;较强的抗氧化性能     

石墨炉原子化器中原子化过程的研究(Ⅱ)——基体对铝原子化的影响

本文研究了在热解石墨管(PGT)、涂钨(WPGT)和涂锆(ZrPGT)热解石墨管中,氯化物基体等对铝原子吸收信号的影响,讨论了干扰机理。     

石墨炉原子吸收法中热解涂层石墨管在无标准分析法测定环境样品中铬的应用

本文探讨了热解涂层石墨管测定铬的最佳实验条件,研究了各种酸和干扰物质的基体效应,提出用浓氨水为基体改进剂克服高氯酸的干扰。比较了各原子化温度时的理论和实验特征量。使热解涂层石墨管有可能用于无标准分析法测定各种环境样品中的铬。     

用衬钨钽金属热解石墨管原子吸收法测定稀土等十七个元素

用热解石墨管(PGT)测定稀土等高温元素存在着严重困难。为此,曾在石墨管中衬钽片测定了一些高温元素,但是未报道钽片的寿命和测定精密度。文献[2,3]采用上述方法测定稀土元素和铀,     

石墨炉原子吸收法测钡时石墨管性能的探讨

近年来,随着石墨炉原子吸收分析技术的发展和应用,使人们越来越深刻地认识到石墨管的性能对石墨炉原子吸收分析起着重要的作用,它直接影响分析方法的灵敏度、检出限和准确度。因此作者在进行石墨炉原子吸收法测钡时,同时观察了普通石墨管、热解涂层石墨管和全热介石墨管的性能,并将所得实验结果作了全面的比较。     

恒温炉中加热管材料对灵敏度的影响

恒温炉中加热管石墨表面结构和物理性质,直接影响分析试样的原子化行为。目前,利用热解涂层石墨管改善原子吸收分析灵敏度,已被人们重视并广泛应用^[1-2]。本文采用Woodriff炉做原子化器,对Al、K、Ag、Cd在普通石墨管和玻璃碳管中的原子化行为进行了研究,结果四种元素在玻璃碳管中的灵敏度均获得提高。     

石墨炉原子吸收分析中升温速率对灵敏度影响的研究

L'vov指出,商品石墨炉由于升温速率低,导致石墨管内空间温度低于石墨管壁温度,大量原子以分子形式丢失,因此产生较低的灵敏度,基体干扰严重,背景吸收也大,为此L'vov提出用快速升温技术克服以上缺点。而后Chakrabarti等用自制的快速升温电源研究升温速率对灵敏度的影响,指出快速升温电源为提高元素灵敏度,降低背景和基体干扰提供了良好的条件,但他们的工作只局限于全热解石墨管(简     

不同表面石墨管测定比较及采用WPGT直接测定水系沉积物及煤飞灰中的钇

本文采用自制的钨金属表面石墨管(WPGT)测钇,并与其它石墨管进行了比较。WPGT测钇灵敏度高,为PGT的340倍,重现性好,抗干扰能力强,可用于水系沉积物等样品中钇的直接测定。     

Determination of gallium by graphite furnace atomic absorption spectrometry with combined use of a tungsten-coated L'vov platform tube and a chemical modification technique

Tungsten-coated non-pyrolytic graphite (NPG), pyrolytic graphite (PG) and pyrolytic L'vov platform graphite (PPG) tubes were prepared, and their analytical performances were compared. The coating process simply involved injecting 100 μl of a sodium tungstate solution (0.01 mol l⁻¹) into each graphite tube, followed by heating according to a temperature programme similar to an atomisation cycle for the determination of gallium. This procedure for coating was repeated at least 12, 25, and 7 times towards NPG, PG, and PPG tubes, respectively. Among these tubes, the tungsten-coated PPG tube showed excellent performance for the determination of gallium. By combined use of a chemical modifier such as aluminium(III) or nickel(II) a detection limit (3σ) of 6 pg and sensitivity (1% absorption) of 3–4 pg were achieved. The practical potential of the proposed technique was demonstrated for the determination of gallium in several samples of alloys and fresh water.     

Comparison of uncoated, pyro-coated and totally pyrolytic graphite tubes for the HGA-500 electrothermal atomiser

The analytical performance of three uncoated electrographite tubes, three pyro-coated electrographite tubes, one tantalum carbide (TaC) coated electrographite tube, and three totally pyrolytic graphite (TPG) tubes has been evaluated and compared. A test programme was devised to determine the useful operational lifetime of each tube, and assess the influence of tube age on the sensitivity of lead, manganese and vanadium measurements by atomic absorption spectrometry. The TPG tubes were found to be more durable than the other types studied, but the lifetime advantage depended on the thickness of the pyrolytic graphite. The best TPG tube, of 720 μm wall-thickness, lasted 2.5 times longer than the pyro-coated tubes, and 5 times longer than the uncoated electrographite tubes.The TPG tubes gave slightly poorer AAS sensitivity for lead, equivalent sensitivity for manganese, and 4 times better sensitivity for vanadium than the pyro-coated electrographite tubes. Also, with TPG, signal magnitude was more consistent throughout the lifetime of a tube. For each of the test elements studied, poorest sensitivity was encountered with the TaC-coated electrographite tube.     

Selective determination of antimony(III) and antimony(V) with ammonium pyrrolidinedithiocarbamate, sodium diethyldithiocarbamate and dithizone by atomic-absorption spectrometry with a carbon-tube atomizer

The extraction behaviour of antimony(III) and antimony(V) with ammonium pyrrolidinedithiocarbamate, sodium diethyldithiocarbamate and dithizone in organic solvents has been investigated by means of frameless atomic-absorption spectrophotometry with a carbon-tube atomizer. The selective extraction of antimony(III) and differential determination of antimony(III) and antimony(V) have been developed. With ammonium pyrrolidinedithiocarbamate and methyl isobutyl ketone, when the aqueous phase/solvent volume ratio is 50 ml/10 ml and the injection volume in the carbon tube is 20 mul, the sensitivity for antimony is 0.2 ng/ml for 1% absorption. The relative standard deviations are ca. 2%. Interferences by many metal ions can be prevented by masking with EDTA. The proposed methods have been applied satisfactorily to determination of antimony(III) and antimony(V) in various types of water.     

Periodic trends in sensitivity and its dependence on the properties of pyrolytic and non-pyrolytic graphite in graphite-furnace atomic-absorption spectrometry

The sensitivities for metal determination by GFAAS in the peak-height and integration modes were examined with pyrolytic graphite (PG) and non-pyrolytic graphite (NPG) tubes for 34 elements. It was found that there are periodic trends of the mole sensitivity and the elements can be classified according to whether their sensitivity of determination is enhanced by use of (a) the PG tube (alkali, alkaline-earth and transition metals); (b) the NPG tube (semi-metals); about equally by both tubes (Mg, Zn, Cd, and Pb). The mole sensitivity pM for atomic-absorption spectrometry (AAS) was defined as pM = -log(m(h)/A(w)) where m(h) is the weight of an element corresponding to 1% absorption and A(w) is the atomic weight. It was found that the pM values for graphite furnace AAS have a periodic trend similar to that for flame AAS and atomic-fluorescence spectrometry.     

Selective determination of arsenic(III) and arsenic(V) with ammonium pyrrolidinedithiocarbamate, sodium diethyldithiocarbamate and dithizone by means of flameless atomic-absorption spectrophotometry with a carbon-tube atomizer

The extraction behaviour of arsenic(III) and arsenic(V) with ammonium pyrrolidinedithiocarbamate, sodium diethyldithiocarbamate and dithizone in organic solvents has been investigated by means of nameless atomic-absorption spectrophotometry with a carbon-tube atomizer. The selective extraction of arsenic(III) and differential determination of arsenic(III) and arsenic(V) have been developed. With ammonium pyrrolidinedithiocarbamate and methyl isobutyl ketone or nitrobenzene, when the aqueous phase/solvent volume ratio is 5 and the injection volume in the carbon tube is 20 μl, the sensitivities for 1% absorption are 0.4 and 0.5 part per milliard of arsenic, respectively. The relative standard deviations are ca. 3%. Interference by many metal ions can be prevented by masking with EDTA. The proposed methods are applied satisfactorily for determination of As(III) and As(V) in various types of water.     

Electroanalytical Exploitation of Nitroso Phenyl Modified Carbon‐Thiol Interactions: Application to the Low Voltage Determination of Thiols

The electrochemical generation of nitrosophenyl groups covalently attached to graphite powder (nitrosophenylcarbon) from carbon powder chemically modified with nitrophenyl groups and their subsequent reaction with thiols (glutathione, cysteine and homocysteine) has been investigated as a method by which the later can be quantified. The modified carbon powder was immobilized onto a basal plane pyrolytic graphite electrode and characterized by cyclic voltammetry by scanning between 1.0 V and ?1.0 V vs. SCE in phosphate buffer (pH 7). Square wave voltammetry (SWV) was used for the determination of thiols and the SWV parameters were optimized. The nitrosophenylcarbon is electrogenerated from nitrophenylcarbon and can chemically oxidize thiols to disulfides. Subsequent reduction of nitrosophenylcarbon to phenylhydroxylaminecarbon during the square wave voltammetric process leads to a decrease in the reductive current. This can be correlated to the concentration of thiol present within the medium. The cyclic voltammetric responses of basal plane pyrolytic graphite electrode, edge plane pyrolytic graphite electrode, glassy carbon electrode and boron‐doped diamond electrode in the direct oxidation of thiols were also investigated and all were found to have a significantly higher overpotential compared to the described method using nitrosophenylcarbon.     

Determination of phosphorus in steel with a stabilized-temperature graphite furnace and zeeman-corrected atomic absorption spectrometry

The determination of phosphorus in steel by graphite furnace a.a.s. is plagued by a spectral interference from the iron matrix which results in overcompensation when a continuum-source background corrector is used. Zeeman background correction using an alternating transverse magnetic field at the furnace eliminates this problem and allows a routine determination of phosphorus down to 0.002% in steel. Lanthanum is an effective matrix modifier for the phosphorus determination, but its enhancing effect depends largely upon the tube material used and the sample matrix. A 0.2% lanthanum solution was found to be optimum. The stabilized-temperature platform furnace concept allows an interference-free determination of phosphorus in steel, down to 0.002%, directly against aqueous standards. Atomizing the sample from a pyrolytic graphite platform in an uncoated graphite tube provides the optimum environment for a phosphorus determination.     

Determination of Cadmium and Lead in Sea Water after Extraction Using Electrothermal Atomisation. Minimisation of Interferences from Co-Extracted Sea Salts

Abstract

Interferences from small amounts of sea salt in the determination of cadmium and lead were investigated. Test samples were made to mimic solutions obtained after extraction of sea water for trace metal analysis. Sea salt concentrations in the range 0–400 mg/l were investigated. Background absorption from this salt was high but easily minimised through the addition of nitric acid (2 % v/v). Sensitivity reductions due to the salt were considerable and varied from one graphite tube to the other. This problem was overcome by the addition of 1000 mg lanthanum per litre of sample. The positive effect of the lanthanum matrix modification is thought to be due to a change of the graphite tube surface.