Determination of arsenic in sediments by chloride formation and d.c. plasma arc emission spectrometry

The sediment sample is heated in an induction furnace in hydrogen chloride—argon; arsenic trichloride evolved is trapped and then swept into a d.c. plasma arc. Calcium sulfate addition enhances the signals and suppresses interference from organic matter. The limit of detection is 15 ng As; the relative standard deviation is 3.4% (n = 10) for 1.5μg As₂0₃.     

Analysis of mineral suspensions by d.c. plasma emission spectrometry

Dilute aqueous suspensions of sub-sieve fractions of various minerals are analyzed for their major constituents by d.c. plasma emission spectrometry. In favourable cases (e.g., determination of zinc in sphalerite or smithsonite powders below 5 μm), the suspensions may be analyzed quantitatively simply by comparison with standard solutions, and with a relative error less than 10%. In other cases (e.g., determination of beryllium in beryl powders), the required element is so poorly atomized that the analysis is impossible, even when very fine-grained suspensions are used. As expected, the atomization efficiency for a particular element decreases with increasing particle size, and with increasing free energy of formation of its oxide at high temperatures. The region extending along the vertical branch of the plasma is a convenient excitation zone for suspensions containing elements that are difficult to atomize but the high background in this region limits the analytical possibilities.     

Some analytical characteristics of an argon—nitrogen d.c. plasma arc for emission spectrometry

A low-power d.c. plasma arc device was used to estimate the analytical characteristics of an Ar—N₂ plasma arc compared to those of an argon plasma arc. When the flow rate of added nitrogen was varied from 0 to 1 l min^-1, the Cd I 228.802-nm line showed a maximum signal-to-background ratio at a nitrogen flow rate of approximately 0.3 1 min^-1 which corresponds to 0.23% of the total argon flow rate. Ratios of the signal intensities with the Ar—0.23%N₂ and argon plasma arcs are given for the spectral lines of seventeen elements. Relatively higher ratios were found for the atom lines of the group VIII through IIIA elements in the periodic table. Better precision and lower detection limits were attained for aluminium and cadmium with the Ar—0.23%N₂ plasma arc than with the argon plasma arc.     

电感耦合等离子体原子发射光谱法测定铈矿中微量的砷、锑

采用过氧化钠熔融试样，用盐酸调节试液酸度，对电感耦合等离子体原子发射光谱（ICP－AES）法同时测定铈矿中微量砷和锑进行了研究，考察了铈基体及共存元素，试液酸度及介质等因素对砷和锑的光谱和非光谱影响。     

Determination of arsenic and antimony by microwave plasma atomic emission spectrometry coupled with hydride generation and a PTFE membrane separator

The performance of a microwave plasma torch (MPT) discharge atomic emission spectrometry (AES) system directly coupled with hydride generation (HG) for the determination of As and Sb has been studied. The argon MPT system can sustain a stable plasma over a wide range of carrier and support gas flow rates with optimum performance at 250 and 1450 ml min⁻¹, respectively. The presence of trace amount of water in the MPT discharge is found to affect the detection limits and the signal to noise ratio. A PTFE membrane separator is applied for hydride introduction and water rejection. In addition, the membrane cell separator also improves the signal to noise ratio by serving as a pressure buffer to minimize noise due to pressure fluctuation. Detection limits (3σ) of 8.1 and 3.2 ng ml⁻¹ are obtained with the analytical lines As I 228.812 nm and Sb I 259.809 nm, respectively at an MPT power of 135 W. The detection limits are improved when a concentrated sulfuric acid cell is placed after the membrane cell to further remove water. This double cell system yields detection limits of 5.3 and 2.1 ng ml⁻¹ for As and Sb, respectively under the same operating conditions. Linear dynamic ranges of three orders of magnitude could be obtained.     

Determination of arsenic by hollow-cathode emission spectrometry

The applicability of the hollow-cathode discharge source in the emission spectrometric determination of arsenic is described. Neutral and 10% nitric acid solutions, as well as solutions obtained by mineralization of biological materials, all containing 2.5 to 125 μg As cm^?3, were introduced into stainless steel cathodes, dried under i.r. radiation, and calcined in a muffle furnace; the loaded cathodes were then subjected to discharge. Acidic solutions were found to leach nickel from the steel of the cathode: this converted the analyte into thermally-stable nickel arsenide, thus minimizing losses. Matrix effects were small, and the r.s.d. was satisfactory (5–8%). The detection limit was 3 μg cm^?3.     

Determination of submicrogram amounts of tin by atomic absorption spectrometry with electrothermal atomization

The determination of tin is described with particular reference to the addition of organic compounds to the graphite tube for the suppression of interferences of other ions. Most were suppressed by adding 20 μl of 10% ascorbic acid to 20 μl of sample in the furnace. The method was used for the determination of tin in waste-waters and sediments.     

Determination of antimony,arsenic, bismuth and copper by inductively coupled plasma atomic emission spectrometry in the electrorefining of copper

Inductively coupled plasma atomic emissionspectrometry (ICP-AES) has been applied as a rapid and routine method for the analysis of process electrolytes in the electrorefining of copper. Antimony, arsenic, bismuth and copper have been selected as major electrolyte constituents. For these elements profound statistical studies of spectral and interelement effects have been carried out. For As, Bi and Sb two analyte wavelengths have been selected, and for Cu one relatively insensitive analyte line has been chosen due to the high Cu concentration in samples. Best analytical lines were: As at 193.759 nm, Bi at 306.772 nm, Sb at 206.833 nm and Cu at 216.953 nm. Multiple linear regression proved to be very capable in the search of the best analytical wavelength and identifying interfering elements. Using simple acid based standards all elements investigated can be determined separately in complicated matrices with satisfactory results. Differences between true values and measured values can be partly eliminated by appropriate calculational methods.     

蒸馏分离-电感耦合等离子体原子发射光谱法测定氰化样品中砷的含量

砷是黄金选冶过程中常见的元素之一,选冶过程中砷的存在在一定的程度上影响了黄金等贵金属的氰化浸出效果。选冶样品中砷含量的准确分析可以为黄金选冶提供可靠地数据,并且采用一定的方法避免选冶过程中砷存在的影响。本方法通过饱和溴水-硝酸-硝硫混酸强氧化剂处理含氰样品,一方面分解氰化物,另一方面将各种形式的砷氧化为五价离子;再通过加入溴化钠催化剂,用硫酸亚铁将五价砷还原为三价砷,在108℃条件下,通过蒸馏方式将三价砷蒸馏出来,利用电感耦合等离子体原子发射光谱仪测定砷的含量。通过实验得出本方法的检测限为0.0019%;方法的精密度RSD<2%;方法的准确度-加标回收实验范围为99.8%-100.9%;通过与溴酸盐滴定法之间对比,说明了结果的准确性是可靠地。     

Determination of arsenic, selenium, and antimony in cloud water by inductively coupled plasma mass spectrometry

The capability of inductively coupled plasma mass spectrometry in determining trace levels of As, Se, and Sb in cloud water was evaluated. Preliminary studies focused on identifying and eliminating potential interferences in the cloud water matrix, the choice of appropriate internal standards, and system optimization. The detection limits for As, Se, and Sb were 20, 100, 20 pg/mL using pneumatic nebulization, and 5, 25, 5 pg/mL, respectively, using ultrasonic nebulization with a precision of better than 5% RSD. The accuracy was demonstrated by the analysis of a NIST commercial reference material, SRM 1643d. In all cases, the results from ICP-MS analysis agreed within 4% of the certified values. Comparative analysis of cloud water samples obtained from a site downwind from large pollution sources (Whiteface Mountain, New York) and Changlagali Pakistan, a rural mountain peak, was carried out by hydride generation atomic absorption (HGAA) spectrometry. There was excellent agreement between the ICP-MS and HGAA results.     

Determination of arsenic, selenium, and antimony in cloud water by inductively coupled plasma mass spectrometry

The capability of inductively coupled plasma mass spectrometry in determining trace levels of As, Se, and Sb in cloud water was evaluated. Preliminary studies focused on identifying and eliminating potential interferences in the cloud water matrix, the choice of appropriate internal standards, and system optimization. The detection limits for As, Se, and Sb were 20, 100, 20 pg/mL using pneumatic nebulization, and 5, 25, 5 pg/mL, respectively, using ultrasonic nebulization with a precision of better than 5% RSD. The accuracy was demonstrated by the analysis of a NIST commercial reference material, SRM 1643d. In all cases, the results from ICP-MS analysis agreed within 4% of the certified values. Comparative analysis of cloud water samples obtained from a site downwind from large pollution sources (Whiteface Mountain, New York) and Changlagali Pakistan, a rural mountain peak, was carried out by hydride generation atomic absorption (HGAA) spectrometry. There was excellent agreement between the ICP-MS and HGAA results. Received: 31 July 1997 / Revised: 28 October 1997 / Accepted: 31 October 1997     

The determination of antimony and arsenic concentrations in fly ash by hydride generation inductively coupled plasma optical emission spectrometry

Hydride generation inductively coupled plasma optical emission spectrometry (HG-ICP-OES) was used in the determination of As and Sb concentrations in fly ash samples. The effect of sample pre-treatment reagents and measurement parameters used for hydride generation was evaluated. Due to memory effects observed, the appropriate read delay time was adjusted to 60 s resulting in RSDs 0.6% and 2.3% for As and Sb, respectively. The most suitable volumes of pre-reduction reagents for 10 mL of sample were 4 mL of KI/ascorbic acid (5%) and 6 mL of HCl (conc.). The determination of Sb was significantly interfered by HF, but the interference could be eliminated by adding 2 mL of saturated boric acid and heating the samples to 60 °C at least 45 min. The accuracy of the method was studied by analyses of SRM 1633b and two fly ash samples with the recovery test of added As and Sb. As high a recovery as 96% for SRM 1633b was reached for As using 193.696 nm with two-step ultrasound-assisted digestion. A recovery rate of 103% was obtained for Sb using 217.582 nm and the pre-reduction method with the addition of 2 mL of saturated boric acid and heating. The quantification limits for the determination of As and Sb in the fly ash samples using two-step ultrasound-assisted digestion followed with HG-ICP-OES were 0.89 and 1.37 mg kg⁻¹, respectively.     

Determination of tungsten by plasma emission spectrometry

The emission spectrum of tungsten in an inductively coupled Ar/Ar-plasma (ICP) was investigated and relative intensities of 17 lines listed. Among the lines tested, W I 400.875 nm and W 207.911 nm are recommended for steel analysis. Several others suffer from severe spectral interferences. The line W 400.875 nm is very sensitive, but interfered with by titanium and very high iron concentrations. The line W 207.911 nm requires careful determination of adjacent background, but can be used even with low-resolution instruments. The influence of RF power, nebulizing conditions, burner height, and acid concentration was tested and found to be small enough for simple control in routine work. Steels and other alloys containing 0.02-80% W were analysed.     

电感耦合等离子体发射光谱法测定粗二氧化碲中 铜、铅、锑、铋、砷和硒

粗二氧化碲作为碲精炼或碲化工产品生产的重要原料,其中共存元素铜、铅、砷、锑、铋、硒含量的准确测定对于生产过程质量控制和贸易结算具有重要意义,但目前没有粗二氧化碲中铜、铅、砷、锑、铋、硒含量检测的标准分析方法。采用王水和饱和氟化氢铵分解试样,在王水和酒石酸介质中,选用Cu 327.393 nm、Pb 220.353 nm、Sb 217.582 nm、Bi 223.061 nm、As 193.696 nm、Se 196.026 nm为分析谱线,采用电感耦合等离子体发射光谱(ICP-AES)法测定粗二氧化碲中铜、铅、锑、铋、砷和硒含量。各元素校准曲线的相关系数均大于0.999;铜、铅、锑、铋、砷和硒的检出限分别为0.0004%、0.0005%、0.0006%、0.0007%、0.0004%和0.0007%,定量检出限分别为0.0012%、0.0016%、0.0020%、0.0025%、0.0013%和0.0025%。按照实验方法测定5个粗二氧化碲样品中铜、铅、锑、铋、砷和硒,测定结果的相对标准偏差(RSD,n=7)为0.79%~4.8%,加标回收率为96.0%~103%。方法简单,精密度和准确度较高,可用于测定粗二氧化碲中铜、铅、砷、锑、铋、硒含量。     

Direct-reading d.c. arc spectrometry for rapid geochemical surveys

A technique developed for the rapid quantitative analyses of metals in large suites of silicate materials is described. A direct-reading emission spectrometer interfaced to a dedicated minicomputer is used with d.c. arc excitation. Sample, buffer and arc parameters were chosen to promote reproducible selective volatilization. By partial integration of the line emission for the volatile metals, the spectrum background contribution is reduced, improving line to background ratios and permitting both “volatile” and “nonvolatile” metals to be determined in one burn.Preformed electrode cups are used in a specially designed arc chamber which incorporates a gas jet for controlled atmosphere and arc stabilization, and permits automatic electrode alignment as well as rapid and efficient cleaning between samples. No adjustment of the electrodes is made during the burn.One standard only is required for calibration since the working curves are linear over the concentration ranges of interest and a method of background correction using this same standard is described.A high rate of analysis as well as good accuracy and precision is achieved for 21 metals.     

Determination of trace amounts of antimony in geological materials by atomic absorption spectrometry

For the determination of traces of antimony in rocks and soils, dried samples are heated with ammonium iodide to volatilize antimony triiodide, which is then taken up with 10% hydrochloric acid and extracted into TOPO-MIBK. Analysis is completed by atomic absorption spectrometry. The range is 1.0–40 p.p.m. Sb, the relative standard deviation being about 10–4%. Up to 20% iron and 2000 p.p.m. Cu, Pb, Zn. Sn, As or Hg do not interfere.     

The influence of non-easily ionized elements on emission intensities in a d.c. arc plasma

Higher concentrations of non-easily ionized elements (NEIE) increase the spectral line intensity of trace elements in the arc plasma. It was found that these additives do not greatly affect the evaporation processes of the trace elements. Changes in temperature, electron density and transport velocities together can optimize the excitation for particular atomic species. The importance of the investigations is to underline the possible application of NEIE in spectrochemical practice.     

Determination of arsenic and antimony in milk by hydride generation atomic fluorescence spectrometry

A highly sensitive procedure has been developed for total arsenic and antimony determination in milk samples by hydride generation atomic fluorescence spectrometry after microwave-assisted sample digestion. The discrete introduction of 2 ml of digested sample in the automated continuous flow hydride generation system allows us to reduce drastically the sample and HCl consume and to determine several elements from a same sample digestion. The method provides detection limits of 0.006 and 0.003 ng ml⁻¹, a sensitivity of 2390 and 2840 fluorescence units per ng ml⁻¹ for As and Sb respectively, and average relative standard deviation of 2.3% for As and 4.8% for Sb. The analysis of cow milk samples, obtained from the Spanish market evidenced the presence of As at concentration levels from 3.4 to 11.6 ng g⁻¹ and Sb levels from 3.5 to 11.9 ng g⁻¹, thus in a proportion near to 1:1, which is in contrast with the 10:1 natural ratio between As and Sb and could evidence the effect of the introduction of new alloys and polymer materials in the industrial process of milk. The method was validated by the comparison of data found for commercial samples by using the proposed procedure and reference methods based on dry-ashing and AFS, and microwave-assisted digestion and inductively coupled plasma mass spectrometry determination.