A rapid approach for assessment of arsenic exposure by elemental analysis of single strand of hair using laser ablation-inductively coupled plasma-mass spectrometry

Application of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) as a method for identification of arsenic in a single hair strand was investigated. Using a single point ablation method detectability of ⁷⁵As and other two elements (²⁰⁸Pb and ⁶⁴Zn) were evaluated. Arsenic (⁷⁵As) signal is improved with enhanced laser ablation conditions. For the arsenic determination in hair single spots or single linear scans with enhanced laser ablation conditions described in the paper are satisfactory although  800 μm linear scans may be preferable. Arsenic levels in a single strand of hair from individuals who were chronically exposed to arsenic contaminated drinking water from a village in the Atacama Desert in northern Chile were determined by LA-ICP-MS. These results were satisfactorily correlated with total As concentration previously measured by hydride generation (HG)-ICP-MS. The sample throughput is high and it takes  3 min per each hair sample including mounting, focusing and analysis. LA-ICP-MS method can be used for the rapid identification and screening of toxic and nutritionally important elements in hair.     

Elemental analyses of soil and sediment fused with lithium borate using isotope dilution laser ablation-inductively coupled plasma-mass spectrometry

Quantitative analysis using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) remains challenging primarily due to the lack of appropriate reference materials available for the wide variety of samples of interest and to elemental fractionation effects. Isotopic dilution mass spectrometry (IDMS) is becoming the methodology of choice to address these issues because the different isotopes of an element represent near-perfect internal standards. In this work, we investigated the lithium borate fusion of powdered solid samples, including soils, sediments, rock mine waste and a meteorite, as a strategy to homogenously distribute, i.e. equilibrate the elements and the added isotopically enriched standards. A comparison of this methodology using two pulsed laser ablation systems (ArF* excimer and Nd:YAG) with different wavelengths as well as two ICP-MS instruments (quadrupole and double-focusing sector field) was performed. Emphasis was put on using standard equipment to show the potential of the proposed strategy for its application in routine laboratories. Cr, Zn, Ba, Sr and Pb were successfully determined by LA-ICP-IDMS in six Standard Reference Materials (SRMs) representing different matrices of environmental interest. Experimental results showed the SRM fused glasses exhibited a low level of heterogeneity (intra- and inter-sample) for both natural abundance and isotopically enriched samples (RSD <3%, n = 3, 1σ). A good agreement between experimental results and the certified values was also observed.     

Modelling the temporal intensity distribution in laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) using scanning and drilling mode

Signal equations basing on dispersion functions describing the measured temporal intensity distribution for laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) used in scanning and drilling mode are developed. Variable ablation rates due to either varying focussing conditions typical for drilling mode and due to the changes of physical and chemical properties in inhomogeneous samples as typically investigated in scanning mode are considered for. The model accounts for intermixing of the sample aerosol within the sampling chamber, the influence of transport in a cylindrical transport channel and the fact that normally not the entire vapour generated and transported to the ICP can be observed. The absolute signal response is influenced by the actually ablated, transported and observed analyte mass. The dispersion functions describing the relative signal response depend on sample chamber volume, the volume of the transport channel, the laser shot frequency, the carrier gas flow rate and the part of observable cross-section at the MS interface compared to the entire cross-section filled by the vapour. All these parameters depend on the experimental set-up and the selected operating conditions only. Using the signal equation the influence of all mentioned parameters on signal course is shown both theoretically and experimentally. The signal equation can be used for calculation of optimal experimental conditions.

On this basis, an algorithm is proposed providing the relative temporal distribution of any analyte with significantly higher temporal resolution than the measured temporal intensity distribution itself. Furthermore, usage of dispersion functions for investigation of a given transport system, for explanation of typical signal deviations, for the proof of homogeneous regions in a heterogeneous sample, for examination of changes in ablation rate and for investigation of fractionation effects is shown.     

Were Chinchorros exposed to arsenic? Arsenic determination in Chinchorro mummies' hair by laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS)

Chinchorros, a fishermen culture, who lived about 7000 years ago in the coastal region of the Atacama Desert in the northern outpost of present-day Chile, practiced an intricate system of mummification of their dead. The drinking water in this region is rich with arsenic, and the mummies were found in these arsenic endemic areas. Well preserved mummy hair samples provided a unique opportunity to explore the ancient arsenic exposure of the Chinchorros by laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) using a single hair strand without any elaborate sample preparation. Forty-six hair samples from mummies found in five burial sites around the Atacama Desert, Chile, were used for this study. After cleaning, hair strands were placed on mounting tape and ablated using a Nd-YAG UV laser coupled to ICP-MS. A suite of contemporary human hair from the same region with known arsenic concentrations was used for calibration of LA-ICP-MS. Satisfactory linear calibration functions were obtained for arsenic in hair. The method detection limit was 0.8 µg/g and the sample throughput for this method is ∼ 10 samples per hour. It appears that mummies from the Morro (Arica), Iquique and Camarones had the elevated concentration of arsenic in hair (AsH > 10 µg/g) in this sub-set of samples, where Morro had the broad distribution of As concentrations.     

Study of plasma parameters influencing fractionation in laser ablation-inductively coupled plasma-mass spectrometry

Methods permitting to test the influence of the matrix as well as of its local and temporal distribution on the plasma conditions in laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) are developed. For this purpose, the MS interface is used as plasma probe allowing to investigate the average plasma condition within the ICP zone observed in terms of temporal and spatial distribution of the matrix.     

Rapid survey analysis of polymeric materials by laser ablation-inductively coupled plasma spectrometry. An analytical note

An Nd-Yag laser (1064 nm) in combination with a multichannel emission spectrometer was used for rapid survey analysis of polymers and paints. A novel design feature of the ablation chamber was the incorporation of a graphite furnace to effect electrothermal pretreatments of samples. Transient emission signals were studied as a function of laser operating mode, laser duration and flashlamp energy.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria     

Multi-element analysis of compost by laser ablation-inductively coupled plasma mass spectrometry

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been applied to multi-element determination in compost samples. Since compost is a heterogeneous mixture of organic and inorganic materials, the influence of sample heterogeneity on the accuracy and precision of analysis was investigated. Several parameters related to the following were studied: laser (energy, laser-beam diameter, preablation. rastering speed, carrier-gas flow rate), sample preparation (use of compacted pellets, grinding time, particle size, sample amount, length of hydraulic press treatment, position of line scan), and the ICP-MS system (quantitative versus semiquantitative analysis, matrix-matched standards and liquid standards calibration). The main causes of imprecision in sample preparation were determined to be particle size and grinding time. The effect of sample heterogeneity on precision was also evaluated by using different test samples (pellets). For Ni, Zn and Pb, the greatest contribution to the total relative standard deviation (R.S.D.) was related to analyte determination. For Mn and Cu, sample heterogeneity and analyte determination contributed equally to the total R.S.D., whereas for Cr, Co, Cd and Hg sample heterogeneity accounted for most of the total R.S.D. A comparison of semiquantitative and quantitative analysis modes showed that better precision and very good agreement with certified reference material was obtained with the latter, but semiquantitative analysis could be a practical alternative. Although accuracy of results was improved with matrix-matched standards calibration the use of standard addition calibration with aqueous standards could be another possibility.     

Lead determination in whole blood by laser ablation coupled with inductively coupled plasma mass spectrometry

This work describes a simple procedure for blood lead level determination. The proposed method requires little sample pretreatment and subsequent direct analysis of a dried blood spot on a filter membrane using laser ablation coupled with inductively coupled plasma mass spectrometry (LA-ICP-MS). In general, LA-ICP-MS studies are somewhat limited by the lack of matrix-matched standards for calibration purposes. Here we describe aqueous standard calibration and matrix-matched calibration methods. This method was validated by analysis of the reference materials. With the matrix-matched calibration method, the recovery ranged from 97.8% to 112.8%, while the aqueous standard calibration method ranged 90.4% to 122.4%. The lower detection limit was estimated as 0.1 ng mL⁻¹. The determination precision, expressed as the relative standard deviation (RSD), was not worse than 10% for all results. A sample throughput of approximately 5 min per sample made it possible to rapidly screen a large number of samples.     

Uranium colloid analysis by single particle inductively coupled plasma-mass spectrometry

Uranium single particle analysis has been performed by inductively coupled plasma-mass spectrometry (ICP-MS) and the performances are compared with that provided by scanning electron microsopy and single particle counting. The transient signal induced by the flash of ions due to the ionisation of an uranium colloidal particle in the plasma torch can be detected and measured for selected uranium ion masses (²³⁸U⁺, ²³⁵U⁺ or ²⁵⁴[²³⁸U¹⁶O]⁺) by the mass spectrometer. The signals recorded via time scanning are analysed as a function of particle size or fraction of the studied element or isotope in the colloid phase. The frequency of the flashes is directly proportional to the concentration of particles in the colloidal suspension. The feasibility tests were performed on uranium dioxide particles. The study also describes the experimental conditions and the choice of mass to detect uranium colloids in a single particle analysis mode.     

Characterization of lead and lead leaching properties of lead glazed ceramics from the Solis Valley, Mexico, using inductively coupled plasma-mass spectrometry (ICP-MS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT)

Ingestion of relatively small amounts of lead is now recognized to cause significant neurological and cognitive effects in humans. Large quantities may be fatal, yet lead poisoning, especially of children, is still a major public health concern in many parts of the world. In rural Mexican communities lead oxide (PbO) is added to ceramic glaze as a fluxing agent, lowering starting firing temperatures to 500 °C. The purpose of this study is to characterize the lead chemical forms in ceramic glazes from the Solis Valley, Mexico, to investigate lead leaching properties of these ceramics, and to demonstrate the applicability of lead isotope signatures as a means of tracing lead source origins. Ceramics were collected from the rural village of Santa Maria de Canchesda, State of Mexico, Mexico. Dried liquid glazes, post-fired glaze material, and pure PbO were analyzed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFT). Results from DRIFT analysis indicate that PbO (1429 cm⁻¹ band) is the active form of lead found in liquid glazes and ceramics. Some shifting of 1429 cm⁻¹ PbO peak to lower wavenumbers occurs in post-fired ceramics, and this may be due to the formation of lead bisilicate during firing. Ceramics samples were leached in 0.02 M citric acid solution for 1 min, and leached lead concentrations were measured using inductively coupled plasma-mass spectrometry (ICP-MS). Lead concentrations in these leachates varied from 0.4-80.4 μg ml⁻¹, while the control pottery from the US leached only 0.1 μg ml⁻¹ lead. Elemental distributions on glaze surfaces were identified by laser ablation (LA)-ICP-MS. Nitric acid extracts of soils, teeth, and ceramic glazes were analyzed for lead isotope ratios (²⁰⁷Pb/²⁰⁶Pb vs. ²⁰⁸Pb/²⁰⁶Pb) using ICP-MS. Similarities of tooth and ceramic lead isotope ratios indicate that ceramics may be a substantial source of body lead burden in the Solis Valley. This study demonstrates the applicability of lead isotope ratios for lead source identification, and it identifies potential health risks from ceramic use induced lead toxicity within the Solis Valley.     

Gold colloid analysis by inductively coupled plasma-mass spectrometry in a single particle mode

Analysis in a single particle mode of gold colloids in water has been performed by inductively coupled plasma-mass spectrometry (ICP-MS). The signal induced by the flash of ions due to the ionization of a colloid in the plasma torch can be measured for the ions ¹⁹⁷Au⁺ by the mass spectrometer without interferences. The intensity of the MS signal is recorded in time scan. The recorded peak distributions were analysed as a function of the colloid size for five monodisperse colloids (80-250 nm). This study describes the experimental conditions to analyse gold colloids in a single particle mode. The size detection limit is around 25 nm corresponding to 0.15 fg colloids and one particle per ml may be detected during a 1 min time scan within standard procedure.     

碰撞池-电感耦合等离子体质谱法测定芝麻中痕量的锗

建立了碰撞池-电感耦合等离子体质谱法测定芝麻中痕量的锗元素(germanium , Ge)。采用微波消解,碰撞池(KED模式)-电感耦合等离子体质谱检测,在线引入内标元素铑(Rh),同时消解液中加入3%正戊醇增敏。结果 3 % 正戊醇可使_⁷⁴Ge的上机检测信号强度提高2.85倍,_⁷⁴Ge校正曲线线性相关系数为1.00000,检出限为0.0555 μg/kg,加标回收率为92.0%~106%,相对标准偏差(relative standard deviation, RSD%)为2.6%~4.3%。采用建立的方法测定7种国家标准物质,检测结果均在认定值范围内,RSD%为2.5%~8.8%。结论 该方法灵敏度高、准确,可实现批量检测,适用于芝麻中痕量锗的检测。     

External calibration strategy for trace element quantification in botanical samples by LA-ICP-MS using filter paper

The use of reference solutions dispersed on filter paper discs is proposed for the first time as an external calibration strategy for matrix matching and determination of As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr, V and Zn in plants by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS). The procedure is based on the use of filter paper discs as support for aqueous reference solutions, which are further evaporated, resulting in solid standards with concentrations up to 250 μg g⁻¹ of each element. The use of filter paper for calibration is proposed as matrix matched standards due to the similarities of this material with botanical samples, regarding to carbon concentration and its distribution through both matrices. These characteristics allowed the use of ¹³C as internal standard (IS) during the analysis by LA-ICP-MS. In this way, parameters as analyte signal normalization with ¹³C, carrier gas flow rate, laser energy, spot size, and calibration range were monitored. The calibration procedure using solution deposition on filter paper discs resulted in precision improvement when ¹³C was used as IS. The method precision was calculated by the analysis of a certified reference material (CRM) of botanical matrix, considering the RSD obtained for 5 line scans and was lower than 20%. Accuracy of LA-ICP-MS determinations were evaluated by analysis of four CRM pellets of botanical composition, as well as by comparison with results obtained by ICP-MS using solution nebulization after microwave assisted digestion. Plant samples of unknown elemental composition were analyzed by the proposed LA method and good agreement were obtained with results of solution analysis. Limits of detection (LOD) established for LA-ICP-MS were obtained by the ablation of 10 lines on the filter paper disc containing 40 μL of 5% HNO₃ (v v⁻¹) as calibration blank. Values ranged from 0.05 to 0.81  μg g⁻¹. Overall, the use of filter paper as support for dried aqueous standards showed to be a useful strategy for calibration and plant analysis by LA-ICP-MS.     

Analysis of lead in tooth enamel by laser ablation-inductively coupled plasma-mass spectrometry.

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used to determine the Pb/Ca ratios in the enamel of deciduous incisors, a biomarker of in utero Pb exposure, using pelletized bone certified reference materials (CRMs) as calibrants. The detection limit for Pb by LA-ICP-MS was 11 microg kg(-1) demonstrating an adequate sensitivity for Pb in the teeth of unexposed individuals (0.1-10 mg kg(-1)). The precision for the Pb/Ca ratios in NIST SRM 1486 Bone Meal was 3.4%. The correlation between Pb/Ca ratios obtained by LA-ICP-MS and those obtained by a digestion method was highly significant. We found one point calibration by a CRM was applicable for the quantification of Pb in tooth enamel. This method will be valuable for the assessment of in utero Pb exposure levels.     

电感耦合等离子体质谱(ICP-MS)法测定地质样品中Cu和Zn的干扰研究

电感耦合等离子体质谱(ICP-MS)法标准模式测定地质样品中Cu和Zn时,样品溶液中Ti在高温下易形成TiO⁺和TiOH⁺产生离子重叠干扰,使测定值偏离真值而影响测定结果。采用氢氟酸-高氯酸-硝酸消解、王水复溶样品,通过多级在线校正⁴⁶Ti¹⁶O⁺,消除TiO⁺和TiOH⁺离子重叠干扰,研究了单质Ti与⁴⁶Ti¹⁶O⁺、质荷比63、64、65、66离子间存在的关系,建立了一种电感耦合等离子体质谱(ICP-MS)法测定地质样品中Cu和Zn的分析方法。结果表明：单质Ti对Cu和Zn产生的干扰值与其质量浓度呈非简单的正相关性,TiO⁺产生的干扰离子质荷比65离子强度比63高,质荷比64离子强度比66高;⁴⁶Ti¹⁶O⁺对质荷比63、66离子干扰增量值与单质Ti质量浓度变化无关;^6...     

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。     

Determination of trace lead by hydride generation-inductively coupled plasma-mass spectrometry

A newly developed hydride generation-inductively coupled plasma-mass spectrometry (HG-ICP-MS) system was employed to determine trace amounts of lead in geological and biological samples. Laboratory-made single-stage and double-stage gas-liquid separators (GLSs) were investigated in order to replace the consumable membrane-GLS. Possible reasons were given why double-stage GLSs were superior over the single-stage ones according to the factors such as GLS volume and configuration, carrier gas inlet mode and flow rate. Interferences in liquid and vapor phase from concomitant ions and their products were investigated employing different flow mani-folds. Memory effects contributed to the blank values, but could be reduced employing a special wash protocol. Internal and external standardization were combined to improve the accuracy of the method, with bismuth as the internal standard according to its similarity with lead in the HG-ICP-MS system. Compared with ICP-MS and hydride generation-atomic fluorescence spectrometry (HG-AFS) methods, the system performance of HG-ICP-MS was characterized with improved detection limit to 0.002 ng/ml and acceptable short- and long-term stabilities. The linear dynamic range of this method was up to 50 ng/ml lead. Three Chinese national certified reference materials: poplar leaves, human hair and copper ore, were analyzed for method validation, and the results agreed well with the certified values. At last, the method was also employed to determine wide range of lead concentrations in lightweight limestone and nervous tissue samples from infants of albino rats with recoveries between 95 and 105% (n=10).     

Quantitative images of metals in plant tissues measured by laser ablation inductively coupled plasma mass spectrometry

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used for quantitative imaging of toxic and essential elements in thin sections (thickness of 30 or 40 μm) of tobacco plant tissues. Two-dimensional images of Mg, Fe, Mn, Zn, Cu, Cd, Rh, Pt and Pb in leaves, shoots and roots of tobacco were produced. Sections of the plant tissues (fixed onto glass slides) were scanned by a focused beam of a Nd:YAG laser in a laser ablation chamber. The ablated material was transported with argon as carrier gas to the ICP ion source at a quadrupole ICP-MS instrument. Ion intensities of the investigated elements were measured together with ¹³C⁺, ³³S⁺ and ³⁴S⁺ within the entire plant tissue section. Matrix matching standards (prepared using powder of dried tobacco leaves) were used to constitute calibration curves, whereas the regression coefficient of the attained calibration curves was typically 0.99. The variability of LA-ICP-MS process, sample heterogeneity and water content in the sample were corrected by using ¹³C⁺ as internal standard. Quantitative imaging of the selected elements revealed their inhomogeneous distribution in leaves, shoots and roots.