High-throughput determination of seven trace elements in food samples by inductively coupled plasma-mass spectrometry

A method was developed for high-throughput determinations of 7 elements in food samples, namely antimony (Sb), arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), mercury (Hg), and tin (Sn). The samples were digested by closed-vessel microwave-assisted digestion using concentrated nitric acid (HNO3) as the medium, followed by microwave- assisted evaporation to concentrate the sample solutions before dilution to the desired volume. The microwave-assisted evaporation procedure effectively reduced the final acid concentration to around 8% before analysis by inductively coupled plasma-mass spectrometry (ICP-MS). This reduction allows determination by ICP-MS to proceed without further sample dilution, which would affect the detection limit. The method was validated, and method recoveries for As, Cd, Cr, Pb, and Hg were within the certified ranges of the chosen certified reference materials. Recoveries of the 7 elements from spiked samples ranged from 93.1 to 103.6%. The standard uncertainties of precision for the 7 elements were between 3.1 and 4.3%. Interlaboratory comparison studies for As, Cd, and Pb gave z-scores ranging from -0.2 to 0.3.     

微波消解-电感耦合等离子体质谱(ICP-MS)法测定拟黑多刺蚁中11种微量元素

为准确定量拟黑多刺蚁体内的微量元素,采用微波消解法,以HNO_(3)-H_(2)O_(2)混合酸为消解体系对样品进行前处理,选择合适的同位素,以^(103)Rh为内标测定^(52)Cr、^(55)Mn、^(60)Ni、^(63)Cu、^(66)Zn、^(75)As、^(78)Se、^(88)Sr和^(114)Cd,以^(185)Re为内标测定^(202)Hg和^(208)Pb,建立了电感耦合等离子体质谱法测定拟黑多刺蚁中11种微量元素的方法。实验发现,以HNO_(3)-H_(2)O_(2)为消解体系,样品消解完全;采用KED模式消除质谱干扰,以内标法校正基体效应;通过绘制校准曲线及测定流程空白,各元素校准曲线的相关系数均大于0.999,方法检出限为0.0005~0.011 mg/kg,方法定量限为0.0016~0.033 mg/kg。对拟黑多刺蚁实际样品进行测定,各元素的相对标准偏差(RSD,n=9)在1.2%~5.5%,加标回收率为91.2%~107%;经过实验室间比对实验,相对偏差为-3.15%~2.74%;测定六个不同产地的拟黑多刺蚁样品,结果显示不同产地样品除Cd外,其他10种微量元素的含量均存在较大差异。测定结果稳定可靠,能满足拟黑多刺蚁中11种微量金属元素含量的分析检测要求。     

Determination of trace elements in organic material by inductively coupled plasma-mass spectrometry

Summary For purposes of trace element analysis of organic materials a combined analytical procedure is tested. It consists of a pressure decomposition by nitric acid at 220° C in quartz vessels. The measurements are performed in the diluted digests by inductively coupled plasma/mass spectrometry. Analytical figures of merit are given.Dedicated to Prof. Dr. Karl Winsauer on the occasion of his 60th birthday.     

On the determination of platinum group elements in environmental materials by inductively coupled plasma mass spectrometry and microwave digestion

The interferences from Cd, Cu, Hf, Pb, Sr, Zn, Zr and Y on the inductively coupled plasma quadrupole mass spectrometry (ICP-MS) determination of Pt, Pd, Rh, Ru and Ir in geological (Pt-ore SARM-7, abundance range for platinum metals 0.07-3.74 μg/g) and environmental samples (sediment JSd-2 abundance range for Pt and Pd 0.0167-0.021 μg/g; road dust and plant sample) are evaluated using model solutions, real samples and comparison to inductively coupled plasma atomic emission spectrometry (ICP-AES) results. Pt, Rh, Ru and Ir can be determined usually after introduction of corrections for the interference in all investigated materials though in sediments the direct determination of Pt might be a problem depending on the actual Hf concentrations. The direct determination of Pd (after microwave-assisted acid digestion) is possible in ores using all investigated isotopes (, , ), in plants using and correction for the interferences of Zr, Mo and Cd, and not possible in sediments and road dust. Therefore, we developed a procedure for isolation of Pd using its diethyl-dithio-carabamate (DDTC) complex. The detection limits for Pt, Pd and Ir are 0.015 ng/g, and for Ru and Rh 0.03 ng/g.     

Multielemental determination in breast cancerous and non-cancerous biopsies by inductively coupled plasma-mass spectrometry following small volume microwave-assisted digestion

A microwave-assisted digestion method amenable to analysis of small size biological samples (<30 mg dry mass) has been optimized for determining twelve elements (Ag, As, Cd, Co, Cu, Cr, Mn, Mo, Ni, Pb, Se and Zn) by inductively coupled plasma-mass spectrometry (ICP-MS) in breast cancerous and non-cancerous biopsies. The use of three small volume PTFE closed vials (6-mL capacity) placed inside a conventional microwave vessel allows to drastically diminishing the volume of acid needed for digestion. A Plackett-Burman experimental design was used to evaluate the robustness of the digestion procedure. Effects of nitric acid volume, need for predigestion step, microwave power and digestion time were assessed. No significant effects were found, the digestion method being robust enough to be recommended for a routine practice. The method was successfully validated against CRM BCR 185 (bovine liver), CRM NRCC TORT-2 (lobster hepatopancreas), CRM NRCC DORM-2 (dogfish muscle) and CRM NRCC DOLT-2 (dogfish liver). Procedural detection limits ranged from 0.54 to 40 ng g(-1). Within-batch precision values were less than 3%, whereas between-batch precision values were in the range 2-11%. Forty-seven biopsies from thirty-nine women were analyzed: 20 samples corresponding to mammoplasties from healthy women and 27 samples from patients suffering from cancer pathology, 19 of which corresponded to tumour and 8 to adjacent normal tissue. After applying parametric and non-parametric statistical tests, a significant accumulation of Cu, Mn, Zn and Se in cancerous tissues was demonstrated.     

Neutron activation analysis and inductively coupled plasma-mass spectrometry for the determination of elements in tree stems

Mn, Zn and Al concentrations of ume, sakura and sugi stems determined by ICP-MS using a simple pretreatment were compared with those determined by INAA. We obtained a considerably good agreement between the two methods. ICP-MS using simple pretreatment was found to be useful in analyzing the elements in tree stems.     

Trace elements content in size-classified volcanic ashes as determined by inductively coupled plasma-mass spectrometry

At present there is an increasing concern as regards the release of potentially toxic metals into the environment. Volcanic eruptions are a natural source of metals and metalloids in the atmosphere. Toxic trace elements ejected during an eruptive episode may produce hazardous effects for people and the environment in areas close to the volcano. In this context, a study was undertaken to investigate the concentration of metal and metalloids in ashes ejected from Copahue volcano, Neuquén, Argentina. Two samples (A and B) of deposited particles were collected one day after the first eruption and size-fractionated in four sub-samples (S1, S2, S3 and S4). Analysis was performed by inductively coupled plasma-mass spectrometry (ICP-MS) and the accuracy for the entire analytical procedure was performed by means of the certified reference material CRM GBW 07105 Rocks (NRCCRM, China). The elements considered were: As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, U, V and Zn. The adverse effect of potentially interfering species on the mass-spectrometric determination of these elements was also taken into account. The concentration intervals found in the four fractions are as follows (in μg g⁻¹): As, 6.0-2.6; Cd, 0.71-0.36; Cr, 29.5-54.0; Cu, 132-49.0; Hg, 0.020-0.007; Ni, 36.0-26.0; Pb, 15.5-2.55; Sb, 1.07-0.30; U, 2.57-1.94; V, 152-106; Zn, 85.5-55.0. The elements with the highest concentrations were: Cu, V and Zn. All fractions, in both samples, were found to be enriched in some toxic trace elements in the following order Sb>Cd>As. On the contrary, samples were depleted in Ni, Cr and Hg. Lead was the element that exhibits a noticeable difference in concentration between the finer and coarser fractions.     

Iodine determination in food by inductively coupled plasma mass spectrometry after digestion by microwave-induced combustion

Iodine determination in food samples was performed by inductively coupled plasma mass spectrometry (ICP-MS) after digestion by microwave-induced combustion (MIC). Sample masses up to 500 mg of bovine liver, corn starch, milk powder, or wheat flour were completely combusted using the MIC system. Ammonium nitrate (6 mol l⁻¹ solution, 50 μl) was used as an aid for ignition and vessels were charged with 15 bar of O₂. The use of H₂O, 0.9 mmol l⁻¹ H₂O₂, 10 to 50 mmol l⁻¹ (NH₄)₂CO₃ and 56 mmol l⁻¹ tetramethylammonium hydroxide was investigated as absorbing solutions, as well as the suitability of performing a reflux step after the combustion process. Digestion of food samples by pressurized microwave-assisted acid digestion, microwave-assisted extraction and conventional extraction of iodine in alkaline solution were also evaluated. Iodine recoveries higher than 99% were obtained using MIC and 50 mmol l⁻¹ (NH₄)₂CO₃ or 56 mmol l⁻¹ tetramethylammonium hydroxide as absorbing solution and with 5 min for the reflux step. Accuracy was evaluated using certified reference materials (bovine muscle, corn bran, and milk powder) and agreement better than 97% was obtained. The limit of quantification by MIC and further ICP-MS determination was 0.002 μg g⁻¹. Blanks were always low and no memory effects were observed. Digestion by MIC allowed the processing of up to eight samples by each run in 25 min with high efficiency of digestion (residual carbon content lower than 1%) providing a suitable medium for further iodine determination by ICP-MS.     

Employing multivariate calibration for the determination of radionuclides by inductively coupled plasma-mass spectrometry

A method for the simultaneous ICP-MS determination of α- and β-emitting radionuclides in acid digested samples of concrete without further sample pretreatment is presented. Spectral and non-spectral interferences are corrected for by combining systematic internal standardization with bilinear multivariate calibration. Consequently, especially for radionuclides with long half-lives, ICP-MS is an alternative to radiometric analytical methods. The optimal multivariate calibration approach is the PLS1-model with preselected variables.     

Determination of selenium in red blood cells by inductively coupled plasma mass spectrometry (ICP-MS) after microwave digestion

Selenium is an essential trace element and its levels in blood have been widely used for assessing Se status in humans. The aim of this present study is to develop a suitable method for the determination of Se in red blood cells (RBC) using ICP-MS after microwave digestion. The blood samples were obtained from patients with benign prostatic hyperplasia (BPH), who attended urology clinics at the Princess Alexandra hospital, Brisbane, Australia. No apparent polyatomic and matrix interferences were encountered when ⁸²Se isotope was used for the analysis of Se levels in RBC. Whole Blood Seronorm Trace Elements (SERO, Norway) and dogfish muscle (DORM-1, NRCC) were used as reference materials for method validation. The method was rapid and accurate, and ideal for routine analysis of Se in RBC, and in particular for assessing of Se status in humans. This revised version was published online in August 2006 with corrections to the Cover Date.     

微波消解法-电感耦合等离子体质谱(ICP-MS)法测定韭菜中11种元素

为快速、准确测定韭菜中多元素含量,采用微波消解法对韭菜中样品进行消解处理,优化了前处理方法、ICP-MS工作条件和检测方法,利用微波消解-电感耦合等离子体质谱法测定韭菜中Pb、Cd、Se、As、Zn、Cu、Ni、Fe、Cr、Ca、K等11种元素含量。结果表明,在硝酸-双氧水(7:1)体系中,消解功率1550W,温度梯度为120℃-160℃-195℃,总时长为45min,赶酸温度选择150℃,可将韭菜完全消解,并且ICP-MS射频功率设为1550W,运用在线内标的检测方式降低非质谱干扰。11种元素回归系数R₂^{均大于0.999,方法检出限为}0.002～0.100μg/kg,方法定量限为0.006～0.300μg/kg。方法回收率88.0%～102.7%,相对标准偏差为1.8%～4.6%,可以满足韭菜中多种元素同时测定的需求。方法具有灵敏度高、线性范围宽、准确性高等特点,可为韭菜样品的多元素同时测定提供可靠的方法支撑。     

Multi-elemental analysis of marine sediment reference material MESS-3: one-step microwave digestion and determination by high resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS)

Single-step microwave digestion methods using four different acidic dissolving reagents were investigated with the main objective to obtain a simple, rapid method for multi-elemental analysis of marine sediment samples by high resolution inductively coupled plasma-mass spectrometry (HRICP-MS), especially for environmental studies. Closed-vessels microwave digestion procedures were carried out using the reagents as follows: HNO₃, mixture of HNO₃-HCl (φ _r = 9: 1), aqua regia, and mixture of HNO₃-HCl-HF (φ _r = 8: 1: 1). The elements analyzed were: Al, As, Ba, Be, Bi, Cd, Co, Cr, Cu, Fe, K, Li, Mn, Mo, Na, Ni, Pb, Sb, Sn, Sr, Ti, Tl, V, and Zn. Good recoveries were established for many of the metals analyzed even when only nitric acid was employed. However, for a good recovery of Sb and Tl, aqua regia should be employed.     

Microwave digestion of "residual fuel oil" (NIST SRM 1634b) for the determination of trace elements by inductively coupled plasma-mass spectrometry

A microwave procedure for the digestion of the NIST 1634b reference material "residual fuel oil" in closed pressurized vessels was developed in an attempt to facilitate routine analysis and obtain reproducible conditions or comparable results. The influence of sample size, reagent composition and volume, microwave power, and duration of heating on the digestion procedure was studied. Pressure and temperature inside the reaction vessels were monitored to determine the progression of the reaction and to develop optimal conditions. A nine-step heating program requiring 36.5 min with microwave power not exceeding 450 W in the pulsed mode was found suitable for the digestion of approximately 250 mg fuel oil with a mixture of nitric acid (5.0 mL) and hydrogen peroxide (2.0 mL). The reproducibility of microwave power was determined in terms of the relative standard deviations (n = 3) for temperature (2.7%) and pressure (4.9%) data. The vapor pressures obtained with 5.0 mL Milli-Q water (heated) in an 80-mL digestion vessel showed good agreement with literature data. The excess acid in the resulting digests was removed by evaporation and the concentrations of 24 elements (Ag, Al, As, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mo, Ni, Pb, Sb, Sn, Sr, Ti, Tl, V, U, and Zn) were determined in the diluted digests by inductively coupled plasma mass spectrometry (ICP-MS). The experimental results were in good agreement with the certified and recommended concentrations for eight elements (Al, As, Co, Cr, Ni, Pb, V, Zn) in solutions obtained after one digestion step. An additional digestion step, consisting of intermediate cooling and venting stages, was required for the accurate determination of Fe. No agreement was reached for Ca and Ba even after two-step digestion. The proposed method of digestion provided precise results with relative standard deviations generally less than 5% for most of the elements determined.     

Determination of elements in paints and paint scrapings by inductively coupled plasma atomic emission spectrometry using microwave assisted digestion

Summary Inductively coupled plasma atomic emission spectrometry (ICPAES) is applied to the determination of elements in paints and paint scrapings to evaluate potential occupational and environmental exposure to metals in paints. A microwave assisted digestion procedure of these materials using nitric and hydrofluoric acid mixtures under controlled pressure has been developed. The accuracy and repeatability of the recommended procedure for lead are documented and evaluated by analysing NIST SRM 1579 Powdered Lead Based Paint. Neutron activation analysis was applied as a reference method for other elements. A variety of industrial and domestic paints of different chemical composition were analysed. The advantages and limitations of microwave digestion of paints are discussed.     

电感耦合等离子体质谱法测定地球化学样品中镉

采用HF-HClO4-HNO3-H2SO4分解样品,王水提取,选用4个国家一级标准物质制备成标准系列校准,ICP-MS法直接测定地球化学样品中的Cd。选择103Rh为内标,确定了仪器的最佳分析条件,研究了Zr,Sn对Cd的干扰,选择114Cd作为测定同位素,采用数学公式校正了Sn对Cd的同质异位素干扰,方法检测限(3s)为6.3×10-3μg/g,RSD(n=12)为3.9%～6.6%。经国家一级标准物质验证,测定值与标准值吻合较好。该方法适用于地球化学样品中的微量Cd的测定。     

Determination of chromium, iron and selenium in foodstuffs of animal origin by collision cell technology, inductively coupled plasma mass spectrometry (ICP-MS), after closed vessel microwave digestion

The determination of chromium (⁵²Cr), iron (⁵⁶Fe) and selenium (⁸⁰Se) isotopes in foodstuffs of animal origin has been performed by collision cell technology (CCT) mode using an inductively coupled plasma mass spectrometry (ICP-MS) as detector after closed vessel microwave digestion. To significantly decrease the argon-based interferences at mass to charge ratios (m/z): 52 (⁴⁰Ar¹²C), 56 (⁴⁰Ar¹⁶O) and 80 (⁴⁰Ar⁴⁰Ar), the gas-flow rates of a helium and hydrogen mixture used in the hexapole collision cell were optimised to 1.5 ml min⁻¹ H₂ and 0.5 ml min⁻¹ He and the quadrupole bias was adjusted daily between −2 and −15 mV. Limits of quantification (LOQ) of 0.025, 0.086 and 0.041 mg kg⁻¹ for Cr, Fe and Se, respectively, in 6% HNO₃ were estimated under optimized CCT conditions. These LOQ were improved by a factor of approximately 10 for each element compared to standard mode.Precision under repeatability, intermediate precision reproducibility and trueness have been tested on nine different certified reference materials in foodstuffs of animal origin and on an external proficiency testing scheme. The results obtained for chromium, iron and selenium were in all cases in good agreement with the certified values and trueness was improved, compared to those obtained in standard mode.     

Microwave assisted digestion of atmospheric aerosol samples followed by inductively coupled plasma mass spectrometry determination of trace elements

A microwave digestion method in a closed vessel was developed for the determination of trace metals in atmospheric aerosols using inductively coupled plasma mass spectrometry (ICP-MS). A recovery study for the elements V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Sb, and Pb was conducted using multi-elemental standard solutions, NIST 1633b Trace Elements in Coal Fly Ash, and NIST 1648 Urban Particulate Matter. A simple digestion method using only HNO₃/H₂O₂ gave good recoveries (90%–108%) for all elements except Cr in SRM 1648, but yielded low recoveries for SRM 1633b. A more robust method using HNO₃/H₂O₂/HF/H₃BO₃ yielded higher recoveries (82%–¶103%) for the lighter elements (V – Zn) in SRM 1633b, and improved the Cr recovery in SRM 1648, but decreased the Se recovery in both SRMs. A comparative analysis of aerosol samples obtained at a remote mountain location Nathiagali, Pakistan (2.5 km above mean sea level), and Mayville, New York, downwind from the highly industrialized Midwestern United States, was carried out using Instrumental Neutron Activation Analysis (INAA) for the elements Cr, Mn, Fe, Co, Zn, As, Se, and Sb. The simple digestion method yielded excellent agreement for Cr, Fe, Zn, As, Se, and Sb, with slopes of the ICP-MS vs. INAA regressions of 0.90–1.00 and R² values of 0.96–1.00. The regressions for Mn and Co had slopes of 0.82 and 0.84 with R² values of 0.83 and 0.82, respectively. Addition of HF/H₃BO₃ did not improve the correlation for any of the elements and degraded the precision somewhat. The technique provides sensitivity and accuracy for trace elements in relatively small aerosol samples used in atmospheric chemistry studies related to SO₂ oxidation in cloud droplets. The ability to determine concentrations of a very large number of elements from a single analysis will permit source apportionment of various trace pollutants and hence strategies to control the sources of air pollution. This is particularly important as the health effects of particulate matter are increasingly recognized.     

Microwave assisted digestion of atmospheric aerosol samples followed by inductively coupled plasma mass spectrometry determination of trace elements

A microwave digestion method in a closed vessel was developed for the determination of trace metals in atmospheric aerosols using inductively coupled plasma mass spectrometry (ICP-MS). A recovery study for the elements V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Sb, and Pb was conducted using multi-elemental standard solutions, NIST 1633b Trace Elements in Coal Fly Ash, and NIST 1648 Urban Particulate Matter. A simple digestion method using only HNO3/H2O2 gave good recoveries (90%-108%) for all elements except Cr in SRM 1648, but yielded low recoveries for SRM 1633b. A more robust method using HNO3/H2O2/HF/H3BO3 yielded higher recoveries (82%-103%) for the lighter elements (V-Zn) in SRM 1633b, and improved the Cr recovery in SRM 1648, but decreased the Se recovery in both SRMs. A comparative analysis of aerosol samples obtained at a remote mountain location Nathiagali, Pakistan (2.5 km above mean sea level), and Mayville, New York, downwind from the highly industrialized Midwestern United States, was carried out using Instrumental Neutron Activation Analysis (INAA) for the elements Cr, Mn, Fe, Co, Zn, As, Se, and Sb. The simple digestion method yielded excellent agreement for Cr, Fe, Zn, As, Se, and Sb, with slopes of the ICP-MS vs. INAA regressions of 0.90-1.00 and R2 values of 0.96-1.00. The regressions for Mn and Co had slopes of 0.82 and 0.84 with R2 values of 0.83 and 0.82, respectively. Addition of HF/H3BO3 did not improve the correlation for any of the elements and degraded the precision somewhat. The technique provides sensitivity and accuracy for trace elements in relatively small aerosol samples used in atmospheric chemistry studies related to SO2 oxidation in cloud droplets. The ability to determine concentrations of a very large number of elements from a single analysis will permit source apportionment of various trace pollutants and hence strategies to control the sources of air pollution. This is particularly important as the health effects of particulate matter are increasingly recognized.