Ultrasound-assisted sequential extraction method for the evaluation of mobility of toxic elements in contaminated soils

A method for the fast sequential extraction of toxic elements in contaminated soil samples using an ultrasonic water bath, followed by determination with inductively coupled plasma optical emission spectrometry (ICP-OES), was developed and compared with other methods introduced in the literature. The five-step sequential extraction (Tessier scheme) was shortened using ultrasound-assisted sequential extraction (UASE). The optimization of the five-step sequential extraction was based on the analysis of SRM 2710 using Tessiers’s method as a reference. Several extracting solutions with different sonication times and temperatures were tested in the optimization procedure. Concentrations of arsenic, cadmium, copper, lead, and zinc were determined in SRM 2710, SRM 2711, and contaminated soil samples with high accuracy and precision. The certified acid-leachable concentrations of the SRM 2710 were obtained for all elements investigated by using an optimized UASE method. Tessiers’s method yielded total element concentrations that were too high. The determination of zinc in SRM 2711 yielded concentrations that were too low, whereas arsenic determination yielded concentrations that were too high by the UASE method and analysis by ICP-OES. The analysis of the SRMs showed that the UASE method is highly comparable with the other methods used for such purposes. The major advantages of the UASE method are the high treatment rate (40 samples simultaneously with a sonication time of 54 min) and a low sample and reagent usage.     

Comparison of solid phase extraction, saponification and gel permeation chromatography for the clean-up of microwave-assisted biological extracts in the analysis of polycyclic aromatic hydrocarbons

The feasibility of different clean-up procedures was studied for the determination of polycyclic aromatic hydrocarbons (PAHs) in biota samples such as oysters, mussels and fish liver. In this sense, once the samples were extracted--essentially with acetone and in a microwave system--and before they could be analysed by gas chromatography-mass spectrometry (GC-MS), three different approaches were studied for the clean-up step: solid phase extraction (SPE), microwave-assisted saponification (MAS) and gel permeation chromatography (GPC). The main aim of this work was to maximise the recoveries of PAHs and to minimise the presence of interfering compounds in the last extract. In the case of SPE, Florisil cartridges of 1, 2 and 5 g, and silica cartridges of 5 g were studied. In that case, and with oysters and mussels, microwave-assisted extraction and 5 g Florisil cartridges provided good results. In addition, the concentrations obtained for Standard Reference Material (SRM) NIST 2977 (mussel tissue) were in good agreement with the certified values. In the case of microwave-assisted saponification, the extracts were not as clean as those obtained with 5 g Florisil and this fact lead to overestimate the concentration of the heaviest PAHs. Finally, the cleanest extracts were obtained by GPC. The method was successfully applied to mussels, oysters and hake liver, and the results obtained for NIST 2977 (mussel tissue) were within the confidence interval of the certified reference material for most of the certified analytes.     

Determination of arsenic and selenium in spinach and tomato leaves reference materials using flow injection and atomic absorption spectrometry

A flow-injection atomic absorption spectrometric method was developed for the determination of trace amounts of arsenic and selenium in proposed spinach and tomato leaves standard reference materials (SRM 1570a and SRM 1573a). The samples were digested with HNO(3), H(2)SO(4) and HClO(4) using reflux column. The experimental details for sample preparation and the flow injection hydride generation method are discussed. The effect of matrix and various acid concentrations on the extraction and absorbance was also studied. The method has detection limits of 0. 15 ng As/ml and 0.17 ng Se/ml. Standard Reference Materials (SRM 1571 and 1547) were analyzed and the results agreed well with the certified values.     

Determination of mineral and trace element concentrations in pine needles by ICP-OES: evaluation of different sample pre-treatment methods

In the present study, the determination of mineral and trace elements (Al, B, Ca, Cu, Fe, K, Mg, Mn, Na, P and Zn) from pine needles using three sample pre-treatment methods followed by inductively coupled plasma optical emission spectrometry, was examined. Sample pre-treatment methods tested were microwave digestion, ultrasound-assisted digestion and dry ashing. The new ultrasound-assisted digestion method was optimised by the analysis of the standard reference material (SRM) 1575a (pine needles) sample. The speed of dry ashing method was significantly increased by ultrasound dissolution after ashing. All the ICP-OES measurements were performed in robust plasma conditions which were tested by measuring the Mg II 280.270 nm/Mg I 285.213 nm line intensity ratios. The microwave digestion resulted generally in slightly higher element concentrations than ultrasound-assisted digestion. B, Cu and Na resulted in such low concentrations that they could not be accurately determined by using the microwave digestion method. The t-tests found no significant differences between the certified and the determined element concentrations of the SRM 1575a using the dry ashing method followed with ultrasound dissolution.     

An ultrasound-assisted digestion method for the determination of toxic element concentrations in ash samples by inductively coupled plasma optical emission spectrometry

A method of ultrasound-assisted digestion followed by inductively coupled plasma optical emission spectrometry (ICP-OES) used for the determination of toxic element concentrations (arsenic, barium, cobalt, copper, lead, nickel, strontium, vanadium and zinc) in ash samples was developed. All the measurements were performed in robust plasma conditions which were tested by measuring the Mg(II) 280.270 nm/Mg(I) 285.213 nm line intensity ratios. The highest line intensity ratios were observed when a nebulizer gas flow of 0.6 L min⁻¹, auxiliary gas flow of 0.2 L min⁻¹ and plasma power of 1400 W were used for radially viewed plasma. The analysis of SRM 1633b showed that the ultrasound-assisted method developed is highly comparable with the microwave digestion method standardized by the United States Environmental Protection Agency (EPA-3052). The ultrasound-assisted digestion with a digestion solution of aqua regia and hydrofluoric acid (HF) resulted in recovery rates of over 81%. One exception is arsenic which resulted in recoveries of about 60% only; however, it could be digested with good recovery (>90%) using a digestion solution of 5 mL of water and 5 mL of aqua regia. The major advantage of the ultrasound-assisted digestion over microwave digestion is the high treatment rate (30 samples simultaneously with a sonication time of 18 min).     

CZE for the speciation of arsenic in aqueous soil extracts

We developed two separation methods using CZE with UV detection for the determination of the most common inorganic and methylated arsenic species and some phenylarsenic compounds. Based on the separation method for anions using hydrodynamic sample injection the detection limits were 0.52, 0.25, 0.27, 0.12, 0.37, 0.6, 0.6, 1.2 and 1.0 mg As/L for phenylarsine oxide (PAO), p-aminophenylarsonic acid (p-APAA), o-aminophenylarsonic (o-APAA), phenylarsonic acid (PAA), 4-hydroxy-3-nitrobenzenearsonic acid (roxarsone), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenite or arsenious acid (As(III)) and arsenate (As(V)), respectively. These detection limits were improved by large-volume sample stacking with polarity switching to 32, 28, 14, 42, 22, 27, 26 and 27 microg As/L for p-APAA, o-APAA, PAA, roxarsone, MMA, DMA, As(III) and As(V), respectively. We have applied both methods to the analysis of the arsenic species distribution in aqueous soil extracts. The identification of the arsenic species was validated by means of both standard addition and comparison with standard UV spectra. The comparison of the arsenic species concentrations in the extracts determined by CZE with the total arsenic concentrations measured by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) indicated that CZE is suited for the speciation of arsenic in environmental samples with a high arsenic content. The extraction yield of phenylarsenic compounds from soil was derived from the arsenic concentrations of the aqueous soil extracts and the total arsenic content of the soil determined by ICP-AES after microwave digestion. We found that 6-32% of the total amount of arsenic in the soil was extractable by a one-step extraction with water in dependence on the type of arsenic species.     

微波消解-电感耦合等离子体原子发射光谱(ICP-AES)法测定含铜污泥中多种重金属

为了填补现有方法的技术空白,本方法采用微波消解和电感耦合等离子体原子发射光谱法（ ICP-AES）相结合,实现对含铜污泥中铅、锌、铬、镉、砷、镁、铝、锑量的同时测定。首先采用盐酸-硝酸-氢氟酸微波消解进行样品的前处理,消解后加入高氯酸置于电热板进行除碳并赶酸,溶样效果理想,且有效避免了高温溶样对易挥发元素砷、锑的损失,整个过程安全、高效、无损。溶样后以电感耦合等离子体发射光谱法（ ICP-AES）进行测定。对含铜污泥的分解方法进行了合理选择,并对测定时的元素分析谱线及各测定元素间干扰情况等进行了讨论。该方法的加标回收率在95.31%~107.28%%,相对标准偏差（RSD）在0.31%~2.05%之间（n=7),结果表明,该方法准确度高,操作简单快捷,可同时测定多种元素,能满足批量的测定含铜污泥中铅、锌、镍、铁、镉、铬、砷、锑含量的测定要求。     

Two new marine sediment standard reference materials (SRMs) for the determination of organic contaminants

Two new marine sediment standard reference materials (SRMs), SRM 1941b Organics in Marine Sediment and SRM 1944 New York/New Jersey Waterway Sediment, have been recently issued by the National Institute of Standards and Technology (NIST) for the determination of organic contaminants including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyl (PCB) congeners, and chlorinated pesticides. Both sediment SRMs were analyzed using multiple analytical methods including gas chromatography/mass spectrometry (GC/MS) on columns with different selectivity, reversed-phase liquid chromatography with fluorescence detection (for PAHs only), and GC with electron capture detection (for PCBs and pesticides only). SRM 1941b has certified concentrations for 24 PAHs, 29 PCB congeners, and 7 pesticides, and SRM 1944 has certified concentrations for 24 PAHs, 29 PCB congeners, and 4 pesticides. Reference concentrations are also provided for an additional 58 (SRM 1941b) and 39 (SRM 1944) PAHs, PCB congeners, and pesticides. SRM 1944, which was collected from multiple sites within New York/New Jersey coastal waterways, has contaminant concentrations that are generally a factor of 10–20 greater than SRM 1941b, which was collected in the Baltimore (Maryland) harbor. These two SRMs represent the most extensively characterized marine sediment certified reference materials available for the determination of organic contaminants.Electronic Supplementary Material Supplementary material is available in the online version of this article at . A link in the frame on the left on that page takes you directly to the supplementary material.     

Recently developed NIST food related standard reference materials

Summary NIST issues food related, chemical composition standard reference materials for validating food analyses. SRMs certified for inorganic constituents are: Non-Fat Milk Powder (SRM 1549), Oyster Tissue (SRM 1566a), Bovine Liver (SRM 1577a), Wheat Flour (SRM 1567a), Rice Flour (SRM 1568a), and Total Diet (SRM 1548). The certificate of analysis for the total diet SRM also provides a certified concentration for cholesterol. Oyster tissue, a renewal SRM, is certified for 25 elements including 6 (Al, Cl, I, P, S, and V), that had not been certified in the previously issued SRM 1566. The elemental certified concentrations are based on concordant results of two or more independent analytical methods. The chemical compositions of the six food matrix SRMs are tabulated. Three food matrix SRMs certified for organic constituents are: Cholesterol and Fat-Soluble Vitamins in Coconut Oil (SRM 1563), Cholesterol in Whole Egg Powder (SRM 1845) and Organics in Cod Liver Oil (SRM 1588). Serum and urine matrix SRMs are also available that may be useful for metabolic and bioavailability studies.     

ICP-AES法测定化妆品中铅、镉、砷、汞、锑、铬、镍、钡、锶等禁限用元素含量

建立了化妆品中铅(Pb)、镉(Cd)、砷(As)、汞(Hg)、锑(Sb)、铬(Cr)、镍(Ni)、钡(Ba)、锶(Sr)含量的电感耦合等离子体原子发射光谱法(ICP-AES)同步检测技术。采用微波消解,在较难消化的化妆品中加HF进行消化,铑(Rh)为内标元素消除基体干扰,以配备耐HF进样系统的ICP-AES进行测定。在0～1.0 mg/L范围内呈现良好的线性关系(相关系数≥0.9999),Pb、Cd、As、Hg、Sb、Cr、Ni、Ba、Sr检出限分别为0.0016,0.0007,0.0021,0.0013,0.0003,0.0009,0.0008,0.0009,0.0021 mg/L,方法回收率80.2%～111%,精密度1.7%～8.2%。结果表明,该方法适用于检测基体复杂的化妆品中Pb、Cd、As、Hg、Sb、Cr、Ni、Ba、Sr。     

Digestion of plastic materials for the determination of toxic metals with a microwave oven for household use.

A rapid sample-digestion method for the determination of toxic metals, cadmium, chromium, and lead, in polyethylene and polyvinyl chloride has been developed by using a microwave oven for household use. An appropriate amount of the sample taken in a PTFE decomposition vessel was mixed with nitric acid or nitric and sulfuric acids. The vessel was heated in a microwave oven by a predetermined operating program. The digested sample was diluted to a definite volume with water after evaporating most of the nitric acid. The precipitate, if formed, was filtered off by a membrane filter. The metals were determined by ICP-AES. The sample digestion required 5 min (for 20-mg sample) to 25 min (for 60-mg sample). The analytical results obtained for cadmium, chromium, and lead in a polyethylene certified reference material, BCR-680, digested with nitric acid, were in good agreement with the certified values.     

Determination of polybrominated diphenyl ethers in environmental standard reference materials

Standard reference materials (SRMs) are valuable tools in developing and validating analytical methods to improve quality assurance standards. The National Institute of Standards and Technology (NIST) has a long history of providing environmental SRMs with certified concentrations of organic and inorganic contaminants. Here we report on new certified and reference concentrations for 27 polybrominated diphenyl ether (PBDE) congeners in seven different SRMs: cod-liver oil, whale blubber, fish tissue (two materials), mussel tissue and sediment (two materials). PBDEs were measured in these SRMs, with the lowest concentrations measured in mussel tissue (SRM 1974b) and the highest in sediment collected from the New York/New Jersey Waterway (SRM 1944). Comparing the relative PBDE congener concentrations within the samples, we found the biota SRMs contained primarily tetrabrominated and pentabrominated diphenyl ethers, whereas the sediment SRMs contained primarily decabromodiphenyl ether (BDE 209). The cod-liver oil (SRM 1588b) and whale blubber (SRM 1945) materials were also found to contain measurable concentrations of two methoxylated PBDEs (MeO-BDEs). Certified and reference concentrations are reported for 12 PBDE congeners measured in the biota SRMs and reference values are available for two MeO-BDEs. Results from a sediment interlaboratory comparison PBDE exercise are available for the two sediment SRMs (1941b and 1944).     

Boron determination in biological materials by inductively coupled plasma atomic emission and mass spectrometry: effects of sample dissolution methods

This study compares four sample dissolution methods for Boron determination in two National Institute of Standard and Technology (NIST) botanical Standard Reference Materials (SRMs) and three Agriculture Canada/NIST RMs, each having a reference (certified or best estimate) B concentration. The dissolution treatments consisted of: 1) dry ashing at 500° C, 2) wet digestion with HNO₃ + H₂O₂, 3) extraction with hot HNO₃ and 4) closed vessel microwave dissolution. The samples were spiked before and after imposing dissolution treatments to study B recovery by inductively coupled plasma mass spectrometric (ICP-MS) analysis. Microwave digests of NIST SRM 1515 and some in-house RMs were also used to compare the B values of ICP-MS and ICP-AES (atomic emission spectrometry). While all three digestion methods (dry ashing, wet ashing and microwave) dissolved botanical samples, only the microwave method worked well for animal tissues. In terms of B values in these materials, there was no significant difference among the three digestion treatments. Near 100% recovery of B spiked before and after the sample dissolution indicates that there may not be a significant loss of B during the dissolution process used in this study. Extraction with hot HNO₃ was as effective as the three digestion treatments, and B values for this method agreed well with reference values. For the botanical materials studied, the B values determined by ICP-AES were not significantly different from ICP-MS values. This study shows that a simple, time and labor efficient hot HNO₃ extraction is as effective as other digestion/dissolution methods for quantitative B recovery from biological materials. Received: 13 June 1996 / Revised: 17 September 1996 / Accepted: 19 September 1996     

Isotope dilution inductively coupled plasma mass spectrometry (ID ICP-MS) for the certification of lead and cadmium in environmental standard reference materials

Lead (Pb) and cadmium (Cd) have been determined in six new environmental standard reference materials (SRMs) using isotope dilution inductively coupled plasma mass spectrometry (ID ICP-MS). The SRMs are the following: SRM 1944, New York-New Jersey Waterway Sediment, SRMs 2583 and 2584, Trace Elements in Indoor Dust, Nominal 90 mg/kg and 10,000 mg/kg Lead, respectively, SRMs 2586 and 2587, Trace Elements in Soil Containing Lead from Paint, Nominal 500 mg/kg and 3,000 mg/kg Lead, respectively, and SRM 2782, Industrial Sludge. The capabilities of ID ICP-MS for the certification of Pb and Cd in these materials are assessed. Sample preparation and ratio measurement uncertainties have been evaluated. Reproducibility and accuracy of the established procedures are demonstrated by determination of gravimetrically prepared primary standard solutions and by comparison with isotope dilution thermal ionization mass spectrometry (ID TIMS). Material heterogeneity was readily demonstrated to be the dominant source of uncertainty in the certified values.     

Isotope dilution inductively coupled plasma mass spectrometry (ID ICP-MS) for the certification of lead and cadmium in environmental standard reference materials

Lead (Pb) and cadmium (Cd) have been determined in six new environmental standard reference materials (SRMs) using isotope dilution inductively coupled plasma mass spectrometry (ID ICP-MS). The SRMs are the following: SRM 1944, New York-New Jersey Waterway Sediment, SRMs 2583 and 2584, Trace Elements in Indoor Dust, Nominal 90 mg/kg and 10,000 mg/kg Lead, respectively, SRMs 2586 and 2587, Trace Elements in Soil Containing Lead from Paint, Nominal 500 mg/kg and 3000 mg/kg Lead, respectively, and SRM 2782, Industrial Sludge. The capabilities of ID ICP-MS for the certification of Pb and Cd in these materials are assessed. Sample preparation and ratio measurement uncertainties have been evaluated. Reproducibility and accuracy of the established procedures are demonstrated by determination of gravimetrically prepared primary standard solutions and by comparison with isotope dilution thermal ionization mass spectrometry (ID TIMS). Material heterogeneity was readily demonstrated to be the dominant source of uncertainty in the certified values.     

微波消解–电感耦合等离子体质谱法测定酱卤肉中铬、砷、镉、铊、铅

建立微波消解–电感耦合等离子体质谱法测定酱卤肉中铬、砷、镉、铊、铅5种元素含量的检测方法。采用微波消解法处理酱卤肉样品,对预处理条件和仪器工作参数进行了优化,以内标校正法降低基体影响。结果表明,铬、砷、镉、铊、铅5种元素的质量浓度在0.1~50.0 μg/L范围内与质谱响应值具有良好的线性关系,相关系数均大于0.999,方法检出限为0.2~6.2 μg/kg。在3种加标浓度水平下平均回收率为72.4%~113.5%,测定结果的相对标准偏差为3.1%~7.7%(n=6)。该方法简便,快速,高效,准确,可为酱卤肉中铬、砷、镉、铊、铅的测定提供技术支持。     

Micellar Extraction of Polycyclic Aromatic Hydrocarbons from Certified Marine Sediment

Abstract

In the present study the extraction of polycyclic aromatic hydrocarbons from a certified marine sediment (SRM 1941a) with a micellar medium of polyoxyethylene 10 lauryl ether by micro-wave- and ultrasound-assisted method has been evaluated. The analysis of extracts has been carried out by HPLC with fluorimetric detection and wavelength programming. Hydrocarbons with more than three rings gave average recoveries of 77.4% and 86.5%, by microwave- and ultrasound-assisted methods respectively, with a mean relative standard deviation better than 6.2%.     

Microwave Assisted Digestion Method for the Determination of Cadmium,Copper, Lead,and Zinc in Biological Materials

Anodic stripping voltammetry is useful instrumental method for trace element determination in biological materials. It is however extremely demanding to the quality of the sample preparation process. The high‐pressure microwave assisted digestion seems to meet its requirements. The differential pulse anodic stripping voltammetry technique was used for determination of cadmium, copper, lead and zinc in certified reference materials both of plant and of animal origin to prove the analytical properties of such sample preparation method. The found concentrations have been in satisfactory agreement with the certified values. The elaborated digestion procedure is greatly universal and has required accuracy and precision.     

Optimization of operating conditions of axially and radially viewed plasmas for the determination of trace element concentrations from ultrasound-assisted digests of soil samples contaminated by lead pellets

The method of ultrasound-assisted extraction followed by inductively coupled plasma optical emission spectrometry (ICP-OES) used for the determination of trace element concentrations (arsenic, copper, lead, antimony, and zinc) in shooting range areas was optimized. Optimization was achieved not only on the basis of the analysis of appropriate standard reference materials but also on that of 31 synthetic mixtures of matrix and analyte elements (aluminum, antimony, arsenic, calcium, copper, lead, iron, manganese, silicon, and zinc), in five concentrations. All the measurements were performed in robust plasma conditions which were tested by measuring the Mg II 280.270 nm/Mg I 285.213 nm line intensity ratio. The highest Mg II 280.270 nm/Mg I 285.213 nm line intensity ratios were observed when a nebulizer gas flow of 0.8 L min⁻¹, auxiliary gas flow of 0.2 L min⁻¹ and plasma power of 1400 W were used for both the axially and radially viewed plasmas. The analysis of 31 synthetic mixtures of the selected elements showed that As concentrations could be accurately determined with axially viewed plasma alone. The determination of Pb and Sb could be performed with either axially or radially viewed plasma whereas, surprisingly, Cu could be determined with high accuracy using radial plasma alone with a power of 1400 W. All the elements investigated were determined with high accuracy using robust plasma conditions and a combination of axially and radially viewed plasmas. The total recoveries of elements from SRM 2710 (Montana soil) and SRM 2782 (Industrial sludge) were highly comparable to leach recoveries certified by the National Institute of Standards and Technology (NIST).     

Certification of methylmercury content in two fresh-frozen reference materials: SRM 1947 Lake Michigan fish tissue and SRM 1974b organics in mussel tissue (Mytilus edulis)

This paper describes the development of two independent analytical methods for the extraction and quantification of methylmercury from marine biota. The procedures involve microwave extraction, followed by derivatization and either headspace solid-phase microextraction (SPME) with a polydimethylsiloxane (PDMS)-coated silica fiber or back-extraction into iso-octane. The identification and quantification of the extracted compounds is carried out by capillary gas chromatography/mass spectrometric (GC/MS) and inductively coupled plasma mass spectrometric (GC/ICP-MS) detection. Both methods were validated for the determination of methylmercury (MeHg) concentrations in a variety of biological standard reference materials (SRMs) including fresh-frozen tissue homogenates of SRM 1946 Lake Superior fish tissue and SRM 1974a organics in mussel tissue (Mytilus edulis) and then applied to the certification effort of SRM 1947 Lake Michigan fish tissue and SRM 1974b organics in mussel tissue (Mytilus edulis). While past certifications of methylmercury in tissue SRMs have been based on two independent methods from the National Institute of Standards and Technology (NIST) and participating laboratories, the methods described within provide improved protocols and will allow future certification efforts to be based on at least two independent analytical methods within NIST.