Some observations on the determination of total heavy metals in sewage sludge by atomic absorption spectrophotometry after a pressurized acid digestion

An economical and simple method for the flame atomic absorption spectrometric determination of Cd, Pb, Ni, Cu, Fe, and Zn in sewage sludges is described. Samples are treated with concentrated HNO₃ in a thermal oven using Pyrex glass tubes hermetically sealed with Bakelite screw caps. The effect of the digestion parameters, such as digestion time, acid volume, sample mass, and temperature, were studied. The precision and accuracy of this procedure were evaluated by the analysis of two BCR (Community Bureau of Reference, European Communities) certified sewage sludge samples (CRM 146 and 144).     

Flow injection determination of lead and cadmium in hair samples from workers exposed to welding fumes

A flow injection procedure involving continuous acid leaching for lead and cadmium determination in hair samples of persons in permanent contact with a polluted workplace environment by flame atomic absorption spectrometry is proposed. Variables such as sonication time, nature and concentration of the acid solution used as leaching solution, leaching temperature, flow-rate of the continuous manifold, leaching solution volume and hair particle size were simultaneously studied by applying a Plackett–Burman design approach. Results showed that nitric acid concentration (leaching solution), leaching temperature and sonication time were statistically significant variables (confidence interval of 95%). These last two variables were finally optimised by using a central composite design. The proposed procedure allowed the determination of cadmium and lead with limits of detection 0.1 and 1.0 μg g⁻¹, respectively. The accuracy of the developed procedure was evaluated by the analysis of a certified reference material (CRM 397, human hair, from the BCR). The proposed method was applied with satisfactory results to the determination of Cd and Pb in human hair samples of workers exposed to welding fumes.     

Certified reference material (CRM 397) for the quality control of trace element analysis of human hair

Summary Analyses of human hair are routinely performed by a number of organisations to monitor the level of exposure of a population to toxic elements, e.g. heavy metals. To control the quality of such determinations, the Community Bureau of Reference (BCR) has produced a reference material (CRM 397) certified for its contents of Cd, Hg, Pb, Se and Zn. This material was collected in a moderately contaminated area, carefully prepared and its homogeneity and long term stability were verified. This paper presents the certification work performed.     

Utilization of optimized BCR three-step sequential and dilute HCl single extraction procedures for soil-plant metal transfer predictions in contaminated lands

The prediction of soil metal phytoavailability using the chemical extractions is a conventional approach routinely used in soil testing. The adequacy of such soil tests for this purpose is commonly assessed through a comparison of extraction results with metal contents in relevant plants. In this work, the fractions of selected risk metals (Al, As, Cd, Cu, Fe, Mn, Ni, Pb, Zn) that can be taken up by various plants were obtained by optimized BCR (Community Bureau of Reference) three-step sequential extraction procedure (SEP) and by single 0.5 mol L(-1) HCl extraction. These procedures were validated using five soil and sediment reference materials (SRM 2710, SRM 2711, CRM 483, CRM 701, SRM RTH 912) and applied to significantly different acidified soils for the fractionation of studied metals. The new indicative values of Al, Cd, Cu, Fe, Mn, P, Pb and Zn fractional concentrations for these reference materials were obtained by the dilute HCl single extraction. The influence of various soil genesis, content of essential elements (Ca, Mg, K, P) and different anthropogenic sources of acidification on extraction yields of individual risk metal fractions was investigated. The concentrations of studied elements were determined by atomic spectrometry methods (flame, graphite furnace and hydride generation atomic absorption spectrometry and inductively coupled plasma optical emission spectrometry). It can be concluded that the data of extraction yields from first BCR SEP acid extractable step and soil-plant transfer coefficients can be applied to the prediction of qualitative mobility of selected risk metals in different soil systems.     

Determination of arsenic in scalp hair samples from exposed subjects using microwave-assisted digestion with and without enrichment based on cloud point extraction by electrothermal atomic absorption spectrometry

A simple and rapid cloud point extraction (CPE) procedure was applied for preconcentration of trace quantities of arsenic (As) in scalp hair samples. The samples were subjected to microwave-assisted digestion in a mixture of nitric acid and hydrogen peroxide (2 + 1, v/v) prior to preconcentration by CPE. The As in digested samples was complexed with ammonium pyrrolidine dithiocarbamate (APDC), and the resultant As-PDC complex was extracted by a nonionic surfactant, octylphenoxypolyethoxyethanol (Triton X-114). After centrifugation, the surfactant-rich phase was diluted with 0.1 M HNO3 in methanol and analyzed by electrothermal atomic absorption spectrometry. The experimental parameters, i.e., amount of APDC, concentration of Triton X-114, equilibrium temperature and time, were optimized. For validation of the proposed method, a certified reference material (CRM) of human hair (BCR 397) was used. No significant difference (P > 0.05) was observed between the experimental results and certified values of the CRM (paired t-test). The LOD and LOQ obtained under the optimal conditions were 0.025 and 0.083 microg/kg, respectively. The developed method was applied for the determination of As in scalp hair samples from male and female subjects of two villages of Khairpur Mir's, Pakistan.     

Determination of cadmium and lead in biological samples by three ultrasonic-based samples treatment procedures followed by electrothermal atomic absorption spectrometry

The development of 3 different ultrasonic-based sample treatment methods, ultrasonic probe-assisted acid extraction, ultrasonic-assisted acid slurry, and ultrasonic-assisted acid pseudodigestion is presented. These methods were compared for the determination of Cd and Pb by electrothermal atomic absorption spectrometry in biological samples (blood and scalp hair) and validated by using certified materials BCR 397 human hair and BCR 185R bovine liver. The sample amounts chosen to perform the analysis were 100 mg and 0.5 mL for solids (human hair and bovine liver) and blood samples, respectively. An acid digestion induced by microwave energy was used to obtain the total metal concentrations and for comparative purposes. The best results were obtained with the ultrasonic-assisted acid pseudodigestion, with which it was possible to perform accurate and precise determination of the Cd and Pb contents in 2 certified reference materials and biological samples of 50 normal males of ages 25-40 years. The precision of the methods, together with their efficiency, rapidity, low cost, and environmental acceptability, make them good alternatives for the determination of trace metals from biological samples. The precision of the methods for accuracy evaluation, resulting in good agreement according to the t-test for a 95% confidence level, and the relative standard deviations were lower than 10% (n=10) for all determinations.     

Determination of iron,cobalt, nickel,manganese, zinc,copper, cadmium and lead in human hair by inductively coupled plasma-atomic emission spectrometry

A method was standardized for the dissolution of hair samples and analysis was carried out by inductively coupled plasma atomic emission spectrometry (ICP-AES). Hair samples were brought into solution by using a mixture of nitric acid and hydrogen peroxide. Various parameters that influence the sample preparation, namely temperature, digestion time and ratio of acid mixture were studied and standardized. The optimized method has been employed to digest standard reference materials and hair samples of residents of India, collected from different age groups and sex, and analyzed for Fe, Co, Ni, Mn, Zn, Cu, Cd and Pb. The values agree for most of the metals with the data reported for human hair samples of residents of India. The NIES CRM Human Hair No. 5 and IAEA Reference Hair HH-1 certified reference materials were used in order to verify the accuracy of the method and the results were in excellent agreement with the certified values.     

Ultrasound-Assisted Extraction for the Evaluation of Element Mobility in Bottom Sediment Collected at Mining and Smelting Pb–Zn Ores Area in Poland

The current BCR procedure for metal fractionation recommended by the Standard Measurement and Testing Programme requires rather time-consuming sample pretreatment. Ultrasonic energy seems to be an attractive alternative for leaching metal from solid samples into a liquid extractant phase. This study aims at optimizing ultrasonic extraction in order to replace the BCR method of leaching using acetic acid and to apply the procedure of assessing element mobility in bottom sediment rich in moderately soluble carbonate minerals. The application of ICP-MS allowed the determination of As, Cd, Cr, Cu, Pb, Ni, Tl and Zn in extracts, in a wide range of concentration without any special treatment. Finally, 40’min extraction in an ultrasonic bath was proposed for evaluation of the mobile fraction of As, Cd, Cr, Cu, Pb and Zn as an assessment of environmental risk. The recovery of the ultrasound-assisted extraction in comparison to the shake-filter method, as applied in the common BCR procedure, was slightly higher than 100% for As, Cr and Pb, reasonably high (about 70%) for Cd, Zn and Cd, but did not exceed 21% for Tl. Also, the mobility and extractability (relative mobility) of the studied elements from sediment collected over one year were compares. According to the results obtained after 40’min of ultrasound-assisted extraction it can be concluded that mobility did not change over one year for Cr, Cu, As, Cd, Ni and Tl, but noticeable differences for Zn and Pb were observed. The total content of all studied elements was almost the same in samples taken in the years 2003 and 2004, respectively.     

Ultrasound-assisted solubilization of trace and minor metals from plant tissue using ethylenediaminetetraacetic acid in alkaline medium

A simplified and fast sample pretreatment method based on ultrasound-assisted solubilization of metals from plant tissue with ethylenediaminetetraacetic acid in alkaline medium is described. Powdered unknown and certified plant samples (particle size < 50 microns) were slurried in the solubilization medium and subjected to high intensity ultrasonication by a probe ultrasonic processor (20 kHz, 100 W). Metal solubilization can be accomplished within 3 min using a 30% vibrational amplitude and 0.1 M EDTA at pH 10, the supernatant obtained upon centrifugation being used for analysis. The method is applied to several food plants with unknown metal contents and certified plant samples such as CRM GBW07605 tea leaves, BCR CRM 61 aquatic moss and BCR CRM 482 lichen, with good trueness and precision. Intensive treatments with concentrated acids involving total matrix decomposition can be avoided. Metal determination (Ca, Cd, Mg, Mn, Pb and Zn) in the alkaline extracts was carried out by flame and electrothermal atomic absorption spectrometry.     

Ultrasound-assisted solubilization of trace and minor metals from plant tissue using ethylenediaminetetraacetic acid in alkaline medium

A simplified and fast sample pretreatment method based on ultrasound-assisted solubilization of metals from plant tissue with ethylenediaminetetraacetic acid in alkaline medium is described. Powdered unknown and certified plant samples (particle size < 50 μm) were slurried in the solubilization medium and subjected to high intensity ultrasonication by a probe ultrasonic processor (20 kHz, 100 W). Metal solubilization can be accomplished within 3 min using a 30% vibrational amplitude and 0.1 M EDTA at pH 10, the supernatant obtained upon centrifugation being used for analysis. The method is applied to several food plants with unknown metal contents and certified plant samples such as CRM GBW07605 tea leaves, BCR CRM 61 aquatic moss and BCR CRM 482 lichen, with good trueness and precision. Intensive treatments with concentrated acids involving total matrix decomposition can be avoided. Metal determination (Ca, Cd, Mg, Mn, Pb and Zn) in the alkaline extracts was carried out by flame and electrothermal atomic absorption spectrometry.     

Certified reference materials—Hay Powder (CRM 129) and Rye Grass (CRM 281)—for the quality control of analysis of animal feed

Analyses of nutritive elements are routinely performed in grass or hay for animal feed in order to improve the state of health and growth of domestic animals. To control the quality of such determinations, the Community Bureau of Reference (BCR) so far has produced two certified reference materials: Hay Powder (CRM 129) and Rye Grass (CRM 281). After a careful preparation procedure of the materials, a homogeneity study and a long-term stability study, the contents of the elements Ca, K, Mg, P, S, Zn, I, N and Kjeldahl-N were certified in CRM 129, whereas CRM 281 was certified for As, B, Cd, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Se and Zn. This paper presents the certification exercise and especially concentrates on the elements I, B and Mo as examples of analytical work. Indicative values for Co, Cr, Fe, Cl and Na were also obtained.     

Certified reference material for the quality control of cadmium,copper nickel and zinc determination in estuarine water (CRM 505)

Analyses of estuarine water samples are routinely carried out by a number of laboratories to monitor the level of environmental contamination by toxic substances, e.g. heavy metals. A series of interlaboratory studies has been organised by the Community Bureau of Reference, BCR (now renamed Standards, Measurements and Testing Programme) to improve the quality of the determinations of selected trace metals in estuarine water samples. The improvement achieved allowed to produce a reference material (CRM 505) which was certified for its content of Cd, Cu, Ni and Zn. Further improvements were considered to be necessary for the certification of other trace elements, e.g. Pb. This material was collected in the Tagus Estuary, carefully prepared (filtered and acidified) and its homogeneity and long term stability were verified. This paper presents the work performed for the certification of Cd, Cu, Ni and Zn. Indicative values are reported for As, Co, Fe, Mn, Pb and V.     

Certified reference material for the quality control of cadmium, copper nickel and zinc determination in estuarine water (CRM 505)

Analyses of estuarine water samples are routinely carried out by a number of laboratories to monitor the level of environmental contamination by toxic substances, e.g. heavy metals. A series of interlaboratory studies has been organised by the Community Bureau of Reference, BCR (now renamed Standards, Measurements and Testing Programme) to improve the quality of the determinations of selected trace metals in estuarine water samples. The improvement achieved allowed to produce a reference material (CRM 505) which was certified for its content of Cd, Cu, Ni and Zn. Further improvements were considered to be necessary for the certification of other trace elements, e.g. Pb. This material was collected in the Tagus Estuary, carefully prepared (filtered and acidified) and its homogeneity and long term stability were verified. This paper presents the work performed for the certification of Cd, Cu, Ni and Zn. Indicative values are reported for As, Co, Fe, Mn, Pb and V.     

A comparison of an optimised sequential extraction procedure and dilute acid leaching of elements in anoxic sediments, including the effects of oxidation on sediment metal partitioning

The effect of oxidation of anoxic sediment upon the extraction of 13 elements (Cd, Sn, Sb, Pb, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As) using the optimised Community Bureau of Reference of the European Commission (BCR) sequential extraction procedure and a dilute acid partial extraction procedure (4 h, 1 mol L⁻¹ HCl) was investigated. Elements commonly associated with the sulfidic phase, Cd, Cu, Pb, Zn and Fe exhibited the most significant changes under the BCR sequential extraction procedure. Cd, Cu, Zn, and to a lesser extent Pb, were redistributed into the weak acid extractable fraction upon oxidation of the anoxic sediment and Fe was redistributed into the reducible fraction as expected, but an increase was also observed in the residual Fe. For the HCl partial extraction, sediments with moderate acid volatile sulfide (AVS) levels (1-100 μmol g⁻¹) showed no significant difference in element partitioning following oxidation, whilst sediments containing high AVS levels (>100 μmol g⁻¹) were significantly different with elevated concentrations of Cu and Sn noted in the partial extract following oxidation of the sediment. Comparison of the labile metals released using the BCR sequential extraction procedure (ΣSteps 1-3) to labile metals extracted using the dilute HCl partial extraction showed that no method was consistently more aggressive than the other, with the HCl partial extraction extracting more Sn and Sb from the anoxic sediment than the BCR procedure, whilst the BCR procedure extracted more Cr, Co, Cu and As than the HCl extraction.     

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.     

The utilization of modified BCR three-step sequential extraction procedure for the fractionation of Cd, Cr, Cu, Ni, Pb and Zn in soil reference materials of different origins

A modified three-step sequential extraction procedure for the fractionation of heavy metals, proposed by the Commission of the European Communities Bureau of Reference (BCR) has been applied to the Slovak reference materials of soils (soil orthic luvisols, soil rendzina and soil eutric cambisol), which represent pedologically different types of soils in Slovakia. Analyses were carried out by flame or electrothermal atomic absorption spectrometry (FAAS or ETAAS). The fractions extracted were: exchangeable (extraction step 1), reducible-iron/manganese oxides (extraction step 2), oxidizable-organic matter and sulfides (extraction step 3). The sum of the element contents in the three fractions plus aqua-regia extractable content of the residue was compared to the aqua-regia extractable content of the elements in the origin soils. The accuracy obtained by comparing the determined contents of the elements with certified values, using BCR CRM 701, certified for the extractable contents (mass fractions) of Cd, Cr, Cu, Ni, Pb and Zn in sediment following a modified BCR-three step sequential extraction procedure, was found to be satisfactory.     

Evaluation of heavy metal bioavailability in soil amended with poultry manure using single and BCR sequential extractions

In the present study, three-step Community Bureau of Reference sequential extraction scheme (BCR-SES) and single extraction methods were performed to assess the mobility and availability of heavy metals (Cd, Cu, Pb, Fe and Zn) in an agricultural soil before and after amendment with poultry waste (PW).The PW samples were collected from poultry farms, situated in Hyderabad Sindh, Pakistan. The extractable heavy metals were measured by flame and electrothermal atomic absorption spectrometry. The validation of the method was carried out by analysis of a certified reference material of soil amended with sewage sludge (BCR-483). The single extractions using calcium chloride and EDTA, separately, while BCR-SESs were developed to evaluate the available heavy metals to plants and their environmental accessibility for control soil (CS), PW and soil amended with PW (SPW).The pH of the PW and SPW were found to be < 6.0, which may enhance the leaching of heavy metals to agricultural soil. The results from the partitioning study indicated that easily mobilised forms (acid exchangeable) of Cd were higher than other heavy metals. The oxidisable fractions of all heavy metals were dominant in PW and SPW as compared to found in CS samples. The EDTA- and CaCl₂-extractable heavy metals correspond to 5.0 to 10 and 0.5 to 3.0%, respectively of total contents in all three solid samples. Contamination factors revealed that the retention of Pb and Zn were higher compared with Cu, Cd and Fe in CS, PW and SPW samples.     

Certified reference material (CRM 414) for the quality control of trace element analysis in plankton

Summary Analyses of plankton are performed by a number of organisations to investigate the transfer and uptake of toxic elements along the trophic chain and to monitor the levels of contamination of different aquatic environments. In order to obtain reliable transfer functions in environmental models or to use plankton as an indicator organism for the assessment of environmental pollution, these analyses should give accurate results. As accuracy requires quality control and the application of certified reference materials (CRMs), a certification campaign has been conducted by the Community Bureau of Reference (BCR). A plankton material was collected in a freshwater pond, lyophilised, homogenised and bottled and its homogeneity and long-term stability were verified. The material (CRM 414) was analysed by a group of 15 selected laboratories having given proof of their adequate QC and using different analytical methods. The contents of As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Se, V and Zn are certified. This paper presents the certification work performed.     

Certification of trace element contents (As, Cd, Co, Cu, Fe, Mn, Hg, Na, Pb and Zn) in a fly ash obtained from the combustion of pulverised coal

Summary The element contents of As, Cd, Co, Cu, Fe, Mn, Hg, Na, Pb und Zn of a fly ash from pulverised coal are certified. The procedures and their results for the homogenisation, the contamination and homogeneity checks and the analytical campaign are reported. The certified mass fractions and indicative values for Cr, Ni, Th, V and water soluble sulphate are given. The work was carried out within the framework of the activities of the Community Bureau of Reference (BCR) of the Commission of the European Communities.

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Zertifizierung von Spurengehalten (As, Cd, Co, Cu, Fe, Mn, Hg, Na, Pb und Zn) in einer Flugasche aus Pulverkohle

Zusammenfassung In einer Flugasche aus Pulverkohle wurden die Elementgehalte an As, Cd, Co, Cu, Fe, Mn, Hg, Na, Pb und Zn zertifiziert. Über die Homogenisierung, die Kontrolle der Kontaminierung und Homogenität und die analytischen Ringversuche wird berichtet. Die zertifizierten Gehalte sowie der Gehalt von Cr, Ni, Th, V und wasserlöslichem Sulfat werden gegeben. Die Arbeit wurde ausgeführt im Rahmen des Programms des Referenzbüros der Kommission der Europäischen Gemeinschaften (BCR).

     

Determination of calcium, potassium, manganese, iron, copper and zinc levels in representative samples of two onion cultivars using total reflection X-ray fluorescence and ultrasound extraction procedure

The chemical characterization of onion cultivar samples is an important tool for the enhancement of their productivity due to the fact that chemical composition is closed related to the quality of the products. A new sample preparation procedure for elemental characterization is proposed, involving the acid extraction of the analytes from crude samples by means of an ultrasonic bath, avoiding the required digestion of samples in vegetable tissue analysis. The technique of total reflection X-ray fluorescence (TXRF) was successfully applied for the simultaneous determination of the elements Ca, K, Mn, Fe, Cu and Zn. The procedure was compared with the wet ashing and dry ashing procedures for all the elements using multivariate analysis and the Scheffé test. The technique of flame atomic absorption spectrometry (FAAS) was employed for comparison purposes and accuracy evaluation of the proposed analysis method. A good agreement between the two techniques was found when using the dry ashing and ultrasound leaching procedures. The levels of each element found for representative samples of two onion cultivars (Yellow Granex PRR 502 and 438 Granex) were also compared by the same method. Levels of K, Mn and Zn were significantly higher in the 438 Granex cultivar, while levels of Ca, Fe and Cu were significantly higher in the Yellow Granex PRR 502 cultivar.