Quality control in the analysis of lead and cadmium in blood

Summary An extensive quality control programme has been developed within a global UNEP/WHO project on Assessment of Exposure to Lead and Cadmium through Biological Monitoring. This project was coordinated by the Karolinska Institute (Department of Environmental Hygiene) and the National (Swedish) Institute of Environmental Medicine. The project was carried out within the framework of UNEP's Global Environmental Monitoring System (GEMS) and was initiated in 1978 on the basis of recommendations from a UNEP/WHO meeting of a Government Expert Group on Health-Related Monitoring.On termination of the project in 1981 it was decided to extend the analytical QC assurance programme on a periodic basis in order to maintain the analytical capability of the participating laboratories. A QC programme was conducted by our Institute in a follow-up study of the above mentioned UNEP/WHO programme and for a National Swedish Board of Occupational Safety and Health project, as well as for a recently concluded project in which a decrease in bloodlead levels in residents of Stockholm for the period 1980–1984 was established.In the latter project decreased blood-lead levels of about 20% were found in samples stored frozen (–20 ° C) for 4 years. This finding stimulated a study of the long-term stability of our QC samples. Results of lead and cadmium analyses performed for each QC sample during 1980–1985 were computerized. The results showed that the QC samples appeared to be stable for 2–3 years when stored at –20 °C. The losses of cadmium were 5 –10% in 5–6 years of storage at –20 ° C and seem to be less than those of lead (7–15%). Analysis of several QC sets, prepared on different occasions, but analyzed on the same day, confirmed that losses occur.     

Quality control samples for the determination of lead and cadmium in blood, feces, air filters, and dust

Summary Quality control samples for the determination of lead and cadmium in blood, feces, air filters, and dust have been prepared within the UNEP/WHO Human Exposure Assessment Location (HEAL) Project. The preparation is given in detail. Problems related to sample preparation and reference values are discussed.

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Qualitätskontrollproben für die Bestimmung von Blei und Cadmium in Blut, Faeces, Luftfiltern und Staub

     

Sensitive and stable monitoring of lead and cadmium in seawater using screen-printed electrode and electrochemical stripping analysis

Sensitive and stable monitoring of heavy metals in seawater using screen-printed electrodes (SPE) is presented. The analytical performance of SPE coupled with square wave anodic stripping voltammetry (SWASV) for the simultaneous determination of Pb and Cd in seawater samples, in the low μg L⁻¹ range, is evaluated. The stripping response for the heavy metals following 2 min deposition was linear over the concentration range examined (10-2000 μg L⁻¹) with detection limits of 1.8 and 2.9 μg L⁻¹ for Pb and Cd, respectively. The accuracy of the method was validated by analyzing metal contents in different spiked seawater samples and comparing these results to those obtained with the well-established anodic stripping voltammetry using the hanging mercury drop electrode. Moreover, a certified reference material was also used and the results obtained were satisfactory.     

Solubility of cadmium in lead tellurides

The solubility of cadmium in PbTe was determined using microhardness and hydrostatic density measurements and by electron microscopy and electron probe microanalysis. All these methods indicate that the existence region of Pb_{1 − x} Cd _x Te solid solutions (ss) extends to x = 0.08 at 670°C. As the cadmium concentration of the solid solution increases, microhardness shifts up, whereas density shifts down.     

ICAP-analysis of cadmium and lead in whole blood

Summary The present study deals with the determination by ICAP-AES of cadmium and lead present at normal and elevated concentrations in whole blood. Three sample treatment techniques were tested, viz. the Stoeppler method (matrix modification), low temperature ashing, and thermal ashing. The latter two techniques were applied in combination with an extraction procedure for iron and a pre-concentration procedure using Controlled Pore Glass immobilized 8-hydroxyquinoline (CPG-8HQ). The determination of normal concentrations was accomplished by microsampling of analyte concentrates essentially free from matrix metals. The sample treatment techniques applied were assessed on the basis of detection limit, accuracy, precision, pre-concentration capability, and laboriousness.

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ICAP-Analyse von Cadmium und Blei in Vollblut

Zusammenfassung Die Anwendung der ICAP-Emissions-spektrometrie für die Bestimmung von Cadmium und Blei bei normalen und erhöhten Konzentrationen in Vollblut wird beschrieben. Drei Probevorbereitungsverfahren wurden geprüft: die Stoeppler-Methode (Matrixmodifikation), die Niedrigtemperatur-Veraschung im Sauerstoffplasma und die thermische Veraschung. Anschlie\end an die letzten beiden Verfahren erfolgte eine Extraktion von Eisen und ein Anreicherungsverfahren mit auf Controlled Pore Glass immobilisierten 8-Hydroxychinolin. Die Bestimmung normaler Konzentrationen konnte durch Mikroanalyse nahezu matrixfreier Konzentrate erfa\t werden. Die Probenvorbereitungsverfahren wurden in bezug auf Nachweisgrenze, Richtigkeit, PrÄzision, AnreicherungsfÄhigkeit und Zeitaufwand beurteilt.

     

Polarographic behavior of cadmium and lead in -caprolactam

The stability constants of the complexes formed by cadmium and lead with -caprolactam have been determined polarographically. The reductions are reversible and diffusion-controlled. Lead forms two complexes having β₁ and β₂ values 1.75 and 19.55. Cadmium is found to form 1:1 and 1:2 complexes with the values of the constants β₁ = 4.95 and β₂ = 22.65. The percentage distribution of various complex species has been presented. Method is suitable for quantitative determination of these metals.     

The membrane free sonoelectroanalytical determination of trace levels of lead and cadmium in human saliva

In this paper, square wave anodic stripping voltammetry (SWASV), synergistically coupled with an ultrasonically enhanced preconcentration step has been shown to yield a quantitative determination of lead and cadmium in human saliva at a membrane free in situ plated mercury thin film glassy carbon electrode. The sensitivity was facilitated by acoustic streaming which promoted efficient mass transport to the electrode thus reducing sampling times. Cavitation was responsible for cleaning and activating the electrode surface, this was essential in order to obtain a reproducible and representative signal. In silent conditions electrode fouling leading to fluctuations in the baseline current and signal depression, precluded accurate quantitative analyses. The results presented herein provide an extension to the proof of concept given in the authors' earlier work, with the analysis of lead in human saliva as opposed to artificial saliva reported. We also address the hitherto unreported detection and determination of cadmium in this medium. Results for both were independently verified by inductively coupled plasma-mass spectroscopy (ICP-MS). Close agreement between lead concentration determined by sono-SWASV and independent and blind ICP-MS is reported for human saliva samples having a total lead content of 0.92 microg L(-1) and 5 microg L(-1) with a detection limit of 0.5 microg L(-1). Microaddition calibration data for cadmium additions of 0.0125 microg L(-1) to samples spiked with 2.5 microg L(-1) and 5.0 microg L(-1) (reflecting levels in workers occupationally exposed) exhibited close agreement with the known total cadmium in the samples. A detection limit of 1 microg L(-1) cadmium in saliva has been established.     

Enzymatic oxidation of cadmium and lead metals photodeposited on cadmium sulfide

Cadmium and lead metals deposited on CdS particles are shown to act as substrates--electron donors for enzymes, hydrogenase from Thiocapsa roseopersicina (HG), NAD-dependent hydrogenase from Alcaligenes eutrophus (NLH), and ferredoxin:NADP oxidoreductase (FNR) from Chlorella in the formation of hydrogen, NADH and NADPH, respectively. Adsorption of the enzyme on the surface of the metallized CdS particle is required for enzymatic oxidation of metal. The maximum rates for the formation of hydrogen and NADH catalyzed by hydrogenase and NAD-dependent hydrogenase with metals as electron donors are comparable with the rates obtained for these enzymes using soluble substrates. Kinetic analysis of the enzymatic oxidation of cadmium metal has revealed that the rate decreases mainly due to the formation of a solid product, which is supposed to be Cd(OH)2. The deceleration of lead oxidation catalyzed by hydrogenase proceeds at the expense of the inhibitory effect of the formed Pb2+. The enzymatic oxidation of electrochemically prepared cadmium metal is also shown. Based on these results, a new mechanism of action of the enzymes involved in anaerobic biocorrosion is proposed. By this mechanism, the enzyme accelerates the process of metal dissolution through a mediatorless catalysis of the reduction of the enzyme substrate.     

微波消解电感耦合等离子体发射光谱法测定塑料中铅和镉

采用微波消解技术溶样，ICP-AES法测定了塑料中的铅和镉。通过对消解试剂和微波温度程序的研究，建立了塑料样品的微波消解方法。该方法与传统马弗炉高温灰化消解方法比较，具有准确、简便、快速、省试剂、污染少、消解完全等优点。方法回收率为93％～106％，相对标准偏差(n=7)均小于2％。实际样品对比分析结果表明，方法具有良好的准确度，适于多种塑料材料中铅和镉的快速分析。     

The determination of copper,lead, cadmium and zinc in human teeth by anodic stripping voltammetry

Differential pulse anodic stripping voltamrnetry and a hanging mercury drop electrode are used for the determination of copper, lead, cadmium and zinc in Norwegian teeth and pure hydroxyapatite. Special attention is given to the choice of decomposition procedure and the determination of the blank values. A complete dissolution of the tooth material and satisfactory blank values can be obtained by using decomposition with nitric acid in a Teflon bomb.     

Flow injection spectrophotometric analysis of lead in human saliva for monitoring environmental pollution

A new highly sensitive, simple and low-cost methodology for the direct determination of Pb (II) with 2-(5-bromo-2-pyridylazo)-5-dimethylaminophenol in ethanolic medium has been developed. The absorption spectroscopy of the complex has been examined in detail, and the chemical variables affecting the sensitivity of procedure studied, optimized and applied to the determination of trace amounts of lead in human saliva. Under the optimal experimental conditions, a precision of 1.61x10(-4) mug cm(-2) was achieved, the molar absorptivity being (epsilon) 5.6x10(4) l mol(-1) cm(-1). An FI technique is proposed, and it is possible to determine trace levels of lead by injection into a steam buffered at pH 7.15, containing 70% ethanol: 30% Tris buffer 3.5x10(-3) mol l(-1) (pH=7.2), 1x10(-4) mol l(-1) 5-BrDMPAP. The FIA configuration allows the analysis of 45 samples per hour. The lower limit of detection (LOD) was 1x10(-7) mol l(-1). The calibration plot was linear at least within two orders of magnitude of lead concentration. The use of an HPLC pump for the FI analysis led to a substantial improvement in the analytical performance of the method, which clearly satisfies the typical requirements for control processes.     

Thermodynamic study of the system cadmium - zinc,cadmium - lead,cadmium - tin,bismuth - cadmium,tin - zinc,and lead - tin

Russian Chemical Bulletin -     

Screen-printed electrodes incorporated in a flow system for the decentralized monitoring of lead,cadmium and copper in natural and wastewater samples

Mercury-based screen-printed electrodes (SPE) combined with square-wave anodic stripping voltammetry (SWASV) techniques for the analysis of copper, cadmium, lead, and zinc in different water samples have been applied. The detection system has been implemented in a flow cell and different experimental conditions have been tested in view of its application for in-situ monitoring. In particular, an acetate buffer together with a low chloride concentration (0.025?M NaCl) provided best performance and reproducible results. Additionally, the flow system was validated for the first time in terms of limits of detection, linearity, repeatability and recovery. Limits of detection of 2.8?µg?L^?1, 4.1?µg?L^?1, and 7.5?µg?L^?1 for cadmium, lead and copper respectively and repeatabilities lower than 10% (as RSD) were found. Good recoveries have been obtained for the three cations and in particular for copper, even in the presence of zinc. Finally, the method has shown its efficiency for the rapid screening of lead, cadmium and copper contained in both natural waters and wastewater samples.     

Preparation of uniform colloidal cadmium and lead selenide particles

Colloidal cadmium selenide and lead selenide particles of narrow size distribution were prepared by decomposition of selenourea in solutions of corresponding metal salts. While both salts were crystalline, CdSe powders showed nearly spherical morphology whereas PbSe consisted of particles of cubic symmetry. In the latter case greater uniformity was achieved if homogeneous precipitation was carried out in methanol-water mixtures.     

Determination of lead, cadmium, copper and zinc in human tissues by differential pulse anodic stripping voltammetry

Summary A convenient electroanalytical technique for the simultaneous determination of lead, cadmium, copper and zinc in human blood and teeth is described. The method is based on differential pulse anodic stripping voltammetry at the static mercury drop electrode (SMDE). Optimum conditions for the anodic stripping of Pb, Cd, Cu and Zn were determined using ammonium acetate and dilute nitric acid (pH 2) as electrolytes. Interferences from other metals were not observed and the estimations were reproducible within a standard deviation of±4%. Low blank values and high sensitivity of the method allowed the determinations at sub-ppb levels with an electrolysis time of 1–3 min. The accuracy of the method has been tested by comparison with the results obtained by mass spectrometry and atomic absorption spectrometry. The results and findings are discussed in brief.

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Bestimmung von Blei, Cadmium, Kupfer und Zink in menschlichen Geweben mit Hilfe der Differentialpuls-Anodic Stripping Voltammetrie

Zusammenfassung Eine vorteilhafte elektroanalytische Methode zur Bestimmung von Pb, Cd, Cu und Zn in menschlichem Blut und in Zähnen wird beschrieben. Das Verfahren beruht auf der Differentialpuls-Anodic Stripping Voltammetrie an der statischen Quecksilbertropfelektrode. Mit Hilfe von Ammoniumacetat und verdünnter Salpetersäure (pH 2) als Trägerelektrolyten wurden die optimalen Bedingungen ausgearbeitet. Störungen durch andere Metalle wurden nicht beobachtet. Die Standardabweichung betrug ±4%. Infolge der niedrigen Blindwerte und der hohen Empfindlichkeit konnten Bestimmungen im Sub-ppb-Bereich mit Elektrolysezeiten von 1–3 min durchgeführt werden. Die Genauigkeit der Methode wurde durch Vergleich mit massenspektrometrischen und AAS-Untersuchungen bewiesen. Die Ergebnisse werden kurz diskutiert.

     

Direct atomic absorption spectrometric determination of cadmium,lead and manganese in bone and of lead in ivory

Various atomic absorption spectrometric methods — including the solid sampling technique — are described for the determination of cadmium, manganese and lead in hard tissue. The methods were used in the analysis of hydroxyapatite, ivory and animal bone.     

Precise determination of cadmium and lead isotopic compositions in river sediments

A method for the accurate determination of Cd and Pb isotope compositions in sediment samples is presented. Separation of Cd and Pb was designed by using an anionic exchange chromatographic procedure. Measurements of Cd isotopic compositions were carried out by multi-collector inductively coupled plasma mass spectrometer (MC-ICPMS), by using standard-sample bracketing technology for mass bias correction and Pb isotopic ratios were determined by thermal ionization mass spectrometry (TIMS). The factors that affect the accurate and precise Cd isotope compositions analysis, such as instrumental mass fractionation and isobaric interferences, were carefully evaluated and corrected. The Cd isotopic results were reported relative to an internal Cd solution and expressed as the δ^114/110Cd. Five Cd reference solutions and one Pb standard were repeatedly measured in order to assess the accuracy of the measurements. Uncertainties obtained were estimated to be lesser than 0.11‰ (2s) for the δ^114/110Cd value. Analytical uncertainties in 2s for Pb isotopic ratios were better than 0.5‰. The method has been successfully applied to the investigation of Cd and Pb isotope compositions in sediment samples collected from North River in south China.