Planning and certification of new multielemental reference materials for research in antarctica

The adoption of the principles of Good Laboratory Practice (GLP) and the implementation of the ensuing procedures for quality assurance (QA) and quality control (QC) of analytical determinations are nowadays deemed essential to the achievement of sound, credible and comparable experimental information. This is certainly also applicable to research projects currently being carried out in the antarctic continent, in particular as regards investigations on global change phenomena. Worldwide investments made so far in this field do require in fact that reliability of data be optimized so as to allow for a harmonized assessment of ongoing trends. In this context the Italian National Programme for Research in Antarctica has recently launched a project for the preparation of new multielemental certified reference materials (CRMs) to be used for QC of analyses performed on environmentally significant materials. The suitability of CRMs to verify the accuracy of experimental measurements acknowledgedly depends, among others, on the degree of similarity of their matrix composition and analyte levels to those expected for real samples. From this standpoint three CRMs are planned, namely: i) marine sediment certified for Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sn and Zn; ii) ocean water certified for Cd, Cr, Cu, Fe, Hg, Mn, Ni and Pb; iii) krill certified for As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sn and Zn. Regarding the first two matrices, amounts of ca. 100 kg and ca. 1001, respectively, have been collected during the IX (1993–1994) antarctic expedition, while krill was taken in the course of the X (1994–1995) campaign. The pretreatment of sediment has been accomplished in terms of homogenization, stabilization and characterization of the preliminary ground mass. Approximately 500 bottles, each containing 75 g of material are now ready for distribution to interested laboratories involved in chemical measurements of antarctic matrices, whereas ocean water and krill will follow at a later stage. Finally, depending on circumstances, also the certification of organochlorine compounds in the same materials will be attempted.     

Interlaboratory comparison study for the determination of methyl tert-butyl ether in water

This is the first publication which describes the evaluation of the analytical performance and state-of-the-art of the determination of methyl tert-butyl ether (MTBE) in water at ng L^–1 concentrations. An interlaboratory comparison study for the determination of MTBE in water was carried out. Twenty-eight laboratories from seven European countries participated in the study. Twenty of those finally transmitted results to the organiser. Italian spring water, containing no detectable amounts of MTBE was fortified to yield two samples with MTBE concentrations of 0.074±0.004 µg L^–1 and 0.256±0.010 µg L^–1. The laboratories applied their regular in-house methods to analyse the water samples. Static headspace, Purge & Trap, solid-phase microextraction (SPME) or direct aqueous injection were used as sample preparation techniques. Subsequent separation and detection of MTBE were performed by gas chromatography/mass spectrometry (GC/MS) or gas chromatography/flame ionisation detection (GC/FID). After rejection of outliers, the overall arithmetic mean of laboratory results corresponded to recoveries of 78±20% (Sample A) and 88±20% (Sample B) of the reference concentrations. The between laboratory coefficients of variation (CV) were 32% and 31%, respectively. The organisation of the study and quality assurance measures at the organiser's laboratory are described. Moreover, the measurement results of the participants and the analytical methods used for the determination of MTBE are presented and the correlation between selected method parameters and data quality is discussed.     

Quality assurance in biological monitoring of environmental exposure to pollutants: from reference materials to external quality assessment schemes

The presence of chemicals in the environment is a matter of concern in that it poses potential health risks. At present, exposure to toxic chemicals and their biological and biochemical effects can be better estimated by biological monitoring, through the systematic collection of specimens from potentially exposed humans. Biological monitoring of human exposure to environmental pollutants is hampered by the difficulty to assess data reliability. As a consequence, the validity of biological monitoring should depend on the strict implementation of a quality assurance (QA) program, which includes a series of procedures aiming to ensure that laboratory results meet defined standards of quality and are reliable. For the validation and monitoring of methods’ performance, to ensure the trueness of measurements and to warrant the traceability to international standards, reference materials (RMs) and certified reference materials should be used. Internal quality control and external quality assessment (EQA) are part of overall QA and are carried out to verify that analytical errors are compatible with the specific requirements or needs of the user. In particular EQA schemes (EQAS) allow to test independently the analytical performance of participating laboratories. In the last decades, increasing concern has been raised by urban air pollution; lead and benzene, two gasoline components released by motor vehicle exhausts, are known to be toxic to humans. For biological monitoring of lead exposure of the general population, screening campaigns, utilizing lead in blood as a biomarker, have been carried out since the 1970s. Strict strategies were adopted to ensure data comparability, including the preparation of RMs, the organization of EQAS and the cross-exchange and analysis of blood samples between laboratories. Biological monitoring of benzene exposure could be carried out by means of various biomarkers such as benzene in blood and benzene, trans,trans-muconic acid (t,t-MA) and S-phenylmercapturic acid (S-PMA) in urine. At present, few RMs and EQAS are available for these biomarkers. A pilot EQAS for t,t-MA in urine, adopted to assess the reliability of data regarding benzene exposure, has been organized and carried out between 1996 and 1997 in Italy. From the accrued experience, it clearly emerges the importance of strategies designed to guarantee the quality of biological monitoring data. The use of RMs and the participation in EQAS are highly recommended in order to improve the global performance of methods and laboratories involved in biological monitoring.     

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.     

A survey of workload, facilities and awareness of uncertainty of measurement among Italian laboratories performing analyses in occupational and environmental medicine

Biological monitoring is essential for risk assessment in the presence of exposure of workers or the general population to harmful chemical agents. Besides the choice of analytical methods which are fit for purpose and the skills of the analysts, the performance of laboratories, including those working in the field of environmental and occupational medicine, also depends on other technical factors such as frequency of testing, the use of well maintained and properly functioning equipment and the implementation of quality control procedures including the participation in External Quality Assessment Schemes (EQAS). Surveys of laboratory workload have been organized periodically since 1997 within the MeTos Project, an Italian national EQAS for biomarkers of environmental and occupational exposure to chemical agents. In 2001, a more extensive survey, including specific technical issues, was organized as part of the activities of the Thematic Network of European Organizers of External Quality Assessment/Proficiency Testing Schemes Related to Occupational and Environmental Medicine (Network survey). In addition, information on the awareness and implementation of the new requirement for laboratories to estimate the uncertainty of their measurements was collected since 2000. The results of these surveys are reported and compared here. In all surveys, Pb in blood was the biomarker most frequently determined. As for biomarkers of exposure to organic compounds, the data collected in the Network survey indicate that methylhippuric acid, hippuric acid and mandelic acid in urine were the assays most commonly performed. About a third of the participants stated that they estimate the uncertainty of at least some of their measurements. Preliminary analysis of data, limited to Pb in blood, showed that analytical performance improved with continuous participation in EQAS and was positively influenced by a high workload.     

Determination of suspended particulates matter of major significance to human health using nuclear techniques in kenya

Energy dispersive X-ray fluorescence (EDXRF) analysis of aerosol samples in Nairobi is presented. Results show that elemental concentrations are of the order of 10^–4 to 10^–6 g/m³ for most elements analyzed. The total suspended particulate (TSP) matter was between 30–80 g/m³ for the entire sampling period between December 1993 to October 1994. Levels of lead (Pb) are below WHO guidelines. However, the obtained bromine (Br) to Pb ratio: 0.3–0.51, shows the origin of Pb to be from vehicular emissions. This ratio was particularly high during the months of April to July 1994 which were also found to be very active in terms of weather parameters.     

Polychlorobiphenyls in Antarctica

The presence and the distribution of polychlorobiphenyls (PCBs) in Antarctic environmental components and the effect of the seasonal formation/melting process of pack ice on the pollution level of seawater were investigated. Seawater, marine, and lake sediment and soil samples were collected in a large area of the Ross Sea and Victoria Land during the 1988–1989, 1989–1990, 1990–1991, and 1991–1992 Italian expeditions. The results obtained highlighted a low and quite homogeneous PCB contamination of the studied area. Surface seawater samples from Gerlache Inlet and Wood Bay showed a typical PCB concentration of 130 pg/liter, and an increase after pack ice melting of about 30–40%. Marine sediment, lake sediment, and soil samples showed normalized mean PCB contents of 150, 240, and 130 (pg/g)/(m²/cm³), respectively.     

Estimates of uncertainty of measurement from proficiency testing data: a case study

The results obtained by a laboratory over a number of proficiency testing/external quality assessment schemes (PT/EQAS) rounds can give information on the uncertainty of its measurements for a given test, provided that conditions such as full coverage of the routine analytical range, traceability, and small uncertainty of the assigned values (compared to the spread of the results) are met and provided that systematic deviations and any other sources of uncertainty are considered. As organisers of the Italian EQAS (ITEQAS) in occupational and environmental laboratory medicine, we tested this hypothesis using as model data from well-performing laboratories taking part in ITEQAS for lead in blood over the last 2 years. We also investigated how different PT/EQAS features (frequency of trials and number of samples) would affect a laboratory estimate of its uncertainty. Such information can be helpful in improving PT/EQAS organisation and define, for a given test: (a) the state of the art of the uncertainty of current measurement procedures, (b) identify needs for improvement of analytical methodologies and (c) set targets for acceptable uncertainty values.Presented at the Eurachem PT Workshop September 2005, Portorož, Slovenia.Papers published in this section do not necessarily reflect the opinion of the Editors, the Editorial Board and the Publisher.     

Swedish interlaboratory trials on proximates and certain macro minerals

Summary During the period 1980–1986 a number of samples representing different kinds of food items were distributed to about thirty laboratories for analysis. The objective was to test the laboratories with respect to their analytical skill in proximate analyses. Towards the end of the period the condition for analyses and the statistical technique had been developed in such a way that variations could be estimated within laboratories (repeatability) as well as between laboratories (reproducibility). An ellipse was constructed so that the probability for a randomly selected laboratory to fall within the ellipse would be 95%. This presentation also gives an example of wether mean values and standard deviations for a specific item change depending on the time between two courses of analysis.     

Blood lead and cadmium determination: Results of the Italian external quality assessment scheme

The procedures adopted in the Italian external quality assessment scheme (EQAS) for blood Pb (B-Pb) and Cd (B-Cd) determination, including the preparation of control materials, are described. Each scheme involves the use of internal quality control materials and the participation in periodical external quality assessment trials. All control materials are prepared at the Laboratory of Clinical Biochemistry, Italian National Institute of Health (Istituto Superiore di Sanità, ISS), as the reference centre. Computerized procedures have been adopted whenever possible, i.e. sample randomization, data transfer and treatment. The analytical performance of the participating laboratories, evaluated from the results obtained in ten years of activity, is reported. A total of eight phases has been carried out between 1983 and 1993. Over the course of these ten years, a positive trend was observed for B-Pb towards a smaller bias and a lower percentage of laboratories with poor performance. In the eighth phase, taking into account the results from all participants, the mean absolute inaccuracy for B-Pb was 32 g/l (mean Pb concentration in control samples, 165 g/l). The percentage of laboratories providing results within established acceptability limits for at least 80% of the examined samples (good performers) increased with time from 28% in the first phase to 48% in the last phase. The laboratories providing less than 50% of acceptable results (poor performers) decreased from 35% in the first phase to 22% in the last phase. As regards B-Cd, mean absolute inaccuracy decreased from 0.96 g/l to 0.55 g/l between the first phase and the sixth phase. The percentage of good performers increased from 45% to 62% and that of poor performers decreased from 31% to 5%. From the seventh phase a large group of new laboratories agreed to participate in the EQAS for B-Cd and the inaccuracy rose to 0.75 g/l (mean concentration: 2.7 g/l) and the percentage of poor performers rose to 24%, whereas the percentage of good performers remained almost unchanged.     

Developing external quality assessment programmes for primary health: care level in resource limited countries

Laboratory services are an essential component of health care delivery in tropical countries and play a vital role in improving the accuracy of clinical diagnosis and the investigation of disease outbreaks. In developing countries, laboratories face numerous constraints to providing quality services, including poor selection of techniques, difficulties in equipment availability and maintenance, and shortages of supplies, staffing and supervision. Currently in the eastern African countries (Kenya, Tanzania and Uganda), internal quality control procedures are inconsistently carried out in most laboratories. National External Quality Assessment Schemes (EQAS) have been established in all countries addressing a limited number of tests, but are constrained by difficulties of sustainability and poor coverage. The Laboratory Programme of the African Medical and Research Foundation (AMREF) has been operating a simple EQAS for primary heath care laboratories since 1993. Tests addressed are those carried out in primary health care laboratories in eastern Africa. A total of 81 laboratories from 5 countries in the eastern African region have participated in the scheme since 1993 and 9 distributions were submitted since the start of the scheme. No laboratory participated in all distributions; 24 (30%) laboratories participated in 4 or more distributions. Of these, the hospital laboratories in Kenya and Tanzania showed improved average mean scores between the first two and subsequent distributions. The educational benefit of participation in the scheme is emphasised. There was an overall low rate of participation of laboratories (35%) once the scheme was expanded to include laboratories outside direct AMREF project activities. Contributing factors include shortages of staff and lack of time in busy rural laboratories, together with difficulties in communication; however, the voluntary nature and lack of appreciation of the benefits of participation may also play a role. To increase participation in the scheme and to address the quality of laboratory services throughout the region, AMREF is currently developing a Regional EQAS in collaboration with the Ministries of Health of Kenya, Tanzania and Uganda, in affiliation with the World Health Organisation (WHO). The approaches used to establish reference values for haemoglobin samples are discussed. The scheme has also been utilised to examine the performance of different techniques for haemoglobin estimation, demonstrating the inaccuracy of the visual comparator methods. Received: 13 April 2002 Accepted: 5 July 2002     

Anti-HIV quality assurance programs in Australia and the southeast Asian and Western Pacific regions

Anti-HIV testing is the most regulated area of laboratory medicine in Australia. These regulations have placed the National Sero-logy Reference Laboratory, Australia (NRL) in a unique position to implement a comprehensive quality assurance (QA) program for HIV testing. The elements of our QA program include pre-market evaluation of assays, external quality assessment schemes (EQAS), quality control, specificity monitoring, consultations, and training workshops. The results of the NRL EQAS for Australian laboratories were compared with those of a program developed by the NRL for reference laboratories in the Southeast Asian and Western Pacific (SEAWP) regions. For laboratories authorized to use tests for HIV in Australia, participation in the entire QA program is mandatory, whereas the SEAWP EQAS program is voluntary. While the overall percentage of discrepant results for these programs are similar, the percentage of false negatives, variation in laboratory results, and choice of assay differ. These differences have decreased with time with improvements in assays and laboratory testing practices. The educational component of both EQAS, which comprises workshops, laboratory questionnaires, consultancies, and newsletters, has had a critical impact on the testing practices of laboratories. Received: 30 October 2000 Accepted: 9 December 2000     

Selenium Determination in Biological Matrices

In this study, we discuss some relevant aspects concerning the determination of selenium in biological materials with special reference to fluorometry and hydride generation atomic absorption spectroscopy (HG-AAS) techniques. The two methods may be applied without modifications to the analysis of Se in a wide spectrum of specimen types, and we describe their reliability in serum and hair analyses. Thirty-six independent control serum samples, the concentrations of which were unknown to the analyst, were analyzed in duplicate using both techniques in the Italian External Quality Assessment Scheme (EQAS). Accuracy was assessed by comparing Se values with those previously assigned by the organizers of the scheme using graphite furnace atomic absorption spectrometry (GF-AAS), which is the most frequently used technique for selenium determination in serum among the participants in the Italian EQAS. The results confirmed that fluorometry has a higher degree of accuracy than HG-AAS: the mean differences between observed and expected values were 1.5 μg/liter (95% confidence interval, −1.06 to 3.97) for fluorometry and −1.1 μg/liter (95% confidence interval, −5.05 to 2.76) for Hg-AAS. We also report some results obtained for the determination of Se in hair. Since a critical step in hair preparation is the pretreatment for removal of external contamination, we compared six different washing procedures. In general, Se is poorly leached from hair, but the efficiency of removal differed with the substance used, ranging from 0 to 13% of the original content. A nonionic detergent like Triton X-100 offers the advantage of safe working conditions and a substantial reduction in costs compared with organic solvents. Lastly, in a consistent group (n= 131) of women, Se in hair was found to be strongly reduced by the use of dye (389.9 ng/g vs 498.7 ng/g,P< 0.001). We recommend recording information on cosmetic treatments when hair is collected to evaluate Se reference values in epidemiological studies.     

Trace element determination in seawater by ICP-SFMS coupled with a microflow nebulization/desolvation system

Direct and simultaneous determination of Al, Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Pb, Sb, U, V and Zn in diluted (1:10 v:v) seawater from the Antarctic Ocean and the Venice Lagoon at the ng mL^–1 and pg mL^–1 level has been performed by using an inductively coupled plasma sector field mass spectrometer (ICP-SFMS). Samples were analysed by using a PFA microflow nebulizer coupled with a desolvation system or a PFA microflow nebulizer coupled with a Teflon spray chamber, respectively. Measurements were carried out at low (LR, m/m=300), medium (MR, m/m=3,000) and high (HR, m/m=7,500) resolutions depending on the studied isotope. To avoid contamination, sample pre-treatment was carried out in a clean laboratory equipped with a Class 100 vertical laminar flow hood. Concentration ranges (minimum–maximum in ng mL^–1) found in the Antarctic seawater samples (in depth profiles) were: Ag 0.0004–0.0018, As 0.69–1.32, Cd 0.031–0.096, Co 0.018–0.065, Cr 0.18–0.46, Cu 0.04–1.58, Fe 0.13–1.63, Mn 0.02–0.12, Mo 5.97–12.46, Pb 0.007–0.074, Sb 0.033–0.088, U 0.5–1.9, V 0.6–2.5 and Zn 0.16–0.80. Concentration ranges (min–max in ng mL^–1) found in the Venice Lagoon water samples (temporal profile from a benthic chamber experiment) were: Al 0.24–0.61, Ag 0.007–0.031, As 1.42–2.27, Cd 0.050–0.182, Co 0.440–1.461, Cr 0.15–0.34, Cu 0.81–2.46, Fe 0.25–1.66, Mn 11.6–31.7, Mo 6.50–10.6, Pb 0.047–0.225, Sb 0.240–0.492, U 1.7–3.3, V 1.3–2.8 and Zn 5.20–21.5. The detection limits range between 0.06 pg mL^–1 for Ag and U to 15 pg mL^–1 for Fe. In order to check the accuracy of the analytical procedure, measurements of the trace elements in a certified reference material (coastal Atlantic seawater, CASS-4-NRCC) were compared with the certified values. In addition, the results from the Antarctic and Venice Lagoon samples were compared with those obtained by using different analytical techniques.     

Determination of total, organic solvent extractable, volatile and tetraalkyllead in fish, vegetation, sediment and water samples

Procedures for the determination of total, hexane extractable, volatile and tetraalkyllead in fish, vegetation, sediment and water samples are given. Detection limits, better than those obtainable by any other published methods, are in the range of 10–50 ppb-total Pb, 2-ppb-hexane extractable Pb, 0.5–1.5 ppb-volatile Pb and 0.5 ppb-tetraalkyllead. Standard reference samples from National Bureau of Standards were used as controls where applicable and satisfactory agreement was obtained between accepted values and values obtained by the proposed procedure.     

Fallout241Am concentration in food and human tissue

Americium and plutonium concentrations in food samples and human tissue samples were determined using alpha-ray spectrometry.Food samples, representative of the average dietar intake over a period of 30d in Japan, were pruchased in Akita during 1985 and 1986. The food was divided into six groups: cereals, vegetable, fruits/beans, seaweeds, fish/shellfish, and meats/eggs/milk. Most of the. total ingestion of both Pu and Am was contributed by seaseed and fish/shellfish. The concentration of Am in the other food groups was low.A compoarison of the measured²⁴¹Am/^239+240Pu ratio in human liver with the predicted value of the ICRP-30 or ICRP-48 model showed that the half-life of Am in the liver is approximately 2–10y. The human tissue samples were obtained from subjects who died in Akita and Niigata Prefectures in northern Japan during 1981–1984. The median concentration of²⁴¹Am was 1.4 mBq/kg-wet in the stemum (n=11), 3.4 mBq/kg-wet in the liver (n=19), and 0.5 mBq/kg-wet in the lung (n=15). The ratio of²⁴¹Am/^239+240Pu was 0.34 in the sternum, 0.12 in the liver, and 0.14 in the lung.     

Determination of heavy metals at the pg/g level in Antarctic snow with DPASV and IDMS

Summary Differential pulse anodic stripping voltammetry (DPASV) and isotope dilution mass spectrometry (IDMS) were used to analyse heavy metals in Antarctic snow samples. It was possible to determine Pb and Cd with DPASV at the German Antarctic station Georg-von-Neumayer whereas the analyses of Pb, Cd, Tl, Cr, Ni, Cu, Zn, and Fe with IDMS were carried out at the University of Regensburg. 80% of the elemental concentrations in surface snow samples analysed with IDMS lay in the following ranges: Pb=3–40 pg/g, Cd<0.2–3 pg/g, Tl<0.2 pg/g, Cr<0.8–15 pg/g, Ni<4.8–40 pg/g, Cu<11–30 pg/g, Zn=30–500 pg/g, and Fe=(0.5–1.5)×10³ pg/g. In most cases an acceptable agreement between the DPASV and IDMS results was obtained for Pb and Cd. More than 50% of all Pb analyses agreed within a deviation of 0–10 pg/g. The Cd results between both methods usually deviated by less than 1 pg/g. Slightly higher Pb concentrations were analysed in the average with IDMS compared with DPASV. This effect was not observed for the Cd data. A possible explanation for this fact are non-ionic Pb species in the melted snow samples, which cannot be analysed by DPASV. One particular investigation of Pb concentrations showed that the analysed data with DPASV decreased with the increasing length of sun-shine after a snowfall when samples of the same origin were determined. Blank control is the major requirement for accurate analysis results of heavy metals in this low concentration range. On the other hand, accuracy must always be tested by independent analytical methods. In this work it is shown that Pb and Cd can be analysed directly in the Antarctica with DPASV and that the result of this method is in acceptable agreement with the definitive method IDMS.

---

Bestimmung von Schwermetallen im pg/g Bereich in antarktischen Schneeproben durch differentielle Pulsinversvoltammetrie und massenspektrometrische Isotopenverdünnungsanalyse

     

Preparation and testing for homogeneity of spiked strawberry and cabbage candidate reference materials

Strawberry and cabbage candidate reference materials (RMs) have been prepared by our laboratory during 1992–1993. Fresh materials have been homogenized and spiked with known concentrations of pesticides representing compounds commonly used for strawberries and cabbages. The candidate RMs have been then freeze-dried, homogenized, bottled under a stream of nitrogen and stored frozen at –20°C. Homogeneity and stability of the candidate RMs have been studied during the storage period. Homogeneity of the candidate RMs for 5 g samples has been within 10%. Homogeneity and stability studies have been carried out using the conventional multiresidue method of Luke et al. [1]. Instrumental analysis have been performed by gas chromatography mass spectrometry (GC-MS) employing selected ion monitoring (SIM).     

Adsorption and adsorptive separations: A review and bibliographical update (1994)

This paper provides a review of the 1994 journal literature and complete bibliography concerned with adsorptive separations. The references are taken from the 45 most important chemical engineering journals. This paper provides an update to the literature as provided in previous bibliographic papers (Ray 1990; 1991; 1995). References for membranes and membrane-type separations (for 1992–1993) were the subject of a separate bibliographic paper (Ray 1994), due to the number of papers now published on this topic each year. A review and bibliography paper covering 1994 for membranes has been submitted for publication. Bibliographic papers covering traditional unit operations (Ray 1992; 1993; 1994; 1994) and supercritical extraction (Ray 1994) have been published. A bibliography of the chemical engineering journal literature from 1967–1988 has been published by the author (Ray 1990), and can provide access to a wider range of topics. A complete bibliographic listing of the chemical engineering journal literature from 1989 to 1994 (with subsequent six-monthly updates) is available on a CD-ROM database (Published by Royal Melbourne Institute of Technology) and full details can be obtained from the author.     

Particle size distribution of metals in the atmosphere of Madrid (Spain)

Summary The size distribution of six metals (Cd, Cu, Fe, Mn, Ni and Pb) present in the atmosphere of Madrid was determined in the airborne particulate matter. Samples were collected in an area located in the University Campus in Madrid. Twenty-one samplings were carried out in two different periods: summer 1986 and autumn — winter 1986–87. AAS was employed in the analysis. The particle size distribution of the elements was bimodal. The most toxic metal studied (Cd, Ni and Pb) have extremely high proportions in the smallest particle size range, which can easily enter the respiratory tract lodging in the alveoli. For the metals the enrichment factors based on soil proportions are calculated on each stage. The values are higher for lead, cadmium and nickel, tending to vary from stage to stage, suggesting significant pollution sources.