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the same adatom-surface combina- tion. Nathan S. Lewis performs chemical lithography on graphite in water by pulsing the bias applied to a STM tip. Various bias voltages re- sulted in surface pits or domes (7 A diameter, 1.5 8, high). His aim is to use these domes as reactive sites for the formation of chemical linkages to the surface and as nucleation sites for metal deposition.

The diversity and depth of study reported at Pittcon ‘91 was truely im- pressive. We look forward to having the opportunity to hear about the

progress made in these fields next year in New Orleans at Pittcon ‘92.

CLAUDIA COHEN, BRIAN DAVIS, JOHN JACKOVITZ, MICHAEL PREIGH, HWEIYAN TSAI and

ELIZABETH WISE

Dr. John Jackovitz is a research chemist at Westinghouse Science and Technology Center, Pittsburgh, PA 15235, USA. The other co-authors are graduate students un- der the direction of Stephen G. Weber, Department of Chemistry, University of Pittsburgh, Chevron Science Center, Box 44, Pittsburgh, PA 15260, USA.

Speciation of metal compounds (interrelation between chemistry and biology)

A report on the 4th IAEAC Hans Wolfgang Nijrnberg Memorial Workshop on Toxic Metal Com- pounds, les Diablerets, Switzer- land, 4-8 March 1991, and on the 2nd IAEAC Soil Residue Analysis Workshop, Lausanne, Switzer- land, ll-13March 1991.

Both meetings were held under the auspices of the International Asso- ciation of Environmental Analytical Chemistry and the Swiss Federal Office for the Environment, Forests and Landscape. Chairmen and co- chairmen were Werner Haerdi, Jo- seph Tarradellas, Ernest Merian, and G. R. Barrie Webster. Emphasis was laid on environmental analytical chemistry, on environmental chemis- try in waters and soils, on bioavail- ability, on (molecular) biochemistry, and on biological effects. Hans W. Dtirbeck commemorated Hans Wolf- gang Niirnberg and extended an invi- tation to the 5th IAEAC Hans Wolf- gang Nurnberg Memorial Workshop on Metal Compounds in Environ- ment and Life in Jiilich, Germany (spring 1995).

Sampling, sample handling, environ-

mental analytical chemistry Tolg (Dortmund) opened the

Workshop by discussing the role of

trace elements in living systems from the analytical point of view. Metal compounds may bind and be trans- formed in various ways, data reliabil- ity and limits of detection must still be improved, particularly if concen- trations are very low (e.g. in the case of platinum species) or in cellular an- alytical chemistry. Multi-stage pro- cedures must be understood and au- tomation is only appropriate where standard reference materials are available and calibration is possible. Stoeppler (Jtilich) evaluated trace and ultratrace analytical methods for total and methyl mercury determina- tion in precipitations, biota and soil, e.g. by ion-exchange CV-AAS. Chambaz (Geneva) has improved the performance of ion chromatogra- phy in urine and blood studies by using chelating silica columns. De Vitre (Geneva) used potentiometric based microelectrodes, polarogra- phic based microelectrodes, or volt- ammetric methods for the determi- nation of toxic metal compounds in nerve synapses and environmental samples. Since low currents are needed, microelectrodes may also be applied in resistive systems. Hirner (Munich and Essen) has developed specific sequential chemical extrac- tion that differentiates between com- plexes and isomers, e.g. to determine anthropogenic lead as opposed to

trends in analytical chemistry, vol. 10, no. 6,199X

natural lead. Filella (Geneva) de- scribed net binding energy distribu- tion determination as the basis for heterogeneous multicomponent sys- tem models for normalized functions in soil.

Heavy metal pollution in soil

Berrow (Aberdeen) reported on the translocation of heavy metals in uncontaminated and polluted soils. Fractionation into particle-size and sequential extractions were used to indicate the forms in which metals are held within profiles. Concentra- tion in the inhomogeneously distrib- uted clay must be considered, but some metals are preferably bound to organics. Newman (Geneva) dis- cussed the influences of pore vol- umes, pH, salinity, and colloid ex- change on metal concentrations and turbidity in soil packed laboratory columns. Domergue (Lausanne) dis- cussed metal mobility in soil profiles, particularly from soils into water and plants. Bioavailability of zinc com- pounds is higher than those of cadmi- um and copper (the latter may be bound to organic compounds and is desorbed into groundwater). The ef- fects of adding compost/granite were also explored in pot experiments. Ja- penga (Haren) studied how soil transport of inorganic pollutants is influenced by manure. Hani (Liebe- feld-Berne) presented an overview on heavy metal contents of Swiss top- soils and subsoils. Anthropogenic and natural concentrations were com- pared, e.g. copper compounds in ag- ricultural grassland, vineyards and potato plantations. Federer (Zurich) has determined the distribution, de- sorption and translocation of copper, zinc and cadmium compounds in soil fractions around a closed foundry. Sequential extraction and desorption, e.g. of cadmium ions from carbon- ates, were discussed, as well as com- petition-displacement reactions.

Specific soil contamination by metal compounds

Verloo (Ghent) explained the tasks of the FAO Sub-network of Trace Elements in Soils and Plants. Absorption and desorption of arsenic onto and from various soil fractions have been determined. AlAsO, may

trends in analytical chemistry, vol. 10, no. 6,199l 173

be in equilibrium with gibbsite and/or amorphous Al(OH),, FeAsO, with amorphous Fe(OH),. Leaching is controlled by complex compounds. Liming is not recommended, be- cause it increases leaching of arse- nates. Charlet (Berne) has studied immobilization (adsorption and pre- cipitation) and oxidation of heavy metals, particularly chromium(II1). Synchroton based EXAFS (ex- tended X-ray absorption fine struc- ture spectroscopy) is recommended for the examination of surface reac- tions. Cr(II1) may be coprecipitated with Fe(II1) or absorbed on Q- FeOOH or MnO, (oxidation and back-reduction by Fe(I1) or S(I1) is then possible). Wenzel (Vienna) dis- cussed the effects of fluorine and metal accumulation in six luvisols near a former aluminum smelter. Fluorine increases solubility of ex- changeable aluminum-dissolving amorphous Al-oxides, which makes leaching of aluminum to subsoils pos- sible. Other emitted metals have ac- cumulated in the topsoil.

Aqueous and atmospheric environ- mental chemistry, cycles

Johnson (DubendorfiZiirich) dis- cussed analysis and chemodynamics of chromium in a natural lake. Bind- ing to colloids, coprecipitation with Fe(OH), or FE(I1) ions, electro- chemical deposition, and selective complexation and separation were discussed. From redox reaction stud- ies it can be concluded that binding to organic matter is important, and that under anoxic conditions chromate is predominantly reduced by sulfide and Fe(I1). Schirmer (Bremen) ex- amined heavy metal bioavailability in polluted rivers, and considered in- fluences of salinity and tidal pump- ing. Partition coefficients between dissolved and particle-bound metal phases are useful indicators, since sediments, bacteria, plants and ani- mals are sinks, for instance in an est- uary. Keller (Zurich) analysed cur- rent uses of cadmium in Switzerland, showing shifts to large-scale non-reg- ulated applications and that the man- datory regulations cannot curtail its use. New applications include nick- el-cadmium batteries, unsealed bat- teries, emergency generators, semi-

conductors, photoluminiscence products, and silver-metal oxides. Yule (Karlsruhe) discussed specia- tion of rare metals (including the lan- thanides and actinides) in biological systems, including binding to trans- ferrin. She used centrifugal separa- tion, gel chromatography, and spe- ciation models (such as ESTA and PHREEQE).

Bioavailability and uptake by micro- organisms andplants, biomonitoring

Smith (London) discussed specia- tion and accumulated forms of metals during exposure, tissue con- centrations and their toxicity to plants. Sequential extraction and bioavailability of cadmium, thallium and zinc species were compared. Lanthanum may inhibit cadmium up- take in some cases, and on average 35% of the cadmium and 10% of the thallium is accumulated in insoluble forms in growth media. Vangrons- veld (Diepenbeek) has developed a biological test system for the evalu- ation of metal phytotoxicity at five industrial sites, which include hec- tares of barren ground near aban- doned smelters. He compared bio- availability, root weights, shoot lengths, and leaf areas, and found that for reclamation purposes, heat- treated aluminum silcate additives

may restore enzyme capacities. Krosshavn (Dragvoll) has examined soil samples by solid state i3C NMR using cross polarisation and magic angle spinning (CP-MAS). She de- scribed chemical properties of soil organic matter. Pine forest soils have the highest zinc binding capacity. Ri- beyre (Talence), an expert in multi- compartment ecotoxicology, pre- sented experimental ecosystems as biological models. Structures, abiot- ic parameters, and contaminants may influence interactions. e.g. in ef- fects of total mercury and of methyl- mercury chloride on macrophytes. Zeelie (Port Elizabeth) has studied the influence of copper, magnesium or zinc sulfate additions to selected antimicrobial agents to increase mi- crobial activities (antiseptics) with- out side-effects. He determined an- tagonistic interactions or potentia- tion, and chromosome-mediated re- sistance. Thoni and Schmid-Grob

(Zurich) discussed biomonitoring by mosses, and exchange by wet deposi- tion.

Biochemistry, (molecular) interac- tions, mutagenicity

Costa (Tuxedo, NY) organized the second poster session discussion. Pounds (Detroit) reported on experi- mental techniques to study cellular and molecular interactions of lead compounds with essential elements, such as alteration of iron homeostasis and perturbation of calcium-me- diated functions. Raspor (Zagreb) described complexing properties of metallothionein-like proteins in bi- valves in seawater, particularly in the presence of cadmium. Sunderman Jr. (Farmington, CT) reported on metal substitution in zinc finger do- mains. Autoradiograms show to which protein Zn, Cd, and Ni are bound (Mn does not bind). Some other metal ions revent non-specific binding. Transcriptor factor IIIA (and ~43) has a high affinity for Zn and Cu. Foreign metals in Zn fingers may cause carcinogenesis and terato- genesis by altering DNA-binding do- mains. Bronzetti (Pisa) discussed ge- notoxicity of vanadium compounds in yeast and cultured mammalian cells. Beyersmann (Bremen) pre- sented an excellent overview of toxic metal (particularly cadmium) ions and cellular regulation in mamma- lian cells, discussing extracellular factors, membrane receptors and in- tracellular receptors. Identified end products may be modified by en- zymes and (in)activated transcrip- tion factors. Control of Ca*+ homeo- stasis, interactions with single trans- ducing proteinkinase C, and interac- tions with gene expression (binding to metallo-regulatory elements of gene MTIIA) were studied, using hy- drophobic chromatography or immo- bilized metal affinity chromatogra- phy in addition to other techniques. Carcinogenesis via genotoxic or epi- genetic mechanisms was also exam- ined.

Uptake and biological effects of cad- mium compounds

Oberdorster (Rochester, NY) and Glaser (Hannover) discussed cadmi- um solubility in a suspension of cad-

174 trends in analytical chemistry, vol. IO, no. 6,199I

mium sulfide aerosols. Cd0 dust, CdCl,, CdSO,, and CdS show similar lung cancer incidence in rats within 18 months of continuous inhalative exposure, because CdS suspensions treated with ultrasonification and with light before entering inhalation chambers are substantially oxidized and ionized. From lavaged lung or cell monitoring studies it can howev- er be concluded that acute pulmo- nary effects are still cadmium species dependent. Dobrota (Guildford) studied adsorption and tissue distri- bution of cadmium in the mouse fol- lowing dietary uptake of cadmium from potato (retention is only about 0.8%; most is transported to the kid- neys and liver). Andersen (Odense) discussed occupational monitoring and the effects of DDC, TTD and Thiram on cadmium toxicokinetics. Ribas (Majadahonda/Madrid) com- pared metallothionein isoforms in- duced with cadmium, mercury and lead compounds after sample prepa- ration by high-performance liquid chromatography.

Uptake and biological effects of mer- cury compounds

Baraldi (Modena) reported on neurobehavioral and neurochemical effects induced by prenatal exposure to methylmercury. In principle ef- fects are not permanent. Avoidance latency after learning trials is possi- ble, and the binding of methylmer- cury chloride to [3H]glutamate is of long duration. Nielsen (Odense) looked at the effects of selenium compounds on mercury toxicokinet- its, particularly at interactions be- tween methylmercury ions and sele- nomethionine in pregnant mice. Organ distribution of the mercury species depends on the selenium spe- cies. He also monitored excretion of mercury absorbed placentally or dur- ing lactation.

Uptake and biological effects of alu- minum compounds

Sjoberg (Umea) discussed pro- gress in aquatic aluminum chemistry, differentiating between hydrated metal ions, hydrolytic and other complexes, and metal colloid com- plexes. Of special analytical and chemical interest are complexes with

organic ligands and their eventual precipitation. The formation of FeOAlOH+ and Al(II1) complexa- tion at goethite (FeOOH)-solution were also determined and inter- preted. Sheik-Osman (Padova) ex- plained in detail metal speciation of aluminum(III)carboxylates in aqueous solutions at pH 7.5. He compared Al(OH),, A1(OH)2+, Al(OH)l, Al(OH),, and the syn- thetic complexes Al(acac),, Al(malt), and Al(lact), by ‘H NMR. Progressive hydrolytic reactions and, for instance, the formation of the me- tastable Al(OH),(OH,), are now better understood. Precipitations are influenced by rate differences. D’Haese (Edegem) improved the value of serum aluminum-monitor- ing in dialysis patients by chemical (AAS), histochemical or histological bone biopsy, by DFO-test and/or by serum Al measurements. Patients with high Al levels also have low fer- ritin levels. DFO therapy keeps Al- serum levels low, but it is not univer- sally recommended. Favarato (Pa- dova) discussed the role of metal spe- ciation on the effects of Al(II1). He looked at morphological differentia- tion of murine neuroblastoma cells, e.g., due to interactions with the model substance (OHJ2+ >

Al(lact),(OH)- and using microscopy dem-

onstrated for the first time specific reactions at neurites. Schlatter (Schwerzenbach, Zurich) differen- tiated between dialysis encepha- lopathy from aluminum exposure and Alzheimer’s-type senile demen- tia. In the former ataxia and Al levels in organs lo-100 times above normal are observed, but no distinct mor- phological signs. Senile dementia is more controversial: it is a progres- sive cognitive impairment. No or only minor increased aluminum lev- els in the brain and other organs are measured, but we need better quan- titative analytical chemistry on the brain to explain the deviations found. In Alzheimer’s disease typical morphological features were de- scribed. In Guam patients Al accu- mulations are found in nuclear re- gions and cytoplasma, but probably do not have any relation to the ef- fects of the disease. Gallium-trans- ferrin binding capacity may be a

good bio-indicator. Studies are needed to determine the role of cen- tral amorphous aluminum silicate cores in senile plaques and in nucleo- somes. Also the potential conse- quences of drinking water contami- nation need to be investigated fur- ther.

Uptake and biological effects of sili- con, lanthanides and other less com- mon metal compounds

Dobrota (Guildford) has studied cellular uptake of lanthanide ele- ments, taking into account the for- mation of insoluble hydroxide col- loids under physiological pH condi- tions. He looked for instance at bind- ing of Eu+ and Eu-chelates. Tobler (Wurenlingen) determined silicon in spruce needles, and discussed corre- lations with concentrations of Fe, La, and other elements. Birchall (Run- corn) discussed the antagonistic ef- fects of silicon on aluminum bioavail- ability. For instance, hydroxyalumi- no-silicate species formed in water, are not adsorbed at gill surfaces. Oberdorster (Rochester, NY) dis- cussed the increased pulmonary tox- icity of ultrafine metal oxide parti- cles. Metal compounds are used in new technologies, where they are concentrated at surfaces (clusters). Inhaled Al,O,, TiO,, and Ga,O, can lead to pulmonary fibrosis and affect clearance by alveolar macrophage functions.

Uptake and biological effects of chro- mium and nickel compounds

O’Brien (London) presented new evidence for reactive chromium in- termediates, e.g. by ESR spectra of Cr(V). Cr5’ (BSG),GSSG.H,O has additionally been synthesized and has a half life of minutes. Hartwig (Bremen) discussed nickel interac- tions with DNA polymerases and co- mutagenic effects, induced by MMS, B[a]P and UV-light. Nucleoid sedi- mentation techniques allowed her to follow strand break induction and li- gation during repair. Ni(I1) appears to compete with the essential Mg(II). Costa (Tuxedo, NY) proposed the deletion of a senescence gene in mammalian X chromosomes as one of four mechanisms of nickel carcino- genesis. It seems that this process is

trends in analyticalchemistry, vol. 10, no. 6,199l 175

controlled by methylation of DNA. He compared various immortal and tumorigenic cell lines. Ni(I1) can also react with euchromatin which leads to a loss of a tumor suppressor gene. Sunderman Jr. (Farmington, CT) de- scribed a new test system for em-

bryotoxicity and teratogenicity of Ni2+ and Co*+, using embryos of Xe- nopus llaevis. The easy Petri dish test lasts four days. Severe changes to the skeleton, the eyes, the face, and the skin are determined under a micro- scope, and good dose-response

curves are obtained. Many other substances have also been tested.

ERNEST MERIAN

Dr. E. Merian, im Kirsgarten 22, CH- 4106 Therwil, Switzerland.

Software for finding groups in data

Peter J. Rousseeuw printer. (The output contains rough graphical dis- Antwerp, Belgium plays that are composed of ASCII characters.)

A collection of seven clustering programs, DAISY, PAM, CLARA, FANNY, AGNES, DIANA and MONA, is described. This package is particularly suit- edfor cluster analysis in chemistry.

The programs

Introduction This note describes a collection of seven computer

programs for cluster analysis. Their manual is a book’ which was written for the general user, who does not necessarily have any statistical background. The first chapter discusses various types of data (in- cluding binary variables, and matrices containing dissimilarities between objects) and helps the user to choose a clustering method. The remaining six chap- ters each cover a single clustering method, and can be read independently. The first half of each chapter gives a short description of the clustering method, explains how to use it, and analyzes some examples. The second half of the chapter (which may be skipped without loss of understanding) then dis- cusses the algorithm and its implementation, and re- lated methods in the literature.

DAISY: computes a dissimilarity matrix between objects that are characterized by variables (which may be binary, nominal, ordinal, quantitative, or a combination of these) or by similarities. It can also compute correlation-based dissimilarities between variables.

PAM (Partitioning Around Medoids): carries out a k-medoid partitioning2 of objects characterized by quantitative variables or by a dissimilarity matrix (possibly obtained from DAISY). The k-medoid method has frequently been applied to analytical chemistry, e.g. for the classification of iron meteo- rites3.

The seven programs are written for IBM PC/XT/AT microcomputers or compatibles with 640 kB of memory, running MS-DOS (version 2.0 or later). No graphics card is needed. A mathematical co-processor is not required, but the programs will run faster if there is one. The Fortran source codes of these programs are very portable, and they have been used on mainframe computers as well. The in- put is carried out by a simple interactive dialogue. The output is a plain ASCII file with lines of less than 80 characters, designed to fit on any screen and any

CLARA (Clustering Large Applications): uses a new algorithm4 to partition a set of objects having quantitative variables. CLARA does not store the inter-object distances, and is able to deal with large data sets with thousands of objects. Its main idea is to draw a sample from the set of objects and partition it into k clusters using the k-medoid method (this is done with the same algorithm as in PAM). Each ob- ject not belonging to the sample is then assigned to the nearest cluster, yielding a clustering of the entire data set. A measure of the quality of this clustering is obtained by computing the average distance be- tween the objects of the full data set and a central ob- ject in their cluster. After drawing five such samples and repeating this procedure for each one of them, CLARA keeps the clustering for which the lowest average distance was obtained.

FANNY (Fuzzy Analysis): provides a fuzzy clus- tering, whereby an object can belong to several clus-

01659936/91/$03.00. OElsevier Science Publishers B.V.