Dr. RADMILA MILAČIČ (AJLEC till 1989)
(contributed on international conferences with more than 60 lectures and posters)
Scientific papers:
R. Ajlec, J. Štupar:
J. Štupar, R. Ajlec:
R. Ajlec, J. Štupar:
R. Ajlec, J. Štupar:
R. Ajlec:
J. Štupar, R. Ajlec, J. Korošin, F. Lobnik:
R. Ajlec, M. Čop, J. Štupar:
R. Ajlec, J. Štupar:
R. Milačič, J. Štupar, N. Kožuh, J. Korošin and I. Glazer:
R. Milačič, J. Štupar, J. Korošin, N. Kožuh:
R. Milačič and J. Štupar:
N. Kožuh, J. Štupar, R. Milačič and B. Gorenc:
R. Milačič and F. Dolinšek:
R. Milačič and J. Štupar:
F. Cruz, S.A. Katz, and R. Milačič:
R. Milačič, H. Leskovšek, F. Dolinšek and D. Hrček:
N. Kožuh, R. Milačič and B. Gorenc:
B. Mitrović, R. Milačič and B. Pihlar:
N. Kožuh, R. Milačič, B. Gorenc, O. Abollino and C. Sarzanini:
R. Milačič, M. Čemažar and G. Serša:
R. Milačič, M. Benedik and S. Knežević:
Rapid determination of aluminium and iron in red mud by the suspension atomic absorption technique, Vestn.Slov.kem.Drus. 29, 295-305, (1982).
Determination of Al2O3 and Fe2O3 in red mud is required during the processing of bauxite in order to run the production of alumina under optimal conditions. Classical procedures are tedious and time consuming and thus less suitable for that purpose. The slurry injection atomic absorption technique was investigated in this respect. The suspension was prepared by mixing 0.5 of sample with 10 ml of HCl (1+1) for 10 minutes, and diluted to 100 ml with distilled water. Fe and Al were measured in an air-N2O-acetylene flame at 386 nm and an air-N2O-acetylene flame at 396.2 nm, respectively. e t, e ni and e ai values were measured for a series of samples. A correction was made solvent soluble fraction. On the basis of these experiments the accuracy of the procedure was evaluated. The analysis of three samples can be made in two hours with a relative accuracy ± 13% for Al and ± 9% for Fe. An alternative solution atomic absorption spectroscopy procedure employing a rapid fusion-dissolution sample pre-treatment was developed. A standard addition calibration was necessary for each sample and element in order to obtain maximal relative accuracy (± 3%). The method can be applied satisfactorily for routine use in an alumina production plant.
Study of the use of soil suspensions in the determination of iron, manganese, magnesium and copper in soils by flame atomic absorption spectrometry, Analyst 107, 144-156, (1982).
A method is described for the direct, routine atomic-absorption spectrometric determination of copper, iron, manganese and magnesium in soil samples of the terra rossa and peat types. An investigation was made on the factors influencing the atomisation efficiency of these elements when suspensions of soil samples were aspirated into the flame. Particle size, flame temperature and position in the flame were found to be critical in determining the fractions of particular elements atomised. Special emphasis was given to the preparation of the soil suspensions, which is the most critical step in the whole procedure. Magnetic and ultrasonic devices were used for stirring purposes. The latter proved to be more efficient, particularly when suspensions of high clay content soils are being prepared. An average standard sample made for each soil type was used for calibration. Test analysis of two sets of soil samples showed that the majority (80-90%) of samples can be analysed with an accuracy of ± 20%. This should be acceptable in most applications where a large number of samples are to be analysed. Considerable amounts of time and chemical are saved. The method was also found to be suitable for the determination of lithium, calcium, strontium, barium, aluminium, chromium and titanium.
Molekularna emisijska spektrometrija v nizkotemperaturnem plamenu: Določanje fosforja v rastlinskih materialih in odpadnem blatu, Vestn.Slov.Kem.Drus. 32, 51-68, (1985).
Molecular emission spectrometry in low temperature flame is a new spectroscopic technique convenient for determination of non-metallic elements such as phosphor, sulphur, nitrogen, boron and halogens. It is based on measurement of molecular emission appearing on the surface of a cold body immersed in a flame such as: hydrogen-nitrogen, argon-hydrogen or air-hydrogen-nitrogen. Belcher and co-workers developed so called MECA technique in which a sample is deposited inside a small metal or quartz cavity which placed in a flame acts as a cold body. In this work a construction of a MECA spectrometer is described. Emission due to HPO molecules is measured at 528.0 nm in a hydrogen-nitrogen flame. The effects of several parameters (flame composition, position of a cavity in the flame, chemical composition of the sample solution etc.) upon integrated emission intensity (I x sec) are investigated. The sensitivity of phosphorous measurement is strongly inhibited by the presence of various cations (with exception of H+ and HN4+) forming low volatile phosphates. Limit of detection 2 µ g P/ml phosphoric acid solution is achieved. Phosphorous is successfully determined in solutions of plant ashes after removal of cations by ion-exchange procedure.
A critical appraisal of the molecular emission cavity analysis technique in analytical spectroscopy, Vestn.Slov.Kem.Drus. 33, 87-104, (1986).
A critical appraisal of the molecular emission cavity analysis technique for determination of phosphorous, sulphur, chloride and iodide in real samples was made. Strong cationic interferences inhibited the formation of HPO, S2 InCl and InI molecules and the measurement of molecular emission. In phosphorous determination cations can be successfully removed by cation-excahnge when the acidity of sample solution is < 0.1M. In sulphur determination H3PO4 or its ammonium salts can be used for removal of cationic interferences. Due to the poor reproducibility of this pretreatment, the method cannot be satisfactory employed for analytical use and for determination of particular sulphur compounds. Determination of chloride and iodide is inhibited by cationic and spectral inerferences (In2 emission coincides almost exactly with the wavelength range of InI emission) so MECA technique cannot be applied for these purposes.
Optična emisijska spektrometrija v induktivno sklopljeni plazmi : Korekcija spektralnih interferenc, Vestn.Slov.Kem.Drus. 34, 243-258, (1987).
A basic problem of atomic emission measurements in an inductively coupled argon plasma (ICP) is the determination of the true net analyte signal of the measured element. Correction methods for spectral interferences are usually based either on the experimentally measured influences of the interfering elements and/or a correction calculated on the basis of tabulated data (line overlap only). In the present work, three characteristic types of spectral interferences were studied. Correction of spectral interferences due to line overlap: the example studied was measurement of Gd from the 342.247 nm ionic line in the presence of U, Cr, Ho and Fe. Correction of spectral due to simultaneous line overlap and variation of background: the case chosen was measurement of P from the 213.618 nm atomic line in the presence of Cu and Ca. Correction of spectral interferences due to variation of background: in this case by measurement of low concentrations of U from 385.958 nm ionic line in the presence of high concentrations of Zr.
J. Štupar, R. Ajlec, J. Korošin, F. Lobnik:
A comparison of spectroscopic methods for determination of phosphorus in plant materials, soil extracts and fertilizers, Landwirtsch. Forschung 40, 21-31, (1987).
A critical comparison was made of different spectroscopic methods (spectrophotometry, atomic absorption, MECA and ICP-OES) for determination of phosphorous in plant materials, soil extracts and various types of fertilizers. Different procedures were investigated for dissolution of solid samples (plant materials, fertilizers) and special care emphasis was given to the problem of avoiding losses of organically bound phosphorous present in these samples. Representative samples (NBS standard reference materials, etc.) were analysed in five parallel portions for phosphorous, dividing the sample solutions into four equal parts, each part being measured by one of the above mentioned method employing the same standards. he applicability of the particular method for routine use was estimated on the basis of the following characteristics: sensitivity, detection limit, linearity of calibration curve, useful concentration range, precision, accuracy, susceptibility to interferences, speed of analysis and simplicity of sample preparation procedure. In these respects ICP-OES seems to be the method of choice.
Interferences in the determination of chromium in plant materials and soil samples by flame atomic absorption spectrometry, Analyst 113, 585-590, (1988).
A method is described for the determination of chromium in plant materials and soil samples by flame atomic absorption spectrometry. Factors influencing the sensitivity of the method for chromium and cationic interferences were investigated in air-acetylene flame and dinitrogen oxide - acetylene flames. Interfernces that were pronounced in an air - acetylene flame were almost eliminated in a dinitrogen oxide - acetylene flame, so the latter was employed for determination of chromium. Extraction of Cr2O72- into isobutyl methyl ketone was used to concentrate chromium from plant digests and soil extracts; Cr3+ in these solutions was efficiently oxidised by (HN4)2S2O8. Dry ash followed by removal of silica was used for digestion of plants. Soil extracts (Na2EDTA) should be ashed before the oxidation - extraction procedure. Total chromium in soil samples was determined without pre-concentration procedure.
Determination of iron species in wine by ion-exchange chomatography - flame atomic absorption spectromety, Analyst 114, 137-142, (1989).
The direct coupling of ion-exchange chromatography to flame atomic absorption spectrometry (AAS) has been achieved by employing a Babington type nebuliser. The system enables all the processes on the column to be followed directly at a flow rates of between 1 and 5 ml min-1. The potential of the system was investigated for the determination of various iron species in synthetic samples containing iron(II) and iron(III) in ionic or chelated form by employing various ion-exchange (Dowex 50X-8, Dowex 1X-8) and sorptive (Amberlite XAD-2) resins, respectively. In some instances where direct coupling was impossible, owing to the physical properties of the effluent or eluent, convential analyses of chromatographically separated iron species were performed by flame AAS. The optimum concentration range, limit of detection, and reproducibility of measurement were also determined for a particular column capacity. When direct coupling was employed, the detection limit of separate iron species was 15 µ g with a relative standard deviation (RSD) of ± 3% and, using the convential method of analysis , 2-5 µ g with RSD of ± 1%. On the basis of these results system was applied to the determination of iron(II) and iron(III) in wines.
R. Milačič, J. Štupar, N. Kožuh, J. Korošin and I. Glazer:
Fractionation of chromium and determination of chromium(VI) in blue shavings, JALCA, 87, 221-233, (1992).
Blue shavings are a protein-based matrix with a high content of Cr(III) salts and organic polymers. If they contain excessive amounts of Cr(VI) they could be a potentially hazardous waste in the environment. Fractionation of Cr in blue shavings was studied by employing various sequential extraction procedures to determine the water-soluble, exchangeable, organically bound, carbonate, crystalline, hydroxide and sulphide fractions. Cr(VI) was determined in the phosphate buffer extractable (pH = 6.5 - 7.0) fraction. Results obtained by several analytical techniques indicate limitations in the determination of Cr(VI). Ion-pairing reversed phase HPLC combined with flame or electrothermal AAS was found to be affected by severe matrix effects due to organic polymers in blue shavings and high salt concentrations in the buffer and extractant solutions. Chelating ion-exchange and ion-exchange chromatography combined with flame AAS detection gave over-estimated results due to inefficient retention of inert Cr(III) complexes. Spectrophotometry (addition of diphenylcarbazide reagent to the analyte prior to acidification) and extraction of Cr(VI)-HCl complex into MIBK (277 K) gave generally comparable and reliable results. The detection limit for the former technique was 15 ng cm-3 and 2 ng cm-3 for the latter. Our investigations indicate that over 90% of total Cr in blue shavings is in chemically inert forms, approximately 8 percent is extracted with Na4P2O7 while less that 0.003 percent exists in the toxic chromate form.
R. Milačič, J. Štupar, J. Korošin, N. Kožuh:
Critical evaluation of three analytical techniques for determination of Cr(VI) in soil extracts, Analyst, 117, 125-130, (1992).
Three different analytical techniques [ 1,5-diphenylcarbazide spectrophotometry, chelating ion-exchange chromatography (Chelex-100), and ion-pairing reversed-phase high-performance liquid chromatography (RP-HPLC) combined with electrothermal atomic absorption spectrometry (ETAAS)] were critically evaluated for the determination of Cr(VI) in soil extracts. Spectrophotometry was not applicable to the analysis of moist soil extract samples owing to its high limit of detection (LOD = 30 ng cm-3), and the possibility of the instantaneous reduction of Cr(VI) under the acidic conditions employed. A Chelex-100 column although adequate sensitive (LOD = 1.5 ng cm-3), is inclined to give higher results as inert and moderately labile Cr(III) complexes partially passed through the resin together with Cr(VI). In addition, very small particles (< 0.45 µ m) carrying chromium can produce severe positive systematic errors. In order to avoid this, filtration employing 0.1 µ m filter is recommended. Ion-pairing RP-HPLC was found to be the most sensitive technique (LOD = 0.3 ng cm-3). It might also give high chromate results if negatively charged Cr(III) complexes from ion pairs with tetrabutylammonium phosphate and their elution partially coincided with that of Cr(VI). Fulvate ligands showed this type of interferences. Reversed-phase HPLC is not suitable for analysis of extracts obtained from soils with freshly added tannery waste owing to the effects of the undestroyed tannery waste matrix. This study showed that each method investigated was vulnerable to some type of interferences.
Simultaneous determination of Cr(III) complexes and Cr(VI) employing fast protein anion-exchange liquid chromatography - atomic absorption spectrometry, Analyst, 119, 627-632 (1994).
Chromium(III) complexes [ oxalate and ethylenediaminetetraacetic acid (EDTA)] and Cr(VI) were separated simultaneously on a fast protein liquid chromatography (FPLC) anion-exchange column of Mono Q HR 5/5. For separation tris(hydroxymethyl)aminomethane (TRIS)-HCl buffer (5 x 10-3 mol dm-3, pH 5.5-8.5), and the same buffer with NaCl (0.5 mol dm-3) were employed in gradient elution (15 min; flow rate, 1 cm-3 min-1). The column was regenerated (NaCl) and equilibrated (TRIS-HCl buffer) in the following 8 min. With this procedure, C(III) positive species and kinetically labile, negatively charged Cr(III) complexes such as Cr(III) citrate passed through the column, whereas relatively stabile anionic Cr(III) complexes (with EDTA and oxalate), and Cr(VI) were separated and determined by ultraviolet molecular (234 and 273 nm, respectively) and atomic (357.9 nm) absorption. Atomic absorption was measured "off line" in 100 or 200 µ l eluate fractions. The method was successfully employed for the determination of Cr(VI), Cr(III)-EDTA, and Cr(III)-oxalate in cabbage xylem at ng cm-3 levels [ limits of detection (LOD), 5, 3, and 80 ng cm-3, respectively] , using 500 µ l sample loop. In addition, chromate was monitored in Cr(VI) containing nutrient solutions during plant experiments to investigate Cr uptake by plants (LOD, 5 ng cm-3).
N. Kožuh, J. Štupar, R. Milačič and B. Gorenc:
Optimization of extraction procedure for determination of total water-soluble chromium and chromium(VI) in various soils, Int.J.Environm.Anal.Chem., 56/3, 207-217 (1994).
The parameters influencing the extraction efficiency of total water-soluble chromium and chromium(VI) in clay, peat and sandy soils were investigated. Water and a KH2PO4 solution (0.015 mol dm-3) were used as extractants. Samples were ultrasonicated or shaken in classical shakers. Variations of solution volume-to-soil weight ratio, and of shaking time were studied in order to develop the optimal extraction procedure for the determination of total water-soluble chromium and chromium(VI). Soil samples treated with tannery waste continuously for 17 years and soils freshly contaminated with the same waste were studied.
Determination of cadmium and lead in aerosols in the Zasavje region in Slovenia employing slurry electrothermal atomic absorption spectrometry, Int.J.Environm.Anal.Chem., 57, 329-337 (1994).
Investigations of air pollution were carried out in the Zasavje industrialized region in Slovenia. Cadmium and lead were measured in respirabile (< 2.5 µ m) and inhalable (2.5 - 10 µ m) aerosols. Special pumps were equipped with a Nucleopore-Costar polycarbonate membrane filters. Cadmium and lead were measured in those filters by slurry electrothermal atomic absorption spectrometry (ETAAS) on a laboratory-assembled atomic absorption spectrometer with a graphite cup atomizer. A reliability of the employed technique was proved by analysis of the same filters with classical dissolution of aerosol particles in diluted nitric acid and measurement of cadmium and lead by flame atomic absorption spectrometry (FAAS). Good agreement (± 5 - 10%) of the results was obtained between the two technique for both elements. The study indicated that cadmium and lead in a contaminated area prevailed in the respirable (< 2.5 µ m) aerosols. The employed technique was sensitive enough for measurement of cadmium and lead also in non-polluted sites.
Fractionation and oxidation of chromium in tannery waste and sewage sludge amended soils, Environm.Sci.Technol., 29, 506-514 (1995).
Clay, sandy and peat soils were mixed with tannery waste so that the final concentrations of total chromium were between 1500 and 2000 µ g g-1 and with sewage sludge where the final concentrations of total chromium ranged from 170 to 200 µ g g-1. The experiment was carried out for 2 years under atmospheric conditions. Fractionation of chromium was studied in these soils employing a sequential extraction procedure and oxidation of chromium by measurement of chromium(VI) in the water-soluble fraction. The results of fractionation studies in tannery waste-amended soils indicated that 5 months after the start of the experiment up to 1.1% of total added chromium was oxidized in clay, 0.45% in sand, and only 0.03% in peat soil. The concentration of the water-soluble chromium and chromium(VI) decreased in further continuation of the experiment since chromium was redistributed to more sparingly soluble fractions of soils. The process of chromium oxidation was not observed in sewage sludge-amended soils.
F. Cruz, S.A. Katz, and R. Milačič:
Determination of hexavalent chromium in CCA-treated building timbers, J.Environ.Sci.Health,Part A-Environm.Sci.Engineer., A30(2), 299- 306 (1995).
Alkaline extraction followed by atomic absorption spectrometry was applied to the speciation and quantification of chromium in CCA-treated building timbers. Total chromium was determined by atomic absorption spectrometry of specimens prepared by acid digestion. the specimens examined were found to contain 0.3 - 0.4% total chromium, and < 100 mg/kg of hexavalent chromium.
R. Milačič, H. Leskovšek, F. Dolinšek and D. Hrček:
A complex study of air pollution with cadmium, lead, polycyclic aromatic hydrocarbons, sulfur dioxide, and black smoke in the Zasavje industrialized region in Slovenia, Annali di Chimica, 85, 131-148 (1995).
Air pollution has been investigated from 1991 to 1994 in Trbovlje, Zagorje and Hrastnik, three towns in the Zasavje industrialized urban region in Slovenia. Cd and Pb were measured in aerosols continuously for three years employing direct electrothermal atomic absorption spectrometry, and polycyclic aromatic hydrocarbons (PAH's) for one year by gas chromatography and gas chromatography/mass spectrometry. In addition, SO2 and Black Smoke (BS) were monitored continuously during the period investigated. The study indicated that the concentrations of all the pollutants measured were highest in the heating seasons. In the wintertime the average monthly concentrations of SO2 were up to 30 times higher than in the summertime, and the concentrations of BS up to 8 times higher. This increase being up to 6 times for Cd, and up to 10 times for Pb. PAH's, with the exception of naphthalene, were not detected in the summertime, while in the wintertime the presence of these carcinogenic substances was very evident. In general, the degree of pollution is comparable to other urban and industrialized regions worldwide. The results indicated the substantial decrease of air pollution during the period investigated. The main reason for declination of SO2, Black Smoke, Cd and PAH's pollution being in the progressive change of the local heating system from coal to gas and in the gradual substitution of coal in coal-fired heating station with oil. The reason for Pb pollution decrease being in a substantial reduction of the Pb content in leaded gasoline during the period investigated and in increased consumption of unleaded gasoline.
N. Kožuh, R. Milačič and B. Gorenc:
Comparison of two methods for speciation of aluminium in soil extracts, Annali di Chimica, 86, 99-113 (1996).
The possibilities for aluminium speciation were investigated in the pH range 3.0 - 8.0 by employing column chelating ion-exchange chromatography - inductively coupled plasma atomic emission spectrometry (ICP-AES) and the 8-hydroxyquinoline spectrophotometric method. Before analysis the samples were filtered through 0.1 m m membrane filters. Aquo Al3+ and hydroxy- complexes of aluminium were retained by the column resin (Chelex-100, H+ form) and eluted with 1 mol dm-3 HCl. Separated positively charged labile monomeric aluminium species in the eluate were determined by ICP-AES, applying Y as an internal standard. At pH values higher than 5.0, prewashing with 0.025 mol dm-3 HCl was required before elution with 1 mol dm-3 HCl, to remove Al(OH)3 adsorbed on the column resin. The influence of some inorganic and organic complexing ligands on aluminium speciation was also investigated. A comparison with the conventional 8-hydroxyquinoline spectrophotometric method indicated good agreement of results for synthetic aluminium standard solutions. The results also agreed well with reported calculated data. Parameters influencing the extraction efficiency of total water-soluble aluminium in various soils were also investigated in order to develop an optimised extraction procedure for the determination of total water-soluble aluminium in soil extracts. Both methods were successfully employed in speciation of aluminium in aqueous soil extracts of neutral and acidic soils, where the LOD for the column chelating ion-exchange chromatographic technique was found to be 650 ng g-1, and for the 8-hydroxyquinoline spectrophotometric method it was 200 ng g-1 of positively charged labile monomeric aluminium species.
B. Mitrović, R. Milačič and B. Pihlar:
A novel approach to speciation of aluminium by employing fast protein cation-exchange liquid chromatography - inductively coupled plasma-atomic emission spectrometry, Analyst, 121, 627-634 (1996).
A fast protein liquid chromatography (FPLC) - ICP-AES procedure was developed for speciation of Al over a wide pH range, from acidic to alkaline region. Positively charged monomeric Al species in synthetic aqueous solutions were separated from polymeric, neutral and negatively charged species on an FPLC cation-exchange column. Aqueous-NaNO3 (8 mol dm-3) linear gradient elution was employed for separation in 10 min at a flow rate of 1.0 cm3 min-1. Separated Al species were determined "off line" by ICP-AES in 0.5 cm3 fractions which were diluted prior to analysis, using internal standard addition of yttrium. Retention times were found to be 1.5 min for Al(OH)2(H2O)4+ [ Al(OH)2+] , 4.0 min for Al(OH)(H2O)52+ [ Al(OH)2+] and 4.5 min for Al(H2O)63+ [ Al3+] . Good reproducibility of measurement (RSD 1.5%) was obtained in the optimal concentration range. LOD (3 s ) for separated Al species was found to be 120 ng cm-3 (1.0 cm3 of sample).
The distribution of Al species over a wide pH range is matched with the reported calculated data, and in general agreed also with the 8-hydroxyquinoline spectrophotometric method. Investigation of the effect of inorganic and organic complexing ligands on speciation of Al indicated that positively charged Al species (Al(SO)4+, AlF2+) and negatively charged (oxalate and citrate) coeluted with Al(OH)2+ and were separated from Al(OH)2+ and Al3+ species, while AlF2+ coeluted with Al(OH)2+ species. At lower pH's (e.g. 4.0) Al-citrate was partially coeluted with Al3+ and Al(OH)2+ species. The same observations were found when soil extracts were analyzed.
N. Kožuh, R. Milačič, B. Gorenc, O. Abollino and C. Sarzanini:
Speciation of aluminium in environmental water samples employing microcolumn chelating ion-exchange chromatography-ETAAS, Int.J.Environm.Anal.Chem., in press
A microcolumn chelating ion-exchange chromatography - electrothermal atomic absorption spectrometry procedure (ETAAS) was developed for aluminium speciation at the nanogram per millilitre level in water samples from the environment. Chelex-100 resin (100-200 mesh, H+ form) was filled into a micro column and connected to a peristaltic pump. Before analysis, the resin column was equilibrated to the pH of the particular sample analyzed. Sample was then pumped through the column at a flow rate of 0.5 cm3 min-1. Labile aluminium monomeric species were retained by the resin column and, after elution with 5 cm3 of HCl (1 mol dm-3), determined by ETAAS. At pH higher than 5.0, prewashing with 0.025 mol dm-3 HCl was applied prior to elution with 1 mol dm-3 HCl, to remove Al(OH)3 adsorbed on the column resin. The distribution of aluminium species over a pH range from 3.0 to 8.0 in synthetic standard solutions was closely matched by the 8-hydroxyquinoline spectrophotometric method and reported calculated data. Good reproducibility of measurement (± 1.5%) was obtained (10 ng cm-3 of Al, pH 4.0). LOD (3s ) for separated aluminium species (50 cm3 of sample) was found to be 0.3 ng cm-3. The influence of some inorganic and organic complexing ligands as well as the effect of high salinity, nonionic surfactants and an excess of alkaline-earth ions on aluminium speciation was investigated. The technique was successfully employed in determination of aluminium species in various water samples from the environment.
R. Milačič, M. Čemažar and G. Serša:
Determination of platinum in tumor tissues after cisplatin therapy by electrothermal atomic absorption spectrometry, J.Pharma.Biomed.Anal., in press
A simple procedure is described for the determination of platinum in tumours after cisplatin therapy. Tumours were digested in 65% nitric acid by incubation at 37o C for two days and platinum analysed under optimum conditions by electrothermal atomic absorption spectrometry with Zeeman background correction. The reproducibility of measurements in general was better than ± 2%. The calibration graph was linear from 30.0 m g l-1 up to 1000 m g l-1 of platinum, while the limit of detection (3 s ) was found to be 3.0 m g l-1 (sample volume 20 m l). Aqueous standard solutions and the standard addition method were applied in the calibration procedure. Under the recommended analytical conditions the sample matrix did not influence the determination of platinum significantly. In 72% of samples analysed the differences between results obtained by the two calibration procedures did not exceed ± 5%.
R. Milačič, M. Benedik and S. Knežević:
Adsorption-desorption processes of aluminium, zinc and copper on plastic tubing in haemodialysis monitors, Clin. Chim. Acta, 256, 169-182 (1997).
This study was performed to identify the source of contamination of dialysate with trace elements which had been observed in some haemodialysis centres in Slovenia. A possible explanation of this phenomenon was adsorption-desorption processes occurring on the plastic tubing in which dialysate was circulating in the haemodialysis monitors during dialysis. To confirm this, contamination of tubing with trace elements was simulated in vitro. After contamination, acetate or bicarbonate dialysates were prepared by the conventional procedure and samples of each dialysate collected in 1 ml fractions. Trace elements were measured by atomic absorption spectrometry. The haemodialysis tubing was contaminated for 0.5 or 4.5 hours with 1.85 or 7.41 µ mol/l of aluminium, 38.24 or 76.48 µ mol/l of zinc and 7.87 or 15.74 µ mol/l of copper. Steady state concentrations were reached after five minutes and ranged for aluminium from 0.18 to 0.67 µ mol/l, for zinc from 0.31 to 0.92 µ mol/l and for copper from 0.13 to 0.28 µ mol/l in acetate dialysate, and 0.15 to 0.56 µ mol/l of aluminium, 0.46 to 1.53 µ mol/l of zinc and 0.06 to 0.47 µ mol/l of copper in bicarbonate dialysate. The results suggested that adsorption-desorption processes are a probable source of contamination of the dialysate what could affect the health of haemodialysis patients.