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Low capacity adsorbents, based on iminodiacetic acid and a crosslinked agarose, Novarosetrade mark, have been synthesised for the enrichment of metal ions. Test ions Cu(2+) with high, and Cd(2+) with a moderate affinity for the sorbent were selected. The study includes the effect of specific capacity and matrix composition on the rate of uptake and recovery of these ions. Using a column packed with 0.25 ml of a sorbent and a sample volume of 100 ml, Cu(2+) is quantitatively accumulated from all of the matrices studied even at a capacity of 6 mumol ml(-1) of adsorbent and a flow rate as high as 100 ml min(-1). The enrichment of Cd(2+) is affected by the matrix and for quantitative recovery the flow rate and capacity must be properly adjusted. In the presence of 0.01 M Ca(2+), a specific capacity of 45 mumol ml(-1) is needed for quantitative retainment and a flow rate of 100 ml min(-1), whereas a capacity of 10 mumol ml(-1) suffices at 10 ml min(-1). The advantage of low specific capacity on the removal of matrix elements has been demonstrated. A method based on the determination of conditional stability constants of the metal sorbent complex is suggested for predicting the sorbent capacity needed to acquire quantitative recovery and optimal matrix elimination.

The equilibrium and kinetic properties of an iminodiacetate (IDA) based chelating ion exchanger with a crosslinked agarose, Novarose™, as support has been investigated. The second and third acidity constants and some complexation constants of the ligand were determined for adsorbents with metal binding capacities of 140, 55 and 18 μmol ml −1 , respectively. The adsorbent of medium capacity showed fast adsorption and desorption of Cu(II), Cd(II), Ni(II) and Ca(II) both in the batch and column mode. It was found to be about 50 times faster than Chelex-100 (50–100 mesh) in accumulation of these metal ions in the batch mode. Studies of the adsorbent in a flow system, using a 5 mm × 6 mm i.d. column, indicated quantitative accumulation of Cu(II), Cd(II), and Ni(II) at volumetric flow rates up to 110 ml min −1 . Linear calibration curves with r > 0.999 and signal enhancement factors up to 1300 were obtained. Preconcentration by a FIA system connected to an ICP-AES instrument will make simultaneous measurement of ultratrace concentrations of a number of metal ions possible within reasonable cycle times due to the high flow rates which can be used with the adsorbent. Trace amounts of cadmium and copper in tap water were determined successfully at 60 ml min −1 . However, copper and nickel in tap water are strongly complexed and do not accumulate quantitatively even at low flow rates. Hence a sample pretreatment is needed. Copper was completely adsorbed after UV-treatment of the sample.

Exchange reactions between inorganic selenium species and chloride were studied on Dowex 1X8. The concentration exchange constants were determined with the batch technique at room temperature and used to predict the chromatographic enrichment and separation of tetra- and hexavalent selenium. A procedure for the determination of total selenium after digestion with permanganate and anion exchange preconcentration was also developed. The enrichment techniques were applied to the determination of Se(IV) and total dissolved selenium in drinking water and fresh water using flow injection hydride generation—atomic absorption spectrometry (HG—AAS). Results agreed with those obtained in a HG—AAS system where selenium was preconcentrated as hydrogen selenide in a trap at liquid nitrogen temperature.

The reduction of selenium(VI) to selenium(IV) in 4, 5 and 6M hydrochloric acid was studied at temperatures between 50 and 95 degrees . The reaction rate was determined by measurement of the selenium(IV) formed, by continuous-flow hydride-generation atomic-absorption spectrometry. The most notable feature of the reaction is the strong increase in rate with increasing hydrogen-ion concentration and temperature. The rate increases initially with chloride concentration at constant acidity (mixtures of hydrochloric and perchloric acid) but levels off to an almost constant value at high chloride concentrations.

Lead in fly-ash from a garbage incinerator has been determined by X-ray fluorescence spectrometry (XRFS) and a modified standard-addition method. To keep the attenuation properties of the spiked samples constant, decreasing amounts of an attenuation modifier [mercury (II) acetate] were added together with increasing amounts of the standard (lead nitrate). Linearity between fluorescence intensity and amount of lead was thus obtained, so the amount of lead in the sample could be evaluated by linear regression. The amount of modifier needed could be calculated from a simple expression. The method was validated by comparison with the results obtained by applying atomic-absorption spectrometry (AAS) to solutions made by leaching the fly-ash with strong acid. For 8 fly-ash samples, containing between 0.8 and 1.35% lead, the largest absolute difference between the two sets of results was 0.03%. Theoretical calculations based on a simplified version of the Sherman equation were performed to confirm the linearity of the modified standard-addition curves.

Bromine (20-40 ppm), chlorine (200-500 ppm), sulphur (0.2-3%) and phosphorus (300-1000 ppm) in peat have been determined by X-ray fluorescence spectrometry (XRFS) combined with the standard-addition method. Chlorine, sulphur and phosphorus have also been determined by other methods and agreement between the results is good. Theoretical calculations based on the Sherman equation were made to validate the linearity of the standard-addition curves. A multi-element standard-addition technique has been tested with addition of all elements at the same time. The results for chlorine were high but after correction for the difference in attenuation coefficient between the sample and added compound the results agreed with those from single-element standard addition.

Adsorption properties of a fast iminodiacetate-agarose adsorbent, IDA-Novarose, with a capacity of 120-140 mumol/ml were studied for preconcentration of eight transition elements. A FIA-ICP-AES system was used in the study. It was shown that 0.3 ml of the adsorbent, packed in a column, can quantitatively accumulate Cr(3+), Mn(2+), Fe(3+), Co(2+), Ni(2+), Cu(2+), Zn(2+) and Cd(2+) from standard solutions in the pH range between 4 and 8 at high loading flow rates (10-80 ml/min). The rate of adsorption was studied in batch experiments and found to be fast and equal for the divalent metal ions but relatively slow for accumulation of Cr(3+) and Fe(3+). On-line buffering of acidified samples improved the accumulation of metal ions from synthetic samples spiked with humic acid. Quantitative uptakes were observed for most of the studied metals. The accumulation of Cr(3+) was found to be quite sensitive to the ionic strength and some loss of inert complexes of Fe(3+) was also observed. The method was applied to the analysis of certified riverine water (SLRS-3), a tap water and a lake water. With few exceptions the results obtained by ICP-AES after preconcentration agreed well with the certified concentrations and results found by ICP-MS.

A spectrofluorimetric method for the determination of total selenium in biological samples has been developed. After oxidative destruction, the sample is reacted with a mixture of bromide and 2,3-diamino-1,4-dibromonaphthalene (Br 2 -DAN) without pH adjustment. Selenium(VI) is rapidly reduced by bromide to Se(IV) which then forms 4,7-dibromo-5,6-benzopiazselenol (Br 2 -DAN-Se). The conversion of Se(VI) to Br 2 -DAN-Se is completed in 6 min at 100°C. The piazselenol is extracted to cyclohexane and the fluorescence measured at 577 nm with excitation at 518 nm. The procedure has been validated by determinations on reference materials with selenium concentrations ranging from 4 to 1460 ng g −1 . The advantages of the method are the fast reduction of Se(VI) by hydrobromic acid and the properties of Br 2 -DAN, which permit the piazselenol formation to be carried out in a strongly acidic medium and at high temperature. The limit of detection is 0.6 ng g −1 as estimated by three times the standard deviation of the blank determination ( n = 7). The rate of reduction of Se(VI) to Se(IV) in hydrobromic acid was investigated as a function of concentration and temperature. The new kinetic data together with previous kinetic and equilibrium data for the piazselenol formation were used to model and optimize the simultaneous reduction-derivatization procedure.

An adsorbent for metal ions has been prepared by reacting high molecular weight polyethyleneimine (PEI) with a crosslinked and activated agarose gel, Novarose ™ . The synthesis variables, i.e. time, temperature, pH, PEI concentration and PEI/Novarose ratio, were optimized in order to obtain a high metal binding capacity of the adsorbent. The binding capacity for Cu 2+ is 500μmol/ml packed adsorbent. A number of properties of the adsorbent relevant for metal ion accumulation has been investigated for Cu 2+ , Ni 2+ , Cd 2+ and Zn 2+ . Adsorption capacities, adsorption isotherms, distribution coefficients, recoveries and relative rates of accumulation were determined. The adsorbent can be used for preconcentration and for separation of interfering alkali and alkaline earth metals in analytical applications.

A modified standard addition method for single element determination by X-ray fluorescence spectrometry has been studied. The attenuation properties of the standard added samples are kept constant by adding decreasing amounts of an attenuation modifier along with increasing amounts of a standard. In this way the standard addition curve will be a straight line in cases where the ordinary standard addition curve is non-linear, and linear regression can be used to evaluate the concentration of the analyte. Standard additions of oxides of a number of elements, with and without modifier, have been made to cellulose powder or a mixture of aluminium oxide and polyethylene as matrices in order to test the method. The method has been applied to the determination of zinc in fly-ash from a steel work and of iron in cement. The fly-ash contained about 5% of zinc and the cement samples between 2 and 5% of Fe(2)O(3). The results were compared with those obtained by ICP-AES after decomposition of samples in lithium tetraborate or lithium metaborate and dissolution of the melt in 10%(v/v) nitric acid. The results agreed within 2%, relative, for fly-ash and within 3-6%, relative, for cement samples.

A cold trap system for the determination of selenium by hydride generation-atomic absorption spectrometry (HG-AAS) is described. For a 30-ml sample the limit of detection is

Determination of the degree of substitution, D.S., of purified sodium carboxymethylcellulose, CMC, by potentiometric titration has been studied. Different mathematical descriptions of the acid-base properties of polyelectrolytes were tested on the titration curve. It was found that the extended Henderson-Hasselbalch equation reproduced the measured data well. It was therefore used as a basis for evaluating D.S. by the simplex method. The influence of ionic strength, I, on the shape of the titration curve was investigated and the effect of I on the precision of the titrations was evaluated. The titrations showed a precision of +/- 0.004 D.S.-units and the results were in agreement with those obtained from a dry-ashing method, within +/- 0.02 D.S.-units. The whole method, including preparation of solutions and titration, showed a precision of +/- 0.01 D.S.-units.

A method has been developed for the determination of bromide in fresh water. The analyte is enriched on the anion-exehanger Dowex 1 × 8, which exhibits a considerably greater affinity for bromide than for the major anions in fresh water. Sodium perchlorate is used as eluent and an enrichment factor of ~100 can be achieved. The eluted bromide is oxidized with peroxodisulphate to bromate, which is determined iodometrically by a previously published spectrophotometric method. The enrichment in the presence of the major components of fresh water has been studied. Only bicarbonate has been found to interfere, but this interference can be avoided by acidifying the sample with hydrochloric acid. The recovery from synthetic fresh water with ionic concentrations corresponding to 0.005 equivalent/l. and spiked with bromide was 100% at bromide concentrations larger than 50 nM (4 μg l. ) and about 90% at 10 nM. The detection limit is 1.5nM and the limit of determination 5nM for 1-litre samples.

There are several procedures which use only a few points on the titration curve for the calculation of equivalence volumes in acid—base titrations. The accuracy of such determinations will depend on the positions of the points on the titration curve. The effects of errors in the stability constants and in the pH measurements on the accuracy of the analysis have been considered, and the results are used to establish the conditions under which these errors are minimized.

The peroxodisulphate method for the determination of bromide has been modified. A flow-injection system for the spectrophotometric finish has been developed and the size of the ion-exchange column in the preconcentration step has been scaled down. The sum of bromate and iodate produced in the oxidation is determined by treating the oxidized sample with iodide in hydrochloric acid. The iodate is separately determined by applying the reaction in acetic acid. The working range of the spectrophotometric finish is 1-15muM and the limit of determination (10 sigma) is 0.7muM for iodate and for iodate plus bromate. The enrichment factor in the preconcentration step is 50, yielding a limit of determination of 15nM for bromide in natural waters. Eighteen samples of water from the Baltic, with salinity ranging from 3 to 33%. have been analysed. A Br/Cl ratio of (1.53 +/- 0.02) x 10(-3) was found. A comparative study of the original and the new preconcentration step has been made with three river waters, rich in humic substances. The results agreed within +/- 1. 5%.

The exchange reaction 2R(+)HCO(3)(2-) + CO(3)(2-) right harpoon over left harpoon R(2)(+) CO(3)(2-) + 2HCO(3)(2-) has been studied on Dowex 1 x 8 in the presence of bicarbonate solution in equilibrium with atmospheric carbon dioxide (open system). The experiments showed, as theory predicts, that the composition of the resin phase is independent of the concentration of the bicarbonate solution. The mole fraction of carbonate at equilibrium is about 0.4 and the equilibrium constant is 0.15M at 20 degrees . With this value of the constant, the composition of the ion-exchanger for various bicarbonate concentrations has been calculated for a closed system. At [HCO(3)(-)]0.01M a substantial part of the resin is in the carbonate form, whereas for [HCO(3)(-)] 0.05M the resin is present almost exclusively in bicarbonate form. The exchange constants of bromide at trace level have been determined for the bicarbonate and mixed carbonate forms of the ion-exchanger. The exchange constant K(Cl)(HCO(3)) has been determined over the whole composition range and the results can be represented by K(Cl)(HCO(3))= 0.428 -0.063x(Cl) -0.115x(Cl)(2), where X(Cl) is the mole fraction of chloride in the resin. The constants are used to discuss the conditions for the Chromatographie enrichment of bromide from fresh water.

The lead content in fly-ash collected by an electrostatic precipitator has been determined by atomic-absorption spectrometry (AAS) after decomposition by four different leaching/dissolution techniques, and also determined by X-ray fluorescence spectrometry (XRFS) by the standard-addition method. The XRFS data were evaluated by non-linear regression since the standard additions affected the attenuation coefficient of the sample. Good agreement was obtained between the results obtained with AAS and XRFS. It is concluded that lead is quantitatively extracted by hot 1M nitric acid or treatment with hydrofluoric acid/nitric acid. Direct measurement of briquetted samples by XRFS is suggested for rapid monitoring of the lead content in fly-ash from garbage incineration.

Emf measurements on mixtures of carboxylic acids, HA, and the corresponding bases, A, containing a high and constant salt background, show that the equation E = E(0) + glnh + j(h)h commonly used in the calculation of equivalence volumes is not strictly followed. Terms linear in [HA] and [A] should be added. The origin of these terms is discussed briefly and their influence on the accuracy of equivalence-volume determinations is evaluated.

Two digestion procedures have been tested on samples of flour, blood and urine for application in the determination of selenium by hydride-generation atomic-absorption spectrometry. The first utilizes a mixture of concentrated nitric, perchloric and sulphuric acids and the second a mixture of magnesium nitrate hexahydrate, concentrated nitric acid and 6 M hydrochloric acid. The accuracy of the procedures was tested by analysis of standard reference materials and by comparison with results from neutron-activation analysis. It was found that the “magnesium method” can replace the more common procedure, which includes perchloric acid, for the sample types investigated in this paper.

A discussion of the conditions for the complexometric determination of the minor component in a mixture of two metal ions is presented. It is based on expressions of the Ringbom type for the titration error. These are derived by the use of logarithmic diagrams. The results have been used to devise an analytical procedure for the determination of the alkaline earth metals in the presence of a large excess of nickel or zinc.

The rate of the reaction between iodide and selenium(IV) at trace levels to form selenium and iodine has been determined in 1–6M hydrochloric acid. The reaction rate increases rapidly with acidity. When hydrochloric acid is added to reduce selenate to selenite prior to the determination of total selenium, some selenium may be lost by reduction to the element if iodide is present. A table of half-lives of the selenite—iodide reaction under various conditions is presented. A method for removal of iodide is suggested.

A flow system for hydride generation and atomic-absorption spectrometry is described, and the results from the optimization of the equipment for selenium determination are reported. For a sample volume of 0.6 ml the limit of detection for selenium was 0.1 mug l . and the imprecision less than 1% RSD at the 10-mug l . level. Four digestion procedures for selenium in bovine liver have been tested. All procedures gave concordant results, provided that the standard-additions method was used. The accuracies of the overall analytical procedures were estimated by comparison with results from neutron-activation analysis and analysis of NBS Bovine Liver, No. 1577. These comparisons proved that the accuracies of the procedures described in this paper are good.

An equation has been developed for the calculation of the titration curve of any mixture of acids and bases, and an alternative way of defining an equivalence point, suitable for computer calculations, is presented.