Anders Sparen

The Determination of Quickly Reacting Aluminium in Natural Waters by Kinetic Discrimination in a Flow System

Abstract Different aluminium species react with oxine at different rates, a behaviour that we have used as the basis of an analytical method. The reaction is performed in a FIA system and is terminated by extraction of the excess oxine, together with the aluminium trioxinate formed, into chloroform. The reaction time is 2.3 sec, much shorter than that used normally. After separation, the amount of aluminium trioxinate in the organic phase is determined spectrophotometrically. The system has been validated using model substances with known complexation constants. Al3+, AlOH2+, probably Al(OH)2 +, aluminium sulphato complexes and, to some extent, some of its weakest organic complexes are included in the measured fraction, whereas fluoro complexes, citrato complexes and Al13O4(OH)7+ 24 are excluded. Complexes with fulvic and humic acid cause a reduction of the signal. The detection limit is at best about 5 μg/L (ca. 0.2 μM), and we can make 60 measurements per hour. Results from measurements made on natural ...

Analytical methodology for the determination of aluminium fractions in natural fresh waters (Technical Report)

Chairman: D. G. Westmoreland (USA); Secretary: M. W. Linscheid (Germany); Titular Members: M. J.-F. Leroy (France); M. Morita (Japan); H. Muntau (Italy); M. J. Pellin (USA); B. Ya. Spivakov (Russia); Associate Members: S. Caroli (Italy); W. P. Cofino (Netherlands); L.-G. Danielsson (Sweden); J. S. Edmonds (Australia); G. Friedbacher (Austria); D. M. Hercules (USA); J. Hlavay (Hungary); A. E. Maier (Belgium); L. Reutergkdh (Thailand); G. R. Rhodes (USA); W. Wegscheider (Austria); D. E. Wells (UK); National Representatives: Marina B. A. Vasconcellos (Brazil); W. Lund (Norway); Carmen Camara (Spain); S. Giiqer (Turkey).

A mechanized system for the determination of low levels of quickly reacting aluminium in natural waters

Abstract A continuous flow system has been connected to a graphite furnace atomic absorption spectrometer. The system is used to determine low levels of “quickly reacting Al” (Al qr ) in natural waters. In the flow system, aluminium reacts with oxine for 2.3 s and the formed complex is then extracted into toluene. Iron interference is minimized with a masking buffer present in the reagent. Via a simple interface, the toluene extract is introduced into the graphite tube. Good repeatabilities (R.S.D. ca. 2%, n = 10) were obtained, both for standard solutions and for natural waters. The detection limit is −1 , and the sample throughput using 3 injections/sample, is ca. 10 samples h −1 . The system has been used for determining Al qr in tap water, and is well suited for aluminium fractionation in near-neutral waters.

Studies of aluminium complexation to humic and fulvic acids using a method for the determination of quickly reacting aluminium

We have recently presented a method for the determination of quickly reacting aluminium in natural waters based on kinetic discrimination in a flow system. This method has been further validated using both an isolated fulvic acid and natural humus-rich waters. Different reaction times were used, further clarifying the response of aluminium complexed with humic and fulvic acids. Equilibrium dialysis was also used as a reference method for comparison. With the reaction time used normally, 2.3 s, aluminium complexed with humic or fulvic acids was shown not to be measured with our method. These results suggest that our method may be used for studies of the complexation of aluminium with humic and fulvic acids. We have compared results from a series of solutions with varying concentrations of fulvic acids with calculations based on two different models obtained from complexation studies performed by potentiometric titrations and by equilibrium dialysis. The results show fair agreement and suggest that our method can be used for such studies. This approach is more sensitive and rapid than potentiometric titrations, enabling studies of humus interactions with aluminium at concentrations similar to those found in natural waters.

The influence of complexing agents on the solubility and absorption of aluminium in rats exposed to aluminium in water.

The influence of citrate (0–31mm), fluoride (0 or 2.6mM) and silicate (0 or 2.6mM) on the absorption of Al (0–18mM) was studied in rats. We tested the hypothesis that the solubility and absorption of Al increases in the gastrointestinal (GI) tract in the presence of the complexing agents. Male rats were exposed for 6 or 7 weeks to soluble Al in acidic drinking water (pH 2.5–3.0) with or without the complexing agents. At the end of exposure Al was fractionated in the stomach content, in order to study if the solubility of Al was changed after ingestion. Al absorption was estimated by Al analysis of the right femur bone. Speciation calculations indicated that citrate and fluoride caused formation of soluble Al-citrate (97%) and -fluoride (>60%) complexes in the water. Silicate did not affect the theoretical speciation. In all cases, a large fraction of soluble Al became insoluble in the stomach after ingestion. The concentration of soluble Al increased only in the presence of citrate or a mixture of fluoride and silicate, but citrate was the only complexing agent that influenced the absorption of Al in the rat. This indicates that the form of Al may be changed in the GI tract when soluble drinking-water Al is ingested, and that the solubility of Al in drinking water and GI tract may not be good predictors of the bioavailability of Al even when chelating agents are present.

A Modified Fia System for the Determination of High Levels of Quickly Reacting Aluminium in Aqueous Solutions

Abstract We have modified Clarke et al.s (1992) flow injection system for determining ‘quickly reacting Al’ (Alqr) in natural waters, to make it applicable also to solutions having high (> 1 mM) aluminium concentrations. By decreasing the flow rate of the carrier stream, thus diluting the sample on-line, and using a very small injection volume (12 μl), the upper end of the linear range has been increased from 2 mg Al/l to at least 30 mg/l. Good repeatability (RSD ⋍ 1–3%, n = 4) was obtained, both for standard solutions and for natural waters. The quantification limit was about 100 μg/l and the sample throughput ca. 120 injections/h. Validation with synthetic model systems (Al plus F and Al plus citrate) showed that the modified set-up gave a fractionation similar to the one of Clarke et al.s original system. The modified set-up was also tested on soil solutions, having Al qr concentrations in the range of 0.1 to 1.5 mM. The sensitivity to iron interference was largely reduced by.the modification. Howeve...

Bioavailability of labile aluminium in acidic drinking water : a study in the rat

The bioavailability of labile Al (Allab; Al3+, and monomeric hydroxo and sulfato complexes) in drinking water was studied in the rat. The hypothesis was that Allab in drinking water is more available for absorption in the gastro-intestinal tract than Al complexed in the rat feed. Male Sprague-Dawley rats were exposed to 4 mg Al/litre in acidic drinking water (pH 4-5) and 5 mg Al/kg in the feed for 10 wk. The Al intake of these rats was about twice that in a control group of rats that received Al only in the feed. Both a theoretical speciation calculation and a speciation analysis of the water in a flow injection system showed that more than 98% of the Al in the water was present as Allab. However, intake of this water did not result in increased levels of Al in the bone, liver or brain tissue of the rats. Al speciation in a simulated rat stomach indicated that Allab in drinking water is rapidly complexed by feed constituents as the water enters the acidic milieu of the stomach, resulting in a very low concentration of Allab. The concentration of dissolved Al was also low in comparison to the added amount of labile Al. The possibility of complex formation between Allab and feed components in the gastro-intestinal tract should be taken into account in further studies of the bioavailability of drinking water Al in experimental animals and in humans.

Mechanized method for measuring metal partition in n-octanol–aqueous systems. Partition of aluminium complexes

We have established a system combining a continuous-flow extraction system with an electrothermal atomic absorption spectrometer to evaluate the lipophilicity of metal complexes. Quantitative data are obtained by determining the conditional partition constants (D′) of such metal complexes between n-octanol and water. Extraction equilibrium is obtained in a liquid–liquid segmented flow. After extraction a fraction of pure n-octanol phase is separated with either a membrane or a non-membrane separator. Via a simple interface, the n-octanol extract is introduced into the graphite tube. The D′ value is evaluated from the ratio of the concentration of metal in n-octanol to that in aqueous solution. Good repeatability (sr approximately 3.5%, n= 10) is obtained both for standard solutions and for normal extracts from the continuous-flow extraction system. A D′ value as low as 3 × 10–5 can be determined by the present system. The precision, measured as the sr of the mean, is better than 10%. The sample throughput, using at least three injections per sample, is about three samples h–1. The system has been used for studying the partition of aluminium–citrate (AlCit) complexes to n-octanol. AlCit, the only aluminium–citrate species partitioning, was found to have a D′ value of 0.49 × 10–3. Further, conditional constants for aluminium in supernatants from rat feed slurries obtained from in vitro studies of gastro-intestinal absorption have been measured.