Anders Cedergren

Aluminium concentrations in the brain and bone of rate fed citric acid, aluminium citrate or aluminium hydroxide

Male Sprague-Dawley rats were treated daily by gastric intubation (6 days/wk) with 100 mg aluminium/kg body weight in the form of aluminium hydroxide (9 wk) or aluminium citrate (4 wk), with citric acid (4 wk) or with tap-water (control, 9 wk). Young adult and aged Wistar rats were treated with 100 mg aluminium/kg body weight as aluminium hydroxide or with carboxymethylcellulose (vehicle controls). The cerebral cortex, hippocampus, cerebellum and samples of bone from each rat were analysed for aluminium, after digestion with nitric acid, using graphite furnace atomic absorption spectroscopy. The mean aluminium concentrations detected in the control Sprague-Dawley rats were 0.013-0.022 microgram/g wet weight in the various brain regions and 0.355 microgram/g in the bone. No significant increase in tissue aluminium concentrations was observed in Sprague-Dawley or Wistar rats after treatment with aluminium hydroxide. However the rats treated with aluminium citrate showed significantly increased concentrations of aluminium in all the brain regions studied (0.057-0.121 microgram A1/g) and in the bone (12.9 micrograms A1/g). Elevated aluminium concentrations in the cerebral cortex and bone were also observed in the animals fed citric acid suggesting possible absorption of the citrate chelate presumably formed with the traces of aluminium present in the diet.

Investigations of reactions involved in flameless atomic absorption procedures

Abstract In order to study the interference from chlorine in the flameless a.a.s. method for lead in steel, high-temperature equilibrium calculations were applied to a system containing Fe, Pb, C, Cl, S, H, O, N and Ar. The temperatures as well as the input amounts of elements considered could be varied over a wide range, and a survey of the most important parameters governing the system was thereby obtained. The results indicate that a sample must be ashed in the presence of a sufficiently large amount of hydrogen and at a temperature of about 900 K in order to remove the chlorine from the graphite tube. Otherwise, the volatile lead chlorides PbCl 2 , and PbCl are formed, which results in a decreased signal from lead.

Investigations of reactions involved in flameless atomic absorption procedures : Part II. An experimental study of the rôle of hydrogen in eliminating the interference from chlorine in the determination of lead in steel

Abstract The role of hydrogen in eliminating the interference from chlorine in the flameless a.a.s. method for lead in steel has been experimentally studied with the Perkin-Elmer HGA 72 and Varian-Techtron CRA 63 graphite furnaces. Hydrogen is generated at high temperatures in both systems by the reaction of graphite with water left in the tube after the drying step. The amount of hydrogen formed during the ashing procedure in the Perkin-Elmer tube is about five times larger than that in the Varian tube. The removal of chlorine from graphite tubes containing dissolved steel samples has been determined as a function of temperature for (i) the CRA 63 without hydrogen added, (ii) the CRA 63 with hydrogen added, and (iii) the HGA 72 without hydrogen added. At 950 K, a significant amount of chlorine is left only in case (i); thus the amount of hydrogen formed in the HGA 72 is large enough to remove all of the chlorine through the reaction FeCl 2 (g) + H 2 (g) → Fe(s) + 2 HCl(g). If a sample is ashed at 950 K, losses of lead as lead chlorides only occur for the case (i) which is in accordance with theoretical prediction. The theoretically predicted optimum ashing temperature range of 900–1000 K is shown to be in good agreement with the experimental results.

Conditions for sulfite stabilization and determination by ion chromatography

Abstract The efficiencies of three groups of potential sulfite-stabilizing compounds were found to be in the order: carbonyls > alcohols = saccharides. A mole ratio of 1:1 between formaldehyde and sulfite was sufficient for stabilizing a sulfite solution for at least 72 h. The lower stabilizing efficiencies of the alcohols and saccharides examined could be compensated by using large excesses of these compounds. For example, if a 100-fold excess of glycerol over sulfite was used, the recovery of sulfite was 96% after 72 h compared with only 40% without addition of stabilizer. During separations by ion chromatography, almost no oxidation of the sample occurs provided the sample solution is directly injected into a deaerated eluent. For formaldehyde, the peak heights were found to depend on the molar ratio of the stabilizer to sulfite as well as on the concentration of sulfite. This effect was not found for the other stabilizers tested.

Investigations of reactions involved in flameless atomic absorption procedures: Part III. A study of factors influencing the determination of lead in strong sodium chloride solutions

Abstract The factors influencing the direct determination of lead in strong sodium chloride solutions with a Varian Techtron CRA 63 are discussed. The sodium chloride matrix affects the determinations in two ways: (i) non-specific absorbance causes poor precision (the standard deviation for 50 p.p.b. of lead in 4 % sodium chloride was 11 % and the detection limit 11 p.p.b.); (ii) the sensitivity is decreased by about 20 %. Addition of nitric acid to the sodium chloride solution does not improve the sensitivity but decreases the non-specific absorbance to a very low value. This sample treatment improved the standard deviation for 50 p.p.b. of lead in 4% sodium chloride to 4% and the detection limit to 4 p.p.b. After treatment of the sodium chloride solution with nitric acid, the matrix is mainly sodium nitrate; if this matrix is not ashed at a sufficiently high temperature, the sensitivity decreases. At low ashing temperatures, the partial pressure of oxygen, as a result of incomplete reaction between oxygen and graphite, exceeds 10−5 atm during atomization so that, theoretically, the formation of gaseous lead oxide is significant and responsible for the decrease in sensitivity.

Investigations of reactions involved in flameless atomic absorption procedures: Part 7. A Theoretical and Experimental Study of Factors Influencing the Determination of Silicon☆

Abstract The ideal conditions for the determination of silicon by graphite-furnace atomic absorption spectrometry have been investigated by using high-temperature equilibrium calculations. All reasonable reaction products resulting from the reaction between Si, C, O, H, S, N, Ar and Na have been considered. The results show that SiO2(s) is the stable silicon compound for temperatures below 1500 K. For higher temperatures Si3N4(s), SiC(s), SiO(g), SiO2(s), Si(g), SiN(g), SiCl2(g) and SiS(g) are the main silicon-containing reaction products. SiO(g) is always formed in the interval 1600–2200 K independently of the partial pressure of oxygen. The basic requirement for the quantitative formation of silicon atoms at 2600 K is that the partial pressure of atomic oxygen is less than 10-12atm. The main condition for the formation of silicon carbide is an extremely low partial pressure of oxygen. Losses of silicon by the formation of SiO(g) during heating of the graphite tube were experimentally shown to be reduced by using isothermal atomization. An equilibrium model for the formation of silicon atoms is discussed. This model takes into consideration the decrease in the partial pressure of oxygen during the atomization step. The results obtained show that silicon atoms are formed from SiO(g) at the temperatures pertaining to the beginning of the atomization cycle and from SiC(s) at somewhat higher temperatures.

Reaction rates between water and the Karl Fischer reagent

Reaction rates between water and the Karl Fischer reagent have been determined by potentiometric measurement for various compositions of the Karl Fischer reagent. The study has been made with an iodine complex concentration of 0.3-1.2 mM and sulphur dioxide complex at 0.01-0.5M. The concentration of excess of pyridine had no measurable effect on the rate of the main reaction. The reaction was found to be first-order with respect to iodine complex, to sulphur dioxide complex, and to water. The rate constant was (1.2+/-0.2) x 10(3) 1(2). mole(-2). sec(-1). In an ordinary titration it is therefore essential to keep the sulphur dioxide concentration high for the reaction to go to completion within a reasonable time. The extent of side-reactions was found to be independent of the iodine concentration at low concentrations. The side-reactions increased somewhat with increasing sulphur dioxide pyridine concentrations and decreased to about 60% when the temperature was lowered from 24 degrees to 7 degrees.

Investigations of reactions involved in flameless atomic absorption procedures : Part V. An Experimental Study of Factors Influencing the Determination of Aluminium

Abstract An experimental study of various factors influencing the flameless a.a.s. determination of aluminium in graphite furnaces is reported. Even in very low amounts, oxygen, hydrogen, chlorine, sulphur and nitrogen cause interferences during atomization. In addition, hydrogen and chlorine interfere during the ashing step. The interferences are discussed on the basis of high-temperature equilibrium calculations. The interferences can be minimized by using an ashing temperature as high as possible. Hydrogen, in particular, significantly lowers the ideal ashing temperature; its interference increases with the age of the graphite tube and in the presence of iron. The exclusion of atmospheric gases such as oxygen and nitrogen from the tube is an essential requirement for obtaining reliable results.

Investigations of reactions involved in flameless atomic absorption procedures : Part IV. A theoretical study of factors influencing the determination of aluminium

Abstract High-temperature equilibrium calculations are used to study potential interferences in the determination of aluminium by flameless a.a.s. The conditions for the formation of interfering aluminium compounds like AlO(g), Al 2 O(g), Al 2 O 3 (s), AlOH(g), AlH(g), AlHO 2 (g), AlS(g), AlN(g), AlN(s) and AlCl(g) have been calculated. The influence of kinetic parameters on the equilibrium calculations for the reactions involving carbon—oxygen and carbon—sulphur has been established by varying the input amount of carbon. The results indicate that even in the nanomole range the presence of elements like H, O, N, Cl and S may cause severe interferences during the atomization step (2300–2900 K)

Determination of water by flow-injection analysis with the karl fischer reagent

Abstract A method for the determination of water in organic solvents by flow-injection analysis (f.i.a.) is described. The method, which is based on the reaction between water and the Karl Fischer reagent, is capable of 120 determinations per hour. The concentration range 0.01–5% (v/v) of water can be covered by using a single Karl Fischer reagent solution. The results obtained with a specially constructed potentiometric detector showed a relative standard deviation of less than 0.5% (v/v). This value was about 3 times less than that obtained with a spectrophotometric detector. The f.i.a. technique is shown to offer some unique possibilities in minimizing interferences associated with the standard Karl Fischer batch titration method.