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 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 50-X8, Dowex 1-X8) 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, conventional 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 for the separated iron species was 15 micrograms with a relative standard deviation (RSD) of +/- 3% and, using the conventional method of analysis, 2-5 micrograms with an RSD of +/- 1%. On the basis of these results the system was applied to the determination of the ratio of iron(II) to iron(III) in wines.
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 airacetylene and dinitrogen oxideacetylene flames. Interferences that were pronounced in an airacetylene flamewere almost eliminated in a dinitrogen oxide -acetylene flame, so the latter was employed for the determination of chromium. Extraction of Cr2072-into isobutyl methyl ketone was used to concentrate chromium from plant digests and soil extracts; Cr3+ in these solutions was efficiently oxidised by (NH4)2S208. Dry ashing followed by removal of silica was used for digestion of plants. Soil extracts (Na2EDTA) should be ashed before the oxidationextraction procedure. Total chromium in soil samples was determined without a pre-concentration procedure.
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 of 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 analytical 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 analyses of two sets of soil samples showed that the majority (80-90%) of samples can be analysed with an accuracy of k2Oy'. This should be acceptable in most applications where a large number of samples are to be analysed. Considerable amounts of time and chemicals can be saved. The method was also found to be suitable for the determination of lithium, calcium, strontium, barium, aluminium, chromium and titanium.
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