Aluminium spectrophotometric methods

An early spectrophotometric method [ 1 ] for aluminium in soil involves the use of a Technicon sample changer, proportioning pump and automatic colorimeter. The method is based on the measurement of the rate of colour development in the reaction between aluminium and xylenol orange in ethanolic media. The calibration graph is rectilinear up to 2.7 mg/1 aluminium and the coefficient of variation is 4.5%. 

Garcia Gutierrez [19] has described an azo coupling spectrophotometric method for the determination of nitrite and nitrate in soils. Nitrite is determined spectrophotometrically at 550 nm after treatment with sulfuric acid and N-1 -naphlhylclhylcnediamine to form an azo dye. In another portion of the sample, nitrate is reduced to nitrite by passing a pH 9.6 buffered solution through a cadmium reductor and proceeding as above. Soils were boiled with water and calcium carbonate, treated with freshly precipitated aluminium hydroxide and active carbon, and filtered prior to analysis by the above procedure. 

Parker, D.R., Zelazny, L.W. and Kinraide, T.B. (1988b) Comparison of three spectrophotometric methods for differentiating mono- and polynuclear hydroxy-aluminium complexes. Soil Sci. Soc.Am.J., 52, 67-75. 

Spectrophotometric methods that can be used for aluminium speciation in natural waters have been discussed [8],... 

Spectrophotometric methods have been described for the determination of copper, iron, cobalt and manganese in trichlorosilanes and in silicon tetrachloride186 boron in silicon tetrachloride and in hexachlorosilane187 and iron and aluminium in silicone polymers189. 

In general terms, sensitivity of the sp>ectrofluorimetric method is much higher than that of the spectrophotometric method. However, fluorescence reagents and methods suitable for the determination of iron are scarce and they suffer from serious interference of some metal cations such as aluminium, cop>p)er, and tin or they require a matrix separation step. Also, the reagents used for the determination of iron have a risk of toxicity (Tamm Kalb, 1993 Van et al., 1992 Cha et al., 1996 Ragos et al., 1998). Therefore, it is still important to develop simple and economical procedures that could be directly applied to real samples without the matrix separation step and with minimized reagent consumption. 

After adjusting to 2 mol 1 1 in hydrochloric acid, 500 ml of the sample is adsorbed on a column of Dowex 1-XS resin (Cl form) and elution is then effected with 2 M nitric acid. The solution is evaporated to dryness after adding 1M hydrochloric acid, and the tin is again adsorbed on the same column. Tin is eluted with 2 M nitric acid, and determined in the eluate by the spectrophotometric catechol violet method. There is no interference from 0.1 mg of aluminium, manganese, nickel, copper, zinc, arsenic, cadmium, bismuth, or uranium any titanium, zirconium, or antimony are removed by ion exchange. Filtration of the sample through a Millipore filter does not affect the results, which are in agreement with those obtained by neutron activation analysis. 

The determination of an inorganic analyte in an inorganic matrix, e.g. aluminium in rocks, requires the use of classical methods of separation, possibly complexation and a final determination which is designed to remove the effect of interferents by use of a specific chemical reaction(s) or spectrophotometric measurement at a wavelength which is specific to the analyte to be determined. Even so, the ability of this approach to eliminate interference from other elements (or compounds) must be established. 

The same three spectrophotometric reagents were compared for their abilities to differentiate mono- and polynuclear hydroxy-aluminium complexes in solutions typical of those used in phytotoxicity studies (Parker et al., 1988b). Methods based upon each of the three reagents yielded estimates of the mononuclear aluminium fraction of adequate precision for most purposes. Studies using ferron demonstrated its utility for characterising the non-mononuclear aluminium fraction using kinetic analyses. The ferron spectrophotometric procedure was preferred for its simplicity, level of precision and moderate rate of reaction with aluminium. 

The extraction method using 8-hydroxyquinoline is not very sensitive, but it is highly selective. The really sensitive methods for spectrophotometric determination of aluminium are based on ternary systems, including triphenylmethane reagents (mainly Chrome Azurol S and Eriochrome Cyanine R) and some surfactants. 

The thiocyanate method has been used for determining cobalt in vitamin B12 [94], steel [24,94], and nickel [25]. Cobalt present in considerable amounts in alloys with aluminium, nickel, chromium, manganese, copper, and iron was determined by the differential spectrophotometric analysis [95]. 

Another possibility is to take advantage of the individual treatment of every assayed sample. For sample lots with high variability in, e.g., pH or ionic strength, the required adjustments can be made in accordance with a prior assay performed in-line. This approach was proposed for the spectrophotometric determination of total nitrogen in Kjeldahl digests of plant leaves [397], As the method was very susceptible to sample acidity, which varied from sample to sample, individual sample pH adjustment was needed. To this end, an alkaline solution was added to every sample and the amount added was determined according to a pH-orientated feedback mechanism. This innovation was further applied to the spectrophotometric determination of aluminium in plant digests [398] and iron in estuarine waters [399], characterised by pronounced variations in... 

Al, Si, P Digestion with diethyl ether-concentrated sulphuric acid-potassium persulphate. Silicon determined gravimetrically. Aluminium determined by titrimetric EDTA method. Phosphorus determined by spectrophotometric molybdenum blue method. 

METHOD 65 - DETERMINATION OF IRON, TITANIUM AND ALUMINIUM CATALYST RESIDUES IN POLYALKENES AND POLYALKENE COPOLYMERS. ASHING - SPECTROPHOTOMETRIC PROCEDURE. 

Dissolve the aluminium in about 50 cm of water and 3 drops of nitric acid by boiling. Complete the determination of aluminium by the spectrophotometric procedure as described in Method 65. Run a blank, taking care to use the same quantities of all reagents as used in the determination. 

The Analytical Methods Committee of the S,A,C. has described a method for the determination of traces of magnesium, based on the method of Hunter. In this method, after destruction of organic matter, the magnesium is complexed with Titan Yellow and the excess dye is extracted from the reaction mixture and determined spectrophotometrically. The method is generally applicable but zinc, if present in quantities greater than 10 per cent of the magnesium content, interferes and should be removed. Aluminium, cadmium, cobalt and nickel interfere also. The recommended procedure is as follows ... 

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