A spectrophotometric method is described regarding the determination of germanium. A colored complex of germanium with pheny fluorone was collected on an organic solvent-soluble membrane filter made of cellulose nitrate. The complex, together with the filter, was dissolved into N,IV dimethylformamide (3 cm3), and the absorbance of the solution was measured. The obtained calibration curve was linear from 0.05 to 1.0 µg of germanium and the molar absorption coefficient was 1.9x 105 dm3 mo -' cm-'. The relative standard deviation of the absorbance obtained at 1.0 µg of germanium was 0.4% ( n=11). The interference of molybdenum(VI) could be eliminated by hydrogen peroxide. The time required for one run was about ten minutes and germanium at 1 µg dm-3 levels could be easily determined. This method has been applied to the determination of germanium in samples of hot-spring water.
A highly sensitive, rapid and facile method of fluorophotometry is described for the determination of phosphate using the ion pair formation of molybdophosphate with Rhodamine 6G. This ion pair is collected on a membrane filter made of cellulose nitrate when the sample solution is adjusted to 0.35 mol dm-3 in sulfuric acid, 1.9 mmol dm-3 in ammonium molybdate and 3.1 µmol dm-3 in Rhodamine 6G, and it is filtered through the membrane filter under suction. The membrane filter together with the ion pair is dissolved into Methyl Cellosolve. The fluorescence intensity of this solution is measured at 555 nm with the excitation at 535 nm. The calibration curve of phosphate is linear from 5 to 100 ng of phosphorus, with the correlation coefficient of 0.999; the relative standard deviation was 1.6% for 100 ng of phosphorus (n=12). Although arsenic(V) causes positive error, no ions, including silicate, commonly existing in natural water interfere with the determination of phosphate. The proposed method was applied to the determination of phosphate-phosphorus in water samples and satisfactory results were obtained.
Sensitive and accurate methods are described for the determination of phosphate, arsenate and arsenite in natural water using Malachite Green as an ion-pair reagent. The ion pair of Malachite Green with molybdophosphate is floated as a membrane-like substance at the phase boundary between the aqueous phase and a diethyl ether phase. After discarding the aqueous phase, methanol is added to dissolve the floated ion pair. The determination of phosphate is performed by measuring the absorbance of the organic phase. The apparent molar absorptivity of phosphate is 3.3 x lo5 1 mol-1 cm-1 at 620 nm. Arsenate is also determined using the same procedure. An oxidative or a reductive reaction of arsenic with potassium dichromate or sodium thiosulphate is utilised for the determination of phosphate, arsenate and arsenite. An extractionindirect atomic absorption spectrometric determination method was also developed in which the atomic absorption of molybdenum in the ion pair of Malachite Green with molybdophosphate is measured. The proposed methods were applied to the determination of phosphate, arsenate and arsenite in some natu ra I water samples.
A sensitive and accurate spectrofluorimetric method is described for the determination of phosphate in natural water using Rhodamine B as an ion-pair reagent. A Rhodamine Bmolybdophosphate ion pair was floated as a membrane-like substance at the phase boundary between the aqueous phase and a diethyl ether phase. After the aqueous phase had been discarded, the excess of Rhodamine B extracted into the diethyl ether was removed by shaking with 25 ml of 1 .O M hydrochloric acid. The floated ion pair was dissolved by the addition of methanol to the diethyl ether phase. The determination of phosphate was performed by measuring the fluorescence intensity of the organic phase at 573 nm with excitation at 554 nm. The calibration graph was linear up to 0.25 pg of phosphorus with a correlation coefficient of 0.999. Although arsenic(\/) caused a positive error, no ions commonly existing in natural water, including silicate, interfere with the determination of phosphate. The proposed method was applied to the determination of phosphate phosphorus in some natural water samples.
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