Sorption-Photometric Determination of Trace Titanium, Copper, and Iron from a Single Sample in Some Materials Used in Phosphor Production
Abstract Generated abstract
A sorption-photometric procedure is described for determining trace titanium, copper, and iron from a single weighed sample of phosphor L-34 and related production materials, including calcium carbonate and calcium hydrogen phosphate. Samples are decomposed in concentrated purified hydrochloric acid, iron is separated and concentrated on ceralite FF, while titanium and copper chloride complexes are retained on AN-2F, followed by elution with dilute hydrochloric acid and photometric determination using 2,2′-dipyridyl, sodium diethyldithiocarbamate, and diantipyrylmethane. Tests on artificial mixtures and parallel analyses of production materials indicate applicability at sensitivities of 10^-5 to 10^-6 percent, with an analysis time of about 1.5 to 2 hours and relative errors of approximately 10 to 15 percent.
Full Text
SORPTION–PHOTOMETRIC DETERMINATION OF TRACES OF TITANIUM, COPPER, AND IRON FROM A SINGLE SAMPLE IN CERTAIN MATERIALS USED IN PHOSPHOR PRODUCTION
R. D. Glukhovskaya, Yu. L. Lel’chuk, E. D. Lukker
(Presented by the scientific seminar of the Department of Analytical Chemistry)
This collection publishes the results of a study of the sorption and desorption of titanium from hydrochloric-acid solutions on the anion exchangers AN-2F and ceralite FF. These data enabled us, in combination with the previously [1] proposed method for determining copper and iron, to develop a method for determining traces of titanium, copper, and iron from a single sample of phosphor L-34 and of materials used for its production.
The method is based on decomposition of a weighed portion of the substance being analyzed in 9–10 N specially purified HCl; separation and concentration of the chloride complex of iron by the anion exchanger ceralite FF, and of the chloride complexes of titanium and copper by the anion exchanger AN-2F in the chloride form; their elution with 0.1 N HCl; and photometric determination of iron with 2,2′-dipyridyl, copper with sodium diethyldithiocarbamate, and titanium with diantipyrylmethane.
The size of the weighed portion depends on the expected content of microimpurities of these elements. In our experiments it ranged from 1 to 5 g. The duration of the analysis is 1.5–2 h. The sensitivity is \(10^{-5}\)—\(10^{-6}\%\). The relative error is \(\pm 10\)—15%.
Purification of hydrochloric acid, preparation of anion-exchange columns, preparation of iron, copper, and titanium solutions, and the final photometric determinations of traces of these elements have been described by us previously [1–4].
Procedure. A weighed portion of the substance being analyzed is dissolved in 9 N specially purified HCl. Separation and concentration of iron are carried out on a small chromatographic column of ceralite FF with a bed height of 2 cm [4], and of copper and titanium on a column of the anion exchanger AN-2F with a bed height of 22 cm [2, 3]. Both columns are mounted on one stand so that the solution flowing from the ceralite column enters the AN-2F column. The flow rate is 2–3 ml/min.
The columns are successively treated with 10–15 ml of specially purified 9–10 N HCl, then the hydrochloric-acid solution of the substance being analyzed is passed through, and the columns are washed with 20–30 ml of hydrochloric acid of the same concentration. After this the column with ceralite is mounted on another stand, and the sorbed iron is eluted with 10 ml of 0.1 N HCl. The eluate is collected in a 25-ml volumetric flask, and iron is determined photometrically in it as the complex with 2,2′-dipyridyl by the procedure described earlier [3].
The column with AN-2F is washed with another 10–12 ml of 9–10 N HCl, and then the sorbed chloride complexes of titanium and copper are washed out with 0.1 N HCl. The first portions of this acid are used to move the tita-
of titanium and copper down the chromatographic column, and these elements are not contained in the effluent solution. These portions are discarded. As the eluate moves through the column, the color of the anion exchanger changes from dark brown to yellow. When a dark layer of anion exchanger 4–5 cm high remains at the bottom of the column, the stopcock is closed, the column is washed with high-purity water, and the eluate is then collected in a 25 ml volumetric flask to the mark. The contents of the flask are thoroughly mixed, and aliquot portions are taken for the determination of copper in one portion and titanium in the other.
Copper is determined by the previously described method [1], in the form of the yellow complex with sodium diethyldithiocarbamate. To determine titanium, an aliquot of the eluate is transferred to a 25 ml volumetric flask; 1 ml of a 7% ascorbic acid solution, 2 drops of a 5% copper sulfate solution, and 5 ml of a 5% diantipyrylmethane solution are added; the volume is brought to the mark with 5 N HCl, mixed, and after 30–40 min the optical density is measured on an FEKN-57 photoelectric colorimeter-nephelometer in cuvettes with a 5 cm layer thickness, using a blue light filter with maximum transmittance at 413 mμ. Water serves as the comparison solution. A blank experiment is set up simultaneously, and its optical density is subtracted.
The percentage content of titanium in the substance analyzed is calculated by the formula:
\[ \mathrm{Ti}=\frac{B \cdot V}{10000\,H\,V_a}\%, \]
where
\(B\) is the weight of titanium in the aliquot, μg,
\(V\) is the volume of the volumetric flask, ml,
\(H\) is the weighed portion of the substance analyzed, g,
\(V_a\) is the volume of the aliquot, ml.
The accuracy and reproducibility of the method were checked on artificially prepared mixtures and by parallel determinations of traces of titanium, copper, and iron in phosphor L-34, in factory preparations of calcium carbonate and calcium hydrophosphate. Some of the data obtained are given in Tables 1 and 2.
Table 1
Verification of the accuracy of the method on artificially prepared mixtures
| Number of determinations | Taken, μg | Taken, μg | Taken, μg | Found, μg | Found, μg | Found, μg | Relative error, % | Relative error, % | Relative error, % |
|---|---|---|---|---|---|---|---|---|---|
| Ti | Cu | Fe | Ti | Cu | Fe | Ti | Cu | Fe | |
| 3 | 5.17 | 5.43 | 5.54 | 5.26 | 6.10 | 5.56 | +1.7 | +12.3 | +0.36 |
| 2 | 5.17 | 10.86 | 5.54 | 5.25 | 9.86 | 4.86 | +1.5 | −9.2 | −12.2 |
| 2 | 10.34 | 5.43 | 5.54 | 11.28 | 5.75 | 5.12 | +9.1 | +5.9 | −7.6 |
Table 2
Results of parallel determinations of titanium, copper, and iron in phosphor L-34, calcium carbonate, and calcium hydrophosphate
| Substance analyzed | Number of determinations | Found, % | Found, % | Found, % | Max. deviations from the mean value, % | Max. deviations from the mean value, % | Max. deviations from the mean value, % |
|---|---|---|---|---|---|---|---|
| Ti | Cu | Fe | Ti | Cu | Fe | ||
| CaCO₃ | 3 | \(1.07 \cdot 10^{-4}\) | \(4.8 \cdot 10^{-5}\) | \(2 \cdot 10^{-4}\) | ±9.3 | ±12.2 | ±3.4 |
| CaHPO₄ | 3 | \(1.22 \cdot 10^{-4}\) | \(4.75 \cdot 10^{-5}\) | \(3.7 \cdot 10^{-4}\) | ±10.6 | ±5.2 | ±5.9 |
| Phosphor L-34 | 2 | \(1.09 \cdot 10^{-4}\) | \(2.8 \cdot 10^{-4}\) | \(2.2 \cdot 10^{-3}\) | ±6.4 | ±6.9 | ±9.1 |
Conclusions
A sorption–photometric method has been developed for determining trace amounts of titanium, copper, and iron from a single weighed sample in phosphor L-34, calcium carbonate, calcium hydrogen phosphate, and hydrochloric acid used for the production of this phosphor.
Separation and concentration of microimpurities of these elements are carried out in the form of chloride complex anions using anion exchangers: iron with ceralite FF, and copper and titanium with AN-2F. Iron is determined photometrically as the complex with 2,2′-dipyridyl, copper with sodium diethyldithiocarbamate, and titanium with diantipyrylmethane.
The duration of the analysis is 1.5–2 hours; the sensitivity is \(10^{-5}\)—\(10^{-6}\%\), and the relative error is \(\pm 10\)—\(15\%\).
References
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Yu. L. Lel’chuk, R. D. Glukhovskaya, E. D. Lukker, G. N. Dembovskaya. Izv. TPI, vol. 174, 68 (1968).
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R. D. Glukhovskaya, Yu. L. Lel’chuk. Proceedings of the Scientific and Technical Conference of the Tomsk Branch of the All-Union Chemical Society named after D. I. Mendeleev, 54, 1968.
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R. D. Glukhovskaya, Yu. L. Lel’chuk. Abstracts of Reports of the All-Union Conference on Analytical Chemistry of Semiconductor Substances. 19, 46, Kishinev, 1965.
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R. D. Glukhovskaya, Yu. L. Lel’chuk, E. D. Lukker. This collection, pp. 23, 26.