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A rapid method of microgram analysis of titanium from rocks
Chemical Geology, 30 (1980) 167--170
167
Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
Short Communication A RAPID METHOD OF MICROGRAM A N A L Y S I S OF TITANIUM FROM ROCKS
Y.K. AGRAWAL 1, M.P. PATEL 2, S.J. DESAI 2, and S.S. MERH 2
Analytical Laboratories, Pharmacy Department, Faculty of Technology and Engineering, M.S. University o f Baroda, Kalabhavan, Baroda 390 001 (India) 2Faculty of Science, M.S. University of Baroda, Baroda 390 002 (India) (Received June 2, 1979; revised and accepted April 16, 1980)
ABSTRACT Agrawal, Y.K., Patel, M.P., Desai, S.J. and Merh, S.S., 1980. A rapid method of microgram analysis of titanium from rocks. Chem. Geol., 30: 167--170. A new spectrophotometric method for the microgram determination of Ti from rock samples in the presence of commonly occurring metal ions has been developed. Ti is extracted from a 1-hexanol solution of benzohydroxamic acid (BHA) at pH < 2. The yellow extract has the maximum absorbance at 370 nm. The extraction was quantitative and obeys Beer's law at 370 nm over the range of 5--20 ppm Ti and the molar absorptivity is 2.4.103 I mo1-1 cm -1. INTRODUCTION
Titanium, as a trace element in waters, geological materials, plants and animals, has been extensively studied for the last five decades. The average abundance of Ti in geological materials, igneous rocks, is about 64 mg/kg (Brooks, 1972). Ti is also a valuable pathfinder element in geobotany and biogeochemistry studies in mineral exploration (Hutchinson, 1943; Cannon, 1960; Brooks, 1972). Various methods are available for the chemical determination of Ti in the chemical form (Sandell, 1959; Vogel, 1968; Agrawal, 1975). In the present investigation, a spectrophotometric method has been described for the quantitative determination of Ti in geological samples. EXPERIMENTAL
Reagents and solutions The benzohydroxamic acid (BHA) was synthesised by the method of Shukla et al. (1974). It was recrystallized before use and its purity was ascertained by m.p., elemental analysis, UV and IR spectra. Generally, a 0.1 M solution of benzohydroxamic acid was prepared in distilled water. 0009-2541/0000--0000/$ 02.25 © 1980 Elsevier Scientific Publishing Company
168 A standard Ti solution was prepared by heating 0.1668 g of pure titanium dioxide in a Pyrex ® flask with 8 g of a m m o n i u m sulphate and 25 ml of concentrated H2SO4. After cooling, the resulting solution was transferred into a 500-ml volumetric flask containing 350 ml o f water. The Pyrex ® flask was washed with 5% H:SO4 and finally diluted to the mark. A further 20 ml of this solution was diluted to 100 ml with 5% H2SO4. The strength of this solution in terms o f Ti was 1 . 0 4 1 . 1 0 -3 M. The solutions o f rock samples were prepared as " B " solutions by the Shapiro and Brannock (1962) method. The absorption spectra of Ti complexes were recorded on a VSU-2P ® s p e c t r o p h o t o m e t e r , using 10-mm cells. Procedure Calibration curve. Into a 100-ml separatory funnel, an aliquot of Ti solution (5 ml or 1 . 0 4 1 . 1 0 -3 M), 8 ml of concent r a t e d HC1 and 10 ml of BHA were added. Then 10 ml of 1-hexanol was added and the contents were shaken vigorously for 5 min. The hexanol layer was separated, dried over anhydrous sodium sulphate, and finally the extracts were diluted to 25 ml with hexanol. The absorbance o f the extracts was measured at 370 nm against 1-hexanol as a reagent blank. Finally, a graph was pl ot t e d between absorption and concentration o f Ti (5--20 ppm). Extraction and determination
of titanium from rocks
10 ml o f the rock-sample solution was transferred into a 100-ml separatory funnel, along with 25 ml of distilled water (10 mg of ascorbic acid), 20 ml o f c o n cen tr ated HC1 and 10 ml of b e n z o h y d r o x a m i c acid solution. 10 ml o f 1-hexanol was added find the cont ent s were shaken vigorously for 5 min. The hexanol layer was separated, dried over anhydrous sodium sulphate to remove the moisture and transferred into 1 25-ml volumetric flask. To ensure the complete recovery of Ti, the aqueous phase was extracted with 5 ml of reagent solution and 2 ml of hexanol. The sodium sulphate was washed with 2 ml o f hexanol to remove the last traces of yellow colour. Finally, the extract was diluted t o 25 ml. The absorbance of yellow colour was measured at 370 nm against the reagent blank and the concent rat i on was c o m p u t e d from the calibration curve. RESULTS AND DISCUSSION The absorbance spectra of the Ti-BHA complex has a m a x i m u m absorbance at 370 nm (Agrawal, 1975). The reagent does n o t absorb at this wavelength. The data on the effect o f pH for the determination of Ti are given in Table I and the co n cen tr at i on o f Ti in r oc k samples in Table II. The plot o f the absorbance at 370 nm against the c o n c e n t r a t i o n os Ti gives
169 TABLE I Extraction of Ti(IV}-benzohydroxamic acid complex as a function of pH pH
Extraction, E (%)
1.0 1.5 2.0 2.5
100 100 100 95
Distribution ratio, D oo
~o oo 19.0
pH
Extraction, E (%)
Distribution ratio, D
3.0 4.0 4.5 5.0
80 50 30 15
17.0 11.0 6.0 2.5
TABLE II Concentration of titanium (ppm) in rock samples No.
Rock type
Ti
No.
Rock type
Ti
1 2 3 4 5 6
basic charnockite norite ultrabasic charnockite acid charnockite ultra basic charnockite intermediate charnockite
165 180 165 190 200 195
7 8 9
spilitic basalt spilitic diabase keratophyre keratophyre soda granite soda granite
170 180 190 175 190 180
10
11 12
a straight line, which passes through the origin. Fig. 1 represents this plot which obeys Beer's law over a range of 5--20 ppm Ti. This method is quite rapid and sensitive and gives reproducible results. Ti could be determined from any type of the rock samples in the presence of V, Be, Fe, Cu, Ni, Co, As, Mo, rare earths and other common metal ions. Another advantage of this method is that the same "B" solutions, which have 1.25
1.00
c 0.7!
o .fl
.~ 0.75 0.2E
;
,; ,;
1o
Titanium. ppm
Fig. 1. Calibration curve for titanium.
170
been prepared earlier for the analysis of major elements, can also be used for Ti. Further, this m e t h o d is more sensitive as compared to the atomic absorption spectrophotometric method where the sensitivity for Ti is 12.0 ppm.
REFERENCES Agrawal, Y.K., 1975. Solvent extraction and spectrophotometric determination of titanium(IV) with benzohydroxamic acid. Chem. Era, 11 : 21. Brooks, R.R., 1972. Geobotany and Biogeochemistry in Mineral Exploration. Harper and Row, New York, N.Y. Cannon, H.L., 1960. Botanical prospecting for ore deposits. Science, 132: 591--598. Hutchinson, G.E., 1943. The biogeochemistry of aluminium and of certain related elements. Q. Rev. Biol., 18: 1--29; 129--153; 242--262; and 331--363. Sandell, E.B., 1959. Colorimetric Determination of Traces of Metals. Interscience, New York, N.Y., pp. 868--881. Shapiro, L. and Brannock, W.W., 1962. Rapid analyses of silicate, carbonate and phosphate rocks. U.S. Geol. Surv., Bull., 1144-A: 45. Shukla, J.P., Agrawal, Y.K. and Kuchya, K.P., 1974. Preparation and properties of some p-substituted benzohydroxamic acids. J. Indian Chem. Soc., 51: 437. Vogel, A.I., 1968. A Text Book of Quantitative Inorganic Analysis. Longmans, London, 3rd ed., p. 788.
167
Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
Short Communication A RAPID METHOD OF MICROGRAM A N A L Y S I S OF TITANIUM FROM ROCKS
Y.K. AGRAWAL 1, M.P. PATEL 2, S.J. DESAI 2, and S.S. MERH 2
Analytical Laboratories, Pharmacy Department, Faculty of Technology and Engineering, M.S. University o f Baroda, Kalabhavan, Baroda 390 001 (India) 2Faculty of Science, M.S. University of Baroda, Baroda 390 002 (India) (Received June 2, 1979; revised and accepted April 16, 1980)
ABSTRACT Agrawal, Y.K., Patel, M.P., Desai, S.J. and Merh, S.S., 1980. A rapid method of microgram analysis of titanium from rocks. Chem. Geol., 30: 167--170. A new spectrophotometric method for the microgram determination of Ti from rock samples in the presence of commonly occurring metal ions has been developed. Ti is extracted from a 1-hexanol solution of benzohydroxamic acid (BHA) at pH < 2. The yellow extract has the maximum absorbance at 370 nm. The extraction was quantitative and obeys Beer's law at 370 nm over the range of 5--20 ppm Ti and the molar absorptivity is 2.4.103 I mo1-1 cm -1. INTRODUCTION
Titanium, as a trace element in waters, geological materials, plants and animals, has been extensively studied for the last five decades. The average abundance of Ti in geological materials, igneous rocks, is about 64 mg/kg (Brooks, 1972). Ti is also a valuable pathfinder element in geobotany and biogeochemistry studies in mineral exploration (Hutchinson, 1943; Cannon, 1960; Brooks, 1972). Various methods are available for the chemical determination of Ti in the chemical form (Sandell, 1959; Vogel, 1968; Agrawal, 1975). In the present investigation, a spectrophotometric method has been described for the quantitative determination of Ti in geological samples. EXPERIMENTAL
Reagents and solutions The benzohydroxamic acid (BHA) was synthesised by the method of Shukla et al. (1974). It was recrystallized before use and its purity was ascertained by m.p., elemental analysis, UV and IR spectra. Generally, a 0.1 M solution of benzohydroxamic acid was prepared in distilled water. 0009-2541/0000--0000/$ 02.25 © 1980 Elsevier Scientific Publishing Company
168 A standard Ti solution was prepared by heating 0.1668 g of pure titanium dioxide in a Pyrex ® flask with 8 g of a m m o n i u m sulphate and 25 ml of concentrated H2SO4. After cooling, the resulting solution was transferred into a 500-ml volumetric flask containing 350 ml o f water. The Pyrex ® flask was washed with 5% H:SO4 and finally diluted to the mark. A further 20 ml of this solution was diluted to 100 ml with 5% H2SO4. The strength of this solution in terms o f Ti was 1 . 0 4 1 . 1 0 -3 M. The solutions o f rock samples were prepared as " B " solutions by the Shapiro and Brannock (1962) method. The absorption spectra of Ti complexes were recorded on a VSU-2P ® s p e c t r o p h o t o m e t e r , using 10-mm cells. Procedure Calibration curve. Into a 100-ml separatory funnel, an aliquot of Ti solution (5 ml or 1 . 0 4 1 . 1 0 -3 M), 8 ml of concent r a t e d HC1 and 10 ml of BHA were added. Then 10 ml of 1-hexanol was added and the contents were shaken vigorously for 5 min. The hexanol layer was separated, dried over anhydrous sodium sulphate, and finally the extracts were diluted to 25 ml with hexanol. The absorbance o f the extracts was measured at 370 nm against 1-hexanol as a reagent blank. Finally, a graph was pl ot t e d between absorption and concentration o f Ti (5--20 ppm). Extraction and determination
of titanium from rocks
10 ml o f the rock-sample solution was transferred into a 100-ml separatory funnel, along with 25 ml of distilled water (10 mg of ascorbic acid), 20 ml o f c o n cen tr ated HC1 and 10 ml of b e n z o h y d r o x a m i c acid solution. 10 ml o f 1-hexanol was added find the cont ent s were shaken vigorously for 5 min. The hexanol layer was separated, dried over anhydrous sodium sulphate to remove the moisture and transferred into 1 25-ml volumetric flask. To ensure the complete recovery of Ti, the aqueous phase was extracted with 5 ml of reagent solution and 2 ml of hexanol. The sodium sulphate was washed with 2 ml o f hexanol to remove the last traces of yellow colour. Finally, the extract was diluted t o 25 ml. The absorbance of yellow colour was measured at 370 nm against the reagent blank and the concent rat i on was c o m p u t e d from the calibration curve. RESULTS AND DISCUSSION The absorbance spectra of the Ti-BHA complex has a m a x i m u m absorbance at 370 nm (Agrawal, 1975). The reagent does n o t absorb at this wavelength. The data on the effect o f pH for the determination of Ti are given in Table I and the co n cen tr at i on o f Ti in r oc k samples in Table II. The plot o f the absorbance at 370 nm against the c o n c e n t r a t i o n os Ti gives
169 TABLE I Extraction of Ti(IV}-benzohydroxamic acid complex as a function of pH pH
Extraction, E (%)
1.0 1.5 2.0 2.5
100 100 100 95
Distribution ratio, D oo
~o oo 19.0
pH
Extraction, E (%)
Distribution ratio, D
3.0 4.0 4.5 5.0
80 50 30 15
17.0 11.0 6.0 2.5
TABLE II Concentration of titanium (ppm) in rock samples No.
Rock type
Ti
No.
Rock type
Ti
1 2 3 4 5 6
basic charnockite norite ultrabasic charnockite acid charnockite ultra basic charnockite intermediate charnockite
165 180 165 190 200 195
7 8 9
spilitic basalt spilitic diabase keratophyre keratophyre soda granite soda granite
170 180 190 175 190 180
10
11 12
a straight line, which passes through the origin. Fig. 1 represents this plot which obeys Beer's law over a range of 5--20 ppm Ti. This method is quite rapid and sensitive and gives reproducible results. Ti could be determined from any type of the rock samples in the presence of V, Be, Fe, Cu, Ni, Co, As, Mo, rare earths and other common metal ions. Another advantage of this method is that the same "B" solutions, which have 1.25
1.00
c 0.7!
o .fl
.~ 0.75 0.2E
;
,; ,;
1o
Titanium. ppm
Fig. 1. Calibration curve for titanium.
170
been prepared earlier for the analysis of major elements, can also be used for Ti. Further, this m e t h o d is more sensitive as compared to the atomic absorption spectrophotometric method where the sensitivity for Ti is 12.0 ppm.
REFERENCES Agrawal, Y.K., 1975. Solvent extraction and spectrophotometric determination of titanium(IV) with benzohydroxamic acid. Chem. Era, 11 : 21. Brooks, R.R., 1972. Geobotany and Biogeochemistry in Mineral Exploration. Harper and Row, New York, N.Y. Cannon, H.L., 1960. Botanical prospecting for ore deposits. Science, 132: 591--598. Hutchinson, G.E., 1943. The biogeochemistry of aluminium and of certain related elements. Q. Rev. Biol., 18: 1--29; 129--153; 242--262; and 331--363. Sandell, E.B., 1959. Colorimetric Determination of Traces of Metals. Interscience, New York, N.Y., pp. 868--881. Shapiro, L. and Brannock, W.W., 1962. Rapid analyses of silicate, carbonate and phosphate rocks. U.S. Geol. Surv., Bull., 1144-A: 45. Shukla, J.P., Agrawal, Y.K. and Kuchya, K.P., 1974. Preparation and properties of some p-substituted benzohydroxamic acids. J. Indian Chem. Soc., 51: 437. Vogel, A.I., 1968. A Text Book of Quantitative Inorganic Analysis. Longmans, London, 3rd ed., p. 788.