Scope and Limitations. The method seems to be suitable for the determination of any kinds of steroids with a dihydroxy acetone side chain a t position 17. The position and strength of the absorption band is independent of the structure and substituents of the steroid skeleton. The absorption maxima of the dimethyl quinoxaline derivatives for prednisolone, prednisone, hydrocortisone, cortisone, triamcinolone etc. were found a t 351 nm and the molar absorptivities range between 12050 and 12700. The above mentioned corticosteroids can be determined as contaminants in their 21 -acylated derivatives (acetates, trimethylacetates, p-toluene sulfonates, methane sulfonates, etc.) if their quantity is more than 0.2 %. The data of Table I1 are characteristic of these investigations. The application of the method t o 21-amino corticosteroids and pharmaceutical formulations will be published later.
17-Deoxy corticosteroids cannot be investigated by the proposed method because in this case the 20-keto-21-aldehyde side chain which is formed in the oxidation step, is instantaneously transformed t o the stable enol-aldehyde form (17/20/-ene-20-01-2l-a1) and the latter does not react with ophenylene diamine. It must be noted that triamcinolone acetonide cannot be determined also. The reason for this is supposed t o be the steric hindrance caused by the bulky acetonide group. Precision of the Method. The relative standard deviations in Tables I and I1 are characteristic of the precision of the method.
RECEIVED for review August 9, 1971. Accepted November 3, 1971. This paper is the 20th in a series on Analysis of Steroids.
Separation of Cadmium(l1) from Zinc(l1) and Other Metal Ions on a Cadmium Selective Exchanger: Titanium Selenite Mohsin Qureshi, Rajendra Kumar, and H. S. Rathore Department of Chemistry, Aligarh Muslim Unhersity, Aligarh, U. P., India THEMOST OBVIOUS advances in ion exchange in the last few years are in the area of inorganic ion exchangers ( I ) . Numerous new materials have been reported and older ion exchange materials have been studied in greater detail. Most applications of ion exchange to chemical analysis are chromatographic and ion exchange chromatography can be used to separate metal ions. Of the various metal ions, cadmium is especially important since most of the methods for determining this element depend on the complete removal of almost all other elements ( 2 ) . Several ion exchange methods for the separation of cadmium from zinc on resins in hydrochloric acid (3), aliphatic alcohols (4,dimethyl sulfoxide-aqueous hydrochloric acid ( 5 ) and in hydrobromic acid (6) media have been reported. It has been mentioned (7) that these complicated and costly solvents can be replaced by aqueous solutions containing inorganic solutes by using synthetic inorganic ion exchangers instead of organic resins. The selectivity of a n ion exchanger depends largely on its composition. Numerous ion exchangers were thoroughly studied but none of them was effective for this separation. We have therefore investigated a new ion exchanger, titanium selenite. The unique feature of this material is its high selectivity for cadmium. In this report we summarize a simple and rapid method for the separation of cadmium from zinc and from numerous metal ions by the use of a titanium selenite column. (1) H. F. Walton, ANAL.CHEM., 42, 86R (1970). (2) I. M. Kolthoff and P. J. Elving, “Treatise on Analytical Chemistry.” Vol. 3. Interscience, New York, N.Y., 1961, p 183. (3) H. G. Meyer, Z . Arid. Cliem., 24, 394 (1969). (4) F. W. E. Strelow, C. R. Vanzyl, and C. J. C. Bothma, A m / . Cliim. Acra, 45, 81 (1969). ( 5 ) I. Brize, L. W. Marple, and H. Diehl, Talama, 15, 1441 (1968). (6) J. Korkisch and E. Klakl, ibid., 16, 377 (1969). (7) G. Alberti, “Chromatography Review,” Vol. 8, Elsevier, New York, N.Y., 1966, p 246.
EXPERIMENTAL
Apparatus. All instrumentation was the same as that used in our earlier papers (8-10). Reagents. Sodium selenite (Reidel), selenious acid (BDH), and 15% wt/v titanic chloride (BDH) were used. All other chemicals were of analytical grade. Method of Preparation. Samples 2, 3, and 6 were prepared by mixing the 0.10M titanic chloride and sodium selenite solutions in the volume ratio of 1:2 at pH -1.20, 9.90, and 6.70, respectively. For sample 7, the mixing ratio was 1 : 1 ; the rest of the conditions were similar t o sample 2. Sample 1 was prepared by mixing 0.025M solutions of titanic chloride and sodium selenite in the volume ratio 1 :2 at p H -2. Sample 4 was prepared by refluxing a-titanic acid in 0.20M selenious acid for 36 hr. In order t o obtain sample 5, equal volumes of 0.2M solutions of titanic chloride and selenious acid were mixed and the product obtained was refluxed for 36 hr. Ammonia solution (d = 0.88) was used fo1 raising the pH wherever necessary. The precipitates were washed, filtered, dried, converted t o hydrogen form, sieved t o 60-120 mesh, washed again with demineralized water, and finally dried at 50 “C. The exchanger was now ready for use. The Kd values, the saturation ion-exchange capacity for K-, the pH-titration curves, X-ray, and IR studies were made as reported earlier (8, 9). For conductometric and high frequency titrations, 2 ml of 0.10M sodium selenite solutions were taken in the cell, diluted t o 100 ml with water, and titrated with 0.10M titanic chloride solution. Column Operation. For separation studies, titanium selenite (2.0 grams) .was filled in a glass column (0.68 i d . ) with glass wool support, the column was washed with de(8) M. Qureshi, H. s. Rathore, and R. Kumar, J . Cliem. Sac. ( A ) , 1970, 1986. (9) M. Qureshi, H. S. Rathore, and R. Kumar, J. Cliromatogr., 1971, 269. (10) M. Qureshi and J. P. Gupta, J . Cliem. Soc. ( A ) , 1969, 1755. ANALYTICAL CHEMISTRY, VOL. 44,
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selenium (14) content in the solution were determined spectrophotometrically. RESULTS
All seven samples are amorphous, physically stable in water as well as in dilute mineral acids. They are in the form of hard white granules suitable for column operation. The ionexchange capacity for sample 4 is 0.45 meq/gram and for the remaining samples it is 0.64-0.78 meqigram. Sample 1 turns white, white, dirty white, and light yellow and the ion-exchange capacity becomes 0.78, 0.64, 0.29, and 0.14 meq/gram on drying at 50,110,200, and 500 “C, respectively. The Ti :Se ratios for the samples are 1 :1.39, 1 : 1.35, 1 :0.20, 1 :0.20, 1:0.30, 1:1.28, and 1:1.19 for samples 1-7, respectively. The Ti: Se ratio obtained from electrometric titrations is 1 :1.66. On the basis of selenium breakdown, the order of stability of the samples is 3 > 5 > 4 > 7 > 6 >1 > 2 in water, 4M H N 0 3 , 4M HCl, and 1 M NaOH. The sequence of stability of the exchanger in all the four solutions is water > 4 M HNO:, > 4M HCl > 1 M NaOH-/.e., it is prone to hydrolysis, and water as well as dilute H N 0 3are good media for analytical studies. The quantities of titanium and selenium for sample 1 are 0.0,27.4; 625.0, 340.0; 574.0, 560.0; and 0.0, 762.5 mg’l. at 25 i 1 “C in water, 4M H N 0 3 , 4M HCl, and 1 M NaOH, respectively. The pH-titration curves of all the seven samples are similar to those reportid for zirconium phosphate (15) of varying composition. Sorption Studies. The Kd values obtained are given in Table I. The ionic radii are those tabulated by Cotton (16) and reported by Templeton et ul. (17). To show the effectiveness of titanium selenite for the separation of cadmium from numerous metal ions a plot of log Kd cs. metal ions is given in Figure 1 for various titanium based exchangers. On the basis of the Kd values, the separations
‘X--x/X
Mq2*
A134
Ca2*
Mn2’
Co2*
N12*
ZnZ*
Cd2’
METAL IONS
Figure 1. Analytical potential for Cd2- of various synthetic inorganic ion exchangers based on titaniurn(1V) 4- Titanium selenite
-x-
-e-
Titanium antimonate (19) A- Titanium tungstate (10) Titanium molybdate (12)
- .-0.- Titanium arsenate (18)
-
mineralized water, the synthetic mixture was loaded, and the column was washed again. The cations other than cadmium were eluted with 2 X 10-4A4 HNOa while cadmium was eluted with 0.40zNH4C1solution. Analytical Procedure. The exchanger was dissolved in concentrated HC1, selenium was separated by sulfur dioxide treatment and determined gravimetrically ( I ] ) , while titanium was determined volumetrically (12) in the filtrate. To measure the breakdown of the exchanger in solution, a 0.50gram portion of the exchanger was shaken in 100 ml of solution for 8 hr at 25 = 1 “C and the titanium (13) and
(11) Reference No. 1 I , p 930. (15) C. €3. Amphlett, “Inorganic Ion Exchangers,” Elsevier, New Y Irk, N.Y.. 1964, p 96. (16) F. A. Cotton and G. Wilkinsoii. “Advances in Inorganic Cliernistrq,” Interscience. Nea Yorh. N.Y.. 1964, p 45. (17) D VI. Templeton and Carol H. Dauken, J . Amer. Cl7em. SOC., 76, 5237 (1954). (18) M. Qureshi and S. A. Nabi, J . liiarg. Nucl. Chem., 32, 2059 (1970). (19) hl. Qureshi and V. KumaI, J . Ciiem. SOC.( A ) , 1970, 1488.
(11) N. Howell Furman. “Standard Methods of Chemical finalysis,” Vol. 1, 6th ed.. D. Van Nostrand, Ne\$ York, N.Y., 1962. (12) M. Qureshi and H. S. Rathore. J . Cliem. SOC.( A ) . 1969, 2515. (13) E. B. Sandell. “Colorimetric Determination of Traces of Metals.” Interscience Publishers, Inc., New York, 1959, p 873. 3
zx IO-
---i z 2
4 M- H N O ~
0.40 */e NHLCI
F
0
W I
E N 0 0
Figure 2. Separation of Zn2+from CdZT
0 IL
0
1 400
80
1082
ANALYTICAL CHEMISTRY, VOL. 44, NO. 6, MAY 1972
160
240 320 4 VOLUME OF E FFLUENl(ml.)
560
640
obtained are given in Table 11. A model plot for the elution curve of Zn2+-CdZ+is shown in Figure 2. IR Studies. The bands in IR spectra for titanium selenite samples in hydrogen form dried at 50 and 500 "C and in potassium form dried at 50 "C are similar in general. The bands obtained are characteristic of interstitial water and hydroxyl groups, interstitial water, and metal oxygen bond at 3.2, 6.2, and at about 13 1.1, respectively. However, the intensity of bands at 3.2 and 6.2 1.1 decreases as the drying temperature increases. The IR spectrum of the potassium form of the exchanger dried at 500 "C shows no band at 3.2 and 6.2 1.1.
Table I. Distribution Coefficient of Metal Ions on Titanium Selenite (Sample 1) at 25 i 1 "C Metal ion Ionic radii, A " Kd, ml/gram Mg2+
Pb2+
0.65 0.99 1.13 1.35 0.96 0.69 0.72 0.80 0.74 0.97 1.10 1.21
~ 1 3 +
0.50
Fe3+ Ga3+
0.75 0.62 0.81 1.03 0.93 1.15 0.81 1.01 1 .oo 0.96
CaZ+ Sr2+ Ba2+ cu2+
Nil+ CO2+ Mn2+ Zn2+ Cd2+ Hgz+
DISCUSSION
The method of preparation (20) of amorphous inorganic ion-exchangers has a considerable effect on their composition and the degree of hydration. These two factors are responsible for the size and shape of the cavities inside the exchanger and the chemical stability of the product. The chemical composition and the ion-exchange capacity of samples 1, 2, and 6 are somewhat similar but different from those of samples 3,4, and 5 . Sample 1 is easy to prepare, shows good ionexchange capacity and is fairly stable in water as well as in dilute mineral acids. Therefore, it has been studied in detail. The sample prepared at a higher pH (sample 3) contains more titanium than the one prepared at a lower pH (sample 1). The X-ray analysis results show the amorphous nature of the samples. IR spectra show the presence of OH groups as well as free water molecules in titanium selenite. pH-titration curves of titanium selenite exhibit a bifunctional behavior for samples 1,2, and 6 and a monofunctional behavior for samples 3, 4, 5, and 7 . Titanium(1V) oxide (21) behaves as a monofunctional base on titration with acid solution and vice-versa. (20) Sylvia J. Harvie and George H. Nancollas, J . I m r g . Nuci. Cliem., 32, 3923 (1970). (21) C. Heitner-Wirgun and A. Albu-Yaron, ibid., 28, 2379 (1966).
1n3+
Ce3+ Y3+
La3+ sc3+
Pr 3+ Nd3+ Sm3+
vo2+
uo*2+
Th4+ Zr02+
Hf02+
10 50 110 1270 130 20 20 50 60 300 30 9950 60 2230 160 1520 1100 530 1390 3 50 1600 1520 1390 140 870 140 290 470
...
... ... ...
~~~
It seems that titanium selenite is formed as a result of condensation of hydrated oxides of titanium(1V) and selenium
(W. In addition to the separations already achieved, the separation of Fe3+from A13+,Co2+,Ni2+,Mn2+,Cu*+;Mg2+from Ca2+; Ca2+ from Sr2+; Sr2+ from Ba2+; UO?+ from Th4+, V 0 2 + ; Ce3+ from Y 3 + ;La3+ from Sc3+; Cu2+ from Ni2+, Co2+and Ga3+from Zn2+and A13+ are also feasible on tita-
Table 11. Separation of Cd2+from Zn2+ and from Numerous Metal Ions on Titanium Selenite (Sample 1) Columns at 27 Volume of Sample No. Mixture separated effluent, ml Taken, gram X lo4 Found, gram X lo4 Error, 1 Zn2+ 100 0.46 0.46 0.0 Cd2+ 200 13.14 13.05 -0.7 2 ZnZT 440 5.00 5.00 0.0 Cd2+ 160 5.26 5.35 +1.7 3 Zn2+ 500 9.09 9.15 $0.6 Cd2+ 80 1.31 1.36 +3.8 4 5
6 7 8
Zn2+ Cd2+ Zn2+
Cd2+ Nil+ CdZ+ co2+ Cd2+ Mn2+ Cd2+
9
Ca2+ Cd2+
10
Mg2+ Cd2+
11
~ 1 3 +
Cd2+
380 80 760 80 240 160 500 160 400 160
4.55 1.31 22.73 0.66 4.04 5.26 4.50 5.26 4.12 5.26
4.55 1.27 22.85 0.68 4.04 5.35 4.55 5.35 4.17 5.26
200 160 80 160
2.19 5.26 2.39 5.26
2.13 5.35 2.39 5.16
600 160
2.02 5.26
1.99 5.26
=t1
"C
0.0
-3.1 +0.5 +3.0 0.0 +1.7 +1.1 +1.7 +1.2 0.0
-2.7 +1.7 0.0
-1.9 -1.5 0.0
ANALYTICAL CHEMISTRY, VOL. 44, NO. 6, M A Y 1972
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nium selenite columns (Table I). Titanium selenite is more selective for the separation of cadmium from numerous metals than other exchangers based on titanium (Figure 2). This is the obvious advantage of the synthesis. pH-titration curves for Li, Na, and K of sample 1 show that titanium selenite is also selective for alkali metals. The order of adsorption is K > Na > Li, Li > Na > K and Li = Na > K at pH values 3, 8, and 12, respectively. On stannic arsenate this preference is reversed. Ion-exchange capacity data at different temperatures show that it is a good exchanger and it can be used up to 500 “C successfully. IR spectra are also in support of the above conclusion. In order to explain the effectiveness of titanium selenite for the separation of cadmium from numerous metal ions, a thorough search of the literature (22) was made. It was found that the selenite of Mg, Ca, Ni, Co, Mn, Zn, and AI have been prepared by mixing the carbonate of the respective metal ions (22) J. W. Mellor, “A Comprehensive Treatise on Inorganic and Theoretica 1 Chemistry,” Vol. X, Longmans Green & Co., London, 1961, p 829.
with selenious acid. Except cadmium selenite, all are soluble in water as well as in dilute mineral acids. Therefore, cadmium should be adsorbed more strongly than the remaining cations under study. Hence elution of Mg, Ca, Ni, Co, Mn, Zn, and AI has been made with 2 X 10-4M H N 0 3 while elution of cadmium has been obtained with aqueous 0.40% NH4Cl solution at a low pH value and at a higher ionic strength. The elution of cadmium is sharper than that of the other metal ions. This may be due to the formation of a complex anion (23) (CdCI4*-)with ammonium chloride. ACKNOWLEDGMENT
We thank S.M.F. Rahman, B. Rama Rao (R.R. Lab., Hyderabad), M.V. George (I.I.T., Kanpur) for research, X-ray and IR facilities. RECEIVED for review August 4, 1971. Accepted November 9, 1971. One of us (R.K.) thanks the U.G.C. (India) for financial assistance. (23) Reference No. 15, p 606.
Simple Method for Routine Detection of Residues of Diethylstilbestrol (DES) in Meat Contaminated at Levels as Low as One Part per Billion Walter G. Smith1 and Edward E. McNeil Animal Pathology Dicision, Health of Animals Branch, Canadian Department o j Agriculture, Animal Diseases Research Institute, Hull, Quebec, Canada DIETHYLSTILBESTROL (DES) may be administered to livestock animals as a growth promoting agent by surgical implantation in pellet form or as an additive in their rations. The detection of residues of DES in animals so treated is difficult. A utilizable, chemical assay must satisfy a number of criteria. It must be suitable for regular and routine use by relatively unskilled personnel. It must permit handling large numbers of specimens in a short space of time for use as a surveillance tool. It must be selective for DES and avoid the simultaneous estimation of natural estrogens. It must unequivocally detect a quantity of DES equivalent to a contamination level in the specimen as low as 1 part per billion. It must permit simultaneous estimation of “free DES” and either “combined DES” (sulfate or glucuronide conjugates) or “total DES”Le., “free DES” together with “combined DES.” Published methods (1-9) satisfy some of these criteria but 1 Present address, Pharmacology Division, Research Laboratories, Food and Drug Directorate, Tunney’s Pasture, Ottawa
(1) “British Pharmacopoeia,” 1968, p 938. (2) “Pharmacopoeia of the United States,” XVI, p 217. (3) “Official Methods of Analysis of the Association of Official Agricultural Chemists,” 10th ed., 1965, Section 32.196 and Section 33.039. (4) R. L. Dryer, Clin. Clzem., 2, 25 (1956). (5) J. M. Goodyear and N. R. Jenkinson, ANAL.CHEM.,33, 853 (1961). 1084
ANALYTICAL CHEMISTRY, VOL. 44, NO. 6, MAY 1972
none satisfies all. The present communication outlines a new method which in our hands has proved to be rapid, easy to execute, and selective for DES. The present text is restricted to a full description of the method and sufficient discussion to permit its routine use by others with minimum difficulty. The method consists of extraction utilizing acetonitrile :water (9 :l); removal of contaminating lipid from the extracted DES with the aid of immiscible solvent systems; and detection of the extracted DES by electron capture gas chromatography. It seems to us that the detection of nanogram quantities of DES utilizing gas chromatography with an electron capture detector is dependent upon the formation of a derivative of DES on the column (10). This aspect is under further investigation. EXPERIMENTAL
Reagents. Ethanol was redistilled in an all-glass apparatus from CaC12 and NaOH. All other reagents used were of (6) E. J. Umberger, D. Banes, F. M. Kunze, and S . H. Colson, J. Ass. Ofjic. Agr. Cliem., 46, 471 (1963). (7) I. E. Smiley and E. D. Schall, J . Ass. Ofic. Ann/. Ckem., 52, 107 (1969). (8) D. L. Simmons, R. J. Ranz, and R. C. Cornell, Cm. J. Pliarm. Sci., 6 , 28 (1971). (9) B. S. Rutherford, J . Ass. Ofic.Ami. Cliem., 53, 1243 (1970). (10) P. Saschenbreker, Animal Pathology Laboratory. Canada Department of Agriculture, Guelph. Ontario, personal communication, January 1971.
