667
Anal. Chem. 1986, 58,667-668
dition of the acid scavenger greater than the 500 ppm added increment is unnecessary for the reduction in HC1 emissions achieved. Registry No. HCl, 7647-01-0; chloride, 16887-00-6; polypropylene (homopolymer), 9003-07-0.
LITERATURE CITED (1) BASF Aktiengeseiischaft, United Kingdom Patent 1439 948, 1976. (2) Bora, J. S.Corros. Sci. 1979, 14,503-506. (3) Shigeo Miyata, Takamatsu; Masataka, Kagawa United States Patent 4 284 762, 1976. (4) Shigeo Mlyata, Takamatsu; Masataka, Kagawa United States Patent 4 347 353, 1982.
(5) Schroeder, Waiter C.; Webster, Joseph R. United Kingdom Patent 1514903, 1978. (6) Lin, Chi-Hung United States Patent 4420609, 1983. (7) Hecht, James L.; Garrison, Wiiiiam E. Polyrn-Plast. Techno/. Eng. 1982, 18 (l),109-122. (8) NORCHEM, Inc., Morris, IL, Method Number 9107.2,1983. (9) Haslam, J.; Willis, H. A,; Squirell, D.C. M. "Identification and Analysis of Plastics", 2nd ed.; Iiiffe Books: London, 1972;Chapter 6.
RECEIVEDfor review June 26,1985. Accepted October 7,1985. The author wishes to express his appreciation and thanks to the management a t NORCHEM's Technical Center, Morris, IL, for permitting publication of this work.
Separation of Tracer Titanium-44 from Vanadium Munawwar Sajjad' and Richard M. Lambrecht*'
Department of Chemistry, Brookhaven National Laboratory, Upton, N e w York 11973 The trend in medical radionuclide and radiopharmaceutical research and development is toward the use of short-lived neutron-deficient nuclides. Biomedical generators ( I ) that deliver positron-emitting nuclides will be an important source (t1/2= 4 years), of these nuclides. The 4d/ri/"Sc generator ["i 44Sc (tlIz = 3.93 h)] has been suggested previously (2-4). Furthermore, w7Sc has been suggested as a potential scanning agent for tumor and bene marrow (5) and for metabolism studies (6, 7). Syed and Hosain (8) proposed %c for studying bone diseases by positron emission tomography. Titanium-44 produced by the 45S~(p,2n)44Ti reaction is commercially available only in very limited quantities. We have found that 44Ti can also be produced by the 51V(p,2p6n)44Tinuclear reaction by irradiating a vanadium target with high-energy protons. A new separation method was required in order to recover 44Tiwithout added carrier. Kanza-Kanza et al. (9) reported a procedure for the simultaneous separation of carrier-free 4sCr, 45Ti,and 44Scisotopes from cyclotron-irradiated Vz05, but the recovery yield of T i was not indicated. Nelson et al. (13)have shown that vanadium can be separated from titanium if both are in the plus four valence state. We have developed a new method for the separation of titanium from vanadium.
EXPERIMENTAL SECTION Two vanadium disks (305 mg/cm2) of 99.7% purity were irradiated at the BNL Linac Isotope production facility with 50100-yA beams of 200-MeV protons to a fluence of 7775 and 5273 yAh, respectively. A sample assayed after 1 year indicated 46Sc, 44Ti,22Na,7Be,54Mn,and were present. 44Ti/44S~ were the main isotopes present after a 10-year cooling period as shown in Figure 1. The activity is mainly due to 4Ti/"Sc, but 22Naand @Coare also present. Gamma spectrometry was obtained by using a 45-cm3Ge(Li) detector (full width at half-maximum of 1.87 keV at 1.33-MeV photopeak of 6oCo,peak-to-compton ratio of 32:1, and an efficiency of 7.7%) in conjunction with a Canberra Series 90 pulse-height analyzer. Titanium and vanadium in the final separated samples from the nonradioactive work were analyzed by X-ray fluorescencespectrometry. Neutron activation analysis (NAA) was used for the 44Tisamples. RESULTS AND DISCUSSION The method was developed by use of nonradioactive vanadium and titanium metal. Typically, 50 mg of V and 5-13 mg of T i were dissolved in aqua regia. The solution was Present address: Radionuclide and Cyclotron Operations, King Faisal Specialist Hospital and Research Centre, Box 3354, Riyadh 11211, Kingdom of Saudi Arabia.
evaporated to dryness. Vanadium was converted to Vz05 and titanium to TiOz. I t is important to use HCl-HF media for the separation, Titanium dissolves in hot HCl but tends to precipitate even in concentrated acid. The best solvent is H F or acids to which fluoride ions have been added. Such a media dissolves titanium and holds it in solution as the fluoro complex. Four milliliters of 2 M H F and 1 mL of concentrated HC1 were added to the dried Vz05and Ti02. Ti(1V) forms Hydroxylamine hya strong complex with F-, Le., TiF:-. drogen chloride was used to reduce V(V) to V(1V). The following standard potentials have been reported ( 2 1 , 12)
VOz+ + 2H+ + e = V02+ + H20 Eo = 1.0 V (1) Ti02+(aq)
+ 2H+ + e = Ti3+ + H 2 0
Eo = 0.1 V
(2)
The standard potential of V(V) - V(1V) is higher than the Ti(1V) - Ti(II1) standard potential; therefore V(V) will be reduced to V(1V) before Ti(1V) will be reduced to Ti(II1). As Ti is bound as TiFs2-, it will be more difficult to reduce titanium. The exact weight of the vanadium target was known. Therefore the number of moles of NH20H-HC1needed to reduce V(V) to V(1V) was calculated by using a 1:l proportion. The weighed NH20H.HC1was dissolved in water. A solution of NH20H.HC1 was added slowly while stirring. Insoluble Vz05 will start dissolving as V(V) is reduced to V(1V) forming the blue [VO(H20)5]2+ ion. The solution was heated to boiling for 10 min after the addition of NH20H-HC1. The solution was cooled and diluted to the final acid concentration of 0.1 M HCl-1 M HF. The solution was passed through a Dowex 1X-2 (50-100 mesh) anion-exchange column (1X 10 cm). The column was prewashed with 0.1 M HC1-1 M HF. After the dissolved target solution was eluted, the column was washed with 0.1 M HCl-1 M H F till the column was visually free of the blue vanadium solution. [VO(HzO)5]2+ was passed through the column, whereas TiF:was retained on the column. Titanium was eluted with 6 M HC1-1 M HF. The solution was evaporated to dryness, and titanium was taken up in dilute HC1 for analysis. The samples were analyzed by X-ray fluorescence spectrometry. The titanium recovery was 97 2%, and the vanadium contamination was 0.02%. The vanadium concentration can be further reduced by repeating the procedure. Separation of 44Tifrom Irradiated Vanadium Target. Figure 2 depicts a flow diagram of the radiochemical scheme used for the separation of 44Ti. Nine grams of irradiated vanadium metal was reacted with aqua regia. Thirty milliliters of concentrated H F and 8 mL of concentrated HCl were added
0003-2700/86/0358-0667$01.50/00 1986 American Chemical Society
*
688
ANALYTICAL CHEMISTRY, VOL. 58, NO. 3, MARCH 1986
2048
1024 CHANNEL NUMBER
?-Ray spectrum of the irradiated vanadium target after a 10-year cooling period.
Figure 1.
&id aqua r e g i a . After tbe metal has reacted, evaporate to dryness
Add
Hp
+ EC1 + 820
+ N8208'HCl
SOLUTION, COOL
I I
0.1 M E l - 1 H Bp
I I
DILDTEITrnTKE FINAL ACID CXJNCE"FATI0N 0.1 n Bci-i n H p
I
+5 I
6 H E l - 1 W EX
PASS I T TEXOUGE ANION EXCHANGE RESIN
V(IV)
T i (IV)
Figure 2. Scheme for the separation of 44Ti from an irradiated vanadium target.
to the dried Vz05. The volume of acid needed was calculated by using eq 1and 2. The total number of moles of H+ present due to HF must be calculated from the ionization constant in order to ensure that sufficient H+ is present. The exact amount of NH20H.HC1 needed was added. The solution was boiled for 10 min, and after cooling, it was diluted to 900 mL (-0.1 MHC1-1 M HF). I t was found that 44Tiwas eluted slowly from the column if more than 400 mL of the solution was passed through the column. This may be due to the high
concentration of HF. The solution was passed through three columns, i.e., 300 mL through each column. The column was washed with 0.1 M HCl-1 M HF. 44TiF62-was eluted with 6 M HC1-1 M HF solution. Eluants from all three columns were combined and evaporated to dryness. 44Tiwas taken up in 30 mL of 0.1 M HC1-1 M HF. Two milliliters of 2 M NH20H.HC1was added, and the solution was boiled for 5 min. The solution was diluted to 30 mL and passed through a Dowex 1X-2 anion-exchangecolumn. The column was washed with four column volumes of 0.1 M HC1-1 M HF. 44TiF62was eluted with 6 M HC1-1 M H F and assayed. The 44Ti solution was evaporated to dryness, and the titanium was dissolved in 5 mL of 3 M "OB. The solution (1 mL) was sealed in a polyethylene vial and analyzed for Ti and V by NAA. The 5-mL solution contained 21 pg of V and 0.22 mg of Ti. Titanium carrier (25-50 ppm) was present in the vanadium target as stated by the supplier. There are two sources of carrier titanium in the 44Ti: the titanium present in the vanadium target and the other stable isotopes of titanium produced due to the V(p,x) nuclear reactions. The contribution due to the latter source is negligible compared to the earlier one. Vanadium was reduced from 9 g to 21 pg. The decontamination factor for vanadium is 4.0 X lo6. The specific activity of the solution was 0.65 pCi/mg of titanium. We expect the procedure to be applicable to commercial production of 44Ti for biomedical generator applications. Availability of no-carrier-added 44Tiis required for effective performance of the generator. In addition near carrier-free 44Ti-44S~ has been suggested as an ideal standard for nuclear spectrometry due to the y spectrum and as a source for positrons (Es+= 1.471 MeV) for slow positron spectrometry.
ACKNOWLEDGMENT We appreciate the cooperation of A. Blotcky for NAA activations at the TRIGA reactor at the Omaha V. A. Medical Center, NB, and E. Lebowitz for scheduling the BLIP irradiations. Registry No. 44Ti,15749-33-4;V, 7440-62-2. LITERATURE CITED Lambrecht, R. M. Radiochim. Acta 1983, 3 4 , 9. Greene, M. W.; Hillrnan, M. Int. J . Appi. Radiat. Isot. 1967, 18, 540. Mirza, M. Y.; Aziz, A. Radiochim. Acta 1969, 7 7 , 43. Seidl, V. E.; Lieser, K. H. Radiochim. Acta 1973, 19, 196. Hara, T.;Freed, B. R. I n t . J . Appi. Radiat. Isot. 1973, 2 4 , 373. Rosoff, B.; Siegei, E.; Williams, G. L.; Spencer, H. I n t . J . Appl. Radia t . Isot. 1963, 14, 129. Rosoff, B.; Spencer, H.; Cohn, S. H.; Gusmano, E. A. I n t . J . Appi. Radiat. Isot. 1965, 16, 479. Syed, I . B.; Hosain, F. Appi. RadiologyINM 82 1975. Kanza-Kanza, L., Cogneau, M.. Mahieu, B., Apers, D. J. Radiochem. Radioanai. Lett. 1982, 5 4 , 7. Nelson, F.; Rush, R. M.; Kraus, K. A. J . A m . Chem. SOC. 1960, 82, 339. Cotton, F. A,; Wiikinson, G. "Advanced Inorganic Chemistry," 4th ed.; Wiley-Interscience: New York, 1980; p 701. Cotton, F. A.; Wilkinson, G. "Advanced Inorganic Chemistry," 4th ed.; Wiley-Interscience: New York, 1980; p 717.
RECEIVED for review July 12, 1985. Accepted September 3, 1985. This research was carried out at Brookhaven National Laboratory under Contract DE-AC02-76CH00016 with the U S . Department of Energy and supported by its Office of Health and Environmental Research.
