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The rapid determination of total bromine and iodine in biological fluids by neutron activation
Clin. Biochem. 13 {6) 277-278 (1980)
The Rapid Determination of Total Bromine and Iodine in Biological Fluids by Neutron Activation JIRI HOLZBECHER and DOUGLAS E. RYAN Trace Analysis Research Centre, Chemistry Department, Dalhousie University, Halifax, Nova Scotia, B3H 4J1
Total bromine and iodinc are instrumentally determined in I mL samples of body fluids by neutron activation under a boron shield at normal concentration levels. No sample treatment is necessary. Bromine is determined by its 8°Br nuclide (617.0 keY; TII2 ----18.0 min) and iodine by its 1281nuclide (442.7 keV; T112= 25.0 min). The method is rapid; four bromine and two iodine determinations can be done in one hour. Bromine and iodine can be detected down to 14 ,g/dL (1.75 ~mol/L) and 2.9 ~g/dL (0.23 ~mol/L), respectively. THERE IS NEED IN CLINICALLABORATORIESfor fast and reliable methods for the determination of bromine and iodine in body fluids. Sodium bromine, is still occasionally used as a tranquilizer. The methods currently employed for bromine d e t e r m i n a t i o n , b as e d on c o l o r i m e t r y {1.2) or gas c h r o m a t o g r a p h y ( 3 ) can, h o w e v e r , m e a s u r e only e l e v a t e d bromine levels and require considerable sample handling and preparation. Blood iodine levels are i m p o r ta n t in thyroid function studies and the rapid rise of iodine blood concentrations after application of tincture of iodine on the skin of patients undergoing s u r g e r y (4) necessitates fast and simple methods for iodine determination. The determination of low iodine levels in biological materials has required the ashing of the organic material prior to analysis (5,6, 7). In the neutron activation analysis method described, ashing is unnecessary. N e u t r o n sources are becoming more readily accessible; in Canada, for example, a number of S L O W P O K E reactors have been established across the country. The S L O W P O K E react or is an ideal tool for hospital and research laboratories; it has a v e r y stable neutron flux (8) and is particularly suitable for analyses making use of relatively short-lived isotopes. Body tissues and fluids contain relatively large amounts of sodium and chlorine and the resulting activities of 24Na and 38CI are often an interference in the de t e r m i n at i o n of o t h e r isotopes by neutron activation. Sodium can be r e m o v e d prior to analysis by adsorption on antimony pentoxide (9) but digestion of organic s a m p l e s b e f o r e s o d i u m s e p a r a t i o n is, of c o u r s e , necessary. A simpler way to reduce the activity from 24Na and 3sCl production is to irradiate the sample under a cadmium or boron shield. The shield passes only Correspondence: Douglas E. Ryan
neutrons with energies greater than thermal so that the activities produced by sodium and chlorine atoms are greatly reduced; these isotopes have high cadmium or boron ratios (i.e.ratio of activity without shield to activity with shield). Other isotopes, such as ~ 0 , x~I or 8°Br have low boron ratios and, since their activities are only slightly affected by the shield, can be determined in matrices containing large amounts of sodium chloride. A recent paper (10) has described the determination of traces of uranium in urine using a boron shield and this paper deals with the determination of iodine and bromine in whole blood, serum, plasma and urine. MATERIALS AND METHODS
All samples were irradiated in an outer irradiation position of a SLOWPOKE reactor; details of flux composition have been previously described (8). Gamma ray measurements were made with a TN-11 Pulse Height Analyzer (Tracor Northern) using a Canberra Ge(Li) detector having a 9.50/0 relative efficiency and 1.9 keV resolution at 1332 keV. Bromine was measured via 80Br, T1/2 = 18.0 min, 617.0 keV, and iodine by 128I, TI/2 = 25.0 rain, 442.7 keV. Because of the multielement capability of neutron activation, sodium and chlorine can also be readily determined via their 24Na, Tll2 ffi 15.0 h, 1368.7 keV, and 3sCl, TI~z = 37.3 rain, 1642.0 keV nuclides. The concentrations of aluminium and potassium are sufficiently high in urine to permit their direct determination; nuclides used were 28A1, Tl/2 ffi 2.3 min, 1778.9 keV, and 42K, Tl/2 = 12.5 h, 1524.7 keV. The boron shield was prepared from 3.2 mm thick B4C loaded elastomer sheet (Flex/Boron, Reactor Experiments) containing 250/0 w/w boron. Working standards were prepared by addition of microgram amounts of the elements of interest to 1 mL amounts of samples or distilled water in "2/5 dram" polyethylene vials. Pooled serum, outpatient plasma, whole blood and 24 h urine samples were used in the investigation. Procedure
The 1 mL samples of whole blood, serum, plasma or urine were sealed in the polyethylene vials and placed in boron shielded irradiation capsules. If only bromine was required, urine, whole blood, serum or plasma samples were irradiated for 10 min and then counted for 10 rain after a 3 rain waiting period. The determination of iodine in whole blond, serum and plasma necessitates a 30 rain irradiation and count after a 7 min decay. The neutron flux for all irradiations was 5 x 1011 n cmas a. Blanks, standards and samples with standard additions were also run.
278
HOLZBECHER AND RYAN RESULTSANDDISCUSSION
The following ranges of concentrations were found in 24 h urines: 19-26 ~g/dL (1.50-2.05 /amol/L) iodine and 213-520 ~g/dL (26.6-65.1 ~anol/L} bromine corresponding to 0.05-0.25 mg/24 h iodine and 0.82-3.55 mg/24 h bromine; these compare well with r e p o r t e d l i t e r a t u r e values (11). E i g h t s e p a r a t e analyses of pooled serum for bromine, iodine, sodium and chlorine agreed within -+ 10%. O u t p a t i e n t s ' blood and plasma samples gave bromine and iodine values in the normal range (310-670 pg/dL Br and 5.8-8.5 #g/dL I in plasma, and 130-810 #g/dL Br and 1.5-7.2 #g/dL I in whole blood) (11); the corresponding ranges in SI units are 38.8-83.8 ~,nol/L bromine and 0.46-0.67 ~mol/L iodine in plasma, and. 16.3-101.3 ~mol/L bromine and 0.12-0.57 ~mol/L iodine in whole blood. The detection limits, based on 2 x x/background, for bromine and iodine in biological fluids for 10 rain irradiation and count are 19 and 5.7 #g/dL (2.4 and 0.45 ~nol/L), respectively. A 30 min irradiation and count improves the detection limits to 14 #g/dL (1.75 ~mol/L) for bromine and to 2.9 ~g/dL (0.23 /~rnol/L) for iodine. The analytical sensitivities, expressed in counts per microgram, for 10 min irradiation and count are 210 and 690 for bromine and iodine respectively; for 30 min irradiation and count, the respective sensitivities are 810 and 3480. The boron ratio was 5.8 for 8°Br and 3.5 for 128I. Boron ratios of a p p r o x i m a t e l y 60 were shown by 28Al, 3sC1, 42K and 24Na. All samples were initially e v a p o r a t e d to dryness before irradiation to p r e v e n t any flux thermalization by water. Although thermalization does t a k e place in w a t e r containing samples, drying was found to be unnecessary because of its small effect; for example, d r y i n g of urine prior to activation improves the detection limit for bromine from 14 to 12 ~g/dL (1.75 to 1.50 wnol/L) and for iodine from 2.9 to 2.4 ~g/dL (0.23 to 0.19
~mol/L).
ACKNOWLEDGEMENT This work was s u p p o r t e d by a g r a n t from N a t u r a l Sciences and E n g i n e e r i n g Research Council of Canada.
REFERENCES 1. Sunshine, I. In: Methodology for analytical toxicology, Editor: I. Sunshine, CRC Press, Cleveland. pp. 54, 55 (1975). 2. Street, H.V. Determination of bromide in blood. Clin. Chim. Acta. 5, 938-941 (1960). 3. Cimbura, G., and Wells, J. In Methodology for analytical toxicology, Editor: I. Sunshine, CRC Press, Cleveland. pp. 55, 56 (1975L 4. Reeve, T.S., Coupland, G.A.E., and Hales, I.B. The effect on serum iodine levels of painting tincture of iodine on the skin. Med. J. Aust. 1,891-892 (1973). 5. Hoch, H., and Lewallen, C.G. Cerate-arsenite measurement of iodine in the subnanogram range. Clin. Chem. 15, 204-215 (1969). 6. Harden, R. MEG., and Bastomsky, C.H. Measurement of iodine concentration in biological material. Clin. Chem. 17, 1020-1023 (1971}. 7. Spector, H., and Hamilton, T.S. The microdetermination of iodine in biological materials with special reference to the combustion of samples in the Parr oxygen bomb. J. BioL Chem. 161, 127-135 (1945). 8. Ryan, D.E., Stuart, D.C., and Chattopadhyay, A. Rapid multielement neutron activation analysis with a Slowpoke reactor. Anal Chim. Acto. 100, 87-93 (1978). 9. Ward, N.I., and Ryan, D.E. Multi-element analysis of blood for trace metals by neutron activation analysis. AnaL Chim. Acto. 105, 185-197 (1979). 10. Holzbecher, J., and Ryan, D.E. Determination of uranium by thermal and epithermat neutron activation in natural waters and in human urine. AnaL Chim. Acto. 19, 405-408 (1980). Ii. lyengar, G.V., Kollmer, W.E., and Bowen, H.J.M. The elemental composition of human tissues and body fluids. Verlag Chemie, Weinheim {1978}.
The Rapid Determination of Total Bromine and Iodine in Biological Fluids by Neutron Activation JIRI HOLZBECHER and DOUGLAS E. RYAN Trace Analysis Research Centre, Chemistry Department, Dalhousie University, Halifax, Nova Scotia, B3H 4J1
Total bromine and iodinc are instrumentally determined in I mL samples of body fluids by neutron activation under a boron shield at normal concentration levels. No sample treatment is necessary. Bromine is determined by its 8°Br nuclide (617.0 keY; TII2 ----18.0 min) and iodine by its 1281nuclide (442.7 keV; T112= 25.0 min). The method is rapid; four bromine and two iodine determinations can be done in one hour. Bromine and iodine can be detected down to 14 ,g/dL (1.75 ~mol/L) and 2.9 ~g/dL (0.23 ~mol/L), respectively. THERE IS NEED IN CLINICALLABORATORIESfor fast and reliable methods for the determination of bromine and iodine in body fluids. Sodium bromine, is still occasionally used as a tranquilizer. The methods currently employed for bromine d e t e r m i n a t i o n , b as e d on c o l o r i m e t r y {1.2) or gas c h r o m a t o g r a p h y ( 3 ) can, h o w e v e r , m e a s u r e only e l e v a t e d bromine levels and require considerable sample handling and preparation. Blood iodine levels are i m p o r ta n t in thyroid function studies and the rapid rise of iodine blood concentrations after application of tincture of iodine on the skin of patients undergoing s u r g e r y (4) necessitates fast and simple methods for iodine determination. The determination of low iodine levels in biological materials has required the ashing of the organic material prior to analysis (5,6, 7). In the neutron activation analysis method described, ashing is unnecessary. N e u t r o n sources are becoming more readily accessible; in Canada, for example, a number of S L O W P O K E reactors have been established across the country. The S L O W P O K E react or is an ideal tool for hospital and research laboratories; it has a v e r y stable neutron flux (8) and is particularly suitable for analyses making use of relatively short-lived isotopes. Body tissues and fluids contain relatively large amounts of sodium and chlorine and the resulting activities of 24Na and 38CI are often an interference in the de t e r m i n at i o n of o t h e r isotopes by neutron activation. Sodium can be r e m o v e d prior to analysis by adsorption on antimony pentoxide (9) but digestion of organic s a m p l e s b e f o r e s o d i u m s e p a r a t i o n is, of c o u r s e , necessary. A simpler way to reduce the activity from 24Na and 3sCl production is to irradiate the sample under a cadmium or boron shield. The shield passes only Correspondence: Douglas E. Ryan
neutrons with energies greater than thermal so that the activities produced by sodium and chlorine atoms are greatly reduced; these isotopes have high cadmium or boron ratios (i.e.ratio of activity without shield to activity with shield). Other isotopes, such as ~ 0 , x~I or 8°Br have low boron ratios and, since their activities are only slightly affected by the shield, can be determined in matrices containing large amounts of sodium chloride. A recent paper (10) has described the determination of traces of uranium in urine using a boron shield and this paper deals with the determination of iodine and bromine in whole blood, serum, plasma and urine. MATERIALS AND METHODS
All samples were irradiated in an outer irradiation position of a SLOWPOKE reactor; details of flux composition have been previously described (8). Gamma ray measurements were made with a TN-11 Pulse Height Analyzer (Tracor Northern) using a Canberra Ge(Li) detector having a 9.50/0 relative efficiency and 1.9 keV resolution at 1332 keV. Bromine was measured via 80Br, T1/2 = 18.0 min, 617.0 keV, and iodine by 128I, TI/2 = 25.0 rain, 442.7 keV. Because of the multielement capability of neutron activation, sodium and chlorine can also be readily determined via their 24Na, Tll2 ffi 15.0 h, 1368.7 keV, and 3sCl, TI~z = 37.3 rain, 1642.0 keV nuclides. The concentrations of aluminium and potassium are sufficiently high in urine to permit their direct determination; nuclides used were 28A1, Tl/2 ffi 2.3 min, 1778.9 keV, and 42K, Tl/2 = 12.5 h, 1524.7 keV. The boron shield was prepared from 3.2 mm thick B4C loaded elastomer sheet (Flex/Boron, Reactor Experiments) containing 250/0 w/w boron. Working standards were prepared by addition of microgram amounts of the elements of interest to 1 mL amounts of samples or distilled water in "2/5 dram" polyethylene vials. Pooled serum, outpatient plasma, whole blood and 24 h urine samples were used in the investigation. Procedure
The 1 mL samples of whole blood, serum, plasma or urine were sealed in the polyethylene vials and placed in boron shielded irradiation capsules. If only bromine was required, urine, whole blood, serum or plasma samples were irradiated for 10 min and then counted for 10 rain after a 3 rain waiting period. The determination of iodine in whole blond, serum and plasma necessitates a 30 rain irradiation and count after a 7 min decay. The neutron flux for all irradiations was 5 x 1011 n cmas a. Blanks, standards and samples with standard additions were also run.
278
HOLZBECHER AND RYAN RESULTSANDDISCUSSION
The following ranges of concentrations were found in 24 h urines: 19-26 ~g/dL (1.50-2.05 /amol/L) iodine and 213-520 ~g/dL (26.6-65.1 ~anol/L} bromine corresponding to 0.05-0.25 mg/24 h iodine and 0.82-3.55 mg/24 h bromine; these compare well with r e p o r t e d l i t e r a t u r e values (11). E i g h t s e p a r a t e analyses of pooled serum for bromine, iodine, sodium and chlorine agreed within -+ 10%. O u t p a t i e n t s ' blood and plasma samples gave bromine and iodine values in the normal range (310-670 pg/dL Br and 5.8-8.5 #g/dL I in plasma, and 130-810 #g/dL Br and 1.5-7.2 #g/dL I in whole blood) (11); the corresponding ranges in SI units are 38.8-83.8 ~,nol/L bromine and 0.46-0.67 ~mol/L iodine in plasma, and. 16.3-101.3 ~mol/L bromine and 0.12-0.57 ~mol/L iodine in whole blood. The detection limits, based on 2 x x/background, for bromine and iodine in biological fluids for 10 rain irradiation and count are 19 and 5.7 #g/dL (2.4 and 0.45 ~nol/L), respectively. A 30 min irradiation and count improves the detection limits to 14 #g/dL (1.75 ~mol/L) for bromine and to 2.9 ~g/dL (0.23 /~rnol/L) for iodine. The analytical sensitivities, expressed in counts per microgram, for 10 min irradiation and count are 210 and 690 for bromine and iodine respectively; for 30 min irradiation and count, the respective sensitivities are 810 and 3480. The boron ratio was 5.8 for 8°Br and 3.5 for 128I. Boron ratios of a p p r o x i m a t e l y 60 were shown by 28Al, 3sC1, 42K and 24Na. All samples were initially e v a p o r a t e d to dryness before irradiation to p r e v e n t any flux thermalization by water. Although thermalization does t a k e place in w a t e r containing samples, drying was found to be unnecessary because of its small effect; for example, d r y i n g of urine prior to activation improves the detection limit for bromine from 14 to 12 ~g/dL (1.75 to 1.50 wnol/L) and for iodine from 2.9 to 2.4 ~g/dL (0.23 to 0.19
~mol/L).
ACKNOWLEDGEMENT This work was s u p p o r t e d by a g r a n t from N a t u r a l Sciences and E n g i n e e r i n g Research Council of Canada.
REFERENCES 1. Sunshine, I. In: Methodology for analytical toxicology, Editor: I. Sunshine, CRC Press, Cleveland. pp. 54, 55 (1975). 2. Street, H.V. Determination of bromide in blood. Clin. Chim. Acta. 5, 938-941 (1960). 3. Cimbura, G., and Wells, J. In Methodology for analytical toxicology, Editor: I. Sunshine, CRC Press, Cleveland. pp. 55, 56 (1975L 4. Reeve, T.S., Coupland, G.A.E., and Hales, I.B. The effect on serum iodine levels of painting tincture of iodine on the skin. Med. J. Aust. 1,891-892 (1973). 5. Hoch, H., and Lewallen, C.G. Cerate-arsenite measurement of iodine in the subnanogram range. Clin. Chem. 15, 204-215 (1969). 6. Harden, R. MEG., and Bastomsky, C.H. Measurement of iodine concentration in biological material. Clin. Chem. 17, 1020-1023 (1971}. 7. Spector, H., and Hamilton, T.S. The microdetermination of iodine in biological materials with special reference to the combustion of samples in the Parr oxygen bomb. J. BioL Chem. 161, 127-135 (1945). 8. Ryan, D.E., Stuart, D.C., and Chattopadhyay, A. Rapid multielement neutron activation analysis with a Slowpoke reactor. Anal Chim. Acto. 100, 87-93 (1978). 9. Ward, N.I., and Ryan, D.E. Multi-element analysis of blood for trace metals by neutron activation analysis. AnaL Chim. Acto. 105, 185-197 (1979). 10. Holzbecher, J., and Ryan, D.E. Determination of uranium by thermal and epithermat neutron activation in natural waters and in human urine. AnaL Chim. Acto. 19, 405-408 (1980). Ii. lyengar, G.V., Kollmer, W.E., and Bowen, H.J.M. The elemental composition of human tissues and body fluids. Verlag Chemie, Weinheim {1978}.