Chimica Acta, 82 (1976) 427-430 OFJsevier Scientific Publishing Company, Amsterdam-
Analytica
Printed in The Netherlands
427
Short Communication
DETERMINATION
CHRISTINE Department (England)
OF MERCURY
IN FINGER NAILS AND BODY HAIR
A HELSBY of Conservative
Dentistry,
University
of Manchester,
Manchester
15 6FH
(Received 27th September 1975)
Contamination of dental personnel with mercury has been estimated from the analysis of finger nails, toe nails and body hair by neutron activation analysis [1, 21, but this technique is expensive for screening work. Recently, the flameless cold-vapour atomic absorption technique described by Hatch and Ott [3] has been used for the analysis of a number of body tissues. Hair has been analyzed after digestion either with a mixture of concentrated nitric and sulphuric acids and potassium permanganate at room temperature 141 or with sodium hydroxide solution (11.2 M) at 125 “C [5]. Other body tissues have been analysed after similar lengthy digestions with concentrated acids and strong oxidants 163, or after digestion in a Uni-Seal decomposition vessel with nitric acid at 150 “C for 30-60 mm [7]. Biological materials have been analysed by Schijniger oxygen flask combustion and the cold-vapour technique applied either directly [8,9] or after an amalgamation step [lo]. Ure and Shand [9] replaced the conventional platinum basket of the Schijniger method with a perforated tantalum basket to overcome any interference from platinum in the subsequent determination. The procedure described below involves Schoniger flask combustion of nails and hair followed by flameless cold-vapour analysis. The method is considerably cheaper and faster than neutron activation analysis. An additional advantage is the use of the combustion flask as an aeration flask so that the possibility of transference losses is eliminated.
Experimental Instrumentation. A Perkin-Elmer model 303 atomic absorption spectrophotometer was fitted with a recorder-readout accessory and a Hitachi 165 recorder. The spectral source was a mercury Intensitron hollow-cathode lamp operated at 253.65 nm. Aeration apparatus. Air (1.5 1 min-’ ) was pumped (Charles Austen Capex Mark II pump) through a Drechsel bottle head (porosity 2 glass filter) into a 250-ml Quickfit conical flask. The outlet from the flask was connected to a
drying tube containing magnesium perchlorate. The air then passed into a 15cm gas cell of lo-mm diameter fitted with silica windows and positioned in the optical path of the spectrometer_ The air returned to the pump to complete the closed circuit. The circuit contained a 3-way valve by which the air stream could. be passed through a scrubbing tube containing activated charcoal, which removed any mercury vapour from the air-stream after absorption measurements had been completed_ Reagents and preparation. All new glassware was boiled in 6 M nitric acid for 20 min before use. After washing, all glassware was rinsed several times with 10 7%(v/v) nitric acid; no organic solvents were used. All the acids were Aristar grade and the other chemicals were Analar grade. Solutions were prepared with distilled-deionized water. The mercury was liberated with tin(II) chloride (20 % w/v) prepared in 5 M hydrochloric acid. This solution was aerated for 2 h before use to remove any traces of mercury present in the reagent and acid. Mercury solutions. A 1000 p.p.m_ stock solution of mercury as HgCl* (B.D-H.) was used for the preparation of standards by suitable dilutions. For the recovery studies, mercury(I1) chloride and phenylmercury acetate were USed.
Procedure_ Use up to 25 mg of nail or hair sample. Wrap nail samples in Whatman No. 541 filter paper, or insert hair samples in gelatin capsules. Introduce 6 ml of 50 % (v/v) nitric acid into a dry 250-ml Quickfit conical flask, flush with a rapid flow of oxygen for a few seconds, ignite the fuse and burn the sample in the usual way. When combustion is complete, shake the flask for 1 min and allow to stand for 5 min. Wash the stopper and gauze with 2 ml of 50 % (v/v) nitric acid followed by 10 ml of deionized water, and dilute to 140 ml with deionized water. Stir the solution with a magnetic stirrer for 5 min to remove any nitrous oxide fumes. Add 20 ml of tin(I1) chloride solution, quickly connect to the Drechsel head of the aeration apparatus and mix welL Aerate the sample solution and conduct the air-mercury vapour through the gas cell until a steady equilibrium is achieved on the recorder. Record the maximum peak deflection. Use the 3-way valve to conduct the air-mercury vapour through the scrubber until the recorder pen returns to zero deflection. Calibration. To S-ml portions of 50 % (v/v) nitric acid in 250-ml Quickfit conical flasks add 0.1, 0.2, 0.3 or 0.4 ml of a freshly prepared mercury standard solution (1 pg ml-‘) and dilute to 140 ml with deionized water. Repeat the relevant stages of the procedure described above. The filter paper and gelatin capsule did not give an absorption reading for mercury.
429
Results and discussion Several acids have been used as absorbents for mercury in the oxygen flask including hydrochloric acid [lo] and nitric acid [ 111. Both concentrated and dilute hydrochloric acid were found to give low and erroneous results with 0.1 ng of mercury, and after use the platinum basket had a dull etched appearance. These low results may have been due to attack on the platinum basket resulting in platinum interference as observed by Ure and Shand 191. When concentrated nitric acid was used, dense brown fumes were produced after the combustion, and enhanced absorption was obtained owing to interference by nitrous oxide [12]. The optimal absorbent concentration of nitric acid was found to be 50 % (v/v); this concentration gave reproducible results, and there was no interference or attack on the platinum basket. To evaluate the method, recovery studies were carried out with finger nails from control subjects who had no known contact with mercury. The finger nails were wrapped in filter paper which had previously been spiked with inorganic mercury (as HgC12) and organic mercury (as C6H,HgC02CH3). The technique of spiking the filter paper had previously been proved to be valid by burning filter paper spiked with 0.1 r.cgof mercury; five such combustions gave a mean absorbance of 0.0308, a standard deviation of 0.00045 and a relative standard deviation of 1.45 70. The results of the recovery studies (Table 1) showed an overall recovery of 92.5 (k5.3) % for added mercury(I1) chloride, and 94.2 (26.5) % for added phenylmercury acetate. A number of samples from dental personnel, who had little or no direct contact with the preparation of mercury amalgams, were analysed by the technique described above. The levels of mercury found in nails and hair are shown in Table 2 and compared with the levels reported by other workers [l, 21 who used neutron activation analysis_ The results to date indicate that TABLE
1
Recovery
of mercury
addedto fingernailsfrom controlsubjects
Hg added kg) Added 0.1 0.2 0.3
as HgClza
-4dded 0.1 0.2 0.3
as C,H,HgCO,CH,b
=Rlean mercury bMean mercury
concentration concentration
No. of detns.
Hg found f sr kg)
7%Recovery
6 5 6
0.094 0.185 0.272
_f 0.007 + 0.012 f 0.007
94.25 92.6 90.7
2 6.8 2 5.5 f 2.4
5 4 3
0.095 0.177 0.299
f 0.005 i 0.006 c 0.022
95.5 88.4 99.9
f 5.1 f 2.8 + 7.1
* .sr
of nail sample 0.92 p_p.m_ (4 determinations; s, = 3.8 ‘ZJ). of nail samples 1.21 p.p_m. (4 determinations;~, = 4.1 95).
430 TABLE
2
Levels of mercury (p.p.m)
found in nails and hair samples from dental personnel
Sample
This procedurea (8 individuals)
Ref 1 (20 individuals)
Ref 2 (167 individuals)
Finger Nail Toe Nail Head Hair Axillary hair
3 -84 0.31- 3.7 1.02-10.0 O-613.1
68.76 9.3 .32.25 7.88
1.33-3070 0.76 181 1.17160 -
Pubic hair
0.85-
-
O-58-
2.56
404
ahIeans of triplicate analyses.
this technique which is relatively quick and inexpensive can be used to monitor the possible health hazards of mercury to dental personnel. The author would like to thank Professor G. S. Nixon for his interest in this work.
REFERENCES 1 2 3 4 5 6 7 8 9 10 11 12
G.S. Nixonand H.Smith,J.Oral Ther. Pharm., 1 (1965)512. J. M. A. Leniham, H. Smith and W. Harvey, Brit. Dent. J., 135 (1973) 365. W. R. Hatch and W. L Ott, Anal. Chem., 40 (1968) 2085. P. J. Nord, M. P. Kadaba and J. Sorenson, Arch. Environ. Health, 27 (1973) 40. T. Giovanoli-Jakubczak, M. R. Greenwood, J. Crispin Smith and T. W. Clarkson, Clin. Chem., 20 (1974) 222. N. K Mottet and R. L. Body, Arch. Environ. Health, 29 (1974) 18. P. C. Stein, E. E. Campbell, W. D. Moss and P. Trujillo, Arch. Environ. Health, 29 (1974) 25. C. A Bathe, D. Gutenmann and D. J. Lisk, Science, 172 (1971) 951. A. M. Ure and C. A Shand, Anal. Chim. Acta, 72 (1974) 63. I. Okuno, R A Wilson and R. E White, J. Ass. Offic. Anal. Chem., 55 (1972) 96. B. C. Southmorth, J. I% Hodecker and K. D. Fleischer, Anal. Chem., 30 (1958) 1152. W_ L Hoover, J. R Melton and P_ A_ Howard, J. Ass. Offic. Anal. Chem., 52 (1971) 860.
Analytica
Printed in The Netherlands
427
Short Communication
DETERMINATION
CHRISTINE Department (England)
OF MERCURY
IN FINGER NAILS AND BODY HAIR
A HELSBY of Conservative
Dentistry,
University
of Manchester,
Manchester
15 6FH
(Received 27th September 1975)
Contamination of dental personnel with mercury has been estimated from the analysis of finger nails, toe nails and body hair by neutron activation analysis [1, 21, but this technique is expensive for screening work. Recently, the flameless cold-vapour atomic absorption technique described by Hatch and Ott [3] has been used for the analysis of a number of body tissues. Hair has been analyzed after digestion either with a mixture of concentrated nitric and sulphuric acids and potassium permanganate at room temperature 141 or with sodium hydroxide solution (11.2 M) at 125 “C [5]. Other body tissues have been analysed after similar lengthy digestions with concentrated acids and strong oxidants 163, or after digestion in a Uni-Seal decomposition vessel with nitric acid at 150 “C for 30-60 mm [7]. Biological materials have been analysed by Schijniger oxygen flask combustion and the cold-vapour technique applied either directly [8,9] or after an amalgamation step [lo]. Ure and Shand [9] replaced the conventional platinum basket of the Schijniger method with a perforated tantalum basket to overcome any interference from platinum in the subsequent determination. The procedure described below involves Schoniger flask combustion of nails and hair followed by flameless cold-vapour analysis. The method is considerably cheaper and faster than neutron activation analysis. An additional advantage is the use of the combustion flask as an aeration flask so that the possibility of transference losses is eliminated.
Experimental Instrumentation. A Perkin-Elmer model 303 atomic absorption spectrophotometer was fitted with a recorder-readout accessory and a Hitachi 165 recorder. The spectral source was a mercury Intensitron hollow-cathode lamp operated at 253.65 nm. Aeration apparatus. Air (1.5 1 min-’ ) was pumped (Charles Austen Capex Mark II pump) through a Drechsel bottle head (porosity 2 glass filter) into a 250-ml Quickfit conical flask. The outlet from the flask was connected to a
drying tube containing magnesium perchlorate. The air then passed into a 15cm gas cell of lo-mm diameter fitted with silica windows and positioned in the optical path of the spectrometer_ The air returned to the pump to complete the closed circuit. The circuit contained a 3-way valve by which the air stream could. be passed through a scrubbing tube containing activated charcoal, which removed any mercury vapour from the air-stream after absorption measurements had been completed_ Reagents and preparation. All new glassware was boiled in 6 M nitric acid for 20 min before use. After washing, all glassware was rinsed several times with 10 7%(v/v) nitric acid; no organic solvents were used. All the acids were Aristar grade and the other chemicals were Analar grade. Solutions were prepared with distilled-deionized water. The mercury was liberated with tin(II) chloride (20 % w/v) prepared in 5 M hydrochloric acid. This solution was aerated for 2 h before use to remove any traces of mercury present in the reagent and acid. Mercury solutions. A 1000 p.p.m_ stock solution of mercury as HgCl* (B.D-H.) was used for the preparation of standards by suitable dilutions. For the recovery studies, mercury(I1) chloride and phenylmercury acetate were USed.
Procedure_ Use up to 25 mg of nail or hair sample. Wrap nail samples in Whatman No. 541 filter paper, or insert hair samples in gelatin capsules. Introduce 6 ml of 50 % (v/v) nitric acid into a dry 250-ml Quickfit conical flask, flush with a rapid flow of oxygen for a few seconds, ignite the fuse and burn the sample in the usual way. When combustion is complete, shake the flask for 1 min and allow to stand for 5 min. Wash the stopper and gauze with 2 ml of 50 % (v/v) nitric acid followed by 10 ml of deionized water, and dilute to 140 ml with deionized water. Stir the solution with a magnetic stirrer for 5 min to remove any nitrous oxide fumes. Add 20 ml of tin(I1) chloride solution, quickly connect to the Drechsel head of the aeration apparatus and mix welL Aerate the sample solution and conduct the air-mercury vapour through the gas cell until a steady equilibrium is achieved on the recorder. Record the maximum peak deflection. Use the 3-way valve to conduct the air-mercury vapour through the scrubber until the recorder pen returns to zero deflection. Calibration. To S-ml portions of 50 % (v/v) nitric acid in 250-ml Quickfit conical flasks add 0.1, 0.2, 0.3 or 0.4 ml of a freshly prepared mercury standard solution (1 pg ml-‘) and dilute to 140 ml with deionized water. Repeat the relevant stages of the procedure described above. The filter paper and gelatin capsule did not give an absorption reading for mercury.
429
Results and discussion Several acids have been used as absorbents for mercury in the oxygen flask including hydrochloric acid [lo] and nitric acid [ 111. Both concentrated and dilute hydrochloric acid were found to give low and erroneous results with 0.1 ng of mercury, and after use the platinum basket had a dull etched appearance. These low results may have been due to attack on the platinum basket resulting in platinum interference as observed by Ure and Shand 191. When concentrated nitric acid was used, dense brown fumes were produced after the combustion, and enhanced absorption was obtained owing to interference by nitrous oxide [12]. The optimal absorbent concentration of nitric acid was found to be 50 % (v/v); this concentration gave reproducible results, and there was no interference or attack on the platinum basket. To evaluate the method, recovery studies were carried out with finger nails from control subjects who had no known contact with mercury. The finger nails were wrapped in filter paper which had previously been spiked with inorganic mercury (as HgC12) and organic mercury (as C6H,HgC02CH3). The technique of spiking the filter paper had previously been proved to be valid by burning filter paper spiked with 0.1 r.cgof mercury; five such combustions gave a mean absorbance of 0.0308, a standard deviation of 0.00045 and a relative standard deviation of 1.45 70. The results of the recovery studies (Table 1) showed an overall recovery of 92.5 (k5.3) % for added mercury(I1) chloride, and 94.2 (26.5) % for added phenylmercury acetate. A number of samples from dental personnel, who had little or no direct contact with the preparation of mercury amalgams, were analysed by the technique described above. The levels of mercury found in nails and hair are shown in Table 2 and compared with the levels reported by other workers [l, 21 who used neutron activation analysis_ The results to date indicate that TABLE
1
Recovery
of mercury
addedto fingernailsfrom controlsubjects
Hg added kg) Added 0.1 0.2 0.3
as HgClza
-4dded 0.1 0.2 0.3
as C,H,HgCO,CH,b
=Rlean mercury bMean mercury
concentration concentration
No. of detns.
Hg found f sr kg)
7%Recovery
6 5 6
0.094 0.185 0.272
_f 0.007 + 0.012 f 0.007
94.25 92.6 90.7
2 6.8 2 5.5 f 2.4
5 4 3
0.095 0.177 0.299
f 0.005 i 0.006 c 0.022
95.5 88.4 99.9
f 5.1 f 2.8 + 7.1
* .sr
of nail sample 0.92 p_p.m_ (4 determinations; s, = 3.8 ‘ZJ). of nail samples 1.21 p.p_m. (4 determinations;~, = 4.1 95).
430 TABLE
2
Levels of mercury (p.p.m)
found in nails and hair samples from dental personnel
Sample
This procedurea (8 individuals)
Ref 1 (20 individuals)
Ref 2 (167 individuals)
Finger Nail Toe Nail Head Hair Axillary hair
3 -84 0.31- 3.7 1.02-10.0 O-613.1
68.76 9.3 .32.25 7.88
1.33-3070 0.76 181 1.17160 -
Pubic hair
0.85-
-
O-58-
2.56
404
ahIeans of triplicate analyses.
this technique which is relatively quick and inexpensive can be used to monitor the possible health hazards of mercury to dental personnel. The author would like to thank Professor G. S. Nixon for his interest in this work.
REFERENCES 1 2 3 4 5 6 7 8 9 10 11 12
G.S. Nixonand H.Smith,J.Oral Ther. Pharm., 1 (1965)512. J. M. A. Leniham, H. Smith and W. Harvey, Brit. Dent. J., 135 (1973) 365. W. R. Hatch and W. L Ott, Anal. Chem., 40 (1968) 2085. P. J. Nord, M. P. Kadaba and J. Sorenson, Arch. Environ. Health, 27 (1973) 40. T. Giovanoli-Jakubczak, M. R. Greenwood, J. Crispin Smith and T. W. Clarkson, Clin. Chem., 20 (1974) 222. N. K Mottet and R. L. Body, Arch. Environ. Health, 29 (1974) 18. P. C. Stein, E. E. Campbell, W. D. Moss and P. Trujillo, Arch. Environ. Health, 29 (1974) 25. C. A Bathe, D. Gutenmann and D. J. Lisk, Science, 172 (1971) 951. A. M. Ure and C. A Shand, Anal. Chim. Acta, 72 (1974) 63. I. Okuno, R A Wilson and R. E White, J. Ass. Offic. Anal. Chem., 55 (1972) 96. B. C. Southmorth, J. I% Hodecker and K. D. Fleischer, Anal. Chem., 30 (1958) 1152. W_ L Hoover, J. R Melton and P_ A_ Howard, J. Ass. Offic. Anal. Chem., 52 (1971) 860.
