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Simplification of the mercurimetric procedure for organohalogen determination
MICROCHEMICAL
JOURNAL
21, 125-128 (1976)
Simplification of the Mercurimetric Procedure for Organohalogen Determination F. W. ICI
United
Stutes
Inc.,
CHENC
Wilmington,
Delaware
19897
Received December 10, 1975
INTRODUCTION
In a 1959 issue of this journal, we reported a mercurimetric procedure for organohalogen determination (3). It consisted of: (a) oxygen llask combustion, (b) absorption of the combustion products in a dilute alkaline hydrogen peroxide solution, (c) boiling to eliminate hydrogen peroxide and (d) mercurimetric titration to determine the halogen content. This procedure was widely accepted and its reliability has been confirmed by several collaborative studies (13,14). A recent statistical comparison with other established methods also appeared to favor this method (4). However, as we have noted, the analytical time can be further reduced by about 50% if one eliminates the boiling step for the removal of hydrogen peroxide. In 1961, MacDonald (10) had suggested such a shortcut in a brief statement but her suggestion was generally overlooked. This note is an attempt to recall attention to this shortcut. METHOD
The revised mercurimetric procedure is essentially the same as described previously (3), but with the boiling step after combustion eliminated. Briefly, therefore, the procedure should read: Burn the sample (l-3 mg) as usual by the oxygen tlask combustion technique (12). Absorb the combustion products in 10 ml of 6% hydrogen peroxide solution and 1 ml 0.5 N potassium hydroxide solution. Shake thoroughly after combustion and let stand for 2-5 min for complete absorption. Rinse the flask with water. The combustion mixture is diluted with 2 parts of alcohol and is adjusted to pH value of 3.5 using dilute nitric acid with aid of 5 drops of bromophenol blue (0.05% alcoholic solution). The resulting solution is titrated with 0.01 N mercuric nitrate, using 0.5% diphenylcarbazone in alcohol as the indicator. Methods of preparing reagents were described in our previous publication (3). RESULTS AND DISCUSSION
The justification for omitting the boiling step follows from the comparison of results shown in Tables 1 and 2. In these tables, data under col125 Copyright0 1976by AcademicPress,Inc. All rightsof reproductionm any form reserved.
126
F. W.
CHENG
TABLE ANALYSIS
A (no hydrogen peroxide) data collected 1959 (3)
Acrnn
B (no hydrogen peroxide) current data
d
C (with hydrogen peroxide)
d
d
found
deviation from mean
Cl% found
deviation from mean
Cl% found
deviation from mean
22.51 22.68 22.65 22.81 22.56 22.60 22.60 22.63
0.12 0.05 0.02 0.18 0.07 0.03 0.03 0.07
22.36 22.24 22.30 22.40 22.40
0.02 0.10 0.04 0.06 0.06
22.71 22.59 22.60 22.75 22.75
0.03 0.09 0.08 0.07 0.07
22.34
0.06
22.68
0.07
Cl%
Mean
1
OF CHLOROBENZOIC
41= 0.09
M
= 0.08
a Microstandard sample from British Drug House, Poote, England. Theoretical: 22.65% Cl.
umns A and B were obtained by the procedure (3) where hydrogen peroxide was expelled. Data under column A were quoted from the previous report (3), while those under column B are current results. The data under column C were obtained by the revised procedure wherein the mercurimetric titration is conducted in the presence of hydrogen peroxide. The results are in good agreement, but the analytical time is shortened by 50% using the revised procedure. Most commercial diphenylcarbazone reagents are mixtures of diphenylcarbazide and diphenylcarbazone (5,6,16). Since diphenylcarbazone is usually prepared by partial oxidation of diphenylcarbazide with hydrogen peroxide, it follows that hydrogen peroxide would not alter the function of either when it is present during the mercurimetric titration. Therefore, the presence of hydrogen peroxide is not harmful, but beneficial in the mercurimetric titration. Some investigators deliberately titrate halide in the presence of hydrogen peroxide to enhance the end-point (11). The boiling step to remove hydrogen peroxide in the original procedure is a disadvantage for organoiodine determination. Omission of this step could improve iodine analysis. Recently an iodine procedure devised by Lalancette et al. (7) had reported achieving excellent results. These were also conhrmed by collaborative studies (8,9). However, for bromine or
ORGANOHALOGEN
127
DETERMINATION
TABLE 2 ANALYSIS
A (no hydrogen peroxide) data collected 1959 (3)
OF BROMOBENZOIC
B (no hydrogen peroxide) current data
d
Mean s=
ACID”
C (presence of hydrogen peroxide) d
d
Br % found
deviation from mean
Br % found
deviation from mean
Br T found
deviation from mean
39.96 39.97 39.12 39.89 39.93 39.61 39.70 39.74 39.80 39.81
0.15 0.16 0.09 0.03 0.12 0.20 0.11 0.07 0.01 0.10
39.66 39.82 39.70 39.72 39.80
0.08 0.08 0.04 0.02 0.06
39.84 39.75 39.80 39.80 39.70
0.06 0.03 0.02 0.02 0.08
39.74
0.06
39.78
0.04
- ud2 M = ( n-l >
M
0.12
= 0.06
?4 = 0.05
a Microstandard sample from British Drug House, Poote, England. Theoretical 39.75% Br.
=
chlorine determination alone, the present shortcut procedure should be comparatively simpler than the A.O.A.C. procedure (9). Moreover in several common titration micromethods involving hydrogen peroxide absorption in the flask combustion, the removal of hydrogen peroxide is not necessary. Examples of this are: a. Barium titration for organosulfur determination as described by Alicino (I) or by Budisinsky and Krumlova (2), and/or Scrogglins (15). b. Argentimetric titration with specific-ion electrodes (bromide, chloride and iodide), but must be in an acidic medium (say pH 4-5). SUMMARY The mercurimetric method for organohalogen determination described in 1959 can be further simplified by omitting the boiling process for removal of hydrogen peroxide after combustion of the sample in the oxygen tlask. Hydrogen peroxide does not interfere in the mercurimetric titration. Its presence did show certain advantages in the work of other investigators as well as in this present study.
REFERENCES 1. Alicino, J. F., Determination of sulfur in organic compounds. Microchem. (1958).
J. 2, 83
128
F. W.
CHENG
2. Budesinsky, B., and Krumlova, L., Determination of sulfur and sulfate by titration with barium perchlorate. Anal. Chim. Actn 39 375-381 (1967). 3. Cheng, F. W., A rapid method for microdetermination of halogen in organic compound. Microchem. J. 3, 537-542 (1959). 4. Denney, R. D., and Smith, P. A., Comparison of two procedures for the determination of organobromine by the Schoeniger oxygen flask method. Analyst 99, 1176 (1974). 5. Frausto da Silva, J. J. R., Calado, J. G., and Legrand de Moura, M., Separation of commercial diphenylcarbazone into its compounds. Tu/nnra 11, 938-984 (1964). 6. Krumholz, P., and Krumholz, E., Diphenylcarbazone. Monafsh. Chem. 70, 341-346 (1937). 7. Lalancette, R. A., Lukaszewski, D. M., and Steyermark, A., Determination of iodine in organic compounds employing oxygen flask combustion and mercurimetric titration. Microchem. J. 17, 665-669 (1972). 8. Lalancette, R. A., Steyermark, A., Lukaszewski, D. M., and Kostrzewski, P. L., Collaborative study of the microanalytical determination of iodine by oxygen flask combustion. J. Ass. Offic. Anal. Chem. 56, 888-891 (1973). 9. Lalancette, R. A., and Steyermark, A., Collaborative study of the microanalytical determination of bromine and chlorine by oxygen flask combustion, J. Ass. Offic. Anal. Chem. 57, 26-28 (1974). 10. MacDonald, A. M. G., The oxygen llask method-A review. Analyst 86, 3-12 (1961). II. Ovsyankina, V. V., and Shashkova, M. L., Mercurimetric determination of small concentration of chloride and bromides. Zh. Vses. Khim. 14, 468 (1969). 12. &h&tiger, W., Eine mikroanalytishe Schnellbestimmung von Halogene in Organischem Substanzen. Mikrochim. Acta 123-129 (1955). 13. Steyermark, A., Microanalytical determination of bromine, chlorine, and iodine by oxygen flask combustion, J. Ass. Offic. Anal. Chem. 48, 709-717 (1965). 14. Steyermark, A., Lalancette, R. A., and Contreras, E. M., Collaborative study of microanalytical determination of bromine and chlorine by flask combustion. J. Ass. Offic. Anal. Chem. 55, 680-683 (1972). IS. Scrogglins, L. H., Collaborative Study of the microanalytical oxygen flask sulfur determination with dimethyl sulfonazo III as indicator. J. Ass. Offic. Anal. Chem. 57, 22 25 (1974). 16. William, G. J., and DeRanter, C. J., The purity of commercial diphenylcarbazone. Anal. Chim. Acta 68, 111 (1974).
JOURNAL
21, 125-128 (1976)
Simplification of the Mercurimetric Procedure for Organohalogen Determination F. W. ICI
United
Stutes
Inc.,
CHENC
Wilmington,
Delaware
19897
Received December 10, 1975
INTRODUCTION
In a 1959 issue of this journal, we reported a mercurimetric procedure for organohalogen determination (3). It consisted of: (a) oxygen llask combustion, (b) absorption of the combustion products in a dilute alkaline hydrogen peroxide solution, (c) boiling to eliminate hydrogen peroxide and (d) mercurimetric titration to determine the halogen content. This procedure was widely accepted and its reliability has been confirmed by several collaborative studies (13,14). A recent statistical comparison with other established methods also appeared to favor this method (4). However, as we have noted, the analytical time can be further reduced by about 50% if one eliminates the boiling step for the removal of hydrogen peroxide. In 1961, MacDonald (10) had suggested such a shortcut in a brief statement but her suggestion was generally overlooked. This note is an attempt to recall attention to this shortcut. METHOD
The revised mercurimetric procedure is essentially the same as described previously (3), but with the boiling step after combustion eliminated. Briefly, therefore, the procedure should read: Burn the sample (l-3 mg) as usual by the oxygen tlask combustion technique (12). Absorb the combustion products in 10 ml of 6% hydrogen peroxide solution and 1 ml 0.5 N potassium hydroxide solution. Shake thoroughly after combustion and let stand for 2-5 min for complete absorption. Rinse the flask with water. The combustion mixture is diluted with 2 parts of alcohol and is adjusted to pH value of 3.5 using dilute nitric acid with aid of 5 drops of bromophenol blue (0.05% alcoholic solution). The resulting solution is titrated with 0.01 N mercuric nitrate, using 0.5% diphenylcarbazone in alcohol as the indicator. Methods of preparing reagents were described in our previous publication (3). RESULTS AND DISCUSSION
The justification for omitting the boiling step follows from the comparison of results shown in Tables 1 and 2. In these tables, data under col125 Copyright0 1976by AcademicPress,Inc. All rightsof reproductionm any form reserved.
126
F. W.
CHENG
TABLE ANALYSIS
A (no hydrogen peroxide) data collected 1959 (3)
Acrnn
B (no hydrogen peroxide) current data
d
C (with hydrogen peroxide)
d
d
found
deviation from mean
Cl% found
deviation from mean
Cl% found
deviation from mean
22.51 22.68 22.65 22.81 22.56 22.60 22.60 22.63
0.12 0.05 0.02 0.18 0.07 0.03 0.03 0.07
22.36 22.24 22.30 22.40 22.40
0.02 0.10 0.04 0.06 0.06
22.71 22.59 22.60 22.75 22.75
0.03 0.09 0.08 0.07 0.07
22.34
0.06
22.68
0.07
Cl%
Mean
1
OF CHLOROBENZOIC
41= 0.09
M
= 0.08
a Microstandard sample from British Drug House, Poote, England. Theoretical: 22.65% Cl.
umns A and B were obtained by the procedure (3) where hydrogen peroxide was expelled. Data under column A were quoted from the previous report (3), while those under column B are current results. The data under column C were obtained by the revised procedure wherein the mercurimetric titration is conducted in the presence of hydrogen peroxide. The results are in good agreement, but the analytical time is shortened by 50% using the revised procedure. Most commercial diphenylcarbazone reagents are mixtures of diphenylcarbazide and diphenylcarbazone (5,6,16). Since diphenylcarbazone is usually prepared by partial oxidation of diphenylcarbazide with hydrogen peroxide, it follows that hydrogen peroxide would not alter the function of either when it is present during the mercurimetric titration. Therefore, the presence of hydrogen peroxide is not harmful, but beneficial in the mercurimetric titration. Some investigators deliberately titrate halide in the presence of hydrogen peroxide to enhance the end-point (11). The boiling step to remove hydrogen peroxide in the original procedure is a disadvantage for organoiodine determination. Omission of this step could improve iodine analysis. Recently an iodine procedure devised by Lalancette et al. (7) had reported achieving excellent results. These were also conhrmed by collaborative studies (8,9). However, for bromine or
ORGANOHALOGEN
127
DETERMINATION
TABLE 2 ANALYSIS
A (no hydrogen peroxide) data collected 1959 (3)
OF BROMOBENZOIC
B (no hydrogen peroxide) current data
d
Mean s=
ACID”
C (presence of hydrogen peroxide) d
d
Br % found
deviation from mean
Br % found
deviation from mean
Br T found
deviation from mean
39.96 39.97 39.12 39.89 39.93 39.61 39.70 39.74 39.80 39.81
0.15 0.16 0.09 0.03 0.12 0.20 0.11 0.07 0.01 0.10
39.66 39.82 39.70 39.72 39.80
0.08 0.08 0.04 0.02 0.06
39.84 39.75 39.80 39.80 39.70
0.06 0.03 0.02 0.02 0.08
39.74
0.06
39.78
0.04
- ud2 M = ( n-l >
M
0.12
= 0.06
?4 = 0.05
a Microstandard sample from British Drug House, Poote, England. Theoretical 39.75% Br.
=
chlorine determination alone, the present shortcut procedure should be comparatively simpler than the A.O.A.C. procedure (9). Moreover in several common titration micromethods involving hydrogen peroxide absorption in the flask combustion, the removal of hydrogen peroxide is not necessary. Examples of this are: a. Barium titration for organosulfur determination as described by Alicino (I) or by Budisinsky and Krumlova (2), and/or Scrogglins (15). b. Argentimetric titration with specific-ion electrodes (bromide, chloride and iodide), but must be in an acidic medium (say pH 4-5). SUMMARY The mercurimetric method for organohalogen determination described in 1959 can be further simplified by omitting the boiling process for removal of hydrogen peroxide after combustion of the sample in the oxygen tlask. Hydrogen peroxide does not interfere in the mercurimetric titration. Its presence did show certain advantages in the work of other investigators as well as in this present study.
REFERENCES 1. Alicino, J. F., Determination of sulfur in organic compounds. Microchem. (1958).
J. 2, 83
128
F. W.
CHENG
2. Budesinsky, B., and Krumlova, L., Determination of sulfur and sulfate by titration with barium perchlorate. Anal. Chim. Actn 39 375-381 (1967). 3. Cheng, F. W., A rapid method for microdetermination of halogen in organic compound. Microchem. J. 3, 537-542 (1959). 4. Denney, R. D., and Smith, P. A., Comparison of two procedures for the determination of organobromine by the Schoeniger oxygen flask method. Analyst 99, 1176 (1974). 5. Frausto da Silva, J. J. R., Calado, J. G., and Legrand de Moura, M., Separation of commercial diphenylcarbazone into its compounds. Tu/nnra 11, 938-984 (1964). 6. Krumholz, P., and Krumholz, E., Diphenylcarbazone. Monafsh. Chem. 70, 341-346 (1937). 7. Lalancette, R. A., Lukaszewski, D. M., and Steyermark, A., Determination of iodine in organic compounds employing oxygen flask combustion and mercurimetric titration. Microchem. J. 17, 665-669 (1972). 8. Lalancette, R. A., Steyermark, A., Lukaszewski, D. M., and Kostrzewski, P. L., Collaborative study of the microanalytical determination of iodine by oxygen flask combustion. J. Ass. Offic. Anal. Chem. 56, 888-891 (1973). 9. Lalancette, R. A., and Steyermark, A., Collaborative study of the microanalytical determination of bromine and chlorine by oxygen flask combustion, J. Ass. Offic. Anal. Chem. 57, 26-28 (1974). 10. MacDonald, A. M. G., The oxygen llask method-A review. Analyst 86, 3-12 (1961). II. Ovsyankina, V. V., and Shashkova, M. L., Mercurimetric determination of small concentration of chloride and bromides. Zh. Vses. Khim. 14, 468 (1969). 12. &h&tiger, W., Eine mikroanalytishe Schnellbestimmung von Halogene in Organischem Substanzen. Mikrochim. Acta 123-129 (1955). 13. Steyermark, A., Microanalytical determination of bromine, chlorine, and iodine by oxygen flask combustion, J. Ass. Offic. Anal. Chem. 48, 709-717 (1965). 14. Steyermark, A., Lalancette, R. A., and Contreras, E. M., Collaborative study of microanalytical determination of bromine and chlorine by flask combustion. J. Ass. Offic. Anal. Chem. 55, 680-683 (1972). IS. Scrogglins, L. H., Collaborative Study of the microanalytical oxygen flask sulfur determination with dimethyl sulfonazo III as indicator. J. Ass. Offic. Anal. Chem. 57, 22 25 (1974). 16. William, G. J., and DeRanter, C. J., The purity of commercial diphenylcarbazone. Anal. Chim. Acta 68, 111 (1974).