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Spectrophotometric study of bismuth with N-(2-acetamido)iminodiacetic acid (ADA): Determination of bismuth in pharmaceutical formulations
MICROCHEMICAL
JOURNAL
31, 368-374 (1985)
Spectrophotometric Study of Bismuth with N-(2-Acetamido)iminodiacetic Acid (ADA): Determination of Bismuth in Pharmaceutical Formulations’ AURORAGONZALEZ-PORTAL,
F. BERMEJO-MARTINEZ,
AND MARIA Department
CRISTINA
C.
BALUJA-SANTOS,
DIEZ-RODRIGUEZ
of Analytical
Chemistry, Faculty of Chemistry, Santiago de Compostela, Spain
University,
Received March 16, 1983 A new method for the spectrophotometric determination of bismuth using N-(2-acetamido)iminodiacetic acid as complexometric agent is proposed. The complex is formed in a wide pH range, 5.5-7.5, and has a maximum absorption at 265 nm. Beer’s law is obeyed in the interval 3.8-17.9 ug of bismuth(III)/ml, with a minimum photometric error of 2.3. The molar absorptivity is 9.1 x lo3 liters/cm mol. The stoichiometry of the reaction takes place in the metal-to-ligand ratio 1:2. The interferences produced by the more common ions are studied. The method has been successfully applied to the determination of bismuth in pharmaceutical formulations. 0 1985 Academic press, IIIC.
INTRODUCTION
Bismuth forms a series of salts derived from BiO+ and Bi3+ ions. BiO+ salts are generally insoluble in water and the Bi3+ salts have a strong tendency to form covalent bonds with polarizable ligands such as those containing sulfur and nitrogen. Ligands such as aminopolycarboxylic acid (NTA) (4) and (EDTA) (IO), containing oxygen, form complexes that are very useful in analytical chemistry. The Bi(III)-HEEDTA complex in the presence of perchloric acid has been utilized for the determination of 2 to 36 kg/ml with an error of less than 10% (5). Bismuth can also be determined by use of the Bi(III)-DTPA complex (2, 8). Springer et al. (9) have utilized EDDPA as a chelating agent to determine bismuth. The complex shows an absorption maximum at 245 nm and pH between 1.6 and 3.3. The complex Bi(III)-TTHA in perchloric acid has been studied by Kuncheva et al. (6). The N-(2-acetamido)iminodiacetic acid CH, - COOH H,N-CO-CH,-N’ ‘CH, - COOH (short form ADA-H,) is the monoamide of nitrilotriacetic ’ part CXVII in the series “Analytical
Applications of the Chelons.” 368
0026-265X185$1.50 Copyright AU rights
0 1985 by Academic Press, Inc. of reproduction in any form reserved.
acid and it is used as a
SPECTROPHOTOMETRY
OF Bi
369
pH regulator between 6 and 8 units in biological environments and together with other compounds it is known by the name of “Good’s” buffers. The ADA-H, has nitrogen and oxygen groups and will form complexes of intermediate type with the Bi3+ ion. Nakon (7) propose several structures for some of these complexes. In the present paper the bismuth(III)-ADA complex is studied and a new method for the photometric determination of this metal is applied to several pharmaceutical formulations. EXPERIMENTAL Reagents Bismuth(ZZZ) chloride standard solution was prepared from B&O, in HCl; its concentration was determined volumetrically and had a value of 0.02454 M. From this solution others were prepared by dilution. N-(2-Acetamido)iminodiacetic acid standard solution. An aqueous solution was prepared by dissolving the appropriate amount of reagent in distilled water with the aid of sodium hydroxide to achieve its complex dissolution; its concentration was determined volumetrically and had a value of 0.2454 M. From this solution others were prepared by dilution. N-(2-Acetamido)iminodiacetic acid (ADA) solution. A 0.05% aqueous solution was prepared by dissolving the appropriate amount of reagent in distilled water with the aid of sodium hydroxide. Sodium hydroxide aqueous solution, Hydrochloric acid aqueous solution,
0.1 M. 0.1 M.
Apparatus
A Bausch & Lomb Spectronic 700 spectrophotometer with l-cm-thick quartz cells and a Beckman Electromate pH meter with a sensibility of 0.02 were used. Absorption
Spectra
In order to set the optimum working wavelength, the spectral characteristics of the bismuth-ADA system at various pH values were studied according to the following procedure. Aliquots of the standard bismuth solution were placed in IO-ml volumetric flasks to which were added 2 ml of ADA-H, solution at 0.05% and solutions of HCl or OHNa to obtain different pH values, and finally diluted with distilled water to the mark and mixed. Absorbance was read in the spectrophotometer with quartz cells of l-cm light path using a solution with the same amounts of reagents as the blank. In Fig. 1 are shown the results obtained at pH 4.7 and 11.2, from which the identity of the spectra is determined at the given pH values, exhibiting a maximum at 265 nm. pH Effect
Absorbance was found to be constant in the pH interval 5.5-7.5. Figure 2 illustrates the results obtained when using a bismuth concentration of 10.2 pg/ ml; thus a pH of about 6.8 was chosen for further studies.
370
GONZALEZ-PORTAL
L
, 230
250
ET AL.
270
290
h (nm)
FIG. I. Absorption spectrum of Bi(III)-ADA pH 7.0 (-.-.), and pH 11.2 (---).
complex with 10.2 pg of Bi(III)/ml at pH 4.0 (-),
Effect of Amount of Reagent The influence of the amount of reagent on the formation of bismuth(U)-ADA complex was studied. It was found that 0.7 ml of 0.05% ADA-H, solution for every 10.2 pg of Bi(III)/ml was sufficient to form the complex and further additions of reagent did not appreciably effect the absorbance of the system. Time and Temperature Effects The effects of time and temperature on the stability of the system bismuth(III)ADA were also studied with the conclusion that the complex is formed instantaneously and its absorbance remains unchanged for up to 8 hr and up to 100°C. Beer’s Law, Molar Absorptivity, and Sensitivity The relationship between absorbance radiant energy and complex concentration was studied under the previously established conditions. Several solutions of bismuth(III)-ADA complex were prepared by taking aliquots of the standard solution of bismuth and, after adding the reagent and adjusting the pH, diluting with distilled water up to the mark. The absorbance of the solution was measured at 265 nm; the results are linear on the calibration graph over the range 3.8- 17.9 pg bismuth(III)/ml. The molar absorptivity was calculated as 9.1 x IO3 liters/ cm * mol. The sensibility according to Sandell’s expression was 0.023 kg/cm*.
L,
1
,
,
3
5
7
9
11
19
P"
FIG. 2. The dependence of the absorbance of the Bi(Ill)-ADA tion 10.2 pg/ml.
complex on pH. Bi(III) concentra-
SPECTROPHOTOMETRY
OF Bi
371
so-
z ; 70. B :: . m 4 6 50. >.
30-
0:5
1 ;s
1 :o L0g.c
FIG. 3. Ringbom’s plots for bismuth(III)-ADA
Ringbom’s
Interval
and Photometric
complex. pH 6.8
Error
The optimal interval of Beer’s law application was studied (Fig. 3) and is 5. l15.4 pg Bi(III)/ml. The minimum photometric error is 2.3%. Reproducibility
and Precision
To carry out these studies four series of solutions with different concentrations were prepared according to the previously described procedure. The reproducibility is good; the standard deviation is about 1% for the range 0.254-0.579 absorbance unit. Stoichiometry of the Reaction The composition of the complex bismuth(III)-ADA was studied using the “molar ratio” method of Yoe and Jones (II) and the “continuous variations” method of Job (3). The results are illustrated in Figs. 4 and 5, from which it is deduced that the formation of the complex takes place at a bismuth(II1) to ADA-H, ratio of 1:2.
0.5
/
-.
d uz 0.3
i
5: m 4
3
0.1 /j--
123456 [ADA]/[8illll]
FIG. 4. Determination pH 6.8.
of composition of bismuth(III)-ADA
complex by the Yoe and Jones method.
372
GONZALEZ-PORTAL
0:2 [Bi(lll)]
'd.4
6.6
ET AL.
0:B
I'.0
/[BiOll)]+[ADA]
FIG. 5. Determination of composition of bismuth(III)-ADA
complex by Job’s method. pH 6.8.
Effect of Diverse Ions Various amounts of foreign ions were added to solutions containing 10.2 pg Bi(III)/ml and the recommended procedures were followed: SO-fold amounts of chloride, bromide, chromate, dichromate, chlorate, perchlorate, thiosulfate, lead(II), zinc(II), cadmium(II), nickel(II), cobalt(II), aluminum(III), and lithium, and IO-fold amounts of nitrate, nitrite, acetate, arsenate, manganese(I1); at a 5fold excess, oxalate, tartrate, copper( chromate, and iron(I1) do not interfere in the bismuth determination. Application of the Method to the Determination of Bismuth in Pharmaceutical Formulations Bismuth and its derivatives occupy a very important place in pharmacology due to the variety and interest of their applications. They are used as local protectors of the mucous membrane of the digestive system, and as antisyphilitic agents-similar to antimony and arsenic-they consolidate the action of penicillin. The proposed method is applied to the determination of bismuth in the following SUALYN digestive regulators from VITA Laboratories: (A) a colloidal suspension of bismuth subnitrate smaller than a micrometer corresponding to 79% B&O, mixed with metachlopramide chlorydrate, magnesium carbonate, and sorbitol; TABLE 1 Determination of Bismuth in Pharmaceutical Formulations Bismuth (ppm) Found
Sample
Taken
Volumetric method (n = 3)
Colloidal suspension Tablets
10.6 12.8
10.1 * 0.1 12.5 +- 0.1
This method (n = 5)
Mean recovery (%I
9.9 k 0.1 12.3 * 0.1
93.4 96.0
SPECTROPHOTOMETRY
373
OF Bi
TABLE 2 Study of the Determination of Bismuth with Metal Chelates of Some Aminopolycarboxylic Chelon
Log K
NTA EDTA DCTA DTPA EEDTA HEDTA HEEDTA EDDPA TTHA ADA-H,
22.80 23.19 29.77 23.77 21.85 -
-
A (nm)
243 263.5 267 277 270 260 260 245 280 265
E
PH 1.0 0.8-1.2 b b b b b
1.6-3.3 b
5.5-7.5
(liters cm-’ mol-‘) 8000 9350 8700 8900 8180 8160 9100
Beer’s law hdml) 2-25 2-36 0.3-16.0 l-40 3.8-17.9
Acids” Ref.
(4) (10) (8) (2, 8) (8)
(5) (8) (9)
(6) Present paw
a The acronyms for the chelons are taken from “Chelates in Analytical Chemistry,” Vol. 5, p. 34, Dekker, New York, 1976. b Acid pH.
(B) tablets of bismuth polyuronate, about 1.50 g, each containing 0.125 g of polyuronate equivalent to 50% B&O, and metachlopramide base, magnesium oxide, and unspecified excipients. Procedure
Samples (0.5 ml or 0.5 g) of A and B are placed in a Kjeldahl flask. The mixture is treated with the appropriate amount of hydrogen peroxide, and then drops of chlorhydric acid (for A) and perchloride acid (for B) are added until oxidation is complete and the solution is completely transparent. Then it is cooled to room temperature and placed in a volumetric flask completing the volume with distilled water. An aliquot of this solution is placed in a 25ml volumetric flask so as to reach a tinal concentration of between 3.8 and 17.9 pg of Bi/ml and the general procedure already described is followed. The bismuth content of the samples was also determined volumetrically (I) by using a standard method. The results obtained for several samples of pharmaceutical produces are shown in Table 1. In order to show the accuracy of the method employed aliquots of both samples are taken and aliquots of the standard solution of bismuth(II1) are added so that the final concentration is kept within the limits required by the method. The obtained results, shown in Table 2, indicate that the recoveries are between 93.4 and 96.0%. CONCLUSIONS
Several aminopolycarboxylic acids have been proposed as reagents for the determination of bismuth(II1) in the ultraviolet. The spectrophotometric properties of the main chelons used to determine such cations are summarized in Table 2. The results obtained emphasize the high molar absorptivity and pH range of the bismuth(III)-ADA complex. All chelons form a complex with bismuth in the ratio 1: 1 but the ratio composition of the bismuth-ADA complex is 1:2.
374
GONZALEZ-PORTAL
ET AL.
REFERENCES 1. Bermejo-Martinez,
2. 3. 4. 5. 6. 7. 8. 9. JO. JJ.
F., and Prieto-Bouza, A., “Aplicaciones Analiticas de1 AEDT y Similares,” 2nd ed., p. 294. Imprenta de1 Seminario Conciliar, Santiago de Compostela, 1975. Edgaonkar, P S., Atchayya, M., and Subbaraman, P. R., Spectrophotometric estimation of bismuth(II1) and lead(I1) with diethylenetriaminepentaacetic acid. Indian J. Chem. 13, 400-402 (1975). Job, P., Formation and stability of inorganic complexes in solution. Ann. Chim. 9, 113 (1928). Karadakov, B. P., and Venkova, D. I., The complexes of bismuth(II1) and nitrilotriacetic acid. Tulanta 17, 878-883 (1970). Karadakov, B. P., Nenova, P. P., and Ivanova, K. R., Spectrophotometric study of the complexes of hydroxyethylenediaminetriacetic acid with bismuth(III), copper(B), and lead(I1). Zh. Anal. Khim. 31, 2058-2061 (1976). Kuncheva, D., Nenova, P., and Karadakov, B., Spectrophotometric study of bismuth with triethylenetetraminehexaacetic acid. Dokl. Bolg. Akud. Nauk 32, 651-654 (1979). Nakon R., “Free metal ion depletion by Good’s buffers. I. N-(2-Acetamido)iminodiacetic acid 1:l complexes with Ca(II), Mg(II), Zn(II), Mn(II), Co(II), Ni(II), and Cu(I1). Anal. Biochem. 95, 527-532 (1979). Nozaki, T., and Koshiba, K., Determination of the composition and formation of constants of aminopolycarboxylate complexes of bismuth by ultraviolet spectrophotometry. J. Chem. Sot. Jpn. Pure Chem. Sect. 88, 1287-1291 (1967). Springer, V., Turan, J., and Kopecka, B., Complex of bismuth(II1) with ethylenediamine-N,N’2,2’-di(3-hydroxypropionic) acid. Farm. Ubz. 45, 15-23 (1976). West, P. W., and Coll, H., Spectrophotometric determination of bismuth with ethylenediaminetetraacetic acid. Anal. Chem. 27, 1221-1224 (1955). Yoe, J. H., and Jones, A. L., “Calorimetric determination of iron with disodium 1,2-dihydroxybenzene 3,5-disulfonate. Znd. Eng. Chem. Anal. Ed. 16, 11l- 115 (1944).
JOURNAL
31, 368-374 (1985)
Spectrophotometric Study of Bismuth with N-(2-Acetamido)iminodiacetic Acid (ADA): Determination of Bismuth in Pharmaceutical Formulations’ AURORAGONZALEZ-PORTAL,
F. BERMEJO-MARTINEZ,
AND MARIA Department
CRISTINA
C.
BALUJA-SANTOS,
DIEZ-RODRIGUEZ
of Analytical
Chemistry, Faculty of Chemistry, Santiago de Compostela, Spain
University,
Received March 16, 1983 A new method for the spectrophotometric determination of bismuth using N-(2-acetamido)iminodiacetic acid as complexometric agent is proposed. The complex is formed in a wide pH range, 5.5-7.5, and has a maximum absorption at 265 nm. Beer’s law is obeyed in the interval 3.8-17.9 ug of bismuth(III)/ml, with a minimum photometric error of 2.3. The molar absorptivity is 9.1 x lo3 liters/cm mol. The stoichiometry of the reaction takes place in the metal-to-ligand ratio 1:2. The interferences produced by the more common ions are studied. The method has been successfully applied to the determination of bismuth in pharmaceutical formulations. 0 1985 Academic press, IIIC.
INTRODUCTION
Bismuth forms a series of salts derived from BiO+ and Bi3+ ions. BiO+ salts are generally insoluble in water and the Bi3+ salts have a strong tendency to form covalent bonds with polarizable ligands such as those containing sulfur and nitrogen. Ligands such as aminopolycarboxylic acid (NTA) (4) and (EDTA) (IO), containing oxygen, form complexes that are very useful in analytical chemistry. The Bi(III)-HEEDTA complex in the presence of perchloric acid has been utilized for the determination of 2 to 36 kg/ml with an error of less than 10% (5). Bismuth can also be determined by use of the Bi(III)-DTPA complex (2, 8). Springer et al. (9) have utilized EDDPA as a chelating agent to determine bismuth. The complex shows an absorption maximum at 245 nm and pH between 1.6 and 3.3. The complex Bi(III)-TTHA in perchloric acid has been studied by Kuncheva et al. (6). The N-(2-acetamido)iminodiacetic acid CH, - COOH H,N-CO-CH,-N’ ‘CH, - COOH (short form ADA-H,) is the monoamide of nitrilotriacetic ’ part CXVII in the series “Analytical
Applications of the Chelons.” 368
0026-265X185$1.50 Copyright AU rights
0 1985 by Academic Press, Inc. of reproduction in any form reserved.
acid and it is used as a
SPECTROPHOTOMETRY
OF Bi
369
pH regulator between 6 and 8 units in biological environments and together with other compounds it is known by the name of “Good’s” buffers. The ADA-H, has nitrogen and oxygen groups and will form complexes of intermediate type with the Bi3+ ion. Nakon (7) propose several structures for some of these complexes. In the present paper the bismuth(III)-ADA complex is studied and a new method for the photometric determination of this metal is applied to several pharmaceutical formulations. EXPERIMENTAL Reagents Bismuth(ZZZ) chloride standard solution was prepared from B&O, in HCl; its concentration was determined volumetrically and had a value of 0.02454 M. From this solution others were prepared by dilution. N-(2-Acetamido)iminodiacetic acid standard solution. An aqueous solution was prepared by dissolving the appropriate amount of reagent in distilled water with the aid of sodium hydroxide to achieve its complex dissolution; its concentration was determined volumetrically and had a value of 0.2454 M. From this solution others were prepared by dilution. N-(2-Acetamido)iminodiacetic acid (ADA) solution. A 0.05% aqueous solution was prepared by dissolving the appropriate amount of reagent in distilled water with the aid of sodium hydroxide. Sodium hydroxide aqueous solution, Hydrochloric acid aqueous solution,
0.1 M. 0.1 M.
Apparatus
A Bausch & Lomb Spectronic 700 spectrophotometer with l-cm-thick quartz cells and a Beckman Electromate pH meter with a sensibility of 0.02 were used. Absorption
Spectra
In order to set the optimum working wavelength, the spectral characteristics of the bismuth-ADA system at various pH values were studied according to the following procedure. Aliquots of the standard bismuth solution were placed in IO-ml volumetric flasks to which were added 2 ml of ADA-H, solution at 0.05% and solutions of HCl or OHNa to obtain different pH values, and finally diluted with distilled water to the mark and mixed. Absorbance was read in the spectrophotometer with quartz cells of l-cm light path using a solution with the same amounts of reagents as the blank. In Fig. 1 are shown the results obtained at pH 4.7 and 11.2, from which the identity of the spectra is determined at the given pH values, exhibiting a maximum at 265 nm. pH Effect
Absorbance was found to be constant in the pH interval 5.5-7.5. Figure 2 illustrates the results obtained when using a bismuth concentration of 10.2 pg/ ml; thus a pH of about 6.8 was chosen for further studies.
370
GONZALEZ-PORTAL
L
, 230
250
ET AL.
270
290
h (nm)
FIG. I. Absorption spectrum of Bi(III)-ADA pH 7.0 (-.-.), and pH 11.2 (---).
complex with 10.2 pg of Bi(III)/ml at pH 4.0 (-),
Effect of Amount of Reagent The influence of the amount of reagent on the formation of bismuth(U)-ADA complex was studied. It was found that 0.7 ml of 0.05% ADA-H, solution for every 10.2 pg of Bi(III)/ml was sufficient to form the complex and further additions of reagent did not appreciably effect the absorbance of the system. Time and Temperature Effects The effects of time and temperature on the stability of the system bismuth(III)ADA were also studied with the conclusion that the complex is formed instantaneously and its absorbance remains unchanged for up to 8 hr and up to 100°C. Beer’s Law, Molar Absorptivity, and Sensitivity The relationship between absorbance radiant energy and complex concentration was studied under the previously established conditions. Several solutions of bismuth(III)-ADA complex were prepared by taking aliquots of the standard solution of bismuth and, after adding the reagent and adjusting the pH, diluting with distilled water up to the mark. The absorbance of the solution was measured at 265 nm; the results are linear on the calibration graph over the range 3.8- 17.9 pg bismuth(III)/ml. The molar absorptivity was calculated as 9.1 x IO3 liters/ cm * mol. The sensibility according to Sandell’s expression was 0.023 kg/cm*.
L,
1
,
,
3
5
7
9
11
19
P"
FIG. 2. The dependence of the absorbance of the Bi(Ill)-ADA tion 10.2 pg/ml.
complex on pH. Bi(III) concentra-
SPECTROPHOTOMETRY
OF Bi
371
so-
z ; 70. B :: . m 4 6 50. >.
30-
0:5
1 ;s
1 :o L0g.c
FIG. 3. Ringbom’s plots for bismuth(III)-ADA
Ringbom’s
Interval
and Photometric
complex. pH 6.8
Error
The optimal interval of Beer’s law application was studied (Fig. 3) and is 5. l15.4 pg Bi(III)/ml. The minimum photometric error is 2.3%. Reproducibility
and Precision
To carry out these studies four series of solutions with different concentrations were prepared according to the previously described procedure. The reproducibility is good; the standard deviation is about 1% for the range 0.254-0.579 absorbance unit. Stoichiometry of the Reaction The composition of the complex bismuth(III)-ADA was studied using the “molar ratio” method of Yoe and Jones (II) and the “continuous variations” method of Job (3). The results are illustrated in Figs. 4 and 5, from which it is deduced that the formation of the complex takes place at a bismuth(II1) to ADA-H, ratio of 1:2.
0.5
/
-.
d uz 0.3
i
5: m 4
3
0.1 /j--
123456 [ADA]/[8illll]
FIG. 4. Determination pH 6.8.
of composition of bismuth(III)-ADA
complex by the Yoe and Jones method.
372
GONZALEZ-PORTAL
0:2 [Bi(lll)]
'd.4
6.6
ET AL.
0:B
I'.0
/[BiOll)]+[ADA]
FIG. 5. Determination of composition of bismuth(III)-ADA
complex by Job’s method. pH 6.8.
Effect of Diverse Ions Various amounts of foreign ions were added to solutions containing 10.2 pg Bi(III)/ml and the recommended procedures were followed: SO-fold amounts of chloride, bromide, chromate, dichromate, chlorate, perchlorate, thiosulfate, lead(II), zinc(II), cadmium(II), nickel(II), cobalt(II), aluminum(III), and lithium, and IO-fold amounts of nitrate, nitrite, acetate, arsenate, manganese(I1); at a 5fold excess, oxalate, tartrate, copper( chromate, and iron(I1) do not interfere in the bismuth determination. Application of the Method to the Determination of Bismuth in Pharmaceutical Formulations Bismuth and its derivatives occupy a very important place in pharmacology due to the variety and interest of their applications. They are used as local protectors of the mucous membrane of the digestive system, and as antisyphilitic agents-similar to antimony and arsenic-they consolidate the action of penicillin. The proposed method is applied to the determination of bismuth in the following SUALYN digestive regulators from VITA Laboratories: (A) a colloidal suspension of bismuth subnitrate smaller than a micrometer corresponding to 79% B&O, mixed with metachlopramide chlorydrate, magnesium carbonate, and sorbitol; TABLE 1 Determination of Bismuth in Pharmaceutical Formulations Bismuth (ppm) Found
Sample
Taken
Volumetric method (n = 3)
Colloidal suspension Tablets
10.6 12.8
10.1 * 0.1 12.5 +- 0.1
This method (n = 5)
Mean recovery (%I
9.9 k 0.1 12.3 * 0.1
93.4 96.0
SPECTROPHOTOMETRY
373
OF Bi
TABLE 2 Study of the Determination of Bismuth with Metal Chelates of Some Aminopolycarboxylic Chelon
Log K
NTA EDTA DCTA DTPA EEDTA HEDTA HEEDTA EDDPA TTHA ADA-H,
22.80 23.19 29.77 23.77 21.85 -
-
A (nm)
243 263.5 267 277 270 260 260 245 280 265
E
PH 1.0 0.8-1.2 b b b b b
1.6-3.3 b
5.5-7.5
(liters cm-’ mol-‘) 8000 9350 8700 8900 8180 8160 9100
Beer’s law hdml) 2-25 2-36 0.3-16.0 l-40 3.8-17.9
Acids” Ref.
(4) (10) (8) (2, 8) (8)
(5) (8) (9)
(6) Present paw
a The acronyms for the chelons are taken from “Chelates in Analytical Chemistry,” Vol. 5, p. 34, Dekker, New York, 1976. b Acid pH.
(B) tablets of bismuth polyuronate, about 1.50 g, each containing 0.125 g of polyuronate equivalent to 50% B&O, and metachlopramide base, magnesium oxide, and unspecified excipients. Procedure
Samples (0.5 ml or 0.5 g) of A and B are placed in a Kjeldahl flask. The mixture is treated with the appropriate amount of hydrogen peroxide, and then drops of chlorhydric acid (for A) and perchloride acid (for B) are added until oxidation is complete and the solution is completely transparent. Then it is cooled to room temperature and placed in a volumetric flask completing the volume with distilled water. An aliquot of this solution is placed in a 25ml volumetric flask so as to reach a tinal concentration of between 3.8 and 17.9 pg of Bi/ml and the general procedure already described is followed. The bismuth content of the samples was also determined volumetrically (I) by using a standard method. The results obtained for several samples of pharmaceutical produces are shown in Table 1. In order to show the accuracy of the method employed aliquots of both samples are taken and aliquots of the standard solution of bismuth(II1) are added so that the final concentration is kept within the limits required by the method. The obtained results, shown in Table 2, indicate that the recoveries are between 93.4 and 96.0%. CONCLUSIONS
Several aminopolycarboxylic acids have been proposed as reagents for the determination of bismuth(II1) in the ultraviolet. The spectrophotometric properties of the main chelons used to determine such cations are summarized in Table 2. The results obtained emphasize the high molar absorptivity and pH range of the bismuth(III)-ADA complex. All chelons form a complex with bismuth in the ratio 1: 1 but the ratio composition of the bismuth-ADA complex is 1:2.
374
GONZALEZ-PORTAL
ET AL.
REFERENCES 1. Bermejo-Martinez,
2. 3. 4. 5. 6. 7. 8. 9. JO. JJ.
F., and Prieto-Bouza, A., “Aplicaciones Analiticas de1 AEDT y Similares,” 2nd ed., p. 294. Imprenta de1 Seminario Conciliar, Santiago de Compostela, 1975. Edgaonkar, P S., Atchayya, M., and Subbaraman, P. R., Spectrophotometric estimation of bismuth(II1) and lead(I1) with diethylenetriaminepentaacetic acid. Indian J. Chem. 13, 400-402 (1975). Job, P., Formation and stability of inorganic complexes in solution. Ann. Chim. 9, 113 (1928). Karadakov, B. P., and Venkova, D. I., The complexes of bismuth(II1) and nitrilotriacetic acid. Tulanta 17, 878-883 (1970). Karadakov, B. P., Nenova, P. P., and Ivanova, K. R., Spectrophotometric study of the complexes of hydroxyethylenediaminetriacetic acid with bismuth(III), copper(B), and lead(I1). Zh. Anal. Khim. 31, 2058-2061 (1976). Kuncheva, D., Nenova, P., and Karadakov, B., Spectrophotometric study of bismuth with triethylenetetraminehexaacetic acid. Dokl. Bolg. Akud. Nauk 32, 651-654 (1979). Nakon R., “Free metal ion depletion by Good’s buffers. I. N-(2-Acetamido)iminodiacetic acid 1:l complexes with Ca(II), Mg(II), Zn(II), Mn(II), Co(II), Ni(II), and Cu(I1). Anal. Biochem. 95, 527-532 (1979). Nozaki, T., and Koshiba, K., Determination of the composition and formation of constants of aminopolycarboxylate complexes of bismuth by ultraviolet spectrophotometry. J. Chem. Sot. Jpn. Pure Chem. Sect. 88, 1287-1291 (1967). Springer, V., Turan, J., and Kopecka, B., Complex of bismuth(II1) with ethylenediamine-N,N’2,2’-di(3-hydroxypropionic) acid. Farm. Ubz. 45, 15-23 (1976). West, P. W., and Coll, H., Spectrophotometric determination of bismuth with ethylenediaminetetraacetic acid. Anal. Chem. 27, 1221-1224 (1955). Yoe, J. H., and Jones, A. L., “Calorimetric determination of iron with disodium 1,2-dihydroxybenzene 3,5-disulfonate. Znd. Eng. Chem. Anal. Ed. 16, 11l- 115 (1944).