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Spectrophotometric determination of vitamin C using the copper(II)-nioxime-ascorbic acid system following stabilization in a propylene glycol medium
MICROCHEMICAL
JOURNAL
4,
109-l
14 (1989)
Spectrophotometric Determination of Vitamin C Using the Copper(H)-Nioxime-Ascorbic Acid System following Stabilization in a Propylene Glycol Medium M. BARBAS PARDILLO, V. PERIS MARTINEZ,’ J. V. GIMENO ADELANTADO, AND F. BOSCH REIG Department of .Analytical Chemistry, Faculty of Chemistry, University of Valencia, Dr. Moliner 50, 46100 Butjassot, Valencia, Spain A spectrophotometric method for the determination of Vitamin C is proposed. The procedure is based on formation and stabilization of the ternary complex Cu(II)nioxime-ascorbic acid in 80% (v/v) propylene glycol-water medium. The method has a high degree of tolerance for the determination of ascorbic acid in the presence of other active substances or excipients likely to be present along with vitamin C in pharmaceutical formulations. The suggested method has proved to be rapid and precise and has been successfully applied to different commercial pharmaceutical preparations of vitamin C. Precision, measured on the relative standard deviation, did not exceed 0.73%. 8 1989 Academic press, IW.
INTRODUCTION
Ascorbic acid is essential in the human body, for the formation of collagen and intercellular material. It also influences the formation of hemoglobin and the maturation of erythrocytes. Pharmacological interest in this substance is centered on the prevention and treatment of scurvy. It has also been employed as a diuretic, as a detoxifying agent in drug poisoning, and in treatment of numerous unrelated diseases (1). Although stable in air when dry, vitamin C suffers from a lack of stability in impure preparations, in many natural products, and in solution. The vitamin oxidizes rapidly on exposure to air or light. This is the main difficulty in the determination of ascorbic acid. Oxidation by the action of atmospheric oxygen is catalyzed by several metallic cations (2-9, enzymes such as oxidase (2), and UV light (6). This catalytic oxidation is also influenced by the pH of the medium, temperature (2), and concentration, with the most concentrated solutions being the most stable (2, 4). In addition to catalytic oxidation, bacteriologic decomposition must also be considered an important interference; this action decreases with temperature (4). Several methods for the stabilization of ascorbic acid have been proposed (710). Among the numerous spectrophotometric methods cited in the references (12), the most outstanding include, with Fe(CN),3- as oxidant reagent (22), formation of Prussian blue in the presence of Fe(II1) (23, 14), formation of molyb’ To whom correspondence should be addressed. 109 0026-265x/89 $1.50 Copyright 0 1989 by Academic Press, Inc. All rights of reproduction in any form reserved.
110
BARBAS
PARDILLO
ET AL.
denum blue with ammonium molybdate as reagent (Z5), or colored complexes after reduction of Fe(II1) with ascorbic acid (16, 27). Several reagents have been used for the direct or indirect determination of vitamin C such as 2,6-dichloroindophenol (28, 29), 2,4-dinitrophenylhydrazine (20), dimethoxyquinone (21), dimethoxydiquinone (22), 4nitrobenzenediazonium fluoborate (2.?), 2,3,5triphenyltetrazolium chloride (24), and phenylhydrazinium chloride (25). The following methods have also been used: the degradation reaction with Cu(I1) and forward complexation with neocuprina (26); and the decomposition of the complex Fe(III)-resacetophenone oxime and oxidants such as electrolytic Au(II1) (27). Most of the spectrophotometric methods based on the redox reaction between ascorbic acid and some other reagent show the lack of selectivity of the redox process. In the present work the spectrophotometric determination of vitamin C based on measurement of the color intensity of the ternary complex with Cu(I1) and nioxime (28) is proposed. It must be adequately stabilized in order to obtain the greater reliability and security of the proposed method. Several stabilizing agents and aquoorganic media were previously used by other authors in order to obtain a successful procedure to stabilize ascorbic acid and its solution. The present study has allowed us to choose the best medium for the stabilization of the ternary complex. EXPERIMENTAL Apparatus. A Shimadzu spectrophotometer UV-240 with a l-cm cell was used. Reagents and solutions. Ascorbic acid, Merck r.a., Nioxime 1% (w/v), Cu2+ solution (0.01 M) prepared by dilution of metallic Cu, Merck r.a., in 0.3 M nitric acid, and boiled double-distilled water in aglass distiller (D.B. H20) were utilized. General procedure. Transfer 40 ml propylene glycol to a 50-ml standard flask. Add, in the following sequence, 1 ml Nioxime solution, an aliquot containing ascorbic acid, 2.5 ml monochloroacetic/monochloroacetate buffer solution (pH 3.0), and 0.5 ml 0.01 M Cu(I1) solution. Dilute to the mark and determine the absorbance against a reagent blank at 385 nm. Preparation of assay solutions. For pure ascorbic acid, prepare solutions of ascorbic acid in D.B. H20. Take aliquots and apply the procedure described above. For an analysis of tablets, capsules, and coated tablets, weigh and pulverize 10 tablets or the contents of 20 capsules or coated tablets. Transfer an accurately weighed quantity of the powder, extract with D.B. H20 and filter it through a Whatman No. 5 filter paper into a standard flask, wash with several portions of D.B. Hz0 , and dilute to the mark. Transfer into a 50-ml standard flask an aliquot of the solution containing 0.03-0.6 mg of ascorbic acid, dilute to the mark, and apply the general procedure. For an analysis of ampoules and syrups, following the reactive addition sequence from the general procedure, transfer the contents of the ampoule to a 50-ml standard flask. When a high concentration of vitamin C is present, dilute the content of the ampoule or several milliliters of syrup to a suitable standard volume with D.B. H,O and apply the general procedure to an aliquot.
DETERMINATION
OF VITAMIN
C IN PHARMACEUTICALS
111
RESULTS AND DISCUSSION Development
of the Procedure
Some ternary complexes have been described as formed with Cu(II), Nioxime, and ascorbic acid (29). In this work we have studied the Cu(II):Nioxime:ascorbic acid 1:2:2, whose absorption spectrum exhibits in aqueous medium a maximum at 385 nm, and the molar absorptivity is 10,300 liters mol-’ cm-’ (r = 0.998) for 10P4 M Cu(I1) and Nioxime 0.01% (28). The maximum absorption is obtained at pH 2.4-3.1. Nevertheless, due to the instability of this complex, it does not seem useful for the determination of ascorbic acid. Therefore we tried to find some stabilizing factors for the complex. Sodium sulfite at different concentrations (2 x 10W3and 8 x 10e3 M) was tested as a stabilizer. The addition of alcohols at different ratios (%, v/v) was also tested: glycerol (60%), ethylene glycol(40 and 60%), and propylene glycol(60 and 80%). Figure 1 shows the effect of time on the absorbance of the complex. The total stabilization is achieved along the time interval studied for 80% propylene glycol. By a comparison of Figs. la and lb it can be inferred that except in propylene glycol medium, the instability increases with the concentration ratio Cu(II)/ ascorbic acid. Specificity
qf the
Method
Ascorbic acid in pharmaceutical products is accompanied by other active subA
a
0.4 -
r’. 5
I 5
10
20
30
t,(mid
IO
20
30
t.(mln)
1. Stability of Cu(II)-Nioxime-ascorbic acid complex. X = 385 nm. (a) Molar ratio, Cu(II)/ ascorbic acid = 1; P, propylene glycol, 80%; 1, ethylene glycol, 80%; 2, ethylene glycol, 40%; 3, sulfite, 8 x 1O.-3M; 4, sulfite, 2 x 10 -3 it4; 5, without additives. (b) Molar ratio, Cu(II)/ascorbic acid = 5/3; P, propylene glycol, 80%; 1, ethylene glycol, 80%; 2, glycerol, 60%; 3, propylene glycol, 60%; 4, ethylene glycol, 40%; 5, sulfite, 8 x 10m3A-f; 6, propylene glycol, 40%; 7, ethylene glycol, 20%; 8, without additives. FIG.
112
BARBAS PARDILLO ET AL.
stances (vitamins, hormones) and excipients. In order to study the possible intluence of these substances on the proposed method, a placebo containing the most common additives or excipients was prepared. For this purpose, 10 mg of ascorbic acid was mixed with different weights of additive or excipient to contain approximately the same quantity as commercial dosage forms. The results obtained are shown in Table 1. The mean recovery of ascorbic acid accompanied by the different additives was 994101%, with a relative standard deviation of 0.146%. This result allows us to state that the proposed method is specific for the additives tested, because of their nonsignificative interaction. Determination of Vitamin C in Pharmaceutical Dosage Forms The calibration graph was made with 80% propylene glycol medium by applying the general procedure. The lineality conforms to the ascorbic acid interval studied: 3 x 10W6-6 x low5 M. The experimental data agree with the equation A = 8483 C - 0.019 (C, M), with a correlation factor r = 0.9998 TABLE 1 Recovery of Ascorbic Acid in the Presence of Other Substances Usually Incorporated in Pharmaceutical Preparations: Tolerance of the Method Compound
Taken (mg)
Ascorbic acid recovery (%)
Aspartic acid Biotin Calcium gluconate Calcium pantothenate Citric acid Cyanocobalamin Dextrin Folic acid Glucose Glutamic acid Lactose Magnesium stearate Maltose Mannosa Nicotinamide Nicotinic acid Pyridoxine HCl Riboflavine Rutin Sodium saccharin Starch Sucrose Thiamine
50 5 50 25 50 2 10 2 50 10 50 5 50 50 50 50 2 5 5 50 50 50 10
101.0 2 0.6 100.2 * 0.2 100.9 ? 0.4 99.8 T 0.3 99.9 2 0.4 100.6 k 0.4 99.9 2 0.2 100.3 2 0.1 100.5 ‘- 0.6 99.8 +- 0.3 100.8 e 0.5 100.1 2 0.1 loo.5 f 0.3 100.6 f 0.4 100.2 + 0.2 100.9 +- 0.5 100.1 + 0.2 100.2 + 0.3 100.3 + 0.4 99.4 2 0.5 99.7 f 0.6 100.0 + 0.2 100.2 + 0.1
Note. Ascorbic acid, 10 mg; n = 5.
DETERMINATION
OF VITAMIN
C IN PHARMACEUTICALS
113
TABLE 2 Determination of Vitamin C in Some Pharmaceutical Preparations Ascorbic acid (mg) Name
Nominal
Found
Efferalgan Arovit C Cecrisina Captagon vitaminado Citroflavona Citroflavona (syrup) Ledovit-C (syrup) Vitamin C Roche
2OO/tablet lOOO/tablet lOOO/dose 50/costed tablet lOO/capsule 100/5 ml 500/5 ml lOO/ampoule
202.9 f 0.4 1062.4 + 1.0
1098.2 * 1.1 48.2 92.3 90.6 484.2 108.0
k 2 2 * +
0.3 0.5 0.5 0.7 0.8
0.20 0.09
0.10 0.66 0.50 0.52 0.15 0.73
Note. n = 5; tFischer= 2.776 for P = 0.05.
Table 2 shows the results obtained for the different pharmaceutical dosage forms analyzed, in statistical agreement with those proposed by the manufacturer. The precision of the proposed method was evaluated using an ordinary statistical study, under 95% probability level (30) and expressed by the confidence interval for each sample (Table 2). A relative standard deviation of 0.09473% was obtained. Therefore, it can be said that the proposed method shows a good precision and a satisfactory fidelity. REFERENCES 1. The Merck Index (Windholz et al., Eds.), p. 120. New York, 1983. 2. Gopala Rao, G.; Narayana Rao, V. Fresenius’Z. Anal. Chem., 1955, 147, 338-347. 3. Taqui Khan, M. M.; Martell, A. E. J. Amer. Chem. Sot., 1%7, 89, 4176-4185. 4. Berg], F. Biochemie Colloq. Med. Scholl, Leedo, 1943. 5. Mapson, S. Biochem. J., 1941, 38, 1332-1352. 6. Zilva, S. S. Biochem. J., 1940, 34, 61-66. 7. Maeda, E. E.; Mussa, D. M. D. N. Food Chem., 1986,22, 51-58. 8. Nishikimi, M.; Ozawa, T. Biochem. Int., 1987, 14, 11l-l 17. 9. Struhar, M.; Heinrich, J.; Banerova, K.; Mandak, M. Farm. Obz., 1987, 56, 321-328. 10. Margolis, S. A.; Black, I. J. Assoc. Off. Anal. Chem., 1987, 70, 806-809. Il. Ogata, Y.; Kosugi, Y. Tetrahedron, 1970, 26, 4711-4716. 12. Burger, N.; Karas-Gasparec, V. Talanta, 1973, 20, 782-785. 13. Vamos, E.; Gabor, E. S. Nahrung, 1973, 17, 409-414. 14. Vamos, K.;, Gabor, M. Elelmiszervizsgalati Kozl., 1973, 19, 83-89. 15. Elnenaey, El S.; Soliman, R. Talanta, 1979, 26, 1164-1166. 16. Besada, A. Talanta, 1987, 34, 731-732. 17. Skaltsa, H. D.; Tzakou, 0. A.; Koupparis, M. A.; Philianos, S. M. Anal. Lett., 1987, 20, 1679 1691.
18. 19. 20. 21. 22. 23.
Pepkowitz, L. P. .I. Biol. Chem., 1943, 151, 405-412. Robinson, W. B.; Stotz, E. J. Biol. Chem., 1945, 160, 217-225. Roe, J. H.; Kuether, C. A. Science, 1942, 95, 77. Eldawy, M. A.; Tawtik, A. S.; Elshabouri, S. R. Anal. Chem., 1975, 47, 46145. Aly, M. M. Anal. Chim. Acta, 1979, 106, 379-383. Istvan, K.; Gustane, F. Acta Pharm. Hung., 1967, 37, 127-131. 24. Hashmi, H. M.; Adil, A. S.; Viegas, A.; Ajmal, A. I. Mikrochim. Acta, 1970, 457-462.
114 25. 26. 27. 28. 29.
BARBAS
PARDILLO
ET AL.
Wahba, N.; Yassa, D. A.; Labib, R. S. Analyst (London), 1974, 99, 397-402. Baker, W. L.; Lowe, T. Analyst (London), 1985, 110, 1187-1191. Huq, G. A.; Rao, S. B. Acta Cienc. Zndica Ser. Chem., 1981, 7, 37-39. Bosch Reig, F.; Martinez Calatayud, J.; Marin Sgez, R. M. An. Quim., 1981, 77, 349-352. Babko, A. K.; Mikhel’son, P. B.; Karpova, L. V.; Karpus, N. N. Russ J. Znorg. Chem., 1%9,14, 65-68. 30. Lacroix, Y. Analyse Chimique, ZnterprPtation des rkults par le calcul statistique. Masson, Paris, 1973.
JOURNAL
4,
109-l
14 (1989)
Spectrophotometric Determination of Vitamin C Using the Copper(H)-Nioxime-Ascorbic Acid System following Stabilization in a Propylene Glycol Medium M. BARBAS PARDILLO, V. PERIS MARTINEZ,’ J. V. GIMENO ADELANTADO, AND F. BOSCH REIG Department of .Analytical Chemistry, Faculty of Chemistry, University of Valencia, Dr. Moliner 50, 46100 Butjassot, Valencia, Spain A spectrophotometric method for the determination of Vitamin C is proposed. The procedure is based on formation and stabilization of the ternary complex Cu(II)nioxime-ascorbic acid in 80% (v/v) propylene glycol-water medium. The method has a high degree of tolerance for the determination of ascorbic acid in the presence of other active substances or excipients likely to be present along with vitamin C in pharmaceutical formulations. The suggested method has proved to be rapid and precise and has been successfully applied to different commercial pharmaceutical preparations of vitamin C. Precision, measured on the relative standard deviation, did not exceed 0.73%. 8 1989 Academic press, IW.
INTRODUCTION
Ascorbic acid is essential in the human body, for the formation of collagen and intercellular material. It also influences the formation of hemoglobin and the maturation of erythrocytes. Pharmacological interest in this substance is centered on the prevention and treatment of scurvy. It has also been employed as a diuretic, as a detoxifying agent in drug poisoning, and in treatment of numerous unrelated diseases (1). Although stable in air when dry, vitamin C suffers from a lack of stability in impure preparations, in many natural products, and in solution. The vitamin oxidizes rapidly on exposure to air or light. This is the main difficulty in the determination of ascorbic acid. Oxidation by the action of atmospheric oxygen is catalyzed by several metallic cations (2-9, enzymes such as oxidase (2), and UV light (6). This catalytic oxidation is also influenced by the pH of the medium, temperature (2), and concentration, with the most concentrated solutions being the most stable (2, 4). In addition to catalytic oxidation, bacteriologic decomposition must also be considered an important interference; this action decreases with temperature (4). Several methods for the stabilization of ascorbic acid have been proposed (710). Among the numerous spectrophotometric methods cited in the references (12), the most outstanding include, with Fe(CN),3- as oxidant reagent (22), formation of Prussian blue in the presence of Fe(II1) (23, 14), formation of molyb’ To whom correspondence should be addressed. 109 0026-265x/89 $1.50 Copyright 0 1989 by Academic Press, Inc. All rights of reproduction in any form reserved.
110
BARBAS
PARDILLO
ET AL.
denum blue with ammonium molybdate as reagent (Z5), or colored complexes after reduction of Fe(II1) with ascorbic acid (16, 27). Several reagents have been used for the direct or indirect determination of vitamin C such as 2,6-dichloroindophenol (28, 29), 2,4-dinitrophenylhydrazine (20), dimethoxyquinone (21), dimethoxydiquinone (22), 4nitrobenzenediazonium fluoborate (2.?), 2,3,5triphenyltetrazolium chloride (24), and phenylhydrazinium chloride (25). The following methods have also been used: the degradation reaction with Cu(I1) and forward complexation with neocuprina (26); and the decomposition of the complex Fe(III)-resacetophenone oxime and oxidants such as electrolytic Au(II1) (27). Most of the spectrophotometric methods based on the redox reaction between ascorbic acid and some other reagent show the lack of selectivity of the redox process. In the present work the spectrophotometric determination of vitamin C based on measurement of the color intensity of the ternary complex with Cu(I1) and nioxime (28) is proposed. It must be adequately stabilized in order to obtain the greater reliability and security of the proposed method. Several stabilizing agents and aquoorganic media were previously used by other authors in order to obtain a successful procedure to stabilize ascorbic acid and its solution. The present study has allowed us to choose the best medium for the stabilization of the ternary complex. EXPERIMENTAL Apparatus. A Shimadzu spectrophotometer UV-240 with a l-cm cell was used. Reagents and solutions. Ascorbic acid, Merck r.a., Nioxime 1% (w/v), Cu2+ solution (0.01 M) prepared by dilution of metallic Cu, Merck r.a., in 0.3 M nitric acid, and boiled double-distilled water in aglass distiller (D.B. H20) were utilized. General procedure. Transfer 40 ml propylene glycol to a 50-ml standard flask. Add, in the following sequence, 1 ml Nioxime solution, an aliquot containing ascorbic acid, 2.5 ml monochloroacetic/monochloroacetate buffer solution (pH 3.0), and 0.5 ml 0.01 M Cu(I1) solution. Dilute to the mark and determine the absorbance against a reagent blank at 385 nm. Preparation of assay solutions. For pure ascorbic acid, prepare solutions of ascorbic acid in D.B. H20. Take aliquots and apply the procedure described above. For an analysis of tablets, capsules, and coated tablets, weigh and pulverize 10 tablets or the contents of 20 capsules or coated tablets. Transfer an accurately weighed quantity of the powder, extract with D.B. H20 and filter it through a Whatman No. 5 filter paper into a standard flask, wash with several portions of D.B. Hz0 , and dilute to the mark. Transfer into a 50-ml standard flask an aliquot of the solution containing 0.03-0.6 mg of ascorbic acid, dilute to the mark, and apply the general procedure. For an analysis of ampoules and syrups, following the reactive addition sequence from the general procedure, transfer the contents of the ampoule to a 50-ml standard flask. When a high concentration of vitamin C is present, dilute the content of the ampoule or several milliliters of syrup to a suitable standard volume with D.B. H,O and apply the general procedure to an aliquot.
DETERMINATION
OF VITAMIN
C IN PHARMACEUTICALS
111
RESULTS AND DISCUSSION Development
of the Procedure
Some ternary complexes have been described as formed with Cu(II), Nioxime, and ascorbic acid (29). In this work we have studied the Cu(II):Nioxime:ascorbic acid 1:2:2, whose absorption spectrum exhibits in aqueous medium a maximum at 385 nm, and the molar absorptivity is 10,300 liters mol-’ cm-’ (r = 0.998) for 10P4 M Cu(I1) and Nioxime 0.01% (28). The maximum absorption is obtained at pH 2.4-3.1. Nevertheless, due to the instability of this complex, it does not seem useful for the determination of ascorbic acid. Therefore we tried to find some stabilizing factors for the complex. Sodium sulfite at different concentrations (2 x 10W3and 8 x 10e3 M) was tested as a stabilizer. The addition of alcohols at different ratios (%, v/v) was also tested: glycerol (60%), ethylene glycol(40 and 60%), and propylene glycol(60 and 80%). Figure 1 shows the effect of time on the absorbance of the complex. The total stabilization is achieved along the time interval studied for 80% propylene glycol. By a comparison of Figs. la and lb it can be inferred that except in propylene glycol medium, the instability increases with the concentration ratio Cu(II)/ ascorbic acid. Specificity
qf the
Method
Ascorbic acid in pharmaceutical products is accompanied by other active subA
a
0.4 -
r’. 5
I 5
10
20
30
t,(mid
IO
20
30
t.(mln)
1. Stability of Cu(II)-Nioxime-ascorbic acid complex. X = 385 nm. (a) Molar ratio, Cu(II)/ ascorbic acid = 1; P, propylene glycol, 80%; 1, ethylene glycol, 80%; 2, ethylene glycol, 40%; 3, sulfite, 8 x 1O.-3M; 4, sulfite, 2 x 10 -3 it4; 5, without additives. (b) Molar ratio, Cu(II)/ascorbic acid = 5/3; P, propylene glycol, 80%; 1, ethylene glycol, 80%; 2, glycerol, 60%; 3, propylene glycol, 60%; 4, ethylene glycol, 40%; 5, sulfite, 8 x 10m3A-f; 6, propylene glycol, 40%; 7, ethylene glycol, 20%; 8, without additives. FIG.
112
BARBAS PARDILLO ET AL.
stances (vitamins, hormones) and excipients. In order to study the possible intluence of these substances on the proposed method, a placebo containing the most common additives or excipients was prepared. For this purpose, 10 mg of ascorbic acid was mixed with different weights of additive or excipient to contain approximately the same quantity as commercial dosage forms. The results obtained are shown in Table 1. The mean recovery of ascorbic acid accompanied by the different additives was 994101%, with a relative standard deviation of 0.146%. This result allows us to state that the proposed method is specific for the additives tested, because of their nonsignificative interaction. Determination of Vitamin C in Pharmaceutical Dosage Forms The calibration graph was made with 80% propylene glycol medium by applying the general procedure. The lineality conforms to the ascorbic acid interval studied: 3 x 10W6-6 x low5 M. The experimental data agree with the equation A = 8483 C - 0.019 (C, M), with a correlation factor r = 0.9998 TABLE 1 Recovery of Ascorbic Acid in the Presence of Other Substances Usually Incorporated in Pharmaceutical Preparations: Tolerance of the Method Compound
Taken (mg)
Ascorbic acid recovery (%)
Aspartic acid Biotin Calcium gluconate Calcium pantothenate Citric acid Cyanocobalamin Dextrin Folic acid Glucose Glutamic acid Lactose Magnesium stearate Maltose Mannosa Nicotinamide Nicotinic acid Pyridoxine HCl Riboflavine Rutin Sodium saccharin Starch Sucrose Thiamine
50 5 50 25 50 2 10 2 50 10 50 5 50 50 50 50 2 5 5 50 50 50 10
101.0 2 0.6 100.2 * 0.2 100.9 ? 0.4 99.8 T 0.3 99.9 2 0.4 100.6 k 0.4 99.9 2 0.2 100.3 2 0.1 100.5 ‘- 0.6 99.8 +- 0.3 100.8 e 0.5 100.1 2 0.1 loo.5 f 0.3 100.6 f 0.4 100.2 + 0.2 100.9 +- 0.5 100.1 + 0.2 100.2 + 0.3 100.3 + 0.4 99.4 2 0.5 99.7 f 0.6 100.0 + 0.2 100.2 + 0.1
Note. Ascorbic acid, 10 mg; n = 5.
DETERMINATION
OF VITAMIN
C IN PHARMACEUTICALS
113
TABLE 2 Determination of Vitamin C in Some Pharmaceutical Preparations Ascorbic acid (mg) Name
Nominal
Found
Efferalgan Arovit C Cecrisina Captagon vitaminado Citroflavona Citroflavona (syrup) Ledovit-C (syrup) Vitamin C Roche
2OO/tablet lOOO/tablet lOOO/dose 50/costed tablet lOO/capsule 100/5 ml 500/5 ml lOO/ampoule
202.9 f 0.4 1062.4 + 1.0
1098.2 * 1.1 48.2 92.3 90.6 484.2 108.0
k 2 2 * +
0.3 0.5 0.5 0.7 0.8
0.20 0.09
0.10 0.66 0.50 0.52 0.15 0.73
Note. n = 5; tFischer= 2.776 for P = 0.05.
Table 2 shows the results obtained for the different pharmaceutical dosage forms analyzed, in statistical agreement with those proposed by the manufacturer. The precision of the proposed method was evaluated using an ordinary statistical study, under 95% probability level (30) and expressed by the confidence interval for each sample (Table 2). A relative standard deviation of 0.09473% was obtained. Therefore, it can be said that the proposed method shows a good precision and a satisfactory fidelity. REFERENCES 1. The Merck Index (Windholz et al., Eds.), p. 120. New York, 1983. 2. Gopala Rao, G.; Narayana Rao, V. Fresenius’Z. Anal. Chem., 1955, 147, 338-347. 3. Taqui Khan, M. M.; Martell, A. E. J. Amer. Chem. Sot., 1%7, 89, 4176-4185. 4. Berg], F. Biochemie Colloq. Med. Scholl, Leedo, 1943. 5. Mapson, S. Biochem. J., 1941, 38, 1332-1352. 6. Zilva, S. S. Biochem. J., 1940, 34, 61-66. 7. Maeda, E. E.; Mussa, D. M. D. N. Food Chem., 1986,22, 51-58. 8. Nishikimi, M.; Ozawa, T. Biochem. Int., 1987, 14, 11l-l 17. 9. Struhar, M.; Heinrich, J.; Banerova, K.; Mandak, M. Farm. Obz., 1987, 56, 321-328. 10. Margolis, S. A.; Black, I. J. Assoc. Off. Anal. Chem., 1987, 70, 806-809. Il. Ogata, Y.; Kosugi, Y. Tetrahedron, 1970, 26, 4711-4716. 12. Burger, N.; Karas-Gasparec, V. Talanta, 1973, 20, 782-785. 13. Vamos, E.; Gabor, E. S. Nahrung, 1973, 17, 409-414. 14. Vamos, K.;, Gabor, M. Elelmiszervizsgalati Kozl., 1973, 19, 83-89. 15. Elnenaey, El S.; Soliman, R. Talanta, 1979, 26, 1164-1166. 16. Besada, A. Talanta, 1987, 34, 731-732. 17. Skaltsa, H. D.; Tzakou, 0. A.; Koupparis, M. A.; Philianos, S. M. Anal. Lett., 1987, 20, 1679 1691.
18. 19. 20. 21. 22. 23.
Pepkowitz, L. P. .I. Biol. Chem., 1943, 151, 405-412. Robinson, W. B.; Stotz, E. J. Biol. Chem., 1945, 160, 217-225. Roe, J. H.; Kuether, C. A. Science, 1942, 95, 77. Eldawy, M. A.; Tawtik, A. S.; Elshabouri, S. R. Anal. Chem., 1975, 47, 46145. Aly, M. M. Anal. Chim. Acta, 1979, 106, 379-383. Istvan, K.; Gustane, F. Acta Pharm. Hung., 1967, 37, 127-131. 24. Hashmi, H. M.; Adil, A. S.; Viegas, A.; Ajmal, A. I. Mikrochim. Acta, 1970, 457-462.
114 25. 26. 27. 28. 29.
BARBAS
PARDILLO
ET AL.
Wahba, N.; Yassa, D. A.; Labib, R. S. Analyst (London), 1974, 99, 397-402. Baker, W. L.; Lowe, T. Analyst (London), 1985, 110, 1187-1191. Huq, G. A.; Rao, S. B. Acta Cienc. Zndica Ser. Chem., 1981, 7, 37-39. Bosch Reig, F.; Martinez Calatayud, J.; Marin Sgez, R. M. An. Quim., 1981, 77, 349-352. Babko, A. K.; Mikhel’son, P. B.; Karpova, L. V.; Karpus, N. N. Russ J. Znorg. Chem., 1%9,14, 65-68. 30. Lacroix, Y. Analyse Chimique, ZnterprPtation des rkults par le calcul statistique. Masson, Paris, 1973.