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Potentiometric determination of penicillins with ion-selective electrodes
0039-9140/89 $3.00 + 0.00 Copyright 0 1989 Pergamon Pressplc
Talanro, Vol. 36, No. 12, pp. 1249-1252, 1989 Printed in Great Britain. All rights reserved
POTENTIOMETRIC DETERMINATION OF PENICILLINS WITH ION-SELECTIVE ELECTRODES S. Z. YAO*, J. SHIAO and L. H. NIE New Material Research Institute, Department of Chemical Engineering, Hunan University, Changsha 410012, People’s Republic of China
(Received 6 January 1989. Accepted 20 June 1989) Summary-Quaternary ammonium, phosphonium and arsonium membrane electrodes sensitive to benzylpenicillin, ampicillin and oxacillin have been investigated. The order of merit of electrode performance is cetyltrioctylammonium > cetyltrioctylphosphonium > cetyltrioctylarsonium. The electrodes are suggested for use in rapid determination of penicillin drugs by direct potentiometry.
Penicillin antibiotics are widely used. In China they are usually determined either by back-titration of their solutions in sodium hydroxide or by spectrophotometry.’ Other methods suggested include ultraviolet spectrophotometry,2 fluorimetry,3 titrimetry,4 chromatography’ and anodic stripping voltammetry.6 Papariello et al.’ used an enzyme electrode based on the use of penicillinase to determine penicillin. This electrode responds slowly and its life-span is rather short. Lead(II), mercury(I1) and iodide-selective electrodes have also been proposed for use in the potentiometric determination of penicillins,‘-” but these procedures are complicated. Electrodes selective for benzylpenicillin have been reported.“*” They employ benzyldimethylcetylammonium as the exchange site, but the linearity ranges are rather narrow. In this study, ion-selective electrodes based on the use of quatemary ammonium, phosphonium or arsonium ions as the exchange site are reported and suggested for potentiometric determination of penicillin drugs.
Buffer solurion. Sulphuric acid (0X4,50 ml) was added to 53.6 ml of 1M tris(hydroxymethyl)aminomethane and the mixture was diluted to 1 litre. The buffer had pH 7.02 and ionic strength O.lM. Standard oxacillin solution. Sodium oxacillin (0.2207 g) was dissolved in the minimum amount of water and diluted to volume in a SO-ml standard flask with the buffer to give a O.OlM standard solution. Standard series (10-6-10-ZM) were prepared by successive dilutions with the buffer. Ampicillin and benzylpenicillin solutions were prepared similarly. Preparation of the ion-pair complexes Oxucillin-CTOA. Cetyltrioctylammonium iodide (0.1 g) was dissolved in 20 ml of chloroform. The solution was shaken in a separating funnel for 15 min with 20 ml of O.OlM sodium oxacillin solution. The aqueous layer was separated and the organic layer was treated with four 20-ml portions of O.OlM sodium oxacillin solution. The organic layer was dried with anhydrous sodium sulphate and filtered, and the solvent was evaporated on a water-bath, to give a pale yellow product. ~xacillin-CTOP, oxacillinCTOAs and ion-pair complexes of ampicillin and benzylpenicillin with CTOA, CTOP and CTOAs were prepared similarly.
EXPERIMENTAL
Electrode preparation
Apparafus The
apparatus used was the same as that reported
previously.‘3 Reagents
Cetyltrioctylammonium (CTOA), cetyltrioctylphosphonium (CTOP) and cetyltrioctylarsonium (CTOAs) salts were synthesized in this laboratory.r4~” All drugs used were of pharmacopoeia1 quality’ and all chemicals used were of analytical reagent grade. Doubly distilled water was used throughout. *Author for correspondence. The general performance characteristics of the cetyltrioctylammonium electrodes (slope, linearity range and working pH range) were cited in a report entitled “Some Aspects of Recent Development of Drug ISEs” presented by the senior author at the International Symposium on Electroanalysis and Sensors in Biomedical, Environmental and Industrial Sciences (6-9 April 1987, Cardiff, GB), an extended summary of which appeared in Anal. Proc., 1987, 24, 338.
The electrodes were constructed as described previously” and preconditioned in a 0.00 1M solution of the appropriate penicillin for 24 hr. A double-junction saturated calomel electrode containing O.lM sodium nitrate in its outer compartment was used as reference electrode.
RESULTS AND DISCUSSION
Comparison
of electroactive
materials
Penicillin electrodes with either CTOA, CTOP or CTOAs ions as exchange sites were evaluated in order to compare their response characteristics. Those based on CTOA were found to give the best response, and those based on CTOAs were unsatisfactory (Fig. 1). CTOA was therefore chosen as the most satisfactory for use in the penicillin ion-selective electrodes. The response characteristics of these electrodes are given in Table 1.
1249
1250 Eflect
g. z. of plasticizers
and membrane
YAO
et al.
concentrations
The effect of different plasticizers, viz. dibutyl phthalate (DBP), tributyl phosphate (TBP), dioctyl phthalate (DOP) and didecyl phthalate (DDP) was investigated. The best electrode response was found with DBP. The optimum concentration of electroactive material in the membrane was 0.005M. Characteristics of the oxacillin-CTOP electrode are shown in Table 2. Effect of pH
The effect of pH was studied for oxacillin-CTOA, ampicillin-CTOA and benzylpenicillin-CTOA electrode potentials. No significant variation in membrane potential was observed for pH ranges 5.6-9.0 (oxacillin), 4.6-9.1 (ampicillin) and M-8.9 (benzylpenicillin). Typical results are shown in Fig. 2. The pH ranges of the penicillin-CTOP electrodes are approximately the same as those observed for the penicillin-CTOA
3
1
5
7
PC Fig. 1. Calibration curves. OxacillinCTOP electrode (I), oxacillin-CTOA electrode (2), oxacillinCTOAs electrode (3).
electrodes.
Electrode potential
When the electrode potential was repeatedly measured in a O.OOlM sodium oxacillin solution, the standard deviation was 0.6 mV for the oxacillinCTOA and for the oxacillin-CTOP electrodes (six determinations).
a0 -
1
-.-~.-.-.-.r,
\
/’ 40
t
-
Z
Electrode versatility
The ampicillin-CTOA electrode can respond to both benzylpenicillin and ampicillin (as well as oxacillin) with a nearly Nemstian response slope, but the linearity range is smaller than that obtained for oxacillin (Table 3). This implies that the electrode response characteristics are determined mainly by the exchange site of the electroactive material.-The same result was obtained electrodes.13
with sulpha-drug
sensitive
Table 1. Response characteristics
Electrode Oxacillin-CTOA BenzylpenicillinCTOA AmpicillinCTOA
G
2 o-
.-.-.-.x. /
-40
’
’ 5
I
I
I
I
6
7
6
9
DH Fig. 2. Effect of pH on the potential of the oxacillin-CTOA electrode. Concentration of sodium oxacillin: O.OOlM (1); O.OlM (2).
of some penicillinCTOA nenicillin drugs
electrodes sensitive to
Slope, Linearity -mV/log C range, mM
Drug ion sensed Oxacillin Benzylpenicilhn Ampicillin
58.3 + 1.0 59.1+ 1.2 59.3 + _ 1.3
Detection limit, mM 0.006 0.04 0.05
5fkO.02 50-0.1 50-0.2
Plasticizer: DBP; membrane concentration: 0.005M. Table 2. Effect of membrane plasticizer and membrane concentration Membrane plasticizer DBP TBP DOP DDP
Membrane concentration, mM 0.5 5 10 5 5 5
I 10
Slope, -mV/log C 57.3 + 58.0 f 58.0 f 58.0 + 51.5 * 58.0 f
Electroactive material: oxacillin-CTOP.
1.5 1.0 1.0 1.0 0.7 1.4
Linearity range, mM 5fkO.l 50-0.03 5fkO.03 50-0.04 50-0.3 5fkO.3
Detection limit, mM 0.04 0.01 0.01 0.015 0.1 0.1
Penicillin ion-selective electrodes
1251
Table 6. Determination of penicillin drugs by potentiometry with an inverted penicillindrug selective electrode’
Selectivity
Selectivities of the oxacillin-CTOA, oxacillinCTOP, benzylpenicillin-CTOA and ampicillinCTOA electrodes were evaluated by the mixedsolution and separate-solution procedures in order to investigate the influence of common interferents on the electrode response. The results are listed in Table 4. Electrode selectivity towards perchlorate, iodide, thiocyanate, nitrate and nitrite salts is rather poor. The Z/r2 criterion has been suggested for characterizing the selectivity of electrodes towards inorganic ions.16 We have examined the selectivity coefficients of the inorganic ions listed in Table 4 in terms of Z/r2. Correlation coefficients of 0.82-0.84 were obtained for the four electrodes tested (Table 5).
Added, M 2.207 8.828 44.14 220.7 6.988 17.47 34.94 174.7 7.127 17.82 35.64 178.2
Drug Oxacillin
Ampicillin
Benzylpenicillin
Found, H 2.31 8.89 44.4 215.7 7.20 17.88 34.90 170.7 7.43 18.23 35.6 182.3
-
Renzylpenicillin Amicillin Preconditioning
Slope,
m V/logC
Linearity range,
Detection limit,
mM
mM
50-0.1 5WJ.2
0.04 0.06
58.5 * 1.5 57.5 f 2.1 time: 10 hr.
Table 4. Log Kr’ for the penicillin-drug selective electrodes Electrode Interferent Ammonium fluoride Sodium chloride Potassium bromide Potassium iodide Potassium thiocyanate Sodium nitrate Sodium nitrite Sodium perchlorate Sodium carbonate Sodium sulphate Aspartic acid Alanine Glycine Glutamic acid Sulphosalicylic acid Urea Ampicillin Renzylpenicillin Tetracycline hydrochloride Streptomycin sulphate Glucose Starch
C,$ mM 1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 1 10 1 1 1 1 1 0.1 0.1 0.1 0.1 1
I’
II*
111t
IVt
l/(Z/r2)
-0.85 -0.45 -0.21 0.65 0.90 0.05 -0.20 1.50 -1.95 -2.10 - 1.28 -1.10 -1.03 -0.94 0.14 -0.10 -0.60 -0.40 -0.62
-0.90 -0.50 -0.20 0.70 0.95 0.07 -0.15 1.60 - 1.96 -2.10
-0.60 -0.41 -0.21 2.31 2.83 1.10 0.12 4.07 - 1.12 -1.28 -0.82 -0.76 -0.58 -0.41 0.61
-0.81 -0.39 -0.48 2.79 3.34 1.55 0.45 4.53 - 1.07 -1.38 -0.31 -0.21 -0.16 -0.02 0.97
1.42 2.80 3.31 4.24 3.80 3.57 2.40 4.00 1.71 2.65
$.I%,
-0.11 -0.58 -0.35 -0.45 - 1.95 - 1.72 -1.52 -1.20 No interference
I: Oxacillin-CTOA electrode; II: oxacillin-CTOP electrode; III: benzylpenicillin-CTOA electrode; IV: ampicillin-CfPA electrode. *Mixed-solution procedure @H 7.02). tseparate-solution procedure (C, = C, = O.OOlM), pH 7.02. Table 5. Relationship between electrode selectivity and ionic parameter Z/r2 Electrode RenzylpenicillinCTOA Ampicillin-CTOA Oxacillin-CTOA Oxacillin-CTOP
104.7 100.7 100.6 97.7 103.0 102.3 99.9 97.7 104.2 102.3 99.7 102.3
*Electrode: all-solid-state oxacillin-CTOA electrode with a gold substrate.
Table 3. Response of the oxacillin_CTOA electrode towards benzylpenicillin and ampicillin Ion sensed
Recovery, %
Correlation coefficient
Equation log Kr’ = log K$+’= log K$’ = log KY’ =
l.55(Z/r2)-’ 1.78(Z/r2)-’ l.06(Z/r2)-’ l.OE(Z/r*)-’
-
3.90 4.37 3.50 3.56
0.82 0.84 0.84 0.84
S. Z.
1252
YAO
et a/.
Potentiometric determination of penicillin drugs
2.
The electrode can be used for rapid determination of penicillin drugs by direct potentiometry and the procedure is much easier and faster than the microbial method.’ Small amounts (pg) of penicillin drugs can be determined with the inverted all-solid-state electrode. Results of oxacillin, ampicillin and benzylpenicillin determinations are listed in Table 6. All these drugs were determined by using an inverted all-solid-state oxacillm-CTOA electrode. The average recoveries were 100.9 + 2.9% (oxacillin), 100.7 + 2.4% (ampicillin) and 102.1 + 1.8% (benzylpenicillin). The electrode was also used for the determination of penicillin drug content in injections. The results were 99.1% (sodium benzylpenicillin), 98.9% (potassium benzylpenicillin) and 97.8% (sodium oxacillin), in agreement with the results obtained by the pharmacopoeial method’ (99.0, 98.7 and 97.9% respectively).
3. 4.
Acknowledgement-This
work was supported by the Natural Science Funds of the People’s Republic of China. REFERENCES
1. Chinese Pharmacopoeia, 3rd Ed., Vol. II, pp. 208-212.
Beijing, 1985.
8.
J. Haginaka, J. Wakai, H. Yasuda and T. Uno, Anal. Sci., 1985, 1, 73. W. J. Jusko, J. Pharm. Sci., 1971, 60, 729. B. PosuiHilova,M. Simkovi and J. KubeS. Cesk. Farm.. 1985, j4, 106: H. Much, H. J. Niclas, Th. Buchheim, B. Drescher and L. Zoelch, Pharmacie, 1985, 40, 627. U. Forsman, Anal. Chim. Acta, 1983, 146, 71. G. J. Papariello, A. K. Muhkerji and C. M. Shearer, Anal. Chem., 1973, 45, 790. S. S. M. Hassan, M. T. M. Zaki and M. H. Eldesouki,
9.
B. Karlberg and U. Forsman, Anal. Chim. Acta, 1976,
5. 6. 7.
Talanta, 1979, 26, 91. 83, 309.
10. A. Blazsek-Bodo, A. Varga and I. Kiss, Rev. Chim. (Bucharest),
1978, 29, 464.
11. L. Campanella, M. Tomassetti and
R. Sbrilli,
Ann. Ch&
(Rome), 1986, 76, 483. 12. L. CamDanella. F. Mazzei. R. Sbrilli and M. Tomassetti, J. Pharm. Biohed. Anal., 1988, 6, 299.
13. S. Z. Yao, J. Shiao and L. H. Nie, Talanfa, 1987, 34, 977.
14. S. Z. Yao and Y. C. Tang, Acta Pharm. Sinica, 1984, 19, 455.
15. S. Z. Yao, J. Shiao and L. H. Nie, Scienfia Sinica (Ser. B), 1988, 31, 1222. 16. H. Z. Gong, D. Xiao and C. L. Wang, Chem. J. Chin. Univ., 1984, 5, 264.
Talanro, Vol. 36, No. 12, pp. 1249-1252, 1989 Printed in Great Britain. All rights reserved
POTENTIOMETRIC DETERMINATION OF PENICILLINS WITH ION-SELECTIVE ELECTRODES S. Z. YAO*, J. SHIAO and L. H. NIE New Material Research Institute, Department of Chemical Engineering, Hunan University, Changsha 410012, People’s Republic of China
(Received 6 January 1989. Accepted 20 June 1989) Summary-Quaternary ammonium, phosphonium and arsonium membrane electrodes sensitive to benzylpenicillin, ampicillin and oxacillin have been investigated. The order of merit of electrode performance is cetyltrioctylammonium > cetyltrioctylphosphonium > cetyltrioctylarsonium. The electrodes are suggested for use in rapid determination of penicillin drugs by direct potentiometry.
Penicillin antibiotics are widely used. In China they are usually determined either by back-titration of their solutions in sodium hydroxide or by spectrophotometry.’ Other methods suggested include ultraviolet spectrophotometry,2 fluorimetry,3 titrimetry,4 chromatography’ and anodic stripping voltammetry.6 Papariello et al.’ used an enzyme electrode based on the use of penicillinase to determine penicillin. This electrode responds slowly and its life-span is rather short. Lead(II), mercury(I1) and iodide-selective electrodes have also been proposed for use in the potentiometric determination of penicillins,‘-” but these procedures are complicated. Electrodes selective for benzylpenicillin have been reported.“*” They employ benzyldimethylcetylammonium as the exchange site, but the linearity ranges are rather narrow. In this study, ion-selective electrodes based on the use of quatemary ammonium, phosphonium or arsonium ions as the exchange site are reported and suggested for potentiometric determination of penicillin drugs.
Buffer solurion. Sulphuric acid (0X4,50 ml) was added to 53.6 ml of 1M tris(hydroxymethyl)aminomethane and the mixture was diluted to 1 litre. The buffer had pH 7.02 and ionic strength O.lM. Standard oxacillin solution. Sodium oxacillin (0.2207 g) was dissolved in the minimum amount of water and diluted to volume in a SO-ml standard flask with the buffer to give a O.OlM standard solution. Standard series (10-6-10-ZM) were prepared by successive dilutions with the buffer. Ampicillin and benzylpenicillin solutions were prepared similarly. Preparation of the ion-pair complexes Oxucillin-CTOA. Cetyltrioctylammonium iodide (0.1 g) was dissolved in 20 ml of chloroform. The solution was shaken in a separating funnel for 15 min with 20 ml of O.OlM sodium oxacillin solution. The aqueous layer was separated and the organic layer was treated with four 20-ml portions of O.OlM sodium oxacillin solution. The organic layer was dried with anhydrous sodium sulphate and filtered, and the solvent was evaporated on a water-bath, to give a pale yellow product. ~xacillin-CTOP, oxacillinCTOAs and ion-pair complexes of ampicillin and benzylpenicillin with CTOA, CTOP and CTOAs were prepared similarly.
EXPERIMENTAL
Electrode preparation
Apparafus The
apparatus used was the same as that reported
previously.‘3 Reagents
Cetyltrioctylammonium (CTOA), cetyltrioctylphosphonium (CTOP) and cetyltrioctylarsonium (CTOAs) salts were synthesized in this laboratory.r4~” All drugs used were of pharmacopoeia1 quality’ and all chemicals used were of analytical reagent grade. Doubly distilled water was used throughout. *Author for correspondence. The general performance characteristics of the cetyltrioctylammonium electrodes (slope, linearity range and working pH range) were cited in a report entitled “Some Aspects of Recent Development of Drug ISEs” presented by the senior author at the International Symposium on Electroanalysis and Sensors in Biomedical, Environmental and Industrial Sciences (6-9 April 1987, Cardiff, GB), an extended summary of which appeared in Anal. Proc., 1987, 24, 338.
The electrodes were constructed as described previously” and preconditioned in a 0.00 1M solution of the appropriate penicillin for 24 hr. A double-junction saturated calomel electrode containing O.lM sodium nitrate in its outer compartment was used as reference electrode.
RESULTS AND DISCUSSION
Comparison
of electroactive
materials
Penicillin electrodes with either CTOA, CTOP or CTOAs ions as exchange sites were evaluated in order to compare their response characteristics. Those based on CTOA were found to give the best response, and those based on CTOAs were unsatisfactory (Fig. 1). CTOA was therefore chosen as the most satisfactory for use in the penicillin ion-selective electrodes. The response characteristics of these electrodes are given in Table 1.
1249
1250 Eflect
g. z. of plasticizers
and membrane
YAO
et al.
concentrations
The effect of different plasticizers, viz. dibutyl phthalate (DBP), tributyl phosphate (TBP), dioctyl phthalate (DOP) and didecyl phthalate (DDP) was investigated. The best electrode response was found with DBP. The optimum concentration of electroactive material in the membrane was 0.005M. Characteristics of the oxacillin-CTOP electrode are shown in Table 2. Effect of pH
The effect of pH was studied for oxacillin-CTOA, ampicillin-CTOA and benzylpenicillin-CTOA electrode potentials. No significant variation in membrane potential was observed for pH ranges 5.6-9.0 (oxacillin), 4.6-9.1 (ampicillin) and M-8.9 (benzylpenicillin). Typical results are shown in Fig. 2. The pH ranges of the penicillin-CTOP electrodes are approximately the same as those observed for the penicillin-CTOA
3
1
5
7
PC Fig. 1. Calibration curves. OxacillinCTOP electrode (I), oxacillin-CTOA electrode (2), oxacillinCTOAs electrode (3).
electrodes.
Electrode potential
When the electrode potential was repeatedly measured in a O.OOlM sodium oxacillin solution, the standard deviation was 0.6 mV for the oxacillinCTOA and for the oxacillin-CTOP electrodes (six determinations).
a0 -
1
-.-~.-.-.-.r,
\
/’ 40
t
-
Z
Electrode versatility
The ampicillin-CTOA electrode can respond to both benzylpenicillin and ampicillin (as well as oxacillin) with a nearly Nemstian response slope, but the linearity range is smaller than that obtained for oxacillin (Table 3). This implies that the electrode response characteristics are determined mainly by the exchange site of the electroactive material.-The same result was obtained electrodes.13
with sulpha-drug
sensitive
Table 1. Response characteristics
Electrode Oxacillin-CTOA BenzylpenicillinCTOA AmpicillinCTOA
G
2 o-
.-.-.-.x. /
-40
’
’ 5
I
I
I
I
6
7
6
9
DH Fig. 2. Effect of pH on the potential of the oxacillin-CTOA electrode. Concentration of sodium oxacillin: O.OOlM (1); O.OlM (2).
of some penicillinCTOA nenicillin drugs
electrodes sensitive to
Slope, Linearity -mV/log C range, mM
Drug ion sensed Oxacillin Benzylpenicilhn Ampicillin
58.3 + 1.0 59.1+ 1.2 59.3 + _ 1.3
Detection limit, mM 0.006 0.04 0.05
5fkO.02 50-0.1 50-0.2
Plasticizer: DBP; membrane concentration: 0.005M. Table 2. Effect of membrane plasticizer and membrane concentration Membrane plasticizer DBP TBP DOP DDP
Membrane concentration, mM 0.5 5 10 5 5 5
I 10
Slope, -mV/log C 57.3 + 58.0 f 58.0 f 58.0 + 51.5 * 58.0 f
Electroactive material: oxacillin-CTOP.
1.5 1.0 1.0 1.0 0.7 1.4
Linearity range, mM 5fkO.l 50-0.03 5fkO.03 50-0.04 50-0.3 5fkO.3
Detection limit, mM 0.04 0.01 0.01 0.015 0.1 0.1
Penicillin ion-selective electrodes
1251
Table 6. Determination of penicillin drugs by potentiometry with an inverted penicillindrug selective electrode’
Selectivity
Selectivities of the oxacillin-CTOA, oxacillinCTOP, benzylpenicillin-CTOA and ampicillinCTOA electrodes were evaluated by the mixedsolution and separate-solution procedures in order to investigate the influence of common interferents on the electrode response. The results are listed in Table 4. Electrode selectivity towards perchlorate, iodide, thiocyanate, nitrate and nitrite salts is rather poor. The Z/r2 criterion has been suggested for characterizing the selectivity of electrodes towards inorganic ions.16 We have examined the selectivity coefficients of the inorganic ions listed in Table 4 in terms of Z/r2. Correlation coefficients of 0.82-0.84 were obtained for the four electrodes tested (Table 5).
Added, M 2.207 8.828 44.14 220.7 6.988 17.47 34.94 174.7 7.127 17.82 35.64 178.2
Drug Oxacillin
Ampicillin
Benzylpenicillin
Found, H 2.31 8.89 44.4 215.7 7.20 17.88 34.90 170.7 7.43 18.23 35.6 182.3
-
Renzylpenicillin Amicillin Preconditioning
Slope,
m V/logC
Linearity range,
Detection limit,
mM
mM
50-0.1 5WJ.2
0.04 0.06
58.5 * 1.5 57.5 f 2.1 time: 10 hr.
Table 4. Log Kr’ for the penicillin-drug selective electrodes Electrode Interferent Ammonium fluoride Sodium chloride Potassium bromide Potassium iodide Potassium thiocyanate Sodium nitrate Sodium nitrite Sodium perchlorate Sodium carbonate Sodium sulphate Aspartic acid Alanine Glycine Glutamic acid Sulphosalicylic acid Urea Ampicillin Renzylpenicillin Tetracycline hydrochloride Streptomycin sulphate Glucose Starch
C,$ mM 1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 1 10 1 1 1 1 1 0.1 0.1 0.1 0.1 1
I’
II*
111t
IVt
l/(Z/r2)
-0.85 -0.45 -0.21 0.65 0.90 0.05 -0.20 1.50 -1.95 -2.10 - 1.28 -1.10 -1.03 -0.94 0.14 -0.10 -0.60 -0.40 -0.62
-0.90 -0.50 -0.20 0.70 0.95 0.07 -0.15 1.60 - 1.96 -2.10
-0.60 -0.41 -0.21 2.31 2.83 1.10 0.12 4.07 - 1.12 -1.28 -0.82 -0.76 -0.58 -0.41 0.61
-0.81 -0.39 -0.48 2.79 3.34 1.55 0.45 4.53 - 1.07 -1.38 -0.31 -0.21 -0.16 -0.02 0.97
1.42 2.80 3.31 4.24 3.80 3.57 2.40 4.00 1.71 2.65
$.I%,
-0.11 -0.58 -0.35 -0.45 - 1.95 - 1.72 -1.52 -1.20 No interference
I: Oxacillin-CTOA electrode; II: oxacillin-CTOP electrode; III: benzylpenicillin-CTOA electrode; IV: ampicillin-CfPA electrode. *Mixed-solution procedure @H 7.02). tseparate-solution procedure (C, = C, = O.OOlM), pH 7.02. Table 5. Relationship between electrode selectivity and ionic parameter Z/r2 Electrode RenzylpenicillinCTOA Ampicillin-CTOA Oxacillin-CTOA Oxacillin-CTOP
104.7 100.7 100.6 97.7 103.0 102.3 99.9 97.7 104.2 102.3 99.7 102.3
*Electrode: all-solid-state oxacillin-CTOA electrode with a gold substrate.
Table 3. Response of the oxacillin_CTOA electrode towards benzylpenicillin and ampicillin Ion sensed
Recovery, %
Correlation coefficient
Equation log Kr’ = log K$+’= log K$’ = log KY’ =
l.55(Z/r2)-’ 1.78(Z/r2)-’ l.06(Z/r2)-’ l.OE(Z/r*)-’
-
3.90 4.37 3.50 3.56
0.82 0.84 0.84 0.84
S. Z.
1252
YAO
et a/.
Potentiometric determination of penicillin drugs
2.
The electrode can be used for rapid determination of penicillin drugs by direct potentiometry and the procedure is much easier and faster than the microbial method.’ Small amounts (pg) of penicillin drugs can be determined with the inverted all-solid-state electrode. Results of oxacillin, ampicillin and benzylpenicillin determinations are listed in Table 6. All these drugs were determined by using an inverted all-solid-state oxacillm-CTOA electrode. The average recoveries were 100.9 + 2.9% (oxacillin), 100.7 + 2.4% (ampicillin) and 102.1 + 1.8% (benzylpenicillin). The electrode was also used for the determination of penicillin drug content in injections. The results were 99.1% (sodium benzylpenicillin), 98.9% (potassium benzylpenicillin) and 97.8% (sodium oxacillin), in agreement with the results obtained by the pharmacopoeial method’ (99.0, 98.7 and 97.9% respectively).
3. 4.
Acknowledgement-This
work was supported by the Natural Science Funds of the People’s Republic of China. REFERENCES
1. Chinese Pharmacopoeia, 3rd Ed., Vol. II, pp. 208-212.
Beijing, 1985.
8.
J. Haginaka, J. Wakai, H. Yasuda and T. Uno, Anal. Sci., 1985, 1, 73. W. J. Jusko, J. Pharm. Sci., 1971, 60, 729. B. PosuiHilova,M. Simkovi and J. KubeS. Cesk. Farm.. 1985, j4, 106: H. Much, H. J. Niclas, Th. Buchheim, B. Drescher and L. Zoelch, Pharmacie, 1985, 40, 627. U. Forsman, Anal. Chim. Acta, 1983, 146, 71. G. J. Papariello, A. K. Muhkerji and C. M. Shearer, Anal. Chem., 1973, 45, 790. S. S. M. Hassan, M. T. M. Zaki and M. H. Eldesouki,
9.
B. Karlberg and U. Forsman, Anal. Chim. Acta, 1976,
5. 6. 7.
Talanta, 1979, 26, 91. 83, 309.
10. A. Blazsek-Bodo, A. Varga and I. Kiss, Rev. Chim. (Bucharest),
1978, 29, 464.
11. L. Campanella, M. Tomassetti and
R. Sbrilli,
Ann. Ch&
(Rome), 1986, 76, 483. 12. L. CamDanella. F. Mazzei. R. Sbrilli and M. Tomassetti, J. Pharm. Biohed. Anal., 1988, 6, 299.
13. S. Z. Yao, J. Shiao and L. H. Nie, Talanfa, 1987, 34, 977.
14. S. Z. Yao and Y. C. Tang, Acta Pharm. Sinica, 1984, 19, 455.
15. S. Z. Yao, J. Shiao and L. H. Nie, Scienfia Sinica (Ser. B), 1988, 31, 1222. 16. H. Z. Gong, D. Xiao and C. L. Wang, Chem. J. Chin. Univ., 1984, 5, 264.