Research article Received: 08 August 2013,
Revised: 15 September 2013,
Accepted: 07 October 2013
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/bio.2606
Determination of ampicillin sodium using the cupric oxide nanoparticles–luminol–H2O2 chemiluminescence reaction Mortaza Iranifam* and Merhnaz Khabbaz Kharameh ABSTRACT: A simple and sensitive chemiluminescence (CL) method has been developed for the determination of ampicillin sodium at submicromolar levels. The method is based on the inhibitory effect of ampicillin sodium on the cupric oxide nanoparticles (CuO NPs)–luminol–H2O2 CL reaction. Experimental parameters affecting CL inhibition including concentrations of CuO NPs, luminol, H2O2 and NaOH were optimized. Under optimum conditions, the calibration plot was linear in the analyte concentration range 4.0 × 10-7–4.0 × 10-6 mol/L. The limit of detection was 2.6 × 10-7 mol/L and the relative standard deviation (RSD) for six replicate determinations of 1 × 10-6 mol/L ampicillin sodium was 4.71%. Also, X–ray diffraction (XRD) and transmission electron microscopy (TEM) analysis were employed to characterize the CuO NPs. The utility of the proposed method was demonstrated by determining ampicillin sodium in pharmaceutical preparation. Copyright © 2013 John Wiley & Sons, Ltd. Keywords: chemiluminescence; cupric oxide nanoparticles; ampicillin sodium; luminol; pharmaceuticals
Introduction Ampicillin sodium, a β-lactam antibiotic of the penicillin family, is the therapeutic of choice for commonly occurring bacterial infections such as ear infections, bladder infections, pneumonia, gonorrhea and Escherichia coli or Salmonella infections (1–3). It is acid resistant and therefore can be administrated orally (4). The pharmacological importance of this antibiotic and its relatively high consumption have led to the establishment of various analytical methods for its quantitative determination. The reported methods include: polarography (5), spectrofluorimetry (3,6,7), spectrophotometry (8–11), high-performance liquid chromatography (HPLC) with UV detection (12) and chemiluminescence (CL; 13,14) (Table 1). Each of the above-mentioned analytical methods for the determination of ampicillin sodium possesses its respective advantages and disadvantages. However, the need for expensive instrumentation, being timeconsuming and being of low sensitivity are some of the reported shortcomings of these methods. In general, CL is the emission of electromagnetic radiation (ultraviolet, visible or infrared) during the process of a chemical reaction (15,16). CL-reaction-based detection systems have outstanding analytical merits such as high sensitivity, wide linear range and inexpensive apparatus due to the lack of the excitation light source and spectral resolving system (17). Hence, CL approaches have found many analytical applications in fields as diverse as clinical, food, environmental and pharmaceutical analysis (18). In this regard, Iranifam (19) has reviewed the recent advance in flow-CL techniques for pharmaceutical analysis. Recently, various nanomaterials such as gold (20,21), silver (22,23), selenium (24), iron(II) and (III) (25) oxide (26,27) and cupric oxide (28,29) nanoparticles with redox catalytic properties have attracted the attention of researchers as alternatives to catalyze CL reactions and provide enhanced CL emission. In 2012, Chen et al. (28) found that cupric oxide nanoparticles
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(CuO NPs) are capable of enhancing the CL of the luminol– H2O2 system up to 400-fold. This enhancement was attributed to the peroxidase-like activity of CuO NPs (30). The CuO NPscatalyzed luminol–H2O2 CL system has been exploited for the determination of hydrogen peroxide, glucose (28) and cholesterol (29). In order to expand the analytical applications of the newly reported luminol–H2O2–CuO NPs CL system, especially in the field of pharmaceutical analysis, we conducted some preliminary tests. We found that ampicillin sodium can inhibit the CL emission of the luminol–H2O2–CuO NPs system. Based on this finding, a simple and sensitive method for the determination of ampicillin in pharmaceutical preparations was proposed. Interestingly, the limit of detection (LOD) of this method was approximately two orders of magnitude lower than those of CL methods reported to date (13,14). In addition, compared with other analytical methods (cited in Table 1), the CL method presented here needs only simple and inexpensive instrumentation.
Experimental Reagents and materials All chemicals used were of analytical grade and supplied by (Merck Millipore, Darmstadt, Germany), except amoxicillin and ampicillin which were purchased from Fluka (Hannover, Germany). All of the -4 reagents were used as received, without further purification. A 2.5 × 10 mol/L standard stock solution of luminol was prepared by dissolving 4.4 -2 mg of luminol in 100 mL of 5.0 × 10 mol/L NaOH. A 1 mol/L NaOH stock
* Correspondence to: M. Iranifam, Department of Chemistry, Faculty of Science, University of Maragheh, Maragheh, East Azerbaijan, Iran. E-mail: [email protected] Department of Chemistry, Faculty of Science, University of Maragheh, Maragheh, East Azerbaijan, Iran
Copyright © 2013 John Wiley & Sons, Ltd.
M. Iranifam and M. K. Kharameh Table 1. Analytical performance data for previously reported and proposed method for the determination of ampicillin sodium Method Spectrofluorimetry Spectrofluorimetry Spectrofluorimetry Polarography Spectrophotometery Spectrophotometery Spectrophotometery Spectrophotometery HPLC with UV detection CL CL This work
Linear range (mol/L) –6
–6
2 × 10 –10 × 10 6.7 × 10–8–2.7 × 10–6 1.3 × 10–5–1.8 × 10–4 1.1 × 10–4–9.4 × 10–3 2.0 × 10 5–6.0 × 10 4 2.1 × 10 5–8.6 × 10 5 5.4 × 10 6–2.1 × 10 4 1.9 × 10 1–1.2 1.1 × 10 6–2.7 × 10 5 5.4 × 10 5–2.7 × 10 3 4.7 × 10 5–4.7 × 10 4 4.0 × 10–7–4.0 × 10–6
Detection limit (mol/L) 4.0–5.2 × 10 5.3 × 10–8 2.7 × 10–6 NR 8.0 × 10 6 2.1 × 10 8 4.0 × 10 6 1.9 × 10 1 5.3 × 10 7 1.3 × 10 5 1.2 × 10 5 2.6 × 10–7
solution was prepared by dissolving 4 g of NaOH in 100 mL of doubledistilled water. Stock solutions of hydrogen peroxide solutions were prepared by diluting appropriate amounts of 35% H2O2 to 1 mol/L H2O2. The H2O2 solutions were freshly prepared and consumed for each experiment. A 0.02 mol/L copper(II) acetate monohydrate solution was prepared by dissolving 0.998 g of copper(II) acetate monohydrate in 250 mL of doubly distilled water. A 10 ppm CuO solution was prepared by dissolving 1 -4 mg of CuO in 100 mL of double-distilled water. A 1.4 × 10 mol/L standard stock solution of ampicilin sodium was prepared by dissolving 5.6 mg of ampicilin sodium in 100 mL of double-distilled water. Injection vials of ampicilin sodium as real samples were provided by Dana Pharmaceutical Co (Tabriz, Iran).
7
Matrix
Ref.
Pharmaceutical preparations Serum Pharmaceutical preparations and urine sample Pharmaceutical preparations and urine sample Pharmaceutical preparations Pharmaceutical preparations Pharmaceutical preparations Pharmaceutical preparations Rabbit plasma Pharmaceutical preparations Pharmaceutical preparations Pharmaceutical preparations
3 6 7 5 8 9 10 11 12 13 14 –
Sample preparation A commercial ampicillin sodium drug, AMPIVIL vial (Daana Pharma. Co), was analysed using the proposed method. The drug sample solution was prepared by dissolving the contents of three vials of drug in 100 mL of double-distilled water. The declared contents of ampicillin sodium were 1 g. Aliquots of the solution were diluted to a concentration within the calibration range for the analysis. The content of ampicillin sodium in the vial of drug was determined according to the general procedure and using a previously prepared calibration plot, or using regression equations without further treatment.
Results and discussion CL signals were monitored using a FB14 luminometer (Berthold Detection Systems, Pforzheim, Germany). To determine the crystal phase composition and average crystalline size of synthesized CuO NPs, XRD measurements were carried out at room temperature by using a Siemens D5000 (California, USA), with Cu Kα radiation. An accelerating voltage of 40 kV and emission current of 30 mA were used. The average crystalline size of the samples was calculated according to the Debye–Scherrer formula (31). TEM images of the products were obtained on a Philips CM-30 high-resolution transmission electron microscope (Eindhoven, Netherlands), employing an accelerating voltage of 150 kV.
Synthesis of CuO NPs CuO NPs were synthesized using a previously reported quick-precipitation approach (28). Briefly, 150 mL of 0.02 M copper acetate aqueous solution was mixed with 0.5 mL glacial acetic acid in a round-bottomed flask quipped with a refluxing device. The solution was heated to 100°C with vigorous stirring. Then, 10 mL of 0.04 g/mL NaOH aqueous solution was rapidly added to the boiling solution, in which a large amount of black precipitate was simultaneously produced. The precipitate was centrifuged, washed three times with absolute ethanol and dried in air at room temperature. The as-prepared CuO NPs can be easily dispersed in distilled water giving a transparent brown solution.
General procedure for CL detection CL detection was implemented in a 3 mL test tube placed in the sample -6 holder of the luminometer. Solution (0.5 mL) containing 8 × 10 mol/L -2 luminol and 5 × 10 mol/L NaOH was transferred to the test tube -7 -6 containing 1 mL of 4 × 10 –4 × 10 mol/L ampicillin sodium solution. Then, 0.5 mL of 10 ppm CuO NPs solution was added into the test tube. -7 Finally, 1 mL of 1 × 10 mol/L H2O2 solution was added to the test tube to initiate the CL reaction. The progress of the reaction was continuously monitored on a computer connected to the luminometer. Maximum CL intensity was used as analytical signal.
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XRD spectrum and TEM image of CuO NPs The XRD spectrum of the CuO NPs is shown in Fig. 1. The XRD peaks are at 2θ of 32.48°, 35.52°, 38.64°, 48.98°, 53.3°, 57.88°, 61.46°, 66.28°, 67.69°, 72.00° and 74.8°, and can be classified to the (110), (002), (111), (020), (202), (113), (022), (311), (200), (113) and (400) plane reflections. All of the peaks in the XRD diagram could be assigned to the monoclinic crystal structure of CuO NPs according to the standard powder diffraction data (JCPDS 80-1268). Peaks of impurities were not observed in the XRD pattern, thus indicatingthe high purity of the CuO NPs. The broadening of the peak indicates the small size of CuO NPs. Based on the Debye–Scherrer equation for the full-width at half-maximum (FWHM) of the (002) reflection, the average crystal size of the CuO nanoparticles is estimated to be 8 nm. 1400 (111)
1200
Intensity (a.u.)
Apparatus
(002)
1000 800 (020)
(110)
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(113) (022) (311) (200) (113) (400)
(202)
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Figure 1. XRD patterns of the synthesized CuO NPs.
Copyright © 2013 John Wiley & Sons, Ltd.
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Determination of ampicillin using CuO NPs–luminol–H2O2 CL reaction 250000 200000
ΔCL(a.u.)
The TEM image of the synthesized CuO NPs is shown in Fig. 2. As can be seen from the TEM image, the size of the CuO NPs is ~ 10 nm, which is in good agreement with that calculated by Debye– Scherrer formula from the XRD pattern.
150000 100000 50000
Principle of the CL method for ampicilin sodium
0
It is well-known that peroxidases including horseradish peroxidase (HRP) can catalyze the oxidation of a peroxidase substrate by hydrogen peroxide. In 2011, Chen et al. (30) found that CuO NPs are capable of mimicking the catalytic activity of peroxidases. It is interesting to mention that in contrast to HRP, the CuO NPs were stable over a wide range of pH from 3 to 12, and temperature from 4 to 90°C. Based on this finding, the catalytic property of CuO NPs on the luminol H2O2 CL reaction was explored and it was found that CuO NPs could remarkably increase the CL signal of the luminol H2O2 system. In the light of these features, analytical applications of the CuO NPs luminol H2O2 CL system for H2O2, glucose and cholesterol detection were successfully demonstrated (28,29). In this work, expansion of the analytical application of the CuO NPs luminol H2O2 CL system for pharmaceutical analysis was intended. To this aim, some preliminary tests were carried out and it was found that ampicillin sodium can suppress CL emission in the CuO NPs luminol H2O2 CL system. In this CL system, H2O2 plays an important role by producing superoxide and hydroxyl radicals. Therefore, it seems more likely that consumption of H2O2 by the antibiotic due to its oxidant-scavenging activity may be the main reason for attenuation of the CuO NPs–luminol–H2O2 CL system (32). The resultant decrease in the CL intensity was proportional to the ampicillin sodium concentration. Optimization of the CL reaction conditions With the view of finding the optimum CL reaction conditions at which ampicillin sodium can impose the highest attenuation on the CL system, a series of experiments was conducted. In this regard, the concentrations of chemical reagents involved in the CL reaction versus their ΔCL signals were plotted. ΔCL was defined as ΔCL = CL0 CL, where CL0 and CL are the emission intensity in the absence and presence of ampicillin sodium, respectively. It is well-known that the luminol–H2O2 CL reaction occurs in alkaline media (16). In addition, as mentioned above, it is reported that ampicillin sodium is able to scavenge H2O2. Therefore, in order to find the optimum concentration of NaOH at which ampicillin sodium has the highest scavenging activity and consequently the highest inhibitory effect on the CL system, a series of experiments was carried out. Figure 3 shows the
0
0.05
0.1
0.15
0.2
0.25
NaOH concentration (mol/L) Figure 3. The effect of NaOH concentration on the inhibitory effect of ampicillin -6 sodium on the CL reaction. Reaction conditions: ampicillin sodium, 1.0 × 10 mol/ -6 -6 L; luminol, 2.5 × 10 mol/L; H2O2, 1.0 × 10 mol/L; CuO, 20 mg/L.
effect of NaOH concentration on the inhibitory effect of ampicillin sodium. Based on this data, 5.0 × 10-2 mol/L was chosen as the most suitable NaOH concentration. The effect of luminol concentration on the ΔCL intensity is presented in Fig. 4. According to this figure, the ΔCL signal reached a maximum at 8.0 × 10-6 mol/L and then remained fairly constant. Therefore, 8.0 × 10-6 mol/L was chosen for subsequent studies. Figure 5 demonstrates the influence of H2O2 concentration on the inhibitory effect of ampicillin sodium. As can be seen, the ΔCL signal increased with increasing H2O2 concentration up to 1.0 × 10-7 mol/L and then decreased at higher concentrations. Therefore, 1.0 × 10-7 mol/L H2O2 was chosen as an optimum value. In this respect, hydroxyl and superoxide radicals possessing critical roles in the CL system are generated by radical decomposition of H2O2, but H2O2 is also a powerful •OH scavenger. It seems that in this system at higher than 1.0 × 10-7 mol/L, its radical scavenging counteracts its positive role as the radical source for the reaction (17). The effect of CuO NPs concentration on the ΔCL signal was also investigated. The results are shown graphically in Fig. 6. As can be seen, 10 mg/L CuO NPs leads to
Figure 4. The effect of luminol concentration on the inhibitory effect of ampicillin -6 sodium on the CL reaction. Reaction conditions: ampicillin sodium, 1.0 × 10 mol/ -2 -6 L; NaOH, 5.0 × 10 mol/L; H2O2, 1.0 × 10 mol/L; CuO, 20 mg/L.
600000
ΔCL (a.u.)
500000 400000 300000 200000 100000 0 0
0.000002 0.000004 0.000006 0.000008
0.00001
0.000012
Hydrogen peroxide concentration (mol/L)
Figure 2. TEM image of the synthesized CuO NPs.
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Figure 5. The effect of H2O2 concentration on the inhibitory effect of ampicillin -6 sodium on the CL reaction. Reaction conditions: ampicillin sodium, 1.0 × 10 -2 -6 mol/L; NaOH, 5.0 × 10 mol/L; luminol, 8.0 × 10 mol/L; CuO, 20 mg/L.
Copyright © 2013 John Wiley & Sons, Ltd.
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M. Iranifam and M. K. Kharameh 400000
Table 3. Determination of ampicillin sodium in ampicilin 1g vials for injection
350000
ΔCL(a.u.)
300000 250000
Found (mol/L)a,b
200000 150000 100000 50000 0 4
6
8
10
12
14
16
CuO NPs concentration (mg/L)
6.6 8.2 1.1 2.0
(± 0.3) (± 0.3) (± 0.1) (± 0.1)
× × × ×
-7
10 10-7 10-6 10-6
Added (mol/L)
Recovery (%)
_ 2 × 10-7 4 × 10-7 1.4 × 10-6
_ 95.8 102.88 103.36
a
Figure 6. The effect of CuO concentration on the inhibitory effect of ampicillin so-6 dium on the CL reaction. Reaction conditions: ampicillin sodium, 1.0 × 10 mol/L; -2 -6 -7 NaOH, 5.0 × 10 mol/L; luminol, 8.0 × 10 mol/L; H2O2, 1.0 × 10 mol/L.
highest ΔCL signal and thus was chosen as the most suitable concentration. Partial absorption of the light emanating from the CL system by CuO NPs at concentrations > 10 mg/L may be the possible reason for the decreasing CL intensity and consequently decreasing sensitivity of the CL system to the drug.
Analytical parameters Under optimum experimental conditions, a calibration curve was plotted for a series of six standard solutions. The calibration curve was linear over an analyte concentration range of 4.0 × 10-7 to 4.0 × 10-6 mol/L. The equation for the calibration curve is: Y = -8 × 10+10 X + 398092 (R2 = 0.999), where Y = CL signal and X = ampicillin sodium concentration (mol/L). After IUPAC, the LOD is defined as: CLOD = analyte concentration giving a signal equal to the blank – 3 SD of the blank signal. The estimated CLOD was 2.6 × 10-7 mol/L. The relative standard deviation (RSD) calculated for six replicate determinations of 1.0 × 10-6 mol/L ampicillin sodium was 4.71%.
Interference The influence of foreign species on the determination of a 1.0 × 10-6 mol/L ampicillin sodium solution was examined. A foreign ion was considered to interfere seriously when it produced a determination error > 5%. The results of interference studies are presented in Table 2. According to the manufacturer’s specifications, no excipients are used in ampicillin sodium vials for injection. Based on these results, one can conclude that the CL method provides selective determination of ampicillin sodium in the pharmaceutical preparations.
Table 2. Tolerable concentration ratios with respect to 1.0 × 10-6 mol/L of ampicillin sodium Species
Tolerable concentration ratio [Cinterferent (mol/L)/C ampicillin sodium (mol/L)]
2K+, Na+, Cl-, PO34 , SO4 2+ Ca Mg2+ Fe3+,H2Y22CO23 , SO3
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1000 100 20 5 1
The sample solution were diluted to the concentration within the calibration range for the analysis. b Mean of three replicate determinations ± SD.
Analytical application The proposed method was successfully exploited for the measurement of ampicillin sodium in pharmaceutical preparations. To evaluate the accuracy of the method, recovery experiments were performed. The accuracy of the method was investigated by carrying out recovery experiments for spiked sample solutions. Recovery ranged from 95 to 105%, revealing sufficient accuracy (Table 3).
Conclusions It was found that ampicillin sodium can inhibit the light emission elicited from the CL reaction of luminol–H2O2–CuO. Based on this finding, a simple and sensitive CL method for the determination of ampicillin sodium was proposed. The applicability of the method was successfully validated by analysis of ampicillin sodium in a pharmaceutical preparation. Acknowledgments Authors make a point of their sincere thanks to the University of Maragheh for the financial support backing this project. They would also like to thank Dr. Mostafa Eskandari for his help in taking TEM image.
References 1. Adnan S, Paterson DL, Lipman J, Roberts JA. Ampicillin/sulbactam: its potential use in treating infections in critically ill patients. Int J Antimicrob Agent 2013;42:384–389. 2. Rice L. Emergence of vancomycin-resistant enterococci. Emerg Infect Dis 2001;7:183. 3. Fernandez-Gonzalez A, Badia R, Diaz-Garcia M. Micelle-mediated spectrofluorimetric determination of ampicillin based on metal ion-catalysed hydrolysis. Anal Chim Acta 2003;484:223–31. 4. Anal AK, Stevens WF. Chitosan–alginate multilayer beads for controlled release of ampicillin. Int J Pharm 2005;290:45–54. 5. Sayed GE, Amin A, Issa Y. DC polarographic determination of ampicillin in pharmaceutical dosage forms. Anal Lett 1994;27:2515–21. 6. Izquierdo P, Gomez-Hens A, Perez-Bendito D. Stopped-flow fluorimetric determination of ampicillin in serum. Fres J Anal Chem 1992;342:606–8. 7. Xiao Y, Wang HY, Han J. Simultaneous determination of carvedilol and ampicillin sodium by synchronous fluorimetry. Spectrochim Acta A 2005;61:567–73. 8. Garcia M, Sanchez-Pedreno C, Albero M, Rodenas V. Determination of ampicillin or amoxycillin in pharmaceutical samples by flow injection analysis. J Pharm Biomed Anal 1994;12:1585. 9. Ahmad AS, Rahman N, Islam F. Spectrophotometric determination of ampicillin, amoxycillin, and carbenicillin using Folin–Ciocalteu phenol reagent. J Anal Chem 2004;59:119–23.
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Determination of ampicillin using CuO NPs–luminol–H2O2 CL reaction 10. Xu L, Wang H, Xiao Y. Spectrophotometric determination of ampicillin sodium in pharmaceutical products using sodium 1,2-naphthoquinone-4-sulfonic as the chromogentic reagent. Spectrochim Acta A 2004;60:3007–12. 11. Al-Momani I. Flow-injection spectrophotometric determination of amoxcillin, cephalexin, ampicillin, and cephradine in pharmaceutical formulations. Anal Lett 2004;37:2099–110. 12. Tolhurst T, Negrusz A, Libelt B, Woods E, Levine B. Determination of ampicillin in New Zealand white rabbit plasma using column switching technique and HPLC. Chromatographia 1996;42:223–6. 13. Li YH, Tang YH, Yao H, Fu JM. Determination of ampicillin and amoxycillin by flow injection chemiluminescence method based on their enhancing effects on the luminol–periodate reaction. Luminescence 2003;18:313–17. 14. Sorouraddin MH, Iranifam M, Imani-Nabiyyi A. Study of the enhancement of a new chemiluminescence reaction and its application to determination of beta-lactam antibiotics. Luminescence 2009;24:102–7. 15. Sorouraddin MH, Iranifam M, Imani-Nabiyyi A. A novel captopril chemiluminescence system for determination of copper(II) in human hair and cereal flours. J Fluoresc 2009;19:575–81. 16. Iranifam M, Segundo MA, Santos JLM, Lima JLFC, Sorouraddin MH. Oscillating chemiluminescence systems: state of the art. Luminescence 2010;25:409–18. 17. Sorouraddin MH, Iranifam M, Imani-Nabiyyi A. Determination of penicillin V potassium in pharmaceuticals and spiked human urine by chemiluminescence. Cent Eur J Chem 2009;7:143–7. 18. Iranifam M. Flow analysis and chemiluminescence: an update. Advances in flow-chemiluminescence analysis. Saarbrücken: LAP LAMBERT, 2011:116. 19. Iranifam M. Revisiting flow-chemiluminescence techniques: pharmaceutical analysis. Luminescence 2012; http://dx.doi.org/10.1002/ bio.2441. 20. Zhang ZF, Cui H, Lai CZ, Liu LJ. Gold nanoparticle-catalyzed luminol chemiluminescence and its analytical applications. Anal Chem 2005;77:3324–9. 21. Wang L, Yang P, Li YX, Chen HQ, Li MG, Luo FB. A flow injection chemiluminescence method for the determination of
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Copyright © 2013 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/luminescence
Revised: 15 September 2013,
Accepted: 07 October 2013
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/bio.2606
Determination of ampicillin sodium using the cupric oxide nanoparticles–luminol–H2O2 chemiluminescence reaction Mortaza Iranifam* and Merhnaz Khabbaz Kharameh ABSTRACT: A simple and sensitive chemiluminescence (CL) method has been developed for the determination of ampicillin sodium at submicromolar levels. The method is based on the inhibitory effect of ampicillin sodium on the cupric oxide nanoparticles (CuO NPs)–luminol–H2O2 CL reaction. Experimental parameters affecting CL inhibition including concentrations of CuO NPs, luminol, H2O2 and NaOH were optimized. Under optimum conditions, the calibration plot was linear in the analyte concentration range 4.0 × 10-7–4.0 × 10-6 mol/L. The limit of detection was 2.6 × 10-7 mol/L and the relative standard deviation (RSD) for six replicate determinations of 1 × 10-6 mol/L ampicillin sodium was 4.71%. Also, X–ray diffraction (XRD) and transmission electron microscopy (TEM) analysis were employed to characterize the CuO NPs. The utility of the proposed method was demonstrated by determining ampicillin sodium in pharmaceutical preparation. Copyright © 2013 John Wiley & Sons, Ltd. Keywords: chemiluminescence; cupric oxide nanoparticles; ampicillin sodium; luminol; pharmaceuticals
Introduction Ampicillin sodium, a β-lactam antibiotic of the penicillin family, is the therapeutic of choice for commonly occurring bacterial infections such as ear infections, bladder infections, pneumonia, gonorrhea and Escherichia coli or Salmonella infections (1–3). It is acid resistant and therefore can be administrated orally (4). The pharmacological importance of this antibiotic and its relatively high consumption have led to the establishment of various analytical methods for its quantitative determination. The reported methods include: polarography (5), spectrofluorimetry (3,6,7), spectrophotometry (8–11), high-performance liquid chromatography (HPLC) with UV detection (12) and chemiluminescence (CL; 13,14) (Table 1). Each of the above-mentioned analytical methods for the determination of ampicillin sodium possesses its respective advantages and disadvantages. However, the need for expensive instrumentation, being timeconsuming and being of low sensitivity are some of the reported shortcomings of these methods. In general, CL is the emission of electromagnetic radiation (ultraviolet, visible or infrared) during the process of a chemical reaction (15,16). CL-reaction-based detection systems have outstanding analytical merits such as high sensitivity, wide linear range and inexpensive apparatus due to the lack of the excitation light source and spectral resolving system (17). Hence, CL approaches have found many analytical applications in fields as diverse as clinical, food, environmental and pharmaceutical analysis (18). In this regard, Iranifam (19) has reviewed the recent advance in flow-CL techniques for pharmaceutical analysis. Recently, various nanomaterials such as gold (20,21), silver (22,23), selenium (24), iron(II) and (III) (25) oxide (26,27) and cupric oxide (28,29) nanoparticles with redox catalytic properties have attracted the attention of researchers as alternatives to catalyze CL reactions and provide enhanced CL emission. In 2012, Chen et al. (28) found that cupric oxide nanoparticles
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(CuO NPs) are capable of enhancing the CL of the luminol– H2O2 system up to 400-fold. This enhancement was attributed to the peroxidase-like activity of CuO NPs (30). The CuO NPscatalyzed luminol–H2O2 CL system has been exploited for the determination of hydrogen peroxide, glucose (28) and cholesterol (29). In order to expand the analytical applications of the newly reported luminol–H2O2–CuO NPs CL system, especially in the field of pharmaceutical analysis, we conducted some preliminary tests. We found that ampicillin sodium can inhibit the CL emission of the luminol–H2O2–CuO NPs system. Based on this finding, a simple and sensitive method for the determination of ampicillin in pharmaceutical preparations was proposed. Interestingly, the limit of detection (LOD) of this method was approximately two orders of magnitude lower than those of CL methods reported to date (13,14). In addition, compared with other analytical methods (cited in Table 1), the CL method presented here needs only simple and inexpensive instrumentation.
Experimental Reagents and materials All chemicals used were of analytical grade and supplied by (Merck Millipore, Darmstadt, Germany), except amoxicillin and ampicillin which were purchased from Fluka (Hannover, Germany). All of the -4 reagents were used as received, without further purification. A 2.5 × 10 mol/L standard stock solution of luminol was prepared by dissolving 4.4 -2 mg of luminol in 100 mL of 5.0 × 10 mol/L NaOH. A 1 mol/L NaOH stock
* Correspondence to: M. Iranifam, Department of Chemistry, Faculty of Science, University of Maragheh, Maragheh, East Azerbaijan, Iran. E-mail: [email protected] Department of Chemistry, Faculty of Science, University of Maragheh, Maragheh, East Azerbaijan, Iran
Copyright © 2013 John Wiley & Sons, Ltd.
M. Iranifam and M. K. Kharameh Table 1. Analytical performance data for previously reported and proposed method for the determination of ampicillin sodium Method Spectrofluorimetry Spectrofluorimetry Spectrofluorimetry Polarography Spectrophotometery Spectrophotometery Spectrophotometery Spectrophotometery HPLC with UV detection CL CL This work
Linear range (mol/L) –6
–6
2 × 10 –10 × 10 6.7 × 10–8–2.7 × 10–6 1.3 × 10–5–1.8 × 10–4 1.1 × 10–4–9.4 × 10–3 2.0 × 10 5–6.0 × 10 4 2.1 × 10 5–8.6 × 10 5 5.4 × 10 6–2.1 × 10 4 1.9 × 10 1–1.2 1.1 × 10 6–2.7 × 10 5 5.4 × 10 5–2.7 × 10 3 4.7 × 10 5–4.7 × 10 4 4.0 × 10–7–4.0 × 10–6
Detection limit (mol/L) 4.0–5.2 × 10 5.3 × 10–8 2.7 × 10–6 NR 8.0 × 10 6 2.1 × 10 8 4.0 × 10 6 1.9 × 10 1 5.3 × 10 7 1.3 × 10 5 1.2 × 10 5 2.6 × 10–7
solution was prepared by dissolving 4 g of NaOH in 100 mL of doubledistilled water. Stock solutions of hydrogen peroxide solutions were prepared by diluting appropriate amounts of 35% H2O2 to 1 mol/L H2O2. The H2O2 solutions were freshly prepared and consumed for each experiment. A 0.02 mol/L copper(II) acetate monohydrate solution was prepared by dissolving 0.998 g of copper(II) acetate monohydrate in 250 mL of doubly distilled water. A 10 ppm CuO solution was prepared by dissolving 1 -4 mg of CuO in 100 mL of double-distilled water. A 1.4 × 10 mol/L standard stock solution of ampicilin sodium was prepared by dissolving 5.6 mg of ampicilin sodium in 100 mL of double-distilled water. Injection vials of ampicilin sodium as real samples were provided by Dana Pharmaceutical Co (Tabriz, Iran).
7
Matrix
Ref.
Pharmaceutical preparations Serum Pharmaceutical preparations and urine sample Pharmaceutical preparations and urine sample Pharmaceutical preparations Pharmaceutical preparations Pharmaceutical preparations Pharmaceutical preparations Rabbit plasma Pharmaceutical preparations Pharmaceutical preparations Pharmaceutical preparations
3 6 7 5 8 9 10 11 12 13 14 –
Sample preparation A commercial ampicillin sodium drug, AMPIVIL vial (Daana Pharma. Co), was analysed using the proposed method. The drug sample solution was prepared by dissolving the contents of three vials of drug in 100 mL of double-distilled water. The declared contents of ampicillin sodium were 1 g. Aliquots of the solution were diluted to a concentration within the calibration range for the analysis. The content of ampicillin sodium in the vial of drug was determined according to the general procedure and using a previously prepared calibration plot, or using regression equations without further treatment.
Results and discussion CL signals were monitored using a FB14 luminometer (Berthold Detection Systems, Pforzheim, Germany). To determine the crystal phase composition and average crystalline size of synthesized CuO NPs, XRD measurements were carried out at room temperature by using a Siemens D5000 (California, USA), with Cu Kα radiation. An accelerating voltage of 40 kV and emission current of 30 mA were used. The average crystalline size of the samples was calculated according to the Debye–Scherrer formula (31). TEM images of the products were obtained on a Philips CM-30 high-resolution transmission electron microscope (Eindhoven, Netherlands), employing an accelerating voltage of 150 kV.
Synthesis of CuO NPs CuO NPs were synthesized using a previously reported quick-precipitation approach (28). Briefly, 150 mL of 0.02 M copper acetate aqueous solution was mixed with 0.5 mL glacial acetic acid in a round-bottomed flask quipped with a refluxing device. The solution was heated to 100°C with vigorous stirring. Then, 10 mL of 0.04 g/mL NaOH aqueous solution was rapidly added to the boiling solution, in which a large amount of black precipitate was simultaneously produced. The precipitate was centrifuged, washed three times with absolute ethanol and dried in air at room temperature. The as-prepared CuO NPs can be easily dispersed in distilled water giving a transparent brown solution.
General procedure for CL detection CL detection was implemented in a 3 mL test tube placed in the sample -6 holder of the luminometer. Solution (0.5 mL) containing 8 × 10 mol/L -2 luminol and 5 × 10 mol/L NaOH was transferred to the test tube -7 -6 containing 1 mL of 4 × 10 –4 × 10 mol/L ampicillin sodium solution. Then, 0.5 mL of 10 ppm CuO NPs solution was added into the test tube. -7 Finally, 1 mL of 1 × 10 mol/L H2O2 solution was added to the test tube to initiate the CL reaction. The progress of the reaction was continuously monitored on a computer connected to the luminometer. Maximum CL intensity was used as analytical signal.
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XRD spectrum and TEM image of CuO NPs The XRD spectrum of the CuO NPs is shown in Fig. 1. The XRD peaks are at 2θ of 32.48°, 35.52°, 38.64°, 48.98°, 53.3°, 57.88°, 61.46°, 66.28°, 67.69°, 72.00° and 74.8°, and can be classified to the (110), (002), (111), (020), (202), (113), (022), (311), (200), (113) and (400) plane reflections. All of the peaks in the XRD diagram could be assigned to the monoclinic crystal structure of CuO NPs according to the standard powder diffraction data (JCPDS 80-1268). Peaks of impurities were not observed in the XRD pattern, thus indicatingthe high purity of the CuO NPs. The broadening of the peak indicates the small size of CuO NPs. Based on the Debye–Scherrer equation for the full-width at half-maximum (FWHM) of the (002) reflection, the average crystal size of the CuO nanoparticles is estimated to be 8 nm. 1400 (111)
1200
Intensity (a.u.)
Apparatus
(002)
1000 800 (020)
(110)
600
(113) (022) (311) (200) (113) (400)
(202)
400 200 0 20
25
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35
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Figure 1. XRD patterns of the synthesized CuO NPs.
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Luminescence 2013
Determination of ampicillin using CuO NPs–luminol–H2O2 CL reaction 250000 200000
ΔCL(a.u.)
The TEM image of the synthesized CuO NPs is shown in Fig. 2. As can be seen from the TEM image, the size of the CuO NPs is ~ 10 nm, which is in good agreement with that calculated by Debye– Scherrer formula from the XRD pattern.
150000 100000 50000
Principle of the CL method for ampicilin sodium
0
It is well-known that peroxidases including horseradish peroxidase (HRP) can catalyze the oxidation of a peroxidase substrate by hydrogen peroxide. In 2011, Chen et al. (30) found that CuO NPs are capable of mimicking the catalytic activity of peroxidases. It is interesting to mention that in contrast to HRP, the CuO NPs were stable over a wide range of pH from 3 to 12, and temperature from 4 to 90°C. Based on this finding, the catalytic property of CuO NPs on the luminol H2O2 CL reaction was explored and it was found that CuO NPs could remarkably increase the CL signal of the luminol H2O2 system. In the light of these features, analytical applications of the CuO NPs luminol H2O2 CL system for H2O2, glucose and cholesterol detection were successfully demonstrated (28,29). In this work, expansion of the analytical application of the CuO NPs luminol H2O2 CL system for pharmaceutical analysis was intended. To this aim, some preliminary tests were carried out and it was found that ampicillin sodium can suppress CL emission in the CuO NPs luminol H2O2 CL system. In this CL system, H2O2 plays an important role by producing superoxide and hydroxyl radicals. Therefore, it seems more likely that consumption of H2O2 by the antibiotic due to its oxidant-scavenging activity may be the main reason for attenuation of the CuO NPs–luminol–H2O2 CL system (32). The resultant decrease in the CL intensity was proportional to the ampicillin sodium concentration. Optimization of the CL reaction conditions With the view of finding the optimum CL reaction conditions at which ampicillin sodium can impose the highest attenuation on the CL system, a series of experiments was conducted. In this regard, the concentrations of chemical reagents involved in the CL reaction versus their ΔCL signals were plotted. ΔCL was defined as ΔCL = CL0 CL, where CL0 and CL are the emission intensity in the absence and presence of ampicillin sodium, respectively. It is well-known that the luminol–H2O2 CL reaction occurs in alkaline media (16). In addition, as mentioned above, it is reported that ampicillin sodium is able to scavenge H2O2. Therefore, in order to find the optimum concentration of NaOH at which ampicillin sodium has the highest scavenging activity and consequently the highest inhibitory effect on the CL system, a series of experiments was carried out. Figure 3 shows the
0
0.05
0.1
0.15
0.2
0.25
NaOH concentration (mol/L) Figure 3. The effect of NaOH concentration on the inhibitory effect of ampicillin -6 sodium on the CL reaction. Reaction conditions: ampicillin sodium, 1.0 × 10 mol/ -6 -6 L; luminol, 2.5 × 10 mol/L; H2O2, 1.0 × 10 mol/L; CuO, 20 mg/L.
effect of NaOH concentration on the inhibitory effect of ampicillin sodium. Based on this data, 5.0 × 10-2 mol/L was chosen as the most suitable NaOH concentration. The effect of luminol concentration on the ΔCL intensity is presented in Fig. 4. According to this figure, the ΔCL signal reached a maximum at 8.0 × 10-6 mol/L and then remained fairly constant. Therefore, 8.0 × 10-6 mol/L was chosen for subsequent studies. Figure 5 demonstrates the influence of H2O2 concentration on the inhibitory effect of ampicillin sodium. As can be seen, the ΔCL signal increased with increasing H2O2 concentration up to 1.0 × 10-7 mol/L and then decreased at higher concentrations. Therefore, 1.0 × 10-7 mol/L H2O2 was chosen as an optimum value. In this respect, hydroxyl and superoxide radicals possessing critical roles in the CL system are generated by radical decomposition of H2O2, but H2O2 is also a powerful •OH scavenger. It seems that in this system at higher than 1.0 × 10-7 mol/L, its radical scavenging counteracts its positive role as the radical source for the reaction (17). The effect of CuO NPs concentration on the ΔCL signal was also investigated. The results are shown graphically in Fig. 6. As can be seen, 10 mg/L CuO NPs leads to
Figure 4. The effect of luminol concentration on the inhibitory effect of ampicillin -6 sodium on the CL reaction. Reaction conditions: ampicillin sodium, 1.0 × 10 mol/ -2 -6 L; NaOH, 5.0 × 10 mol/L; H2O2, 1.0 × 10 mol/L; CuO, 20 mg/L.
600000
ΔCL (a.u.)
500000 400000 300000 200000 100000 0 0
0.000002 0.000004 0.000006 0.000008
0.00001
0.000012
Hydrogen peroxide concentration (mol/L)
Figure 2. TEM image of the synthesized CuO NPs.
Luminescence 2013
Figure 5. The effect of H2O2 concentration on the inhibitory effect of ampicillin -6 sodium on the CL reaction. Reaction conditions: ampicillin sodium, 1.0 × 10 -2 -6 mol/L; NaOH, 5.0 × 10 mol/L; luminol, 8.0 × 10 mol/L; CuO, 20 mg/L.
Copyright © 2013 John Wiley & Sons, Ltd.
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M. Iranifam and M. K. Kharameh 400000
Table 3. Determination of ampicillin sodium in ampicilin 1g vials for injection
350000
ΔCL(a.u.)
300000 250000
Found (mol/L)a,b
200000 150000 100000 50000 0 4
6
8
10
12
14
16
CuO NPs concentration (mg/L)
6.6 8.2 1.1 2.0
(± 0.3) (± 0.3) (± 0.1) (± 0.1)
× × × ×
-7
10 10-7 10-6 10-6
Added (mol/L)
Recovery (%)
_ 2 × 10-7 4 × 10-7 1.4 × 10-6
_ 95.8 102.88 103.36
a
Figure 6. The effect of CuO concentration on the inhibitory effect of ampicillin so-6 dium on the CL reaction. Reaction conditions: ampicillin sodium, 1.0 × 10 mol/L; -2 -6 -7 NaOH, 5.0 × 10 mol/L; luminol, 8.0 × 10 mol/L; H2O2, 1.0 × 10 mol/L.
highest ΔCL signal and thus was chosen as the most suitable concentration. Partial absorption of the light emanating from the CL system by CuO NPs at concentrations > 10 mg/L may be the possible reason for the decreasing CL intensity and consequently decreasing sensitivity of the CL system to the drug.
Analytical parameters Under optimum experimental conditions, a calibration curve was plotted for a series of six standard solutions. The calibration curve was linear over an analyte concentration range of 4.0 × 10-7 to 4.0 × 10-6 mol/L. The equation for the calibration curve is: Y = -8 × 10+10 X + 398092 (R2 = 0.999), where Y = CL signal and X = ampicillin sodium concentration (mol/L). After IUPAC, the LOD is defined as: CLOD = analyte concentration giving a signal equal to the blank – 3 SD of the blank signal. The estimated CLOD was 2.6 × 10-7 mol/L. The relative standard deviation (RSD) calculated for six replicate determinations of 1.0 × 10-6 mol/L ampicillin sodium was 4.71%.
Interference The influence of foreign species on the determination of a 1.0 × 10-6 mol/L ampicillin sodium solution was examined. A foreign ion was considered to interfere seriously when it produced a determination error > 5%. The results of interference studies are presented in Table 2. According to the manufacturer’s specifications, no excipients are used in ampicillin sodium vials for injection. Based on these results, one can conclude that the CL method provides selective determination of ampicillin sodium in the pharmaceutical preparations.
Table 2. Tolerable concentration ratios with respect to 1.0 × 10-6 mol/L of ampicillin sodium Species
Tolerable concentration ratio [Cinterferent (mol/L)/C ampicillin sodium (mol/L)]
2K+, Na+, Cl-, PO34 , SO4 2+ Ca Mg2+ Fe3+,H2Y22CO23 , SO3
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1000 100 20 5 1
The sample solution were diluted to the concentration within the calibration range for the analysis. b Mean of three replicate determinations ± SD.
Analytical application The proposed method was successfully exploited for the measurement of ampicillin sodium in pharmaceutical preparations. To evaluate the accuracy of the method, recovery experiments were performed. The accuracy of the method was investigated by carrying out recovery experiments for spiked sample solutions. Recovery ranged from 95 to 105%, revealing sufficient accuracy (Table 3).
Conclusions It was found that ampicillin sodium can inhibit the light emission elicited from the CL reaction of luminol–H2O2–CuO. Based on this finding, a simple and sensitive CL method for the determination of ampicillin sodium was proposed. The applicability of the method was successfully validated by analysis of ampicillin sodium in a pharmaceutical preparation. Acknowledgments Authors make a point of their sincere thanks to the University of Maragheh for the financial support backing this project. They would also like to thank Dr. Mostafa Eskandari for his help in taking TEM image.
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