Keywords
RP-HPLC; Amoxicillin (AMX); Quality control level; Isocratic mode
Abstract
A novel, simple and economic Reverse Phase High Performance Liquid Chromatography (RP-HPLC) method has been developed for the quantification of Amoxicillin (AMX) in bulk and tablet dosage form with greater precision and accuracy. Separation was achieved on Hypersil ODS C18 (250mm×4.6×5micron) column in isocratic mode with mobile phase consisting of Acetonitrile: 0.2M Potassium dihydrogen phosphate buffer (pH 5) (1:99v/v) and conditions optimized with flow rate of 1 ml/minute and wavelength of detection at 254 nm. The retention time of Amoxicillin (AMX) was found to be 6.992 min. The method was validated as per ICH guidelines. Linearity was established for Amoxicillin (AMX) in the range0.6 – 3.4 μg / ml with R2 value 1. The percentage recovery of Amoxicillin (AMX) was found to be in the range 98.87-99.87 %. The high recovery and low relative standard deviation confirm the suitability of the proposed method for the estimation of the drug in bulk and marketed dosage form. Validation studies demonstrated that the proposed RP-HPLC method is simple, specific, rapid, reliable and reproducible for the determination of Amoxicillin for Quality Control level.
Citation
Sahoo NK, Sahu M, Algarsamy V, Srividya B and Sahoo CK. Validation of Assay Indicating Method Development of Amoxicillin in Bulk and One of Its Marketed Dosage Form by RP-HPLC. Ann Chromatogr Sep Tech. 2016; 2(1): 1014.
Introduction
Amoxicillin (AMX), shown in Figure 1,is (2S.5R.6R)-6-{[(2R)-2-amino-2-(4-hydroxy phenyl)-acetyl]amino}-3, 3-dimethyl-7-oxo-4-thia-l-azabicyclo [3.2.0] heptane-2-carboxylic acid.
Figure 1: Chemical Structure of Amoxicillin.
Amoxicillin is a moderate-spectrum, bacteriolytic, β-lactam antibiotic used to treat bacterial infections caused by susceptible microorganisms. It is usually the drug of choice within the class because it is better absorbed, following oral administration, than other β-lactam antibiotics.It is a semi synthetic antibiotic, an analog of Ampicillin with a broad spectrum of bactericidal activity against many gram- positive and gram-negative microorganisms [1,2]. Amoxicillin is susceptible to degradation by β-lactamase producing bacteria, which are resistant to a broad spectrum of β-lactam antibiotics, such as pencillin.For this reason, it is often combined with clavulanic acid, a β-lactamase inhibitor [3].Several analytical methods for the determination of amoxicillin by capillary electrophoresis [4],spectrophotometry [5],HPLC [6-11] and HPTLC [12] have been reported.The aim of the present work was to develop and validate a sensitive RP-HPLC method that can be implemented for the quantification of Amoxicillin in bulk as well as in its tablet dosage forms.
Experimental
Materials
Pure Amoxicillin (AMX) used as working standards, was purchased from Yarrow chem. Products, Mumbai, India.Tablets containing 500 mg of Amoxicillin (GERMATIN) was obtained from Apollo Pharmaceuticals Pvt. Ltd, Visakhapatnam, India and used within their shelf life period. Acetonitrile and water (HPLC-grade) were purchased from Merck,India. All other chemicals and reagents employed were of analytical grade, and purchased from Merck,India.
Instrumentation
Shimadzu 1800 UV-visible spectrophotometer (Hyderabad), Ultrasonicator,0.45µm membrane f ilter, Sartorius Analytical balance, Shimadzu HPLC system,LC Solution soft ware having the configurations, Solvent degasser DCU-20A3 Solvent degasser,Prominence 10 AT vp binary gradient pumps, SPD 10 A VP UV-VIS detector with class VP software,Columns of Hypersil ODS C18 250mm×4.6×5micron were used in this study.A Wenster digital pH meter was used for pH adjustment.
Chromatographic conditions
The selected and optimized mobile phase composed of Acetonitrile:Potassium dihydrogen phosphate buffer (pH 5) (1:99v/v) and conditions optimized were with flow rate of 1 ml/minute, wavelength at 254 nm and Run time of 20 min. Here the peaks were separated and showed better resolution, appreciable theoretical plate counts and good peak symmetry. The proposed chromatographic conditions were found appropriate for the quantitative determination of the present drug Table 1.
Table 1: Optimization of chromatographic conditions.
| Trials | Column | Mobile phase | Flow rate | Wave length | Observation | Results |
| 1 | Hypersil ODS, C18 column. | 10:90 Acetonitrile and buffer of ph-6 | 1.5ml | 254nm | Peak fronting and Splitting was | Rejected |
| observed | ||||||
| 2 | Hypersil ODS, C18 column. | 10:90 Acetonitrile and buffer of ph-6 | 1ml | 254nm | Tailing was | Rejected |
| Observed | ||||||
| 3 | Hypersil ODS, C18 column. | 1:99 Acetonitrile and buffer of ph-6 | 1ml | 254nm | Tailing was observed | Rejected |
| 4 | Hypersil ODS, C18 column. | 1:99 Acetonitrile and Phosphate buffer of pH-5 | 1ml | 254nm | Good peak was observed | Accepted |
Preparation of mobile phase
Mobile phase was prepared by taking Acetonitrile: 0.2 M Potassium di hydrogen phosphate buffer (pH 5) (1:99 v/v).Mobile phase was filtered through 0.45 µm membrane filter and degassed under ultrasonic bath prior to use. The mobile phase was pumped through the column at a flow rate of 1 ml/min.
Preparation of standard solutions
Dissolve 30 mg of amoxicillin working standard in mobile phase and dilute to 50 ml with the same mobile phase. One ml was diluted to 20ml with mobile. Diluted to 1ml of this solution to 50ml with mobile phase. Finally this gave 0.6 ppm solution, then the solution was filtered through the 0.45 µm membrane filter and degassed under ultrasonic bath prior to use. The solution was injected into the HPLC system.
Assay of Amoxicillin from Marketed tablets
Twenty tablets (GERMATIN tablet contains: Amoxicillin 500 mg) was weighed accurately, average weight was calculated.Then powder equivalent to 50 mg was taken in a 50ml volumetric flask.Then 20ml of mobile phase was added and kept for 15mins with occasional shaking.Then 10 ml of Glacial acetic acid was added.Then volume was made to 50ml followed by sonication for 15mins.Then whole of the solution was filtered with 0.45µ filter paper. From the filterate 10 ml was taken and made to 100ml with the mobile phase.Finally 1ml of the above solution was taken in 10ml volumetric flask and made up to volume with mobile phase and injected into RP-HPLC system.Then Assay was carried out for the amount of amoxicillin content.
Method Validation
The method was validated in accordance with ICH guidelines [13]. The parameters assessed were linearity, accuracy, and precision, reproducibility, robustness and system suitability.
Accuracy Accuracy was best determined by the standard addition method. Previously analyzed samples of Amoxicillin API were added with standard drug solutions and are analyzed by the proposed method. Recovery (%), RSD (%) and bias (%) were calculated for each concentration.
Accuracy is reported as percentage bias,which is calculated from the expression
Precision
System precision: Standard solution prepared as per test method and injected six times and the %RSD value was calculated.
Method precision: Six preparations individually using single batch of Amoxicillin drug substance were prepared as per test method and injected each solution induplicate on the same day in to HPLC. % RSD value was calculated to determine intra-day precision.
Ruggedness/Inter day precision: Six preparations individually using single batch of Amoxicillin drug substance as per test method and injected each solution induplicate on the same day in to HPLC using different column, system and analysts on different days. And %RSD value was calculated to determine inter-day precision.
Robustness
The concept of robustness of an analytical procedure has been defined by the ICH as “a measure of its capacity to remain unaffected by small but deliberate variations in method parameters”. To determine the robustness of the method experimental conditions are purposely altered and chromatographic characters are evaluated. Influence of small changes in chromatographic conditions such as change in flow rate (± 0.1ml/min), wavelength of detection (±2nm) and acetonitrile content in mobile phase (±2%) were studied to determine the robustness of the method.
Limit of Detection (LOD)
The Limit of Detection (LOD) of an analytical method may be defined as the concentration,which gives rise to an instrument signal that is significantly different from the blank.For spectroscopic techniques or other methods that rely upon a calibration curve for quantitative measurements,the IUPAC approach employs the standard deviation of the intercept (Sa), which may be related to LOD and the slope of the calibration curve, b,by
LOD = 3 Sa/b
Limit of Quantitation (LOQ)
The LOQ is the concentration that can be quantitated reliably with a specified level of accuracy and precision. The LOQ represent the concentration of analyte that would yield a signal-to-noise ratio of 10.
LOQ = 10 Sa/b
Where, Sa is the standard deviation of the peak area ratio of analyte to IS (6 injections) of the drugs and b is slope of the corresponding calibration curve.
Linearity and Range
Linearity indicates the ability of analytical procedures to produce results that are directly proportional to the concentration of analyte in the given sample. A series of solutions of drug substance standard were prepared in the concentration range from (0.6µg/ml) to (3.4µg/ml).These solutions were injected into the HPLC and linearity was determined by observing peak areas. A graph of peak area versus concentration (on X-axis concentration and on Y-axis Peak area) was plotted and the correlation coefficient was calculated.
Results and Discussion
The blank chromatogram and optimized chromatogram for amoxicillin is shown in Figure 2 and Figure 3 respectively.
Figure 2: Blank chromatogram for Amoxicillin.
Figure 3: Standard chromatogram for Amoxicillin.
Accuracy: Recovery study
Acceptance criteria: The percentage recovery should be within 98.0% to 102.0%. % RSD should not be more than 1.0%. The recovery of the method, determined by adding a previously analyzed test solution with additional drug standard solution at three levels of concentration, was 98.87- 99.76 %. The values of recovery (%) and RSD (%) listed in Table 2 indicate the method is accurate.
Table 2: Data of recovery for Amoxicillin.
| Amount added (mg) | Amount | % | ||||
| Concentration | Found (mg) | Recovery | Mean | SD | %RSD | |
| 80%- Sample 1 | 24.81 | 24.79 | 99.92 | |||
| 80%-Sample 2 | 24.89 | 24.75 | 99.44 | |||
| 80%-Sample 3 | 24.51 | 24.33 | 99.27 | 99.41 | 0.33 | 0.33% |
| 100%-Sample 1 | 30.22 | 30.21 | 99.97 | |||
| 100%-Sample 2 | 30.02 | 29.91 | 99.63 | |||
| 100%- Sample 3 | 30.05 | 29.9 | 99.69 | 99.76 | 0.18 | 0. 18% |
| 120% Sample 1 | 36.01 | 35.68 | 99.08 | |||
| 120% - Sample | 35.3 | 34.78 | 98.53 | |||
| 2 | 98.87 | 0.3 | 0.30% | |||
| 120% - Sample | 36 | 35.67 | 99.08 | |||
| 3 |
Linearity & Range
The calibration curve showed good linearity in the range of 0.6-3.4 µg/ml,for Amoxicillin (API) with correlation coefficient (r2) of 1.The slope and intercept of the calibration graph was calculated by using linear regression analysis. The regression equation of the calibration curve was: y=76594x-24947; r2=1. A correlation coefficient suggests that the developed HPLC method had an excellent linearity over the investigated range.The results for linearity are shown in Figure 4 and Table 3.
Figure 4: Calibration curve for Amoxicillin.
Table 3: Data for linearity.
| Conc.( µg/ml) | AUC |
| 0.6 | 4542042 |
| 1 | 6056056 |
| 1.4 | 7570070 |
| 1.8 | 9084084 |
| 2.2 | 10598098 |
| 2.6 | 12112112 |
| 3 | 13626126 |
| 3.4 | 15140140 |
Precision: Intra-assay & inter-assay
System precision
Aceptance criteria: RSD for area should not be more than 1%.
The intra & inter day variation of the method was carried out and the high values of mean assay and low values of standard deviation and % RSD (% RSD < 2%) within a day and day to day variations for Meloxicam revealed that the proposed method is precise (Table 4).
Table 4: Data of system precision for Amoxicillin.
| Injection ID | Area |
| 1 | 4542042 |
| 2 | 4533188 |
| 3 | 4535021 |
| 4 | 4530680 |
| 5 | 4536185 |
| 6 | 4532243 |
| Mean | 4534893 |
| SD | 4012 |
| % RSD | 0.09 |
Method Precision
Acceptance criteria: RSD values should not be more than 1% and the results are well within the limits (Table 5).
Table 5: Data of method precision for Amoxicillin.
| Injection ID | Area |
| 1 | 4542042 |
| 2 | 4533188 |
| 3 | 4535021 |
| 4 | 4530680 |
| 5 | 4536185 |
| 6 | 4532243 |
| Mean | 4534893 |
| SD | 4012 |
| RSD | 0.09 |
Robustness
Influence of small changes in chromatographic conditions such as change in flow rate (± 0.1ml/min), Wavelength of detection (±2nm) & acetonitrile content in mobile phase (±2%) studied to determine the robustness of the method are also in favor of (Table 5, % RSD < 2%) the developed RP-HPLC method for the analysis of Amoxicillin API.
Acceptance criteria: RSD value should not be more than 1% and the results obtained are well within limits (Table 6).
Table 6: Data of Intermediate precision for Amoxicillin.
| Sample | Assay %(w/w) | |
| Set- I | Set-II | |
| 1 | 98.9 | 98.83 |
| 2 | 98.86 | 98.83 |
| 3 | 98.96 | 98.77 |
| 4 | 98.98 | 98.85 |
| 5 | 98.87 | 98.8 |
| 6 | 99.03 | 98.86 |
| Mean | 98.93 | 98.82 |
| SD | 0.1 | 0.03 |
| %RSD | 0.1 | 0.03 |
| CI | 0.1 | 0.1 |
| Over all Mean | 98.88 | |
| Over all SD | 0.1 | |
| Overall RSD (%) | 0.1 | |
Stability
From the below data it was concluded that:The test sample was stable for atleast 9 hours at room temperature (about 25˚c).The test sample was stable for at least 15 hours of the temperature and the results are shown in Table 7.
Table 7: Data of stability for Amoxicillin.
| Time in hours | Room temperature25 ˚c | Room temperature 6˚ c | ||
| Initial | 4559861 | 4559861 | ||
| After 1 hr | 4540232 | 0.3 | 4552531 | 0.1 |
| After 2 hr | 4542807 | 0.2 | 4522082 | 0.4 |
| After 3 hr | 4555984 | 0.2 | 4527089 | 0.4 |
| After 4 hr | 4579426 | 0.2 | 4541420 | 0.4 |
| After 5 hr | 4598693 | 0.5 | 4554183 | 0.3 |
| After 6 hr | 4515495 | 0.6 | 4536440 | 0.3 |
| After 7 hr | 4503377 | 0.7 | 4471191 | 0.6 |
| After 8 hr | 4464949 | 0.9 | 4582647 | 0.7 |
| After 9 hr | 4460204 | 1 | 4564295 | 0.7 |
| After 10 hr | 4456992 | 1.1 | 4549355 | 0.6 |
| After 11 hr | 4458707 | 1.1 | 4545623 | 0.6 |
| After 12 hr | 4445107 | 1.2 | 4544017 | 0.6 |
| After 13 hr | 4538216 | 0.6 | ||
| After 14 hr | 4577662 | 0.6 | ||
| After 15 hr | 4571867 | 0.6 | ||
Estimation of Amoxicllin in Tablet Dosage Form
Assay was performed by using the regression equation (y = 76594x-24947;r2 =1) obtained from the standard curve of Amoxicllin API. Results obtained are given in table 8 and Figure 5.
Figure 5: Chromatogram for Amoxicillin marketed tablet.
Recovery Data for estimation Amoxicillin in GERMATIN tablets:
Conclusion
A New RP-HPLC method indicating assay of AMX in bulk and in pharmaceutical dosage forms is established.This method is simple,reliable,linear,accurate,sensitive and reproducible as well as cost effective for the effective quantitative analysis of AMX in bulk and tablet formulations.The method was completely validated showing satisfactory data for all the method validation parameters tested and method is free from interference of the other active ingredients and additives used in the formulations.Therefore the method is suitable for use of the routine quality control analysis of AMX in API or in pharmaceutical dosage forms.
Acknowledgement
The authors are thankful to MNR College of pharmacy for giving valuable facilities during the whole research work.