Quantitative Determination of Paracetamol in Tablets - Assignment Example

Name : xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Tutor :xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Title : Quantitative determination of paracetamol in tablets by u.v/visible spectroscopy-a modification of the british pharmacopiae. Institution : xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Date :xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx @ 2011 Quantitative determination of paracetamol in tablets by u.v/visible spectroscopy-a modification of the british pharmacopiae Introduction This is a laboratory report on the quantitative determination of paracetamol by spectrographic means specifically ultra-violet/visible spectroscopy. Paracetamol is a pain reliever(analgesic) and an antipyretic,that is a fever reliever.Its IUPAC name is N-(4-hydroxyphenyl)acetamide and its structure is as shown below; The British Pharmacopoeia gives an outline of the procedure to be followed in order to carry out this analysis according to laid down guidelines (Lonardi,.Pharm. Acta 2006).In order to assess this procedure it is in order to briefly outline its methodology so that i shall conviniently be able to refer to it later in my report.For convenience please note that i shall refer to the British Pharmacopoeia as simply B.P heretafter. Background of the B.P It was proved by Brodie and Axelrod in 1948 that paracetamol was metabolised from phenacetin and acetanilide in the body. The two substances were initially used as the predominant analgesics of the day. But with this rediscovery paracetamol was somewhat rediscovered as the analgesic and antipyretic of choice. In 1956 ,500 mg paracetamol tablets were introduced into the market initially as a prescription drug and in 1963 was introduced into the B.P.Subsequently,paracetamol later became a popular over the counter drug.[CITE] The B.P comprises of collections that are published annualy for use as quality standards for substances classified as medicines in the United Kingdom. the B.P is routinely used by pharmaceutical corporations and/or research bodies etc, in product research and development.These standards have a legal implication in regard to the quality of medicines.This Pharmacopoeia acts in conjunction with Medicines and Healthcare products Regulatory Agency (MHRA) of the United Kingdom and it does this in the area of licensing and inspection processes where it acts as a legal control. The B.P is prepared partly by the BP Laboratory whose major function is to develop and validate test analytical test methods.In this role it therefore provides both technical and analytical support to the B.P.It is important to note that it receives relevant input from among others,academics,professional bodies,hospitals etc from all over the world.[CITE] Alterations to the B.P The B.P is obviously a very useful tool in the analysis of many compounds such as paracetamol at all levels,be statutory or at individual levels as seen above.However due to our specific problems with our sample,some alterations of some aspects of the procedure need to be made in order to arrive at realistic results.These are; Stock solution preparation The amount selected to make the stock standard solution may be a bit too large and thatis the 200 mg of paracetamol. This is when compared to other experiments involving the same kind of analysis.According to research conducted by xxxxxxxxxxxxx the ideal concentration of the test sample should be 1mg/100ml.This can be arrived at by dissolving 100 ml of paracetamol standard in the solvent which is 0.1N NaOH.From this a 1mg/100ml solution can be conviniently made for making the working standard solution by taking 1 ml of the stock and further diluting it to 100ml. Another potential problem is that dissolution of such a large amount within the 100ml may be tricky.i will therefore in my approach use 100ml of paracetamol standard to make the working standard and for the wavelength determination. Wavelength The wavelength given the B.P procedure is given as 300 nm.This may present a problem.According to xxxxxxxxxxxxxxxwhen a solution containing 1mg/100ml of solvent is run on the u.v machine,the typical peak absorption wavelength(λmax) lies from 255-257 nm. This can be seen when looking at the relation; E = hf where h= plancks constant, F= frequency and E = energy. But c =λf , so f = c/λ Meaning we now have E = hc/λ ,the higher the wavelength, the lower the frequency and hence the lower the energy of the incident light.This means that the bonding electrons in paracetamol will not have enough energy to take a big jump which in turn means that less absorption will result.Therefore i decided to use a smaller wavelength for maximum absorption. A. MATERIALS AND METHOD REAGENTS NaOH Paracetamol(pure) Distilled water APPARATUS XXXXXXXXX SPECTROMETER Instrument set up Wavelength = 257nm Slit width=1.0 nm Mode = Absorbance OUTLINE OF THE BRITISH PHAMACOPIAE PROCEDURE Stock standard solution preparation Exactly 200 mg of paracetamol standard is weighed and transferred into a 100ml flask followed by tand he addition about 50 ml 0f 0.1N NaOH.The two are mixed until all paracetamol is dissolved completely. (M. Blanco, J. Coello 999).The resulting solution is then topped up to the mark with 0.1 N NaOH. Preparation of working standard solutions From the stock standard solution prepared above 0.2ml, 0.4ml, 0.6ml,0.8ml and 1.0ml are pipetted into five 100ml volumetric flasks respectively. Each is topped up to the mark using 0.1N NaOH.The resulting solutions are then 2µg/ml,4 µg/ml ,6 µg/ml ,8 µg/ml and 10 µg/ml in concentration respectively. Preparation of sample solutions A 500mg paracetamol tablet is crushed and 25mg of the crushed powder weighed into a 100 ml volumetric flask.50 ml 0.1N NaOH is added and mixed with the powder until dissolution takes place.5 ml of the solution are separately dispensed into two volumetric flasks labelled final sample .One contains 5 mls of the filtered solution and the other 5 mls of unfiltered solution (M. Blanco, J. Coello 999). ORIGINAL CONDITIONS OF THE B.P METHOD Instrument set up Wavelength – 300nm Slit width – 1nm Reading – Absorbance STANDARDS AND SAMPLING PREPARATION-USING THE ALTERNATIVE PROCEDURE 1. Preparation of Stock Standard Solution a) 100 mg of the paracetamol standard was accurately weighed and transferred into a 100 ml volumetric flask. b) About 80 ml of 0.1M NaOH was added to the flask and mixed with the paracetamol until complete dissolution. c) The solution was made up to 100 ml using 0.1M NaOH. d) 1 ml from this solution was pipetted into a 100ml volumetric flask and topped to the mark using 0.1M NaOH.This was 10 µg/ml. 2. Preparation of Working Standard Solutions a. Five 100 mlvolumetric flasks were labelled and into each one of them was pipetted 0.4 ml, , 0.6mL, 0.8mL, 1.0mL & 1.2mL respectively of stock standard solution. b) Each of these was made up to the mark using 0.1M NaOH. c) The resulting solutions were 4µg/mL, 6µg/mL, 8µg/mL, 10µg/mL and 12µg/mL paracetamol working standard solutions. 3. Preparation of sample solutions a) Six tablets of paracetamol from a packet were taken and weighed. b) The average weight of one tablet was obtained by dividing the total weight by 6. c) These were then crushed thoroughly and mixed up together using a simple cone and quarter method. d) From this mixture, 100mg was weighed out to a 100 ml volumetric flask and about 80 ml of 0.1M NaOH added.This was shaken until all the active ingredient was dissolved and topped up to the mark. e) From this solution,5 mls were pipetted into a separate 100ml volumetric flask and topped to the mark. f) The remaining solution in the other flask was filtered.5 mls of the filtrate was pipetted into another flask. g) Both flasks were labelled,one filtered and the other unfiltered respextively. 4) FINDING WAVELENGTH OF MAXIMUM ABSORPTION(λmax) a) The spectrum the paracetamol was plotted on the instrument using the diluted standard(10µg/ml) as prepared in no.1(d) above. b) The wavelength of maximum absorption was found to be 257 nm. 5) INSTRUMENT SET UP FOR ANALYSIS Photometric determination was set with the following parameters: Wavelength – 257nm Slit width – 1nm Reading – Absorbance 6) PROCEDURE a) A blank of 0.1N NaOH was run and then autozero selected. b) The sample UV cell was rinsed with the 10µg/mL standard solution and then filled with the same solution. c) The absorbance was recorded when the cell was inserted into the instrument. d) The absorbances of the remaining working standards was similarly obtained and recorded. e) The cell was again rinsed with 0.1N NaOH solution followed by the sample solution.The absorbance was recorded. 4. CALCULATIONS AND RESULTS a) Calculation of concentration of stock standard solution Wgt of paracetamol standard taken = 100 mg Topping volume = 100 ml When dissolved in 100ml of 0.1N NaOH we get: 100mg / 100 ml When 1 ml is taken and fed to 100ml the dilution factor = 100ml/1ml = 100 Therefore we shall have 100/100 =1 mg/100 ml So it follows 0.01mg/1ml Therefore 0.01 x 1000µg/ml or 10µg/ml This is the standard used to obtain the absorption maximum wavelength for paracetamol from its spectrum. b) Calculation of concentration of working standards This is accomplished in a similar manner to the 10µg/ml working standard Aliquot taken(ml) (A) Final topping volume(ml) (B) Stock concentration Resultant Conc.(mg/100ml) A/B Resultant Conc.( µg/100ml) A/B * 1000 0.4 100 1000µg/ml 0.004 4 0.6 100 1000µg/ml 0.006 6 0.8 100 1000µg/ml 0.008 8 1.0 100 1000µg/ml 0.01 10 1.2 100 1000µg/ml 0.012 12 c) WEIGHTS OF TABLETS Total weight of 6 tablets = 3005mg Average weight of 1 tablet = 500.83 d) ABSORBANCE OF WORKING STANDARDS STANDARD CONCENTRATION ABSORBANCE 0.0[blank] 0.00 4 µg/ml 0.28 6 0.40 8 0.60 10 0.73 12 0.88 e) ABSORBANCE OF SAMPLE SAMPLE CONCENTRATION ABSORBANCE Reference: International Conference on Harmonisation, ICH Harmonised Tripartite Guideline—Text on Validation of Analytical Procedures, Fed. Regist., 1995, 60, 11260. International Conference on Harmonisation, ICH Harmonised Tripartite Guideline—Validation of Analytical Procedures: Methodology, Fed. Regist., 1997, 62, 27463. United States Pharmacopeial Convention, United States Pharmacopeia 23, US, Rockville, 1995, p. 1982. Pharmacopeial Forum, 1998, 24, 6582. M. Blanco, J. Coello, A. Eustaquio, H. Iturriaga and S. Maspoch, J. Pharm. Sci., 1999, 88, 551. A4 P. Corti, E. Dreassi, G. Corbini, S. Lonardi, R. Viviani, L. Mosconi and M. Bernuzzi, Pharm. Acta Helv., 1990, 65, 28. A5 P. Corti, L, Savini, E. Dreassi, G. Ceramelli, L. Montecchi and S. Lonardi,. Pharm. Acta. Helv., 1992, 67, 57. A6 A. F. Zappala and A. Post, J. Pharm. Sci., 1977, 66, 292.A7 P. Dubois, J. R. Martinez and P. Levillain, Analyst, 1987, 112, Read More