Aspirin standard solution

Weight of contents of 20 capsules = 10.556 g Weight of capsule content analysed = 0.1025 g Capsule eontents were dissolved in methanol and adjusted to 100 ml Concentration of aspirin standard solution = 50.4 mg/100 ml Absorbance of sample at 299 nm in 0.1 M NaOH without standard addition = 0.488... 

Concentration of aspirin standard in standard addition solution = 0.504 mg/100 ml. 

The assay is more or less the same as that described for the paracetamol tablets except that the tablets are extracted with 0.05 M sodium acetate buffer pH 4.4. The calibration standard solutions are prepared so that they contain both aspirin and paracetamol in 0.05 M sodium acetate buffer pH 4.4 in the concentration range 1.0-1.5 mg/100 ml. 

Make two separate 10-/aL injections, each for the 4.5 and 5.5 grain 100-mL standard solutions of aspirin. These were the solutions prepared in Activity B-3. The spectrophotometric detector should be set to 0.2 AUFS (254 nm). 

Tang etah (54) have also reported HPLC determination of serum salicylic acid and aspirin concentrations. Serum (0.1 ml) was treated 1 fj of carbamazepine (internal standard) solution (0.65 mg/ml), 0.1 ml of 0.1 M-phosphate buffer of pH 7.4, 10 //I of 21.25% H3P04 and 1.2 ml of ethyl ether prior to centrifugation at 4000 rpm... 

Standard solutions. Prepare individual standard solutions of about 100 mg/L, 20 mg/L, and 10 mg/L each for aspirin, phenacetin, and caffeine in methylene chloride as follows. Weigh about 25 mg (to the nearest 0.1 mg) of each, transfer to 100-mL volumetric flasks, dissolve, and dilute to volume with methylene chloride. Dilute 2 and 1 mL of this solution to 25 mL in 25-mL volumetric flasks to prepare the 20 and 10 mg/L solutions, respectively. 

Record absorbance versus wavelength curves for the standard solutions and unknown solutions between 200 to 300 nm. (This step may be deleted if you do not have a recording ultraviolet spectrophotometer.) Does the wavelength of 277 nm appear to be the most suitable wavelength for the determmation of aspirin Do the wavelengths of 250 and 275 nm appear to be the best wavelengths for the measurement of the absorbance for the mixture of phenacetin and caffeine Explain. 

Using a 5- or 10-/iL syringe, inject a 5-pL, aliquot of each 100 mg/dL standard solution to obtain chromatograms for aspirin, phenacetin, and caffeine. Similarly, obtain chromatograms for the serial aspirin standards (one chromatogram for each, unless you have time for more). 

Prepare appropriate stock and working standard solutions of aspirin and caffeine in methanol to bracket the amounts of ingredients contained in the sample solution. For analysis, for example, the aspirin stock solution should contain approximately 80 mg/ml and caffeine approximately 5.5 mg/ml. Working standards are mixtures of about 1.0 ml of each solution, 1.5 ml of each solution, and 2.0 ml of each solution made up to volume with methanol in 25-ml volumetric flasks. 

A 1-50 g mass of aspirin was hydrolysed with 25-0 cm of 1-00 mol NaOH solution. After the hydrolysis was complete, the reaction mixture was transferred, with rinsings, to a 250 cm standard flask and made up to the graduation mark with distilled water. The solution was mixed thoroughly and 25-0 cm was pipetted Into a conical flask, along with a few drops of phenolphthalein Indicator. This was titrated with 0-0500 mol sulfuric add solution until the end-point of the titration was Indicated by the colour change from pink to colourless. The titrations were repeated until concordant results were obtained. 

Analysis was carried out by difference spectrophotometry. A one-point standard calibration for the determination of aspirin in dextropropoxyphene compound capsules was prepared by adding a known amount of aspirin to the sample from a standard stock solution. Stated content in the capsules ... 

The difference between the absorbance with standard addition and that without represents the absorbance due to a 0.504 mg/100 ml solution of aspirin. 

Salicylic acid, Na salicylate and aspirin can be determined by titration 118) with standard KBr03 solution. The incision on the oscillopolarogram is used for end point detection. 

Method describes the quantitative determination of salicylic acid in aspirin tablets by infra-red spectrophotometry. 200 mg samples of aspirin was dissolved in CHCI3 and centrifuged. The supernatant solution was then analysed for salicylic acid by I.R. spectrophotometry at 1160 cm 1 with the use of a standard-additions method (45). 

A typical example of a limit test is the test for salicylic acid in a sample of Aspirin BP. Salicylic acid is formed by hydrolysis of aspirin (or may be an impurity from the synthesis). The test involves comparing the violet colour produced when the sample is reacted with ferric chloride with that obtained from a standard salicylic acid solution. 

The analytical approach to follow is a modification of the United States Pharmacopoeia method. The technique involves titrating a solution of aspirin with standard lead perchlorate solution in the presence of a Pb-ISE and reference electrode couple. Because of the PbS04 formed has a shght but significant solubility in water, the titration is carried out a solution of 37 mL acetone and 3 mL water. This solution lowers the solubility of PbS04 critically. The following solutions are required ... 

A series of sequential baseline absorbance measurements are made in a spectro-photometric method, for determining the purity of aspirins in tablets using a blank solution. The absorbance readings are 0.002, 0.000, 0.008, 0.006, and 0.003. A standard 1 ppm aspirin solution gives an absorbance reading of 0.051. What is the detection limit ... 

Using the absorbances of the standard and the unknown aspirin solution at 277 run, calculate the percent aspirin in the ARC tablets and the number of mil-ligrains of aspmn per tablet keeping in mind the dilutions. 

By referring to Experiment 25 (Acid-Base Titration and Molecular Weight of an Unknown Acid), devise a reasonable method for determining the percent of aspirin in commercial aspirin tablets. The pKa for aspirin is 3.48, which lies between the two pK s of oxalic acid used in Experiment 25. Your instructor must approve an outline of your method and the quantities you plan to use before you begin work. An approximately 0.1 M standardized NaOH solution will be provided. Record all experimental data in TABLE 31.IE. 

Quantitative analysis of tablets containing aspirin, phenacetin and caffeine is to be carried out. Each of these components show distinct carbonyl bands in chloroform solution and calibration data for known concentrations are listed below in Table 3.4. Each of the standards was studied by using a 0.1 mm pathlength... 

Apply 10 pi of each of the three standard aspirin and caffeine mixtures and 10 pi of sample solution in duplicate by streaking onto preadsorbent areas of adjacent channels using Drummond microcaps. 

A new salicylate eledrode based on polymer membranes was used in a flow injection analysis system [66]. The electrode membrane contains 29.2-31.0% of PVC, 5.8-6.3% of tetraoctylammonium salicylate, 58.5-62.7% of o-nitrophenyloctylether and 6.5% of p-ferf-octylphenol. The tubular electrode was stored for approx. 6 months in a sodium salicylate solution. The electrode shows the slope of response curve close to theoretical — 56.0 0.6 mV decade in the range of 5 x 10" -10" mol L the response time is up to 5 s. The electrode can be used in a pH range of 6-9. The log K selectivity coefficients are 2-2.9 for acetates, 1.8-2.2 for chlorates, 0.7-1.0 for nitrates and 0.6-1.3 for acetosalicylates. The tubular salicylate electrode can be used for determination of acetylsalicylic add, after its previous analysis to salicylate, in multicomponent preparations and effervescent tablets (Anadin Extra, Aspirin, Dolviran, Alka-Seltzer). The results of potentiometric measurements are consistent with the method used in pharmacopoeia 100.7 to 103% of the compound was obtained, with standard deviation of RSD 0.6-1.8%. 

Dissolve 1 g of salicylic acid in 60 ml of ethanol, adjust the volume to 100 ml with water dilute 10 ml of this solution to 1 litre as a standard, making 1 ml = 0-1 mg of acid. Dissolve 0-6 g of aspirin in a measuring cylinder in 9 ml of ethanol and dilute with water to 90 ml. Take two similar Nessler cylinders into one pour 60 ml of the solution, into the other the remaining 30 ml with 3 ml of ethanol and adjust to the volume of the first. There is thus a difference of 200 mg in the amount of aspirin in the two solutions. Add 1 ml of 1 per cent acid ferric ammonium sulphate solution to each, mix and match the colour by adding the standard salicylic acid solution from a burette. Each ml of standard is equivalent to 0-05 per cent of salicylic acid in the sample. 

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