APC tablet

Yarnelle, M. K. West, K. J. Modification of an Ultraviolet Spectrophotometric Determination of the Active Ingredients in APC Tablets, /. Chem. Educ. 1989, 66, 601-602. 

The analysis of APC tablets (a mixture of aspirin, phenacetin, and caffeine) has been a common undergraduate laboratory experiment. This experiment describes modifications to the standard analysis for APC tablets in which paracetamol (also known as acetaminophen) replaces phenacetin. 

High performance liquid chromatography is used for the separation and quantitative analysis of a wide variety of mixtures, especially those in which the components are insufficiently volatile and/or thermally stable to be separated by gas chromatography. This is illustrated by the following method which may be used for the quantitative determination of aspirin and caffeine in the common analgesic tablets, using phenacetin as internal standard where APC tablets are available the phenacetin can also be determined by this procedure. 

APC tablet (aspirin, phenacetin, caffeine, any supplier). If these tablets are not available, a laboratory mixture may be prepared by mixing 226.8 mg of acetylsalicylic acid (aspirin), 32.4 mg of caffeine, and 162 mg of phenacetin for this experiment. This laboratory mixture will suffice as an APC tablet. ... 

Crush an APC tablet with a glass stirring rod. Transfer the... 

B. Example results of the separation of the APC tablet (or mixture) under the conditions of the experiments are presented in Figures 12-2 to 12-7. These chromatograms are used for all subsequent sample calculations of performance parameters. 

FIGURE 12-2. Example of reverse-phase separation of an APC tablet. Mobile phase MeOH. Flow rate 1 mL/min. Detector UV at 254 nm, 1.0 AUFS. Sample APC tablet in 100 mL MeOH, 10-p.L injection. Column Bondapak Ci8/Porasil B, 2 mm ID x 61 cm. (Note Actual separation will depend upon the quality of the mobile phase and column packing.)... 

Place one APC tablet in each of five 100-mL volumetric flasks. Add 75 mL of methanol to each flask, dissolve the active ingredients by vigorous agitation for 3 mins. Dilute to mark with methanol and allow the insoluble binders (excipients) to settle. 

Figure 13-4 shows an example of the phenacetin standards and APC tablet analysis on a high-efficiency column. 

For those who analyzed the APC tablet, if available, refer to Experiments for Instrumental Methods, C. N. Reilley and D. T. Sawyer, McGraw Hill, New York, 1961, pp. 185-190, and compare the spectro-photometric method for determining phenacetin in an APC tablet to the chromatographic method which you just completed. 

B. Repeat the experiment D but carry out the quantitation for the aspirin and/or caffeine in the APC tablets. What sources of error are present ... 

In addition to aspirin and Cciffeine the most common components of analgesics are, at present, acetaminophen and ibuprofen (Notrin). Phenac-etin, the P of the APC tablet and a former component of Empirin, has been removed from the market because of deleterious side effects. In addition to one or more of these substances, each tablet contains a binder, often stcu-ch or silica gel. And to counteract the acidic properties of aspirin an inorganic... 

An over-the-counter analgesic called APC Tablets contains aspirin, paracetamol and codeine. An extract of these tablets was dissolved in toluene (methylbenzene) and filtered to remove insoluble solids. Devise a separation scheme to isolate all three drugs in a pure form. 

In 1963 Hoffman and Mitchell described a method for determining in a single run the active ingredients in APC-tablets (= Acetylsalicylic acid, Phenacetin, Caffeine tablets). Due to the high ratio of phenacetin to caffeine (162 mg 32 mg) and the small differences in their retention times, it was not very satisfactory for the determination of caffeine. However, the means of several analyses yielded results close to either the labeled claim or the composition by synthesis. The results of a series of analyses of synthetic APC mixtures are listed in Table 20.3. 

As examples the separation of aspirin, caffeine, and phenacetin (APC tablets) is accomplished by a mobile phase of methanol-acetic acid-ether-benzene (1 18 60 120) and nitroglycerine, a vasodilator, present in heart medication capsules can be separated from the other capsule materials by benzene. 

EXPERIMENT 26 ULTRAVIOLET SPECTROPHOTOMETRIC DETERMINATION OF ASPIRIN, PHENACETIN, AND CAFFEINE IN APC TABLETS USING SOLVENT EXTRACTION... 

APC tablets are a mixture of aspirin, phenacetin, and caffeine. Each of these substances has characteristic absorption in the ultraviolet region, with the principal maxima lying at 277 nm for aspirin, 275 nm for caffeine, and 250 nm for phenacetin. In the procedure, a powdered tablet is dissolved in methylene chloride, and the aspirin is separated from the phenacetin and caffeine by extracting it into aqueous sodium bicarbonate solution. The separated aspirin is back-extracted into methylene chloride by acidifying the aqueous layer and is then measured spectrophoto-metrically at 277 nm. The phenacetin and caffeine that remain in the original methylene chloride layer are determined in mixture as described in Chapter 16 (Equations 16.16 and 16.17). 

Note Component of APC tablets, also containing aspirin and caffeine. Phenacetin may reasonably be anticipated to be a carcinogen Fourth Annual Report on Carcinogens (NTP 85-002, 1985) p 165. 

When a compound is a major sample constituent, dissolving the sample in an appropriate amount of suitable solvent followed by direct spotting of a portion of the sample may be adequate for TLC. This approach was used to separate caffeine in APC tablets on C,g reversed-phase layers (Whatman) containing a fluorescent indicator [36]. 

Trade names APC Tablets, Emprazil, Fiorinal, Soma, Synalgos... 

Phenacetin turned out to be a highly effective analgesic and antipyretic. A common form of combinafion pain reliever called an APC tablet was once available. An APC tablet contained Aspirin, Phenacetin, and Caffeine (hence, APC). Phenacetin is no longer used in commercial pain-relief preparations as it was discovered that not all aromatic hydroxyl groups lead to toxic compounds. Today the compound acetaminophen is very widely used as an analgesic in place of phenacetin. 

Because of the central nervous system effects from caffeine, many people prefer decaffeinated coffee. The caffeine is removed from coffee by extrachng the whole beans with an organic solvent. Then the solvent is drained off, and the beans are steamed to remove any residual solvent. The beans are dried and roasted to bring out the flavor. Decaffeination reduces the caffeine content of coffee to the range of 0.03% to 1.2%. The extracted caffeine is used in various pharmaceutical products, such as APC tablets. 

When the compound of interest is a major constituent of the sample, simply dissolving the sample in an appropriate amount of a suitable solvent followed by direct spotting of a portion of the sample may be adequate for TLC. As an example of this approach, Sherma and Beim (1978) separated caffeine in APC tablets on Cjg reversed-phase layers containing a fluorescent indicator. The tablet was extracted in 25 ml of chloroform-methanol (1 1), and l-pl portions of the extract were spotted on the plate along with caffeine standards. After development with methanol-0.5A/ NaCl (1 1), aspirin, phenacetin, and caffeine were... 

Sherma, J., and Beim, M. (1978). Determination of caffeine in APC tablets by densitometry on chemically bonded Cig reversed phase layers. HRC CC J. High Resolut. Chromatogr. Chromatogr. Commun. 1 309-310. 

TLC is useful for the determination of aspirin, phenacetin, and caffeine in the analgesic tablet, APC. A sample from a methanolic solution of an APC tablet was applied to a Whatman KCig reversed-phase plate. Spots were developed for 15 cm in an unequilibrated tank (about 70 min), and detected by fluorescence quenching the Rp values were phenacetin, 0.26 caffeine, 0.47 and aspirin, 0.74 (Sherma and Beim, 1978). Detailed Experiment 2 in this chapter is concerned with TLC-densitometric analysis of aspirin and caffeine in analgesic tablets. Sherma and Rolfe (1992) described the analysis of analgesic tablets (Exce-... 

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