Your assignment is to prepare and submit a paper on colourimetry paracetamol. Colourimetry is an extremely useful technique in establishing the concentration of substances. This is achieved by preparing a known concentration series of about 4 solutions, after which their absorbance is determined after the addition of colour by a reagent. The absorbance values give a calibration curve from which the concentration of an unknown substance is established. This technique is useful in the determination of metal ions alloys and biological fluids. Numerous industrial and clinical experiments report the successful usage of colorimetric procedures in the establishment of the concentrations of chemical substances. For example, the determination of vitamin E in food, trace amounts of platinum in glass, flavonoids in food, and detection of alpha fetoproteins among many other uses.
Paracetamol (4-acetamedophenol) is a commonly used painkiller that lessens the temperature of fever patients. Its pain reducing effects are known as analgesic effects whereas its fever reduction action is called the antipyretic effect. Numerous over the counter medications contain paracetamol especially those meant for the relief of colds and flu. The most common form is the 500 mg tablet though other formulations such as suspensions and suppositories also exist. Paracetamol is quickly taken in from the gastrointestinal tract and attains peak plasma concentrations in about an hour. The cytochrome P450 system metabolises it into N-acetyl-p-benzoquinamine (NAPQI), a toxin that is entirely detoxified through conjugation with glutathione and excreted. Paracetamol is a fairly safe drug. However, doses greater than 10 grams have been reported to cause toxicity (Bose et al. 2005). This experiment aimed at using colourimetry as a chemical technique to make a calibration curve of absorbance against concentration for known paracetamol concentrations and using it to obtain the concentration of paracetamol in the sample with the unknown concentration. Materials and Method 100 ml of 0.002M paracetamol solution was prepared by dissolving the right quantity of the drug in 10 ml of sodium chloride solution and topping up to 100 ml. This was the stock solution for the experiment. 1.0 ml of 6M HCl and 2 ml of 10% sodium nitrite were added to each of the seven labelled test tubes. Paracetamol and water were then added to the tubes in predetermined quantities after which the tubes were methodically mixed and allowed to rest for about 2 minutes. 2 ml of 15% sodium sulphamate were carefully added to the test tubes followed by 2.5 ml of 25% sodium hydroxide. The tubes were shaken for 15 seconds and allowed to stand for 2 minutes. This allowed all the bubbles to disperse. The absorbance of the contents of tubes 2 to 7 was then read at a wavelength of 430 nanometers using tube 1 as the blank. The values of absorbance were recorded for each concentration of paracetamol.
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