Determination of Zinc Content in Commercial Toothpaste Samples in Nigeria by Atomic Absorption Spectrophotometric Method
Abstract
Zinc as its citrate or sulphate salt is added to some toothpaste as a bactericide to reduce the
presence of bacteria in the mouth. These bacteria can form plaque or produce acids which cause
dental decay and halitosis. Zinc salt is added at amounts which are enough to show activity against
oral bacteria without causing toxicity to the user. Five commercial samples of different brands of
toothpaste (TP-A, TP-B, TP-C, TP-D and TP-E) were purchased from different pharmacy stores in
Ogige and Eko markets, Nigeria and analysed for the presence of zinc using atomic absorption
spectrophotometric method. The samples were digested with deionized water and HNO3,
centrifuged and filtered. The absorbance of the supernatants obtained was read with a
spectrophotometer. Calibration curves for zinc sulphate and zinc citrate were obtained with
regression (R2) values of 0.9992 and 0.9973, respectively. The equation obtained from the curves
used in determining the content of zinc in the samples. The zinc content (% w/w) of samples was
determined to be 0.8467%, 0.8127%, 0.0119%, 0.0188% and 0.0305%, respectively. These values
were well below the maximum permissible level of zinc in toothpaste samples but were within the
upper limit for daily zinc intake.
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