The application of DP polarography for the determination of zinc and content of zinc pyrithione in anti-dandruff shampoos

Abstract

Commercially formulated anti-dandruff shampoos contain zinc pyrithione (ZPT) as an active ingredient that has antifungal, antibacterial and anti-seborrheic properties. The determination of ZPT concentration in commercial anti-dandruff shampoos by differential pulse polarography (DPP) was based on the electrochemical reduction of zinc ions in ammoniacal buffer pH 10.2, and the linear dependence of the reduction differential pulse peak current at the potential - 1.33 V vs. concentration of zinc. Using the calibration curve method, it was found that the range of linearity for the determination of zinc concentration was from 1.28 x 10-5 to 1.39 x 10-4 mol L‒1 (linear regression equation: I = - 0.097 + 6.635 x 105c). Surface active ingredients and micro-components in the shampoos did not exert a polarographic interference for the determination of zinc and did not affect the indirect determination of the content of the active ingredient ZPT. The concentrations of zinc in the analyzed anti-dandruff shampoo samples were determined by the standard addition method, resulting in 4.20 x 10‒2 mol L‒1, 1.76 x 10‒1 mol L‒1 and 1.82 x 10‒1 mol L‒1. The results of DPP determinations of zinc and ZPT show that the content of ZPT was 0.28%, 1.15% i.e. 1.19% and was below the maximum recommended level of ZPT in anti-dandruff shampoos. This simple and sensitive differential pulse polarography method is suitable for a routine and rapid control of the active ingredient content, as well as for the quality control of anti-dandruff shampoos.

Aktivni sastojak komercijalno formulisanih šampona protiv peruti je cink-pirition, koji ima antifungalno, antibakterijsko i antiseboreično dejstvo. Određivanje cink-piritiona u šamponima protiv peruti primenom metode diferencijalne pulsne polarografije zasnivalo se na elektrohemijskoj redukciji jona cinka u amonijačnom puferu pH 10,2 i linearnoj zavisnosti intenziteta struje pika na redukcionom potencijalu - 1,33 V i koncentracije cinka. Metodom kalibracione krive je određen opseg linearnosti za određivanje koncentracije cinka od 1,28 x 10‒5 do 1,39 x 10‒4 mol L-1 i dobijena je linearna regresiona jednačina I = - 0,097 + 6,635 x 105c. Utvrđeno je da površinski aktivne komponente u matriksu šampona ne pokazuju polarografsku interferenciju i ne utiču na određivanje koncentracije cinka i sadržaja cink-piritiona u analiziranim šamponima. Koncentracije cinka u analiziranim uzorcima šampona određene su metodom standardnog dodatka i iznose 4,20 x 10‒2 mol L-1, 1,76 ' 10‒1 mol L-1 i 1,82 x 10‒1 mol L-1. Rezultati polarografskog određivanja cinka i sadržaja cink-piritiona pokazuju da su dobijene vrednosti cink-piritiona 0,28%, 1,15% i 1,19% ispod maksimalno preporučenog sadržaja cink-piritiona u šamponima protiv peruti. Ova jednostavna i osetljiva metoda diferencijalno pulsne polarografije pogodna je za rutinsko i brzo određivanje sadržaja aktivnog sastojka i kontrolu kvaliteta šampona protiv peruti.