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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.

Perturbation of the BrayLiebhafsky non-oscillating subsystem (mixture of KIO3 and H2SO4), i.e., Dushman reaction (DR), by piroxicam (PX), was observed in an open reactor, i.e., in the continuously fed well-stirred tank reactor (CSTR). Monitoring the response of DR to perturbations by different concentrations of PX allows developing a simple procedure for quantitative determination of this analyte in both bulk drug and pharmaceutical preparation (injection). A tentative perturbation mechanism of PX action on the DR matrix, based on a kinetic scheme that was suggested by Agreda etal., is proposed. The PX reactivity in DR has been generally related to the reaction of PX with hypoiodous acid (HIO) present in the matrix.

A novel method for the determination of piroxicam (PX) is proposed and validated. For this purpose, the Bray-Liebhafsky (BL) non-oscillating subsystem (mixture KIO3 and H2SO4), i.e. Dushman reaction (DR) was used. The proposed method relies on the linear relationship between maximal potential shift, ΔEm, and the logarithm of the injected PX amounts in the concentration range 2.0 × 10−5 mol L−1 − 2.0 × 10−4 mol L−1 . The sensitivity of the proposed method is 1.5 × 10−5 mol L−1 . Some aspects of the possible mechanism of UA action on the DR matrix system are discussed.