Osjetljivo i selektivno spektrofotometrijsko određivanje doksiciklin hiklata u farmaceutskim pripravcima koristeći Folin-Ciocalteuov reagens

A spectrophotometric method for the determination of doxycycline (DOX) is described. The method is based on the formation of blue colored chromogen due to reduction of tungstate and/or molybdate in Folin-Ciocalteu (F-C) reagent by DOX in alkaline medium. The colored species has an absorption maximum at 770 nm and the system obeys Beer’s law over the concentration range 0.7512.0 μg mL1 DOX. The apparent molar absorptivity is 2.78 × 104 L mol1 cm1. The limit of quantification and detection values are reported to be 0.20 and 0.08 µg mL1, respectively. Over the linear range applicable, the accuracy and precision of the method were evaluated on intra-day and inter-day basis. The reported mean accuracy value was 101.0 ± 1.7 %, the relative error was ≤ 2.7 % and the relative standard deviation was ≤ 2.5 %. Application of the proposed method to bulk powder and commercial pharmaceutical tablets is also presented. No significant difference was obtained between the results of the proposed method and the official BP method. The procedure described in this paper is simple, rapid, accurate and precise.U radu je opisana spektrofotometrijska metoda određivanja doksiciklina (DOX). DOX u bazičnom mediju reducira volframat i/ili molibdat u Folin-Ciocalteuovom (F-C) reagensu pri čemu nastaje modro obojeni kromogen. Obojeni produkt ima apsorpcijski maksimum pri 770 nm. Sustav podliježe Beerovom zakonu u koncentracijskom području 0,7512,0 μg mL1 DOX. Molarni apsorpcijski koeficijent iznosi 2,78 × 104 L mol1 cm1. Granice kvantifikacije i detekcije su 0,20, odnosno 0,08 µg mL1. Unutar linearnog područja procijenjene su ispravnost i preciznost unutar jedne i više eksperimentalnih serija. Ispravnost je iznosila 101,0 ± 1,7 %, relativna pogreška ≤ 2,7 %, a relativna standardna devijacija ≤ 2,5 %. Ispitana je i primjenjivost predložene metode na praškasti uzorak doksiciklina i komercijalne tablete. Usporedbom rezultata dobivenih predloženom metodom i oficijelnom BP metodom nisu ustanovljene značajne razlike. Opisana metoda je jednostavna, brza, ispravna i precizna