Application of 4-(2-pyridylazo)resorcinol in spectropotometric determination of iron in drinking water in the presence of manganese

Pravilnikom o zdravstvenoj ispravnosti vode za piće određene su maksimalne dopuštene koncentracije pokazatelja kakvoće vode. Zbog zadovoljavanja zakonske regulative i za uspješnu provedbu tehnoloških procesa obrade vode za piće nužna je kontrola kvalitete vode za piće, tj. njena kemijska analiza. Jedan od pokazatelja kakvoće vode za piće je koncentracija željeza i mangana u vodi. Za njihovo određivanje razvijene su brojne analitičke metode, od kojih se svojom jednostavnošću ističu spektrofotometrijske metode. U ovom se radu pokušalo razviti jednostavnu i pouzdanu spektrofotometrijsku metodu određivanja željeza u vodi, koja bi omogućavala istovremeno određivanje mangana. Kao kromogeni reagens odabran je 4-(2-piridilazo) rezorcinol i metoda je optimirana s obzirom na pH pri kome oba metala stvaraju stabilne kelate. Utvrđeno je da je metoda visoko selektivna na željezo, koje je pri 720 nm moguće odrediti s granicom detekcije od 6 μg/L. Metoda je linearna u širokom području koncentracija željeza, od 0 do 300 μg/L. U binarnim smjesama Mn je moguće odrediti mjerenjem apsorbancije na 510 nm, uz korekciju za apsorbanciju kompleksa Fe(II)-PAR na toj valnoj duljini, određenoj na temelju apsorbancije pri 720 nm. Relativna pogreška pri određivanju Fe i Mn u binarnim smjesama manja je od 5 %.Maximum levels of contaminants in drinking water are determined in The State Water Quality Regulations for healthy drinking water. To obtain legal regulations and successful technological treatments on drinking water, the control of quality and chemical analysis of water are required. One of indicators of drinking water quality are significant amounts of iron and manganese present in water. A number of analytical methods have been studied, from which the spectrophotometric method has been reported as simple method. In this work, a simple spectrophotometric method for simultaneous determination of iron and manganese in drinking water was studied. The proposed method is based on selected chromogenic reagent 4-(2-pyridylazo) resorcinol and on formation of an stable metal chelates at optimal pH. The recommended method has been successfully applied and highly selective to the determination of iron. The absorbance was measured at 720 nm with limit of detection at 6 μg / L. The method was linear for determination of iron in range 0-300 μg / L. In binary mixtures, recommended method allowed determination of manganese at 510 nm. Absorbance of manganese was corrected with absorbance of complex Fe(II)-PAR on the same wavelength, but determined on absorbance at 720 nm. Relative error for determination of iron and manganese in binary mixtures were lower than 5%