Determination of phophates in four food samples by molecular absorption spectrophotometry

Fosfati so minerali, ki v človeškem telesu opravljajo številne pomembne naloge. Skrbijo za zaščito in delovanje celične membrane, ohranjajo zdrave zobe in kosti ter skrbijo za sproščanje energije pri presnovi. Fosfati so soli fosforne (V) kisline, ki jih dodajajo kot aditive v predelana živila. Z aditivi ohranjajo barvo in videz živil ter jim podaljšajo rok trajanja. Najdemo jih lahko v kavnih pripravkih, zelenjavi (koruzi, zeleni papriki, žitih), sadju (marelicah, zelenih orehih…), živilih, ki so bogata z beljakovinami (mleku in mlečnih izdelkih), osvežilnih pijačah, mesnih in pekovskih izdelkih. Za določanje fosfatov je poznanih veliko različnih metod npr. gravimetrična, titrimetrična, spektrofotometrična, nefelometrična metoda in instrumentalne metode (npr. atomska emisijska spektrometrija, tekočinska kromatografija…). V diplomskem delu je bilo določanje vsebnosti fosfatov v različnih vzorcih izvedeno s spektrofotometrično metodo. Metoda temelji na reakciji anorganskega fosfata z amonijevim molibdatom [Mo(VI)], pri čemer nastane amonijev fosfomolibdat. Tega reduciramo s šibkim reducentom do molibden modrega in v modro obarvani raztopini merimo absorbanco s pomočjo UV/VIS spektrofotometra pri valovni dolžini 690 nm. Poleg določanja vsebnosti fosfatov v vzorcih mleka, jabolčnih sokovih, pecilnih praških in moki je namen diplomskega dela tudi primerjati dobljene rezultate ter preveriti ponovljivost izbrane metode.Phosphates are minerals that play important role in the human body. Their function is to protect the cell membrane and stimulate its function, and maintain healthy teeth and bones. They are also responsible for energy release in metabolism. Phosphates are phosphoric (V) acid salts used as additives in processed foods. Additives preserve the colour and appearance of foods and extend their shelf life. They can be found in coffee preparations, vegetables (maize, green peppers, cereals), fruit (apricots, green walnuts), protein rich foods (milk and dairy products), refreshing drinks, meat and bakery products. There are many different methods for determining phosphates, such as gravimetric, titrimetric, spectrophotometric, nephelometric method and instrumental methods (e.g. atomic emission spectrometry, liquid chromatography etc.). For the purposes of this diploma work, the spectrophotometric method was used for the determination of the phosphate content in various samples. The spectrophotometric method is based on the reaction of inorganic phosphate with ammonium molybdate [Mo (VI)], whereby ammonium phosphomolybdate is formed. The latter is reduced with a weak reducing agent to a molybdenum blue. The blue-coloured solution is then used to measure the absorbance using a UV VIS spectrophotometer at a wavelength of 690 nm. In addition to determining the phosphate content in samples of milk, apple juice, baking powder and flour, the objective of the diploma work is to compare the obtained results and to verify the repeatability of the chosen method