| Abstract | Cilj ovoga istraživanja je bio uvesti analitičku metodu koja bi omogućila precizno, pouzdano i brzo određivanje koncentracije vinske kiseline u uzorcima komercijalno pribavljenih voćnih sokova. Prilikom određivanja koncentracije vinske kiseline korištena je tekućinska kromatografija visoke djelotvornosti (HPLC) s UV/Vis detektorom. Istraživanje je bilo provedeno na HPLC (Knauer, Berlin, Njemačka) koji se sastojao od UV/Vis detektora, manualnog injektora, izokratne pumpe i analitičke kolone obrnute faze dimenzija 125,0 x 4,6 mm s punilom veličine 5 μm (LiChrospher RP-18, Merck, Darmstadt, Njemačka). Valna duljina detekcije na UV/Vis detektoru bila je podešena na 214 nm. Mobilna faza bila je 50 mM otopina fosfatnog pufera pH 2,8. Protok mobilne faze bio je podešen na 0,5 mL/min što je stvaralo tlak od 16,7 MPa. Iz osnovne matične otopine vinske kiseline (2,0 g/L) razrjeđenjem s MilliQ vodom pripremljen je niz standardnih otopina vinske kiseline u koncentracijskom rasponu od 0,125 do 1,0 g/L. Pri opisanim uvjetima na HPLC-UV/Vis vrijeme zadržavanja vinske kiseline na koloni iznosilo je oko 1,5 minute, a ukupna analiza trajala je 10 minuta. Dobivena kalibracijska krivulja je bila pravac s jednadžbom pravca y = 574,63x – 34,683 i pripadajućim koeficijentom korelacije R2 = 0,9972. Ponovljivost izražena kao relativna standardna devijacija (RSD) iznosila je manje od 10 % za sve ispitane standardne otopine. Granica dokazivanja bila je 0,01 g/L, a granica određivanja 0,03 g/L, što pokazuje da je metoda vrlo osjetljiva. Mjerenjem koncentracije vinske kiseline u komercijalno pribavljenim uzorcima voćnog soka (n = 5) dobivene su vrijednosti u rasponu od 1,15 g/L (sok od naranče; uzorak 1) do 1,54 g/L (sok od jabuke; uzorak 3). Dobivene koncentracije vinske kiseline u voćnim sokovima su bile relativno niske i bezopasne za ljudsko zdravlje. Iz dobivenih rezultata može se zaključiti da je razvijena metoda brza, pouzdana i precizna te se može koristiti za određivanje koncentracije vinske kiseline u uzorcima voćnih sokova. Zbog negativnog utjecaja visokih razina vinske kiseline na ljudsko zdravlje, važno je pratiti njenu koncentraciju u proizvodima namijenjenima konzumaciji ljudi. |
| Abstract (english) | The aim of this research was to introduce an analytical method that would allow precise, reliable and fast determination of tartaric acid concentration in samples of commercially obtained fruit juices. To determine the concentration of tartaric acid, high performance liquid chromatography (HPLC) with UV/Vis detector was used. This research was conducted on HPLC (Knauer, Berlin, Germany) consisted of UV/Vis detector, manual injector, isocratic pump and reverse phase analytical column (dimension: 125.0 x 4.6 mm, particle size: 5 μm; LiChrospher RP-18, Merck, Darmstadt, Germany). Wavelength on the UV/Vis detector was set at 214 nm. The mobile phase was 50 mM phosphate buffer with pH adjusted to 2.8. The mobile phase flow was 0.5 mL/min and the resulting pressure 16.7 MPa. From the tartaric acid stock solution (2.0 g/L) by diluting with MilliQ water a set of working standards solutions was prepared in a concentration range of 0.125 to 1.0 g/L. In described HPLC conditions, the tartaric acid retention time was approximately 1.5 minutes and the analysis lasted 10 minutes. Calibration curve was linear (equation: y = 574.63x – 34.683; correlation factor: R2 = 0.9972). Repeatability expressed as relative standard deviation (RSD) was less than 10 % for all tested working standard solutions. The limit of detection was 0.01 g/L and the limit of quantification was 0.03 g/L, indicating that developed method is very sensitive. The concentration of tartaric acid in commercially provided fruit juice samples (n = 5) ranged from 1.15 g/L (orange juice, sample 1) to 1.54 g/L (apple juice, sample 3). The obtained concentrations of tartaric acid in fruit juices were relatively low and harmless to human health. From the results it can be concluded that the developed method is fast, reliable and accurate and can be used to determine the concentration of tartaric acid in fruit juices. Due to the negative impact of high levels of tartaric acid on human health, it is important to monitor its concentration in products intended for human consumption. |
