Determination of iron in Croatian olive oils using GF-AAS technique

Abstract

Budući da elementi u tragovima imaju negativne učinke na oksidativnu stabilnost maslinovog ulja i ljudsko zdravlje, cilj ovog rada bio je odrediti koncentraciju željeza, elementa važnog u procjeni kvalitete maslinovih ulja. Analiza ovog elementa u tragovima u 35 uzoraka maslinovog ulja porijeklom iz Republike Hrvatske provedena je metodom atomske apsorpcijske spektrometrije grafitnom tehnikom. Uzorci maslinovog ulja sadrže visoki udio lipidnih sastavnica te predstavljaju složen organski sustav za određivanje metala. U cilju dobivanja homogene otopine prikladne za određivanje metala grafitnom tehnikom svi analizirani uzorci prethodno su spaljeni mikrovalnom digestijom. Provedenim istraživanjem uočene su prednosti određivanja koncentracije željeza grafitnom tehnikom nakon uklanjanja složenog matriksa spaljivanjem uzoraka mikrovalnom digestijom. Niske RSD vrijednosti upućuju na zadovoljavajuću ponovljivost i postupka mikrovalne digestije i određivanja koncentracije metala grafitnom tehnikom. Na temelju dobivenih vrijednosti LOD i LOQ te definirane NDK, provedene metode grafitne tehnike mogu se smatrati prikladnim za određivanje analiziranog metala u maslinovim uljima. Koncentracije željeza u istraživanim maslinovim uljima bile su ispod najviše dozvoljene koncentracije definirane važećim pravilnikom osim u jednom uzorku te upućuju na dodatno praćenje zastupljenosti ovog metala u hrvatskih maslinovih ulja. Potrebna su daljnja istraživanja u okviru zastupljenosti drugih metala u maslinovom ulju. Istraživana maslinova ulja kategorizirana su kao ekstra djevičansko maslinovo ulje, dok je manji broj uzoraka klasificirano u skupinu djevičansko maslinovo ulje.Since heavy metals and trace elements have negative effects on the oxidative stability of olive oil and human health, the aim of this study was to determine the concentrations of iron, the element important for the assessment of olive oil quality. The analysis of this trace element, in 35 samples of olive oil, originating from the Republic of Croatia, were performed by atomic absorption spectrometry using graphite technique. The samples of olive oil contain a high proportion of lipid components, and thus represent a complex organic system for the determination of metal. In order to obtain a homogeneous solution suitable for the determination of metal by graphite technique, all analyzed samples were previously prepared using a microwave digestion system. The obtained results have shown the advantages of iron concentration determination by graphite technique after removal of complex matrix by burning samples by microwave-assisted digestion. Low RSD values point out the exceptional/satisfactory repeatability of microwave digestion procedures and the metal concentration determination by graphite technique. Based on the obtained LOD and LOQ values as well as the defined NDK, conducted graphite technique methods can be considered as suitable to determine the analyzed metal in olive oils. The concentrations of iron in the investigated olive oils were below their maximum permissible concentrations as defined by the valid rulebook, except in one sample. The presented data point to the exceptional quality of Croatian olive oils. Further research should be conducted to evaluate the presence of other metals in the investigated olive oil samples. The investigated olive oils are categorized as extra virgin olive oil, while a small number of samples are classified into the group of virgin olive oil