Determination of heavy metal content in cocoa samples using TXRF-W, TXRF-Mo and EDXRF techniques

Abstract

Plod stabla kakaovca jest zrno kakaa koje je ključni sastojak u proizvodnji kakao praha i čokolade. Zbog velike zastupljenosti u ljudskoj prehrani, nužno je poznavanje sastava kakaa kako bi se osigurala kvaliteta i sigurnost samih proizvoda. Glavni cilj ovog rada jest odrediti elementni sastav kakaa te usporediti rezultate dobivene različitim analitičkim tehnikama (TXRF-W, TXRF-Mo, EDXRF). Uzorci su pripremljeni mikrovalnom digestijom te u obliku peleta te je određeno prisustvo sljedećih elemenata: željezo, bakar, cink, rubidij, stroncij, mangan, nikal i krom. Priprema uzorka u obliku peleta jeftinija je, manje zahtjevna i ekološki prihvatljivija u odnosu na mikrovalnu digestiju. Analizom je utvrđeno da se rezultati dobiveni različitim analitičkim tehnikama podudaraju (posebice između TXRF-Mo i EDXRF). Sve su se tehnike pokazale kao vrlo korisne budući da omogućavaju identifikaciju i kvantifikaciju vrlo niskih koncentracija elemenata prisutnih u uzorcima kakaa, s naglaskom na TXRF-Mo tehniku koja se pokazala kao najosjetljivija.The fruit of the cocoa tree is the cocoa bean which is a key ingredient in the production of cocoa powder and chocolate. Since cocoa is widely used in the human diet, it is necessary to know the composition of cocoa in order to ensure quality and safety of the products themselves. The main goal of this work is to determine the elemental composition of cocoa and to compare the results obtained by different analytical techniques (TXRF-W, TXRF-Mo, EDXRF). The samples were prepared by microwave digestion and in the form of pellets and the presence of the following elements was determined: iron, copper, zinc, rubidium, strontium, manganese, nickel and chromium. Sample preparation in the form of pellets is less-expensive, simpler and more environmentally friendly than microwave digestion. The analysis showed that the results obtained with the different analytical techniques were consistent (especially between TXRF-Mo and EDXRF). All techniques have proven to be very effective, as they allow the identification and quantification of very low concentrations of the elements present in cocoa samples, with the TXRF-Mo technique which proving to be the most sensitive