A greener, rapid and accurate microwave-assisted hydrogen peroxide digestion method for ICP-OES determination of heavy metals in pet food samples

Abstract

Microwave-assisted hydrogen peroxide digestion (MW-AHPD) method for determination of Cd, As, Pb, Sn, and Cr in South African pet food samples by inductively coupled plasma-optical emission spectroscopic (ICP-OES) is reported. Multivariate tools and wheat flour certified reference material (FAP80467) assessed limiting factors and reproducibility of the methods respectively. The resulted optimum conditions were: 200 °C, 40 mins, 0.5 g, and 5 mol/L for temperature, time, sample mass and H2O2 concentration, respectively. The method demonstrated excellent accuracy (96-98%), reproducibility (≤ 2.1%) and high detection limits (0.0675 to 0.3765 µg/g). Then, real pet food samples made from maize, rice, vegetables, fish, and wheat were digested and concentration levels of Cd, Pb, As, Cr and Sn ranged between 11.2-22.6, 6.4-11.9, 3.44-13.4, 0.44-2.98 and 0.18-0.98 µg/g, respectively. The three metal ions were above the minimum tolerable limits (Cd: 10 µg/g, Pb:10 µg/g, As: 12.5 µg/g) for some of the fish and wheat based pet food according to the South African regulatory standard. Furthermore, using the AGREEPrep metric tool the method was assessed and had a score of 0.76, confirming its greenness. These findings present MW-AHPD method as an alternative for determination of heavy metals in pet food by ICP-OES.