Determination of metals in wine by ICP-OES: Comparative study of matrix effects and greenness of different sample preparation approaches

Determination of metals in wine is an important, but a challenging analytical task because wine is known to have a complex matrix. In inductively coupled plasma optical emission spectrometry (ICP OES) analysis, the complex matrix can create interferences, mainly due to the organic load. In this work, ten pretreatment procedures were tested and compared regarding the effects of matrix on the emission signals of Na, Ca, Mg, K, Mn, Fe, Cu, Zn, Cr, Co, Ni, Cd, Pb, and Y in ICP OES analysis. In addition, the greenness of the ten sample preparation procedures was compared using the "AGREEprep" software. Decreasing the Ar nebulisation flow rate to 0.6 L min⁻¹ , enabled us to maintain the plasma while introducing either a 12 % v/v ethanol solution or wine into the ICP. The ratio of magnesium ionic to atomic emission lines (Mg II at 280.270 nm / Mg I at 285.213 nm) was 9.7, indicating a robust plasma. The signals of Cr and Co were found to be more affected by the presence of ethanol in the analyzed matrix than Y (taken as internal standard in ICP OES), whereas the signals of elements such as K, Ca, Mg, Zn, Ni, Cd and Pb were found to be less affected than Y. The results indicated that alcohol removal and digestion with H 2 O 2 30 % provided comparable results to those using concentrated HNO 3 , demonstrating that the use of HNO 3 can be avoided, thus improving the grenessess of the sample digestion. The method involving alcohol removal and digestion with H 2 O 2 was validated by comparing it to the standardized analytical method OIV-MA-AS322–13. Subsequently, the method was applied to analyze nine real wine samples from Romania. • Sample pretreatment procedures for metals determination in wine were compared. • Ethanol in the sample increases the analytical signal of elements in ICP OES. • The effect of matrix on internal standards and analytes' signals may differ. • The greenness of the ten sample treatments was evaluated using the AGREEPrep tool. • Alcohol evaporation and hydrogen peroxide digestion provide accurate results.