Chloride determination by ion chromatography in petroleum coke after digestion by microwave-induced combustion

Microwave-induced combustion was applied to petroleum coke digestion in closed vessels for further chloride determination by ion chromatography. Samples were pressed as pellets and placed on a quartz holder. Combustion was performed using oxygen pressure of 2 MPa and 50 μl of 6 mol l−1 NH4NO3 as aid for ignition. Recoveries from 97 to 102% were obtained for all studied absorbing solutions (water, H2O2, Na2CO3 or (NH4)2CO3). Accuracy was evaluated using certified reference materials with agreement better than 98% using water as absorbing solution with reflux step. The limit of quantification was 3.8 μg g−1.