Determination of copper in coal fly ash in the presence of excess titanium by dynamic reaction cell inductively coupled plasma mass spectrometry

Inductively coupled plasma quadrupole mass spectrometry (ICP–QMS) was used for the accurate determination of copper in coal fly ash samples in the presence of excess titanium, using the reaction of Cu+ ions with NH3 in the cell. The method eliminated the effect of polyatomic isobaric interferences at m/z 63 and 65 caused by the formation of 47Ti16O+, 49Ti16O+ and 47Ti18O+ on 63Cu+ and 65Cu+ by detecting Cu+ as the product cluster ion Cu(NH3)2+. As the signal of 63Cu(NH3)2+ overlapped with that of 97Mo+ which existed in the samples, 65Cu(NH3)2+ was detected at m/z 99. The effect of the operating conditions of DRC system was studied in order to obtain the best signal to noise ratio for Cu(NH3)2+ at m/z 99. The formation of Cu(NH3)2+ was through the clustering reaction Cu++2NH3→Cu(NH3)2+ which resulted in the separation of analyte from the interfering oxide. The detection limit for Cu(NH3)2+ was 0.015 ng mL–1 as Cu. The method was applied to the determination of copper in NIST SRM 1633a and 1633b coal fly ash reference materials. The precision between sample replicates was better than 2.0% and the analysis results were in good agreement with the certified values.