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 (TiO+)-Ti-47-O-16, (TiO+)-Ti-49-O-16 and (TiO+)-Ti-47-O-18 on Cu-63(+) and Cu-65(+) by detecting Cu+ as the product cluster ion Cu(NH3)(2)(+). As the signal of Cu-63(NH3)(2)(+) overlapped with that of Mo-97(+) which existed in the samples, Cu-65(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++2NH(3)-->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.