Metal selectivity and interference. When a palladium-catalyzed reaction is employed, palladium is obviously the major concern with respect to metal contamination. However, other metal contaminations may be present because other reagents, glassware, or water used during purification may contain copper and iron, among other heavy metals. The previous method was fairly selective for palladium, but platinum produced approximately one-fifth of the signal compared to palladium. Figure shows that the current method is more selective for palladium (41810 A.U.), with platinum (9242 A.U.) being second most reactive. More specifically, after the background (no metal; 5677 A.U.) subtraction, we determined that the selectivity between palladium and platinum was 10:1.