ONLINE STANDARD ADDITIONS WITH DIRECT INJECTION NEBULIZATION FOR INDUCTIVELY COUPLED PLASMA MASS-SPECTROMETRY

A flow injection method for on-line standard additions is described. A 500-mu-L sample solution is injected into a flowing stream via a metal-free flow injection valve. Standard solutions (50-mu-L) are sequentially introduced through a second valve. The two streams mix in a PEEK tee before they are nebulized into the ICP. The advantages of the method of standard additions for matrix correction are retained, but the time-consuming solution preparation steps for conventional standard additions are eliminated by using flow injection techniques and a direct injection nebulizer. Nine toxic elements in undiluted urine were determined in less than 5 min. Possible effects of sample viscosity on accuracy are investigated. Evidence for a change in the background when seawater is nebulized is also presented.