[JCopping]

Hi
 Totally new to this forum, so please bear with me.
 I'm currently involved in a water analysis project and am having some issues measuring Bi with our ICP OES. The background is very 'noisy' making it difficult to attain a good clear peak.
 I'm using wavelength 223.0nm. My analysis is using a Pb and Bi combined standard set with a matrix of distilled water and 1% nitric acid.
 My question is, as my sample concentrations are <20ppb, is it likely that standard addition is my only option to get the best results?

 Any suggestions would be great.
 Thanks
 Jo