ICP-MS Decreasing Sensitivity Over Time?
I work with an ICP-MS and did not get a huge amount of training prior to my predecessor leaving the company. Recently, I've noticed our instrument losing mercury sensitivity over the time of the batch running. I did a study using different concentrations of HCl (0.5%, 0.75% and 1%), and 0.5% held the best mercury concentrations over the time the batch took to run. This is the concentration we were using originally, and now I'm not sure what the problem could be.
The only thing that has changed recently is the addition of more rinses of 5% HNO3 1% HCl, 1g/mL EDTA, and diluent. There was a previous problem with mercury carryover, and this is how I resolved that problem. I've looked into gold chloride as another possible solution for the carryover, but I don't want to change the procedure too much. Any advice out there?