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- Posts: 4
- Joined: Thu Feb 13, 2014 9:19 pm
I'm currently running a Dionex ICS-2100 IC for anions. I'm having an issue with my matrix spikes for chloride. Our calibration range is 5 to 200 for chloride. My matrix spikes are 25 ppm. My recoveries, however, are bad, typically around 65-75%. I work for an accredited lab and our SOP allowable recoveries are 80-120% for the data to be valid. Usually with a failling matrix spike, we reprep and rerun the spikes, and if those fail we report the data as having possible matrix interferences.
Now I've begun to experiment with the spikes, trying different amounts and trying different ways of spiking. Where we are there is a lot of road salt in the winter, and so my samples typically need a 5x dilution. I have tried diluting the sample and then spiking on top of the diluted sample. I have tried spiking on the straight sample and then diluting that. Each time the recoveries are terrible.
By now your first question to me is probably "Have you checked your standards?" The answer to this is yes. I use stock standards that are purchased (one as a calibration and one as a second source) and I use these same stock standards to make all of my calibration standards and to spike for my other 6 analytes. The spikes for the other analytes always have beatiful recoveries and I never have an issue with my calibration standards. The only analyte giving me trouble is chloride.
My main question is has anyone else ever experienced issues with chloride matrix spikes and does anyone have any advice on what I can try? I appreciate any thoughts you all have on the subject.