Chromatography Forum

Okay, I am going in circles so I thought I might as well ask.

From my other postings, it is obvious I had been working on LCMSMS analysis on melamine in milk samples.

I am told I must attain less than 2% RSD. I had tweaked all that I can and is still getting 3-4% RSD at a minimum. Sometimes, it gets as high as 12% but mostly less than 5%.

Is a <2% RSD even possible with LCMSMS, when analysing actual samples???

When I was doing Bioanalytical assays by LC-MS-MS we had our SST criteria set at RSDs <=5% as our default.

From my other postings, it is obvious I had been working on LCMSMS analysis on melamine in milk samples.

I am told I must attain less than 2% RSD.

While I understand the grave consequences of finding toxic levels of melamine in milk samples... may I ask why, from a practical standpoint, less than 2% RSD would be necessary? If I knew with 95% certainty that a milk sample contained a certain concentration of melamine plus or minus 10%, would that 10% error have any bearing on how toxic the milk is?

When I was working in a routine lab, the default was set at <5-10%, depending on the type of samples.

Now I am working in a metrology lab, so they expect high precision and accuracy.

With GCMS, I am able to attain RSD <2%. However, no matter how hard I try to tweak the parameters, the minimum I obtained for LCMSMS is 3-4%.