My DMEM media and cells' supernatant turned slight yellow upon addition of freshly prepared Griess reagent (1% sulphanilamide + 0.1% NED in 2.5% phosphoric acid). Has anyone encountered such problem and what is the cause of it?
No. But as I recall the Griess reaction requires all Nitrates to be reduced to Nitrites (which are reactive). This could be confirmation that the color formation is below the LOQ. Thus, spike your sample with a series of Nitrite concentrations and confirm it is stable in your matrix. If your sample matrix does not interfere over time the slope and y-intercept should be the same as your standards.
HI Bruce, it's actually the interference from my DMEM. I've switched to using phenol red free DMEM and it's ok now. Thanks!
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