[Babcock_Hall]

Hello Everyone,

In isotope dilution mass spectrometry, a multiply deuterated internal standard is typically added at the start of a purification protocol in clinical or forensic toxicology, for example.  How does the sensitivity of the MS experiment change from protium to deuterium, or are they equally sensitive to the detector?  I imagine that use of a standard curve would correct for differences, but I am wondering whether or not there should be differences.  Put another way, should a standard curve have a slope of unity?

[Babcock_Hall]

Quantitative Applications of Mass Spectrometry, Lavagnini I, et al., Wiley (2006) ISBN: 0-470-02516-6
I found a chapter covering quantitative mass spectrometry that had a standard curve in it.  The authors made a series of five mixtures, keeping the concentration of d₃-testosterone constant while varying the concentration of testosterone.  Both compounds were converted into di-heptafluorobutyryl derivatives.  The standard curve placed R, which is the area at m/z 680 over the area at m/z 683 on the y-axis, and concentration of testosterone on the x-axis.  By eyeball, the slope looks to be close to one.  I will keep reading...