Hi all,


With your permission, I would like to make some comments since I work with
HPLC-MS (University of São Paulo).

The results from the labs cannot be compared since they report different
things. LC-IRMS reports isotope ratios and not % of each sugar. Look at the
unit: delta 13C per mille (d13C%0). These are negative values in certain
range (mean around - 24) and the less negative values (-16 to -13) indicate
adulteration by C4 plant sugars. As a consequence, one cannot add these
values to calculate total solids. Regarding disaccharides and mass spec,
the samples are burned to CO2 before entering the MS. So, there is no
structural information or m/z being measured for the sugars (just CO2). The
13C ratios for glucose, fructose, di and trisaccharides are calculated
independently because they are separated by HPLC before entering the
combustion chamber and MS. On the other hand, the AOAC HPLC method reports
the % of each sugar, a very different thing. But, at the end, both results
agree as adulterated honey.
Regarding HPLC, the term "pressure" is deprecated. IUPAC recommends "High
Performance Liquid Chromatography".

Felipe, from Brazil

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