Ajp. Hofte et al., CHARACTERIZATION OF HOP ACIDS BY LIQUID-CHROMATOGRAPHY WITH NEGATIVE ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY, Journal of the American Society of Brewing Chemists, 56(3), 1998, pp. 118-122
The analysis of hop acids, humulones and lupulones, with negative elec
trospray ionization mass spectrometry (MS) is described for two differ
ent chromatographic systems. One system focuses on the complete resolu
tion of the ad- and normal homologues implying that no optimal mass sp
ectrometric parameters can be used, whereas the other system makes no
compromise to the MS and yields a high sensitivity. The latter system
is especially suitable for the fast screening of bitter acids. With th
is system, the detection limit with selected ion monitoring (SIM)-MS c
ould be estimated to be 10 ng/ml for the humulones and 5 ng/ml for the
lupulones. The presence of hop acids in beer was investigated and was
found to be positive for humulones, whereas lupulones could not be de
tected.