Identification of the interfering compound
The extreme specificity of the HA in strawberry tree honey
and the close retention times of HMF and HA observed, in the
RP-HPLC official method at the typical phenolic acids zone,
led us to think that HA could be an authoritative “candidate”
as the interfering species in the chromatographic determination
of HMF.
Our supposition was confirmed by the following findings:
• The chromatogram of pureHAdissolved inwater recorded
in the same conditions as the RP-HPLC determination of
HMF shows a sharp peak at an RT of 11.46 min, i.e. very
close to the HMF one (typical RT = 10.42 min) recorded in
the same conditions.
• The spiking of a sample of multifloral honey (in which the
HA was previously found absent) with a known amount of
HA causes the loss of chromatographic resolution in the
HMF zone of the chromatogram.
• The spiking of a sample of strawberry tree honey with a
known amount of HA causes the right side of the overlapped
peak system to rise.