Bioprofiling
on the planar chromatogram with in situ biological/enzymatic
assays is a powerful bioanalytical screening tool for the nontargeted
detection of known and especially unknown/unidentified bioactive compounds
directly in multicomponent mixtures (e.g., foods, spices, and botanicals).
However, together with the bioactive zone, the adsorbed bioassay medium
is eluted into the mass spectrometer (MS) and interfering with evaluation.
Another sample track without bioassay has thus been handled in parallel.
Hence, for a direct zone elution from the bioautogram, different setups
were investigated to reduce the impact of the bioassay medium load.
A biocompatible filter, orthogonal reversed-phase/cation-exchange
columns (RP/IEX-HPLC), UV/vis detector, and a Rheodyne valve were
installed between the zone eluting interface (after normal-phase high-performance
thin-layer chromatography-multi-imaging-bioassay, NP-HPTLC-UV/vis/FLD-bioassay)
and the MS. For the negative electrospray ionization mode (ESI–), an RP-18e-HPLC column and valve switch were exploited.
After gradient optimization, the RP-column retarded the eluted polar
compounds and split-off the salts of the bioassay medium in the first
minutes. This reduced the bioassay load and separated analyte signals
thereof. However, most bioassay medium mass signals were predominantly
detectable in ESI+-MS. Here, the reduction of bioassay
matrix signals was achieved by integrating a mixed-mode RP/IEX column.
Finally, two different superhyphenations were successfully proven:
NP-HPLC-UV/vis/FLD-bioassay-RP-HPLC-UV/vis-ESI–-MS
with a valve switch and NP-HPLC-UV/vis/FLD-bioassay-RP/IEX-HPLC-UV/vis-ESI±-MS with or without it. Although the original bioprofiling
(NP-HPTLC-UV/vis/FLD-bioassay) was prolonged from 3 to 13 min per
sample, such superhyphenations covering chemistry/biology/mass spectrometry
are considered as an efficient nontarget bioanalytical tool for fast
evaluation of complex samples.