The development of a novel method for the direct quantification
of BVO in soft drinks by HPLC-ESI-MS posed a number of practical
challenges. BVO is comprised of a complex mixture of high molecular
weight triglycerides that vary in their brominated fatty acid
composition. Due to its low polarity, BVO is very highly retained
in most chromatographic systems, and does not easily undergo
ionization in LC–MS interfaces (electrospray or atmospheric pressure
chemical ionization). Furthermore, the somewhat variable
composition of soft drinks, and thus the analytical matrix, presented
an extra challenge for a method that aimed to simplify
the sample preparation to the maximum extent possible. While
we initially contemplated the synthesis of a (commercially
unavailable) isotope-labeled internal standard that could obviate
a number of these challenges, we decided not to follow this route
in order to keep the analytical procedure as simple as possible. We
have thus implemented a standard addition method, capable of
addressing matrix effects, and the expected day-to-day variability
in the absolute response of the HPLC-ESI-MS instrumentation. Considering
the legal limit imposed by the FDA for BVO in soft drinks
(15 lg/mL), the method was validated in the range of 5–25 lg/mL,
and the sample spiking was conducted at 15 lg/mL.