Capillary Electrophoresis-Mass Spectrometry at Trial by Metabo-Ring: Effective Electrophoretic Mobility for Reproducible and Robust Compound Annotation

Capillary zone electrophoresis-mass
spectrometry (CE-MS) is a mature
analytical tool for the efficient profiling of (highly) polar and
ionizable compounds. However, the use of CE-MS in comparison to other
separation techniques remains underrepresented in metabolomics, as
this analytical approach is still perceived as technically challenging
and less reproducible, notably for migration time. The latter is key
for a reliable comparison of metabolic profiles and for unknown biomarker
identification that is complementary to high resolution MS/MS. In
this work, we present the results of a Metabo-ring trial involving
16 CE-MS platforms among 13 different laboratories spanning two continents.
The goal was to assess the reproducibility and identification capability
of CE-MS by employing effective electrophoretic mobility (μeff) as the key parameter in comparison to the relative migration
time (RMT) approach. For this purpose, a representative cationic metabolite
mixture in water, pretreated human plasma, and urine samples spiked
with the same metabolite mixture were used and distributed for analysis
by all laboratories. The μeff was determined for
all metabolites spiked into each sample. The background electrolyte
(BGE) was prepared and employed by each participating lab following
the same protocol. All other parameters (capillary, interface, injection
volume, voltage ramp, temperature, capillary conditioning, and rinsing
procedure, etc.) were left to the discretion of the contributing laboratories.
The results revealed that the reproducibility of the μeff for 20 out of the 21 model compounds was below 3.1% vs 10.9% for
RMT, regardless of the huge heterogeneity in experimental conditions
and platforms across the 13 laboratories. Overall, this Metabo-ring
trial demonstrated that CE-MS is a viable and reproducible approach
for metabolomics.