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Multiplexing Multiple Methods to Maximize Workflow Efficiency in LC-MS Laboratories
Overview
Purpose:
To demonstrate the performance of research and forensic
methods running simultaneously across most or all channels of a
multichannel ultra-high performance liquid chromatography (UHPLC)
system interfaced to a tandem mass spectrometer (MS/MS) in order
to maximize sample throughput and workflow efficiency.
Methods:
Reversed-phase liquid chromatography of analytes with
corresponding stable-isotope internal standards eluting from up to
four UHPLC channels into a common ion source of a triple-
quadrupole mass spectrometer were used to measure blood serum
levels of the following compounds for research purposes:
25-OH-Vitamins D2 & D3
after protein precipitation and
Methylmalonic Acid
after protein precipitation and
butylation, eluting to an atmospheric-pressure chemical
ionization (APCI) source;
or to measure urine levels of the following forensic compounds:
Buprenorphine & Norbuprenorphine
after hydrolysis and
Ethyl-Glucuronide & Ethyl Sulfate
after dilution, eluting into a
heated electro-spray ionization (HESI) source.
Results:
Desired quantitation ranges, accuracy and repeatability
criteria were achieved for each application when various specimen
batches ran on any of the channels of the 4-channel UHPLC system.
Typically, internal standard (IS) peak area counts showed less than
20% coefficient of variability (CV) among calibrators, QCs and
specimens (n = 20) on any and across all 4 channels. Retention time
variations through these batches were less than 3% CV. Calculated
amounts were within +/- 15% of theoretical amounts.
Introduction
Many laboratories run several different LC-MS methods in series on a
single channel LC-MS system. If the methods involve different ion
sources, columns and mobile phases, the changeover is time
consuming, labor intensive and increases the risk of mistakes and
contamination. A four-channel UHPLC system multiplexed into one
mass spectrometer permits parallel batches of up to four different
methods utilizing a common ion source and unique columns and
mobile phases to be completed in a fraction of the time and effort.
Methods
Sample Preparation:
“Neat” specimens were prepared in HPLC
-grade solvents -
acetonitrile, methanol, water - using standards purchased from
Cerilliant
(Round Rock, TX).
Blood serum specimens and corresponding calibrators and quality
controls (QCs) were subjected to protein precipitation by mixing 1:2
Resu
Multi-ch
FIGURE
FIGURE
Start
FIGURE
Desired
25-OH-V
throughp
batches
around 5
FIGURE