2 research outputs found
Gas-Phase Separation of Drugs and Metabolites Using Modifier-Assisted Differential Ion Mobility Spectrometry Hyphenated to Liquid Extraction Surface Analysis and Mass Spectrometry
The present work describes an alternative
generic approach to LC–MS
for the analysis of drugs of abuse as well as their metabolites in
post-mortem tissue samples. The platform integrates liquid extraction
surface analysis (LESA) for analytes tissue extraction followed by
differential ion mobility spectrometry (DMS) mass spectrometry for
analytes gas phase separation. Detection is performed on a triple
quadrupole linear ion trap using the selected reaction monitoring
mode for quantification as well as product ion scan mode for structural
confirmatory analyses. The major advantages of the platform are that
neither chromatographic separation nor extensive sample preparation
are required. In DMS the combination of a high separation voltage
(i.e., up to 4 kV) together with organic modifiers (e.g., alcohols,
acetonitrile, acetone) added in the drift gas is required to achieve
the separation of isomeric metabolites, such as the ones of cocaine
and tramadol. DMS also separates morphine from its glucuronide metabolites,
which allows for preventing the overestimation of morphine in case
of fragmentation of the glucuronides in the atmospheric-to-vacuum
interface of the mass spectrometer. Cocaine, opiates, opioids, amphetamines,
benzodiazepines and several of their metabolites could be identified
in post-mortem human kidney and muscle tissue based on simultaneous
screening and confirmatory analysis in data-dependent acquisition
mode using an analyte-dependent compensation voltage to selectively
transmit ions through the DMS cell to the mass analyzer. Quantitative
performance of the LESA-DMS-MS platform was evaluated for cocaine
and two of its metabolites spotted onto a tissue section using deuterated
internal standard. Analyte’s responses were linear from 2 to
1000 pg on tissue corresponding to a limit of detection in the order
of nanograms of analyte per gram of tissue. Accuracy and precision
based on QC sample was found to be less than 10%. Replicate analyses
of cocaine and its metabolites in forensic samples showed an intra-
and inter-sections variability of less than 25%
Integration of Ion Mobility MS<sup>E</sup> after Fully Automated, Online, High-Resolution Liquid Extraction Surface Analysis Micro-Liquid Chromatography
Direct
analysis by mass spectrometry (imaging) has become increasingly
deployed in preclinical and clinical research due to its rapid and
accurate readouts. However, when it comes to biomarker discovery or
histopathological diagnostics, more sensitive and in-depth profiling
from localized areas is required. We developed a comprehensive, fully
automated online platform for high-resolution liquid extraction surface
analysis (HR-LESA) followed by micro–liquid chromatography
(LC) separation and a data-independent acquisition strategy for untargeted
and low abundant analyte identification directly from tissue sections.
Applied to tissue sections of rat pituitary, the platform demonstrated
improved spatial resolution, allowing sample areas as small as 400
μm to be studied, a major advantage over conventional LESA.
The platform integrates an online buffer exchange and washing step
for removal of salts and other endogenous contamination that originates
from local tissue extraction. Our carry over–free platform
showed high reproducibility, with an interextraction variability below
30%. Another strength of the platform is the additional selectivity
provided by a postsampling gas-phase ion mobility separation. This
allowed distinguishing coeluted isobaric compounds without requiring
additional separation time. Furthermore, we identified untargeted
and low-abundance analytes, including neuropeptides deriving from
the pro-opiomelanocortin precursor protein and localized a specific
area of the pituitary gland (i.e., adenohypophysis) known to secrete
neuropeptides and other small metabolites related to development,
growth, and metabolism. This platform can thus be applied for the
in-depth study of small samples of complex tissues with histologic
features of ∼400 μm or more, including potential neuropeptide
markers involved in many diseases such as neurodegenerative diseases,
obesity, bulimia, and anorexia nervosa