Direct extraction of urinary analytes from undeveloped reversed-phase thin layer chromatography plates using a solvent gradient combined with on-line electrospray ionisation ion mobility-mass spectrometry

Abstract

The direct extraction of urinary analytes deposited on reversed-phase thin-layer chromatography (RP-TLC) plates is demonstrated using a solvent gradient extraction procedure without prior chromatographic development. The surface sample probe TLC-MS interface used for the gradient extraction is compared to direct loop injection into the electrospray ion source for biofluid profiling. The gradient elution is shown to enhance ion intensities, as urinary salts are eluted in aqueous formic acid in the early part of the gradient reducing ion suppression. The retention of urinary components on the C18 RP-TLC plate was confirmed by monitoring analyte responses with, and without, an aqueous wash phase prior to the solvent gradient extraction. The use of gradient elution allows fractionation of the complex biological matrix as a result of differential retention of urine components on the undeveloped RP-TLC plate. The direct gradient analysis of TLC plates has also been combined with ion mobility-mass spectrometry to further resolve the complex urinary profile and identify co-eluting compounds.

High-Throughput Solvent Assisted Ionization Inlet for Use in Mass Spectrometry

“…Mapping of select compounds in microtiter plate wells is an obvious application of this new technology, but any area in which fast analyses are valued such as proteomics, metabolomics, and lipidomics could be impacted. It is our expectation, based on current performance, that some of these new ionization technologies in conjunction with IMS-MS, − ETD, , and LC, − will have considerable advantages relative to current analytical methods. The potential of these methods for direct analyses of complex mixtures will be achieved using high mass resolution available with Fourier transform instruments …”

Direct Determination of Urinary Creatinine by Reactive-Thermal Desorption-Extractive Electrospray-Ion Mobility-Tandem Mass Spectrometry.

“…These results show that the acylation significantly increases the volatility of creatinine from a decomposition point of ∼300 °C to less than the TD probe temperature of 100 °C and that the reaction is sufficiently rapid to allow direct on-probe derivatization and thermal desorption. Since only volatile molecules and derivatives capable of being thermally desorbed at 100 °C will interact with the ESI plume, ion suppression by the urine matrix, observed when diluted urine is directly infused into an ESI ion source, 10 is avoided by this R-TD ambient ionization approach.…”

“…The direct analysis of urine by electrospray ionization mass spectrometry is problematic, because of ion suppression effects arising from the high salt content of urine . Prior separation by high performance liquid chromatography (HPLC) or GC, hyphenated with MS, is therefore usually used for the detection of excreted metabolites relating to disease states such as lung disorder, diabetes, and cancer. − It is common practice in the determination of urinary metabolites to normalize the target molecule concentration to the excretion of creatinine .…”