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Internal standard application strategies in mass spectrometry imaging by desorption electrospray ionization mass spectrometry
Author(s) -
Perez Consuelo J.,
Ifa Demian R.
Publication year - 2021
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.9053
Subject(s) - chemistry , mass spectrometry , chromatography , analytical chemistry (journal) , electrospray ionization , desorption electrospray ionization , desorption , electrospray , mass spectrometry imaging , ionization , ion , thermal ionization mass spectrometry , adsorption , organic chemistry
Rationale We developed a model case study to evaluate three internal standard (IS) application strategies (methods I–III) using the psycholeptic phenobarbital (PB) and the isotopically labelled IS phenobarbital‐D5 (PB‐D5) from in vitro dosed tissues of the golden apple snail ( Pomacea diffusa ) by desorption electrospray ionization mass spectrometry imaging (DESI‐MSI). Methods In method I, the IS was deposited as microspots on top of 10 μm thick snail tissues; in method II, a thin IS film was applied; and in method III, the IS was spiked into the DESI solvent spray. DESI‐MSI analyses were performed using a Thermo LTQ mass spectrometer equipped with a custom‐built DESI source and two‐dimensional moving stage. PB ( m / z 231) and PB‐D5 ( m / z 236) were monitored in selected ion monitoring mode between m / z 227 and 239. Results The analytical performance of two IS strategies (methods I and II) in DESI‐MSI was evaluated based on an intra‐ and inter‐day precision assay, an accuracy assessment, and statistical analysis. In the inter‐day DESI‐MSI assay, method I exhibited better precision (6.5%–7.4%) than method II (10.7%–17.6%) between 10 and 100 ng/μL. In the accuracy assessment, PB quality controls of 75 ng/μL were back‐calculated as 71 ± 4 and 83 ± 9 ng/μL, resulting in relative errors of −5% and 11% for methods I and II, respectively. Method III did not work under the experimental design and was not evaluated. Conclusions Three IS application strategies were investigated and compared for a routine quantitative DESI‐MSI approach. Methods I and II were not statistically significantly different as shown by a Bland–Altman plot, suggesting that these two methods can be used interchangeably. However, method III requires further research for future quantitative DESI‐MSI analyses.