Commercial formaldehyde standard for mass calibration in mass spectrometry

Abstract

Common calibration standards for mass spectrometry can be a source of many problems including instrument contamination, ionization suppression and formation of unidentified ions during subsequent analysis. In this article, we present a new approach for the calibration of mass analyzers such as a quadrupole-time-of-flight mass spectrometry using a diluted solution of commercial formaldehyde. Formaldehyde is an inexpensive and commonly used solvent, and its intrinsic polymerization leads to the formation of polyoxymethylene (POM) oligomers, which are excellent multiple calibration standards for a low-mass spectral region (up to m/z 400) in the positive and negative mode of electrospray ionization. We explore the nature and origin of these polymeric species and attributed them to chemical reactions of formaldehyde and stabilizing agents in commercial formaldehyde solutions and during electrospray ionization. In contrast to other calibrants, POM oligomers do not contaminate the instrument and can easily be removed from the sample delivery system. Using tandem mass spectrometry, we elucidate the structures of the detected POM oligomers and report their reference masses, which are tightly spaced by 30 mass units. In our calibration method, mass errors of <5 ppm can be obtained from m/z 20-400 using external calibration with a simple one-point zero-order correction of spectral data and without the need for operation of a dual spray or internal calibrants. Our approach will be particularly useful for those interested in the analysis of fragile ions with low m/z values and can function at instrumental conditions required for analysis of the most labile metabolites and environmental contaminants.

Improved mass resolution and mass accuracy in TOF-SIMS spectra and images using argon gas cluster ion beams

“…Irganox V R 1010 was selected for external mass calibration [29][30][31][32] because this organic material is inexpensive and commonly used to evaluate the performance of cluster ion beams through depth profiling. [7][8][9] Further, positive and negative spectra that contain well-known multiple characteristic and molecular peaks from the low-to the high-mass spectral regions (up to m/z 1200) can be obtained from this material in a reasonable time (less than 10 s).…”

“…As with the delayed extraction method, the external mass calibration method is also widely used in various mass spectrometry techniques. [29][30][31][32] Although these two methods, delayed extraction and external mass calibration, are not new, they will be useful in identifying unknown materials when newly applied to an Ar-GCIB-TOF-SIMS analysis.…”

Synthesis of Tumor-Associated LeaLex Hexasaccharides: Instability of a Thiol-Containing Oligosaccharide in Mass Spectrometry and Hypermetalation Detected by ESI FAIMS

“…7c Coupled with "soft" Q-TOF mass spectrometry, it is capable of detecting extremely labile ions with minimal fragmentation. Mass calibration was carried out using formaldehyde, as described recently for use with "soft" Q-TOF mass spectrometry, 19 and it appeared that all ions detected for compounds 2−4 and 23 were doubly charged. Hexyl glycoside 2, aminohexyl glycoside 3, and hexyl disulfide analogue 23 gave stable doubly charged ions through protonation, or adduction of ammonium or sodium.…”

“…The mass calibration was carried out using formaldehyde, as described recently for use with "soft" Q-TOF mass spectrometry. 19 Mass accuracies were <5 ppm and were sufficient to determine the elemental composition of the product ions presented. The product ions are listed in the Supporting Information.…”

“…6,170.4,170.1,170.0,169.5,169.4,161.8 (CO),139.0,138.9,138.6,138.2,137.8 (quat Ar),128.5,128.4,128.3,128.2,128.1,128.0,127.6,127.5,127.4,127.3 (Ar), 100.7 (C-1B′), 99.5 (C-1A), 99. 3, 20.9, 20.8, 20.6, 20.5 yl-3-O-[6-O-benzyl-3-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-4-O-(2,3,4- (19). A solution of the glycosyl acceptor 18 (32.6 mg, 0.01712 mmol) and known 11 thioglycoside donor 8 (40.9 mg, 0.08559 mmol, 5 equiv) in dry CH 2 Cl 2 (2 mL) containing freshly activated molecular sieves 4 Å (100 mg) was stirred under N 2 for 1 h 30 min at rt.…”