Mass Spectrometry Of Products Research Articles

Endogenous Ouabain: Recent Advances and Controversies.

In this brief article, we summarize recent reports about endogenous ouabain (EO), a cardiotonic steroid hormone. This includes analysis of mammalian EO, the discovery of EO isomers, regulation of intracellular signaling by EO, and the roles of EO in hypertension, pregnancy, and heart and kidney diseases. Novel ouabain-resistant mice that elucidate the key roles of α2 Na+ pumps and their cardiotonic steroid-binding site are also discussed. EO was first identified in human plasma 25 years ago.1,2 Despite confirmation in humans and other mammals with mass spectrometry (MS; Figure; Figures S1–S6 in the online-only Data Supplement), nuclear magnetic resonance, and combined liquid chromatography (LC)–immunology methods,3–6 human EO has remained controversial.7 New analytic studies and related findings should allay skepticism. For example, employment of multistage MS (MS–MS and MS–MS–MS) to examine the effects of pregnancy and of central angiotensin (Ang) II infusion on EO in rat plasma led to the discovery of 2 novel EO isomers.8,9 Isomer 1 has MS–MS and MS–MS–MS product ion spectra indistinguishable from those of EO, but is slightly more polar than EO; it binds to the antibody used in our radioimmunoassay. Isomer 2 is slightly less polar than EO, has a distinct MS–MS–MS spectrum, and cross reacts weakly in our radioimmunoassay. The primary structural difference(s) between EO and these isomers may involve the steroid nucleus. Importantly, neither isomer was previously described or is detectable in commercial (plant) ouabain.8,9 Figure. Endogenous ouabain determined by liquid chromatography (LC)–mass spectrometry (MS)–MS in plasma from patients with cardiomyopathy. A , Capillary LC–MS–MS product ion chromatogram for a plasma extract from a patient with cardiomyopathy. The ion current peaks represent positively charged molecular product ions with an M+Li+/z ratio equivalent to the lithiated aglycone of ouabagenin …

Differentiation of regioisomeric ring-substituted fluorophenethylamines with product ion spectrometry

The electron ionization (EI) of aromatic ring-substituted isomers gives virtual identical mass spectra which seriously affects their analysis. Especially regioisomeric meta- and para-ring-substituted compounds cannot show any ortho-effect reactions making their differentiation by mass spectrometry impossible. Furthermore o-, m- and p-substituted compounds can only be separated insufficiently by chromatography due to their very similar retention that do not allow univocal identification. Product ion mass spectrometry has proved to be a useful tool to differentiate structurally closely related fluorophenethylamines even in the case of the meta- and para-isomers. A series of N-alkylated o-, m- and p-fluoroamphetamines and 1-(4-fluorophenyl)butan-2-amines have been synthesized in microscale and studied by product ion spectrometry. The combination of chemical ionization (CI) and product ion spectrometry of hydrogen fluoride loss ions [M+H−HF] + allows a univocal differentiation of all studied fluoro-substituted phenethylamines without prior derivatization. This method with submicrogram detection limits provides great advantages for the differentiation between aromatic regioisomeric fluorophenethylamine designer drugs where other methods such as nuclear magnetic resonance (NMR) spectrometry lack sufficient sensitivity or might fail because complex mixtures have to be analyzed.

Comparison of Three Types of Mass Spectrometer for High-Performance Liquid Chromatography/Mass Spectrometry Analysis of Perfluoroalkylated Substances and Fluorotelomer Alcohols

The performance of three different types of mass spectrometers (MS) coupled to high performance liquid chromatography (HPLC) was compared for trace analysis of perfluoroalkylated substances (PFAS) and fluorotelomer alcohols (FTOHs). Ion trap MS in the full scan and product ion MS2 mode, time-of-flight (TOF) high resolution MS and quadrupole MS in the selected ion mode as well as triple quadrupole tandem MS were tested. Electrospray ionisation in the negative ion mode [ESI-] was best suited for all instruments and compounds. PFAS could only be separated by a buffered mobile phase, but the presence of buffer suppressed the ionisation of FTOHs. Therefore, two independent chromatographic methods were developed for the two compound classes. Mass spectra and product ion spectra obtained by in-source and collision induced dissociation fragmentation are discussed including ion adduct formation. Product ion yields of PFAS were only in the range of 0.3 to 12%, independent from the applied MS instrument. Ion trap MS2 gave product ion yields of 20 to 62% for FTOHs, whereas only 4.1 to 5.8% were obtained by triple quadrupole tandem MS. Ion trap MS was best suited for qualitative analysis and structure elucidation of branched isomeric structures of PFAS. Providing typical detection limits of 5 ng injected in MS2 mode, it was not sensitive enough for selective trace amount quantification. TOF high resolution MS was the only technique combining high selectivity and excellent sensitivity for PFAS analysis (detection limits of 2 to 10 pg), but lacked the possibility of MS-MS. Triple quadrupole tandem MS was the method of choice for quantification of FTOHs with detection limits in the low pg range. It is also well suited for the determination of PFAS, though its detection limits of 10 to 100 pg in tandem MS mode are about one order of magnitude higher than for TOF MS.

Application of high-performance liquid chromatography/electrospray mass spectrometry for the characterization of membrane lipids in the haloalkaliphilic archaebacteriumNatronobacterium magadii

The membrane lipid composition of Natronobacterium magadii, a species of haloalkaliphilic archaebacterium, has been studied by electrospray mass spectrometry (ES-MS), reversed phase high-performance liquid chromatography/electrospray mass spectrometry (LC/ES-MS), and tandem mass spectrometry. The negative-ion and positive-ion electrospray mass spectra and product ion mass spectra of the polar lipids are reported. LC/ES-MS of the total lipid extract in conjunction with product ion mass spectrometry established diphytanyl- and phytanyl, sesterterpanylglycerol-diether analogues of phosphatidylglycerolphosphate methyl ester as the major archaeols, with much lower levels of diphytanyl- and phytanyl, sesterterpanylglycerol-diether analogues of phosphatidylglycerol. In addition to these saturated, isopranyl archaeols, the presence of unsaturated archaeol analogues containing up to three double bonds was detected in Nb. magadii, representing the first description of isoprenyl ether lipids in a haloalkaliphilic archaebacterium. © 1998 John Wiley & Sons, Ltd.

Soil degradation of trifluralin: Mass spectrometry of products and potential products

The examination of soil which has been treated with trifluralin (TREFLAN alpha,alpha,alha-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) has resulted in the identification of 28 degradation products. This paper presents the mass spectra of these products and a number of related compounds which were suspected products but were not found in trifluralin-treated soil. The mass spectra of the N,N-dialkylamines, with one exception, show major peaks due to amine alpha-cleavage and due to amine alpha-cleavage followed by carbon-nitrogen bond fission with rearragement of a hydrogen atom. Compounds having nitro groups yield mass spectra containing peaks due to intra-ionic oxidation by the nitro groups. In some cases, propionyl ions formed by this process are major ions in the spectra. Azo and azoxybenzenes resulting from condensation of two trifluraline moieties through nitro-nitrogens fragment mainly through the nitrogen-nitrogen bond.