Triple-stage Quadrupole Mass Spectrometer Research Articles

Thermospray collisionally induced dissociation with single and multiple mass analyzers

A thermospray discharge ionization source has been used to obtain a collisionally induced dissociation (CID) spectrum of nabilone (MW 372) using a single stage quadrupole mass spectrometer. The resulting CID-mass spectrometry (MS) data show only a few structural features. Since most of the important fragments are above mass 200, it is difficult to assign structural identities to the primary daughter fragments or the nabilone molecule. Further information was obtained by using the thermospray discharge ionization source with a triple stage quadrupole mass spectrometer. Selected primary daughter ions were subjected to a second stage of CID fragmentation. Many of the resulting granddaughter ions are now in the mass range of 50–150 daltons and confident structure assignments can be made. The CID-MS—CID-MS data on nabilone showed the following features: a C 9 aliphatic chain with a branch giving a C 6 chain; losses of masses 58, 86, and 100 suggesting a ketonic structure that can break with up to 6 aliphatic carbons; losses of masses 60, 61, and 102 suggesting an ether or alcoholic oxygen; presence of one aromatic ring with one or two phenolic oxygens; low mass fragments of masses 55, 69, and 83 indicative of rings or unsaturation. It is audacious to suggest that the information given here is sufficient to write the full structure of nabilone. Nevertheless, the granddaughter fragment information permits a reasonable reconstruction of possible structures that could not be made with the first-order collisional fragmentation.

The effect of configuration of gas phase protonated ethenedicarboxylates on their low energy collision induced dissociation behaviour

AbstractLow energy collision induced dissociation (CID) spectra were measured by a triple stage quadrupole mass spectrometer for the [MH]+ ions of diethyl and dimethyl esters of maleic, fumaric, citraconic and mesaconic acids. A very high degree of stereospecificity was observed for the geometrically isomeric diethyl esters. The cis esters give rise to very abundant [MHEtOH]+ and [MHEtOHC2H4]+ ions, while the trans isomers exhibit very abundant [MHC2H4]+ and [MH2 C2H4]+ ions. The highly stereospecific processes indicate that the double bond configuration is retained in the protonated species under the conditions of the experiment.

MS/MS in pharmacokinetic studies

Two examples of quantitative drug concentration measurements in biological matrices are presented using (GC)-MS-MS techniques with a triple stage quadrupole mass spectrometer in the multiple reaction monitoring mode. Advantages over the well established GC/MS methods in respect to sensitivity and selectivity are demonstrated.

GC/MS/MS studies of unusual chemical ionization (CI) processes with a triple stage quadrupole (TSQ) mass spectrometer

For 2,2,6,6-tetramethylcyclohexanone (I), the CI(CH 4)-induced fragmentation of MH + into Me 2C=O N + H and [MH - H 2O] + ions is shown to proceed through common intermediates via two interconnected paths. Route A (ca. 75% of either fragment ion current/ involves sequential [1,2]-methyl migration, ring contraction and double [1.2]-methyl migration, route B (ca. 25%) may proceed via [1,2]-methyl migration, [1,21-hydroxyl migration, ring contraction and double [1,2]-methyl migration. A study of the effect of methyl substitution on the relative ease of these routes by GC/MS/MS analysis of mixtures of the lower methyl homologues of I sheds additional light on the mechanisms.

Studies of negative ions by collision-induced decomposition and hydrogen-deuterium exchange techniques.

Development of two new techniques for studying the gas phase chemistry of negative ions is reported. Collision induced dissociation (CID) of (M-1)- ions has been accomplished in a newly constructed triple stage quadrupole mass spectrometer. This instrument was assembled by adding two additional Finnigan quadrupole mass filters to a Finnigan Model 3200 CI mass spectrometer. Generation of (M-1)- ions is accomplished by allowing OH- and sample to react under CI conditions in the ion source. The first quadrupole mass filter, Q1, is then employed to selectively pass the (M-1)- ion into a second quadrupole filter containing argon or neon at 10(-3) torr. On collision with the inert gas the (M-1)- ions dissociate into fragments which are then mass analyzed in the third quadrupole filter, CID spectra of (M-1)- ions from twelve carbonyl compounds are presented in this paper. Ion molecule isotope exchange reactions in the CI ion source can be used to count the number of hydrogen atoms in many different chemical environments. Collisions between sample (M-1)- ions and deuterium-labeled reagent gases (ND3, D2O, EtOD) facilitate incorporation of deuterium into the negative ion if the basicities of the sample and reagent anions are similar. Thus it is possible to selectively incorporate deuterium into many organic samples by controlling the exothermicity of the acid base, ion-molecule chemistry.