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There is a general fascination with regard to the origin of life on Earth. There is an intriguing possibility that prebiotic precursors of life occurred in the interstellar space and were then transported to the early Earth by comets, asteroids and meteorites. It is probable that some part of the prebiotic molecules may have been generated by gas-phase ion/molecule reactions. Here we show experimentally that gaseous ion/molecule reactions of the amino acids, Glu and Met, may promote the synthesis of protonated dipeptides such as (Glu-Glu)H(+) and (Glu-Met)H(+) and their chemical growth to larger protonated peptides.

Hyperbranched polyesteramides (DA2), prepared from hexahydrophthalic anhydride (D) and diisopropanolamine (A) have been characterized, by use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), field desorption (FD)-MS, and electrospray ionization (ESI)-MS. MALDI of polyesteramides produces protonated molecules. The spectra show a complex chemical composition distribution and end-group distribution which are mainly composed of two series of homologous oligomers DnA(n)+1 - mH2O and DnA(n) - mH2O, where m = 1-2. Signals from protonated molecules DnAn+1 and DnAn are almost absent in the MALDI spectrum, whereas these ions are responsible for the base peak of DnA(n)+1 - mH2O and DnA(n) - mH2O (m = 1-2) clusters in the ESI spectrum. The absence of -OH end-groups signals in the MALDI spectrum is due to a metastable decay of protonated DnA(n)+1 and DnAn ions in the ion source of the MALDI mass spectrometer prior to ion extraction. In-source decay results in the formation of protonated lower DnA(n)+1 - mH2O and DnA(n) - mH2O oligomers and their corresponding neutrals, leading to wrong conclusions concerning the relative end-group distribution as a function of the degree of polymerization and the chemical composition.

It is shown using (high-resolution) mass spectrometry that treatment of 4,5-dihydrobenz[ l ]acephenanthrylene ( 2 , C 20 H 14 ) and S 8 in the melt gives the insoluble 532 a.m.u. (C 40 H 20 S) and 750 a.m.u. (C 60 H 30 ) bisbenz[ l ]acephenanthrothiophenes ( 4a–c ) and, trinaphtho[2,1- b ,2,1- m ,2,1- x ]- ( 3a ) and trinaphtho[2,1- b ,2,1- m ,1,2- a ′]decacyclene ( 3b ), respectively (estimated ratio 4a–c / 3a–b 20:1). Whereas 3a fits the `C 60 Schlegel diagram' and might be converted into C 60 (720 a.m.u.) after full cyclodehydrogenation, 3b can only give a curved C 60 H 12 /C 60 H 10 (732:730 a.m.u.). MALDI time-of-flight mass spectrometry shows that cyclodehydrogenations of 3a–b down to 732:730 a.m.u. occur; no evidence for C 60 formation was found. This is attributed to the preferred formation of 3b , the lack of cyclodehydrogenation selectivity and the occurrence of C 2 extrusions.

C70O dissolved in toluene transforms to as yet undetermined compounds when exposed to light at room temperature. After 140 days, only 21% of the original C70O remained. C70 was not formed. C139, or C140O were not found. One possible explanation is that the compounds formed were very insoluble in toluene and that their solids either remained in colloidal solution or attached themselves to the glass walls of the container bottles.

Triphenyltin compounds are widely introduced into the Dutch aquatic environment. To be able to detect them in environmental samples, the ionization methods of electron ionization, chemical ionization, fast atom bombardment, field desorption, thermospray and electrospray have been applied to triphenyltin acetate, chloride, fluoride and hydroxide to find out which of these methods is best suited to obtain molecular weight information on the intact molecules. For this purpose, field desorption is shown to be the most appropriate method giving, without fragmentation, molecular ion peaks, with the exception of triphenyltin hydroxide. The latter compound gives rise to the base peak at mz 716, due to the formation of bis(triphenyltin)oxide. Field desorption tandem mass spectrometry, applied to the molecular ions, has shown that the main decomposition pathway corresponds to the loss of a phenyl radical. Subsequently, sediment and surface water samples from the Dutch inland water, without and with the use of clean-up procedures, have been analyzed by the application of field desorption in combination with tandem mass spectrometry. Within the limits of detection, no signals for the presence of triphenyltin compounds in these environmental samples has been found. Upon spiking these samples with triphenyltin acetate, chloride, fluoride and hydroxide, it has appeared that the covalently bonded non-aromatic substituent of the molecules is exchanged for hydroxyl.

Some synthetically obtained linear and cyclic phosphopeptides of low molecular weight have been studied by fast-atom bombardment and tandem mass spectrometry to verify the position of the phosphate group in these compounds. Based upon the occurrence/non-occurrence of loss of phosphoric acid from low abundance fragment ions induced by low- and high-energy collisions with target gases, it is shown that the position of the phosphate group in the phosphopeptides studied can be determined unequivocally.

It is shown that metastably decomposing molecular ions of the title compounds eliminate sulfur dioxide via two reaction pathways provided that an α-hydrogen atom adjacent to the heterocyclic ring nitrogen atom is present. One of the channels leads to the initial formation of an o-azaxylylene ionic species and is associated with the narrow component of the accompanying composite metastable peak. The other channel involvel a multistep pathway which eventually leads to the formation of an aldimine ionic species and which is associated with the broad component of the accompanying composite metastable peak. Collision-induced dissociation and deuterium-labelling experiments have provided evidence that the initially generated o-azaxylylene ionic species, both as long-lived and as decomposing ions, have rearranged to the aldimine ionic species via a 1,5-shift of the α-hydrogen atom adjacent to the heterocyclic ring nitrogen atom.

Gas-phase reactions of MnO2− and MnO3− ions with a series of monofluoro- and pentafluoro-aromatic compounds, i.e. C6H4FX with X = o-, m- and p-CHO and o-, m- and p-OH and C6F5Y with Y = OH, OCH3, CHO, CN, NO2, COCH3 and F, were studied at low pressures by Fourier transform ion cyclotron resonance mass spectrometry. The principal reaction channels identified involve electron transfer from the MnO2− and MnO3− ions to the fluorinated aromatic substrates and proton abstraction and nucleophilic displacement of fluorine by these oxometallate ions. The results obtained indicate that in the gas phase MnO2− is less basic than MnO3− and that neutral MnO2 has a lower electron affinity than MnO3, both values lying between 0.52 and 0.94 eV.

Fourier transform ion cyclotron resonance and tandem mass spectrometry in combination with deuterium and 13 C-labelling have been applied to study the product C 3 H 4 N + ion from the gas phase reaction of the C 2 H 2 N + ion from CH 3 CN with its neutral precursor. This has provided evidence for associative cyclization of the cyanomethyl CH 2 CN + cation generated by electron bombardment of acetonitrile. The unimolecular dissociation of the metastably decomposing C 3 H 4 N + ion leads predominantly to HCNH + + C 2 H 2 . This reaction proceeds through a multistep pathway involving cyclic intermediates and is discussed in terms of structures and energies of the C 3 H 4 N + system. Collision-induced dissociation of the C 3 H 4 N + ions shows competitive fragmentations being higher energy demanding than that generating HCNH + + C 2 H 2 .

A continuous flow micro total analysis system (micro-TAS) consisting of an on-chip microfluidic device connected to a matrix assisted laser desorption ionization [MALDI] time-of-flight [TOF] mass spectrometer (MS) as an analytical screening system is presented. Reaction microchannels and inlet/outlet reservoirs were fabricated by powderblasting on glass wafers that were then bonded to silicon substrates. The novel lab-on-a-chip was realized by integrating the microdevice with a MALDI-TOFMS standard sample plate used as carrier to get the microfluidic device in the MALDI instrument. A novel pressure-driven pumping mechanism using the vacuum of the instrument as a driving force induces flow in the reaction microchannel in a self-activating way. Organic syntheses as well as biochemical reactions are carried out entirely inside the MALDI-MS ionization vacuum chamber and analyzed on-line by MALDI-TOFMS in real time. The effectiveness of the micro-TAS system has been successfully demonstrated with several examples of (bio)chemical reactions.

Trimethylsilylation of target substances in a mixture of N-methyl-N-trimethylsilyltrifluoroacetamide (MSTFA), ammonium iodide and ethanethiol is frequently applied for the application of gas chromatography–mass spectrometry (GC–MS) in steroid analysis. However, artifacts were formed when using this mixture to silylate the steroids androsterone and etiocholanolone obtained from a urine matrix. The artifacts were identified as ethyl thio-containing products of the respective trimethylsilyl derivatives. The conversion of the studied products increased slowly as a function of time, was dependent on the presence of the urine matrix and was significantly accelerated by adding diethyl disulfide to the reagent before incubation. Also ethyl thio-incorporation into testosterone and epitestosterone was established. A mechanism for ethyl thio-incorporation is proposed. The conversion achieved after 120-h sample storage at room temperature was insufficient to significantly influence the analysis of androsterone and etiocholanolone under the studied conditions. However, the results provide fundamental insight into the mechanism of silylation and the occurring side-reactions. Moreover, when investigating the formation of new metabolites, the ethyl thio-incorporation can lead to misinterpretation.

A combined chemical ionisation and tandem mass spectrometry (MS/MS) approach has been used for investigation of the gas-phase ion chemistry of systems containing the amino acids Glu and Met, and the dipeptides γ-Glu-Met and Met-Glu. The metastable fragmentation of the protonated dimer, (Glu)2H+, reveals an intracluster reaction leading to the elimination of the Glu residue. The main features of the ion-molecule reactions observed in the systems containing Glu and Glu + Met can be described in terms of sequential adduct formation. The results obtained for the thermal dehydration of Glu were used to rationalise the formation of the proton-bound structures (Glu − H2O)···H+··· (Glu − H2O) and (Glu − H2O)3·H+. The adduct ions, [(Glu − H2O) + H + Glu]+ and [(Glu − H2O) + H + Met]+, and further association products were also observed. The results lead to a reconsideration of the structural aspects proposed earlier for these species in the sense that they suggest that the systems correspond to a mixture of isomeric covalent and proton-bound structures. The thermal effects on the decomposition of the neutral (γ-Glu-Met) and its protonated form, (γ-Glu-Met)H+, at m/z 279 were investigated, and dramatic changes in the MI spectra of the m/z 279 ion with temperature were found. A mechanistic explanation for the observed evolution of higher mass ion peaks in the mass spectra is developed. Copyright © 2001 John Wiley & Sons, Ltd.

The possibility of creating a robust mass spectral library with use of high-performance liquid chromatography-atmospheric pressure-electrospray ionization (HPLC-AP-ESI) for the identification of drugs misused in cases of clinical toxicology has been examined. Factors reported as influencing the fragmentation induced by "source transport region collision induced dissociation" (CID) have been tested in this study (i.e. solvent, pH, different acids or buffer salts and their concentration, different organic modifiers and the modifier concentration). The tests performed on a few "model drugs" were analysed with use of two different single quadrupole instruments. The large number of mass spectra obtained appears to be affected by the mobile phase conditions to only a minor extent. This also holds for the mass spectra obtained at two different instruments (laboratories). Subsequently breakdown curves have been measured for about 20 randomly chosen drugs by variation of the kinetic energy of their ions in the CID zone through changing the fragmenter voltage. These breakdown curves were used to optimize the fragmenter voltage for each drug. The optimized fragmenter voltages were then applied by use of a variably ramped fragmenter voltage to acquire mass spectra for the library. The chromatographic separations were run on a Zorbax Stable bond column using a 10-mM ammonium formate-acetonitrile gradient method. Spiked blank serum and patient samples with a total of 40 different drugs were extracted with use of a standard basic liquid-liquid extraction (LLE) method. A search of significant peaks in the chromatogram by application of the developed mass spectral library is shown to result in a more than 95% positive identification. reserved.

The application of the “Lab-on-a-Chip” concept to synthetic chemistry [1, 2] is still at its infancy. In this work a borofloat microchip (Fig. 1) was designed and fabricated by means of the powderblasting technique and used as chemical microreactor in which different solution-phase syntheses have been performed successfully. The stream flowing from the outlet of the chip has been transferred directly onto a gold-coated sample plate. The chemical reaction products were analysed using matrix assisted laser desorption ionization [MALDI] - time-of-flight [TOF] mass spectrometry [3]. MALDI-TOF mass spectrometry in combination with post source decay [PSD] experiments shows to be an excellent method in obtaining molecular weights and structural information. The Schiff base reaction, in which primary amines react with aldehydes to give imines, was chosen as a primary study, because the Schiff base reaction is straightforward and products are obtained in high yields. Lab-scale experiments are carried out under acidic conditions (pH = 3–4), however, pH control is not necessary under the “Labon-a-Chip” conditions. Open image in new window Figure 1 Schematic representation of the chip used in this work and of the MALDI sample plate on which the stream flowing from the chip is analysed.

Results of gas-phase reactions of MnO and MnO ions with a series of aliphatic C1C4 alcohols show that C2C4 primary alcohols are oxidized by MnO in reaction channels which involve proton abstraction and hydride-ion transfer, along with the appearance of [H.Mn.O.OH]− ions. Secondary alcohols are oxidized in slower processes while menthanol and t-butanol are unreactive. MnO/alcohol reactions are more complex and involve the formation of [H.MnO3]−, [H.Mn.O2.OH]−, [RO.Mn.O.OH]−, [(RO)2 Mn.O]− and the terminal solvated ion [(RO)3.Mn.OH]−.

Fullerene contents of chlorinated C60 and C70 were determined with HPLC. n-Values of C60Cln and C70Cln were determined from mass increase during synthesis, MALDI-TOF mass spectrometry, PIXE, Nuclear Microprobe (12C[d,p]13C), and Electron Microprobe analysis. n-Values obtained immediately after synthesis were in the range 31-45. Best values obtained later were in the range 10-20. It is suggested that (i) the samples lost CS2 or CS2/CCl4, or Cl of “crystallization” after synthesis, (ii) after synthesis the samples lost Cl bound to C60 (iii) Cl was lost during the analysis, or (iv) some of all three.

In negative ion field desorption mass spectrometry (M - H) − ions are generated from non-acidic compounds such as saccharides and nucleosides. These ions are not “preformed” in a sample solution but are generated by ion molecule reactions in the space charge region of the negatively charged sample layer. The chemistry of the ionization by proton abstraction is investigated and discussed.

It is shown that the γ- or 1,5-hydrogen shift in the molecular ion of 1-nitropropane leads to three primary fragmentation reactions. They are the loss of a hydroxyl radical, a molecule of ethylene and a molecule of nitric oxide. The structures and chemistry of the resulting ions have been investigated by a series of experiments including deuterium labelling, spontaneous and collisionally induced dissociations and accurate mass measurements.

The deuterium and 13 C-labeling study of metastable and collisionally induced decompositions of gaseous protonated (deuterated) acetonitrile, generated in a chemical ionization source by proton (deuteron) transfer to CX 3 CH (X = H or D) using different reagent gases, reveals two distinct mechanisms for fragmentation of (CX 3 CH)X + . The metastable reactions of (CX 3 CN)X + formed from X + 3 /CX 3 CN occur mainly via the multistep pathway involving isomerization into the nitrilium ion reacting configuration, (X 3 C ⋯ NCX) + , presumably through cyclic configuration(s), while the collisionally induced dissociations proceed directly, i.e., from ion structures which have retained the CCN skeleton. The latter decompositions are similar to both the metastable and collisionally induced decompositions of (CX 3 CN)X + generated from other systems studied. The results obtained indicate that these two pathways are associated with the source of creation of their precursor ions, (CX 3 CN)X + , and are operative independently of each other. This study underlines the important role of the source of energy deposition in the parent ion. The rearrangement of (CX 3 CN)X + is discussed on the basis of structures and energies of the C 2 H 4 N + system.

Field desorption of negative ions can be achieved below the threshold of field electron emission. To this end a mixture of the sample with polyethylene oxide and water was applied to smooth wire cathodes. The mass spectra of some inorganic and organic compounds are reported. Anionization by [CI]− ion attachment is demonstrated with the examples of 20-hydroxycholesterol and sucrose.

It is demonstrated that each of the molecular ions of cyclopropylbenzene and di- n -propyl sulphide, having the same nominal mass m/z 118 and generated from a nearly 1:1 mixture by 70 eV electron impact in a Fourier transform ion cyclotron resonance mass spectrometer, can be selectively isolated in the cell by ejection of all other ions from the cell. This corresponds to a so-called front-end resolution of primary ion selection for MS/MS experiments in excess of 35 000 at m/z 118. Subsequent collisionally induced dissociation (CID) experiments on each of the mass-selected molecular ions have been performed using helium, introduced via a pulsed valve, as collision gas. A so-called back-end resolution of 205 000–475 000 has been obtained for the CID product ions over the mass range m/z 61–117, while the accuracy of the mass measurements on the corresponding ions is shown to be better than 1 ppm.

The site of protonation of gaseous benzonitrile in reactions with H+3, CH3OH+2, and CH3CNH+ as protonating agents has been examined by using tandem mass spectrometry in combination with deuterium and 13C labeling. Metastable and collision-induced dissociation studies of C6X5CNX+ (X = H or D) show that proton attachment occurs on the CN group. The metastably decomposing C6X5CNX+ leads only to C6X5+ + XCN. This reaction proceeds via a mechanism involving H+ (D+) transfer from the CN group to the phenyl ring in which H/D exchange occurs. The efficiency of the CN-to-ring H+ (D+) transfer increases in the order para < meta < ortho position. Evidence for incomplete H/D atom randomization in C6X5CNX+ prior to XCN loss has been obtained. Both processes, CN-to-ring H/D exchange and H/D exchange at the phenyl ring, are affected by the internal energy of the C6X5CNX+ ions. The results have been interpreted in terms of the internal energy distribution of the ions fragmenting within the metastable time window. Collision-induced dissociation of C6X5CNX+ causes the energy-enriched ions to decompose by direct bond cleavage into C6X+5 + XCN.

Negative ion field desorption mass spectrometry has been applied to detergents containing anionic surfactants. The mass spectra demonstrate a high selectivity for the detection of the sulphonates (concentration limit 10−5 mol/l). The spectra do not contain fragment ions nor ionization products from non-ionic components of the mixture.

The anionization of molecules supplied from the gas phase onto a negatively charged [Cl]− or [NO3]− ion donating surface has been investigated. The charged surface was prepared by exposing an aqueous solution of LiCl (or LiNO3) and polyethylene oxide to a high external field as is done in negative ion field desorption mass spectrometry. The ionization of some monosaccharides and adenosine by [Cl]− and [NO3]− attachment and of some acids by proton abstraction is reported.

The dimer formed in the gas-phase reaction of ionized di-isopropyl sulphide with its neutral analogue is shown to possess a strong sulphur–sulphur bond.

Four beta-endorphins (beta-endorphin 6-17, 2-17, 1-16, and 1-17) and two adrenocorticotropic hormone (ACTH) peptides (ACTH 1-10 and (1-16)-NH2) were studied by using fast atom bombardment coupled with tandem mass spectrometry. The capability to reproduce metastable ion and collisionally activated decomposition spectra on two different commercial sector mass spectrometers in two different laboratories was found to be acceptable (deviations in relative abundance are less than +/- 50%). The endorphin peptides fragment metastably or upon collisional activation to give abundant B-series ions as well as Y-series ions, whereas Y-series ions are the principal ionic species produced upon the desorption by fast atom bombardment. The ACTH peptides also fragment to give Y-series ions, but of relatively low abundance compared to those from the endorphins. For both sets of peptides, high-energy collisionally activated decomposition and metastable ion decomposition daughter ion spectra are precise, structurally informative--even for peptides up to m/z 2000--and complementary to spectra of daughter ions produced by desorption ionization alone.