Concluding remarks

1979 ◽  
Vol 293 (1400) ◽  
pp. 167-168
Keyword(s):  
Mass Spectrometry ◽  
High Pressure ◽  
Mass Spectrometer ◽  
Organic Molecules ◽  
Negative Ions ◽  
Negative Ion ◽  
Current Status ◽  
Source Analysis ◽  
Biological Chemistry ◽  
Mass Spectrometers

It is good that from time to time, a group of leading workers in a field should come together to discuss the current status of their research, and the direction in which it will most probably develop. We should all be grateful to the Royal Society in acting as hosts to this conference and to Professor Johnson and Professor Beynon for organizing it. I think that all will agree that the high quality of the papers presented have made this occasion a very memorable and valuable one. I should also like to thank the organizers for the relaxed atmosphere of the Conference, which made it so enjoyable. The last decade has seen a tremendous growth in both the instrumentation and techniques of mass spectrometry and the applications of mass spectrometry to organic and biological chemistry. On the instrumentation side, the modification of a double focusing mass spectrometer to yield ion kinetic energy spectra, giving information about the progenitors of a given ion, and the reversed geometry instrument, yielding information as to the daughter ions of a given parent, have both considerably contributed to our knowledge of the fragmentation of organic molecules. Again the development of special sources, field ionization and field desorption, the linking of a gas or high pressure liquid chromatograph to a mass spectrometer, and the introduction of high pressure sources for chemical ionization, have all made important contributions to organic and biological chemistry. The study of negative ions has also shed considerable light on the structure of organic molecules. Finally, the linking of computers with mass spectrometers has enabled results to be obtained very much more rapidly than in the past, and also made possible library searches to identify the substances present. Mr Craig discussed recent modifications in the source, analysis systems and detector systems of commercial mass spectrometers. Of particular importance was the increased sensitivity obtained by more effective ion collection. Among the newer techniques described during the meeting were g.c.-m.s. (Professor Jellum, Professor Jackson, Dr Morris, Professor Brooks and Professor Eglinton), collisional activation (Professor McLafferty and Dr Morris), negative ion mass spectrometry (Professor Jennings) and reversed geometry mass spectrometry (Professor Beynon).

scholarly journals 662. Identification of Clinically Relevant Microbes with the MasSpec Pen

2020 ◽  
Vol 7 (Supplement_1) ◽  
pp. S386-S387
Author(s):  
Sydney C Povilaitis ◽  
Ashish D Chakraborty ◽  
Rachel D Downey ◽  
Sarmistha Bhaduri Hauger ◽  
Livia Eberlin
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectrometer ◽  
Model Performance ◽  
Sample Surface ◽  
Clinical Analysis ◽  
Ambient Ionization ◽  
Rapid Identification ◽  
Negative Ion ◽  
Ionization Mass ◽  
Molecular Features

Abstract Background In the age of antimicrobial resistance, rapid identification of infectious agents is critical for antimicrobial stewardship and effective therapy. To this end, ambient ionization mass spectrometry techniques have been applied for rapid identification of microbes directly from culture isolates. We have developed a handheld, mass spectrometry-based device, the MasSpec Pen, that permits direct molecular analysis of a biological sample in seconds (Scheme 1). Here, we employ the MasSpec Pen to identify clinically relevant microbes directly from culture isolates. Methods Staphylococcus aureus, Staphylococcus epidermidis, Group A and B Streptococcus, Kingella kingae (K.k), and Pseudomonas aeruginosa (P.a) were cultured on 5% sheep’s blood nutrient agar at 37 °C overnight. Colonies were transferred to a glass slide where they were analyzed directly with the MasSpec Pen coupled to a Q Exactive mass spectrometer (Thermo Scientific) in negative ion mode. For MasSpec Pen analysis, a 10 µL droplet of water was held in contact with the sample surface for 3 seconds and then aspirated to the mass spectrometer for analysis. Data was normalized and the molecular features resulting from the analysis solvent and nutrient medium were removed. The least absolute shrinkage and selection operator (lasso) statistical method was used to build classification models for prediction of bacterial identity. Model performance was evaluated by leave-one-out cross-validation and a validation set of samples. Scheme 1: MasSpec Pen workflow Results Various small molecules were detected including metabolites and glycerophospholipid species. The mass spectral profiles for each species exhibited qualitative differences among them (Figure 1). Additionally, several quorum-sensing molecules were observed in P.a. including hydroxy-heptyl-quinoline (m/z 242.155). Lasso statistical classifiers were created to differentiate organisms at the level of Gram type, genus, and species with each model comprised of a sparse set of molecular features. Accuracies of 90% or greater were achieved for all lasso models and as high as 98% for the differentiation of Staphylococcus (Staph.) and Streptococcus (Strep.). Figure 1: Molecular profiles of species analyzed Figure 2: Statistical classification results Conclusion These results demonstrate the potential of the MasSpec Pen as a tool for clinical analysis of infected biospecimens. Disclosures Sydney C. Povilaitis, BA, MS Pen Technologies, Inc. (Other Financial or Material Support, Patent) Livia Eberlin, PhD, MS Pen Technolpogies, Inc. (Board Member, Shareholder)

The formation of (CH3)7Si2+ in (CH3)4Si/CH4 mixtures and CH3− exchange reactions between (CH3)4Si, (CH3)4Ge, and (CH3)4Sn studied by high pressure mass spectrometry

1987 ◽  
Vol 65 (12) ◽  
pp. 2849-2854 ◽  
Author(s):  
Anastasia C. M. Wojtyniak ◽  
Xiaoping Li ◽  
John A. Stone
Keyword(s):  
Mass Spectrometry ◽  
High Pressure ◽  
Equilibrium Constant ◽  
Mass Spectrometer ◽  
Excellent Agreement ◽  
Ion Source ◽  
Methyl Groups ◽  
Exchange Reactions ◽  
Equilibrium Reactions ◽  
Association Equilibrium

The association equilibrium [Formula: see text] has been studied in a high pressure mass spectrometer ion source using tetramethylsilane/methane mixtures. Measurement of the equilibrium constant over a range of temperatures yields ΔH0 = −22.3 ± 0.4 kcal mol−1 and ΔS0 = −35.2 ± 0.9 cal mol−1 K−1. Collision-assisted dissociation experiments suggest that the methyl groups retain their integrity in (CH3)7Si2+. Mixed ions such as (CH3)7SiGe+ and (CH3)7GeSn+ were not observed in mixtures of (CH3)4X and (CH3)4Y(X ≠ Y = Si, Ge, Sn). Instead CH3− transfer equilibrium reactions were observed viz. [Formula: see text] (ΔH0 = −10.2 ± 1.2 kcal mol−1, ΔS0 = −3.7 ± 2.4 cal K−1 mol−1) and [Formula: see text], ΔS0 = −0.9 ± 1.6 cal K−1 mol−1. These are in excellent agreement with some published differences in appearance potentials for (CH3)3X+ from (CH3)4X (X = Si, Ge, Sn).

Negative Ion Mass Spectra of Some Pesticidal Compounds

1971 ◽  
Vol 54 (6) ◽  
pp. 1340-1348 ◽  
Author(s):  
Peter C Rankin
Keyword(s):  
Organic Chemistry ◽  
Structural Analysis ◽  
Characteristic Feature ◽  
Mass Spectra ◽  
Organic Molecules ◽  
Negative Ions ◽  
Negative Ion ◽  
Carbamate Pesticides ◽  
Complex Organic

Abstract A study of the negative ion mass spectra of a number of complex organic molecules (pesticides) was undertaken to determine what information this technique would yield for structural analysis. The simplicity of the negative ion mass spectra was a characteristic feature and the most abundant negative ions in the spectra were assumed to be similar to the stable carbanions postulated in classical organic chemistry. The simplicity of the mass spectra suggested a possible application of the technique to the identification of carbamate pesticides.

scholarly journals A novel rocket borne ion mass spectrometer with large mass range: instrument description and first flight results

2020 ◽  
Author(s):  
Joan Stude ◽  
Heinfried Aufmhoff ◽  
Hans Schlager ◽  
Markus Rapp ◽  
Frank Arnold ◽  
...  
Keyword(s):  
Mass Spectrometer ◽  
Negative Ions ◽  
Mass Range ◽  
Large Mass ◽  
Molecular Ions ◽  
Negative Ion ◽  
Cluster Ions ◽  
The Arctic ◽  
Atmospheric Species ◽  
Smoke Particles

Abstract. We present a novel rocket borne ion mass spectrometer ROMARA (ROcket borne MAss spectrometer for Research in the Atmosphere) for measurements of atmospheric positive and negative ions (atomic, molecular and cluster ions) and positively and negatively charged meteor smoke particles. Our ROMARA instrument has, compared to previous rocket borne ion mass spectrometers, a markedly larger mass range of up to m/z 2000 and a larger sensitivity, particularly for meteor smoke particle detection. Mayor objectives of this first ROMARA flight included: a functional test of the ROMARA instrument, measurements between 55 km and 121 km in the mass range of atmospheric positive and negative ions, a first attempt to conduct mass spectrometric measurements in the mass range of meteor smoke particles with mass to charge ratios up to m/z 2000, and measurements inside a polar mesospheric winter echo layer as detected by ground based radar. Our ROMARA measurements took place on the Arctic island of Andøya/Norway around noon in April 2018 and represented an integral part of the PMWE rocket campaign. During the rocket flight, ROMARA was operated in a measurement mode, offering maximum sensitivity and the ability to qualitatively detect total ion signatures even beyond its mass resolving mass range. On this first ROMARA flight we were able to meet all of our objectives. We detected atmospheric species including positive atomic, molecular and cluster ions along with negative molecular ions up to about m/z 100. Above m/z 2000, ROMARA measured strong negative ion signatures, which are likely due to negatively charged meteor smoke particles.

scholarly journals A field-deployable, chemical ionization time-of-flight mass spectrometer

2011 ◽  
Vol 4 (7) ◽  
pp. 1471-1479 ◽  
Author(s):  
T. H. Bertram ◽  
J. R. Kimmel ◽  
T. A. Crisp ◽  
O. S. Ryder ◽  
R. L. N. Yatavelli ◽  
...  
Keyword(s):  
High Pressure ◽  
Formic Acid ◽  
Mass Spectrometer ◽  
Chemical Ionization ◽  
Time Of Flight ◽  
High Sensitivity ◽  
Negative Ion ◽  
Efficient Production ◽  
Ionization Time ◽  
Flight Mass Spectrometer

Abstract. We constructed a new chemical ionization time-of-flight mass spectrometer (CI-TOFMS) that measures atmospheric trace gases in real time with high sensitivity. We apply the technique to the measurement of formic acid via negative-ion proton transfer, using acetate as the reagent ion. A novel high pressure interface, incorporating two RF-only quadrupoles is used to efficiently focus ions through four stages of differential pumping before analysis with a compact TOFMS. The high ion-duty cycle (>20 %) of the TOFMS combined with the efficient production and transmission of ions in the high pressure interface results in a highly sensitive (>300 ions s−1 pptv−1 formic acid) instrument capable of measuring and saving complete mass spectra at rates faster than 10 Hz. We demonstrate the efficient transfer and detection of both bare ions and ion-molecule clusters, and characterize the instrument during field measurements aboard the R/V Atlantis as part of the CalNex campaign during the spring of 2010. The in-field short-term precision is better than 5 % at 1 pptv (pL/L), for 1-s averages. The detection limit (3 σ, 1-s averages) of the current version of the CI-TOFMS, as applied to the in situ detection of formic acid, is limited by the magnitude and variability in the background determination and was determined to be 4 pptv. Application of the CI-TOFMS to the detection of other inorganic and organic acids, as well as the use of different reagent ion molecules (e.g. I−, CF3O−, CO3−) is promising, as we have demonstrated efficient transmission and detection of both bare ions and their associated ion-molecule clusters.

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