Ambient ion soft landing.

Ambient ion soft landing, a process in which polyatomic ions are deposited from air onto a surface at a specified location under atmospheric pressure, is described. Ions generated by electrospray ionization are passed pneumatically through a heated metal drying tube, their ion polarity is selected using ion deflectors, and the dry selected ions are soft-landed onto a selected surface. Unlike the corresponding vacuum soft-landing experiment, where ions are mass-selected and soft-landed within a mass spectrometer, here the ions to be deposited are selected through the choice of a compound that gives predominantly one ionic species upon ambient ionization; no mass analysis is performed during the soft landing experiment.

Sampling wand for an ion trap mass spectrometer.

A new sampling wand concept for ion trap mass spectrometers equipped with discontinuous atmospheric pressure interfaces (DAPI) has been implemented. The ion trap/DAPI combination facilitates the operation of miniature mass spectrometers equipped with ambient ionization sources. However, in the new implementation, instead of transferring ions pneumatically from a distant source, the mass analyzer and DAPI are separated from the main body of the mass spectrometer and installed at the end of a 1.

Paper spray ionization of polar analytes using non-polar solvents.

Non-polar solvents like hexane allow ionization of insoluble drugs, peptides, nucleotides and phospholipids as solids from paper. Ambient ionization is achieved simply by application of a high voltage to the wet paper. Transport and ionization mechanisms are discussed, including the possibility of field desorption from dendritic structures formed on the paper.

Multivariate statistical identification of human bladder carcinomas using ambient ionization imaging mass spectrometry.

Diagnosis of human bladder cancer in untreated tissue sections is achieved by using imaging data from desorption electrospray ionization mass spectrometry (DESI-MS) combined with multivariate statistical analysis. We use the distinctive DESI-MS glycerophospholipid (GP) mass spectral profiles to visually characterize and formally classify twenty pairs (40 tissue samples) of human cancerous and adjacent normal bladder tissue samples. The individual ion images derived from the acquired profiles correlate with standard histological hematoxylin and eosin (H&E)-stained serial sections.

Direct analysis of biological tissue by paper spray mass spectrometry.

Paper spray mass spectrometry (PS-MS) is explored as a fast and convenient way for direct analysis of molecules in tissues with minimum sample pretreatment. This technique allows direct detection of different types of compounds such as hormones, lipids, and therapeutic drugs in short total analysis times (less than 1 min) using a small volume of tissue sample (typically 1 mm(3) or less). The tissue sample could be obtained by needle aspiration biopsy, by punch biopsy, or by rubbing a thin tissue section across the paper.

Detection of explosives and related compounds by low-temperature plasma ambient ionization mass spectrometry.

Detection of explosives is important for public safety. A recently developed low-temperature plasma (LTP) probe for desorption and ionization of samples in the ambient environment ( Anal. Chem.

Perspectives in imaging using mass spectrometry.

Imaging mass spectrometry (MS) allows a remarkable range of measurements including diagnosis of disease state of tissue based on detailed information on its chemical constituents, especially lipids and proteins. The recent emergence of ambient ionization allows imaging in the open environment without sample preparation. In this review, we briefly describe the history of imaging MS highlighting its main techniques and applications.

Mapping lipid alterations in traumatically injured rat spinal cord by desorption electrospray ionization imaging mass spectrometry.

Desorption electrospray ionization (DESI) mass spectrometry (MS) is used in an imaging mode to interrogate the lipid profiles of 15 μm thin tissue cross sections of injured rat spinal cord and normal healthy tissue. Increased relative intensities of fatty acids, diacylglycerols, and lysolipids (between +120% and +240%) as well as a small decrease in intensities of lipids (-30%) were visualized in the lesion epicenter and adjacent areas after spinal cord injury. This indicates the hydrolysis of lipids during the demyelination process due to activation of phospholipase A(2) enzyme.

Origin of chiral selectivity in gas-phase serine tetramers.

Serine "magic-number" clusters have attracted substantial experimental and theoretical interest since their discovery. Serine undergoes marked chiral enrichment upon sublimation, which has been associated with the homochiral selectivity of the octamer. This process has been implicated in one possible mechanism leading to the origin of biological homochirality.

Redox chemistry in thin layers of organometallic complexes prepared using ion soft landing.

Soft landing (SL) of mass-selected ions is used to transfer catalytically-active metal complexes complete with organic ligands from the gas phase onto an inert surface. This is part of an effort to prepare materials with defined active sites and thus achieve molecular design of surfaces in a highly controlled way. Solution-phase electrochemical studies have shown that V(IV)O(salen) reacts in the presence of acid to form V(V)O(salen)(+) and the deoxygenated V(III)(salen)(+) complex-a key intermediate in the four electron reduction of O(2) by vanadium-salen.

Enhanced detection of olefins using ambient ionization mass spectrometry: Ag+ adducts of biologically relevant alkenes.

Spray solvent doped with silver ions increases the ease of olefin detection by desorption electrospray ionization (DESI). Characteristic silver adducts were generated in up to 50 times greater abundance when compared to conventional DESI spray solvents for the biologically significant olefin, arachidonic acid, in the positive ion mode. In the analysis of 26 lipids, silver adduct formation was highly favorable for fatty acids, fatty acid esters and prostaglandins but not applicable to some other classes (e.

Ion/molecule reactions for detecting ammonia using miniature cylindrical ion trap mass spectrometers.

Gaseous ammonia, a common toxic industrial compound, is not detected readily in ion trap mass spectrometers because its molecular ion falls below the low-mass cutoff (~m/z 40) normally used when examining organic compounds. Instead, reactions of ammonia with halobenzene radical cations were used with internal electron ionization in two cylindrical ion trap miniature mass spectrometers to create a characteristic product ion by which to identify and quantify ammonia. Ammonia showed a linear response over the concentration range studied (parts per million [ppm] to parts per billion [ppb]) with limits of detection of 17 ppm and 220 ppb for experiments involving direct introduction and thermal desorption after pre-concentration, respectively.

Multivariate statistical differentiation of renal cell carcinomas based on lipidomic analysis by ambient ionization imaging mass spectrometry.

Desorption electrospray ionization (DESI) mass spectrometry (MS) was used in an imaging mode to interrogate the lipid profiles of thin tissue sections of 11 sample pairs of human papillary renal cell carcinoma (RCC) and adjacent normal tissue and nine sample pairs of clear cell RCC and adjacent normal tissue. DESI-MS images showing the spatial distributions of particular glycerophospholipids (GPs) and free fatty acids in the negative ion mode were compared to serial tissue sections stained with hematoxylin and eosin (H&E). Increased absolute intensities as well as changes in relative abundance were seen for particular compounds in the tumor regions of the samples.

Imaging of human lens lipids by desorption electrospray ionization mass spectrometry.

The lipid composition of the human lens is distinct from most other tissues in that it is high in dihydrosphingomyelin and the most abundant glycerophospholipids in the lens are unusual 1-O-alkyl-ether linked phosphatidylethanolamines and phosphatidylserines. In this study, desorption electrospray ionization (DESI) mass spectrometry-imaging was used to determine the distribution of these lipids in the human lens along with other lipids including, ceramides, ceramide-1-phosphates, and lyso 1-O-alkyl ethers. To achieve this, 25 μm lens slices were mounted onto glass slides and analyzed using a linear ion-trap mass spectrometer equipped with a custom-built, 2-D automated DESI source.

Miniature mass spectrometers.

We discuss miniaturization in mass spectrometry in terms of the mass analyzer, the mass spectrometer, and the total analytical system. Mass analyzer miniaturization has focused on ion traps. Decreases in mass analyzer size facilitate reduction of the sizes of the other components of a miniature mass spectrometer, especially the radio frequency electronics and vacuum system.

Evaluation of a differential mobility spectrometer/miniature mass spectrometer system.

A planar differential mobility spectrometer (DMS) was coupled to a Mini 10 handheld rectilinear ion trap (RIT) mass spectrometer (MS) (total weight 10 kg), and the performance of the instrument was evaluated using illicit drug analysis. Coupling of DMS (which requires a continuous flow of drift gas) with a miniature MS (which operates best using sample introduction via a discontinuous atmospheric pressure interface, DAPI), was achieved with auxiliary pumping using a 5 L/min miniature diaphragm sample pump placed between the two devices. On-line ion mobility filtering showed to be advantageous in reducing the background chemical noise in the analysis of the psychotropic drug diazepam in urine using nanoelectrospray ionization.

Instantaneous chemical profiles of banknotes by ambient mass spectrometry.

Using two desorption/ionization techniques (DESI and EASI) and Brazilian real, US$ dollar, and euro bills as proof-of-principle techniques and samples, direct analysis by ambient mass spectrometry is shown to function as an instantaneous, reproducible, and non-destructive method for chemical analysis of banknotes. Characteristic chemical profiles were observed for the authentic bills and for the counterfeit bills made using different printing processes (inkjet, laserjet, phaser and off-set printers). Detection of real-world counterfeit bills and identification of the counterfeiting method has also been demonstrated.

Trace detection of non-uniformly distributed analytes on surfaces using mass transfer and large-area desorption electrospray ionization (DESI) mass spectrometry.

Ambient ionization methods such as desorption electrospray ionization (DESI) allow the analysis of chemicals adsorbed at surfaces without the need for sample (or surface) pretreatment. A limitation of current implementations of these ionization sources is the small size of the area that can be sampled. This makes examination of surfaces of large areas time-consuming because of the need to raster across the surface.

Perspectives and retrospectives in mass spectrometry: one view.

Mass spectrometry benefits from a flexible definition which equates it with many aspects of the science of matter in the ionized state. The field continues to expand rapidly, not only to encompass larger and more complex molecules through more powerful instruments, but simultaneously towards in-situ measurements made using smaller, more flexible and just-sufficiently-powerful instruments. The senior author has been fortunate to work in mass spectrometry from 1967 to the present and has been involved in a wide range of efforts which have covered analytical, biological, organic, instrumental and physical aspects of the subject.

Detection of explosives as negative ions directly from surfaces using a miniature mass spectrometer.

A miniature mass spectrometer was modified by incorporating a conversion dynode detector system and the appropriate electronics to allow the detection of negatively charged ions. The system was fitted with a discontinuous atmospheric pressure interface to allow external ionization by desorption electrospray ionization (DESI). It was used to identify the explosives 2,4,6-trinitrotoluene (TNT), 2,4,6-trinitrophenyl-N-methylnitramine (Tetryl), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) present in trace amounts on surfaces (500 pg/cm(2) to 1 microg/cm(2)) both individually and as components of mixtures.

Enhanced ion signals in desorption electrospray ionization using surfactant spray solutions.

Solvent optimization is an important procedure in desorption electrospray ionization (DESI) and in this study the effects of solvent surface tension are explored. Data are presented for methanol/water/surfactant solvent systems, which show increases in ion signals of more than an order of magnitude when low concentrations of surfactants are added to the standard methanol/water (1:1) spray solvent. Examples of analytes tested include food chemicals, peptides, pharmaceuticals, and drugs of abuse.

Desorption electrospray ionization imaging mass spectrometry of lipids in rat spinal cord.

Imaging mass spectrometry allows for the direct investigation of tissue samples to identify specific biological compounds and determine their spatial distributions. Desorption electrospray ionization (DESI) mass spectrometry has been used for the imaging and analysis of rat spinal cord cross sections. Glycerophospholipids and sphingolipids, as well as fatty acids, were detected in both the negative and positive ion modes and identified through tandem mass spectrometry (MS/MS) product ion scans using collision-induced dissociation and accurate mass measurements.

Facility monitoring of toxic industrial compounds in air using an automated, fieldable, miniature mass spectrometer.

Gaseous samples of nine toxic industrial compounds (acrolein, acrylonitrile, carbon disulfide, cyanogen chloride, ethylene oxide, formaldehyde, hydrogen cyanide, phosgene, and sulfur dioxide) were detected, identified, and quantitated using a fully automated, fieldable, miniature mass spectrometer equipped with a glow discharge electron ionization source and a cylindrical ion trap mass analyzer. The instrument was outfitted with a combined direct air leak and dual thermal desorption tube inlet that allowed for continuous sampling of compounds with throughput times of 2 min or less. Most compounds showed a linear response over the concentration ranges studied (sub-parts per billion [ppb] to parts per million [ppm]).