A novel technique for real time mass spectrometric analysis of bioorganic samples at atmospheric pressure without any pretreatment based on laser ablation of the sample and ionization of the vapor plume by laser plasma radiation was developed. The potential of the method was showcased in drug screening, mass spectrometric imaging of biological tissues, tissue type and oncologic decease presence identification

The results of comparative analysis of laser desorption/ionization, matrix-assisted laser desorption/ ionization, and new laser-induced electron transfer desorption/ionization methods, used to detect chlorophyll A; mercury complex with thiuram; platinum complex with mercaptoquinoline; and lutetium complex with phthalocyanine, modified by crown ether, are presented. The new method is found to have a better ionization efficiency for complex compounds than the conventional laser desorption/ionization methods.

Continuous wave (CW) CO 2 lasers have been in common medicine use for over 40 years. Tissue dissection using CW lasers is accompanied by high heating of adjacent tissue. This effect is highly useful during the soft tissue surgery due to its ability to prevent bleeding. However, there exist problems that require tissue removal without adjacent layers heating. For example: scar removal from skin surface, microbial films removal from surfaces of ENT organs in otolaryngology, ablation of biological tissues for mass spectrometric analysis and so on. In these cases pulsed laser radiation is needed because pulse duration narrowing dramatically decreases the heat transfer out of the irradiated region during ablation of tissue.

General theoretical approaches to the modelling of Coulomb effects in short ion bunches, developed previously by the authors, are applied in this paper to the calculation of multireflection mass-spectrometer systems. A separate module of the MASIM 3D applied software package is designed. An adaptive computational procedure for calculating the ‘mirror potential’ induced by an ion bunch on the surface of field-forming electrodes is proposed. The dynamics of ion bunches in a time-of-flight reflectron-type mass analyser is calculated and the limitations on the resolving power, caused by resonant Coulomb effects of self-bunching and coalescence in the groups of particles with close masses, are revealed on the basis of numerical experiments.

Three new approaches to the laser mass spectrometry of organic samples are presented, which are based on the soft ionization of organic and bioorganic molecules and on the use of pulsed laser radiation.

The paper presents main peculiarities of implementation and testing of an algorithm based on the variational approach to the problem of simulating the stationary distributions of ions in the radiofrequency, low-vacuum ion traps with taking into consideration the Coulomb interaction and interaction with buffer gas. A good agreement between the results of numerical modeling and analytical results obtained earlier by other authors for simpler models is attained. The employment of the software that has been developed in the course of this work enables studying the structure of ion ensembles in the radiofrequency ion traps of different types and obtaining the results being of interest for high-resolution mass spectrometry. The algorithm allows a natural generalization to three-dimensional case.

The atmospheric pressure mass spectrometric detection efficiency of organic species (tofisopam and verapamil) was measured by means of the laser ablation of dried solution drops containing known amount of the analyte. Ablated molecules were ionized by an atmospheric pressure laser plasma cell and then introduced in the TOF mass-spectrometer. The spot was formed by dripping 2 mu l of solution on the stainless steel substrate and consequent drying. Then it was scanned by an intense ablating beam of various lasers (CO2, Nd:YAG and femtosecond fiber laser) until the spot was completely eroded during the non-stop MS-analysis of ablated material. The sensitivity was defined as the ratio of the total ion current integral of the relevant mass peaks to the amount of molecules in the spot. All the tested lasers are suitable for the ablation and subsequent MS-detection of organic species in dried solution spots given enough power deposition is provided. The measured sensitivity values reach 0.1 ions/fg of tested analytes.

The mechanism of ion desorption in the process of laser desorption/ionization from silicon surfaces is studied using pyridine and N,N-dimethyl-1-phenylethylamine as examples. Based on the experimental and theoretical results, dependences of ion signal on the surface temperature are obtained for two different wavelengths of laser radiation, 355 nm and 532 nm. The theoretical part of the work includes numerical calculations of surface temperatures of amorphous silicon using the SLIM software package and quantum-chemical calculations of binding energy between the ions and silicon surface using the Hartree-Fock method and Firefly software package. It is demonstrated that the ions are desorbed via a thermal mechanism at temperatures much lower than the melting point of amorphous silicon.

The efficiency of laser desorption/ionization of twenty compounds from the surface of amorphous silicon is studied as a function of proton affinity (PA) and gas-phase basicity (GB). The values of GB and PA are obtained from quantum-chemical calculations using the density functional theory in the B3LYP model with the 6–311++G(3df,3pd) basis set. The values of GB lie in the range from 845 to 977 kJ/mol. The efficiency of laser desorption/ionization exponentially depends on the GB and PA values and for the studied compounds varies from 7 × 10−6 to 1.4 × 10−2.

Comparison of the efficiency of the laser ablation of biological tissue with the use of a repetitively pulsed CO2-laser with transverse discharge and a continuous CO2-laser with modulated output radiation is carried out. It is shown that the ablation efficiency is higher for the repetitively pulsed laser with a pulse duration of 20 .s and a pulse power of more than 2 kW, and the radiation from the cw laser with the power of 50 W and pulse duration of 500 .s results in much greater thermal damage to the tissue surrounding the impact zone. The first clinical application of the repetitively pulsed CO2-laser in dermatology and plastic reconstructive and restorative surgery has shown its clinical and aesthetic performance and identified key long-term direction of its further use for surgery.

Ablyation of biofabric the radiation of CO2 of the laser now the most effective and perspective physical mechanism for elimination of pathological changes, including cicatricial deformation, integuments. In experimental work of in vivo on integuments of mini-pigs of Svetlogorsk population on the basis of the analysis of comparative histologic research it was defined that efficiency and a pretsizionnost of an ablyation is much higher for pulse and periodic CO2 of the laser lasting impulse of 20 microsec and capacity in an impulse more than 2 kW, the maximum preservation of viability of fabrics on the periphery and progressive dynamics of regeneration of ablative wounds, and radiation of continuous CO2 of the laser with a power of 50 W and lasting impulse of 500 microsec is thus provided and even 200 microsec cause bigger thermal damage of the fabrics surrounding a zone of influence is considerable. Thus, this experimental work at fabric level confirmed uniqueness and efficiency of a laser ablyation of integuments with the radiation of pulse and periodic CO2 of the laser lasting impulse of 20 microsec and prospect of application of a laser dermabraziya realized by it in clinical practice for elimination of pathological changes of integuments, including cicatricial deformation.

A new method was developed for the mass spectrometric analysis of organic and bioorganic compounds, which involves laser ablation with the ionisation of its products by laser-plasma radiation and enables analysing gaseous, liquid, and solid substances at atmospheric pressure without sample preparation. The capabilities of this method were demonstrated by the examples of fast pharmaceutical composition screening, real-time atmosphere composition analysis, and construction of the mass spectrometric images of organic compound distributions in biological materials.

A novel approach to the rapid screening of pharmaceutical drugs by surface assisted laser desorption-ionization (SALDI) mass spectrometry with the rotating ball interface coupled with temperature programmed thermal desorption has been developed. Analytes were thermally desorbed and deposited onto the surface of amorphous silicon substrate attached to the rotating ball. The ball was rotated and the deposited analytes were analyzed using SALDI. The effectiveness of coupling SALDI mass spectrometry with thermal desorption was evaluated by the direct and rapid analysis of tablets containing lidocaine, diphenhydramine and propranolol without any sample pretreatment. The overall duration of the screening procedure was 30÷40 sec. Real urine samples were studied for drug analysis. It is shown that with simple preparation steps, urine samples can be quantitatively analyzed using the proposed technique with the detection limits in the range of 0.2÷0.5 ng/ml.

The role of laser irradiation in the processes of laser desorption/ionisation from silicon surfaces is considered. The basic functions of laser irradiation (chemical activation of the ion emitter surface, laser-induced ionisation of chemical compounds and ion desorption) are established and analysed.

A new method has been developed for the mass spectrometric determination of phenylalkylamines based on surface-assisted laser desorption/ionization (SALDI). Films of amorphous α-Si, obtained by radiofrequency sputtering have been tested as ion emitters. The high efficiency of the ionization method combined with gas chromatography and the time-of-flight mass spectrometry has been demonstrated. The main analytical parameters have been determined for 12 phenylalkylamines. The detection limit for the studied compounds has been found to vary in the range 5–150 pg/mL.

A rotating ball interface for surface-assisted laser desorption/ionization (SALDI) mass spectrometry was designed and tested. One side of the ball was exposed to atmospheric pressure and the other to the vacuum in a time-of-flight mass spectrometer. Analytes (arginine, atenolol, reserpine, tofisopam, and chloropyramine) were applied using electrospray to a silicon substrate on the atmospheric side, the ball was rotated 180 degrees, and the analyte was desorbed on the vacuum side using a pulsed, 200 Hz, 355nm laser. In order to increase the desorption area, the laser focus was scanned over the substrate in a raster pattern repeated once every second. The design allows for rapid sample throughout with a sample turn-around time as short as 5s. Newly produced porous silicon substrates initially yielded very low ion signals, and they required several hundred laser shots to attain maximum sensitivity. In contrast, amorphous silicon did not require such 'activation'. Quantitative analysis showed a sample-to-sample reproducibility of about 10%. The sensitivities with model analytes were in the 1000 to 10 000 ions/fmole range and detection limits in the low fg range. Copyright (C) 2010 John Wiley & Sons, Ltd.

The generation of ions from silicon substrates in surface-assisted laser desorption ionization (SALDI) has been studied using silicon substrates prepared and etched by a variety of different methods. The different substrates were compared with respect to their ability to generate peptide mass spectra using standard liquid sample deposition. The desorption/ionization processes were studied using gas-phase analyte deposition. Mass spectra were obtained from compounds with gas-phase basicities above 850kJ∕mol and with molecular weights up to 370Da. UV, VIS, and IR lasers were used for desorption. Ionization efficiencies were measured as a function of laser fluence and accumulated laser irradiance dose. Solvent vapors were added to the ion source and shown to result in fundamental laser-induced chemical and physical changes to the substrate surfaces. It is demonstrated that both the chemical properties of the substrate surface and the presence of a highly disordered structure with a high concentration of “dangling bonds” or deep gap states are required for efficient ion generation. In particular, amorphous silicon is shown to be an excellent SALDI substrate with ionization efficiencies as high as 1%, while hydrogen-passivated amorphous silicon is SALDI inactive. Based on the results, a novel model for SALDI ion generation is proposed with the following reaction steps: (1) the adsorption of neutral analyte molecules on the SALDI surface with formation of a hydrogen bond to surface Si–OH groups, (2) the electronic excitation of the substrate to form free electron/hole pairs (their relaxation results in trapped positive charges in near-surface deep gap states, causing an increase in the acidity of the Si–OH groups and proton transfer to the analyte molecules), and (3) the thermally activated dissociation of the analyte ions from the surface via a “loose” transition state.

A variety of amphetamine-like compounds were analyzed by gas chromatography/surface-assisted laser desorption ionization mass spectrometry, GC/SALDI-MS. In the SALDI method, compounds are adsorbed on a solid SALDI substrate and directly ionized from the substrate by means of a laser pulse. The interfacing of a SALDI ion source with a gas chromatograph is presented here for the first time. The end of the GC column is situated 20 mm from the silicon substrate in the vacuum of the ion source of a time-of-flight mass spectrometer, and the compounds eluted from the GC capillary are adsorbed onto the nanostructured silicon surface. The mass spectra show very low levels of background noise and no reagent ions. GC/SALDI-MS detection limits are several orders of magnitude lower than those previously reported for GC/MS analysis of amphetamine-like compounds. The extent of fragmentation is under experimental control by changing the laser fluence.

The spectral and energy characteristics of the excitation and dissociation of SF, molecules in a two-frequency infrared laser field are investigated. The quantum efficiency of two-frequency dissociation is found to depend on the frequency of the second field and on the excitation level in the first. The linear-absorption spectra of SF, molecules excited by a laser field are obtained. The parameters of these spectra differ significantly from the thermal ones.