V. T. Kogan

A portable mass spectrometer for direct monitoring of gases and volatile compounds in air and water samples

A portable automated mass-spectrometric system allows direct testing of gases and volatile substances in both air and water samples in in situ and on-line modes and is intended for studies in ecology, oceanology, and for testing technological processes. The parameters, the instrument design and operating modes, and the units included in it are described. The choice of the design of the membrane input system, which ensures low threshold levels of detecting goal compounds (down to a few ppb for toluene and benzene) and the dependence of this choice on the measurement mode and the state and composition of the investigated sample are considered. The results of tests of the mass-spectrometer in the mode of direct selective and total inspection are presented.

The Ion-optical scheme of a portable mass spectrometer

An ion-optical scheme for a portable magnetic double-focusing mass spectrometer that makes it possible to analyze several components simultaneously over a wide mass range (the mass-spectrograph operating mode) is proposed. This scheme effectively solves the research and technological problems involving the analysis of rapidly varying compositions.

Small-size mass spectrometer for determining gases and volatile compounds in air during breathing

We describe an automated mass spectrometer for diagnostics of deceases from the composition of exhaled air. It includes a capillary system, which performs a rapid direct feeding of the sample to the instrument without changing substantially its composition and serves for studying the dynamics of variation of the ratio between various components of exhaled air. The membrane system for introducing the sample is intended for determining low concentrations of volatile organic compounds which are biomarkers of pathologies. It is characterized by selective transmittance and ensures the detection limits of target compounds at the parts per million–parts per billion (ppm–ppb) level. A static mass analyzer operating on permanent magnets possesses advantages important for mobile devices as compared to its dynamic analogs: it is more reliable in operation, has a larger dynamic range, and can be used for determining the concentration of components in the mixture one-by-one or simultaneously. The curvilinear output boundary of the magnetic lens of the mass analyzer makes it possible to reduce its weight and size by 2.5 times without deteriorating the mass resolution. We report on the results of testing of the instrument and consider the possibility of its application for early detection of deceases of respiratory and blood circulation system, gastrointestinal tract, and endocrine system.

Ion-Optical Scheme for a Portable High-Sensitivity Mass Spectrograph

An ion-optical scheme that allows for a considerable improvement of the sensitivity and speed of a mass spectrograph is suggested. These ends are accomplished by appropriately choosing the parameters of an electrostatic capacitor and the shape and location of a magnetic lens, as well as by using an original multichannel linear sectional detector. The numerical simulation of the detector is carried out. It is shown that rapid analysis of multicomponent mixtures in a wide mass range, along with a substantial extension of the dynamic range of a signal recorded, is a possibility. The basic parameters of a mass analyzer based on the scheme suggested are verified experimentally, and the results obtained are discussed.

A membrane inlet system equipped with a piezoelectric lock for introduction of gaseous samples into a mass-spectrometer

The design of a membrane inlet system, which is equipped with a metal-sealed piezoelectric vacuum lock, for introducing samples into a mass spectrometer, is described. The membrane interface is characterized by a selective permeability for volatile target compounds and allows their detection in air with a high sensitivity in a proximate measurement mode using automated portable or mobile mass spectrometers. The system provides short instrument response times (∼1 s) owing to the use of a thin membrane material (tens of microns) and excludes hazardous consequences of a possible destruction of the membrane. The inlet system is controlled via application of voltage to the lock, thus enabling blocking of the gas flow that is supplied to the instrument within several hundredth parts of a second. Testing results are presented.

A Membrane Inlet for a Portable Mass Spectrometer

A system of membrane injection of a sample into a portable mass spectrometer which is used for determining the concentration of organic components in complex mixtures is described. Spectra of samples containing alkanes from methane to hexane have been measured. The data obtained using the membrane and diaphragm inlets to are compared. The potentialities of membrane inlets for portable mass spectrometers intended for environmental and process monitoring are shown.

Direct mass-spectrometric measurement of methane and its volatile homologues in water

The direct quantitative measurement of the concentration of water-dissolved saturated hydrocarbons using a portable membrane-inlet precalibrated magnetic mass-spectrometer is suggested. The particularity of the instrument’s response to the presence of desired compounds in a test sample is taken into consideration. The feasibility of using this portable instrument in real-time oil and gas search on the continental shelf is discussed. Laboratory test data for the methane, ethane, propane, and butane concentrations in air and water samples are presented, from which the sensitivity of the instruments to the components, are determined. The gas concentrations in the water samples lie in the range from several parts per billion (ppb) to several hundred ppb. These values are close to the lower limits of prospecting criteria as applied to oil fields.

Repeatability of breath acetone concentration during stress testing

The aim of the study was to evaluate the repeatability of the human breath acetone concentration during stress testing. Eight healthy men aged 19 to 34 years were tested (mean age 26.9 ± 1.4). Subjects performed a stress testing on cycle ergometer at twice-weekly intervals. As a result of processing the obtained data, a good similarity between the initial and repeated curves of the acetone concentration was found. In addition, a good repeatability of some parameters was revealed, which show the peculiarities of the change in acetone concentration in healthy individuals. The results obtained in this work can be useful in the creation of diagnostic methods that use the acetone concentration in the exhaled air.

Electronic and software systems of an automated portable static mass spectrometer

The electronic systems of a small high-sensitivity static mass spectrometer and software and hardware tools, which allow one to determine trace concentrations of gases and volatile compounds in air and water samples in real time, have been characterized. These systems and tools have been used to set up the device, control the process of measurement, synchronize this process with accompanying measurements, maintain reliable operation of the device, process the obtained results automatically, and visualize and store them. The developed software and hardware tools allow one to conduct continuous measurements for up to 100 h and provide an opportunity for personnel with no special training to perform maintenance on the device. The test results showed that mobile mass spectrometers for geophysical and medical research, which were fitted with these systems, had a determination limit for target compounds as low as several ppb(m) and a mass resolving power (depending on the current task) as high as 250.

Analysis of changes in the human exhale acetone concentration during stress testing

The aim of the study was to analyze the changes in the human breath acetone concentration during stress testing. Using the portable mass spectrometer we obtained recordings of acetone concentration during stress testing on bicycle ergometer for groups of healthy subjects, athletes and patients with congestive heart failure (CHF). As a result, we found significant differences (p <; 0.05) of some parameters of acetone concentration that differ significantly between healthy subjects and patients with CHF. In addition, a parameter that allows classifying patients with CHF into subgroups based on the functional class of CHF was obtained. The results obtained in this study may be useful for the objectification of the functional status of patients with CHF.