Helium Carrier Gas Research Articles

Development and validation of GLC/FID- and GLC/MS-procedures of secnidazole determination by the methods of additions

Gas-liquid chromatography is widely used in the process of forensic toxicological examinations, but data about application of GLC with flame-ionization and mass-spectrometry detection for secnidazole determination in analytical toxicology are absent.Aim. To develop GLC/FID- and GLC/MS-procedures for the quantitative determination of secnidazole and carry out step-by-step validation of the procedures developed in the variant of the method of additions.Results and discussion. The chromatographic conditions has been chosen for secnidazole determination by the method of GLC in two variants of performance with flame-ionization and mass-spectrometry detection with the temperature program changing during the analysis from 70 °C to 250 °C or 320 °C. Retention times for secnidazole are 8.97 min and 11.74 min. To prove the possibility of application of the procedures proposed in further analysis their validation has been carried out in the variant of the method of additions. Such validation parameters as in-process stability, linearity, accuracy and precision have been estimated by model solutions.Experimental part. The GLC/FID-analysis: HP 6890 Hewlett Packard; НР-1 o0.32 mm × 30 m, 0.25 μm; thermostat – 70 oС (3 min), 40 oС/min to 180 oС (2 min), 40 oС/min to 250 oС (3 min); injector – 280 oС; detector – 280 oС; volume rate of a carrier gas (helium) – 1.5 ml/min; split mode – 1 : 2. The GLC/MS-analysis: Agilent 6890N/5973N/7683; НР-5MS o0.25 mm × 30 m, 0.25 μm; DB-17MS o0.25 mm × 30 m, 0.15 μm; columns are connected sequentially through Deans switch; thermostat – 70 oС (2 min), 45 oС/min. to 210 oС, 6 oС/min to 320 oС (12.56 min); transfer line – 280 oС; ion source – 230 oС; quadrupole – 150 oС; electron impact – 70eV; 40-750 m/z; injector – 250 oС; splitless mode; inlet carrier gas (helium) pressure: 1st column – 26.06 psi, 2nd column – 19.30 psi.Conclusions. New procedures for the quantitative determination of secnidazole by the method of GLC/FID and GLC/MS have been developed. Their validation has been carried out, and acceptability for application has been shown.

Effect of cold plasma on storage toxigenic fungi - Aspergillus flavus : Poster

Cold plasma is a novel non-thermal food processing technology that uses energetic, reactive gases to inactivate contaminating microorganisms such as fungi and bacteria. This flexible sanitizing method uses electricity and a carrier gas (air, oxygen, nitrogen, or helium) antimicrobial chemical agents are not required. The primary modes of action are due to UV light and reactive chemical products of the cold plasma ionization process. Aspergillus flavus is the predominant species responsible for fungal contamination and subsequent production of aflatoxins mainly in grains during postharvest operations and storage. Due to their relatively high contamination risk, decontamination methods for fungi are of great interest for economic and environmental reasons, as well as in public health. Improved post-harvest processing followed by further prevention of fungal growth is an effective way to restrict aflatoxin contamination and would have major impact on reducing health related risks and on production economics. Thus, the objective is to evaluate the inactivation of A. flavus by cold plasma. The experiment was conducted with 3 mm sample A. flavus in PDA culture medium. Plasma was applied at different durations (2, 5, 10, 12, 15 and 20 min). After application, the Petri dishes with treated samples were stored at 25°C for 6 days. There was fungal growth after 2 days in the treatments with2 and 5 min durations, 4 days with the treatments with 10 and 12 min durations and there was no fungal growth with the treatments of 15 and 20 min after 6 days. The durationof 15 and 20 min with the plasma parameters tested, were efficient for the inactivation of A. flavus. Cold plasma may be a promising green method to be applied in this microorganisms present in grains and other products during storage.

A Validated GC-MS Method for the Determination of Genotoxic Impurities in Divalproex Sodium Drug Substance.

A specific GC-MS method has been developed, optimized and validated for the determination of five genotoxic impurities namely Methyl bromide (Me.-Br), Ethyl bromide (Et.-Br), Isopropyl bromide (Ipr.-Br), n-Propyl bromide (n-Pr.-Br) and n-Butyl bromide (n-But.-Br) in Divalproex sodium (DPS) drug substance. Chromatographic separation of five genotoxic impurities was achieved on DB-1 column (30 m × 0.32 mm, 3.0 μm), consists of 100% dimethyl polysiloxane as stationary phase and passing helium carrier gas. The mass fragments (m/z) were selected for the quantification of Me.-Br (m/z 94), Et.-Br (m/z 108), Ipr.-Br (m/z 122), n-Pr.-Br (m/z 122) and n-But.-Br (m/z 136). Bromide ion (m/z 79) was the qualifier ion for the analytes [(Me.-Br), (Et.-Br), (Ipr.-Br), (n-Pr.-Br) and (n-But.-Br)]. The performance of the method was assessed by evaluating the specificity, linearity, sensitivity, precision and accuracy experiments. The established limit of detection and limit of quantification values for the genotoxic impurities were in the range of 0.005-0.019 μg mL-1. The correlation coefficient values of the linearity experiment were in the range of 0.9947-0.9983. The average recoveries for the accuracy were in the range of 97.6-111.3%. The results proved that the method is suitable for the determination of Me.-Br, Et.-Br, Ipr.-Br, n-Pr.-Br and n-But.-Br contents in divalproex sodium.

Spectroscopic identification of jet-cooled o-ethynylbenzyl radical generated in corona discharge

The vibronically excited but jet-cooled o-ethynylbenzyl radical was generated from precursor, o-ethynyltoluene seeded in a large amount of carrier gas helium using a home-made pinhole-type glass nozzle combined with the technique of corona excited supersonic expansion. The visible vibronic emission spectrum was recorded with a long-path monochromator from the corona discharge of the precursor. By analyzing the observed spectrum, we determined the electronic energy in the D1 → D0 transition and vibrational mode frequencies in the D0 electronic state of the o-ethynylbenzyl radical.

Issues with analyzing noble gases using gas chromatography with thermal conductivity detection.

The noble gases, namely neon, argon, krypton and xenon, have many uses including in incandescent and gas discharge lighting, in plasma televisions, shielding gas in welding, in lasers for surgery and semiconductors, and in magnetic resonance imaging (MRI) of the lungs. When incorporating these noble gases in industries, especially the medical field, it is important to know accurately the composition of the noble gas mixture. Therefore, there is a need for accurate gas standards that can be used to determine the noble gas amount-of-substance fraction in the appropriate mixture application. A recent comparison of mixtures containing four noble gases in a helium balance showed mixed results among National Metrology Institutes. Significant differences, 0.7 to 3.8% relative, were seen in the analytical amount-of-substance assignments versus the gravimetric value of the noble gases in the comparison mixture when using "binary standards", i.e. neon in helium, argon in helium and krypton in helium, as applied by the National Institute of Standards and Technology. Post-comparison studies showed that when all four noble gases were included in the standards, the agreement between analytical and gravimetric values was within 0.05% relative. Further research revealed that different carrier gases (hydrogen, helium and nitrogen) resulted in varying differences between the analytical and gravimetric values assignments. This paper will discuss the findings of these analytical comparisons. Graphical abstract ᅟ.

Abstract 4390: Developing methods for investigating cold atmospheric plasma effects on cervical cancer

Abstract Cold atmospheric plasma (CAP) has been suggested for use as a novel cancer therapeutic due to its reported ability to induce cell-specific death. Cervical cancer is the fourth most common cancer in women. Its prevalence and accessibility for topical treatment make cervical cancer an ideal target for CAP treatments. Despite its potential impact, effects of CAP in biological systems are not well understood. To better understand the viability of CAP as a therapy, this project investigated in vitro cellular responses induced by CAP treatment within cancerous cervical cells (SiHa) and non-cancerous cervical (Ect1/E6E7 and End1/E6E7) and vaginal cells (VK2/E6E7). Plasma is a state of ionized gas, produced using a controlled electric field or extreme heat. CAP, however, is a subset of plasma that is produced near 1 atm and 40oC. This allows for CAP treatment of biological systems without heating-induced effects. A dielectric barrier discharge plasma pen was developed for this study. Plasma modeling was conducted in order to predict the reactive species present in the system. CAP treatments were performed on cells for 30 seconds using a helium carrier gas at a flowrate of 1 L/min and a DC power supply with input settings of 10kV, 1µs, and 0.1A. Cell vitality assays demonstrated induced cell death following exposure to CAP treatment in both cancerous and noncancerous cervical cells as indicated by flow cytometric analysis and florescence microscopy. CAP treatment induced cell death in 76 ± 8% of treated cancerous, SiHa, cells. In comparison, noncancerous cell lines Ect1/E6E7, End1/E6E7, and VK2/E6E7 underwent 49 ± 8%, 42 ± 13%, and 51 ± 7% cell death, respectively. Flow cytometry characterization and wound healing assays indicate that CAP treatment does not significantly affect the expression of investigated cell surface adhesion molecules or cell migration. Cells were treated with helium carrier gas as the negative control and hydrogen peroxide as an induced death control. Altered levels and locations of uptake of FITC and quantum dots following CAP treatment suggest modification of cell membranes as compared to carrier gas treatment controls. Adjustments in membrane permeability may be a mechanism through which CAP treatment increases exposure to apoptotic triggers. In conclusion, comprehensive understanding of CAP effects on cancerous and non-cancerous cells could lead to the development of effective CAP-based therapies for cervical cancer. Citation Format: Nicole J. Sova, Yonry Zhu, Quinn O. Mitchell, Ariel L. Lanier, David Burnette, Monica M. Burdick. Developing methods for investigating cold atmospheric plasma effects on cervical cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4390.

Precision analysis of multisulfur isotopes in sulfides by femtosecond laser ablation GC-IRMS at high spatial resolution

A new laser ablation method has been developed for measurements of multiple sulfur isotopes in sulfides using a femtosecond laser ablation system in combination with a reactor for sulfide aerosol conversion into SF6 gas, a cryogenic and chromatographic purification system, and an isotope ratio mass spectrometer (FsLA-GC-IRMS). In this method, femtosecond laser-generated aerosol sulfide particles were transferred by the helium carrier gas from the sample chamber into the reactor to convert them to SF6via reaction with BrF5. Cryogenically and chromatographically purified SF6 was transferred by helium carrier gas to the interface that was developed for introducing SF6 into the ion source of a mass spectrometer running in high-vacuum operation mode. For the routine analysis of sulfide, a precision of 0.1–0.2‰ (1σ) for δ34S and higher than 0.03‰ (1 σ) for ∆33S values has been obtained with an ablation crater size of 80 μm diameter and 40 μm depth. The method was tested using reference materials IAEA-S-1, IAEA-S-2, IAEA-S-3 and NBS-123, as well as some natural pyrite, sphalerite and galena samples. The δ34S values obtained by our method are in good agreement (within analytical precision) with the results obtained by the conventional dual inlet method. The FsLA-CG-IRMS method was applied to study sulfur isotope ratios in Archean rocks of the Cheremshanskaya formation (Sharyzhalgai uplift in the southeastern Siberian craton). We found that ∆33S values in sulfides from these rocks ranged +2.30 to +2.68‰. The reliability of the results obtained here was confirmed by comparative analyses of isotope ratios in sulfides from rocks younger than 2.4 Ga in which the anomaly of the 33S isotope could be unlikely to occur. The calculated δ34S’ = ln(δ34S/1000 + 1)*1000 and δ33S’ = ln(δ33S/1000 + 1)*1000 values of this set of samples yielded a straight line passing through the origin with a slope of 0.5152 (±0.002) on a conventional sulfur three-isotope plot that is in good agreement with a slope of 0.515, which was theoretically calculated for the mass-dependent fractionation of sulfur isotopes.

INVESTIGATION OF COMPONENTS OF HEXANE EXTRACT FROM TAMARIX HISPIDA BY METHOD OF GAS CHROMATOGRAPHY

In this article, we determined the qualitative and quantitative component composition of the hexane extract, derived from plant material - the aerial part of the Tamarix hispida genus, the Tamarix family of Tamaricaceae, which grows in the southern region of the Republic of Kazakhstan (Almaty region). For this purpose, the previously dried and ground plant material (500 g) was extracted with hexane into the feed-reagent ratio (1:10) in a Soxhlet apparatus. The extract was concentrated under mild conditions (water bath temperature 40-45 °C) using a water-jet pump vacuum to concentrate. Analysis of the component composition of the hexane extract carried out using gas chromatography with a mass-selective detector under the following conditions: capillary column SHP-5MS used carrier gas helium with a flow rate of 1 ml / min at a temperature gradient from 40 °C to 250 °C and the injector volume - 0.2 μl. The materials were identified by mass spectra and retention times using the Wiley GC/MS library. The percentage of the components was calculated automatically from the areas of the peaks of the general chromatogram of the ions. As a result, 30 components were identified, of which 8 were acids and their esters, 5-alcohols, 4-ketones, 1-aldehyde, 1-phenol, 3-alkane, 3 halogen derivatives, 2-cyclic, 3-heterocyclic compounds. A significant content of β-carotene (23.73%), 2-cis-9-octadecinyl octaethanol (16.99%), propyl 3-octadecyloxyoleic acid (14.34%), octacosyltrifluoroacetate (8.60%), cis-11-octadecenoic acid (7.49%), heptacosan (6.01%), 2-bromocataladecan (5.24%), β-sitosterol (4.49%), respectively. Halogen-containing biologically active compounds were found for the first time in Tamarix genus. In addition, some amount of the nitrogen-containing compounds has been identified, which also were not previously found in lipophilic extracts of Tamarix.Forcitation:Ikhsanov Y.S., Abilov Z.A., Sultanova N.A., Choudhary M.I. Investigation of components of hexane extract from tamarix hispida by method of gas chromatography. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 6. P. 83-87

Water nucleation in helium, methane, and argon: A molecular dynamics study.

Nucleation of highly supersaturated water vapor in helium, methane, and argon carrier gases at 350 K was investigated using molecular dynamics simulations. Nucleation rates obtained from the mean first passage time (MFPT) method are typically one order of magnitude lower than those from the Yasuoka and Matsumoto method, which can be attributed to the overestimation of the critical cluster size in the MFPT method. It was found that faster nucleation will occur in carrier gases that have better thermalization properties such that latent heat is removed more efficiently. These thermalization properties are shown to be strongly dependent on the molecular mass and Lennard-Jones (LJ) parameters. By varying the molecular mass, for unaltered LJ parameters, it was found that a heavier carrier gas removes less heat although it has a higher collision rate with water than a lighter carrier. Thus, it was shown that a clear distinction between water vapor-carrier gas collisions and water cluster-carrier gas collisions is indispensable for understanding the effect of collision rates on thermalization. It was also found that higher concentration of carrier gas leads to higher nucleation rate. The nucleation rates increased by a factor of 1.3 for a doubled concentration and by almost a factor of two for a tripled concentration.

The stable oxygen isotope ratio of resin extractable phosphate derived from fresh cattle faeces.

RationalePhosphorus losses from agriculture pose an environmental threat to watercourses. A new approach using the stable oxygen isotope ratio of oxygen in phosphate (δ18OPO4 value) may help elucidate some phosphorus sources and cycling. Accurately determined and isotopically distinct source values are essential for this process. The δ18OPO4 values of animal wastes have, up to now, received little attention.MethodsPhosphate (PO4) was extracted from cattle faeces using anion resins and the contribution of microbial PO4 was assessed. The δ18OPO4 value of the extracted PO4 was measured by precipitating silver phosphate and subsequent analysis on a thermal conversion elemental analyser at 1400°C, with the resultant carbon monoxide being mixed with a helium carrier gas passed through a gas chromatography (GC) column into a mass spectrometer. Faecal water oxygen isotope ratios (δ18OH2O values) were determined on a dual‐inlet mass spectrometer through a process of headspace carbon dioxide equilibration with water samples.ResultsMicrobiological results indicated that much of the extracted PO4 was not derived directly from the gut fauna lysed during the extraction of PO4 from the faeces. Assuming that the faecal δ18OH2O values represented cattle body water, the predicted pyrophosphatase equilibrium δ18OPO4 (Eδ18OPO4) values ranged between +17.9 and +19.9‰, while using groundwater δ18OH2O values gave a range of +13.1 to +14.0‰. The faecal δ18OPO4 values ranged between +13.2 and +15.3‰.ConclusionsThe fresh faecal δ18OPO4 values were equivalent to those reported elsewhere for agricultural animal slurry. However, they were different from the Eδ18OPO4 value calculated from the faecal δ18OH2O value. Our results indicate that slurry PO4 is, in the main, derived from animal faeces although an explanation for the observed value range could not be determined.

The influence of carrier gas on plasma properties and hydrogen peroxide production in a nanosecond pulsed plasma discharge generated in a water-film plasma reactor

The influence of carrier gas (argon and helium) on the properties of a nanosecond pulsed filamentary discharge propagating along the water surface in a water film plasma reactor, and the effects of plasma properties on the formation of hydrogen peroxide (H2O2) are investigated. The plasma properties, including electron density, gas temperature, and plasma volume, and the hydrogen peroxide production rate and energy yield were measured and compared in both argon and helium discharges. The results show that helium plasma is more diffusive compared with the argon plasma, and it has lower electron density and gas temperature but larger volume. The production rates and energy yields of hydrogen peroxide are only slightly higher in the helium plasma although the electron density is much lower. A simple mathematical model with time-dependent fast radical and electron quenching in a small film surrounding the plasma core and with lumped reaction kinetics for H2O2 formation and degradation suggests that the hydroxyl radical (·OH) concentration is approximately two times higher in the argon discharge, but the larger volume of the helium leads to about two times more total ·OH in the helium with correspondingly higher energy yields. The experimental data and model imply that the H2O2 energy yield may increase at lower power (or specific energy density) for both carrier gases.

Femtosecond X-ray diffraction from an aerosolized beam of protein nanocrystals.

High-resolution Bragg diffraction from aerosolized single granulovirus nanocrystals using an X-ray free-electron laser is demonstrated. The outer dimensions of the in-vacuum aerosol injector components are identical to conventional liquid-microjet nozzles used in serial diffraction experiments, which allows the injector to be utilized with standard mountings. As compared with liquid-jet injection, the X-ray scattering background is reduced by several orders of magnitude by the use of helium carrier gas rather than liquid. Such reduction is required for diffraction measurements of small macromolecular nanocrystals and single particles. High particle speeds are achieved, making the approach suitable for use at upcoming high-repetition-rate facilities.

Phenomenology of Corona Discharge in Helium Admixtures Inside a Point-to-Point Electrode Geometry

Experimental investigations of the electrical discharge characteristics were performed primarily for helium admixtures in a point-to-point electrode geometry. The atmos- pheric pressure weakly ionized plasmas were generated using 60-Hz ac excitation voltage that generated a corona discharge without dielectric barriers on the electrodes. The admixtures used were helium/acetylene (He/C2H2), helium/oxygen (He/O2), and helium/dry-air (He/air) with comparisons made to corona discharges in an admixture argon/dry-air (Ar/air). Visual observations along with voltage–current characteristics have been presented. The discharge included streamers, glows, and return corona discharges inside the point-to-point high voltage gap. We developed from experimental data corona mode maps to delineate optimal regions for plasma operation in these admixtures. Helium carrier gas developed sufficient discharge power when mixed with acetylene, oxygen, or dry air. Peak discharge power was in the range 3–20 W and depended on the polarity of the voltage cycle being considered and depended also on chemical species in the admixture.

Safeguarding against Inactivation Temperatures during Plasma Treatment of Skin: Multiphysics Model and Phase Field Method

One of the most appealing applications of cold plasmas is medical treatment of the skin. An important concern is the capability to safeguard the non-targeted cells against inactivation temperatures during the plasma treatment. Unfortunately, it is problematic to experimentally determine the highest transient temperatures in these cells during the plasma treatment. In the present work, a complete multiphysics model was built based on finite element analysis using phase field method coupled with heat transfer and fluid dynamics to study the discharge phenomenon of cold plasma with helium carrier gas ejected out of a tube for skin treatment. In such plasmas with carrier gas, the fractions of plasma constituents are small compared to the carrier gas, so thermofluid analysis is needed for the carrier gas as the major contributor to the fluid and heat flow. The phase field method has been used to capture the moving helium gas in air, which has enabled us to compute fluid dynamics parameters for each phase individually. In addition to computational fluid dynamic analyses, we have also considered heat transfer in the fluids and to the skin using the Fourier law of heat conduction, which led to a multiphysics system. In the present paper, various flow velocities and tube-to-target distances (TTDs) have been considered to reveal the dependence of the fluid discharge output parameters on the flow and efficiency of heat transfer to the skin and the surrounding environment. The built model is a useful tool for future development of plasma treatment devices and to safeguard the non-targeted cells against inactivation temperatures.

Chemical and physical effect of SiO2 and TiO2 nanoparticles on highly hydrophobic fluorocarbon hybrid coatings synthesized by atmospheric plasma

The impact of the presence of TiO2 and SiO2 nanoparticles on the properties of fluorocarbon films synthesized by atmospheric pressure plasma in argon and helium is investigated in this study. The hydrophobicity, chemical composition and roughness of the films are analyzed by Water Contact Angle (WCA), X-Ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and profilometry. As expected, a significant impact of the nanoparticles on the roughness and therefore on the hydrophobicity of the films is observed and so regardless their nature. However, we show that the impact of the nanoparticles is different whether He or Ar are use as plasmagen gas, as He doesn't induce a significant intrinsic roughness, whereas Ar does. We show that the presence of SiO2 nanoparticles underneath the deposited film has no influence on the chemical composition of the films whatever the deposition time, the plasma power and the carrier gas (helium or argon) are. On the contrary, the presence of TiO2 nanoparticles leads to the degradation of the coatings over time. The influence of the plasma power of the discharge and the deposition time is also discussed. Finally, superhydrophobic coatings are synthesized by increasing the concentration of nanoparticles underneath the deposited films.

Evolutionary clade affects resistance of Clostridium difficile spores to Cold Atmospheric Plasma

Clostridium difficile is a spore forming bacterium and the leading cause of colitis and antibiotic associated diarrhoea in the developed world. Spores produced by C. difficile are robust and can remain viable for months, leading to prolonged healthcare-associated outbreaks with high mortality. Exposure of C. difficile spores to a novel, non-thermal atmospheric pressure gas plasma was assessed. Factors affecting sporicidal efficacy, including percentage of oxygen in the helium carrier gas admixture, and the effect on spores from different strains representing the five evolutionary C. difficile clades was investigated. Strains from different clades displayed varying resistance to cold plasma. Strain R20291, representing the globally epidemic ribotype 027 type, was the most resistant. However all tested strains displayed a ~3 log reduction in viable spore counts after plasma treatment for 5 minutes. Inactivation of a ribotype 078 strain, the most prevalent clinical type seen in Northern Ireland, was further assessed with respect to surface decontamination, pH, and hydrogen peroxide concentration. Environmental factors affected plasma activity, with dry spores without the presence of organic matter being most susceptible. This study demonstrates that cold atmospheric plasma can effectively inactivate C. difficile spores, and highlights factors that can affect sporicidal activity.

A universal method of sample preparation for liquid, solid, and gaseous samples based on a conversion solid-electrolyte reactor for measuring the isotope composition of light elements

A universal conversion solid-electrolyte reactor (SER) based on zirconium dioxide stabilized by yttrium oxide is developed. It ensures the complete oxidation of organic compounds of complex molecular structure in different physical states or the complete reduction of water and organic oxygen-containing substances in a flow of helium carrier gas. The optimum oxidation operation mode of the solid-electrolyte reactor is the mode ensuring the complete oxidation of organic compounds at the boundary line of the oxidation of organic compounds and, at the same time, prevents the inflow of oxygen from the environment to the carrier gas. The potential of the working electrode selected for carrying out experiments was equal to–175 mV (oxidation operation mode). The temperature of the reactor was 940–950oC. The standard deviations δ13СVPDB for organic substances oxidized by SER varied from 0.11 to 0.57‰ and were smaller than standard deviations in the oxidation of corresponding compounds in a commercial reactor. In using the SER–IRMS method (isotope ratio mass spectrometry combined with the solid-electrolyte reactor), a minimum amount of water (60–100 ng) was required. Standard deviations δDVSMOW attained using SER and using a commercial pyrolytic reactor were close to each other. Because of the simplicity and reliability of the design, the developed SER can successfully replace commercial oxidation and reduction reactors in isotope ratio mass spectrometry. In addition, the solid-electrolyte reactor can serve as a chromatographic detector, requiring no calibration in contrast to other detectors.

Possibility of loading the chamber of the “central” pelletized cold moderator for IBR-2 reactor beams 1, 4–6, and 9

This paper presents the results of experiments performed at the cold moderator test stand with beams 1, 4–6, and 9 for studying the possibility of loading the moderator chamber with frozen balls (pellets) 3.5 to 3.8 mm in diameter through the cryogenic pipeline of complex configuration with a 4-m-long section ascending at an angle of 50°. The optimum parameters for the successful loading of the moderator chamber are found to be the following: mass flow rate of the carrier gas (helium), 2 g/s; temperature of the pipeline walls and helium, 79–85 K; angular velocity of the disc in the ball dispenser, 3.6°/0.5 s; ball ejection rate from the dispenser to the pipeline, 8 balls/s; and maximum chamber loading time, 6 h. During the construction of the test stand, the cryostat is replaced with a new one with two gas blowers, which is necessary for maintaining a low temperature in two independent cooling circuits (for two cold moderators or for a cold moderator and the test stand) and the software for the control of the operation parameters is modified.

Modifier-assisted differential mobility–tandem mass spectrometry method for detection and quantification of amphetamine-type stimulants in urine

An advantage of differential mobility spectrometry (DMS) is it provides an orthogonal mechanism to mass spectrometry (MS). The DMS-MS/MS detects analytes in the gas phase on the basis of differences in ion mobility in low and high electric fields, which makes DMS-MS/MS an alternative to chromatographic separation-MS. One drawback of DMS is its limited resolution and sensitivity, especially for detecting small molecules when using a nonpolar inert gas as the carrier gas. The present work has evaluated the effects on peak capacity of adding chemical modifiers to inert carrier gases (nitrogen, helium, argon and carbon dioxide). Use of a methanol-helium mixture gave improvements in both separation and sensitivity. Nine structurally similar amphetamine-type stimulants were determined in urine without pretreatment of the samples before analysis. After optimization of carrier gas, nature and concentration of chemical modifier, and DMS temperature, limits of detection ranging from 1.1 to 2.7 ng mL−1, with a linear range of three orders of magnitude (5–5000 ng mL−1) were achieved. Precision was <15% and the accuracy of the quality control samples was 87.6–113.7%. For the quantitation of urine samples from drug abusers, data obtained using DMS-MS/MS showed reasonable agreement (within ±19.5%) with that obtained using LC-MS/MS. The analysis time for DMS-MS/MS was only 1.1 min and a paired sample t-test between the two methods gave a p-value of 0.0894, which indicates that DMS-MS/MS is a reliable method, with comparable precision and sensitivity to LC-MS/MS.

Investigation of the main influencing parameters on the degassing behavior of titanium carbonitrides using mass spectrometry

It is well known that titanium carbonitrides (Ti(C,N)) release carbon monoxide (CO) and nitrogen (N2) upon heat treatment, which can influence further processing such as sintering. Thus a deeper understanding concerning the driving forces of the degassing behavior could facilitate the development of further processing steps. Therefore, the focus of this study was put on determining the main influencing factors of the degassing behavior of titanium carbonitrides during heat treatment. For this purpose, an application-oriented characterization method by modifying an evolving gas analysis device (EGA) was developed. Quadrupol mass spectrometry (MS) was applied to monitor the gas evolution as a function of temperature under vacuum. The evolving CO and N2 were transported to the mass spectrometer using a helium carrier gas flow. Thermogravimetric analysis was deployed to complement the mass spectrometry data and to further elaborate on the outgassing behavior of the different sample species.Titanium carbonitride powders with different C/N/O ratios, grain size as well as free carbon content blended with typical binder metals (Co, Ni and Co+Ni) were investigated regarding their degassing behavior. The different C/N/O ratios influenced decisively the CO as well as the N2 outgassing in terms of quantity and temperature range. Consequently, a unique outgassing pattern, a “finger print”, was identified for each titanium carbonitride powder type. An altered grain size on the other hand, did not lead to a changed gas evolution. However, the content of free carbon was influencing the CO and the N2 outgassing significantly. The binder type, by contrast, was influencing the N2 evolution to a higher degree than the CO evolution.