Stream Of Nitrogen Research Articles

Development of Electrochemical Cell Combined with Gas Chromatograph for in-Situ Detection of Hydrogen Evolution on Mg

Magnesium (Mg) and its alloys are used for the negative electrode of the Mg air batteries because of its high reactivity in the aqueous solution. The hydrogen evolution on Mg in operation of Mg air batteries is one of the key issue because it may cause the self-discharge and loss of discharge capacity of Mg air batteries. The hydrogen evolution rate on Mg is increased when the anodic current is imposed to the Mg or Mg is anodically polarized above its corrosion potential. This phenomenon is called the negative difference effect, NDE. In order to clarify the NDE phenomenon, the volumetric hydrogen collection method was applied to the investigation of the hydrogen evolution on Mg during anodic dissolution1-3). We developed an electrochemical cell combined with a gas chromatograph 4). It allows the qualitative and quantitative analysis of the gas generated on working electrode because the gas is directly delivered to a gas chromatograph by a stream of carrier gas 4). The details of the developed system and measurement conditions are described as follows. The working electrode and counter electrode were an Mg and Pt respectively. In order to avoid the mixing of gases evolved on each electrode surface, the working electrode and counter electrode were placed in compartments separated by a glass filter and polymer membrane. The reference electrode was a KCl-saturated Ag/AgCl electrode (SSE). The electrolyte solution was 0.5 M NaCl of 10 ml, which was degassed by a nitrogen stream for 1 h before the measurement. The potentiostatic polarization was performed at -1.3 V vs. SSE for 2000 s. The gas-chromatographic measurements were performed starting 2 min after starting potentiostatic polarization. The hydrogen evolution rate was estimated by the results of the gas-chromatographic analysis. The volume of hydrogen gas V H2 (mL) and the hydrogen evolution rate v (mol s−1) are derived by the following equations. VH2 =Pc ×Cs ×A×Vs /(Pa ×As ×100) (1) ν=VH2 ×Ψ/(Vs ×22400×S) (2) In these equations, P c is the pressure of carrier gas (kPa), C s is the concentration of standard gas (%), A is the peak area of evolved hydrogen gas in the chromatogram (cm2), V s is the volume of the sample loop (ml), P a is the atmospheric pressure (kPa), A s is the peak area of standard hydrogen gas in the chromatogram (cm2), y is the flow rate of carrier gas (mL s−1), and S is the effective electrode surface area (cm2). In the present study, we determined the hydrogen evolution rate on Mg during the anodic dissolution by the developed system4). In addition, a nitrogen gas was investigated by the gas-chromatographic analysis during the anodic dissolution of Mg. The effect of solubility of hydrogen in the electrolyte solution on the amount of hydrogen gas detected by the present method was discussed. Reference: [1] G. S. Frankel, A. Samaniego and N. Birbilis, Corros. Sci., 70, 104 (2013). [2] S. Lebouil, A. Duboin, F. Monti, P. Tabeling, P. Volovitch, K. Ogle, Electrochim.Acta., 128, 284 (2013). [3] S. Fajardo and G. S. Frankel, J. Electrochem. Soc., 162, C693 (2015). [4] Y. Hoshi, R. Takemiya, I. Shitanda, and M. Itagaki, J. Electrochem. Soc., 163, C303 (2016).

Low Density Solvent Ion Pair Dispersive Liquid–Liquid Micro‐Extraction – An Economic Method for Extraction of Phthalic Acids

A simple and economic analytical method based on low density solvent ion‐pair dispersive liquid–liquid micro‐extraction using high performance liquid chromatography–diode array detection has been used for the determination of phthalic acid, terephthalic acid, and iso‐phthalic acid in aqueous samples. In this work, 0.75 mL methanol (as a disperser solvent), 90 μL toluene (as an extraction solvent), and 15 μL tri‐butyl amine (as an ion pair reagent) were injected into aqueous phase. After centrifuging (at 4000 rpm for 5 min), the analyte ion pairs were extracted into toluene. The collected toluene was withdrawn and transferred into a microtube. The transferred toluene was evaporated under a stream of nitrogen at room temperature to dryness. Then, 10 μL of the mobile phase was added to the microtube to re‐dissolve the residues. Under the optimized conditions, limits of detection and quantification were calculated in the range of 0.12–0.34 and 0.37–1.06 ng mL−1, respectively. The linear range of the developed method was obtained as 0.37–10000 ng mL−1. Enrichment factors and extraction recoveries were from 82 to 98% and 411–492, respectively. Finally, different aqueous samples such as tap water, mineral water, cola, lemon juice, vinegar, and dextrose and NaCl injection solutions were analyzed successfully by the developed procedure and the selected analytes were found in some of them in the range of 6.2–72 ng mL−1.

Follow the N and P road: High-resolution nutrient flow analysis of the Flanders region as precursor for sustainable resource management

Resource-efficient nutrient management is key to secure food production in the context of a growing global population, rising resource scarcity and increasing pressure on the environment. To map the potential towards increasing nutrient use efficiencies and reduce environmental losses, a high-resolution insight of the nitrogen (N) and phosphorus (P) nutrient streams is pivotal. In this study, a substance flow analysis for N and P is presented for the nutrient intensive region of Flanders (6,211,065 inhabitants) in Belgium for the year 2009. A set of 160 nutrient fluxes was quantified throughout 21 economic and environmental compartments, with a particular focus on 10 waste management processes. A total nutrient load of 20kg N cap−1yr−1 (ca. 73% to the air and 28% to surface waters) and 0.53kg P cap−1 yr−1 (to surface waters) is emitted to the environment; with crop and livestock production as the main contributors (49% of N and 36% of P). The food supply chain revealed a fertilizer-to-consumer efficiency of 14% for N as well as for P, with important losses embedded in waste streams such as excess manure. Advanced manure and waste processing facilities nevertheless offer the opportunity for enhanced nutrient recycling to increase the nutrient use efficiencies and reduce the dependency of inorganic fertilizers.

Evaluation of various soaking agents as a novel tool for pesticide residues mitigation from cauliflower (Brassica oleracea var. botrytis).

The increasing use of pesticides for boosting the yield of agricultural crops also impart toxic residues which ultimately extend to numerous physiological disorders upon consumption. The present study was designed as an effort to assess the reduction potential of various chemical solutions and to minimize the pesticide residues in cauliflower (Brassica oleracea var. botrytis). The samples were soaked in various solutions along with tap water to mitigate pesticide residues. Afterwards, the extracted supernatant was passed through column containing anhydrous sodium sulfate trailed by activated carbon for clean-up. Eluents were first evaporated and then completely dried under gentle stream of Nitrogen. Finally, the residues were determined using gas chromatography equipped with electron capture detector (GC-ECD). Results revealed the highest reduction of endosulfan, bifenthrin and cypermethrin residues with acetic acid (10%) was 1.133±0.007 (41%), 0.870±0.022 (60%) and 0.403±0.003 (75%), respectively among the tested solutions. However, simple tap water treatment also resulted in 0.990±0.02 (12%), 1.323±0.015 (14%) and 1.274±0.002 (21%) elimination of endosulfan, bifenthrin and cypermethrin residues, respectively. Moreover, among various solutions, acetic acid depicted maximum reduction potential followed by citric acid, hydrogen peroxide, sodium chloride and sodium carbonate solutions. The percent reduction by various solutions ranged from 12 to 41, 14 to 60 and 21 to 75% for the elimination of endosulfan, bifenthrin and cypermethrin residues, respectively.

Control of a recuperative vapor- recompression air separation process

The use of oxy-combustion for producing furnace stack gases with low nitrogen and high carbon dioxide concentrations is a potential method for economical sequestration of green house gases. A conventional air separation unit to provide oxygen compresses all the air feed and operates with one of the two cryogenic distillation columns at elevated pressure so heat integration can be employed.The use of recuperative vapor recompression has been recently proposed in which only a portion of a nitrogen stream is compressed to provide liquid reflux to two columns, which both operate at low pressure where the separation is easier. Steady-state designs have been developed and economically optimized.The purpose of this paper is to explore the dynamic controllability of this type of vapor recompression system for air separation.

Simultaneous pentafluorobenzyl derivatization and GC-ECNICI-MS measurement of nitrite and malondialdehyde in human urine: Close positive correlation between these disparate oxidative stress biomarkers.

Urinary nitrite and malondialdehyde (MDA) are biomarkers of nitrosative and oxidative stress, respectively. At physiological pH values of urine and plasma, nitrite and MDA exist almost entirely in their dissociated forms, i.e., as ONO- (ONOH, pKa=3.4) and -CH(CHO)2 (CH2(CHO)2, pKa=4.5). Previously, we reported that nitrite and MDA react with pentafluorobenzyl (PFB) bromide (PFB-Br) in aqueous acetone. Here, we report on the simultaneous derivatization of nitrite and MDA and their stable-isotope labeled analogs O15NO- (4μM) and CH2(CDO)2 (1μM or 10μM) with PFB-Br (10μL) to PFBNO2, PFB15NO2, C(PFB)2(CHO)2), C(PFB)2(CDO)2 by heating acetonic urine (urine-acetone, 100:400μL) for 60min at 50°C. After acetone evaporation under a stream of nitrogen, derivatives were extracted with ethyl acetate (1mL). A 1-μL aliquot of the ethyl acetate phase dried over anhydrous Na2SO4 was injected in the splitless mode for simultaneous GC-MS analysis in the electron capture negative-ion chemical ionization mode. Quantification was performed by selected-ion monitoring (SIM) the anions [M-PFB]-m/z 46 for ONO-, m/z 47 for O15NO-, m/z 251 for -C(PFB)(CHO)2, and m/z 253 for -C(PFB)(CDO)2. The retention times were 3.18min for PFB-ONO2/PFB-O15NO2, and 7.13min for -C(PFB)(CHO)2/-C(PFB)(CDO)2. Use of CH2(CDO)2 at 1μM but not at 10μM was associated with an unknown interference with the C(PFB)2(CDO)2 peak. Endogenous MDA can be quantified using O15NO- (4μM) and CH2(CDO)2 (10μM) as the internal standards. The method is also useful for the measurement of nitrate and creatinine in addition to nitrite and MDA. Nitrite and MDA were measured by this method in urine of elderly healthy subjects (10 females, 9 males; age, 60-70 years; BMI, 25-30kg/m2). Creatinine-corrected excretion rates did not differ between males and females for MDA (62.6 [24-137] vs 80.2 [52-118]nmol/mmol, P=0.448) and for nitrite (102 [71-174] vs. 278 [110-721]nmol/mmol P=0.053). We report for the first time a close correlation (r=0.819, P<0.0001) between MDA and nitrite in human urine. This correlation is assumed to be due to involvement of myeloperoxidase which catalyzes the formation of hypochlorite (-OCl) from chloride and hydrogen peroxide. In turn, hypochlorite reacts both with nitrite and with polyunsaturated fatty acids such as arachidonic acid, with the later reaction generating MDA. The proposed mechanisms are supported by the literature but remain to be fully explored.

Simple Method for Determination of Fungicides in Citrus Fruits by Liquid Chromatography–Tandem Mass Spectrometry

A simple method for the determination of four fungicides (thiabendazole, imazalil, o-phenylphenol, and diphenyl) in citrus fruits has been developed. After spiking surrogates of these fungicides, the sample was extracted with acetonitrile, salted out, and the water was simultaneously removed using anhydrous magnesium sulfate and sodium chloride. The extract was first purified with a primary secondary amine and octadecylsilane, followed by the addition of dimethyl sulfoxide as a keeper solvent, and subsequently concentrated under a nitrogen stream. The compounds were analyzed by liquid chromatography–tandem mass spectrometry using the atmospheric pressure photoionization interface. The recoveries and relative standard deviations (RSDs) of the fungicides (1 mg kg−1) were satisfactory (recovery 92–114 %; RSD <10 %). An evaluation with Shewhart QC plots revealed that all data points are within the controlled area, thus confirming the robustness of the method for analyzing the fungicide content of citrus fruits. The sample preparation time for ten samples was approximately 2 h, highlighting the time and labor efficiency of the method.

OPTIMIZATION OF CONCENTRATION CONDITIONS FOR FOOD PRODUCTS WITH HIGH HUMIDITY

According to the research, for improving the properties of unripe and partly sour honey, its concentration can be achieved by increasing the evaporation surface area of the products to be processed in vacuum conditions as well as in an open boiler under the recommended mode for heating honey (up to 45 °C). To stabilize fruits and accelerate the process of concentration in the liquids as well as mechanical mixtures of liquids for jams and fruit purees, it is recommended to premix the pulp with food sugar enzymatic hydrolysate (invert sugar), then obtain the mix at relatively moderate temperature (55-60°C), for which the intensive thickening technology has been developed using the above-mentioned method (Copyright of deposition #5870,2014, “Sakpatenti”) and easily oxidizable substances of fruits are protected in gaseous nitrogen stream. Due to these changes, honey, invert sugar syrup, fruit juices and fruit pulp preserve their original properties, hydroxymethylfurfural (HMF) content in the finished product was within 0.5-5.0mg/kg, decrease of water content was 17-20 mass % in an hour, if the liquid mass concentration of the mixture was 23-64 mass%. This paper contains 1 table, 7 figures and 6 literary sources. Materials of the research, which formed the basis for the development of new technology, have not been published in any other source of scientific information.

A novelty strategy for the fast analysis of sulfonamide antibiotics in fish tissue using magnetic separation with high-performance liquid chromatography-tandem mass spectrometry.

A simple, fast and low-cost extraction method with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) determination was developed on sulfonamide antibiotics (SAs) in fish tissue. Magnetic separation was first introduced into the rapid sample preparation procedure combined with acetonitrile extraction for the analysis of SAs. Partitioning was rapidly achieved between acetonitrile solution and solid matrix by applying an external magnetic field. Acetonitrile solution was collected and concentrated under a nitrogen stream. The residue was redissolved with 1‰ formic acid aqueous solution and defatted with n-hexane before analysis. The recoveries of SAs were in the range of 74.87-104.74%, with relative standard deviations <13%. The limits of quantification and the limits of detection for SAs ranged from 5.0 to 25.0 μg (kg-1) and from 2.5 to 10.0 μg (kg-1) , respectively. The presented extraction method proved to be a rapid method which only took 20 min for one sample preparation procedure. Copyright © 2016 John Wiley & Sons, Ltd.

Validation of an Analytical Method for Determination of 13 priority polycyclic aromatic hydrocarbons in mineral water using dispersive liquid-liquid microextraction and GC-MS.

Dispersive liquid-liquid microextraction (DLLME) combined with gas chromatography-mass spectrometry (GC-MS) was used for the extraction and determination of 13 polycyclic aromatic hydrocarbons (PAHs) in mineral water samples. In this procedure, the suitable combination of extraction solvent (500 µL chloroform) and disperser solvent (1000 µL acetone) were quickly injected into the water sample (10.00 mL) by Hamilton syringe. After centrifugation, 500 µL of the lower organic phase was dried under a gentle stream of nitrogen, re-dissolved in chloroform and injected into GC-MS. Chloroform and acetone were found to be the best extraction and disperser solvent, respectively. Validation of the method was performed using spiked calibration curves. The enrichment factor ranged from 93 to 129 and the recovery ranged from 71 to 90%. The linear ranges for all the PAHs were 0.10-2.80 ngmL(-1). The relative standard deviations (RSDs) of PAHs in water by using anthracene-d10 as internal standard, were in the range of 4-11% for most of the analytes (n = 3). Limit of detection (LOD) for different PAHs were between 0.03 and 0.1 ngmL(-1). The method was successfully applied for the analysis of PAHs in mineral water samples collected from Tehran.

A novel method for drop in drop edible oils encapsulation with chitosan using a coaxial technique

The presented work concerns a novel one step method for oil encapsulation. In this coaxial system the oil constitutes the core of the capsule, while the chitosan solution is the polymer shell surrounding the core to provide separation of the core from the external environment. The paper contains a diagram of the encapsulation equipment and explains the principle of its operation. The experimental results showed the impact of the media flow rate on the size, shape, mechanical properties and the amount of oil in the capsules. Conditions of the core solution were determined to be: 2.00g/h, and shell solution: 4.45g/h. Maximal oil content obtained under these conditions was: 45.2%. The diameters of the capsules collected gravitationally in the nitrogen stream were from 3.7 to 4.4mm and from 2.8 to 4.3mm, respectively. The force needed to obtain 50% compression strain of all tested samples was in the range from 0.11 to 0.19N. In comparison to other encapsulation methods, the presented technique is much simpler and can be performed under mild conditions. Moreover, the use of natural polymers as a coating matrix enables the use of the described technique in many branches of industry.

Absorption in wetted-wall column with phase properties close to distillation conditions

Our present research re-opens the problem of recalculation of the mass-transfer data between absorption and distillation by performing both processes in devices of the same geometry and using absorption and distillation systems whose physical properties are as similar as possible. The wetted wall column has been chosen as an experimental device which assures identical and known effective interfacial area for both processes. In this paper we present results of the absorption experiments while the follow up article will focus on the distillation ones and their mutual comparison. The liquid side mass-transfer coefficients were measured using desorption of oxygen from primary alcohols to the stream of nitrogen in the range of the liquid phase Reynolds numbers from 30 to 560. The experiments were carried out at ambient and at elevated temperatures providing the range of liquid phase Schmidt numbers from 66 to 1300. The gas phase mass-transfer coefficient was measured using absorption of sulfur dioxide from various carrier gasses-air, helium and sulfur hexafluoride-into the sodium hydroxide aqueous solution for Reynolds numbers from 300 to 11,800. Due to the significantly different properties of the carrier gases the range of the gas phase Schmidt number from 0.45 to 2.75 was achieved. The range of Reynolds numbers and Schmidt numbers covered by the absorption experiments overlaps the range of the distillation experiments, thus no extrapolation will be needed for the recalculation of the mass-transfer coefficients from absorption to distillation conditions. The results of the absorption experiments have been correlated in the dimensionless form ShL=0.33ReL0.12ScL0.47 and ShG=0.012ReLG0.90ScG0.61 with RSD of 6% and 4% respectively.

Processing of Cr-Mo Alloy Steel via PM Route

Fe-Cr-Mo alloy steel with addition of 0.4 weight percentage graphite has been processed via Powder Metallurgy route. Green compacts prepared at 650 MPa pressure were sintered at 1120°C and 1200°C for one hour and cooled at 6.0°C/min in a stream of nitrogen and hydrogen (90%N2+10%H2). The sintered microstructure consists of a ferrite and pearlite with some cementite at the boundaries. Presence of chromium oxide was observed in samples sintered at 1120°C. In the present sintering conditions there was no significant difference in the density achieved at 1120°C and 1200°C. No oxide formation was observed at 1200°C. This resulted in improved mechanical properties as compared to specimen sintered at 1120°C.

Self-Assembled Nanospheres for Encapsulation and Aerosolization of Rifampicin.

Rifampicin (RIF) is a benchmark drug for treatment of tuberculosis, but poor bioavailability, prolonged treatment, and pill burden have been linked to therapeutic failure and the development of multidrug resistant strains. To overcome these limitations, this study investigated a method of rifampicin nanoencapsulation and aerosol delivery using a commercial, hand-held nebulizer modified with a nitrogen stream.

Bed Agglomeration during the Steam Gasification of a High-Lignin Corn Stover Simultaneous Saccharification and Fermentation (SSF) Digester Residue

This research investigates the bed agglomeration phenomena during the steam gasification of a high-lignin residue produced from the simultaneous saccharification and fermentation (SSF) of corn stover in a bubbling fluidized bed. The studies were conducted at 895 °C using alumina as bed material. Biomass was fed at 1.5 kg/h, while steam was fed to give a velocity equal to 2.5 times the minimum fluidization velocity, with a steam/carbon ratio of 0.9. The pelletized feedstock was co-fed with a cooling nitrogen stream to mitigate feed line plugging issues. Tar production was high at 50.3 g/Nm3, and the fraction of C10+ compounds was greater than that observed in the gasification of traditional lignocellulosic feedstocks. Carbon closures over 94% were achieved for all experiments. Bed agglomeration was found to be problematic, indicated by pressure drop increases observed below the bed and upstream of the feed line. Two size categories of solids were recovered from the reactor: +0.25 mm and −0.25 mm. After 2.75 h of experiment, 61.7 wt % was recovered as −0.25 mm particles and 38.2 wt % of the recovered reactor solids were +0.25 mm. A sizable percentage (31.8 wt %) was +0.841 mm. The −0.25 mm particles were mainly formed by the initial bed material (Al2O3). Almost 50 wt % of the +0.841 mm particles was found to be formed by organics. The unreacted carbon remaining in the reactor resulted in a low conversion rate to product gas. Inductively coupled plasma–atomic emission spectroscopy (ICP-AES), scanning electron microscopy–energy-dispersive spectroscopy (SEM-EDS), and X-ray diffraction (XRD) confirmed that the large agglomerates (+0.841 mm) were not encapsulated bed material but rather ungasified feedstock pellets with sand particles attached to it.

A fully automated effervescence assisted dispersive liquid–liquid microextraction based on a stepwise injection system. Determination of antipyrine in saliva samples

A first attempt to automate the effervescence assisted dispersive liquid–liquid microextraction (EA-DLLME) has been reported. The method is based on the aspiration of a sample and all required aqueous reagents into the stepwise injection analysis (SWIA) manifold, followed by simultaneous counterflow injection of the extraction solvent (dichloromethane), the mixture of the effervescence agent (0.5 mol L−1 Na2CO3) and the proton donor solution (1 mol L−1 CH3COOH). Formation of carbon dioxide microbubbles generated in situ leads to the dispersion of the extraction solvent in the whole aqueous sample and extraction of the analyte into organic phase. Unlike the conventional DLLME, in the case of EA-DLLME, the addition of dispersive solvent, as well as, time consuming centrifugation step for disruption of the cloudy state is avoided. The phase separation was achieved by gentle bubbling of nitrogen stream (2 mL min−1 during 2 min).The performance of the suggested approach is demonstrated by determination of antipyrine in saliva samples. The procedure is based on the derivatization of antipyrine by nitrite-ion followed by EA-DLLME of 4-nitrosoantipyrine and subsequent UV–Vis detection using SWIA manifold. The absorbance of the yellow-colored extract at the wavelength of 345 nm obeys Beer's law in the range of 1.5–100 µmol L−1 of antipyrine in saliva. The LOD, calculated from a blank test based on 3σ, was 0.5 µmol L−1.

Steam reforming of dodecane and toluene over Ru/12SrO–7Al2O3 (S12A7) catalysts

Catalytic steam reforming of liquid fuels such as kerosene is an important route for hydrogen production for the fuel cells. However, there is serious catalyst deactivation due to the carbon deposition on the catalyst. In this study, in order to develop a catalyst that has superior catalytic performance for steam reforming of kerosene, 12SrO–7Al2O3 (S12A7) that can incorporate active oxygen ions into the nanocage, was paid attention as a support material, subsequently steam reforming of dodecane and toluene as kerosene model compounds was performed over various Ru/SrO–Al2O3 catalysts with S12A7 phase. The Ru/SrO–Al2O3 catalysts with high S12A7 content exhibited higher catalytic activity than a commercial Ru/Al2O3 catalyst, despite low Ru loading and Ru dispersion. The S12A7 content in the SrO–Al2O3 support was remarkably affected by the calcination conditions such as temperature, moisture, and cooling rate. The S12A7 content was the highest in the SrO–Al2O3 support calcined at 873K in a stream of moist nitrogen (pH2O: 1.9kPa). The turnover frequency (TOF) for steam reforming of dodecane over Ru/SrO–Al2O3 catalysts exponentially increased with an increase in the S12A7 content. This result indicates that the active oxygen species in S12A7 contribute to the acceleration of oxidation of CHx species on Ru metals.

P156: Detection adducts DNA in human blood and lung cancer tissue by a hybrid quadrupole time-of-flight (Q-TOF) mass spectrometer

Background Identification of DNA-based biomarkers of cancer cells is highly promising and rapidly developing direction that can advance early detection and therapy of malignancies. DNA adducts are felicitous markers of cancer, because their chemical structure is significantly different from that of mutated or methylated DNA, that allows to determine them with high precision using mass spectrometry. The aim of this work is to develop the methodology of sample preparation and its mass spectrometric analysis. Samples were prepared from the blood plasma and from the tumor tissue from lung cancer patients and from blood of healthy individuals. Materials and methods DNA was isolated from the blood plasma and tissue by using column method (BioSilica, Russia) The final yield from 1 ml of blood was 100 ng. DNA samples were subjected to acid hydrolysis (1 M HCl) at 70 °C. After 3 h, the hydrolysis was stopped by cooling on ice for 5 min and later on adding an equivalent amount of an alkali and a phosphate buffer solution (pH 7). To assess the extent of hydrolysis of the samples they were analysed by electrophoresis on a 1.2% agarose gel in Tris-acetate buffer. The samples were extracted at cartridge HF Bond Elut-C18 100 mg, 1 ml (Agilent Technologies, USA) and eluted in several fractions with a gradual increase of methanol in the eluent. Stream of nitrogen was applied to dry the extract. The samples were subjected to mass spectrometric analysis after pre-separation by UHLC Ultimate 3000 RS (Dionex, USA) in a column Dionex Acclaim RSLC 120 C18 (2.1 × 50 mm 120 A, 0.2 μm) flow rate of 0.5 ml/min using as eluents 0.1% solution of formic acid in water (A) and 0.1% solution of formic acid in atsetontrile (B). Elution was carried out in gradient mode: (%B): 0–3min (5%), 3–28min (5–95%), 28–30 min (95%), 30–31 min (95–5%), 31–35 min (5%). Mass spectrometry was carried out on ESI-qTOF ultrahigh resolution Maxis 4G (Bruker, Germany) in the positive ion detection mode range 50–1000 m/z, 2 Hz with the following settings electrospray ion source: CV 3800 V, Nebulizer gas 1 bar, Dry Gas 8 l/min, Dry Temp: 200 °C. Results It was found that the DNA which was cleaved with acid hydrolysis in the result contained single DNA bases. The samples were stable at 4 °C for at least 7 days. The optimal eluent for solid phase extraction of DNA is 80% solution of methanol in water. The number of DNA adducts was evaluated by the integrated value of the mass spectrometric response detector. It was shown that most amount of adducts 4-hydroxy-1-(3-pyridyl)-1- butanone and N3-(2-carbamoyl-2-hydroxyethyl)adenine was found in DNA samples derived from tumor tissue. The adduct N7-(2-carbamoyl-2-hydroxyethyl)guanine was found in tumor tissue samples and DNA derived from plasma, as well as in all samples of healthy tissue. Conclusion The established protocol of DNA sample preparation followed by analysis using a mass spectrometer high resolution allows to detect the content of the DNA adducts in small DNA probes (100 ng). We found, that acid hydrolysis is cheaper and more practical in comparison to enzymatic digestion in order to generated samples containing single DNA bases without damaging the structure of adducts. This research was supported by Federal Targeted Programme for Research and Development in Priority Areas of Development of the Russian Scientific and Technological Complex for 2014–2020, “Development of molecular signatures for early detection of lung cancer” (No. 14.575.21.0064 from 05.08.2014, RFMEFI57514X0064) and supported by Tomsk State University, Competitiveness Improvement Program”. Work was conducted with the application of the Tomsk regional common use center technical equipment acquired thanks to a grant of the Russian Ministry of the Agreement No.14.594.21.0001 (RFMEFI59414X0001).

Determination of nine hydroxylated polybrominated diphenyl ethers in water by precolumn derivatization-gas chromatography–mass spectrometry

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs), acting as emerging endocrine disruptors, have aroused more and more concern recently. Produced from natural source or metabolism of PBDEs, OH-PBDEs are more toxic than their parent compounds. However, few analytical methods are available for sensitive determination of these compounds especially in water. In this study, a method of determination of nine OH-PBDEs in lake, reservoir, river and sewage treatment plant effluent was established using N,O-bis (trimethylsilyl) trifluoroacetamide (BSTFA) as derivatization reagent combined with gas chromatography–mass spectrometry (GC–MS). Optimal extraction solvent and derivatization factors such as the amount of BSTFA, time, temperature and dissolution solvent were determined experimentally. After extracted by hexane–dichloromethane (1:1, v/v), extracts were evaporated to almost dry, then BSTFA was added to the residue and heated at 90°C for 30min. The remains were dried under a stream of nitrogen and redissolved in hexane. The solution was separated in DB-35MS column, then determined by GC–MS in selected ion mode and full scan monitoring mode, and quantified by external standard method. The working curves were obtained using sample matrix in order to eliminate the matrix interference. Linear range was from 0.02μgL−1 to 30μgL−1. Limits of detection and quantification ranged from 0.0039μgL−1 to 0.0220μgL−1 and 0.0130μgL−1 to 0.0733μgL−1, respectively. Two different spiked levels were measured with 5 parallel tests for each level. The results indicated that the relative standard deviations were less than 14.08%. The method has been applied to lake water, reservoir water, river water and sewage treatment plant effluent. Five OH-PBDEs including 2′-OH-BDE3, 3′-OH-BDE7, 2′-OH-BDE28, 4′-OH-BDE17 and 5′-OH-BDE99 were detected in all the samples collected in Baoding, China. This method is simple, high sensitive, and suitable for simultaneous determination of nine OH-PBDEs in different environmental water.

Quantification of buprenorphine and the metabolites of methadone and heroin in hair of patients in rehabilitation programs by GC–MS

Quantification of buprenorphine and the metabolites of methadone and heroin in hair of patients in rehabilitation programs by GC–MS