Semi-global mechanisms for the oxidation of diammonium phosphate impregnated wood

Thermogravimetric measurements in air of fir wood impregnated with diammonium phosphate in the concentration range 2-20% and heating rates between 5 and 20 K/min show the existence of three sequential stages: wood decomposition, induction and char oxidation. The additive causes an anticipation in the decomposition stage up to about 100 K, a reduction in the maximum rate up to a factor of three and an increase in the charred solid residue from about 30 to 60%. The total duration of the induction and oxidation stages is also increased. The experimental curves are interpreted by either a three-step mechanism (one reaction for each stage) or a seven-step mechanism (three reactions for decomposition and two reactions for the induction and oxidation stages). The estimated kinetic parameters are independent from the heating rate but vary with the diammonium phosphate concentration. However, for both mechanisms, the activation energies of the various steps remain practically constant except for the decomposition of the cellulose component or the decomposition step, depending on the complexity of the mechanism.     

Analysis of peptides and proteins using sub-2 μm fully porous and sub 3-μm shell particles

The objective of this study was to evaluate the potential of sub-2 μm totally porous particles and sub-3 μm shell particles for peptide and protein analysis. Specific analytical strategies must be developed for these biomolecules as their importance in the pharmaceutical industry increases and as their structural complexity involves some issues when classical LC conditions are employed. Attention was paid on comparing these different columns in various LC conditions (different temperatures, gradient times, and mobile phase flow rates). The comparison of the different supports was assessed considering columns characteristics (quality of packing, silanol activity, pore size, totally porous or shell particles). In this article, peptides were first analyzed with both column technologies. Similar results to those achieved with low molecular weight compounds were obtained (peak capacity >100 for t_grad around 3 min and columns dimensions of 2.1 mm id × 50 mm), but specific conditions were required (elevated temperature and the use of a volatile ion-pairing reagent, namely TFA). For peptide analysis following tryptic digestion, the goal was to improve peak capacity and resolution because of the large number of generated peptides. For this purpose, longer columns packed with porous sub-2 μm or shell sub-3 μm particles (i.e., 150 mm) and gradient times (i.e., up to 30 min) were tested. On the other hand, proteins in their intact forms have higher molecular weights (MW > 5000 Da) and a tertiary structure, thus requiring different conditions in terms of stationary phase hydrophobicity (C₄vs. C₁₈) and pore size (300 vs. 120 Å). In addition, there were issues with adsorption onto the LC system and/or the column itself. This study showed that proteins with MWs lower than 40,000 Da required chromatographic conditions close to those employed for peptide analysis. For larger proteins, a C₄ 300 Å stationary phase gave the best results, confirming theoretical predictions.     

Determination of some refractory elements and Pb by fluorination assisted electrothermal vaporization inductively coupled plasma mass spectrometry with platform and wall vaporization

Platform and wall vaporization for electrothermal vaporization (ETV)-inductively coupled plasma mass spectrometry (ICP-MS) determination of some refractory elements (Ti, V, Cr, Mo, La and Zr) and Pb were comparatively studied with the use of poly (tetrafluoroethylene) (PTFE) as fluorinating reagent. The factors affecting the vaporization behaviors of the target analytes in the platform and tube wall vaporization including vaporization temperature and time, pyrolytic temperature and time were studied in detail, and the flow rates of carrier gas/auxiliary carrier gas, were carefully optimized. Under the optimal conditions, the signal profiles, signal intensity, interferences of coexisting ions and analytical reproducibility for wall and platform vaporization ETV-ICP-MS were compared. It was found that both wall and platform vaporization could give very similar detection limits, but the platform vaporization provided higher signal intensity and better precision for some refractory elements and Pb than the wall vaporization. Especially for La, the signal intensity obtained by platform vaporization was 3 times higher than that obtained by wall vaporization. For platform vaporization ETV-ICP-MS, the limits of detection (LODs) of 0.001 μg L⁻¹ (La) ~ 0.09 μg L^− 1 (Ti) with the relative standard deviations (RSDs) of 1.5% (Pb) ~ 15.5% (Zr) were obtained. While for wall vaporization ETV-ICP-MS, LODs of 0.005 μg L^− 1 (La) ~ 0.4 μg L^− 1 (Pb) with RSDs of 3.2% (Mo) ~ 12.8% (Zr) were obtained. Both platform and tube wall vaporization techniques have been used for slurry sampling fluorination assisted ETV-ICP-MS direct determination of Ti, V, Cr, Mo, La, Zr and Pb in certified reference materials of NIES No. 8 vehicle exhaust particulates and GBW07401 soil, and the analytical results obtained are in good agreement with the certified values.     

Intensified extraction of ionized natural products by ion pair centrifugal partition extraction

The potential of centrifugal partition extraction (CPE) combined with the ion-pair (IP) extraction mode to simultaneously extract and purify natural ionized saponins from licorice is presented in this work. The design of the instrument, a new laboratory-scale Fast Centrifugal Partition Extractor (FCPE300^®), has evolved from centrifugal partition chromatography (CPC) columns, but with less cells of larger volume. Some hydrodynamic characteristics of the FCPE300^® were highlighted by investigating the retention of the stationary phase under different flow rate conditions and for different biphasic solvent systems. A method based on the ion-pair extraction mode was developed to extract glycyrrhizin (GL), a biologically active ionic saponin naturally present in licorice (Glycyrrhiza glabra L., Fabaceae) roots. The extraction of GL was performed at a flow rate of 20 mL/min in the descending mode by using the biphasic solvent system ethyl acetate/n-butanol/water in the proportions 3/2/5 (v/v/v). Trioctylmethylammonium with chloride as a counter-ion (Al336^®) was used as the anion extractant in the organic stationary phase and iodide, with potassium as counter-ion, was used as the displacer in the aqueous mobile phase. From 20 g of a crude extract of licorice roots, 2.2 g of GL were recovered after 70 min, for a total process duration of 90 min. The combination of the centrifugal partition extractor with the ion-pair extraction mode (IP-CPE) offers promising perspectives for industrial applications in the field of natural product isolation or for the fractionation of natural complex mixtures.     

On the extra-column band-broadening contributions of modern, very high pressure liquid chromatographs using 2.1 mm I.D. columns packed with sub-2 μm particles

The efficiencies of two narrow bore columns (100 mm and 50 mm × 2.1 mm) packed with 1.7 μm totally porous BEH-C₁₈ particles were measured on two very high pressure liquid chromatographs (Acquity from Waters and 1290 Infinity HPLC System from Agilent) operating at maximum pressures of 1034 and 1200 bar, respectively. The probe compounds were a mixture of uracil, acetophenone, toluene, and naphthalene eluted in a 50/50 (v/v) solution of acetonitrile and water at 303 K with a flow rate of 0.40 mL/min. The apparent efficiencies of columns, which lumps the consequences of band broadening due to the column and the system contributions, may depend much on the extra-column volumes of the instruments used. Actually, it is known for a long time that the apparent column performance is strongly affected by the instrument characteristics, including the diameter of the connecting tubes, the injection technique (with or without needle seat capillary), and the detection cell volume. When the 1290 Infinity HPLC System is equipped with a needle seat, an inlet and an outlet connecting capillary tube with inner diameters around 115 μm, its extra-column variance for a 0.1 μL injection volume is 9.2 μL² while that of the Acquity instrument is 6.9 μL². Minor modifications suggested by their respective manufacturers allowed significant reductions of these variances, to 6.2 and 3.9 μL², respectively. Yet, in their optimized configurations and for weakly retained compounds (k ? 1), these modern, sophisticated instruments cannot provide more than 75% (1290 Infinity) and 85% (Acquity) of the maximum efficiency of a 2.1 mm × 50 mm BEH column. For more strongly retained compounds (k > 4), in contrast, they are both able to provide more than 95% of the maximum expected efficiency.     

Simultaneous extraction and clean-up of polybrominated diphenyl ethers and polychlorinated biphenyls from sheep liver tissue by selective pressurized liquid extraction and analysis by gas chromatography-mass spectrometry

We describe a selective pressurized liquid extraction (SPLE) method, followed by gas chromatography–mass spectrometry (GC–MS), for the simultaneous extraction and clean-up of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in sheep liver tissue samples. The on-line clean-up of liver tissue by SPLE was tested using differing amount of acid-modified silica (sulphuric acid:silica gel, 1:2, w/w), the most effective amount being 20 g. Different extraction solvents (iso-hexane and dichloromethane), either alone or in various combinations, were used to extract these target compounds from spiked liver samples. Variables affecting the SPLE extraction efficiency, including temperature, pressure, number of extraction cycles and static extraction time were studied; the optimum parameters were 80 °C, 10.3 MPa, 2 cycles and 5 min, respectively. The SPLE based method was compared with more traditional Soxhlet, off-line PLE, ultrasonic and heating extraction methods. Overall the mean percentage recoveries for all target chemicals using SPLE were 86–103% (n = 3, SD < 9%), and compared favourably with the Soxhlet (63–109%, n = 3, SD < 8%), off-line PLE (82–104%, n = 3, SD < 18%), ultrasonic (86–99%, n = 3, SD < 11%) and heating (72–102%, n = 3, SD < 21%) extraction methods. The limits of detection of the proposed method were 5–96 pg g⁻¹ and 2–29 pg g⁻¹ for the different PBDE and PCB chemicals studied, respectively. The outputs of the proposed method were linear over the range from 0.02 to 30 ng g⁻¹, for all PCB and PBDE congeners except for PBDE 100 and 153 (0.05–30 ng g⁻¹) and PBDE 183 (0.1–30 ng g⁻¹). The method was successfully applied to sheep liver samples for the determination of the target PBDE and PCB compounds.     

Application of fast ultrasound water-bath assisted enzymatic hydrolysis--high performance liquid chromatography-inductively coupled plasma-mass spectrometry procedures for arsenic speciation in seafood materials

Enzymatic hydrolysis of seafood materials for isolating arsenic species (As(III), As(V), DMA and AsB) has been successfully performed by assisting the procedure with ultrasound energy (35 kHz) supplied by an ultrasound water-bath. The use of pepsin, as a proteolytic enzyme, under optimized operating conditions (pH 3.0, temperature 40 °C, enzyme to sample ratio of 0.3) led to an efficient assistance of the enzymatic process in a short period of time (from 4.0 to 30 min). The enzymatic extract was then subjected to a clean-up procedure based on ENVI-Carb™ solid phase extraction (SPE). An optimized anion exchange high performance liquid chromatography (HPLC) coupled to inductively coupled plasma-mass spectrometry (ICP-MS) permitted the fast separation (less than 15 min) of six different arsenic species (arsenite, As(III); arsenate, As(V); dimethylarsinic acid, DMA; and arsenobetaine, AsB; as well as monomethylarsonic acid, MMA; and arsenocholine, AsC) in a single run. Relative standard deviations (n = 11) of the over-all procedure were 7% for AsB and DMA, 11% for As(III) and 9% for MMA. HPLC–ICP-MS determinations were performed using aqueous calibrations covering arsenic concentrations of 0, 5, 10, 25, 100 and 200 μg L⁻¹ (expressed as arsenic) for As(III), As(V), MMA, DMA and AsC; and 0, 125, 250, 500, 750, 1000 and 2000 μg L⁻¹ (expressed as arsenic) for AsB. Germanium (5 μg L⁻¹) was used as an internal standard. Analytical recoveries from the anion exchange column varied from 96 to 105% (enzymatic digests spiked with low target concentrations), from 97 to 104% (enzymatic digests spiked with intermediate target concentrations), and from 98 to 103% (enzymatic digests spiked with high target concentrations). The developed method was successfully applied to two certified reference materials (CRMs), DORM-2 and BCR 627, which offer certified AsB and DMA contents, and also to different seafood samples (mollusks, white fish and cold water fish). Good agreement between certified and found AsB concentrations was achieved when analyzing both CRMs; and also, between certified and found DMA concentrations in BCR 627. In addition, the sum of the different arsenic species concentrations found in most of the analyzed samples was statistically similar to the assessed total arsenic concentrations after a total sample matrix decomposition treatment.     

Determination of geosmin and 2-methylisoborneol in water and wine samples by ultrasound-assisted dispersive liquid-liquid microextraction coupled to gas chromatography-mass spectrometry

A fast, simple and environmentally friendly ultrasound-assisted dispersive liquid–liquid microextraction (USADLLME) procedure has been developed to preconcentrate geosmin and 2-methylisoborneol (MIB) from water and wine samples prior to quantification by gas chromatography–mass spectrometry (GC–MS). A two-stage multivariate optimization approach was developed by means of a Plackett–Burman design for screening and selecting the significant variables involved in the USADLLME procedure, which was later optimized by means of a circumscribed central composite design. The optimum conditions were: solvent volume, 8 μL; solvent type: tetrachloroethylene; sample volume, 12 mL; centrifugation speed, 2300 rpm; extraction temperature 20 °C; extraction time, 3 min; and centrifugation time, 3 min. Under the optimized experimental conditions the method gave good levels of repeatability with coefficient of variation under 11% (n = 10). Limits of detection were 2 and 9 ng L⁻¹ for geosmin and MIB, respectively. Calculated calibration curves gave high levels of linearity with correlation coefficient values of 0.9988 and 0.9994 for geosmin and MIB, respectively. Finally, the proposed method was applied to the analysis of two water (reservoir and tap) samples and three wine (red, rose and white) samples. The samples were previously analyzed and confirmed free of target analytes. Recovery values ranged between 70 and 113% at two spiking levels (0.25 μg L⁻¹ and 30 ng L⁻¹) showing that the matrix had a negligible effect upon extraction. Only red wine showed a noticeable matrix effect (70–72% recovery). Similar conclusions have been obtained from an uncertainty budget evaluation study.     

Bio-oil production by flash pyrolysis of sugarcane residues and post treatments of the aqueous phase

The pyrolysis of three sugarcane residues (internal bagasse, external and whole plant) has been carried out in a pilot bubbling fluidized bed pyrolyzer operating under a range of temperature from 300 °C to 600 °C and two vapor residence time (2 and 5 s), with the aim of determining their pyrolysis behavior including products yields and heat balance. The composition of the product gases was determined, from which their heating value was calculated. The liquid bio-oil was recovered with cyclonic condensers and separated into two phases, an aqueous phase and an organic phase. The energy content of the organic phase was determined in comparison with common fossil fuels. Activated carbon adsorption and distillation at 110 °C were used to treat the aqueous phase, with the aim of recovering valuable hydrocarbons and purifying the aqueous phase for wastewater disposal. Furthermore, the thermal sustainability of the pyrolysis process was estimated by considering the energy contribution of the product gases and of the liquid bio-oil in relation to the pyrolysis heat requirements. The optimum pyrolysis temperatures were identified in terms of maximizing the liquid yield, maximizing the energy from the product bio-oil, and maximizing the net energy from the product bio-oil after ensuring a self-sustainable process by utilizing the product gases and part of bio-oil as heat sources.     

Simultaneous pressurized liquid extraction and clean-up for the analysis of polybrominated biphenyls by gas chromatography-tandem mass spectrometry

This paper describes a fast and simple pressurized liquid extraction (PLE) method combined with gas chromatography coupled to ion trap tandem mass spectrometry (GC-ITMS-MS) for the determination of polybrominated biphenyls (PBBs) in fish samples. The method is based on a simultaneous extraction/clean-up step to reduce analysis time and solvent consumption. The effect of several PLE operating conditions, such as solvent type, extraction temperature and time, number of cycles, and lipid retainer, was optimized to obtain maximum recovery of the analytes with the minimum presence of matrix-interfering compounds. The best conditions were obtained at 100 °C with n-hexane using 15 g of silica modified with sulphuric acid (44%, w/w) as sorbent for lipid removal. Quality parameters of the GC-ITMS-MS method were established, achieving good linearity (r > 0.998), between 1 and 500 ng ml⁻¹, and low instrumental limits of detection (0.14-0.76 pg injected). For the whole method, limits of detection ranging from 0.03 to 0.16 ng g⁻¹ wet weight and good precision (RSD < 16%) were obtained.     

Samarium (III) adsorption on bentonite modified with N-(2-hydroxyethyl) ethylenediamine

A new material has been synthesized using dry process to activate bentonite followed by N-(2-hydroxyethyl) ethylenediamine connecting chlorosilane coupling agent. The synthesized new material was characterized by elemental analysis, FT-IR and thermogravimetry which proved that bentonite was successfully modified. The most interesting trait of the new material was its selective adsorption for rare earth elements. A variety of conditions of the new material were investigated for adsorption. The optimal conditions were determined with respect to pH and shaking time. Samarium (Sm) was quantitatively adsorbed at pH 4 and shaking time of 2 min onto the new material. Under these conditions the maximum static adsorption capacity of Sm(III) was found to be 17.7 mg g⁻¹. The adsorbed Sm(III) ion were quantitatively eluted by 2.0 mL 0.1 mol L⁻¹ HCl and 5% CS (NH₂)₂ solution. According to IUPAC definition, the detection limit (3σ) of this method was 0.60 ng mL⁻¹. The relative standard deviation (RSD) under optimum conditions was less than 3% (n = 8). The new material also was applied for the preconcentration of trace Sm(III) in environmental samples with satisfactory results.     

Characterization of a 2.6 μm Kinetex porous shell hydrophilic interaction liquid chromatography column in supercritical fluid chromatography with a comparison to 3 μm totally porous silica

The first systematic study of the performance of a porous shell, hydrophylic interaction liquid chromatography (HILIC) column in supercritical fluid chromatography (SFC) is presented. Observed efficiency on 2.6-μm porous shell particles exceeded all reports using UHPLC on 100-mm long columns packed with <2-μm totally porous particles. A Kinetex 4.6 × 150 mm, 2.6 μm HILIC column significantly outperformed a 3 μm Luna totally porous silica of the same length and diameter. A 17 component, low molecular weight test mix, consisting of a range of small drug-like molecules was separated isocratically on each column, with similar selectivity, but the porous shell column required ½ the time (≈2 min vs. 4 min), with almost 50% higher efficiency. Even little retained compounds (k < 0.5) exhibited more than 30,000 plates under some conditions. Reduced plate heights were higher than previously reported on porous shell particles in both HILIC and rHPLC, with the lowest value of 1.62. Significant fronting was sometimes observed. The cause of the fronting was not determined. The least symmetrical peaks showed the highest apparent efficiency. Pressure drop at optimum velocity (2.5 ml/min) and low modifier concentrations was <60 bar, and only exceeded 250 bar at near double optimum flow and 65% modifier. Peak widths were mostly just over 0.01 min (20 Hz) wide. There was a loss of efficiency when the injection volume was increased. The chromatograph was shown to have extremely low extra-column dispersion, on the order of 5–10 μL², which is also the lowest reported in an SFC, in spite of using standard components. This is likely due to turbulent flow in the tubing and fittings.     

A continuous DC-insulator dielectrophoretic sorter of microparticles

A lab-on-a-chip device is described for continuous sorting of fluorescent polystyrene microparticles utilizing direct current insulating dielectrophoresis (DC-iDEP) at lower voltages than previously reported. Particles were sorted by combining electrokinetics and dielectrophoresis in a 250 μm wide PDMS microchannel containing a rectangular insulating obstacle and four outlet channels. The DC-iDEP particle flow behaviors were investigated with 3.18, 6.20 and 10 μm fluorescent polystyrene particles which experience negative DEP forces depending on particle size, DC electric field magnitude and medium conductivity. Due to negative DEP effects, particles are deflected into different outlet streams as they pass the region of high electric field density around the obstacle. Particles suspended in dextrose added phosphate buffer saline (PBS) at conductivities ranging from 0.50 to 8.50 mS/cm at pH 7.0 were compared at 6.85 and 17.1 V/cm. Simulations of electrokinetic and dielectrophoretic forces were conducted with COMSOL Multiphysics^® to predict particle pathlines. Experimental and simulation results show the effect of medium and voltage operating conditions on particle sorting. Further, smaller particles experience smaller iDEP forces and are more susceptible to competing nonlinear electrostatic effects, whereas larger particles experience greater iDEP forces and prefer channels 1 and 2. This work demonstrates that 6.20 and 10 μm particles can be independently sorted into specific outlet streams by tuning medium conductivity even at low operating voltages. This work is an essential step forward in employing DC-iDEP for multiparticle sorting in a continuous flow, multiple outlet lab-on-a-chip device.     

Kinetics of tetrabromobisphenol A pyrolysis. Comparison between correlation and mechanistic models

Brominated flame retardants are well recognized as being highly effective flame retardants. 4-4′-Isopropylidenebis(2,6-dibromophenol), commonly known as tetrabromobisphenol A, is the brominated flame retardant with the largest production volume and is used to improve fire safety, mainly of laminates in electrical and electronic equipment. A kinetic study of the pyrolysis of TBBA has been carried out to obtain decomposition parameters under different operating conditions and taking into account that TBBA is a compound with a high boiling point and that vaporization occurs simultaneously to decomposition. Dynamic runs and dynamic + isothermal run at different heating rates and using different masses of sample were correlated simultaneously. All TG runs were fitted with a unique set of kinetic parameters that is able to explain all the experiments. Moreover, a simplified detailed kinetic model has been developed and the kinetic parameters obtained satisfactorily reproduce the thermal decomposition of TBBA.     

Enantiomeric resolution of (±)-licarin A by high-performance liquid-chromatography using a chiral stationary phase

(±)-Licarin A (1), a neolignan obtained by the oxidative coupling reaction of isoeugenol, had in this study its enantiomers resolved. A novel, quick and efficient enantiomeric resolution of 1 was directly performed by chiral high-performance liquid chromatography (HPLC-PDA) protocol (CHIRALPACK^® AD column; 9:1 (v/v) n-hexane:2-propanol; 1.0 mL/min). This method provided a chromatogram profile with a well-resolved peak separation. After isolation of each enantiomer with ee > 99.9%, they were analysed in a polarimeter. Compound 2, which showed a retention time (t_r) of 12.13 min, was the (+)-enantiomer and compound 3 (t_r = 18.90 min) was the (−)-enantiomer.     

Headspace stir bar sorptive extraction-gas chromatography/mass spectrometry characterization of the diluted vapor phase of cigarette smoke delivered to an in vitro cell exposure chamber

Advanced smoke generation systems, such as the Borgwaldt RM20S^® smoking machine used in combination with the BAT exposure chamber, allow for the generation, dilution and delivery of fresh cigarette smoke to cell or tissue cultures for in vitro cell culture analyses. Recently, our group confirmed that the Borgwaldt RM20S^® is a reliable tool to generate and deliver repeatable and reproducible exposure concentrations of whole smoke to in vitro cultures [1]. However, the relationship between dose and diluted smoke components found within the exposure chamber has not been characterized. The current study focused on the development of a headspace stir bar sorptive extraction (HSSE) method to chemically characterize some of the vapor phase components of cigarette smoke generated by the Borgwaldt RM20S^® and collected within a cell culture exposure chamber. The method was based on passive sampling within the chamber by HSSE using a Twister™ stir bar. Following exposure, sorbed analytes were recovered using a thermal desorption unit and a cooled injection system coupled to gas chromatograph/mass spectrometry for identification and quantification. Using the HSSE method, sixteen compounds were identified. The desorption parameters were assessed using ten reference compounds and the following conditions led to the maximal response: desorption temperature of 200 °C for 2 min with cryofocussing temperature of −75 °C. During transfer of the stir bars to the thermal desorption system, significant losses of analytes were observed as a function of time; therefore, the exposure-to-desorption time interval was kept at the minimum of 10 ± 0.5 min. Repeatability of the HSSE method was assessed by monitoring five reference compounds present in the vapor phase (10.1–12.9% RSD) and n-butyl acetate, the internal standard (18.5% RSD). The smoke dilution precision was found to be 17.2, 6.2 and 11.7% RSD for exposure concentrations of 1, 2 and 5% (v/v) cigarette vapor phase in air, respectively. A linear response of analyte abundance was observed as a function of dilution. Extrapolation to 100% (v/v) cigarette vapor phase, i.e., undiluted smoke, gave yields for the five compounds ranging from 6 to 450 ng for 10 min exposure.     

Thermal self-sustainability of biochar production by pyrolysis

The pyrolysis of several agricultural and biofuel production residues (grape residues, sugarcane residues, dried distiller's grain, palm oil residues, apple pomace and forestry residue) has been carried out in a pilot bubbling fluidized bed pyrolyzer operating under a range of temperature from 300 to 600 °C and two vapor residence times (2 and 5 s), with the aim of determining their pyrolysis behavior including products yields and heat balance. The composition of the product gases was determined, from which their heating value was calculated. The liquid bio-oil was recovered with cyclonic condensers. The thermal sustainability of the pyrolysis process was estimated by considering the energy contribution of the product gases and of the liquid bio-oil in relation to the pyrolysis heat requirements. The most promising biomass feedstocks for the sustainable production of biochar were indentified. Furthermore, this study presented the char yield in relation to the excess heat that could be obtained by combusting the gas and bio-oil coproducts of biochar production, as functions of pyrolysis temperature and vapor residence time.     

Determination of selenium in biological samples by slurry sampling-electrothermal vaporization-in situ fusion-isotope dilution-microwave-induced nitrogen plasma mass spectrometry

Determination of selenium in certified reference biological materials by slurry sampling electrothermal vaporization (ETV)-isotope dilution (ID)-microwave-induced nitrogen plasma mass spectrometry (MIP-MS) was performed. Several parameters such as the heating conditions were studied in order to obtain optimal conditions. A special heating stage called the in situ fusion stage was applied just before the pyrolysis stage in the electrothermal vaporization process in order to fuse the biological sample and to achieve selenium isotope-equilibration between selenium in the sample and the ⁷⁸Se spike solution. The slurry sample containing an appropriate amount of biological sample, ⁷⁸Se spike solution, and sodium hydroxide as an alkaline flux was injected into the electrothermal vaporization unit. The slurry sample was in situ fused, pyrolyzed, and then vaporized. The ion counts at m/z=78 and 80, the spike and reference isotopes, respectively, could be measured accurately without interference caused by argon since nitrogen plasma was used. The analytical utility of the proposed slurry sampling-electrothermal vaporization-in situ fusion-microwave-induced nitrogen plasma mass spectrometry was evaluated by determining the selenium concentration in certified reference biological materials, and the analytical results obtained were in good agreement with the certified values. The limit of detection for selenium was 90 ng g⁻¹. The relative standard deviation of the determination of selenium was 8–15% with a high sample throughput (less than 30 min per sample including a slurry preparation.)     

A modified supported bilayer/diblock polymer--working towards a tunable coating for capillary electrophoresis

A surfactant bilayer/diblock polymer coating was previously developed for the separation of proteins. The coating consisted of a mixture of the cationic surfactant dioctadecyldimethylammonium bromide (DODAB) and the neutral polymer poly-oxyethylene (POE) 40 stearate (Journal of Chromatography A 1130 (2006) 265–271). Herein an improved method of generating DODAB/POE stearate coatings is demonstrated, which yields more predictable EOF, more stable coatings, greater average efficiencies and easier method development. In this sequential preparation method the DODAB is first flowed through the capillary, followed by a flow of the POE stearate (sequential method). A tunable EOF (−2.40 to −0.17 × 10⁻⁴ cm²/Vs) is achieved by varying the POE chain length (8, 40 and 100 oxyethylene units). Mixtures of POE 8 and POE 40 stearate enabled continuous variation in EOF from −2.44 to −0.42 × 10⁻⁴ cm²/Vs. Separations of basic proteins yielded efficiencies of 760 000–940 000 plates/m. Coatings formed using the sequential method were more stable over a larger number of runs (%RSD for migration times: 0.7–1.0% over 30 runs) than those formed using the original mixed method (%RSD: 2.4–4.6% over 14 runs). The ability to tune the EOF is important in maximizing the resolution of analytes with similar electrophoretic mobilities. Histone proteins are separated on a sequentially coated capillary with resolution of nine possible subtypes. Acidic proteins are separated on a sequentially coated capillary at pH 6.4.