Significance of fatigue for mechanical defibration

The fatigue induced by high-frequency cyclic loading on the compressibility and tensile properties of wood and wood cell walls was quantified. The non-elastic behavior of fatigued and reference samples was similar, whereas their elastic behavior differed, as expected. Next, the effects of the dynamic fatigue on the mechanical pulping process were quantified by grinding fatigued and untreated samples and by comparing the paper strength produced by the two pulps against the consumed pulping energy. Pre-introducing fatigue increased the energy efficiency of grinding and may allow designing a more energy efficient mechanical pulping process.     

Distillation, on-line RP C18 preconcentration and HPLC-UV-PCO-CVAAS as a new combination for the determination of methylmercury in sediments and fish tissue

Distillation as a way of sample digestion has been combined with on-line RP C18 preconcentration and HPLC-UV-PCO-CVAAS (high performance liquid chromatography — ultra violet — post column oxidation — cold vapour atomic absorption spectrometry) for the determination of methylmercury at back-ground levels in sediments, soils and fish tissue. To prove the accuracy of this method, it was applied to sediment and fish tissue reference materials. The results correspond with the reference values within their error ranges. Excellent recoveries (92–95%) were obtained for the sediment samples by means of the standard addition method. The standard deviations of the sediment samples were within an acceptable range (7.2–12.5%), those of the fish samples were substantially lower (3.4–5.0%). The detection limit is 0.04 ng/g for 1 g sample weight.     

Use of NMR metabolomic plasma profiling methodologies to identify illicit growth-promoting administrations

Detection of growth-promoter use in animal production systems still proves to be an analytical challenge despite years of activity in the field. This study reports on the capability of NMR metabolomic profiling techniques to discriminate between plasma samples obtained from cattle treated with different groups of growth-promoting hormones (dexamethasone, prednisolone, oestradiol) based on recorded metabolite profiles. Two methods of NMR analysis were investigated—a Carr–Purcell–Meiboom–Gill (CPMG)-pulse sequence technique and a conventional ¹H NMR method using pre-extracted plasma. Using the CPMG method, 17 distinct metabolites could be identified from the spectra. ¹H NMR analysis of extracted plasma facilitated identification of 23 metabolites—six more than the alternative method and all within the aromatic region. Multivariate statistical analysis of acquired data from both forms of NMR analysis separated the plasma metabolite profiles into distinct sample cluster sets representative of the different animal study groups. Samples from both sets of corticosteroid-treated animals—dexamethasone and prednisolone—were found to be clustered relatively closely and had similar alterations to identified metabolite panels. Distinctive metabolite profiles, different from those observed within plasma from corticosteroid-treated animal plasma, were observed in oestradiol-treated animals and samples from these animals formed a cluster spatially isolated from control animal plasma samples. These findings suggest the potential use of NMR methodologies of plasma metabolite analysis as a high-throughput screening technique to aid detection of growth promoter use.     

Amorphous sol-gel titania modified with heteropolyacids

Samples of amorphous sol-gel titania were prepared at 50%wt with tungstophosphoric or molybdophosphoric acid. The resulting gels were dried and annealed at 100, 150 and 200°C and studied by FT-IR, UV-Vis, EPR, TGA and Raman spectroscopy. By FT-IR the evolution of the stretching vibration of the OH groups (3450–3700 cm⁻¹) was followed. The intensity of this band decreased as the annealing temperature increased. With UV-Vis spectroscopy the band gap was determined for each sample, and the Eg was found between 2.72 and 3.38 eV. Raman spectroscopy revealed the formation of Mo—O—Ti and W—O—Ti—O bonds. An intense EPR signal at g = 1.998 was observed during annealing of the samples. Amorphous solids with a significant number of vacancies and promising photocatalytic properties were obtained.     

Capillary array isoelectric focusing with laser-induced fluorescence detection: milli-pH unit resolution and yoctomole mass detection limits in a 32-channel system

We report a multiplexed capillary electrophoresis system employing an array of 32 capillaries with a micromachined sheath-flow cuvette as the detection chamber. The sample streams were simultaneously excited with a 473-nm laser beam, and the fluorescence emission was imaged on a CCD camera with a pair of doublet achromat lens. The instrument produced mass detection limits of 380 ± 120 yoctomoles for fluorescein in zone electrophoresis. Capillary isoelectric focusing of fluorescent standards produced peaks with an average width of 0.0029 ± 0.0008 pH. Capillary coating stability limits the reproducibility of the analysis.     

Immobilization of xanthine oxidase and its use in the quantitation of hypoxanthine in fish muscle tissue extracts using a flow injection method

Fish muscle extracts (Scomberomorus— brasiliensis- carite) were analyzed for their hypoxanthine content using a flow injection system incorporating an immobilized xanthine oxidase bioreactor. The xanthine oxidase was immobilized under mild conditions to a 2-fluoro-1-methylpyridinium Fractogel support. The uric acid produced from the oxidation of hypoxanthine by the immobilized xanthine oxidase at pH 7.0 and 35‡C was monitored at 290 ran. Hypoxanthine concentrations as low as 4.4 Μmol/L can be detected. Up to 30 samples per hour can be analyzed at a flow rate of 1 mL/min, using 150 ΜL sample volumes and a bioreactor dimension of 1.0 cm x 2.0 mm id. Recovery yields were between 92 and 99%. Both within day and between day precisions gave CVs < 5.00% (n = 30). Good correlation (r = 0.998) is obtained when 78 fish samples were analyzed for their hypoxanthine content both by this FI method and a reference HPLC method.     

Determination of 11 priority pollutant phenols in wastewater using dispersive liquid—liquid microextraction followed by high-performance liquid chromatography—diode-array detection

Dispersive liquid—liquid microextraction coupled with high-performance liquid chromatography—diode-array detection was applied for the extraction and determination of 11 priority pollutant phenols in wastewater samples. The analytes were extracted from a 5-mL sample solution using a mixture of carbon disulfide as the extraction solvent and acetone as the dispersive solvent. After extraction, solvent exchange was carried out by evaporating the solvent and then reconstituting the residue in a mixture of methanol–water (30:70). The influences of different experimental dispersive liquid—liquid microextraction parameters such as extraction solvent type, dispersive solvent type, extraction and dispersive solvent volume, salt addition, and pH were studied. Under optimal conditions, namely pH 2, 165-μL extraction solvent volume, 2.50-mL dispersive solvent volume, and no salt addition, enrichment factors and limits of detection ranged over 30–373 and 0.01–1.3 μg/L, respectively. The relative standard deviation for spiked wastewater samples at 10 μg/L of each phenol ranged between 4.3 and 19.3% (n = 5). The relative recovery for wastewater samples at a spiked level of 10 μg/L varied from 65.5 to 108.3%.     

Using bamboo charcoal as solid-phase extraction adsorbent for the ultratrace-level determination of perfluorooctanoic acid in water samples by high-performance liquid chromatography–mass spectrometry

In recent years, bamboo charcoal, a new kind of material with special microporous and biological characteristics, has attracted great attention in many application fields. In this paper, the potential of bamboo charcoal to act as a solid-phase extraction (SPE) adsorbent for the enrichment of the environmental pollutant perfluorooctanoic acid, which is one of the newest types of persistent organic pollutants in the environment, has been investigated. Important factors that may influence the enrichment efficiency—such as the eluent and its volume, the flow rate of the sample, the pH of the sample and the sample volume—were investigated and optimized in detail. Under the optimum conditions, the limit of detection for PFOA was 0.2 ng L⁻¹. The experimental results indicated that this approach gives good linearity (R ² = 0.9995) over the range 1–1000 ng L⁻¹ and good reproducibility, with a relative standard deviation of 4.0% (n = 5). The proposed method has been applied to the analysis of real water samples, and satisfactory results were obtained. The average spiked recoveries were in the range 79.5∼118.3 %. All of the results indicate that the proposed method could be used for the determination of PFOA at ultratrace levels in water samples.     

Automated liner exchange— A novel approach in direct thermal desorption— gas chromatography

Summary A system was developed for fully automated liner exchange in direct thermal desorption— gas chromatography— mass spectrometry (DTD-GC-MS). Samples are put into a newly developed liner which is capped with a standard crimp cap. The liners are placed in a sample tray and transported to the thermal desorption device. Both liner transport and liner exchange (which can be performed after each analysis) are automated. The system was tested for spores and pollen, vegetable oil, wood (preservative), car exhaust (BTEX), and tobacco (nicotine) analysis to demonstrate the robustness and flexibility of the approach.     

Determination of selected elements by X-ray fluorescence spectrometry in liquid drug samples after the preconcentration with thioacetamide

Preconcentration performance characteristics of precipitation of Mn, Fe, Co, Cu, Zn, Pb, Hg, and Cd and with subsequent filtration through cellulose nitrate membrane were investigated for the X-ray spectrometry identification and determination of trace metal ions in drug samples. The method was optimised for several parameters, including pH and amount of thioacetamide. The investigated analyte ions were collected on cellulose nitrate membrane filter (Pragopor 4) as sulphides after the reaction with thioacetamide. Optimal reaction conditions were found out (pH 8.5 for Fe, Zn, Hg, and Cd and pH 11.5 for Mn, Co, Cu, and Pb; 1.2 mL of added thioacetamide). Thereafter, the content of these elements was determined in the samples of drugs—NaCl, glucose and dextrane. The rapidity of this method, its polycomponent character and low detection limits (for filters: Mn—1.09 μg, Fe—1.08 μg, Co—0.82 μg, Cu—0.42 μg, Zn—0.61 μg, Pb—0.45 μg, Hg—0.42 μg, and Cd—0.99 μg) have proved this method to be very promising in rapid screening used in quality control of drugs.     

Industrial Sustainability of Competing Wood Energy Options in Canada

The amount of sawmill residue available in Canada to support the emerging cellulosic ethanol industry was examined. A material flow analysis technique was employed to determine the amount of sawmill residue that could possibly be available to the ethanol industry per annum. A combination of two key trends—improved efficiency of lumber recovery and increased uptake of sawmill residues for self-generation and for wood pellet production—have contributed to a declining trend of sawmill residue availability. Approximately 2.3 × 10⁶ bone-dry tonnes per year of sawmill residue was estimated to be potentially available to the cellulosic ethanol industry in Canada, yielding 350 million liters per year of cellulosic ethanol using best practices. An additional 2.7 billion liters of cellulosic ethanol might be generated from sawmill residue that is currently used for competing wood energy purposes, including wood pellet generation. Continued competition between bioenergy options will reduce the industrial sustainability of the forest industry. Recommendations for policy reforms towards improved industrial sustainability practices are provided.     

Mechanism of the evaporation of particles of powder test materials in the discharge of a two-jet argon arc plasmatron

The mechanism of the evaporation and formation of an analytical signal upon the injection of an analyzed powder into the plasma jet of a two-jet argon arc plasmatron is studied. The strong dependence of the integral intensity of the spectral lines and the degree of particle evaporation on the dispersity of the introduced material is observed. The completeness of evaporation and the maximum intensity of the analytical signal are attained for particle sizes of the order 0.005–0.025 mm, depending on their structure, chemical composition, and the element to be determined. Larger particles leave the excitation zone being only partially evaporated, i.e., having lost only part of their weight. Different degrees of element atomization from particles of different sizes result in the appearance systematic errors of analysis. It is shown that fine grinding of the powders to the sizes ≤0.025 mm ensures the complete atomization of the impurity elements from the sample particles and ensures the accuracy of the results of analysis.     

Analysis of acidic photosystem II—Interacting herbicides in lake and river water by capillary electrophoresis

Summary The separation of cyanophenolic (ioxynil and bromoxynil) photosystem II-interacting herbicides and mecoprop in surface water extracts was obtained on a poly(vinyl alcohol)—coated capillary in 75 mM acetate buffer, pH 6, at 16 kV applied voltage. Styrene-divinyl benzene packed cartridges were used for solid phase extraction of the real surface water samples at neutral pH. To increase method sensitivity different injection techniques, namely hydrodynamic, electrophoretic and field—amplified sample injection (FASI), were compared.     

Application of artificial neural networks to the nondestructive determination of ciprofloxacin hydrochloride in powder by short-wavelength NIR spectroscopy

The present study is aimed at providing a new short-wavelength near-infrared (NIR) spectroscopic method for the nondestructive quantitative analysis of ciprofloxacin hydrochloride in powder via artificial neural networks (ANNs). For this purpose, the NIR spectra of 90 experimental powder samples in the range 700–1100 mm were analyzed. Four different pretreatment methods—first-derivative, second-derivative, standard normal variate (SNV), and multiplicative scatter correction (MSC)—were applied to three sets of the NIR spectra of the powder samples. Among all of the ANN models, the first-derivative model is found to be the best. The results presented here demonstrate that the short-wavelength NIR region is promising for the fast and reliable determination of the major components in pharmaceuticals. The degree of approximation as an evaluation criterion prevents the overfitting phenomenon occurring in ANNs. The text was submitted by the authors in English.     

Determination of inorganic oxyhalides in drinking water by on-line coupled capillary isotachophoresis— capillary zone electrophoresis

Some oxyhalides can be found in drinking waters as inorganic disinfection byproducts. An on-line coupled capillary isotachophoresis—capillary zone electrophoresis (CITP-CZE) method was developed for the analysis of chlorate, chlorite and bromate in water. The optimized CITP-CZE electrolyte system consisted of the following: 10 mM—HCl+20 mM—β-Alanine (leading electrolyte), 5 mM—succinic acid (terminating electrolyte), and 10 mM—succinic acid +5 mM—β-Alanine +0.1% HPMC (carrier electrolyte). A clear separation of oxyhalides from other components of drinking water was achieved within 25 min. Method characteristics, i.e., linearity (0–200 ng/mL), accuracy (88–110%), intra-assay (3–5%), quantification limit (5–15 ng/mL), and detection limit (2–5 ng/mL), were determined. Minimum labor requirements, sufficient sensitivity and low running cost are important attributes of this method. It was found that the developed method is useful for the routine analysis of oxyhalides in water.     

关于澳洲GoLden Grove金精矿磨样方法的研究

金精矿样品的粒度,直接影响金精矿中金含量测定的精密度和稳定性,本文通过对Golden Grove金精矿采用不同的磨样工具和磨样时间,得到不同粒度的样品,对不同样品进行了金含量的测定,并对测定结果的精密度进行了分析。其中磨样方式：滚筒磨样机、磨样时间为5h、磨样粒度为0.040mm(360目)95%以上的B样品,测定精密度最好。C样品测定精密度相对较差,反映出振动粉碎机磨样均匀度相对较差。     

Application of microextraction by packed sorbent to isolation of psychotropic drugs from human serum

A method of microextraction by packed sorbent (MEPS) followed by liquid chromatography with diode array detection has been developed and optimized for the extraction of six tricyclic antidepressants (amitriptyline, nortriptyline, imipramine, desipramine, doxepin, nordoxepin) from human serum. The optimal parameters of MEPS extraction (type of sorbent, volume of sample, composition, and volume of washing and elution solutions) for these drugs in spiked samples were defined. The developed MEPS procedure was validated and then successfully applied to the analysis of serum reference material. The limit of detection (0.02–0.05 μg/mL), intraday (2.7–8.8%) and interday (4.4–11.6%) precision (RSD), and the accuracy of the assay (94.5–108.8%) at three concentration levels—0.2, 0.5, and 0.8 μg/mL—were estimated. The accuracy of the method was evaluated by the analysis of certified reference material. Moreover, the validated procedure was compared with the solid-phase extraction technique. Finally, microextraction by packed sorbent was assessed as a suitable tool in forensic and clinical methods for serum sample preparations.     

Radioactive labeling in the study of abrasion of hard tooth tissue

Labeling the surface of hard tooth tissue samples by the nuclear recoil effect in radioactive decay was applied to study abrasion caused by abrasive components of tooth-pastes.²²²Rn and its short-lived decay products were implanted into the surface in vacuum. For this purpose irradiation was applied to sample placed very close to thin²²⁶Ra source. Measuring the activity before and after abrasion was used to evaluate abrasion in the system toothbrush — various suspensions of the tooth-pastes — hard tooth tissue (enamel or dentine) in a specially designed device, dentoabrasionmeter VUS 2.     

Direct sample injection for capillary electrophoretic determination of organic acids in cerebrospinal fluid

Organic acids in cerebrospinal fluid (CSF) are potential diagnostic markers for neurological diseases and metabolic disorders. A capillary electrophoretic (CE) method for the direct analysis, i.e., without any sample preparation, of six organic acids in CSF was developed. A capillary coating consisting of a triple layer of charged polymers (polybrene-dextran sulfate-polybrene) was used in combination with a negative separation voltage, providing fast and efficient analysis of acidic compounds. Separation conditions, such as background electrolyte (BGE) concentration and pH were optimized, and the influence of albumin and sodium chloride was systematically studied using a set of test compounds. With injection volumes of ca. 44 nL, plate numbers of up to ca. 150,000 were obtained with a BGE of 200 mM sodium phosphate (pH 6.0). It appeared that high sodium chloride concentrations in the sample hardly affected the peak width and shape of the organic acids, most probably due to transient isotachophoresis effects occurring in the sample zone. Adverse effects of CSF proteins, which frequently compromise the CE performance, could be effectively minimized by the triple layer coating in combination with rinses of 0.1 M hydrochloric acid. Overall, the developed CE system allowed direct injections of CSF samples, yielding good separation efficiencies and stable migration times (RSDs < 2%) for organic acids. Validation of the method with artificial and real CSF samples showed good linear responses (r > 0.99), and LODs for the organic acids were in the range of 2–8 μg/mL when applying UV detection. RSDs for migration times and peak areas were <2% and <7%, respectively. The applicability of the CE system is shown for the determination of organic acids in CSF samples.