Sample evaporation in conventional split/splitless GC injectors. Part 3: Retaining the liquid in the vaporizing chamber

As most sample liquids tend to pass through an empty injector insert at a speed which is too high to enable complete evaporation, movement of the liquid must be arrested before it reaches the column entrance. Stopping the liquid means deposition on to a surface; this, however, is possible only after the temperature of the surface has been cooled to (or below) the boiling point of the liquid (solvent). The performance of different means of stopping the liquid has been tested visually (by the method described in Part 2). Baffles on the wall of the injector insert had hardly any effect on evaporation: the band of liquid leaving the syringe needle performed a perfect slalorn around them. The inverted cup proved more efficient, but the best performance was obtained from a light plug of glass wool: owing to its low thermal mass, the first fibers to be met by the liquid are immediately cooled to the solvent boiling point, allowing the liquid to wet it. The sample liquid is sucked up by the glass wool, from where the sample evaporates relatively slowly, often over a period of several seconds.     

Study on methane fermentation and production of vitamin B12 from alcohol waste slurry

We studied biogas fermentation from alcohol waste fluid to evaluate the anaerobic digestion process and the production of vitamin B₁₂ as a byproduct. Anaerobic digestion using acclimated methanogens was performed using the continuously stirred tank reactor (CSTR) and fixed-bed reactor packed with rock wool as carrier material at 55°C. We also studied the effects of metal ions added to the culture broth on methane and vitamin B₁₂ formation. Vitamin B₁₂ production was 2.92 mg/L in the broth of the fixed-bed reactor, twice that of the CSTR. The optimum concentrations of trace metal ions added to the culture liquid for methane and vitamin B₁₂ production were 1.0 and 8 mL/L for the CSTR and fixed-bed reactor, respectively. Furthermore, an effective method for extracting and purifying vitamin B₁₂ from digested fluid was developed.     

The way to measure quantitatively full dissolution and crystallization of polyamides in water up to 200 °C and above by DSC

The way to measure quantitatively full dissolution and crystallization of polyamides in water up to 200 °C and above by DSC is described. Stainless-steel high-pressure pans enable research on fully dissolving polyamides in water under vapor pressure. The results show clearly that polyamide 6 (PA6) is soluble in water under vapor pressure in the whole concentration range and that water acts as a crystallization and melting point suppressor. The maximum temperature depression is approximately 60 °C. This depression of the transitions is independent of concentration over a large range (10-70 mass% PA6 in water). When PA6 dissolves in water during heating, the polymer often sets to the sides of the DSC sample pan. Because of this the contact between the sample and the bottom of the pan reduces during measurement and therefore DSC heating curves are frequently curved. Adding steel wool to these stainless-steel high-pressure pans improves the measurements by increasing the thermal conductivity between the sample and pan bottom, and as a result the DSC curves become less curved. The interpretation of the measurements improves and the possibility of reproducible peak area calculations also in heating comes in sight.     

Influence of the surface morphology on the melting of polymer crystals. I. Loops of random length and adjacent reentry

A polymer crystal with a noncrystalline surface layer formed by chain loops of different lengths is considered. It is assumed that the length of each loop can be changed by longitudinal diffusion of the molecule through the crystal lattice. From the condition that the free energy of the system is minimum, the loop length distribution and the average loop length as function of temperature are calculated. In contrast to the results for loops of equal length, for the present model, a substantial thickness of the noncrystalline surface layer and a broad melting range is obtained also for the case of adjacent reentry. In order to get this result one has to take into account that even an “ideal fold” consists of at least four rigidly arranged CH2 groups in energetically unfavored conformation.     

Ferrite nanoparticles supported on natural wool in one‐pot tandem oxidative reactions: strategy to synthesize benzimidazole,quinazolinone and quinoxaline derivatives

Two tandem oxidative two‐component reactions (O‐2CRs) and Ugi‐type three‐component reactions (OU‐3CRs) of aromatic hydrocarbons of petroleum naphtha have been investigated for the synthesis of 2‐phenyl‐1H ‐benzo [d ]imidazole, 2‐aryl‐4‐quinazolinone and 3,4‐dihydroquinoxalin‐2‐amine derivatives using six new biopolymer‐supported ferrite nanocatalysts: CoFe₂O₄@wool‐SO₃H, MnFe₂O₄@wool‐SO₃H, ZnFe₂O₄@wool‐SO₃H, MnCoFe₂O₄@wool‐SO₃H, ZnCoFe₂O₄@wool‐SO₃H and CrCoFeO₄@wool‐SO₃H. The best results are obtained with the CrCoFeO₄@wool‐SO₃H catalyst. All of the catalysts were characterized using flame atomic absorption spectrometry, X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy and energy‐dispersive spectroscopy. To the best of our knowledge, this approach can be considered as the first example of O‐2CRs and OU‐3CRs of aromatic hydrocarbons of petroleum naphtha with ferrite nanocatalysts, which would be very useful from a practical point of view. Copyright © 2016 John Wiley & Sons, Ltd.     

Diffusion of moisture in deformable porous media. Anisotropic fibrous materials

This paper presents a study on the deformation of anisotropic fibrous porous media subjected to moistening by water in the liquid phase. The deformation of the medium is studied by applying the concept of effective stress. Given the structure of the medium, the displacement of the solid matrix is not taken into account with respect to the displacement of the liquid phase. The transport equations are derived from the model proposed by Narasimhan. The transport coefficients and the relation between the variation in apparent density and effective stress are obtained by test measurements. A numerical model has been established and applied for studying drip moistening of mineral wool samples capable or incapable of deformation.Nomenclature D mass diffusion coefficient [L²t^–1] - e void fraction - g gravity acceleration [Lt^–2] - J mass transfer density [ML^–2t^–1] - K hydraulic conductivity [Lt^–1] - K _s hydraulic conductivity of the solid phase [Lt^–1] - K ^* hydraulic conductivity of the deformable porous medium [Lt^–1] - P pressure of moistening liquid [ML^–1 t^–2] - S degree of saturation - t time [t] - V speed [Lt^–1] - X horizontal coordinate [L] - Z vertical coordinate measured from the bottom of porous medium [L] - z z-coordinate [L] Greek Letters porosity - ₁ total hydric potential [L] - _g gas density [ML^–3] - ₁ liquid density [ML^–3] - ₀ apparent density [ML^–3] - _s density of the solid phase [ML^–3] - density of the moist porous medium [ML^–3] - external load [ML^–1t^–2] - effective stress [ML^–1t^–2] - bishop's parameter - matrix potential or capillary suction [L] Indices g gas - 1 moistening liquid - p direction perpendicular to fiber planes - s solid matrix - t direction parallel to fiber planes - v pore Exponent * movement of solid particles taken into account     

Microextraction of Reseda luteola-Dyed Wool and Qualitative Analysis of Its Flavones by UHPLC-UV,NMR and MS

Detailed knowledge on natural dyes is important for agronomy and quality control as well as the fastness, stability, and analysis of dyed textiles. Weld (Reseda luteola L.), which is a source of flavone-based yellow dye, is the focus of this study. One aim was to reduce the required amount of dyed textile to ≤50 μg for a successful chromatographic analysis. The second aim was to unambiguously confirm the identity of all weld flavones. By carrying out the extraction of 50 μg dyed wool with 25 μL of solvent and analysis by reversed-phase UHPLC at 345 nm, reproducible chromatographic fingerprints could be obtained with good signal to noise ratios. Ten baseline separated peaks with relative areas ≥1% were separated in 6 min. Through repeated polyamide column chromatography and prepHPLC, the compounds corresponding with the fingerprint peaks were purified from dried weld. Each was unequivocally identified, including the position and configuration of attached sugars, by means of 1D and 2D NMR and high-resolution MS. Apigenin-4′-O-glucoside and luteolin-4′-O-glucoside were additionally identified as two trace flavones co-eluting with other flavone glucosides, the former for the first time in weld. The microextraction might be extended to other used dye plants, thus reducing the required amount of precious historical textiles.     

Design of electrospun polyacrylonitrile nanofiber–coated nonwoven structure for sound absorption

Acoustic felts are commonly used in white goods. Bearing that into mind, this paper aims to enhance sound absorption behavior of such felts, in particular, within the low and medium frequency ranges. In doing so, wool and jute felt samples were coated with electrospun polyacrylonitrile nanofibrous membrane. These nanocoated felts were studied in terms of their sound absorption performance, air permeability, and surface morphology. The results indicated that the air permeability of the felts could be drastically decreased by coating with nanofibers, which was required for better acoustic performance of felt‐like structures. Moreover, the samples having higher amount polyacrylonitrile nanofibers tended to demonstrate better sound absorbency.     

A Study of Adsorption of Water Vapour on Wool under Static and Dynamic Conditions

Adsorption of water vapour on wool provides not only textile comfort, but also convenience in transportation due to increase in its bulk density. The adsorption and desorption isotherms of water vapour for wool were determined by both volumetric technique using a Coulter Omnisorp 100CX instrument and gravimetric method employing a Cahn 2000 electronic microbalance. Adsorption isotherm fitting to B.E.T. model and hysteresis on desorption was observed. The average effective diffusion coefficient of water in wool was found to be 8.4 × 10^-14 m²s^-1 at 25°C from gravimetric data. The effects of packing height and air velocity on the breakthrough curves were also investigated in the wool packed columns. For pseudo first order model, k values changing between 0.33 × 10^-6 – 69 × 10^-6 s^-1 was obtained for 2.2–6.4 cm s^-1 air velocity and 0.05–0.20 m packing height ranges.     

气相色谱-柱后分流-反吹技术测定含脂羊毛中有机氯和有机磷类杀虫剂残留

建立了同时测定含脂羊毛中20种有机氯和有机磷类杀虫剂残留的气相色谱-柱后分流-反吹检测方法.通过二氧化碳超临界萃取技术提取含脂羊毛样品中的杀虫剂残留并经中性氧化铝固相萃取柱净化,采用气相色谱-柱后分流技术,可以同时得到3个检测器信号(MSD、μECD和NPD),可对两类杀虫剂准确定性和定量分析.同时运用反吹技术,减少样品中高沸点杂质对色谱系统的污染.3个添加水平的回收率为85.6%～120.9%,相对标准偏差在1.2%～17.3%之间.方法干扰小、重现性好、自动化程度高,能够对含脂羊毛中有机氯和有机磷类杀虫剂残留准确地定性定量分析.