Stability of collagen with polyols against guanidine denaturation

The effect of polyol osmolytes such as erythritol, xylitol and sorbitol on the protection of collagen against guanidine hydrochloride (GdmCl) was studied using circular dichroism and fluorescence spectroscopy. Collagen was denatured by various concentrations of GdmCl in the presence of polyols. The absorbance was high for GdmCl treated collagen than native and polyols treated analogue. Fluorescence emission properties were studied at the excitation wavelength of 235 nm. The emission wavelength is red shifted from 308 to 370 nm for GdmCl treated collagen with polyols. Increasing the concentration of GdmCl did not affect the peak position. CD studies proved that the aggregation of collagen in the presence of lower concentrations of GdmCl. At higher concentrations of GdmCl due to the loss of secondary structure no clear CD spectra were observed. This shows that the unfolding of collagen is closely related to GdmCl concentrations. The ability of the polyols to protect collagen against guanidine denaturation decreased in order from erythritol to xylitol to sorbitol. The presence of OH group in the solvent structure is important for stabilization of collagen due to the formation of additional stabilizing hydrogen bonds.     

Long-term heat stabilisation by (natural) polyols in heavy metal- and zinc-free poly(vinyl chloride)

The long-term heat stabilisation efficiency of (natural) polyol additives in heavy metal- and zinc-free poly(vinyl chloride) (PVC) has been investigated. It is shown that polyols, such as sorbitol and xylitol, markedly reduce the dehydrochlorination rate and improve Congo Red values. Extraction experiments on unprocessed and ground-processed PVC-sorbitol (1.0 phr) mixtures after thermal degradation at 200 °C revealed that especially in the ground-processed PVC-sorbitol system, sorbitol is partly converted into its mono- and dianhydro-derivatives 1,4-sorbitan and isosorbide, respectively. Apparently, the HCl released during thermal degradation acts as the catalyst. Similar intramolecular cyclodehydration reactions also occur with the natural polyols, erythritol and xylitol, under these conditions. Scrutiny of the measured dehydrochlorination rates and the Congo Red values for ground-processed heavy metal- and zinc-free PVC-polyol mixtures show that in particular polyols containing primary hydroxyl groups exert long-term heat stabilisation and that they act as efficient HCl scavengers.     

Determination of sugar alcohols in confectioneries by high-performance liquid chromatography after nitrobenzoylation

A method was developed for the determination of sugar alcohols, meso-erythritol, xylitol, D-glucitol, D-mannitol, maltitol and parachinit by high-performance liquid chromatography (HPLC). The sugar alcohols were converted into strong ultraviolet (UV)-absorbing derivatives with p-nitrobenzoyl chloride. HPLC was performed on a phenyl column, using acetonitrile-water (67:33) as mobile phase and UV detection (260 nm). The calibration curves for all sugar alcohols tested were linear in the 10-250 microg/ml range. The average recoveries of the sugar alcohols from four sugarless confectioneries spiked at 5 and 10% levels of six sugar alcohol standards ranged from 73.2 to 109.0% with relative standard deviations ranging from 0.7 to 9.0%. The detection limit of the developed method was 0.1% for the above sugar alcohols contained in the samples.     

Determination of γ‐hydroxybutyric acid in saliva by capillary electrophoresis coupled with contactless conductivity and indirect UV absorbance detectors

The aim of the current study was to optimise and validate the methodology for determination of γ‐hydroxybutyric acid (GHB) in saliva by CE combined with a contactless conductivity detector (C⁴D) and indirect UV absorbance detection (λ_ABS = 210 nm). The optimized BGE, consisting of 8.5 mM maleic acid, 17 mM arginine, 255 μM cetyltrimethylammonium bromide (CTAB), and 15% acetonitrile, was evaluated for the separation of GHB in saliva within 6 min. The performance characteristics of the CE‐C⁴D‐indirect UV methodology was validated. The instrument detection and quantification limits were 0.49 and 1.6 mg/L for C⁴D, and 5.1 mg/L and 17.0 mg/L for indirect UV, respectively. The linearity was obtained over the range from 2.5 to 400 mg/L for C⁴D and from 12.5 to 400 mg/L for indirect UV. The interday precisions were within 2.3–5.7% and intraday precisions were within 1.6–9.0% for C⁴D as well as 2.1–9.3%, 5.6–10.1% for indirect UV in spiked saliva, respectively. The recoveries were within 87.2–104.4%. The matrix effects were +53.2% for small concentrations up to 25 mg/L for C⁴D and +23.6% for concentrations up to 75 for mg/L for indirect UV detection. No matrix effects were observed for higher concentration levels. In conclusion, CE‐C4D‐indirect UV can offer a rapid, accurate, sensitive, and definitive method for the determination of GHB abuse in saliva samples as a forensic screening tool.     

高效液相色谱-蒸发光散射法测定食品中的单糖、双糖、低聚果糖和糖醇

建立了食品中常用的木糖、果糖、葡萄糖、蔗糖、麦芽糖、乳糖、蔗果三糖、蔗果四糖、蔗果五糖、赤藓糖醇、木糖醇、甘露糖醇、麦芽糖醇等13种单糖、双糖、低聚果糖和糖醇的高效液相色谱同时分离检测的方法。该法采用NH₂色谱柱,以乙腈-水为流动相梯度洗脱,蒸发光散射检测器检测;13种糖在0.1~5 g/L内均具有良好的线性关系,检出限均在0.1 g/L以下,精密度(RSD)为2.69%~7.21%,回收率为96.1%~105.2%,结果较为理想。将该法用于实际样品检测,结果显示食品标签明示和实际成分相差较大。     

Influence of Polyols and Glucose on the Surface Tension of Bovine <Emphasis Type="Italic">α</Emphasis>-Lactalbumin in Aqueous Solution

The native conformation of a protein is controlled by intramolecular interactions between protein functional groups and intermolecular interactions between protein and solvent molecules that are dominant at low protein concentrations. It has been proposed that the stabilizing effect of polyols and sugars is a consequence of the increase in the surface tension of the solution resulting from the addition of osmolytes. In this work, a systematic study is presented concerning the effect of erythritol, xylitol, sorbitol, inositol and glucose on the surface tension of α-lactalbumin in aqueous solution at 298.15 K. The results show that there is no general correlation between the surface tension of the solvent and a change in the denaturation temperature of holo-lactalbumin in the presence of polyols and glucose. However, for each of the osmolytes used, the change in denaturation temperature increases as the solvent’s surface tension becomes higher.     

Catalytic Conversion of Biomass-Derived Polyols into Para-xylene over SiO2-Modified Zeolites

This work proved that biomass-based polyols (sorbitol, xylitol, erythritol, glycerol and ethanediol) were able to be converted into high-value chemical (p-xylene) by catalytic cracking of polyols, alkylation of aromatics, and the isomerization of xylenes over the SiO₂-modified zeolites. Compared to the conventional HZSM-5 zeolite, the SiO₂-containing zeolites considerably increased the selectivity and yield of p-xylene due to the reduction of external surface acidity and the narrowing of pore entrance. The influences of the methanol additive, reaction temperature, and types of polyols on the selectivity and yield of p-xylene were investigated in detail. Catalytic cracking of polyols with methanol significantly enhanced the production of p-xylene by the alkylation of toluene with methanol. The highest p-xylene yield of 10.9 C-mol% with a p-xylene/xylenes ratio of 91.1% was obtained over the 15wt%SiO₂/HZSM-5 catalyst. The reaction pathway for the formation of p-xylene was addressed according to the study of the key reactions and the characterization of catalysts.     

Analysis of short‐chain aliphatic amines in food and water samples using a near infrared cyanine 1‐(ε‐succinimydyl‐hexanoate)‐1′‐methyl‐3,3,3′,3′‐tetramethyl‐indocarbocyanine‐5,5′‐disulfonate potassium with CE–LIF detection

Precolumn derivatization of six short‐chain aliphatic amines by a near‐infrared dye, 1‐(ε‐succinimydyl‐hexanoate)‐1′‐methyl‐3,3,3′,3′‐tetramethyl‐indocarbocyanine‐5,5′‐ disulfonate potassium (MeCy5‐OSu), followed by MEKC–CE–LIF detection has been developed as a method for the determination of aliphatic amines in environmental water and food. Optimum derivatization was operated nicely in pH 9.0 borate buffer at 20°C for 30 min. Well separated peaks were observed with a pH 9.5 BGE containing 10 mmol L^?1 phosphoric acid, 20 mmol L^?1 SDS, and 7% methanol buffered with 1.0 mol L^?1 NaOH. The separation procedure was rapidly achieved within 11 min and the matrix interferences could be effectively eliminated. A linear calibration graph was obtained for 5–200 nmol L^?1 analytes with a correlation coefficient in the range 0.9933–0.9995 for amines. This method was successfully utilized to determine aliphatic amines in lake, sewage water, and red wine with recoveries ranging from 96.4 to 105% and the RSDs ranging from 0.9 to 2.9%. Near‐infrared, LIF‐detector‐compatible MeCy5‐OSu was proved suitable for the accurate, sensitive, and rapid separation and determination of aliphatic amines in water and food samples.     

Phase and state transition effects on dielectric, mechanical, and thermal properties of polyols

The present study investigated the glass transition, crystallisation and melting behaviour of erythritol, xylitol, and glucitol (sorbitol) using dielectric analysis (DEA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). Sorbitol and xylitol were plasticised by water and their glass transition temperatures decreased when water content was increased. Erythritol crystallised rapidly, and its water plasticisation behaviour could not be determined. Melting of the crystalline polyols occurred at their specific melting temperatures. Melts of erythritol and xylitol crystallised on recooling and no glass transition was apparent on reheating. Quench cooled sorbitol melt remained amorphous and showed a glass transition on reheating. Glass transition and crystallisation were apparent in the DSC thermogram and the dielectric and the dynamic mechanical spectra of mixtures of amorphous and crystalline xylitol.     

离子色谱-质谱联用法检测食品中的糖醇

建立了离子色谱-质谱(IC-MS)联用方法检测食品中的糖醇。不同食品样品中的糖醇经提取后过SPE柱去除杂质,再经CarboPar MA1糖醇柱分离,在选择离子监测(SIM)模式下进行检测,外标法定量。各目标物在一定范围内线性关系良好,相关系数(R²)均大于0.99。赤藓糖醇、木糖醇、D-山梨糖醇、D-甘露糖醇、乳糖醇、麦芽糖醇的定量限(S/N=10)分别为0.98、1.99、2.24、5.92、13.56、13.21 mg/kg;检出限(S/N=3)分别为0.28、0.59、0.71、1.74、4.14、4.03 mg/kg。6种糖醇的加标回收率为82.5%~108.0%,相对标准偏差(RSD)为1.5%~7.6%。该方法的灵敏度、准确度和精密度均符合相关的技术要求,适用于食品中糖醇含量的检测。     

Rapid and direct determination of glyphosate,glufosinate, and aminophosphonic acid by online preconcentration CE with contactless conductivity detection

Rapid and direct online preconcentration followed by CE with capacitively coupled contactless conductivity detection (CE‐C⁴D) is evaluated as a new approach for the determination of glyphosate, glufosinate (GLUF), and aminophosphonic acid (AMPA) in drinking water. Two online preconcentration techniques, namely large volume sample stacking without polarity switching and field‐enhanced sample injection, coupled with CE‐C⁴D were successfully developed and optimized. Under optimized conditions, LODs in the range of 0.01–0.1 μM (1.7–11.1 μg/L) and sensitivity enhancements of 48‐ to 53‐fold were achieved with the large volume sample stacking‐CE‐C⁴D method. By performing the field‐enhanced sample injection‐CE‐C⁴D procedure, excellent LODs down to 0.0005–0.02 μM (0.1–2.2 μg/L) as well as sensitivity enhancements of up to 245‐ to 1002‐fold were obtained. Both techniques showed satisfactory reproducibility with RSDs of peak height of better than 10%. The newly established approaches were successfully applied to the analysis of glyphosate, glufosinate, and aminophosphonic acid in spiked tap drinking water.     

Sorbitol Hydrogenolysis to Glycols over Baisic Additive Promoted Ni-based Catalysts

A series of Ni based catalysts with different supports and basic additives were prepared by sequential impregnation method. The catalysts were characterized by XRD, BET, H₂-TPR and CO₂-TPD techniques. It was found that the introduction of basic additives enhanced the basicities of catalyats and promoted the dispersities of Ni particles by strong interaction between Ni²⁺ and basic additives. Among the Ni based catalysts, 10%Ni/10%La₂O₃/ZrO₂ showed the superior performance in sorbitol hydrogenolysis. The synergistic effect of Ni and La₂O₃ was proven to play an essential role in selective synthesis of EG and 1,2-PG. In the optimal reaction condition, the catalyst presented 100% sorbitol conversion and over 48% glycols (EG and 1,2-PG) yield. The kinetics study of polyols (sorbitol, xylitol and glycerol) hydrogenolysis showed that polyols with more hydroxyl number have higher activity and products distribution was final results of kinetic balance, which could give us some inspiration about how to change the products selectivity.     

Determination of polyol profiles in human urine by capillary gas chromatography

A new rapid capillary gas chromatographic method is described for the profile analysis of urinary polyols as their trifluoroacetyl derivatives. Ten urinary polyols: erythritol, threitol, fucitol, ribitol, arabinitol, xylitol, mannitol, glucitol, galactitol and myo-inositol were completely determined for the first time. Iditol was newly found in normal urine. Urinary polyols were verified by gas chromatography/mass spectrometry.     

Simultaneous Determination of Glyphosate,Glufosinate, and Aminomethylphosphonic Acid by Capillary Electrophoresis After 9‐Fluorenylmethyl Chloroformate Derivatization

A capillary electrophoresis (CE) with UV absorption detection method is described for the simultaneous determination of glufosinate, glyphosate, and aminomethylphosphoric acid. The 9‐fluorenylmethyl chloroformate (FMOC‐Cl) was used for precolumn derivatization of the non‐absorbing herbicides. The three analytes were separated by CE in 9 min with 25 mM borate buffer at pH 9, followed by detection with a UV detector at 260 nm. We demonstrate how the detection limit can be enhanced by using acetonitrile‐salt mixtures. With acetonitrile‐salt mixtures, the limit of detection (LOD) was in the 10^?7 M range. Linearity of more than two orders of magnitude was generally obtained. Precisions of migration times and peak areas were less than 0.9% and 7.5%, respectively. The applicabilities of the method for the analysis of ground water and lake water were examined.     

Lanthanide‐IMAC enrichment of carbohydrates and polyols

In this study a new type of immobilized metal ion affinity chromatography resin for the enrichment of carbohydrates and polyols was synthesized by radical polymerization reaction of vinyl phosphonic acid and 1,4‐butandiole dimethacrylate using azo‐bis‐isobutyronitrile as radical initiator. Interaction between the chelated trivalent lanthanide ions and negatively charged hydroxyl groups of carbohydrates and polyols was observed by applying high pH values. The new method was evaluated by single standard solutions, mixtures of standards, honey and a more complex extract of Cynara scolymus. The washing step was accomplished by acetonitrile in excess volumes. Elution of enriched carbohydrates was successfully performed with deionized water. The subsequent analysis was carried out with matrix‐free laser desorption/ionization–time of flight mass spectrometry involving a TiO₂‐coated steel target, especially suitable for the measurement of low‐molecular‐weight substances. Quantitative analysis of the sugar alcohol xylitol as well as the determination of the maximal loading capacity was performed by gas chromatography in conjunction with mass spectrometric detection after chemical derivatization. In a parallel approach quantum mechanical geometry optimizations were performed in order to compare the coordination behavior of various trivalent lanthanide ions. Copyright © 2013 John Wiley & Sons, Ltd.     

Rapid screening of inorganic and organic anions in liquid by‐products from hydrothermal treatment of biomass by capillary electrophoresis

A simple and rapid capillary electrophoresis method with capacitively coupled contactless conductivity detection (CE‐C⁴D) for the simultaneous determination of inorganic and organic anions in liquid product obtained from the hydrothermal treatment of biomass residues is presented. Under the optimal analytical conditions, limits of detection ranged from 1.8 to 9.4 μM for most target solutes and 53 μM for citrate. Relative standard deviations were below 0.5% for migration times and within 0.6–6.5% for peak areas for all solutes. The proposed method was successfully applied for the rapid determination and screening of inorganic and organic anions in liquid product produced following differing hydrothermal treatment temperatures for banana and pineapple biomass, and the contribution of organic acid formation to acidity in the liquid was evaluated. CE‐C⁴D could be a suitable method for the optimization or tailoring of HTT conditions for desired liquid product composition, and additionally for determination of the best variety(s) of biomass to use in such processes.     

Influence of calcium on the thermal stabilization of bovine α-lactalbumin by selected polyols

Thermal stability of bovine α-lactalbumin in the presence of three different calcium concentrations in aqueous solutions of several concentrations of erythritol, xylitol, sorbitol, and inositol at pH 6.5 was evaluated by UV absorbance, fluorescence spectroscopy, and circular dichroism spectroscopy. At the selected conditions, the thermal denaturation process is reversible and is well described by a two-state model. Results show a higher stability for the holo form of the protein in the presence of calcium, followed by the holo- and the apo-lactalbumin, respectively. The stabilizing effect of the polyols increases with polyol concentration and it is higher for the apo-lactalbumin than holo-lactalbumin and is very small for the protein in the presence of a calcium excess.     

Recent advances in catalytic production of sugar alcohols and their applications

Conversion of non-edible biomass into fuels and value-added chemicals has achieved great attention to cope the world's energy requirements. Lignocellulose based sugar alcohols such as sorbitol, mannitol, xylitol, and erythritol can be potentially used as emerging fuels and chemicals. These sugar alcohols can be converted into widely used products(e.g. polymer synthesis, food and pharmaceuticals industry). The heterogeneous catalytic production of sugar alcohols from renewable biomass provides a safe and sustainable approach. Hydrolysis, coupled with hydrogenation and hydrogenolysis has been proved to be more effective strategy for sugar alcohols production from biomass. This review summarizes the recent advances in biomass upgrading reactions for the production of sugar alcohols and their comprehensive applications.     

Electrochemical derivatization‐capillary electrophoresis‐contactless conductivity detection: A versatile strategy for simultaneous determination of cationic,anionic, and neutral analytes

The simultaneous determination of cationic, anionic, and neutral analytes in a real sample was demonstrated by coupling electrochemical (EC) derivatization with counter‐EOF CE‐C⁴D. An EC flow cell was used to oxidize alcohols from an antiseptic mouthwash sample into carboxylic acids at a platinum electrode in acid medium. The carboxylates formed in the derivatization process and other sample ingredients, such as benzoate, saccharinate, and sodium ions, were separated in counter‐flow mode and detected in one run in Tris‐HCl buffer, pH 8.6. Fewer than 5 min were needed to complete each analysis with the automated flow system comprising solenoid pumps for the management of solutions. Insights into the electrochemistry of benzoic acid, present in the sample matrix, were also gained by EC‐CE‐C⁴D; more specifically, by applying potentials higher than 1.47 V to the platinum electrode, some formiate and minute amounts of salicylate were detected.     

Dispersive liquid–liquid microextraction based on solidification of floating organic drop combined with field‐amplified sample injection in capillary electrophoresis for the determination of beta(2)‐agonists in bovine urine

Dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLME–SFO) was for the first time combined with field‐amplified sample injection (FASI) in CE to determine four β₂‐agonists (cimbuterol, clenbuterol, mabuterol, and mapenterol) in bovine urine. Optimum BGE consisted of 20 mM borate buffer and 0.1 mM SDS. Using salting‐out extraction, β₂‐agonists were extracted into ACN that was then used as the disperser solvent in DLLME–SFO. Optimum DLLME–SFO conditions were: 1.0 mL ACN, 50 μL 1‐undecanol (extraction solvent), total extraction time 1.5 min, no salt addition. Back extraction into an aqueous solution (pH 2.0) facilitated direct injection of β₂‐agonists into CE. Compared to conventional CZE, DLLME–SFO–FASI–CE achieved sensitivity enhancement factors of 41–1046 resulting in LODs in the range of 1.80–37.0 μg L^?1. Linear dynamic ranges of 0.15–10.0 mg L^?1 for cimbuterol and 15–1000 μg L^?1 for the other analytes were obtained with coefficients of determination (R²) ≥ 0.9901 and RSD% ≤5.5 (n = 5). Finally, the applicability of the proposed method was successfully confirmed by determination of the four β₂‐agonists in spiked bovine urine samples and accuracy higher than 96.0% was obtained.