Simple and accurate method for determination of ethylene chlorohydrin in dried spices and condiments

A simple and accurate method is described for the determination of ethylene chlorohydrin (ECH) by using capillary gas chromatography (GC) and flame ionization detection. Acetonitrile-methanol was chosen as the extraction solvent in preference to other solvents because its use reduced the number of compounds detected by the GC system, thus enabling easier identification and quantitation of ECH. The coefficient of variation for the method is 2.7% at 5 ppm, and recovery is good, even for the standard addition of 1 ppm. Fifteen different spices and condiments were analyzed using this method; 20% were identified as positive for ECH. The method also identifies the related compound ethylene bromohydrin (EBH).     

Leaching of ethylene glycol and ethanol in subsoils

The use of the heat pumps connected to ground coils wins widespread interest in the heating of buildings, but in cases of leakage it may involve a risk of ground water pollution caused by anti-freeze mixture components. The adsorption of individual components, such as ethylene glycol, ethanol, methanol, and benzoic acid onto different soil types was studied at 6 °C by use of a batch procedure. No adsorption (or only slight) was observed for any of the test compounds onto samples of subhorizons of sandy till, clayey till, and melt water sand. Leaching experiments with undisturbed soil cores of sandy till showed that ¹⁴C-labelled ethylene glycol or ethanol closely followed the movement of water when cloride was used as a tracer. The percolation experiments were conducted during 79 to 154 day periods at 10 °C and under anaerobic conditions. Darcy velocities varied between 1 and 3 mm day^?1. About 100% of the added amounts of ¹⁴C were recovered in the effluents, although only 74 to 77% of ethylene glycol and 84 to 89% of ethanol were determined as the parent compounds by gas chromatography. Experiments on leaching of ethanol under controlled oxygen supply showed that degradation took place dependent on oxygen availability.     

Simultaneous analysis of grain and grain-based products for ethylene dibromide, carbon tetrachloride, and ethylene dichloride

A method is described for the simultaneous measurement of parts per billion levels of the fumigants ethylene dibromide, carbon tetrachloride, and ethylene dichloride in grain and grain-based products. The fumigants are isolated by hexane co-distillation, separated by capillary gas chromatography, and detected with a mass spectrometer in the selected ion monitoring mode. Recoveries are greater than 90% and standard deviations are approximately 10% of the quantity measured. The method is free of interferences and its precision and accuracy are enhanced by the use of tetradeuterated ethylene dibromide and ethylene dichloride as internal standards.     

Improved codistillation method for determination of carbon tetrachloride, ethylene dichloride, and ethylene dibromide in grain and grain-based products

A method is described for the determination of the common fumigants carbon tetrachloride (CCl4), ethylene dichloride (EDC), and ethylene dibromide (EDB) in grain and grain-based products. A properly prepared sample is mixed with water and hexane, an internal standard mixture of 1,2-dichloropropane (DCP) and 1,2-dibromopropane (DBP) is added, and the fumigants are codistilled with the hexane into an appropriate receiver. After the hexane solution is dried over sodium sulfate, the quantities of fumigants present are quantitated on a gas chromatograph (GC) equipped with an electron capture detector (ECD). For the matrices investigated, the relative standard deviation of the method was 6.0, 9.7, and 23.1% for CCl4, EDC, and EDB, respectively. Recoveries of added fumigants were 107, 95, and 101%, respectively. Comparison with an acetone-water soak extraction method gave a correlation of 0.967 between methods for EDB with odds of a difference between methods of 35%.     

Effect of moisture content on ethylene glycol retention by clay minerals

For the accurate determination of ethylene glycol retention by soil minerals, precision in moisture removal is extremely important. One percent decrease in moisture appears to increase the ethylene glycol retention by 10 to 12 mg/g of sample. Drying samples over P₂O₅ is tedious and requires considerable care. An alternate method that is precise and easy is presented. By this method, an air-dried Ca-saturated subsample suspected of containing irreversibly dehydrating clays is saturated and equilibrated with ethylene glycol. The retention values are determined on a moisture-free weight basis calculated from a duplicate subsample dried in an oven at 105°C. Ethylene glycol retention of samples that do not contain irreversibly dehydrating clays is determined directly by saturation and equilibration of 105°C oven-dried samples.     

Gas chromatographic determination of ethylene dibromide in flour products

A method based on gas chromatography with electron capture detection was developed for the determination of ethylene dibromide (EDB) extracted from flour products. The procedure relies on the organic extraction of flour/water mixtures and uses an internal standard, 1-bromo-3-chloropropane. Recoveries of EDB at 10 and 100 ppb were 80.1 +/- 2.8% (SD) and 84.4 +/- 4.3%, respectively; recovery of the internal standard at the working concentration 500 ppb was 98.3 +/- 6.7%. Calibration curves were linear over the range 5-400 ppb, with a mean overall coefficient of variation of less than 5%. The reliability of the procedure was assessed by using gas chromatography combined with mass spectrometry. Results are shown for determination of EDB in locally milled flour products.     

Determination of poly(ethylene glycol)-binding to browse foliage, as an assay of tannin, by near-infrared reflectance spectroscopy

Nutritionists are interested in functional assays of tannins that do not require time-consuming and expensive extraction, such as the (14)C-labeled poly(ethylene glycol) (PEG)-binding (PEG-b) assay. This paper reports the application of near-infrared (NIR) spectroscopy to determine the percentage of PEG binding, in place of the (14)C-labeled PEG-b assay of tannin, in Mediterranean woodland vegetation. Calibration was done with 53 samples from 14 species and was validated on 25 samples from 10 species. PEG-b ranged between 1.4 and 20.7% in the samples. The calibration obtained by using the modified partial least-squares (MPLS) method, with all wavelengths in the 1100-2500 nm range combined, and the validation were reasonably linear (R (2) = 0.96 and 0.91, respectively). The accuracies, estimated from the standard errors of cross-validation and prediction, were +/-1.6 and +/-1.7% PEG-b, respectively. The NIRS-aided procedure proposed here can serve as an accurate, inexpensive, time-saving, and environment-friendly functional assay of tannin in Mediterranean browse.     

Determination of ethylene oxide in ethoxylated surfactants and demulsifiers by headspace gas chromatography

A headspace gas chromatographic method for the determination of traces of ethylene oxide in ethoxylated surfactants and demulsifiers was developed. Samples are analyzed directly by the technique to a 1.0 ppm (w/w) quantitation limit. The procedure also performs well for propylene oxide, acetaldehyde, and 1,4-dioxane. It is simple, sensitive, and linear. The percent relative standard deviations for 0.5 and 30 ppm ethylene oxide in the surfactant were 2.8 and 8.3%, respectively.     

Migration of ethylene glycol from polyethylene terephthalate bottles into 3% acetic acid

Migration of ethylene glycol (EG) from polyethylene terephthalate (PET) bottles into the food simulate 3% acetic acid was studied using 32 fluid oz PET bottles filled with 3% acetic acid and stored at 32 degrees C for 6 months. Final concentration of EG in the 3% acetic acid migration solution was about 100 ppb, which is equivalent to about 94 microgram EG/bottle. A gas-liquid chromatographic procedure for quantitating EG was developed which is capable of measuring EG levels as low as 50 ppb in the migration solution.     

乙二醇-氯化铁预处理对棉秆酶水解效率的影响

为提高棉秆的纤维素酶水解效率,该研究以乙二醇为预处理溶剂,氯化铁为催化剂对棉秆进行预处理,实现了棉秆木质素和半纤维素的有效去除,提高了酶水解效率。以木质素和半纤维素的去除率为指标,运用正交试验方法优化乙二醇-氯化铁预处理条件。结果表明,棉秆在90%乙二醇水溶液,0.1 mol/L氯化铁,固液比1∶15,160 ℃条件下处理20 min,木质素和半纤维素去除率分别为85.7%和88.9%。相较原料,预处理后棉秆酶解率提高了7.6倍,葡萄糖产率达到100%（基质浓度5%,酶载量8.3 FPU/g,水解72 h条件下）。通过结构表征发现乙二醇-氯化铁预处理使棉秆的比表面积增大,致密结构被破坏,有效提高了棉秆的纤维素酶可及性。     

Determination of methylene chloride, ethylene dichloride, and trichloroethylene as solvent residues in spice oleoresins, using vacuum distillation and electron capture gas chromatography.

A quantitative gas chromatographic (GC) method is described for the determination of residual methylene chloride, ethylene dichloride, and trichloroethylene in spice oleoresins. The proposed method involves vacuum distillation in a closed system with toluene as a carrier solvent. Quantitation by electron capture GC on Porapak Q is facilitated by water extraction and by the addition of trans-1,2-dichloroethylene as an internal standard. Recoveries from oleoresins spiked at 30, 15, and 6 ppm ranged from 93 to 102%. To assess the possibility of interference from spice volatiles, the procedure was applied to 17 different spice oleoresins from 3 different manufacturers. No interferences were found, but methylene chloride levels up to 83 ppm and ethylene dichloride levels up to 23 ppm were detected. Trichloroethylene was not detected in any of the oleoresins.     

正电晕放电耦合Ag-TiO_2降解乙烯的动力学及参数优化

为了解直流正电晕-纳米银沉积纳米TiO2光电催化耦合反应系统降解乙烯及调控臭氧的机理及其动力学规律,该文采用多针对圆筒内壁式电晕放电反应器为对象,在模拟园艺产品的冷藏环境中,进行了纳米TiO2的掺银量、放电功率和气流量等因素对乙烯降解和臭氧控制效果的影响研究。结果表明:建立了正电晕放电耦合活性炭纤维(activated carbon fiber,ACF)负载掺银的纳米TiO2(Ag-TiO2/ACF、Ag-TiO2*/ACF)降解乙烯的动力学模型,通过龙格库塔法数值求解微分方程组和最小二乘法得到动力学模型的反应常数,通过对反应常数比较,正电晕放电耦合Ag-TiO2*/ACF催化膜对乙烯降解和控制臭氧浓度具有较优的性能。采用二次旋转组合试验和回归拟合,建立了正电晕放电耦合Ag-TiO2*/ACF催化膜的乙烯降解反应常数、臭氧浓度上限的预测值与影响因素关系的二次多项数学模型,验证了模型的有效性,并优化出反应体系参数。研究结果为正直流电晕放电耦合纳米二氧化钛技术在园艺产品贮运保鲜设备中的应用提供了依据。     

乙烯分解纳米光催化反应器关键性能参数研究

果品与蔬菜在采后贮藏过程中所产生和释放的乙烯是加速成熟、衰老和腐烂的重要环境因子。该研究采用纳米光催化技术开发设计了一种可以去除气调库中乙烯的玻璃管光催化反应器，并对其主要性能参数进行了模拟测试与分析。结果表明：气体流量、玻璃管直径与长度以及光源种类均是影响光催化反应器乙烯分解性能的主要因素。在该试验条件下，气体流量在40～80 L/h的范围内较佳；玻璃管的适宜内径为50 mm；在相同功率条件下黑光灯的光催化效果优于紫光灯。光催化反应器可以多级串联使用，以便提高系统的乙烯分解能力。这些研究结果为气调库用光催化乙烯分解装置设计提供了基础设计参数和指标。     

Effects of hydrophilic plasticizers on mechanical, thermal, and surface properties of chitosan films

Chitosan films were plasticized with four hydrophilic compounds, namely, glycerol (GLY), ethylene glycol (EG), poly(ethylene glycol) (PEG), and propylene glycol (PG). Our objective was to investigate the effect of plasticizers on mechanical and surface properties of chitosan films. The stability of plasticized films was observed by storage for 3 and 20 weeks in an environmental chamber at 50 +/- 5% RH and 23 +/- 2 degrees C. Plasticization improves the chitosan ductility, and typical stress-strain curves of plasticized films have the features of ductile materials, except the film made with 5% PG that exhibits as a brittle polymer and shows an antiplasticization effect. In most cases, the elongation of plasticized films decreases with the storage time, which might be due to the recrystallization of chitosan and the loss of moisture and plasticizer from the film matrix. Although at the beginning the mechanical properties of films made with PG, at high plasticizer concentration, are comparable to those of films made with EG, GLY, and PEG, their stability is poor and they tend to become brittle materials. The surface properties, analyzed by contact angle measurement, reveal that plasticization increases film hydrophilicity. It is found that GLY and PEG are more suitable as chitosan plasticizers than EG and PG by taking into account their plasticization efficiency and storage stability. Furthermore, a plasticizer concentration of 20% (w/w) with GLY or PEG seemingly is sufficient to obtain flexible chitosan film with a good stability for 5 months of storage.     

Gas chromatographic method for ethylene dibromide in grains and grain-based products: collaborative study

Nine laboratories analyzed samples of whole grain, intermediate, and ready-to-eat products for ethylene dibromide (EDB) residues. Supplied samples of wheat, rice, and flour contained both fortified and incurred EDB; corn bread mix, baby cereal, and bread contained only fortified EDB. The whole grains and intermediates were analyzed by the same basic procedural steps as in the official method for multifumigants: They were extracted by soaking in acetone-water (5 + 1). The baby cereal and bread were analyzed by a modification of the Rains and Holder hexane co-distillation procedure. EDB was determined by electron capture gas chromatography operated with an SP-1000 column. All products contained 3 different levels of EDB and were analyzed as blind duplicates. Overall mean recoveries ranged from 85.2% for 69.6 ppb to 105.0% for 4.35 ppb, both in baby cereal. Interlaboratory relative standard deviations ranged from 5.7% for 869 ppb in wheat to 20.2% for 69.6 ppb in baby cereal, both fortified. Mean levels of incurred EDB in wheat, rice, and flour were 926.7, 982.0, and 49.9 ppb, respectively; corresponding relative standard deviations were 9.9, 7.7, and 13.1%. The method was adopted official first action.     

Diffusion of coefficients of carbon dioxide, nitrous oxide, ethylene and ethane in air and their measurement

Binary diffusion coefficients were measured by a steady-state method in which a gas was introduced at a constant rate into one end of a tube through which it moved by mass flow and diffusion into a semi-infinite volume of air. The Stefan correction for mass flow was modified to allow for initial gas concentrations < 100 per cent, conferring four advantages: errors in the total flow rate are relatively unimportant; density gradients are small so that convection is inhibited; the gas analysis is more sensitive; and diffusion coefficients are measured at the small concentrations that are encountered in soils. Measured diffusion coefficients (cm² s^?1 at NTP) in air for carbon dioxide (0.139), nitrous oxide (0.143), ethylene (0.137) and ethane (0.128) are compared with measured and calculated values from other sources.     

外源乙烯对镉处理下玉米幼苗生理代谢的影响

为探讨外源乙烯缓解玉米（Zea mays）幼苗镉（Cd）毒害的生理机制,通过水培试验研究了Cd处理下,外源乙烯对玉米幼苗相关生理指标与Cd的亚细胞分布的影响,以不做任何处理为空白对照,以Cd处理和（NH₄）₂SO₄处理为试验对照。结果显示,相对Cd处理,乙烯和（NH₄）₂SO₄处理可显著降低Cd胁迫下玉米幼苗H₂O₂和丙二醛（MDA）含量,使净光合速率分别提升1.23倍和1.22倍;显著降低抗氧化物酶[超氧化物歧化酶（SOD）、过氧化氢酶（CAT）]活性,抗氧化物质[抗坏血酸（AsA）、谷胱甘肽（GSH）]含量则显著上升。另外,相对于Cd处理,乙烯+Cd处理可使玉米幼苗ATP硫酸化酶活性、谷胱甘肽还原酶（GR）活性、半胱氨酸和还原型谷胱甘肽（GSH）含量分别上升54.43%、27.93%、50.77%和49.85%,而对非蛋白硫醇（NPT）和植物螯合素（PCs）含量无显著性影响。在乙烯+Cd处理的基础上添加GSH合成抑制剂BSO（buthionine sulfoximine）可导致玉米叶片GSH含量显著降低,H₂O₂含量上升,光合速率下降。外源乙烯可显著降低Cd胁迫下玉米叶片Cd含量,而显著提升根部细胞壁和液泡中Cd含量。因此,外源乙烯一方面通过提升玉米叶片GSH和AsA含量,增强叶片非酶促抗氧化能力,而非通过抗氧化酶促反应和NPT、PCs的螯合作用;另一方面则通过根细胞壁的固定作用和液泡区室化作用,减少Cd向玉米叶片中的转移,从而缓解Cd毒害。研究结果可为乙烯作为潜在的作物重金属拮抗剂提供理论依据。     

介质阻挡放电降解果蔬贮藏环境中的乙烯

为了去除园艺产品贮运环境中的乙烯以达到保鲜效果,该研究采用一种介质阻挡放电（DBD）反应器对乙烯进行降解,对影响乙烯降解的各主要因素进行了考察。结果表明,放电间隙1 mm、放电功率大于15 W、气体流量1.5 L/min时乙烯的降解效果较好,30 min内乙烯被完全降解;产生的臭氧能够更好促进乙烯的降解,但也存在随功率增加臭氧含量突增的缺陷。低温等离子体技术在果蔬保鲜领域是有应用前景的。     

Role of ethylene and abscisic acid in physicochemical modifications during melon ripening

Hormonal metabolism associated with fruit ripening in two cantaloupe muskmelon cultivars, Talma and Manta, has been studied. The ethylene crisis began on day 33 after fruit set, reaching the maximum values of internal ethylene concentration and ethylene production rate on day 35 after fruit set. This was the optimum moment for consumption as shown by the higher content in soluble solids, ripening index, sensory analysis, and color parameter values. The b parameter and the b/a quotient values in peel were good indicators of the maturity stage, the optimum moment for harvesting being about day 33 after fruit set (when autocatalytic ethylene synthesis has begun), with values of 20 and 5 for the b parameter and b/a quotient, respectively. In both cultivars, free 1-aminocyclopropane-1-carboxylic acid (ACC) content increased until day 35 after fruit set and conjugated ACC increased in postclimacterium. The increase in both ACC-synthase and ACC-oxidase activities together could be responsible for the climacteric ethylene production. Significant differences in the abscisic acid evolution in Talma and Manta cultivars were reached, and also a possible stimulation of ethylene by this hormone could be established.     

Simultaneous gas chromatographic determination of carbofuran, metalaxyl, and simazine in soils

A method for extraction, cleanup, and simultaneous gas chromatographic detection of carbofuran, metalaxyl, and simazine in soils has been developed. Pesticide residues were extracted from soil with acetone containing 10% 0.2M HCl-KCl buffer (pH 2.0), cleaned up with methylene chloride-carbonate buffer (pH 10.7) solvent partitioning and solid-phase extraction on disposable silica gel columns, and quantitated with gas chromatography using a Supelcowax 10 megabore capillary column and a nitrogen-selective detector. Method limits of detection were 0.02 microgram/g for the 3 pesticides in surface soils (0-30 cm depths) and 0.02, 0.02, and 0.005 microgram/g in soils below 30 cm (subsoils) for carbofuran, metalaxyl, and simazine, respectively. Recoveries for carbofuran, metalaxyl, and simazine were 92.6 +/- 5.5, 93.6 +/- 5.0, and 88.4 +/- 6.7%, respectively, when soil samples were spiked with pesticide concentrations ranging from 0.02 to 2.0 micrograms/g.