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1.
Isothermal gas chromatography with flame ionization detection was used to determine residual ethylene oxide (EtO), ethylene chlorohydrin, and ethylene glycol in soft rubber catheters that had been sterilized with EtO. Catheter samples were extracted by shaking with carbon disulfide, and the extract was analyzed on a 3% Carbowax 20M on 80-100 mesh Chromosorb 101 column, using nitrogen as the carrier gas. Ten replicate injections of a mixed standards solution gave coefficients of variation of 1.91, 1.23, and 4.74% for EtO, ethylene chlorohydrin, and ethylene glycol, respectively. A linear response was obtained with concentrations ranging from 1.0 to 7.9 micrograms EtO, 14.0 to 88.0 micrograms ethylene chlorohydrin, and 31.0 to 98.5 micrograms ethylene glycol. The proposed method detected as little as 0.5, 5.0, and 16.5 ng EtO, ethylene chlorohydrin, and ethylene glycol, respectively.  相似文献   

2.
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.  相似文献   

3.
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%.  相似文献   

4.
Mature green bananas were treated with the ethylene antagonist 1-methylcyclopropene (1-MCP) at intervals during the 24 h period after initiation of ripening with propylene. Following 1-MCP treatment, the fruits were ripened in either air or propylene while ethylene, carbon dioxide, and volatile production and composition were monitored at regular intervals. The application of 1-MCP significantly delayed and suppressed the onset and magnitude of fruit respiration and volatile production. The 1-MCP treatments also caused a quantitative change in the composition of the aroma volatiles, resulting in a substantial increase in the concentration of alcohols and a decrease in their related esters. The results showed that ethylene has a continuing role in integrating many of the biochemical processes that take place during the ripening of bananas.  相似文献   

5.
Summary In vitro maintenance of plant organs can enhance programs in plant breeding and germplasm resources. In bulbous plants, such as onion (Allium cepa L.) and leek (A. ampeloprasum L.) induction and storage of in vitro bulblets could enable long term maintenance of special genotypes. In vitro cultivated seedlings of onion and leek were induced to form bulblets by increase in sucrose concentration (30, 50, 150 g/1), and addition of benzyladenine (BA-0, 12.5 mg/1), or ethephon (0, 5, 20 days). The highest bulbing ratios were obtained within combinations of sucrose and ethephon treatments. BA caused not only bulb swelling but also an increase of multiple adventitious shoot formation. Increasing the sucrose concentration and treatment with ethephon are used to obtain bulblets for in vitro storage under conditions of slow growth.Abbreviations BA benzyladenine - BDS medium according to Dunstan & Short (1977) - BD maximal basis (bulb) diameter - BI bulbing index - BC basal callus - BS basal sprouting - ND bulb neck diameter  相似文献   

6.
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7.
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.  相似文献   

8.
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9.
Summary One of the major factors affecting the production and stability of ethylene (C2H4) in soil is its water content. This study was conducted to determine the effect of unsaturated vs. saturated conditions on the production and stability of C2H4 in soil. L-Methionine and D-glucose were added alone and in combination at 1.0 and 5.0 g kg-1 soil, respectively. The addition of l-methionine significantly promoted C2H4 production at field capacity to a much greater extent than under waterlogged conditions. Glucose was equally effective under both moisture regimes, while the combined application of both amendments (l-methionine and d-glucose) led to the release of significantly higher amounts of C2H4 under saturated conditions. Antibiotic experiments revealed that under aerobic conditions, l-methionine may be more efficiently converted to C2H4 by soil fungi, while in glucose-amended soil, both bacteria and fungi are active in generating C2H4. C2H4 was more stable under saturated conditions. The magnitude of C2H4 removal from the headspace after 3 days of incubation under unsaturated conditions (25.7%) was comparable to that after 6 days under saturated conditions (24.1%). The loss of C2H4 was approximately 10-fold greater in non-sterilized soil than in sterilized (autoclaved) soil, both maintained at field capacity, indicating that a biotic component has a major influence on C2H4 stability. Kinetic analysis revealed that the C2H4 loss/degradation in nonautoclaved soil under aerobic conditions followed a firstorder reaction, with a rate constant (k) of 0.115 day-1 and a half-life (t 1/2) of 6.0 days.  相似文献   

10.
Among the treatments of exogenous foliar spray application of sulphates of cobalt (Co) and cadmium (Cd) at 0, 250, 500, 1000, and 1500 ppm, and nickel (Ni) at 0, 100, 200, and 400 ppm prior to flower bud differentiation in the first week of October, cobalt sulphate (1000 ppm) or cadmium sulphate (1500 ppm) significantly (P=0.05) reduced floral malformation of mango (Mangifera indica L) cv. Langra by 65 to 71% and increased the fruit yield by 35 to 37%. The physical characteristics of the fruit were not affected significantly at the lower concentrations but higher concentrations of Co and Cd caused reduction. Total and non‐reducing sugars in the fruit were adversely affected by the higher rates of Co and Ni applied, but exhibited no effect on total soluble solids percentage (TSS%) or reducing sugars. The foliar spray application of the sulphates of Co, Ni, and Cd increased their respective concentrations in the leaf tissue without any phytotoxic symptoms. Most of the desirable effects were achieved with the 1000 ppm cobalt sulphate treatment applied in the first week of October prior to flower bud differentiation.  相似文献   

11.
Regulation of ethylene biosynthesis or action has a major effect on volatiles production in apples. To understand the biochemical processes involved, we used Greensleeves apples from a transgenic line with a high suppression of ethylene biosynthesis. The study was focused at the level of the aroma volatile-related enzymes, including alcohol acyltransferase (AAT), alcohol dehydrogenase (ADH), and lipoxygenase (LOX) and at the level of amino acids and fatty acids as aroma volatile precursors in peel and flesh tissues. In general, volatile production, enzyme activity levels, and precursor availability were higher in the peel than the flesh and were differentially affected by ethylene regulation. AAT enzyme activity showed a clear pattern concomitant with ethylene regulation. Contrarily, ADH and LOX seem to be independent of ethylene modulation. Isoleucine, an important precursor of aroma compounds including 2-methylbutanoate esters, showed a major increase in the peel during ripening and responded significantly to ethylene regulation. Other important aroma volatiles precursors, like linoleic and linolenic acid, showed an accumulation during ripening associated with increases in aldehydes. The significance of these changes in relation to aroma volatile production is discussed.  相似文献   

12.
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.  相似文献   

13.
An improved method has been developed for the determination of ethylene dibromide (EDB; 1,2-dibromoethane) in whole grains, milled grain products, intermediate grain-based foods, and animal feeds. Samples are mixed with water and sparged with nitrogen for 1 h with stirring in a water bath at 100 degrees C. The EDB collected on the adsorbent Tenax TA is eluted with hexane and determined by gas chromatography (GC) with electron capture detection (ECD) and confirmed with Hall electrolytic conductivity detection (HECD) using a second GC column. The highest levels of EDB were also confirmed by full scan GC/mass spectrometry (GC/MS). A total of 24 whole grains, milled grain products, intermediate grain-based foods, and animal feeds analyzed by using this method contained EDB levels up to 840 ppb (wheat). Recoveries from fortified samples ranged from 90 to 105%. Values from this method were compared with those obtained from the acetone soak method; for all 24 samples, this purge and trap method gave equivalent or superior recoveries and detected levels of EDB. Chromatograms for this purge and trap method were clean, enabling a quantitation level of 0.5 ppb to be achieved.  相似文献   

14.
The evolution of C2H4 from soils was stimulated by air-drying, and still more by oven-drying at 105°C. The quantities evolved were closely correlated with organic matter content, with no significant difference in this relationship between grassland and arable soils, or between topsoil and subsoil. In arable soils only, the quantities of C2H4 also increased significantly with decreasing pH. No significant relationship could be found between NO3? concentrations in fresh soils and the quantities of C2H4 evolved, but for air-dried soils (arable only) there was a significant decrease with increasing NO3?. Artificial addition of NO3? only partially inhibited the evolution of C2H4, even at concentrations an order of magnitude higher than those found in the field. At normal soil concentrations the only effect of NO3? seems likely to be a short delay in the achievement of the maximum C2H4 concentrations.  相似文献   

15.
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16.
The application of diphenylamine (DPA) to prevent the apple peel disorder superficial scald can result in accumulation of a number of DPA derivatives resulting from C-nitration, C-hydroxylation, O-methylation, and N-nitrosation during fruit storage. As the presence of these compounds may be indicative of metabolic processes leading to superficial scald development, the contents of DPA and DPA derivatives were determined in fruits treated at harvest with DPA or DPA plus the ethylene action inhibitor 1-methylcyclopropene (1-MCP), which also prevents scald development. Influences of fruit maturity, storage environment, storage duration, and a 14 day poststorage ripening period on accumulation of DPA metabolites were also assessed. Poststorage ripening, 1-MCP treatment, and controlled atmosphere storage had varied effects on DPA derivative contents suggesting that reactive oxygen and nitrogen species, such as *OH, *NO, and *NO2, or enzyme-catalyzed reactions may be present during certain ripening and senescence-related physiological processes. Definitive correlations between superficial scald incidence and contents of specific derivatives were not observed.  相似文献   

17.
Ethylene formation in submerged soils and ethylene degradation by rice roots and soils were investigated. Ethylene was formed in rice soils in amounts which may deleteriously affect the growth of rice seedlings. Ethylene formation was markedly enhanced when organic materials such as glucose or rice straw were added to the soil. The rice roots, especially those taken from lowland and rice fields, showed notable ethylene-degradation activity; the rhizosphere microorganisms of the lowland rice appeared to be responsible for the ethylene-degradation activity. Lowland soils which have been continually submerged for a long time also showed ethylene-degradation activity. Upland soil and soil recently submerged, however, showed little degradation activity.  相似文献   

18.
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.  相似文献   

19.
探索叶面增钙对芒果果实呼吸、乙烯释放及果实矿质元素的影响,为钙肥在芒果生产中的合理应用提供科学理论依据。以"贵妃"芒果为试材,田间试验于2013年10月至2014年6月在海南省东方岛西林场芒果园进行,试验共设置不喷施叶面肥(0 g·L~(-1))、喷施0.5、1.5、2.5、3.5 g·L~(-1)钙含量肥5个处理,各处理3个重复,肥料选择硝酸钙(化学纯)和果蔬钙(Ca 170 g·L~(-1)),于催花前、幼果期、果实膨大期及采收前分别喷施,研究果实呼吸速率、乙烯释放及矿质元素含量变化。研究发现,不施钙处理芒果的果实跃变峰出现在采摘后第13d,叶面增钙使果实跃变峰的出现滞后。在呼吸峰值出现前硝酸钙降低果实呼吸速率,以1.5 g·L~(-1)处理显著降低,峰后有增强呼吸的趋势,在呼吸峰值出现前果蔬钙有提高果实呼吸速率的趋势,峰值出现后有抑制呼吸速率的作用;喷施硝酸钙推迟采后芒果果实进入乙烯跃变期,使跃变峰的出现比CK滞后2 d,峰值过后各处理乙烯释放速率远高于CK,喷施果蔬钙推迟采后芒果果实进入乙烯跃变期,跃变峰的出现有推迟趋势,0.5 g·L~(-1)处理的跃变峰滞后显著,推迟至第17 d;叶施钙肥有使果实K含量降低趋势,以果蔬钙处理显著降低;叶面喷施硝酸钙、果蔬钙均提高果实Ca含量,硝酸钙降低Mg含量,果蔬钙提高Mg含量;叶施硝酸钙使果实Fe、Cu、Zn含量下降,Mn含量提高;叶施果蔬钙使果实Fe下降、Mn提高,低钙提高果实Cu、Zn含量,高钙降低果实Cu、Zn含量。叶面增钙,影响了芒果果实采后呼吸、乙烯释放速率及推迟跃变峰的出现,影响果实部分矿质元素的含量,提高了果实采后贮藏性。  相似文献   

20.
Apricots of two varieties, Ceccona with strong aroma and San Castrese with low aroma but good firmness, were treated with 1 microL L(-)(1) 1-methylcyclopropene (1-MCP) for 12 h at 20 degrees C and then kept for shelf life at 20 degrees C and 85% relative humidity. 1-MCP treatment strongly inhibited ethylene production in apricots of both varieties, and softening was delayed. Fruit softening started before the rise of ethylene in air-treated apricots, which softened even when the rise of ethylene production was inhibited by 1-MCP. The softening reduction was more significant in Ceccona apricots than in San Castrese. Pectinmethylesterase (PME) activity declined in Ceccona fruit regardless of the treatment; in San Castrese, PME of air-treated fruit slightly increased, whereas in 1-MCP-treated apricots the activity declined. alpha-d-Galactosidase (alpha-gal) and beta-d-galactosidase (beta-gal) activities in Ceccona apricot were significantly reduced by 1-MCP treatment, whereas in San Castrese apricot no difference in activities was observed between air- and 1-MCP-treated fruit. The pattern of beta-d-xylosidase (xyl) activity in San Castrese apricot was similar to that of beta-gal, showing a peak on day 4 without difference between treatments. alpha-d-Mannosidase (alpha-man) activity of air-treated apricots of both varieties rose slightly, and 1-MCP treatment decreased the enzyme activity in both varieties. alpha-d-Glucosidase (alpha-glu) decreased in air-treated apricots in both varieties, and 1-MCP maintained higher activity in Ceccona fruit but not in San Castrese. Acidity decreased during postharvest ripening regardless of the treatment, whereas soluble solids content (SSC) increased in Ceccona apricot and slightly diminished in San Castrese ones without any effect by 1-MCP treatment. 1-MCP did not show any effect on apricot color; in contrast, it affected the volatiles profile, especially in Ceccona apricot, reducing the synthesis of lactones and promoting the rise of terpenols.  相似文献   

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