共查询到19条相似文献，搜索用时 218 毫秒
1.
建立了毛细管气相色谱法测定蔬菜水果中28种有机磷农药残留量的分析方法,对实验水果蔬菜经乙腈提取,盐析,浓缩液丙酮溶解定容,采用ENVI-Carb固相萃取小柱净化,以10%丙酮-正己烷混合液洗脱,洗脱液采用DB-17毛细管柱和火焰光度检测器测定,一次进样可对蔬菜水果中28种有机磷农药进行检测,并且通过采用DB-1毛细管柱和氮磷检测器进行确证实验,准确度高。结果表明:样品加标平均回收率在72.8%～102.3%之间,相对标准偏差(RSD)在2.1%～6.6%之间,检出限(LOD)在0.017～0.200mg/kg之间。实验表明,该检测方法简便、快速、灵敏、准确,各项技术指标均能满足农药残留检测的要求,适合蔬菜水果中有机磷农药多残留的日常检验。 相似文献
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建立了一种气相色谱质谱联用同时测定水中49种农药及代谢物残留的方法。样品经二氯甲烷∶丙酮(V/V,1∶1)二次萃取浓缩后,在VF-1701 ms毛细管柱条件下,多反应监测模式,内标法定量,GC-MS-MS上机分析。结果显示：49种农药及代谢物在10～500μg/L质量浓度范围内线性关系良好,线性相关系数均大于0.995,定量限为0.003～0.464μg/L;平均加标回收率在62.6%～116.5%,精密度相对标准偏差在0.8%～12.2%。该方法前处理简单,准确灵敏,回收率高,适合水中多种农药残留的定量分析。 相似文献
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用QuEChERS方法对板栗样品中10种有机磷农药进行前处理优化,建立了板栗有机磷残留量的快速前处理方法,并进行验证。通过对比不同的提取溶剂、取样量、除水剂用量、净化剂用量确定板栗QuEChERS前处理的最佳组合,净化完成后用GC/MS检测。10种有机磷农药的线性相关系数均0.998,最低检出限为0.010~34 mg/kg,平均回收率为80.1%~105.4%,相对标准偏差值为3.5%~8.9%。该方法准确、快速、净化效果好,适用于板栗中多种有机磷农药残留的快速检测。 相似文献
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蔬菜生产使用的化学农药，导致蔬菜中农药残留过高，严重危害了人们的身体健康。而在低温溶氧调频状态下，设计制作的太阳能蔬菜杀菌器是利用太阳能电池板提供电能，通过生物、物理、计算机等技术。进行电子杀虫、物理灭菌，补充蔬菜生长需要多种光照。太阳能蔬菜杀菌器可替代化学农药，提高蔬菜产量，改善蔬菜品质，生产无农药残留的绿色、优质蔬菜。 相似文献
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目前我国使用的农药品种主要为有机磷、氨基甲酸酯和菊酯等。其中有机磷农药已成为我国农药残留急性污染事件的元凶。虽然大多数氨基甲酸酯类农药属中、低毒性,但其中的呋喃丹、涕灭威等却属高毒农药。长期以来农药的大面积使用和滥用,使得农药残留严重威胁到人类食品的安全性。中国科学院大连化学物理研究所开发的便携式荧光探针农药残留检测仪,可满足我国基层部门对农药残留现场检测和农药残留检测室筛选分析的迫切需要。 相似文献
9.
蔬菜种植过程中降低农药残留的方法探讨 总被引：1，自引：0，他引：1
阐述了农药残留对人体的危害.针对当前蔬菜农药残留的现状和存在的安全问题,结合导致农药残留的根本原因进行分析,探讨了蔬菜种植过程中减少农药残留的技术措施. 相似文献
10.
指出了农药的大量使用使得农药残留问题备受关注，而农药分析技术是解决该问题的有效方法，探讨了农药残留分析中的样品前处理和检测分析等方面技术的最新进展。 相似文献
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This study clarified the origin of Al in spring water and stream water by analyzing the size distribution of Al of ground
water, spring water, stream water, and soil extracts obtained by batch and column experiments using samples from a suburban
secondary forest on granite bedrock in Aichi Prefecture. The high concentration of dissolved Al (Al0.45; fraction through 0.45-μm filter) in water samples obtained from this study site was divided into completely dissolved and
small colloidal forms (<0.20 μm; Al0.20) and large colloidal forms (0.20–0.45 μm). More than 50% of dissolved Al (Al0.45) in spring water existed in large colloidal form. By comparing the size distribution and concentration of various elements
including Al in the samples from soil batch and column experiments, we suggest that the high concentration of Al in spring
water is caused by the release of Al from surface soils when ground water emerges as spring water. 相似文献
12.
To study the effect of postcure conditions on the viscoelastic behavior of water-based polymer isocyanate adhesives for wood
(API adhesive), dynamic mechanical analysis (DMA) was performed for a simplified model of API adhesives under various postcure
conditions. These conditions were achieved by storing the samples at room temperature or by heating them in an oven. Fourier
transform infrared (FT-IR) spectroscopy was performed to test for residual isocyanate groups (NCO) and isocyanate derivatives
to elucidate the reaction mechanism under the postcure conditions. DMA revealed that the postcure conditions led to wide variations
in the viscoelastic behaviors of API films. FT-IR analysis confirmed the decrease of residual isocyanate during postcure treatments.
However, the complete consumption of isocyanate could not be achieved under the postcure conditions. A good correlation was
found between the DMA result and the chemical changes in the API samples heated above 140°C. However, no correlation was observed
in the case of the samples heated at temperatures less than 140°C. This implies that postcure conditions led to a difference
in the reaction chemistry of API.
Part of this article was presented at the 55th Annual Meeting of the Japan Wood Research Society, Kyoto, March 2005 相似文献
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Eight different residual lignins isolated from unbleached chemical pulps [sulfite, kraft, alkaline sulfite-anthraquinone-methanol
(ASAM), soda/AQ/MeOH] of spruce and beech were characterized using gel permeation chromatography (GPC), thioacidolysis, and
desulfurization to determine average molecular weight, amounts of uncondensed β-O-4 linkages, and dimeric linkage patterns, respectively. The total amounts of G-CHSEt-CHSEt-CH2SEt and S-CHSEt-CHSEt-CH2SEt were markedly reduced in residual lignins to 40% to 80% of the values for the corresponding milled wood lignins (MWLs).
The number of dimeric units determined by thioacidolysis and desulfurization of the residual lignins was decreased by onehalf
to one-fifth compared to the MWLs. Among the diverse types of dimeric units, reduction of β-1 and β-5 units was significant in most of the residual lignins, with the exception of beech ASAM residual lignin. Compared to beech
MWL, 40% more C6–C3 main monomers were detected, whereas the relative composition of the dimeric units in the beech residual
lignin was very similar to that in the beech MWL. The average molecular weights of residual lignins were less than those of
the MWLs. However, the average molecular weights of the spruce kraft and soda residual lignins were determined to be higher
than those of the corresponding MWLs. 相似文献
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I. L. Post J. C. Atherton C. P. Vendhan Professor R. R. Archer 《Wood Science and Technology》1980,14(4):289-296
Summary Previous methods for measuring residual longitudinal growth strain distributions in logs are reviewed. An extension is given of Jacobs' method for measuring growth strains which yields residual strain information at many points in the cross section other than along the diametrical plank. Some of the longitudinal growth strain distributions measured using the new method are presented.This work was supported in part by NSF Grant ENG-74-02428 相似文献
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预应力砼箱型连续梁支架法现浇施工技术 总被引：1，自引：0，他引：1
按满布支架法和梁柱支架法分别提出了混凝土箱梁现浇施工中易被忽视的问题,并建立了受力分析模型,阐明了分次浇筑预应力混凝土箱梁会在混凝土内产生残余应力,可通过选择合理的施工方法和浇筑顺序减小残余应力。 相似文献
16.
黄水是白酒在固态发酵过程的副产物,含有大量发酵产物,黄水的成分一定程度反映了固态发酵的信息。基于白酒固态发酵只能在线检测温度这一现状,设计了针对白酒副产物黄水的一种传感器阵列检测装置,用于检测黄水的总酸和残余葡萄糖。该传感器阵列由电导率传感器、pH传感器和氧化还原传感器构成。采用主成份分析、判别函数分析印证了传感器数据对不同样品的区分作用,再采用多元线性回归对黄水样品建立了预测模型,结果显示:该传感器阵列装置对黄水的总酸和残余葡萄糖的预测偏差分别为0.39和0.45。 相似文献
17.
研究区域位于天然林保护工程重点区域大兴安岭林区,收集大兴安岭森林资源连续清查第6次复查232块样地资料,将其整理成列联表,做列联表分析,进行卡方检验、剩余分析、对数线性模型拟合。结果表明,此区域落叶松林分在低海拔分布较广,但蓄积量处于相对低水平,主要是此区域内林分受人为干扰较严重而致。本文研究结果对于森林经营决策具有重要的意义。 相似文献
18.
For analysis of carbon isotope discrimination in wood, cellulose or holocellulose is often preferred to whole tissue because of the variability in isotopic composition of different wood components and the relative immobility of cellulose. Most currently used methods for the preparation of wood components for stable isotope analysis (e.g., the Jayme-Wise method) produce a residue of holocellulose. The Jayme-Wise method was initially developed to extract holocellulose from small (~1 g) samples of wood, and, despite subsequent modifications, the method requires specialized glassware, considerable time and entails the risk of sample loss. For carbon isotope analysis, we adapted an acid-catalyzed solvolytic method for preparing crude cellulose by treating wood meal with acidified di-glycol methyl ether (diglyme). The one-step process requires no special glassware, is complete within 24 hours and enables over 100 samples to be processed in a day. This method gives similar delta(13)C values to the Jayme-Wise method for wood of Eucalyptus globulus Labill., Pinus radiata D. Don and Pinus pinaster Ait. The relationship between delta(13)C of wood and crude cellulose is as strong as that observed between wood and alpha-cellulose and stronger than that observed between wood and holocellulose in other species. These relationships suggest that variation in delta(13)C of wood may result from hemicellulose and that analysis of stable carbon isotopes in crude cellulose is preferable. If the consistent -0.3 bias in the value of delta(13)C of cellulose resulting from residual lignin is corrected for, then the relationship between delta(13)C of wood and crude cellulose may be used to predict delta(13)C of cellulose from a small sub-sample. The method is well suited to species with low concentrations of extractives, but further testing is needed to assess its general applicability. 相似文献
19.
In our preceding study, we clarified that liquids having similar molecular sizes to ethanol were mainly adsorbed onto lignin
among the major constituents of wood. This suggests that most micropores or adsorption sites loosely hydrogen-bonded to each
other, which are accessible to these liquids, exist in lignin. In the present study, to examine micropores in wood and lignin,
micropore distribution was measured by CO2 gas adsorption at ice-water temperature (273 K). Dry samples prepared by gradual delignification from wood meal were used
as adsorbents. The pore-size distributions were determined by analyzing adsorption isotherms using the Horvath-Kawazoe method.
It was found that the number of micropores decreased with the decrease in residual lignin, and micropores were hardly found
in cellulose and hemicellulose. It is considered that most micropores smaller than 0.6 nm in wood exist in lignin. 相似文献