香蕉中噻唑膦残留分析方法研究

建立香蕉中噻唑膦的超高效液相色谱串联质谱法(UPLC-MS/MS)残留测定方法。香蕉样品采用乙腈提取和PSA+C18分散固相萃取,采用UPLC-MS/MS多反应模式(MRM)进行分析测定。噻唑膦在添加水平0.01~1.0 mg/kg范围内,平均回收率为94.3%~107.5%,相对标准偏差为7.9%~11.0%。采用外标法定量,方法的检出限为0.001μg/m L,定量限为0.005 mg/kg。该方法简单、准确、重复性较好且节省溶剂,适用于香蕉中噻唑膦的残留检测。     

Compatible measurements of volumetric soil water content using a neutron probe and Diviner 2000 after field calibration

Field calibrations for a neutron probe and a capacitance sensor (Diviner 2000) for measuring the soil water content of a shrinking–swelling clay soil were substantially different from commonly used default values. Using our field calibrations, the two instruments estimated similar changes in the cumulative water content of a soil profile (0–1 m depth) over one growing season.     

Pedotransfer functions to assess adsorbed phosphate using iron oxide content and magnetic susceptibility in an Oxisol

Adsorbed phosphate in soils can be chemically extracted; however, this process is both time‐consuming and not cost‐effective if large numbers of samples have to be analysed. Indirect assessment of adsorbed phosphate by pedotransfer functions (PTFs) can help optimize fertilizer strategies. This study aimed to evaluate the spatial variability of adsorbed phosphate (P_ads), iron oxides and magnetic susceptibility (MS) in oxisols and to calibrate PTFs to predict P_ads. A total of 308 soil samples were collected from Hapludox and Eutrudox soils formed from sandstone in Brazil. The contents of clay (196–607 g/kg), iron oxides (40–165 g/kg), MS (1.2–29 × 10^?6 m³/kg) and P_ads (327–842 mg/kg) were in the range of typical values for these highly weathered soils. This study showed that the attributes studied were spatially dependent. Geomorphic surfaces enabled understanding of spatial variability and helped to develop a more efficient sampling scheme to calibrate PTFs. Moreover, the adsorbed phosphate in these oxisols could be predicted by a PTF using iron oxides and MS as predictors. The MS attribute enabled the most accurate prediction (concordance coefficient = 0.95, root‐mean‐square error = 46 mg/kg and relative improvement in root‐mean‐square error = ?4.12) of spatial variability through PTF compared to other predictors.     

Turbidity‐induced changes in emergent effects of multiple predators with different foraging strategies

Abstract – In natural systems, prey frequently interact with multiple predators and the outcome often cannot be predicted by summing the effects of individual predator species. Multiple predator interactions can create emergent effects for prey, but how those change across environmental gradients is poorly understood. Turbidity is an environmental factor in aquatic systems that may influence multiple predator effects on prey. Interactions between a cruising predator (largemouth bass Micropterus salmoides) and an ambush predator (muskellunge Esox masquinongy) and their combination foraging on a shared prey (bluegill Lepomis macrochirus) were examined across a turbidity gradient. Turbidity modified multiple predator effects on prey. In clear water, combined predators consumed in total more prey than expected from individual predator treatments, suggesting risk enhancement for prey. In moderately turbid water, the predators consumed fewer prey together than expected, suggesting a risk reduction for prey. At high turbidity, there were no apparent emergent effects; however, the cruising predator consumed more prey than the ambush predator, suggesting an advantage for this predator. Understanding multiple predator traits across a gradient of turbidity increases our understanding of how complex natural systems function.     

分散固相萃取结合UPLC-Orbitrap MS联用测定鸡蛋中五氯苯酚残留量

建立了超高效液相色谱-静电轨道阱质谱联用测定禽蛋中五氯苯酚残留量的分析方法。取均质后的禽蛋样品经乙腈溶液提取,加入无水硫酸镁和氯化钠进行脱水和盐析,高速离心分层后,取适量乙腈层溶液经0.1%(V∶V)甲酸稀释后,用酸性氧化铝粉末进行样品净化并以10000 r/min离心取上清液,过0.22μm滤膜后上机测定。使用反相色谱柱进行分离,流动相为乙腈:0.1%甲酸=75∶25,采用等度程序进行洗脱,静电轨道阱质谱进行定性定量分析。结果表明,五氯苯酚在0.5~100μg/kg范围内线性关系良好(r>0.995),方法的最低检出限为0.2μg/kg,最低定量限为0.5μg/kg,添加回收率在74.43%~96.85%之间,批内批间变异系数CV%<10%。该方法具有较好的准确度与精密度,适用于禽蛋中五氯苯酚残留量的测定。     

利用分散液-液微萃取和反相高效液相色谱-荧光检测器测定硒蛋白多糖中硒含量

本试验介绍了一种利用分散液-液微萃取前处理并将一种新型反相色谱柱应用于高效液相色谱-荧光检测器(HPLC-FLD)测定硒蛋白多糖中硒含量的方法。该方法以2,3-二氨基萘(DAN)为螯合剂,400μL乙腈为分散剂,120μL氯苯为萃取剂,硒(Ⅳ)与2,3-二氨基萘的螯合物(Se-DAN螯合物)经乙腈稀释后进行高效液相色谱分析。采用PFP色谱柱分离,乙腈为流动相,用荧光检测器在激发波长为376 nm、发射波长为520 nm条件下测定荧光强度,外标法定量。结果显示:该方法成功地用于测定硒蛋白多糖中硒含量,硒的检出限为2.5μg/L,线性范围为5.0~250.0μg/L。采用该方法测定的硒蛋白多糖中硒含量为1337.0μg/g,与荧光分光光度法(国标法)测定结果高度一致;并且,该方法也适用于酵母硒中硒含量的测定。本试验成功建立了检测硒蛋白多糖中硒含量的方法,该方法具有操作简便、易普及、试剂消耗少、分离度好、回收率高和适用性强等特点。     

A comparison between X‐ray fluorescence and dissolution methods employing lithium metaborate fusion for elemental analysis of soil clays

Abstract

A method employing fusion of soil clay samples with lithium metaborate (1:5 ratio) in a furnace at 1050°C for 1 hr. subsequent dissolution of the fused sample in 4% HNO₃. and elemental analysis for Si, Al, Fe, Ca, Mg, K, and Ti by atomic absorption spectrometry was compared with the X‐ray fluorescence (XRF) fused disc technique for analysis. Duplicated analyses were performed on 15 clay samples from soils of the southern U.S and three API reference samples. The mean total percent recovery by this method was excellent (100.14 ± 2.85). Elemental oxide quantities in terms of SiO₂. Al₂O₃, Fe₂O₃, MgO, CaO and K₂O determined by atomic absorption/flame emission (AA/FE) spectroscopy were in good agreement with values measured by x‐ray fluorescence (XRF) on the same subsamples (r = 0.89^* to 0.98^**). but somewhat more variable on subsamples seperated from different pretreatments (r = 0.70^* to 0.97^** ). The method, which has also been tested on 36 additional clay samples from a variety of Kentucky soils with total percent recoveries ranging from 96.5 ‐ 103.5%. demonstrated no bias due to mineralogy with respect to mixed, montmorillonitic. and siliceous classes. This technique presents numerous advantages over other elemental analysis techniques utilizing fusion, dissolution, or XRF spectroscopy with respect to time, effort and cost. With the introduction of inductively‐coupled plasma (ICP) emission spectroscopy. efficiency can be additionally improved.     

Evaluation of uncalibrated preferential flow models against data for isoproturon movement to drains through a heavy clay soil

The uncalibrated predictive ability of four preferential flow models (CRACK‐NP, MACRO/MACRO_DB, PLM, SWAT) has been evaluated against point rates of drainflow and associated concentrations of isoproturon from a highly structured and heterogeneous clay soil in the south of England. Data were available for four plots for a number of storm events in each of three successive growing seasons. The mechanistic models CRACK‐NP and MACRO generally gave reasonable estimates of drainflow over the three seasons, but under‐estimated concentrations of isoproturon over a prolonged period in the first season and over‐estimated them in the two remaining seasons. CRACK‐NP simulated maximum concentrations of isoproturon over the first two events of each of the three seasons of 156, 527 and 24.4 µg litre^?1, respectively, and matched the observed data (465, 65.1 and 0.65 µg litre^?1) slightly better than MACRO (69.1, 566 and 58.5 µg litre^?1). Automatic selection of parameters from soils information within MACRO_DB reduced the emphasis on preferential flow relative to the stand‐alone version of MACRO. This gave a poor simulation of isoproturon breakthrough and simulated maximum concentrations were 0, 50.1 and 35.1 µg litre^?1, respectively. The capacity model PLM gave the best overall simulation of total drainflow for the first two events in each season, but over‐estimated concentrations of isoproturon (967, 808 and 51.3 µg litre^?1). The simple model SWAT represented total drainflow reasonably well and gave the best simulation of maximum isoproturon concentrations (140, 80.2 and 8.2 µg litre^?1). There was no clear advantage here in using the mechanistic models rather than the simpler models. None of the models tested was able to simulate consistently the data set, and uncalibrated modelling cannot be recommended for such artificially drained heavy clay soils. © 2001 Society of Chemical Industry     

三唑酮种衣剂对小麦白粉菌侵染和非侵染位点硅等元素含量的影响

 借助扫描电子显微镜-X射线能谱分析方法从超微结构和元素水平观测了三唑酮种衣剂包衣处理和空白对照的小麦幼苗上白粉病菌侵染及非侵染位点硅等元素含量的变化。结果表明,接种后20~36 h内三唑酮种衣剂处理的麦苗侵染位点细胞内元素硅含量由5.204%上升为42.064%,非侵染位点由5.821%上升为12.342%;空白对照中侵染位点元素硅含量由低于检测水平上升为17.388%,非侵染位点接种后36 h时为19.460%。在处理和空白对照的麦苗上侵染和非侵染位点均检测到了含量不等的磷、硫、氯等元素存在。     

日本三节叶蜂分散繁殖的观察

本文较系统观察了日本三节叶蜂Arge niponicus (Rohwer) (膜翅目:叶蜂科)成虫的羽化对策.结果表明,5月中旬作茧的个体能分散在335d内羽化,即:29.6%非滞育的茧的羽化期出现在6月;68.3%的越夏茧的羽化期出现在7月21日至9月21日;2.1%越夏-越冬的茧羽化期出现在第二年的4月.揭示了该虫在生活史上有明显的分散繁殖现象.