高效液相色谱荧光法测定水产品中四环素类残留量

[目的]建立应用高效液相色谱荧光法测定水产品中四环素类药物残留量方法.[方法]通过对水产样品的提取、净化研究及仪器条件的选择和优化,采用荧光检测器一次测定痕量土霉素、四环素和金霉素.[结果]方法的检出限土霉素(OTC)0.005 mg/kg;四环素(TC)0.005 mg/kg;金霉素(CTC)0.010 mg/kg.加标回收率土霉素(OTC)61.0%～78.2%;四环素(TC)81.4%～83.0%;金霉素(CTC)69.0%～73.8%.[结论]本方法样品前处理简单,灵敏度高,能满足各国对水产品中四环素类药残检测低限的要求.     

HPLC法测定辣椒及其制品中苏丹红色素含量

[目的] 建立辣椒及其制品中4种苏丹红(sudan)色素的高效液相色谱同时测定方法.[方法] 采用反相高效液相色谱法,以乙腈-酸性水溶液为流动相,采用梯度洗脱,以二极管阵列检测器(PDA)定性定量测定辣椒制品中的4种苏丹红色素,并以LC-MS对阳性样品中的苏丹红成分进行了结构确证.[结果] 在添加浓度1～4mg/kg范围内,4种苏丹红色素的回收率在 81.92%～97.87 %之间,相对标准偏差(RSD)≤5.23%,最低检出限(信噪比S/N=3)分别为0.102、0.097、0.074、0.099mg/kg.[结论] 本方法经实际应用证明,具有良好的稳定性和重现性,步骤简单、可操作性强.     

猪肉中克伦特罗、沙丁胺醇、土霉素、四环素残留量的HPLC同时测定方法研究

[目的]建立高效液相色谱法(HPLC)同时测定猪肉样品中克伦特罗、沙丁胺醇、土霉素、四环素残留量的检测方法.[方法]样品用0.01 mol/L EDTA-2Na、0.3%磷酸溶液、高氯酸(1:1)混合溶液提取,上清液过C18固相萃取柱净化,采用高效液相色谱分离,二极管阵列检测器(DAD)检测,外标法定量.[结果]克伦特罗、沙丁胺醇在0.04～10μg/mL范围内线性关系良好.相关系数为0.99992～0.99993.在0.001～0.05mg/kg添加浓度范围内,平均回收率在70.3%～94.3%之间,相对标准偏差为1.52%～5.85%,土零素、四环素在0.5～10μg/mL范围内线性关系良好,相关系数为0.99993～0.99997.在0.02～0.5mg/kg添加浓度范围内,平均回收率在64.1%～94.2%之间,相对标准偏差为1.23%～4.53%.[结论]本法简便、快速、定量准确、精密度商.适用于猪肉样品中克伦特罗,沙丁胺醇、土霉素、四环素残留量的同时检测.     

固相萃取-液相色谱法测定水产品中孔雀石绿结晶紫及其代谢产物

[目的]建立水产品中孔雀石绿、结晶紫及其代谢产物隐性孔雀石绿、隐性结晶紫的高效液相色谱分析方法.[方法]样品以乙酸钠-乙腈为提取剂,经二氯甲烷反提取、再经SPE柱净化、氰基柱分离和柱后衍生化、等度洗脱、HPLC-DAD测定、外标法定量.[结果]各标准曲线相关系数均≥0.999,2μg/kg4μg/kg浓度水平加标回收率为70.0%～87.7%,RSD为4.9%～8.1%,检测低限均为2μg/kg.[结论]本法简便、快速,具有良好的重现性和准确性.     

婴幼儿配方奶粉中氯霉素残留的酶联免疫分析法

[目的]建立测定婴幼儿配方奶粉中氯霉素残留的酶联免疫分析法.[方法]用乙酸乙酯对样品中的氯霉素残留进行提取,用酶联免疫试剂盒进行检测.[结果]方法检测低限为0.075μg/kg;在0.1μg/kg和0.3μg/kg两个添加水平,样品加标回收率分别为85%～120%和91%～119%;重复性试验CV%分别为6.35%和5.31%;重现性试验CV%分别为11.88%和12.92%.[结论]本方法灵敏度、准确度和精密度均符合残留分析质量控制的要求,适用于婴幼儿配方奶粉中氯霉素残留的快速检测.     

微波萃取-HPLC法测定电子电气产品中的多氯萘

[目的]建立了微波萃取法提取-HPLC法检测电子电气产品中的多氯萘的方法。[方法]样品以甲苯为溶剂经微波萃取法提取、硅胶小柱净化、浓缩后采用高效液相色谱法测定,以外标法进行定量。[结果]方法检测低限为2.5 mg/kg,测定结果的相对标准偏差为2.9%-5.2%,回收率为74.2%-96.8%。[结论]本文所用方法操作简便、快速、准确,对实际样品的检测结果满意。     

高效液相色谱法和高效液相色谱-质谱/质谱法测定荔枝中对氯苯氧乙酸（钠）

建立了荔枝中对氯苯氧乙酸（钠）残留量的液相色谱和液相-串联质谱检测方法,采用碱性水提取,利用二氯甲烷液液萃取进行净化,用液相色谱方法在280 nm检测,检出限为0.02 mg/kg。在负离子模式下进行液质串联质谱检测,检出限为0.01 mg/kg。本方法的添加回收率在78.2%～106.7%,变异系数为2.0%～12.2%。回收率、检测限等技术参数均能满足相关检测要求。本方法应用于65个实验样品的检测,其中有两个样品为阳性,含量分别为0.032 mg/kg及0.026 mg/kg。     

GC—MS法测定大豆蛋白粉中乙草胺残留量

[目的]建立测定大豆蛋白粉中乙草胺残留的方法.[方法]采用气相色谱-质谱测定法,样品中乙草胺用乙腈提取,经中性氧化铝和氟罗里硅土混合柱净化后,采用HP-5MS石英毛细管柱于气相色谱-质谱仪进行测定.[结果]实验采用添加法测定回收率,添加水平为0.005mg/kg～0.5mg/kg时,其平均回收率为91.2%～95.8%.本方法的最低检出限为测定0.005mg/kg.[结论]本方法灵敏度高,速度快,重复性好.     

水产品中氯霉素残留的放射免疫分析

[目的]建立CharmⅡ放射免疫系统测定水产品中氯霉素残留的分析方法.[方法]用CharmⅡ检测氯霉素残留试剂盒中的MSU萃取缓冲液,对样品中的氯霉素残留进行提取,通过竞争性受体免疫反应,采用液体闪烁计数仪计数.[结果]方法检测低限为0.15μg/kg;在0.15μg/kg、0.3μg/kg、1μg/kg3个添加水平,样品的cpm读数均落在相应控制点60%～100%的范围内;cpm读数的相对标准偏差为2.4%～8.8%.[结论]本方法灵敏度、准确度和精密度、选择性均符合残留分析质量控制指南的要求,适用于水产品中氯霉素残留的快速检测.     

进出口中成药中黄曲霉毒素检测方法的研究

[目的] 建立免疫亲和柱-溴化荧光分光光度法检测中成药中黄曲霉毒素总量的常规方法和免疫亲和柱高效液相色谱法检测检测黄曲霉毒素B1、B2、G1、G2的确认方法.[方法] 采用免疫亲和柱(IAC)净化、柱后光化学衍生的高效液相色谱/荧光检测器技术(HPLC/FLD)及溴化荧光光度法(BFS)分别测定两种中成药(水丸和蜜丸)中的黄曲霉毒素B1、B2、G1、G2及其总量.[结果] IAC-HPLC/FLD法平均回收率为86.2%;最低检出限1.0μg / kg;BFS法平均回收率为92.1%;最低检出限1.0μg/kg.[结论] 本方法检测结果尚未发现假阳性现象,假阴性率为零.     

自由贸易与贸易保护主义——公平与效率问题

当今世界 ,贸易自由化成为世界经济发展的主流 ,降低关税和非关税壁垒成为各国双边和多边谈判的主要议题。自由贸易与贸易保护主义的争论由来已久 ,自由贸易的效率以及产生的不公平问题用“补偿原则”来解决是存在局限性的 ,所以 ,自由贸易和贸易保护主义之间政策的权衡十分必要。解决贸易自由化中不公平的问题应从政府制定规则、完善社会保障和建立社会道德标准三方面加以着手。     

INNOVATION AND GROWTH WITH RICH AND POOR CONSUMERS

This work studies the impact of income inequality on the level of innovative activities in a model where innovations result in quality improvements. In contrast to the standard model of innovations and growth, the equilibrium outcome may be characterized by a situation where not only the quality leader but also producers of worse qualities are on the market. In that case the quality leader sells to the rich, whereas the producer of the second‐best quality sells to the poor. In general, we find that a more equal distribution of income is favourable for innovation incentives. This is consistent with empirical evidence suggesting that countries with a more equal distribution of income have grown faster.     

OPTIMAL CONSUMPTION AND PORTFOLIO SELECTION WITH INCOMPLETE MARKETS AND UPPER AND LOWER BOUND CONSTRAINTS

We study an optimal consumption and portfolio selection problem for an investor by a martingale approach. We assume that time is a discrete and finite horizon, the sample space is finite and the number of securities is smaller than that of the possible securities price vector transitions. the investor is prohibited from investing stocks more (less, respectively) than given upper (lower) bounds at any time, and he maximizes an expected time additive utility function for the consumption process. First we give a set of budget feasibility conditions so that a consumption process is attainable by an admissible portfolio process. Also we state the existence of the unique primal optimal solutions. Next we formulate a dual control problem and establish the duality between primal and dual control problems. Also we show the existence of dual optimal solutions. Finally we consider the computational aspect of dual approach through a simple numerical example.     

ENTRY AND EXIT OF FIRMS AND UNDEREMPLOYMENT EQUILIBRIUM

This paper extends the standard Keynesian model of aggregate demand and supply allowing for imperfect competition, variable returns to scale, and entry and exit of firms. It distinguishes three phases of macroeconomic equilibria, stagnant, expansive and contractive, according to whether the number of firms is fixed or endogenously determined by the position of the aggregate demand curve. Using this model we show that a large shift in the aggregate demand affects the structure of the economy irreversibly and that the real wage or labor productivity may move procyclically rather than anticyclically. We also elucidate the asymmetric effects of fiscal and monetary policies on the entry of firms and employment.     

论货币与金银货币

关于货币产生过程 ,理论界根据马克思的《资本论》 ,普遍认为应划分为四个阶段 ,把货币阶段与金银货币阶段等同起来 ,认为货币即金银货币。本文提出了新观点 :认为根据有关的资料 ,也可以把货币的产生过程划分为五个阶段 ,不把货币与金银货币划等号 ,认为货币的产生应早于金银货币 ,并阐明了提出以上新观点的依据。     

DEFAULT RISK AND DIVERSIFICATION: THEORY AND EMPIRICAL IMPLICATIONS

Recent advances in the theory of credit risk allow the use of standard term structure machinery for default risk modeling and estimation. The empirical literature in this area often interprets the drift adjustments of the default intensity's diffusion state variables as the only default risk premium. We show that this interpretation implies a restriction on the form of possible default risk premia, which can be justified through exact and approximate notions of "diversifiable default risk." The equivalence between the empirical and martingale default intensities that follows from diversifiable default risk greatly facilitates the pricing and management of credit risk. We emphasize that this is not an equivalence in distribution, and illustrate its importance using credit spread dynamics estimated in Duffee (1999) . We also argue that the assumption of diversifiability is implicitly used in certain existing models of mortgage-backed securities.     

SIMPLE PROCESSES AND THE PRICING AND HEDGING OF CLIQUETS

For data on market prices for 246 cliquets we consider pricing these exotic options using a relatively simple path space. The path space is subsequently stressed to market implied stress levels as well as stress levels predicted from contract characteristics. An additive process transitioning from a Sato process to a Levy process is formulated and estimated on vanilla options. Ask prices constructed from predicted stress levels are observed to have an in sample correlation of 92% with market prices. Interestingly, it is observed that capped cash flows have negative stress levels while uncapped products have positive stress levels. We illustrate the effect of hedging cliquet liabilities using call options as hedging assets permitting a 10% reduction in ask prices.     

电子政务与电子商务的同构与协同

本文基于电子政务与电子商务的基本内涵,详细分析了二者的"同构"、交集与关联,阐述了二者协同发展的思路和途径.本文分析了电子政务与电子商务的支撑体系(信用管理体系、法律环境、标准体系、基础管理体系等)的"同构"性、电子政务与电子商务在对外服务方面上的的交叉部分,以及电子政务与电子商务互促互进共同繁荣的发展路径和远景思路.     

INFORMATION AND INTERRELATIONS BETWEEN THE DEALER AND PRIVATE MARKETS

A competitive equilibrium model of the dealer and private markets is constructed where buyers in the private market obtain some but imperfect information about quality by observing some characteristic of the good while those in the dealer market have perfect information. Under some conditions, there may exist two equilibria. It is shown that one equilibrium is unstable and Pareto inferior to the other. Comparative static analysis are made in the Pareto superior equilibrium to conclude that the size of the dealer market is inversely related to the amount of information about quality contained in the observable characteristic.     

我国石油天然气会计存在的问题及其改进

统一的会计制度不能够反映石油天然气会计的特殊性,海外上市的石油公司虽然采用国际通用的成果法,但在某些具体处理上仍然存在缺陷。为提高会计信息的决策相关性,应在储量信息报告等诸多方面对我国的石油天然气会计予以完善