伏安法结合化学计量学测定食品中的香兰素和乙基麦芽

实验采用微分脉冲溶出伏安法(DPSV)对食品中的香兰素和乙基麦芽酚进行同时测定。在pH=10.12的Britton-Robinson缓冲溶液中这2种增香剂都具有峰型良好的氧化峰,在最佳的实验条件下香兰素和乙基麦芽酚的线性范围分别为0.40～6.40、0.20～7.60μg.mL-1,检测限分别为0.28、0.11μg.mL-1。由于这2种增香剂的峰电位相近,所得伏安曲线重叠严重,不经分离难以进行同时测定。本实验将主成分回归法(PCR)、偏最小二乘法(PLS)、一阶导数-主成分回归(DPCR)及一阶导数-偏最小二乘法(DPLS)处理它们的重叠伏安波谱数据并进行定量分析,发现主成分回归法可建立稳定的校正模型并获较好的定量结果。建立的方法用于食品中的2种增香剂的测定,并与高效液相色谱法进行了对照,可获得可靠的定量分析结果。     

化学计量学-分光光度法同时测定成年男子精液中的钙、镁、锌

在pH10．4的硼砂-NaOH缓冲体系中,2-(8′-羟基喹啉-5′-磺酸-7′-偶氮)变色酸(8Q5SAC)能分别与钙、镁、锌形成络合物。它们的光谱均在400～800nm波长范围内,且相互重叠。本文应用主成分回归法、偏最小二乘法和径向基人工神经网络法处理测量数据,建立数学模型,并对一组人工合成试样作浓度预报,发现径向基人工神经网络法能给出最好的结果,钙、镁和锌测定的RSD分别为3．4％、3．0％、3．2％。将此法用于一患不育症成年男子和一正常成年男子精液中的钙、镁、锌同时测定,荻较好结果。     

HPLC测定酱油中的有机酸及其聚类分析

建立了高效液相色谱法测定酱油中有机酸的方法,该方法的样品前处理简单,甲酸、苹果酸、琥珀酸、乳酸、酒石酸、乙酸、柠檬酸、丙酮酸、乙酰丙酸在弱阳离子交换柱上分离效果良好。各有机酸在0.10~20.0 mg/mL范围内,用本方法测定的相关系数均在0.999 0以上,回收率为(96.0~103.9)%     

THE EXPLICIT SOLUTION OF HOMOGENEOUS LINEAR ORDINARY DIFFERENTIAL EQUATIONS WITH CONSTANT COEFFICIENTS

In this paper by using tensor analysis we give the explicit expressions of the solution of the initial-value problem of homogeneous linear differential equations with constant coefficients and the n th-order homogeneous linear differential equation with constant coefficients. In fact, we give the general formula for calculating the elements of the matrix exp[At]. We also give the results when the characteristic equation has the repeated roots. The present method is simpler and better than the other methods.     

THE ADSORPTION OF Ge ON GaAS(ll0)

In the present work, the chemisorption of Ge on GaAs(1lO) was studied by a cluster model using the charge self-consistent extended H ückel method (EHT) and the results thus obtained were compared with those derived from the experiments. It was shown from the calculation that after chemisorption, the substrate tends to relax back to the ideal unrelaxed state, after cleavage. The tilted angle of the As-Ga bond was reduced from the well khown 27° to 10°.The gap states which were driven into both the valence band and the conduction band due to relaxation will-be introduced into the gap after chemisorption. From the calculation of the total energy of the cluster, it was found that the Ge atom could bind to both Ga and As atoms although the binding of the latter was somewhat stronger. The gap states were derived from the p states of Ge and the s and p states of Ga and As atoms. The states will serve as donors and acceptors for p and n type materials respectively . From a comparison with the previous results concerning studies of group Ⅲ and Ⅴ metals on GaAs(110) surface, it seems that the change of surface relaxation after chemisorption might be the origin of gap states and the cause for Fermi level pinningr. The explanation was first put forward by Chen et al . from their experimental studies . The present calculation also gives the core shifts of Ga(3d) and As(3d) of the clean relaxation surfaces with respect to that of the bulk as well as the core shifts of Ga(3d) and As(3d) after the chemisorption of Ge atom. A chemisorption induced state which is attributed to a precursor state for a heterojunction interface state is also obtained at a binding energy near 7eV which is in fairly good agreement with the experimental result.     

具有种内互惠作用的Lotka—Volterra捕食模型

对具有种内互惠作用的Ｌｏｔｋａ－Ｖｏｌｔｅｒｒａ捕食-食饵模型进行了完整的全局分析,得到了一些新的有趣的结果．     

石墨烯修饰的电极对对氨基苯酚和对乙酰氨基酚进行同时测定

利用石墨烯修饰的玻碳电极采用微分脉冲伏安法对对氨基苯酚和对乙酰氨基酚进行同时测定.实验证明在pH=5.72的Britton-Robinson(B-R)缓冲溶液中这两种物质都具有良好的氧化峰,在修饰电极上两物质的伏安峰能够很好地分开,因此可以直接对这两种物质进行同时测定.在最佳实验条件下对氨基苯酚和对乙酰氨基酚的线性范围分别为0.1～1.8,0.2～2.2 mg·mL-1,两者的检测限分别为0.067,0.074mg·mL-1.利用本文提出的方法对血清实际样中的对氨基苯酚和对乙酰氨基酚进行测定,可得较高的回收率.     

在玻碳电极上用微分脉冲溶出伏安法检测盐酸甲氧氯普胺

在pH3.29的Britton-Robinson缓冲溶液中,盐酸甲氧氯普胺在E=1150 mV (vs.Ag/AgCl ) 处具有良好电化学氧化峰,本实验采用循环伏安法和线性扫描溶出伏安法等对该体系进行研究,发现采用线性扫描溶出伏安法时能得到较大的灵敏度,电极反应呈不可逆现象,并具有一定的吸附性,在30 s时能达到吸附平衡.该体系的伏安波谱峰电流与浓度成正比,线性范围为1.2～25 μg/mL,检出限为0.44 μg/mL.利用该方法对针剂样品中的盐酸甲氧氯普胺进行直接测定,获得了较好的定量分析结果.     

电化学分析在有机农药残留量分析中的应用

对近二十年来电化学分析方法在农药残留量分析中的应用进行了综述，对有机氯农药、有机磷农药、有机氮农药、有机硫农药及有机除草剂展开了评述，并对化学计量学在该领域中的应用作了讨论。     

Superposition about the 3D vortex solutions of the fluid dynamic equation

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