影响白砂糖色值测量结果的原因探讨

研究了水质、滤膜、溶液浓度、糖液ｐＨ值、混浊度的变化与白砂糖色值的关系。研究结果表明，溶液的ｐＨ变化影响最严重。不调整糖液ｐＨ与用ＨＣｌ或ＮａＯＨ调整糖液ｐＨ对比所得白砂糖色值的结果是满意的。标准偏差１１２～１８６，相对标准偏差１１６％～２２５％，调ｐＨ使结果偏高，导致产生系统误差。因此：测定白砂糖色值不宜调整糖液的ｐＨ。     

Tests for liquid chromatographs

Summary The paper describes tests for liquid chromatographs to assess the autosampler and pump flow rate precision; suitability of the instrument for normal phase chromatography; UV detector performance; and external band broadening characteristics. Tests for mixing and proportioning characteristics of solvent pumps and performance of diode array detectors are also considered. These tests are designed to evaluate the performance of both newly released liquid chromatography equipment and equipment already in operation. Data from evaluations carried out by instrument manufacturer’s and suppliers is reported and discussed. This data offers specifications to a common format for initial selection of instruments prior to purchase.     

拓扑指数法研究稀土显色剂结构与铈显色反应对比度的关系

计算了４３种不对称变色酸双偶氮膦酸型显色剂的Ａｍ拓扑指数，并将其与结构选择性因子相结合，用于偶氮类显色剂结构与铈显色反应对比度的相关性研究，讨论了显色剂结构对拓扑指数有译比度的影响。     

1-(偶氮苯基)-3-(3,5-二溴-2-吡啶)-三氮烯的合成及其与镉的显色反应

报道了 1 (偶氮苯基 ) 3 ( 3,5 二溴 2 吡啶 ) 三氮烯的合成及其与镉的显色反应。在TritonX 1 0 0存在下 ,于pH 1 0 .9的Na2 B4O7 NaOH缓冲介质中 ,镉与ABDBPDT形成摩尔比 1∶3型红色配合物。试剂及配合物的最大吸收波长分别为 430nm和 5 30nm。表观摩尔吸光系数为 1 .75× 1 0 5L·mol- 1 ·cm- 1 。镉含量在 0 μg/2 5mL～ 1 2 μg/2 5mL范围内符合比耳定律     

氨水溶液制备ZnO纳米晶阵列的研究

以氨水和硝酸锌为前躯体，采用低温水溶液法在涂敷ZnO晶种层的玻璃衬底上外延生长了ZnO纳米棒晶阵列。应用SEM、TEM、SAED和XRD表征了ZnO纳米晶的形貌和结构。讨论了该组成体系水溶液法纳米棒外延生长的机理及其对棒晶形貌的影响。通过对水溶液pH值的原位二次调整，制备出了ZnO纳米管和表面绒毛状的棒晶阵列，基于生长机理探讨了它们的形成原因，为实现不同形貌ZnO纳米晶阵列的优化控制提供了可能的技术途径。结果表明，不同形貌的ZnO均属沿c轴择优取向的六方纤锌矿结构。     

Trace Detection of Mercury(II) Using Gold Ultra‐Microelectrode Arrays

The electroanalytical detection of trace mercury(II) at gold ultra‐microelectrode arrays is reported. The arrays consist of 256 gold microelectrodes of 5 μm in diameter in cubic arrangements which are separated from their nearest neighbor by 100 μm. The array was utilized in nitric acid using linear sweep voltammetry where a linear response from mercury additions over the range 10 μg L^?1?200 μg L^?1 (10^?8?10^?6 M) was observed with a sensitivity and detection limit of 0.11 nC/μg L^?1 and 3.2 μg L^?1 (16 nM) respectively from using a deposition time of 30 s at ?0.2 V (vs. SCE). This methodology was explored in 0.1 and 1 M chloride media over the mercury range 10 μg L^?1?200 μg L^?1 (5×10^?8?10^?6 M) where similar sensitivities of 0.087 nC/μg L^?1 and 0.078 nC/μg L^?1 were observed with an identical detection limit. The protocol is demonstrated to be useful for the determination of mercury for analysis of environmental water samples.     

Simplified Solid-Phase Extraction Procedure and Liquid Chromatographic Determination of Celecoxib in Rat Serum

A simplified solid phase extraction method, eliminating a preliminary protein precipitation has been developed for the determination of celecoxib in rat plasma. The technique included a solid phase extraction of the serum samples on a [poly (divinylbenzene-co-N-vinylpyrrolidone)] sorbent. After conditioning, the cartridge was loaded with 0.5 mL of acidified serum containing internal standard. Elution was made with 1 mL of a mixture of acetonitrile and methanol (1/1, v/v). After evaporation of the eluate to dryness and reconstitution with methanol, the samples were analyzed on an octadecyl bonded phase with several mobile phases containing acetonitrile and a phosphate buffer. Detection was carried out using a Photodiode Array Detector. Full validation of the proposed method was provided (linearity range: 0.01–2 mg. L^–1, average extraction efficiency: 92.4%; average intra-day variability: 4.6% with an accuracy of 94.8%; average interday variability: 5% with an accuracy of 95.3%, limit of detection: 0.005 mg. L^–1, limit of quantification: 0.002 mg. L^–1). The proposed method was successfully utilised to quantify celecoxib in rat plasma for a pharmacokinetic study.Revised: 26 January and 23 April 2004     

Microdevices for manipulation and accumulation of micro- and nanoparticles by dielectrophoresis

Microfluidic devices with three-dimensional (3-D) arrays of microelectrodes embedded in microchannels have been developed to study dielectrophoretic forces acting on synthetic micro- and nanoparticles. In particular, so-called deflector structures were used to separate particles according to their size and to enable accumulation of a fraction of interest into a small sample volume for further analysis. Particle velocity within the microchannels was measured by video microscopy and the hydrodynamic friction forces exerted on deflected particles were determined according to Stokes law. These results lead to an absolute measure of the dielectrophoretic forces and allowed for a quantitative test of the underlying theory. In summary, the influence of channel height, particle size, buffer composition, electric field, strength and frequency on the dielectrophoretic force and the effectiveness of dielectrophoretic deflection structures were determined. For this purpose, microfluidic devices have been developed comprising pairs of electrodes extending into fluid channels on both top and bottom side of the microfluidic channels. Electrodes were aligned under angles varying from 0 to 75 degrees with respect to the direction of flow. Devices with channel height varying between 5 and 50 microm were manufactured. Fabrication involved a dedicated bonding technology using a mask aligner and UV-curing adhesive. Particles with radius ranging from 250 nm to 12 microm were injected into the channels using aqueous buffer solutions.     

Application of an artificial neural network (ANN) and piezoelectric chemical sensor array for identification of volatile organic compounds

A piezoelectric chemical sensor array was developed using four quartz crystals. Gas chromatographic stationary phases were used as sensing materials and the array was connected to an artificial neural network (ANN). The application of the ANN method proved to be particularly advantageous if the measured property (mass, concentration, etc.) should not be connected exactly to the signal of the transducers of the piezoelectric sensor. The optimum structure of neural network was determined by a trial and error method. Different structures were tried with several neurons in the hidden layer and the total error was calculated. The optimum values of primary weight factors, learning rate (η=0.15), momentum term (μ=0.9), and the sigmoid parameter (β=1) were determined. Finally, three hidden neurons and 900 training cycles were applied. After the teaching process the network was used for identification of taught analytes (acetone, benzene, chloroform, pentane). Mixtures of organic compounds were also analysed and the ANN method proved to be a reliable way of differentiating the sensing materials and identifying the volatile compounds.     

Pretreatment of swine wastewater using anaerobic filter

Efforts were made to assess the efficiency of an anaerobic filter packed with porous floating ceramic media and to identify the optimum operational condition of anaerobic filter as a pretreatment of swine wastewater for the subsequent biological removal of nitrogen and phosphorus. A stepwise decrease in hydraulic retention time (HRT) and an increase in organic loading rate (OLR) were utilized in an anaerobic filter reactor at mesophilic temperature (35°C). The optimum operating condition of the anaerobic filter was found to be at an HRT of 1 d. A soluble chemical oxygen demand (COD) removal efficiency of 62% and a total suspended solids removal efficiency of 39% at an HRT of 1 d were achieved with an OLR of 16.0 kg total COD/(m³·d), respectively. The maximum methane production rate approached 1.70 vol of biogas produced per volume of reactor per day at an HRT of 1 d. It was likely that the effluent COD/total Kjeldahl nitrogen ratio, of 22, the COD/total phosphorous ratio of 47, and the high effluent alkalinity >2500 mg/L as CaCO₃ of the anaerobic filter operated at an HRT of 1 d was adequate for the subsequent biological removal of nitrogen and phosphorus.