Determination of sulfa antibiotic residues in river and particulate matter by field-amplified sample injection-capillary zone electrophoresis

In the present research, field-amplified sample injection–CZE (FASI–CZE) coupled with a diode array detector was established to determine trace level sulfa antibiotic. Sulfathiazole, sulfadiazine, sulfamethazine, sulfadimethoxine, sulfamethoxazole, and sulfisoxazole were selected as analytes for the experiments. The background electrolyte solution consisted of 70.0 mmol/L borax and 60.0 mmol/L boric acid (including 10% methanol, pH 9.1). The plug was 2.5 mmol/L borax, which was injected into the capillary at a pressure of 0.5 psi for 5 s. Then the sample was injected into the capillary at an injection voltage of –10 kV for 20 s. The electrophoretic separation was carried out under a voltage of +19 kV. The capillary temperature was maintained at 20˚C throughout the analysis, and six sulfonamides were completely separated within 35 min. Compared with pressure injection-CZE, the sensitivity of FASI-CZE was increased by 6.25–10.0 times, and the LODs were reduced from 0.2–0.5 to 0.02–0.05 μg/mL. The method was applied to the determination of sulfonamides in river water and particulate matter samples. The recoveries were 78.59–106.59%. The intraday and interday precisions were 2.89–7.35% and 2.77–7.09%, respectively. This provides a simpler and faster method for the analysis of sulfa antibiotic residues in environmental samples.     

A rigid subspace of the real line whose square is a homogeneous subspace of the plane

Working in ZFC, we give an example as indicated in the title.

     

Resistivity－temperature characteristics of sol gel YBa2Cu3Oy samples synthesized in flowing oxygen atmosphere

The relationship of resistivity versus synthesizing temperature of sol gel YBa_2Cu_3O_y samples was studied when prepared under flowing oxygen conditions. A set of high-temperature ρ－T curves was obtained for the whole process. After the sample finished the test measuring, its resistivity was ρ_{300}=9.83×10^{-3 }Ω·cm at room temperature. The ρ－T curve also showed that the orthorhombic－tetragonal phase transformation of sol-gel YBa_2Cu_3O_y sample occurred at 581℃ for the sample in the rising temperature process, but at 613℃ in the cooling process, lower than that of the samples made by using the conventional powder metallurgy methods.     

Spectrofluorimetric Method for the Determination of Aluminum with Alizarin Red PS

 A simple and direct spectrofluorimetric method has been developed for the determination of aluminum using alizarin red PS (1,2,4-trihydroxy 9,10-anthraquinone-3-sulfonic acid). The method is based on the strong fluorescence (480/564 nm) of Al³⁺ and alizarin red. Experimental parameters such as pH, concentration of the ligand, ionic strength of the solution, reaction time and temperature were optimized in order to maximize the analytical signal. Interferences of several ions (anions and cations) were studied and evaluated. The linear range of the method extends from 3 to 100 μg L⁻¹. Limit of detection (3s_b) was 0.9 μg L⁻¹. The method was tested with a silicate certified reference material. Interferences were eliminated by a liquid extraction with cupferron. Author for correspondence. E-mail: aucelior@rdc.puc-rio.br Received September 10, 2002; accepted January 15, 2003 Published online May 5, 2003     

色质联用技术在毒物分析中的应用

从生物样品中检测未知物,一直以来是毒物分析中的一个难点。如何有效地提取目标化合物,并选择适合的检测手段将未知物筛选出来,GC-MS方法是快速筛选多种毒物和药物的一个简便、可靠的手段。随着MS技术的不断发展,更灵敏、更准确的特性将使其成为药物和毒物分析中必不可少的一门技术。     

关于实Hilbert环

通过引进“强实Hilbert环”这一概念,本文证明了,一个环A是强实Hilbert环,当且仅当多项式环A[X]是实Hilbert环,当且仅当A[X]的每个实极大理想在A上的局限是实极大的,从而文献[1]中两个主要结果被否定.此外,本文还研究了所谓的“严格的实Hilbert环”,这类环对于半代数零点定理等方面的探讨更具应用意义.     

激光除锈过程的实时监测技术研究

对激光除锈过程中的实时监测技术进行了实验研究,结果表明:除锈过程中产生的声波强度会随着表面清洁度的变化而发生明显的变化,声波信号包含了除锈过程中的大量信息,可作为激光除锈实时监测的基本信号.     

事后分层方法及其在交通运输抽样调查中的应用

本文介绍事后分层技术，说明了它不仅可用于简单随机抽样，而且可以用于放回ＰＰＳ抽样。给出了事后分层估计量的形式，证明了它的无编性，并给出了它在交通运输抽样调查中的应用。     

软X光辐射烧蚀实验方法研究

 用强激光辐照金箔靶，以金箔背侧软X光辐射为基础，提出了软X光辐射烧蚀研究的新靶型、新方法，做了C₈H₈样品辐射烧蚀初步实验。     

Mathematical topographical correction of XPS images using multivariate statistical methods

For rough heterogeneous samples, the contrast observed in XPS images may result from both changes in elemental or chemical composition and sample topography. Background image acquisition and subtraction are frequently utilized to minimize topographical effects so that images represent concentration variations in the sample. This procedure may significantly increase the data acquisition time. Multivariate statistical methods can assist in resolving topographical and chemical information from multispectral XPS images. Principal component analysis (PCA) is one method for identification of the highest correlation/variation between the images. Topography, which is common to all of the images, will be resolved in the first most significant component. The score of this component contains spatial information about the topography of the surface, whereas the loading is a quantitative representation of the topography contribution to each elemental/chemical image. The simple‐to‐use self‐modelling mixture analysis (Simplisma) method is a pure variable method that searches for the source of most differences in the data and therefore has the potential to distinguish between chemical and topographical phases in images. The mathematical background correction scheme is developed and validated by comparing results to the experimental background correction for samples with differing degrees of topography. Copyright © 2004 John Wiley & Sons, Ltd.