Determination of [13C-15N] Labeled Methylxanthines by Gas Chromatography-Atomic Emission Detection (GC-AED) and Compound-Independent Calibration

ABSTRACT

Compound independent calibration (CIC) can be used to measure stable isotopically labeled molecules and their metabolites. This study was designed to demonstrate that gas chromatography coupled to atomic emission detection and CIC are useful analytical tools for the specific and quantitative determination of ¹³C and ¹⁵N labeled caffeine and its metabolites. These labeled compounds can be measured by monitoring either ¹³C or ¹⁵N atomic emission lines and using only one calibration function from one of the analytes. This method can be helpful when it is difficult or impossible to obtain an authentic reference material, which is often the case in metabolic studies.     

Potentiometric Flow-Injection Determination of Sugars Using a Metallic Copper Electrode

Abstract

The determination of reducing sugars is shown to be possible by use of potentiometric detection with a metallic copper indicator electrode by either flow-injection analysis (FIA) or high-performance liquid chromatography. Various sugars including arabinose, maltose, sorbose, glucose, fructose, sucrose, lactose and xylose, give an electrode response when injected into different carrier streams composed of cupric ions in weakly complexing ligand solutions comprised of either ammonia or tartrate. Optimization of response depends on flow-rate, temperature, pH, and concentrations of carrier components. Chromatography using a cation-exchange column and post-column addition of carrier reagents similar to those used for FIA is demonstrated to give detectable separation of four sugar components with umole injection quantities.     

Selective detection and identification of Se containing compounds--review and recent developments

The complexity of selenium (Se) chemistry in the environment and in living organisms presents broad analytical challenges. The selective qualitative and quantitative determination of particular species of this element is vital in order to understand selenium's metabolism and significance in biology, toxicology, clinical chemistry and nutrition. This calls for state-of-the-art analytical techniques such as hyphenated methods that are reviewed with particular emphasis on interfaced separation with element-selective detection and identification of the detected selenium compounds. Atomic spectral element specific detection for monitoring chromatographic eluent enabled quantitative determination of selenium species in selenized yeast and qualitative measurement for breath samples. Gas chromatography with atomic emission detection (AED) of ethylated species and fluoroacid ion pair HPLC applied to the analysis of currently produced or archived selenized yeast and Brassica juncea have revealed the presence of a previously unrecognised Se-S amino acid, S-(methylseleno)cysteine.     

Thermal decomposition of silica based surface compounds as a source of volatile standards. A new approach to the generation of gaseous calibration mixtures

A new approach to the preparation of standard gaseous mixtures based on thermal decomposition of surface compounds, has been reviewed. The method is used to prepare standard mixtures containing volatile analytes such as thiols, isothiocyanates, carbon monoxide, carbon dioxide, ammonia, amines, ethylene and methyl chloride. The method enables the preparation of the standard immediately before a calibration step. It is specially useful for the generation of standard mixtures containing volatile, malodorous, unstable and toxic compounds. Presented at Balaton Symposium on High Performance Separation Methods, Siófok, Hungary, September 1–3, 1999     

多壁碳纳米管修饰电极检测盐酸氯丙嗪的研究

制备了多壁碳纳米管修饰玻碳电极,采用循环伏安法(CV)研究了盐酸氯丙嗪在修饰电极上的电化学特性,发展了一种新的检测盐酸氯丙嗪的电化学分析方法。在最佳实验条件下,用循环伏安法检测盐酸氯丙嗪,其响应电流与盐酸氯丙嗪的浓度在8.0×10-5~1.0×10-3mol/L范围内有很好的线性关系,线性方程为Ip(A)=0.0106c(mol/L)-8×10-8(R2=0.999,n=6),检出限为6.2×10-6mol/L(S/N=3)。方法可用于盐酸氯丙嗪片的测定。     

Analysis of microcystins by capillary zone electrophoresis coupling with electrospray ionization mass spectrometry

In this paper, a rapid and effective method based on capillary zone electrophoresis (CZE) coupled with electrospray ionization mass spectrometry (ESI-MS) was established for the trace analysis of microcystin (MC) isomers in crude algae sample. The experimental conditions including the composition, acidity and concentration of buffer, separation voltage, injection time, and MS detection parameters were investigated in detail. A capillary separation system was as follows: a uncoated fused-silica capillary tube (50 μm i.d. × 90 cm), 40 mmol L⁻¹ ammonium acetate solution (pH 9.86) as running buffer, 25 kV as separation voltage, 20 kV × 3 s water first and 20 kV × 20 s for sample injection. Mass analysis was performed in ESI source, with sheath gas temperature 150 °C, sheath gas pressure 10 psi, and sheath gas flow 6 L min⁻¹. And sheath liquid was 7.5 mmol L⁻¹ acetic acid in 50% isopropanol-water (3 μL min⁻¹). Protonation and ammonium adduct molecular ions m/z 506.9 (MC-LR) and 532.0 (MC-YR) were used for the quantification of MCs. Under these conditions, two MCs were baseline separated within 9 min, the calibration curves were obtained in the range of 0.11-10.0 μg mL⁻¹ and 0.16-10.5 μg mL⁻¹ for MC-LR and MC-YR, respectively. Meanwhile, limits of detection were 0.05 and 0.08 μg mL⁻¹ for MC-LR and MC-YR, respectively. The recoveries for the two MCs were in the range of 95.8-108%. The developed approach had been successfully applied to the analysis of MCs in crude algae samples.     

Quantitative analysis of 3‐OHB[a]P and (+)‐anti‐BPDE as biomarkers of B[a]P exposure in rats

The aim of this study was to develop an analytical method for the determination the levels of metabolites of benzo[a]pyrene (B[a]P), 3‐hydroxybenzo(a)pyrene (3‐OHB[a]P) and (+)‐anti‐benzo(a)pyrene diol‐epoxide [(+)‐anti‐BPDE, combined with DNA to form adducts], in rat blood and tissues exposed to B[a]P exposure by high‐performance liquid chromatography with fluorescence detection (HPLC/FD), and to investigate the usefulness of 3‐OHB[a]P and (+)‐anti‐BPDE as markers of intragastrical exposure to B[a]P in rats. The levels of 3‐OH‐B[a]P and B[a]P‐tetrol I‐1 released after acid hydrolysis of (+)‐anti‐BPDE in the samples were measured by HPLC/FD. The calibration curves were linear (r² > 0.9904), and the lower limit of quantification ranged from 0.34 to 0.45 ng/mL for 3‐OHB[a]P and from 0.43 to 0.58 ng/mL for (+)‐anti‐BPDE. The intra‐ and inter‐day stability assay data suggested that the method is accurate and precise. The recoveries of 3‐OHB[a]P and (+)‐anti‐BPDE were in the ranges of 73.6 ± 5.0 to 116.5 ± 6.3% and 73.3 ± 8.5 to 141.2 ± 13.8%, respectively. A positive correlation was found between the concentration of intragastrical B[a]P and the concentrations of 3‐OH‐B[a]P and (+)‐anti‐BPDE in the blood and in most of the tissues studied, except for the brain and kidney, which showed no correlation between B[a]P and 3‐OHB[a]P and between B[a]P and (+)‐anti‐BPDE, respectively. A sensitive, reliable and rapid HPLC/FD was developed and validated for analysis of 3‐OHB[a]P and (+)‐anti‐BPDE in rat blood and tissues. There was a positive correlation between the concentration of 3‐OHB[a]P or (+)‐anti‐BPDE in the blood and the concentration of 3‐OHB[a]P or (+)‐anti‐BPDE in the most other tissues examined. The concentration of 3‐OHB[a]P or (+)‐anti‐BPDE in the blood could be used as an indicator of the concentration of 3‐OHB[a]P or (+)‐anti‐BPDE in the other tissues in response to B[a]P exposure. These results demonstrate that 3‐OHB[a]P and (+)‐anti‐BPDE are potential biomarkers of B[a]P exposure, which would also be useful to assess the carcinogenic risks from B[a]P exposure. Copyright © 2015 John Wiley & Sons, Ltd.     

科学仪器工作状态监测装置的设计与实现

建立了支持网络通讯的科学仪器工作状态监测装置。该检测装置以单片机系统为核心,运用信号检测技术获取仪器的工作状态信息,实现有效机时的记录。基于自制编码表对数据进行BASE64编码,保证了记录信息的安全;支持嵌入式互联网技术将被监测仪器的实时状态上传到远程服务器,实现大型科学仪器的网络化监测。     

Application of an in-line imprinted polymer column in a potentiometric flow-injection chemical sensor to the determination of the carbamate pesticide carbaryl in complex biological matrices

A flow-injection biosensor-like system based on a nonenzymatic approach has been developed to determine the carbamate pesticide carbaryl in complex biological samples without lengthy and expensive extraction steps. Molecularly imprinted polymeric beads were used to immobilize carbaryl from biological samples. pH variation permitted the elution of carbaryl from the binding cavity to the flow cell. A pH electrode was used to detect changes in the charge of carbaryl in the sample solution resulting from the protonation and deprotonation of the molecule over different pH ranges. At pH 2.0, the secondary amine group is protonated, giving a (+1) charge to the carbaryl molecule. At pH 8.0, the ionized carbaryl loses a proton to become neutral, changing the local pH of the flow cell. The pH change at the flow cell generated by the deprotonation of carbaryl ion in alkaline medium was used to determine the carbaryl concentration. Parameters influencing the performance of the system were optimized for use in the detection procedure. The validated biosensor-like system had a carbaryl detection limit of 10.0 μg/mL and a response that was linear (r ² > 0.98) over the concentration range of 10.0–00 μg/mL.     

Inductively coupled plasma atomic emission spectrometry — Optimization of the operating conditions in the determination of trace of elements in line-rich emission matrices

Radial viewing 40.68 MHz inductively coupled plasma atomic emission spectrometer was used in the determination of Y, Sc and rare earth elements in Eu₂O₃ or Lu₂O₃ as pure rare earth matrices. The Mg II 280.270 nm/Mg I 285.213 nm line intensity ratio was measured to evaluate the robustness of the operating conditions. The operating conditions were affected by varying the incident power and sheathing gas flow rate. The carrier gas flow rate remained a constant value. The relationship between the Mg II 280.270 nm/Mg I 285.213 nm ratio and the excitation temperature was obtained. A dependence of the magnesium ratio in the pure solvent and the corresponding values in the presence of the above matrices was established.