Gas chromatographic system equipped with a mass detector and a selective nitrogen-phosphorous detector operating simulataneously in the analysis of pesticide residues

The possibility to perform gas chromatographic analysis using both a mass detector and a selective nitrogen-phosphorous detector will enable highly sensitive analytical results and an optimal identification reliability. In this work we describe an easily workable technical solution, which has been accomplished in our laboratory and the application of the above system to analytical procedures for the detection and determination of nitrogenous herbicides in drinking water and phosphorylated pesticides in agricultural products is discussed.     

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.     

检出限概念问题讨论—IUPAC及其它检出限定义的综合探讨和实验论证

讨论文以大量实验数据为依据，查证了光分析法中影响检出限的诸多因素，用设计实验获得数据与理论结合，对几种推荐的检出限计算方法予以归纳、论证，阐明以检出限做为分析主、分析仪器的比较标准时，应正确理解的有关问题和使用检出限的注意事项。     

A review of opportunities for electrospun nanofibers in analytical chemistry

Challenges associated with analyte and matrix complexities and the ever increasing pressure from all sectors of industry for alternative analytical devices, have necessitated the development and application of new materials in analytical chemistry. To date, nanomaterials have emerged as having excellent properties for analytical chemistry applications mainly due to their large surface area to volume ratio and the availability of a wide variety of chemical and morphological modification methods. Of the available nanofibrous material fabrication methods, electrospinning has emerged as the most versatile. It is the aim of this contribution to highlight some of the recent developments that harness the great potential shown by electrospun nanofibers for application in analytical chemistry. The review discusses the use of electrospun nanofibers as a platform for low resolution separation or as a chromatographic sorbent bed for high resolution separation. It concludes by discussing the applications of electrospun nanofibers in detection systems with a specific focus on the development of simple electrospun nanofiber based colorimetric probes.     

The Reliability of Detection Limits in Analytical Chemistry

Abstract

Five guidelines were elucidated to be of importance in improving the reliability of detection limits in analytical chemistry. The necessity of following rigid statistical rules and documentation of the experimental system, the experimental parameters and the entire analytical procedure, is stressed, in order for the detection limits to have any reliability.     

Accredited laboratory for detection of irradiated foods in Poland

The history of the development and the role of the Accredited Laboratory for Detection of Irradiated Foods in the national quality food control system are described. The analytical methods for the detection of irradiation in foods adapted and accredited in the Laboratory are enumerated and discussed.     

Analysis of Caffeine Deutero Isotopomers by Gas Chromatography and Atomic Emission Detection

Abstract

This paper describes the behaviour of various caffeine deutero isotopo-mers analyzed using gas chromatography coupled wiih atomic emission detection. Results are given concerning the linearity of the response and the detection limits for carbon, nitrogen, hydrogen and deuterium. It is demonstrated that neither the number of deuterium atoms per isotopomer nor the location of deuterium labeling modify the analytical response.     

Calculation of detection limits for a single-laboratory ion-chromatographic method to determine parts-per-trillion ions in ultrapure water

This paper addresses the calculation of detection limits (DLs) for ion-chromatographic data at low part-per-trillion (w/w) levels. The main objectives are: (1) to explain two statistical techniques (the EPA or “3σ” approach and the Hubaux-Vos method), (2) to calculate DLs using each procedure, (3) to discuss the strengths and weaknesses of each statistical approach and (4) to decide if the analytical method is appropriate for quantifying anions at the 50-ppt level in deionized water. The analytes of interest are: fluoride, chloride, nitrite, bromide, nitrate, sulfate and phosphate. All work was performed on a Dionex DX500 microbore unit, using an AS11 column. Results indicate that the H-V method gives a more realistic (and higher) DL than does the 3σ. Assuming false-negative and false-positives probabilities of 10% or less, this analytical method is not acceptable for quantifying anions at the desired level.     

A quantitative assessment of chemical techniques for detecting traces of explosives at counter-terrorist portals

Previous reviews have discussed in a qualitative manner the various highly sensitive analytical techniques for detecting minute traces of explosive material. However, there is no review available which compares quantitatively the sensitivities of the different analytical methods for detecting explosives. In view of the importance of this area to the present day planning of counter-terrorist strategies, this review makes a comprehensive and quantitative comparison of the analytical chemical methods which can be used for the detection of trace explosives in the luggage and on the persons of travelers. Possible directions of future development in this area are also discussed.     

Liquid chromatography with atmospheric pressure chemical ionization and electrospray ionization mass spectrometry of flavonoids with triple-quadrupole and ion-trap instruments

With 15 flavonoids as test compounds, the analytical performance of four modes of LC-MS, multiple MS (MSn) and tandem MS operation (atmospheric pressure chemical ionization (APCI), electrospray ionization, positive and negative ionization) was compared for two mass spectrometers, a triple-quadrupole and an ion-trap instrument. Two organic modifiers, methanol and acetonitrile, and two buffers, ammonium acetate and ammonium formate, were used. In general, the use of APCI in the negative ion mode gave the best response, with the signal intensities and the mass-spectral characteristics not differing significantly between the two instruments. The best results were obtained when methanol-ammonium formate (pH 4.0) was used as LC eluent. Under optimum conditions full-scan limits of detection of 0.1-30 mg/l were achieved in the negative APCI mode. Here it needs to be emphasized that up to 2-order response differences were found both between analytes and between modes of ionization. This implies that one should be very cautious when interpreting data on the screening of real-life samples. The main fragmentations observed in the MSn spectra on the ion-trap, or the tandem MS spectra on the triple-quadrupole were generally the same. The advantage of the former approach is the added possibility to ascertain precursor-->product ion relationships.     

水中药物和个人护理品分析方法研究进展

随着社会经济发展水平的提高和医疗条件的改善,药物和个人护理品(PPCPs)的使用种类及总量均显著增加,造成环境中PPCPs的残留浓度不断升高,进而会对水环境生态安全及人类和动植物的健康造成潜在危害和严重威胁.由于开发建立快速、灵敏、高效的PPCPs定性、定量分析方法是探究其存在、去除及毒性的前提,因此本文对水中PPCP...     

Analytical detection methodologies for methane and related hydrocarbons

The determination of methane is of strong interest to the analytical community due to its natural abundance, its potential to cause explosions and its known greenhouse effect. The current report gives a brief overview into the environmental significance of methane and an account of the existing detection protocols for methane in air and environmental samples.     

Liposomes in analyses

The use of liposomes as analytical and bioanalytical reagents has been shown to be successful of in a variety of different applications that will be reviewed here. Due to their high surface area, large internal volume, and ability to conjugate bilayer lipids with a variety of biorecognition elements liposomes have been used in homogenous and heterogeneous assays, providing signal amplification both as intact or lysed vesicles. This review covers the discussion of their application in recent liposome-based immunoassay publications and includes the growing number of other non-immunoassay applications as an evidence of their immense versatility. In this article, a general background about liposomes is given first that extends past the use of liposomes as analytical tools. The main discussion is then divided by the manner in which liposomes are utilized as signaling reagents for the assays. Where available, the detection limits for common analytes that have been assayed using multiple liposome-based detection systems are presented. The advantages of using liposomes in terms of sensitivity versus other techniques are also discussed.     

Tutorial on estimating the limit of detection using LC-MS analysis,part II: Practical aspects

In part II of this tutorial, the investigated approaches of estimating the limit of detection (LOD) are applied to experimental data from LC-MS measurements. Important practical aspects specific to LC-MS and related to LOD are reviewed. The results of different tests of estimating linearity and scedasticity are compared. LOD estimates obtained with different approaches (for both simple characterization of the analysis method and accurate interpretation of the results) are applied to the data and the obtained values are compared. As a conclusion, a decision tree is proposed for estimating LOD for analytical methods using the LC-MS technique.     

激光光热反射光谱检测装置的研制

研制出一种采用直接测量激光反射光信号的激光光热反射光谱检测装置。讨论了该装置的硬件结构和程序模块,并应用于分子印迹实验。该装置具有操作简单、精度高、稳定性好和抗干扰能力强等优点。     

Detection method for microchip separations

The features of analytical systems utilizing microfluidic devices, especially detection methods, are described. Electrochemical detection (EC), laser-induced fluorescence (LIF), mass spectrometry (MS), and chemical luminescence (CL) methods are covered. EC enables detection without labeling and has been used in recent years because of its low cost and sensitivity. LIF is the most generally used detection method in microchip separations. Use of LED as an excitation source for fluorescence measurement was also developed for the purpose of miniaturization of the entire system, including detection and separation. Although MS enables highly sensitive analysis, the interface between MS and micro channels is still under examination. This review with fifty-two references introduces interesting detection methods for microchip separations. Related separation methods using microfluidic devices are also discussed.     

Tutorial on estimating the limit of detection using LC-MS analysis,part I: Theoretical review

A large body of literature exists on the limit of detection (LOD), but there is still a lot of confusion about this important validation parameter. This confusion mainly stems from its statistically complex background. The goal of this two-part tutorial is to discuss and clarify the topic of LOD for practitioners. The two main conclusions of this tutorial are: (1) the choice of how to estimate LOD should be based on the purpose of the analytical method that is being validated (e.g. considerable effort should not be made to estimate LOD for a method that is not used for detecting traces in the vicinity of LOD), and (2) LOD estimates are strongly dependent on different assumptions and the approach used, and therefore caution must be exercised when using the estimate or when comparing different estimates.     

A method based on stochastic resonance for the detection of weak analytical signal

An effective method for detection of weak analytical signals with strong noise background is proposed based on the theory of stochastic resonance (SR). Compared with the conventional SR-based algorithms, the proposed algorithm is simplified by changing only one parameter to realize the weak signal detection. Simulation studies revealed that the method performs well in detection of analytical signals in very high level of noise background and is suitable for detecting signals with the different noise level by changing the parameter. Applications of the method to experimental weak signals of X-ray diffraction and Raman spectrum are also investigated. It is found that reliable results can be obtained.     

An unusual systematic behaviour of detection limits for elements from 55Cs to 73Ta

A representative database for detection limits for all elements from ⁵⁵Cs to ⁷³Ta reveals that these limits are governed by a systematic zigzag pattern, according to which the odd atomic number elements have systematically lower detection limits than the even atomic number neighbour elements. This is true even when the actual detection limits vary by several orders of magnitude. We propose that such a systematic pattern be used as a requisite analytical criterion to evaluate the detection limit data, and any departure from this pattern be looked on with caution to check the analytical technique for any interference or matrix effect problems.Electronic Supplementary Material Supplementary material is available for this article if you access the article at . A link in the frame on the left on that page takes you directly to the supplementary material.     

Determination of quinolones by fluorescent excitation emission

In this work the viability of a fluorescent technique for the determination of quinolones is studied. This analytical technique allows one to analyze the effect of the increasing order of the analytical signal from a univariate calibration (zero order data) to partial least squares (PLS) calibration (first order). The comparison has been done through the figures of merit of the analytical procedure (technique and calibration) in accordance with the ISO norm and the 2002/657/EC European Decision about residuals.