Practical applications of open tubes in liquid chromatography

The practical applications of open tubes in liquid chromatography as separation columns and as reactors for post column derivatization are discussed. With present technology, the potential efficiency of open tubular columns cannot be fully exploited. As reactors in post column derivatization, these tubes offer many advantages if knitted or stitched to enhance radial mass transfer. The application of open tubes with diameters between 0.12 mm and 0.6 mm as reactors in the selective and sensitive detection of amino acids is demonstrated.     

高效液相色谱法测定氨基酸的研究进展

氨基酸是构成生物体的基础物质,氨基酸分析是生命科学研究中最重要的领域之一。高效液相色谱法因分析速度快、操作简便、检测灵敏、适用范围广等优点而广泛应用于食品工业、制药工业、生命科学研究等领域。该文综述了高效液相色谱分析氨基酸的方法,包括柱后衍生法、柱前衍生法、高效阴离子交换色谱-积分脉冲安培检测法和高效液相色谱-蒸发光散射检测法。并对上述方法进行了比较,为日常的氨基酸分析提供了参考。     

Stripping voltammetry at micro-interface arrays: A review

In this article, a comprehensive overview of the most recent developments in the field of stripping voltammetry at regular micro-interfaces (both solid–liquid and liquid–liquid interfaces) is presented. This review will report on the most conventional arrays of metallic micro-electrodes but also on the rapidly growing field of electrochemistry at arrays of micro-interfaces between two immiscible electrolyte solutions (μITIES). The main fabrication methods, together with some design considerations and diffusion phenomena at such interfaces are discussed. Main applications of micro-interface arrays are presented including heavy metals detection at micro-electrode arrays and detection of organic molecules (amino acids, vitamins, peptides and drugs) at the μITIES. Stripping analysis at micro-interface arrays is suitable for the detection of analytes in several real media including water, soil extracts and biological fluids (blood and saliva) with high specificity, sensitivity (detection limits of nM, ppb level) and reliability. Stripping analysis at μITIES and micro-electrode arrays are two complementary approaches that have the advantages of being cost effective, simple to use and easily adaptable to field measurement.     

Fluorescence enhancement for aflatoxins in HPLC by post-column split-flow iodine addition from a solid-phase iodine reservoir

Summary A method for post-column derivatization of the highly carcinogenic aflatoxins with iodine has been developed. It involves splitting of the mobile phase used for the reversed phase HPLC separation. One part flows through the injection valve and the C₁₈ analytical column to achieve the separation. The other part flows through a column packed with solid iodine. The iodine-containing solution is recombined with the flow coming from the analytical column. The derivatization reaction takes place in a knitted open tubular reactor maintained at 60 °C. Detection is done by fluorescence measurement. Due to the low solubility of iodine in the mobile phase, the iodine solid-phase column can be used for very long periods of time before refilling is necessary. The analytical system consists of only one pump and therefore gives the opportunity to carry out low-cost post-column reaction detection. The method yields reproducible results, a linear response over at least two orders of magnitude and detection limits of about 1 ppb, both for standard solutions and for peanut butter samples.     

Conducting polymers in chemical sensors and arrays

The review covers main applications of conducting polymers in chemical sensors and biosensors. The first part is focused on intrinsic and induced receptor properties of conducting polymers, such as pH sensitivity, sensitivity to inorganic ions and organic molecules as well as sensitivity to gases. Induced receptor properties can be also formed by molecularly imprinted polymerization or by immobilization of biological receptors. Immobilization strategies are reviewed in the second part. The third part is focused on applications of conducting polymers as transducers and includes usual optical (fluorescence, SPR, etc.) and electrical (conductometric, amperometric, potentiometric, etc.) transducing techniques as well as organic chemosensitive semiconductor devices. An assembly of stable sensing structures requires strong binding of conducting polymers to solid supports. These aspects are discussed in the next part. Finally, an application of combinatorial synthesis and high-throughput analysis to the development and optimization of sensing materials is described.     

原位衍生化技术在液相色谱和液相色谱-质谱联用分析中的应用

衍生化是将待分析物转化为更适合的物质形式以便于分析的有效手段。原位衍生化技术作为一种常用的柱前衍生化方法,可以在样品基质中同时完成分析物的萃取和衍生化,具有高效、灵敏和选择性好的优点。原位衍生化结合其他前处理技术广泛用于胺类、醛酮类、醇类、酚类、羧酸和巯基化合物的分析中,在生物、药物、食品、环境、化妆品分析等领域有广泛的应用。该文概述了原位衍生化的反应类型和代表性衍生试剂,综述了原位衍生化技术在液相色谱和液相色谱-质谱联用分析中的应用,并展望其发展趋势。     

Derivatization procedures and their analytical performances for HPLC determination in bioanalysis

Derivatization, or chemical structure modification, is often used in bioanalysis performed by liquid chromatography technique in order to enhance detectability or to improve the chromatographic performance for the target analytes. The derivatization process is discussed according to the analytical procedure used to achieve the reaction between the reagent and the target compounds (containing hydroxyl, thiol, amino, carbonyl and carboxyl as the main functional groups involved in derivatization). Important procedures for derivatization used in bioanalysis are in situ or based on extraction processes (liquid–liquid, solid‐phase and related techniques) applied to the biomatrix. In the review, chiral, isotope‐labeling, hydrophobicity‐tailored and post‐column derivatizations are also included, based on representative publications in the literature during the last two decades. Examples of derivatization reagents and brief reaction conditions are included, together with some bioanalytical applications and performances (chromatographic conditions, detection limit, stability and sample biomatrix).     

Supercritical fluid chromatography as a tool for enantioselective separation; A review

Supercritical fluid chromatography (SFC) has become popular in the field of enantioselective separations. Many works have been reported during the last years. This review covers the period from 2000 till August 2013. The article is divided into three main chapters. The first one comprises a basic introduction to SFC. The authors provide a brief explanation of general principles and possibilities of this method. The advantages and drawbacks are also listed. Next part deals with chiral separation systems available in SFC, namely with the commonly used chiral stationary phases. Properties and interaction possibilities of the chiral separation systems are described. Recent theoretical papers are emphasized in this chapter. The last part of the paper gives an overview of applications of enantioselective SFC in analytical chemistry, in both analytical and preparative scales. Separation systems and conditions are summed up in tables so that they provide a helpful tool for analysts who search for a particular method of analysis.     

Doubly hydrogen-bridged 1,2-diphenylenediboranes derived from 9-chloro-9-borafluorene and ligand exchange reactions

Cyclic 1,2-diphenylenediboranes containing a doubly hydrogen-bridged structure, including 1,2-(2,2^′biphenylylene)diborane(I) and 1,2-(2,2^′biphenylylene)-1,2-diethyldiborane (II), are conveniently prepared by treating 9-chloro-9-borafluorene with NaBH₄ and Na(Et)₃BH, respectively. The reaction mechanism involves an initial Cl-H exchange to form 9-borafluorene containing a reactive 5-member ring diarylborane moiety, which subsequently engages in a facile ring expansion with the in situ formed B-H containing residue (BH₃ or HBEt₂) to result in cyclic 1,2-diphenylenediboranes compounds. The doubly hydrogen-bridged structure shows good thermal stability up to 50 °C. Upon thermal cleavage at higher temperature, all free B-H groups become very reactive involving hydroboration with α-olefin. The complexization study also reveals that this intradiborane moiety forms a 1:2 complex with a strong base, such as pyridine.     

Design of single chain magnets through cyanide-bearing six-coordinate complexes

The design and preparation of stable cyanide-bearing six-coordinate complexes of formula [M^III(L)(CN)_x]^{(x + l − m)−} (M = trivalent transition metal ion and L = polydentate blocking ligand) are summarized here. Their use as ligands towards either fully hydrated metal ions or coordinatively unsaturated preformed species, to afford a wide variety of low-dimensional metal assemblies whose nuclearity, dimensionality and magnetic properties can be tuned, is also reviewed. Special emphasis is put on the appropriate choice of the end-cap ligand L whose denticity determines the number of coordinated cyanide groups in the mononuclear precursors. Among the different new spin topologies obtained through this rational synthetic strategy, ferromagnetically coupled 4,2-ribbon like bimetallic chains which exhibit slow magnetic relaxation and hysteresis effects (chain as magnets) are one of the most appealing and constitute the heart of the present contribution.     

快速柱前衍生HPLC法检测曲格列汀中(R)-3-氨基哌啶

以邻苯二甲醛(OPA)和3-巯基丙酸为衍生试剂,建立了柱前衍生高效液相色谱(HPLC)测定曲格列汀中(R)-3-氨基哌啶含量的分析方法.(R)-3-氨基哌啶与衍生剂在碱性(pH 10.5)条件下于室温反应30s,进行柱前衍生,并利用高效液相色谱-质谱对衍生产物进行定性分析.采用YMC-Triart C18色谱柱(150...     

Liquid chromatography/tandem mass spectrometric method for the simultaneous determination of tobacco-specific nitrosamine NNK and its five metabolites

A sensitive and robust high-performance liquid chromatography-electrospray ionization tandem mass spectrometry method to analyze 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and its five metabolites in one passage was developed and validated. The method achieved excellent reproducibility and accuracy. Linearity was observed for all six compounds (R² = 0.999) with detection limits (S/N ≥ 3) ranging from 0.2 to 2.4 pg on column and 0.01-0.12 ng ml⁻¹ in samples injected. Average intra-day and inter-day variations (% R.S.D.) were 1.2 and 3.5%, respectively. A sample preparation method involving C8 and C18 solid phase extraction provided satisfactory recovery of the analytes in mouse urine. Each NNK metabolite was identified by its chromatographic retention time and specific fragmentation pattern. Since the carcinogenicity of NNK is related to its metabolism, the method described in this report should facilitate toxicological investigations into the carcinogenesis due to NNK exposure in the environment.     

大气颗粒物滤膜中极性有机物在线衍生装置的设计与应用

设计制作了一套用于气相色谱-质谱(GC-MS)分析极性有机物的在线衍生装置,并将其应用于大气颗粒物样品中极性有机物的检测.将大气颗粒物滤膜样品置于GC-MS进样口,通过使用套针组件,匀速引入气态衍生试剂N-甲基-Ⅳ-(三甲基硅烷)三氟乙酰胺(MSTFA),使其在衬管内于310℃下与待测物接触,10 min即可完成硅烷化...     

Applications of polymethacrylate-based monoliths in high-performance liquid chromatography

Monolithic columns were introduced in the early 1990s and have become increasingly popular as efficient stationary phases for most of the important chromatographic separation modes. Monoliths are functionally distinct from porous particle-based media in their reliance on convective mass transport. This makes resolution and capacity independent of flow rate. Monoliths also lack a void volume. This eliminates eddy dispersion and permits high-resolution separations with extremely short flow paths. The analytical value of these features is the subject of recent reviews. Nowadays, among other types of rigid macroporous monoliths, the polymethacrylate-based materials are the largest and most examined class of these sorbents. In this review, the applications of polymethacrylate-based monolithic columns are summarized for the separation, purification and analysis of low and high molecular mass compounds in the different HPLC formats, including micro- and large-scale HPLC modes.     

Chemical modification of polymeric microchip devices

Analytical polymeric microchips in both fluidic and array formats offer short analysis times, coupling of many sample processing and chemical reaction steps on one platform with minimal sample and reagent consumption, as well as low cost, minimal fabrication times and disposability. However, the invariable bulk properties of most commercial polymers have driven researchers to develop new modification strategies. This article critically reviews the scope and development of chemical modifications of such polymeric chips since 2003. Surface modifications were based on chemical derivatization or activation of surface layers with reagent solutions, reactive gases and irradiation. Bulk modification of polymer chips used newly incorporation of monomers with selective chemical functionalities throughout the bulk polymer material and integrated the chip modification and fabrication into a single step. Such modifications hold a great promise for establishing a true ‘lab-on-chip’ as can be seen from many novel applications for modulating electroosmosis, suppressing protein adsorption in microchip capillary electrophoretic separations, extraction of analytes and for zone-specific binding of enzymes and other biomolecules.     

Open tubular liquid chromatography: Recent advances and future trends

Nano-liquid chromatography (nanoLC) is gaining significant attention as a primary analytical technique across various scientific domains. Unlike conventional high-performance LC, nanoLC utilizes columns with inner diameters (i.ds.) usually ranging from 10 to 150 μm and operates at mobile phase flow rates between 10 and 1000 nl/min, offering improved chromatographic performance and detectability. Currently, most exploration of nanoLC has focused on particle-packed columns. Although open tubular LC (OTLC) can provide superior performance, optimized OTLC columns require very narrow i.ds. (< 10 μm) and demand challenging instrumentation. At the moment, these challenges have limited the success of OTLC. Nevertheless, remarkable progress has been made in developing and utilizing OTLC systems featuring narrow columns (< 2 μm). Additionally, significant efforts have been made to explore larger columns (10–75 μm i.d), demonstrating practical applicability in many situations. Due to their perceived advantages, interest in OTLC has resurged in the last two decades. This review provides an updated outlook on the latest developments in OTLC, focusing on instrumental challenges, achievements, and advancements in column technology. Moreover, it outlines selected applications that illustrate the potential of OTLC for performing targeted and untargeted studies.     

离子色谱法测定蚀刻槽废氢氟酸中的六氟硅酸

建立了一种新的检测蚀刻槽废氢氟酸中六氟硅酸的离子色谱方法。色谱柱为Metrosep A Supp 7阴离子交换柱,流动相为3.2 mmol/L碳酸钠-1.0 mmol/L碳酸氢钠,流速为0.7 mL/min。六氟硅酸经过抑制型电导检测器后进行衍生化反应,在360 nm波长下用紫外检测器检测。六氟硅酸的线性范围为2.4~120 mg/L,相关系数r²大于0.999,定量限为0.24 mg/L,平均加标回收率为97.2%。本方法还可以同时利用电导检测器检测废氢氟酸中的氢氟酸、醋酸、盐酸、硝酸、磷酸和硫酸的含量。该方法快速、准确,适用于蚀刻槽液中六氟硅酸的检测。     

8-Phenyl-(4-oxy-acetic acid N-hydroxysuccinimidyl ester)-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene as a new highly fluorescent-derivatizing reagent for aliphatic amines in disease-related samples with high-performance liquid chromatography

A novel fluorescent-activated ester, 8-phenyl-(4-oxy-acetic acid N-hydroxysuccinimidyl ester)-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (TMPAB-OSu) has been designed and synthesized for amine labeling in HPLC. Being used 11 aliphatic amines as the models, the derivatization conditions were optimized. In 0.2 mol/l borate buffer (pH 8.8), amines reacted with TMPAB-OSu at 30 °C to form the derivatives in 10 min. The fluorescent quantum yield of TMPAB-OSu and its amine derivatives are high even compared with fluorescein. The separation of these amine derivatives was achieved with a C₈ column and gradient elution by using 0.1 mol/l sodium acetate buffer (pH 5.0) and methanol. With fluorescence detection at an emission wavelength of 509 nm and an excitation wavelength of 497 nm, the detection limits of aliphatic amines were 2–18 fmol, at a signal-to-noise ratio of 3:1. The proposed TMPAB-OSu-based HPLC method has been applied to the analysis of urine samples of health, hepatic and renal patients and lake water. Recoveries from different matrices are from 96 to 104%, depending on the sample investigated.     

TLC for pharmaceutical analysis in resource limited countries

This review article discusses the sustainability and robust advantages of planar chromatography that are critical to the successful performance of product quality assessments in resource limited areas including field applications. Because of the robustness and ease of use, the training required for successful performance of the high performance thin layer chromatography (HPTLC) assessments is much lower than that of other technologies with comparable reproducibility such as high performance liquid chromatography (HPLC). Some of the successful applications of planar chromatography in resource limited countries are presented. It should be noted that these planar chromatographic technologies have much lower plate counts and therefore separation power than column technologies such as HPLC and gas liquid chromatography (GLC). However in finished pharmaceutical products there are generally few active ingredients which are assessed making the HPTLC adequate for these analyses. In addition at this time there is a much wider array of detection technologies available for HPLC and GLC.     

Extension of the application of the thermal in-situ reaction on NH2 layers to the detection of catecholamines in biological materials

Summary This article describes a thin-layer chromatographic method for the determination of catecholamines in human urine. Chromatographic separation on NH₂-modified silica gel layers is followed by in-situ visualization brought about by heating the plate. The use of this derivatization technique for other urine components, such as creatine, creatinine, uric acid and glucose, is also discussed.