Enhanced sensitivity of LC-MS analysis of permethylated N-glycans through online purification

Aberrant glycosylation of proteins and lipids has been implicated in many human diseases, thus prompting the need for reliable analytical methods that permit dependable quantification of glycans originating from biological specimens. MS of permethylated glycans is currently employed to monitor disease-related aberrant glycosylation of proteins and lipids. However, enhancing the sensitivity of this type of analysis is still needed. Here, analysis of permethylated glycans at enhanced sensitivity is attained through miniaturized solid-phase permethylation and online solid-phase purification. Solid-phase permethylation method was miniaturized by reducing the amount of sodium hydroxide beads (one-third the original amount) packed in microspin columns. The efficiency of glycan permethylation was not adversely affected by this reduction. Online solid-phase purification of permethylated N-glycans derived from model glycoproteins, such as fetuin, α-1 acid glycoprotein and ribonuclease B, offered more sensitive and reproducible results than offline liquid-liquid and solid-phase extractions. Online solid-phase purification method described here permitted a 75% increase in signal intensities of permethylated glycans relative to offline purification methods. This is mainly due to the minimized sample handling associated with an online cleaning procedure. The efficiency and utility of online solid-phase purification was also demonstrated here for N-glycans derived from human blood serum. Online solid-phase purification permitted the detection of 73 N-glycan structures, while only 63 glycan structures were detected in the case of samples purified through liquid-liquid extraction. The intensities of the 63 structures that were detected in both cases were 75% higher for samples that were purified through the online method.     

Comparison of liquid-liquid and solid-phase extraction techniques for drugs in urine and effects on the lifetime and performance of fused-silica capillary columns

Contamination of a gas chromatographic system with involatile sample residues will cause degradation of the chromatograms. Deposition of sample residues from urine extracted by a liquid-liquid and a solid-phase cartridge extraction method for drugs of abuse is compared. Standards containing five different drug compounds were injected into a gas chromatograph equipped with a fused-silica capillary column following injections of urine extracts prepared by the two different extraction methods. The samples extracted by the liquid-liquid method contaminated the chromatographic system to a greater extent and much faster than those extracted by the solid-phase extraction method.     

Study on a novel circulating cooling solid-phase microextraction method

A novel solid-phase microextraction (SPME) setup, circulating cooling solid-phase microextraction (CC-SPME), is developed for determining organochlorine pesticides (OCPs) in water. The linearity area of this method is 0.5-120 microg/l, its RSD value is less than 10% and detection limit is in the low ng/l when it is used to detect gamma-hexachlorocyclohexane, which is better than traditional headspace SPME (HS-SPME) and direct immersion SPME (DI-SPME) methods. The influence of factors such as pH, ionic intensity, adsorption time, and adsorption temperature were also investigated, respectively.     

The Comparison of Different Stationary Phases for the Analysis of Methamphtamine by Solid-phase Microextraction (SPME) and Gas Chromatography——Mass Spectrometry (GC/MS)

Methamphtamine is a kind of drug used as central nervous system stimulants, which has been widely abused. The drug is analyzed both for therapeutic value and in forensic medicine and toxicology. Though liquid-liquid extraction and solid-phase extraction are two kinds of common extractant method for the analysis of methamphtamine in urine,they both need high purity solvent. Recently, Lord et.al reported the method optimization for the analysis of amphetamines in urine by head-space solid-phase microextraction. Compareing with the liquid-liquid extraction and solid-phase extraction, solid-phase microextraction has the advantages of more simple, quick operation, high efficiency and solvent free.     

Concentration of organic compounds in natural waters with solid-phase dispersion based on advesicle modified silica prior to liquid chromatography

The ability of vesicle-coated silica to aid the extraction of organic compounds from water prior to liquid chromatographic analysis is presented for the first time. The method is based on the formation of silica supported cationic multi-lamellar vesicles of gemini surfactants inherently ensuring the presence of hydrophilic and hydrophobic sites for the partitioning of analytes bearing different properties. Method development is illustrated by studying the adsolubilization of UV absorbing chemicals from swimming pool water. Due to the requirement for external energy input (intense shearing) a method based on solid-phase dispersion (SPD) was applied producing better results than off-line solid-phase extraction (SPE). Meticulous investigation of the experimental parameters was conducted in order to elucidate the mechanisms behind the proposed extraction pattern. Analyte recoveries were quantitative under the optimum experimental conditions offering recoveries higher than 96% with RSD values below 5%.     

超声波溶剂提取-气相色谱法测定烟草及烟草制品中19种有机氯农药残留

建立了超声波溶剂提取-气相色谱法同时测定烟草及其制品中19种有机氯农药残留。样品采用正己烷-丙酮超声提取,经Florisil固相萃取柱净化后,采用气相色谱-电子捕获检测法(GC-ECD)进行检测。结果发现,19种有机氯农药加标回收率均在72%以上,相对标准偏差(RSD)在0.1%～9.0%,能满足当前烟草中有机氯农药残留的同时快速检测要求。     

Determination of 1-naphthylacetic acid in commercial formulations and natural waters by solid-phase spectrofluorimetry

A method for the determination of trace amounts of 1-naphthylacetic acid (NAA) has been developed, based on solid-phase spectrofluorimetry. The relative fluorescence intensity of NAA fixed on Sephadex QAE A-25 gel was measured directly after packing the gel beads in a 1-mm silica cell, using a solid-phase attachment. The wavelengths of excitation and emission were 280 and 336 nm, respectively. The applicable concentration range was from 0.3 to 18 ng/ ml, with a relative standard deviation of 1.4% (for a level of 9 ng/ml) and a detection limit of 0.09 ng/ml. The method was applied to the determination of NAA in commercial formulations and natural waters. The method is more sensitive and selective than other methods described in the literature.     

膜萃取-气相色谱/质谱法测定瓶装饮用水中27种有毒有害物质含量

利用C18固相萃取膜与气质联用(GC-MS)技术建立了瓶装饮用水中27种痕量化合物多残留同时检测的方法.水中被测物多残留通过C18固相萃取膜富集,丙酮洗脱,旋转蒸发与吹氮浓缩,GC/MS选择离子监测模式(SIM)测定.被测物加标回收率在60%～120%之间,相对标准偏差小于25%.     

Microwave-assisted solid-phase synthesis of 2,5-diketopiperazines: solvent and resin dependence

Solid-phase synthesis of diketopiperazines (DKPs) was preformed using various combinations of resins (polystyrene, TentaGel, ArgoGel, and PEGA) and solvents (toluene, tert-butyl alcohol, water, and toluene/2-butanol (1:4, v/v). The DKPs were synthesized from solid-phase bound dipeptides via intramolecular aminolysis. Both thermal and microwave-assisted solid-phase synthesis of DKPs gave high yields of products independently of resin and organic solvent used; however, only the PEGA resin resulted in high yields of DKPs in water independent of heating method. The short reaction times, high yields, and the possibility to run reactions in water when an appropriate resin is used makes the microwave-assisted solid-phase synthesis the method of choice. The method should be suitable for solid-phase synthesis of diketopiperazine-based libraries.     

糖肽的固相合成

目前糖肽的固相合成可以分为两种策略：构建单元策略和固相糖基化策略。本文对O-连接和N-连接糖肽固相合成的研究进展进行了综述。     

Determination of cyanide by a flow injection analysis-atomic absorption spectrometric method

A new flow injection analysis (FIA) procedure is proposed for the indirect atomic absorption spectrometric determination of cyanide. The FIA manifold is based on the insertion of the sample into a distilled water carrier, then the sample flows through a solid-phase reactor filled with silver iodide entrapped in polymeric resin beads. The calibration graph is linear over the range 0.2-6.0 mg l-1 of cyanide (correlation coefficient 0.9974), the detection limit is 0.1 mg l-1, the sample throughput is 193 h-1 and the RSD is 0.8%. The method is simple, quick and more selective than other published FIA procedures. The reproducibility obtained by using different solid-phase reactors and solutions is in the range 2.2-3.1% (RSD). The method was applied to the determination of cyanide in commercial samples such as pharmaceutical formulations and industrial electrolytic baths.     

Ultrasensitive determination of 1,4-dihydroxybenzene based on fluorescence resonance energy quenching of luminescent quantum dots modified on surface of silica nanoparticles

An ultrasensitive solid-phase fluorescence resonance energy quenching (FREQ) method for determination of 1,4-dihydroxybenzene (DHB) using mercaptosuccinic acid (MSA)-capped CdTe quantum dots (QDs) immobilized on silica nanoparticles (NPs) as donors was developed. In the method, silica NPs were first modified with 3-aminopropyltriethoxysilane (APTS). Then, MSA-capped CdTe QDs were immobilized on the surface of the APTS-modified silica NPs. Finally, DHB in the solution was attached to the empty sites on the surface of silica NPs with QDs through electrostatic interaction. The fluorescence emission of the QDs was quenched by the proximal DHB molecules on the silica NPs. The quenching efficiency of the solid-phase FREQ method was 200-times higher than that of the solution-phase FREQ method. Using the ultrasensitive solid-phase FREQ method, DHB as low as 2.4 × 10⁻¹² mol/L could be detected. The method was applied to quantify trace DHB in water samples.     

分散固相萃取气相色谱-负化学离子源质谱法测定大豆和玉米中20种农药的残留量

建立了一种大豆和玉米中20种农药残留量的分散固相萃取气相色谱-负化学离子源质谱分析方法。样品经乙腈提取并浓缩后加入N-丙基乙二胺（PSA）、石墨化碳黑和C18 3种填料进行分散固相萃取净化,气相色谱-负化学离子源质谱分时段选择离子监测技术测定与确证,外标法定量。所有农药在20～400 μg/L范围内线性均良好;方法的定量限(LOQ)均不高于2 μg/kg;在5,10和20 μg/kg 3个添加水平下所有农药的平均回收率均处于70%～130%之间,相对标准偏差(RSD)低于17%;运用该方法检测大豆和玉米样品时没有干扰现象。     

Comparison of Solid-Phase Extraction and Liquid-Liquid Extraction Methods for Liquid Chromatographic Determination of Diltiazem and its Metabolites in Plasma

Abstract

A rapid solid-phase extraction method for the determination of diltiazem and its metabolites from plasma was compared to a conventional liquid-liquid extraction procedure we have described previously. Analytical recovery for all compounds was greater than 90 % for solid-phase extraction whereas for liquid-liquid extraction, mean recovery ranged from 67 to 82 %. The increase of extraction efficiency was closely related to an improvement of the detection limit for the metabolites. Solid phase extraction procedure was found to be more convenient, rapid and sensitive than liquid-liquid extraction and represents a useful analytical tool for the monitoring of diltiazem and its metabolites in clinical investigations.     

用于放射性卤代药物合成的高速无载体固相标记法

本文研究了一种适合于卤素标记化合物的高分子氧化剂的合成及其性能, 研究了适合于某些卤代放射性药物合成的高速、无载体产物的固相标记法和固相反应。 用于肿瘤探针的药物带电诺丹明和肾功能显像剂胆固醇在固定化后, 将这两种药物进行固相法碘标记并对产物进行了鉴定, 得到了放射化学纯度大于95%, 放射性回收率高于96%的标记化合物, 实现了5分钟内完成放射性标记药物无需分离就可得到极高放化纯产物的高速标记法。本文还对其它能生成有机汞化合物的固相标记法进行了讨论。     

多孔芳香骨架吸附剂-固相萃取-高效液相色谱法同时测定辣椒粉中4种偶氮类染料

建立了固相萃取-高效液相色谱同时测定辣椒粉中对位红、酸性橙Ⅱ、苏丹红Ⅰ和苏丹红Ⅱ 4种偶氮染料的方法。以多孔芳香骨架-6（PAF-6）材料作为固相萃取吸附剂，考察并获得了影响自制固相萃取柱的萃取效率和吸附容量等主要因素。在优化条件下，4种目标分析物的检出限（LOD）为1.5~7.0 μg/L（信噪比S/N=3），定量限（LOQ）为5.0~22.1 μg/L（S/N=10），加标回收率为76.5%~89.8%，相对标准偏差（RSD）均不大于5.3%（n=6）。此外，基于量子化学计算，考察了PAF-6与目标分析物之间的相互作用机制，结果表明，目标分析物可以稳定地吸附在PAF-6分子上。该方法准确可靠，具有良好的回收率和较高的灵敏度，可用于辣椒粉中4种偶氮类染料的检测。     

Analysis of free and bound phenolics in wine and grapes by GC–MS after automated SPE

The results of validation of a method for the analysis of free and bound phenolics in wine and grapes are presented. Wine and grape extracts are fractionated by automated solid-phase extraction on Bond Elut PPL cartridges to give free and bound phenolic fractions. Bound fractions are subjected to acid hydrolysis, and the phenolics released are recovered by solid-phase extraction on Bond Elut PPL cartridges. The fractions are further purified by automated solid-phase extraction on Bond Elut silica cartridges. After derivatisation to form trimethylsilyl ethers, the phenolics are determined by gas chromatography–mass spectrometry with selected ion monitoring. The method is suitable for robust, high-throughput monitoring of the concentrations of phenolics that can affect the palatability of wine.     

Miniaturized matrix solid-phase dispersion and solid-phase clear-up combined with capillary electrophoresis for efficient determination of trace bioactive components in complicated sample matrix: Take Wubi Shanyao Pill as an example

Accurate quantitative analysis of trace analytes in a complicated matrix is a challenge in modern analytical chemistry. An appropriate analytical method is considered to be one of the most common gaps during the whole process. In this study, a green and efficient strategy based on miniaturized matrix solid-phase dispersion and solid-phase extraction combined with capillary electrophoresis was first proposed for extracting, purifying and determining target analytes from complicated matrix, using Wubi Shanyao Pill as an example. In detail, 60 mg of samples were dispersed on MCM-48 to obtain high yields of analytes, then the extract was purified with a solid-phase extraction cartridge. Finally, four analytes in the purified sample solution were determined by capillary electrophoresis. The parameters affecting the extraction efficiency of matrix solid-phase dispersion, purification efficiency of solid-phase extraction and separation effect of capillary electrophoresis were investigated. Under the optimized conditions, all analytes demonstrated satisfactory linearity (R²>0.9983). What's more, the superior green potential of the developed method for the determination of complex samples was confirmed by the Analytical GREEnness Metric Approach. The established method was successfully applied in the accurate determination of target analytes in Wubi Shanyao Pill and thus provided reliable, sensitive, and efficient strategy support for its quality control.     

Separation of polyphenols in Canary Islands wine by capillary zone electrophoresis without preconcentration

A method for separation and determination of polyphenols in wine by capillary zone electrophoresis (CZE) without any preconcentration step is described. The sensitivity and limits of detection for gentisic and p-coumaric acid are better than those previously published. The effect of a possible C18 solid-phase extraction prior to the CZE analysis was examined. The developed optimized method (without any extraction step) was applied to the analysis of wines from Tenerife, Canary Islands.