Reversed-phase Adsorption Research Articles

Inner-Wall Coated Nanopipette Microextraction for Quantitative Analysis of Per- and Polyfluoroalkyl Substances in Single Cells Using Mass Spectrometry.

Per- and polyfluoroalkyl substances (PFASs) are a series of organic pollutants with potential cytotoxicity and biotoxicity. Accurate and sensitive detection of trace PFASs in single cells can provide insights into investigating their cytotoxicity, carcinogenicity, and mutagenicity. Here we report the development of an inner-wall coated nanopipette microextraction coupled with induced nanoelectrospray ionization mass spectrometry (InESI-MS) method and its application for rapid, sensitive, and accurate analysis of trace PFASs in single cells. A specially designed inner-wall coated nanopipette was prepared for sampling of the cytoplasm from a single cell, and the trace PFASs in the cytoplasm were selectively enriched into the coating via reversed-phase adsorption, ion bonding adsorption, and π-π interaction mechanisms. After the extraction, the cytoplasm was removed, and the enriched PFASs were then desorbed into some organic solvent, applying an alternating current (AC) voltage to the inner-wall coated nanopipette for InESI-MS analysis. The inner-wall coated nanopipette showed an exhaustive extraction to the trace PFASs in one single cell, and thus, the mass of each target analyte in the cytoplasm can be calculated via an internal standard calibration curve method, avoiding the measurement of ultrasmall volume cytoplasm for one single cell. By using the inner-wall coated nanopipette microextraction coupled with InESI-MS method, trace PFASs accumulated in the LO2 cells with pollutant exposure were successfully detected, and the accumulative behaviors and heterogeneities of PFASs in single cells were explored.

Protection and Active Decontamination of Dairy Cattle Heifers against Lipophilic Toxins (PCBs) from Diet.

We studied the effects of a hydrophobized reversed-phase feed adsorbent in the form of a polyoctylated polysilicate hydrogel (POPSH) on productivity indicators, metabolic adaptation, and on the level of polychlorinated biphenyls (PCBs) in the blood of growing Holsteinized black-and-white heifers during the transition period. Two groups of two-month-old heifers of 20 head each were used. The experimental group received POPSH in addition to the main diet. The use of the adsorbent led to an increase in daily weight gain by 19.9% and to a decrease in the total concentration of PCB congeners found in whole blood by 40%. The greatest decrease in concentration (35–52%) was observed for tetra-, penta- and hexachlorobiphenyls. These results demonstrate the possibilities of effective protection of calves from lipophilic toxins of feed and their active decontamination.

Research progress of microextraction by packed sorbent and its application in microvolume sample extraction

微萃取技术是分析化学领域发展迅速,且已经得到广泛应用的样品前处理技术。填充吸附剂微萃取(MEPS)是一种微量固相萃取技术,使用微量的吸附剂填充于微量注射器,通过反复抽推方式使样品多次流经吸附剂以完成样品吸附萃取过程,萃取后的样品可直接用于色谱分析。典型的MEPS萃取设备包括MEPS注射器和MEPS吸附床(BIN)。MEPS优化的主要因素为MEPS处理过程的参数,包括样品流速、样品量与样品萃取循环次数,吸附剂及淋洗、洗脱溶剂的种类和体积,还需要考虑样品基质对MEPS性能的影响和样品残留和重复使用问题。MEPS中最重要的部分是吸附剂,主要有商品化的MEPS吸附剂,包括硅基的Silica、C18、C8等,碳材料的Hypercarb和聚苯乙烯聚合物类的SDVB、HDVB吸附剂等。研究用的吸附剂包括分子印迹材料、限进分子印迹材料、碳基材料、导电聚合物类材料、改性硅基材料及共价-有机骨架材料等。MEPS结合多种分析仪器已经成功应用于从不同基质中提取单一或多种分析物,所涵盖基质包括生物样品(尿液、唾液、血浆或血液)、河流水体或生活污水以及几种食品和饮料。MEPS处理复杂生物基质样品时,通常需要稀释样品、除蛋白质等预处理。MEPS具有需要样品体积小、操作快速等特点,在生物基质样品分析中有望得到更广泛的使用。在环境样品中,该技术可与现场便携仪器联用,未来将有望在现场进行快速检测,并于易分解样品等方面发挥作用。

Исследование молекулярно-массового распределения природных полисахаридов и полиацетиленов методом многомерной хроматографии

Методом многомерной жидкостной хроматографии с использованием ГПХ и обращеннофазовой адсорбционной хроматографии, исследовано молекулярно-массовые и функциональные харктеристики продуктов биосинтеза полисахаридов и полиацетиленовых соединений, базидиальными грибами рода Ganoderma lucidum и Pleurotus ostreatus. Указанные грибы выращивались методом глубинного культивирования в среде, состоящей из пшеничных отрубей на среде Чапека-Докса следующего состава (г/дм3): NaNO3 -2, K2HPO4 -1, MgSO4·7H2O-0.5, KCl-0.5, FeSO4·H2O-0.01, глюкоза-30 и H2O. Культивирование проводилось в термостате при 28оС. После 10 суток выдержки в составе их мицелл обнаружены полисахариды и полиацетиленовые соединения. Далее образующуюся биомассу грибов измельчали и экстрагировали метиловым эфиром уксусной кислоты и водой. Осадок и экстракт в отдельности разделены в указанной хроматографической системе. Установлено, что в водном экстракте количество полисахаридов достигает до 70-80%, а в эфирном экстракте содержание полиацетиленовых соединений меняется в пределах 65-70%. Таким образом, метод GPC позволил выявить в составе продуктов биосинтеза 5 фракций, в том числе 4 полисахаридов, состоящие из гексаозы (Мw=Mn=1085), гептаозы (Мw=Mn=1260) и из двух олигосахаридов с Мw и Mn 4390, 3600 и 5450, 4500, соответственно, и одна полиацетиленовая (Мw =180, Mn =150). Методом обращенно-фазовой адсорбционной хроматографии в рабочей волне УФ-детектора в составе полиацетиленовой фракции обнаружены 5 подфракций по химической природе относяхщихся к полиацетиленовым кислотам и спиртам сопряженными двойными и тройными связями в различных сочетаниях. С целью изучения химического состава обнаруживаемых подфракции, фракция полиацетилена подвергнута препаративному разделению. Разделение обеспечено в условиях повышенной концентрации экстракта, многократным сбором фракции по соответствующим пикам на АЖХ хроматограмме, которые далее были подвергнуты ИК-спектральному анализу и установлен их функциональный состав. Состав полиацетиленновых соединений подтвержден также хроматографически по объемам удерживания испытываемых соединений с применением соответствующих эталонов.

Hydrophobized Reversed-Phase Adsorbent for Protection of Dairy Cattle against Lipophilic Toxins from Diet. Efficiensy in Vitro and in Vivo.

The steady growth of inflammatory diseases of the udder in dairy cattle forces us to look for the causes of this phenomenon in the context of growing chemical pollution of the environment and feeds. Within the framework of this concept, an analysis was made of the polarity level of the three toxic impurity groups, which are commonly present in dairy cattle feeds. These impurities are presented by mycotoxins, polyaromatic hydrocarbons (PAH) and persistent organic pollutants (POP). It has been determined that 46% of studied mycotoxins (n = 1500) and 100% of studied polyaromatic hydrocarbons (n = 45) and persistent organic pollutants (n = 55) are lipophilic compounds, prone to bioaccumulation. A comparative evaluation of the sorption capacity of four adsorbents of a different nature and polarity with respect to the simplest PAH, naphthalene and lipophilic estrogenic mycotoxin, zearalenone in vitro has been carried out. The highest efficiency in these experiments was demonstrated by the reversed-phase polyoctylated polysilicate hydrogel (POPSH). The use of POPSH in a herd of lactating cows significantly reduced the transfer of aldrin, dieldrin and heptachlor, typical POPs from the “dirty dozen”, to the milk. The relevance of protecting the main functional systems of animals from the damaging effects of lipophilic toxins from feeds using non-polar adsorbents, and the concept of evaluating the effectiveness of various feed adsorbents for dairy cattle by their influence on the somatic cell count in the collected milk are discussed.

Liquid chromatography–mass spectrometry studies on the isomeric 1-fluorobenzyl-3-naphthoyl-indoles: FUB-JWH-018 and five isomers

One of the ongoing research subjects for forensic analysts is differentiating halogen positional isomers of newly-emerging synthetic cannabinoids. The purpose of this study is to elucidate liquid chromatographic and mass spectrometric conditions applicable to the differentiation of such derivatives. High-performance liquid chromatography (HPLC) coupled with triple quadrupole mass spectrometry (QqQ-MS) and linear ion trap time-of-flight mass spectrometry (IT-TOF-MS) using electrospray ionization (ESI) in its positive ion mode were utilized to analyze six model compounds, FUB-JWH-018 and five positional isomers having structures of 1- or 2-naphthoyl-substituted 1H-indole-3-carboxylates with N-substituted positional isomeric fluorobenzyl groups (2-fluorobenzyl, 3-fluorobenzyl, and 4-fluorobenzyl). The chromatographic separation of the six isomers was successfully achieved by HPLC using a pentafluorophenylpropyl-bonded reversed-phase adsorbent. The positive ESI-QqQ-MS could discriminate fluorobenzyl isomers having a same naphthoyl structure via the relative abundance of the two product ions in the collision-induced dissociation reaction. ESI-IT-TOF-MS in its positive ion mode successfully distinguished three ring positional isomers in both naphthoyl scaffolds on the basis of the differences in the abundance of oxomethylium ion attributed to C16H11FNO+ (m/z 252). The use of ESI-QqQ-MS and ESI-IT-TOF-MS in its positive ion mode coupled with LC using a pentafluorophenylpropyl-bonded silica column is applicable to MS-aided differentiation and the chromatographic separation of FUB-JWH-018 positional isomers.

Multilayer adsorption in liquid chromatography – The surface heterogeneity below an adsorbed multilayer

A numerical method was introduced for the estimation of the surface heterogeneity below an adsorbed multilayer of the analyte. The calculation procedure is based on the raw adsorption isotherm data points obtained by frontal analysis experiments. To permit the mapping of the nature of the analyte–surface interaction, a numerical procedure was used to pre-estimate the adsorbate–adsorbate interactions occurring during the adsorption process. The surface heterogeneity estimation was carried out using the affinity-energy distribution calculations with assuming local BET isotherm. In the local BET isotherm the pre-estimated adsorbate–adsorbate interaction constant was used, and the surface heterogeneity was described. After the test of the numerical method with benchmark isotherms, the algorithm was tested on several experimental isotherms. The isotherms were measured using phenol as test molecule on reversed phase adsorbents, with different surface coverage of the octadecyl ligands. The surface of the non-end-capped stationary phases showed detectable heterogeneity, while the surface end-capped phases were found to be homogeneous.

A simple method for measuring excess adsorption isotherms of organic eluent components on reversed-phase packing materials.

A simple frontal analysis method has been developed for the reliable measurement of excess adsorption isotherms of an organic component on reversed-phase adsorbents in a series of programmed concentration steps. In the present method, a peak, which is produced by refractive index change in column eluate, is detected at 589 nm; it represents the elution volume of the boundary. The method is applied to the measurement of the excess adsorption isotherms of organic eluent components from water on commercially available reversed-phase stationary phases. The results are in good agreement with the previously reported isotherms. We also measure the excess adsorption isotherms of organic eluent components from solutions containing electrolytes. There are not any interference peaks on the elution traces. The method is thus reliably applicable to the evaluation of the excess adsorption of organic eluent components in practical systems.

Coupling solid-phase microextraction with ambient mass spectrometry using surface coated wooden-tip probe for rapid analysis of ultra trace perfluorinated compounds in complex samples.

Coupling solid-phase microextraction (SPME) with ambient mass spectrometry using surface coated wooden-tip probe was achieved for the first time and applied in the analysis of ultra trace perfluorinated compounds (PFCs) in complex environmental and biological samples. We modified n-octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride on the surface of sharp wooden tip via silanization to form a novel SPME probe, which was then used for highly selective enrichment of PFCs from complex matrices and applied as a solid substrate to induce electrospray ionization for mass spectrometric analysis. The porous structural surface together with the dual extraction mechanisms (reversed phase adsorption and ion exchange adsorption) demonstrated that the SPME probe has an outstanding enrichment capacity, enhancing sensitivity by approximately 4000-8000 folds for the detection in aqueous samples, and 100-500-fold in whole blood and milk samples. The method showed good linearity, with correlation coefficient values (r(2)) of no less than 0.9931 for eight target PFCs. The limits of detection and qualification of the eight PFCs were 0.06-0.59 and 0.21-1.98 ng/L, respectively. Quantification of real samples was achieved by isotope internal standard calibration curve method or isotope dilution method, and ultratrace levels of PFCs present in lake water, river water, whole blood, and milk samples had been successfully detected and qualified.

Highly efficient N-glycoproteomic sample preparation by combining C18 and graphitized carbon adsorbents

Conventional N-glycoproteome analysis usually applies C18 reversed-phase (RP) adsorbent for sample purification, which will lead to unavoidable sample loss due to the high hydrophilicity of N-glycopeptides. In this study, a porous graphitized carbon (PGC) absorbent was combined with a C18 adsorbent for N-glycopeptide purification in comprehensive N-glycoproteome analysis based on the hydrophobic and polar interactions between carbon and N-glycans. It was observed that the small hydrophilic N-glycopeptides that cannot retain onto C18 adsorbent can be captured by the graphitized carbon, while the large hydrophobic N-glycopeptides that cannot retain onto the graphitized carbon can be feasibly captured by the C18 adsorbent. Comparing with sample purification by using C18 adsorbent only, 28.5 % more N-glycopeptides were identified by combining both C18 and PGC adsorbents. The C18-PGC strategy was further applied for both sample purification and pre-fractionation of a complex protein sample from HeLa cell. After hydrophilic interaction chromatography enrichment, 1,484 unique N-glycopeptides with 1,759 unique N-glycosylation sites were finally identified.

Reversible Immobilization of Chelating Affinity Surfactants on Reversed Phase Adsorbents for Protein and Peptide Separations under Metal Affinity Chromatography

Alkyl-bound silica was modified using chelating surfactants and the resulting adsorbent was used in immobilized metal affinity chromatography of proteins and peptides. Brij-76, a non-ionic amphiphilic surfactant with an alkyl moiety and an ethylene oxide chain, was reversible adsorbed to alkyl silica (C18). The hydroxyl group at the end of the ethylene oxide chain was chemically modified previously with an iminodiacetate functionality as chelating agent of transitional metal ions. Cu(II) was studied as immobilized ion for the adsorption of peptides and proteins. Three chromatographic supports were prepared having different Cu(II) capacities. For a low Cu(II) capacity case, the generated adsorbent behaved as a controlled access media preventing the adsorption of large molecular weight proteins, such as BSA, while small peptides, such as Angiotensin III, or amino acids could be retained. For a medium and high Cu(II) capacity, the synthesized adsorbent no longer behaved as a controlling access media and all molecules in this study, either large or small, were retained by the immobilized ion. Nonetheless, most of the BSA was strongly retained by the system and a pH change did not remove any of the adsorbed BSA while the small molecules were removed by the same pH change.

Multilayer adsorption on fractal surfaces

Multilayer adsorption is often observed in liquid chromatography. The most frequently employed model for multilayer adsorption is the BET isotherm equation. In this study we introduce an interpretation of multilayer adsorption measured on liquid chromatographic stationary phases based on the fractal theory. The fractal BET isotherm model was successfully used to determine the apparent fractal dimension of the adsorbent surface. The nonlinear fitting of the fractal BET equation gives us the estimation of the adsorption equilibrium constants and the monolayer saturation capacity of the adsorbent as well. In our experiments, aniline and proline were used as test molecules on reversed phase and normal phase columns, respectively. Our results suggest an apparent fractal dimension 2.88–2.99 in the case of reversed phase adsorbents, in the contrast with a bare silica column with a fractal dimension of 2.54.

Detection of nerve agent markers by liquid chromatography-mass spectrometry

An approach to the detection of metabolites of organophosphorous agents (OPA), such as O-iso-propylmethylphosphonic acid (detection limit, 4 ng/mL), O-pinacolylmethylphosphonic acid (0.6 ng/mL), and O-isobutylmethylphosphonic acid (1 ng/mL), in plasma samples was developed using liquid chromatography-mass spectrometry. The curves of the elutionxcretion of OPA metabolites were obtained for the samples of biological material of rats exposed to toxic substances. Determination was performed by mass spectrometry with electrospray ionization in the negative ion mode, using deprotonated molecules for detection. The biological samples were analyzed by reversed-phase chromatography using hydrophilic end-capped adsorbents. Solid phase extraction on reversed-phase adsorption cartridges containing a copolymer of styrene and divinylbenzene was proposed for sample preparation.

Influence of the solvation process on solute adsorption in reversed phase liquid chromatography

The adsorption isotherms of phenol were acquired by frontal analysis on six different reversed phase adsorbents from five different organic solvent solutions. The end-capped octadecyl columns only differed in the bonding density of the C 18 ligands. The inverse method was used to confirm the estimated isotherm parameters derived from the frontal experiments. The effect of the bonding density of the end-capped octadecyl bonded phase on the adsorption properties of phenol from different mobile phase compositions was investigated. The adsorption behavior of phenol has changed from Langmuir type to BET type with the change of the organic modifier and the bonding density of the adsorbent.

Multi-way analysis of retention of model compounds in thin-layer chromatography

Summary The thin-layer chromatographic (TLC) retention of 35 model compounds has been investigated with ten screening mobile phases on six normal-phase and seven reversed-phase adsorbents. The retention factors formed two cubes with dimensions 35 × 10 × 6 and 35 × 10 × 7, respectively, which enabled three-way analysis by PARAFAC. A one-component PARAFAC model was optimum in both cases and two-component models performed worse. The one-component model explained 78.8% of the variance in normal-phase chromatography and 94.2% of the variance in reversed-phase chromatography. These results showed that the major variability of the retention factor (RF) can be modelled as the product of three factors related to the substance itself, the mobile phase, and the adsorbent. RF modelling was substantially better than using k or RM (rate mobility) values.

Carbohydrate Study for 40 Years

This review describes the carbohydrate study and the natural product related to the glycoside chemistry. What shall the people in the field of pharmacognosy and natural products chemistry search in scene in future? Forty years before while isolating dimeric compound having naphthoquinonepyrone skeleton from the coloring material produced by the pathogen that hosted in wheat and caused rotten root disease, silica gel has to be treated with oxalic acid to reduce the absorbency before separation. However now a days, availability of reversed phase adsorbents for liquid chromatography has made the separation and isolation of complex compounds possible, easy and rapid. With the advancement of mechanical/physicochemical analytic methods, it has even been possible to isolate traces of compounds present in complex. This advancement has made it possible to determine structure of saponins and complex polysaccharides without decomposition and carry out in vitro bioassay at the same time using various cells on-line. Further, this review describes the oligosaccharide syntheses and biological activities of glycosphingolipids, focusing especially on those found in invertebrates.

Simultaneous LC Determination of Ergosterol, Tocopherols and Carotenoids in Foods

A simple and reliable liquid chromatographic method was worked out to simultaneously determine ergosterol, as biomarker of fungal contamination, tocopherols and carotenoids as important phytochemicals having antioxidant properties in foods. The method developed in the present work included alkaline hydrolysis of the food sample, solvent extraction, chromatographic separation and photodiode-array detection. The separation was performed on the newest generation of Zorbax reversed-phase adsorbent with extra dense bonding of organo-silane ligands with double end-capping. Gradient elution system starting with water containing methanol and ending with a mixture of methanol–isopropanol–acetonitrile was used. The separated compounds were detected by using photodiode-array detection at wavelength ranges of 190–700 nm with quantification accomplished at the maximum absorbance wavelength for each analyte. The method was validated on the basis of recovery, precision, linearity of the calibration curves, and limit of detection and quantification using standard materials for ergosterol, α-tocopherol and β-carotene. The method was successfully applied for the determination of important phytochemicals in some spice and herbal products. The lowest detectable limit of such constituents was between 0.1 and 0.5 μg g−1 food. Positive correlation was not found between the ergosterol content and fungal count number of spice red pepper subjected to thermal drying and ambient storage.

Method for estimating the residual silanol activity of reversed-phase chromatographic adsorbents

The retention of some organic bases on reversed-phase adsorbents was studied as a function of the concentration of KH2PO4 in the mobile phase. It was shown that, for some adsorbents, retention decreases with an increase in the salt concentration, while an opposite dependence was observed for the other adsorbents. Such behavior of adsorbates can be explained by the prevailing silanophilic interactions in the former case and hydrophobic interactions in the latter case. The observed dependence can be used to change the chromatographic selectivity in the analysis of complex mixtures containing organic bases and to assess the properties of reversed-phase columns. Diphenhydramine hydrochloride was proposed as a test substance to assess the properties of the columns in the analysis of multicomponent pharmaceutical preparations. It was used in the comparative study of the properties of some adsorbents.

Simple and rapid method for the isolation of forskolin from Coleus forskohlii by charcoal column chromatography

A simple, safe, rapid and economical method was developed for the isolation of high-purity forskolin from Coleus forskohlii roots using activated charcoal as an adsorbent in a column. The elution was carried out under reduced pressure to make the process rapid. Activated charcoal acted as a reversed phase adsorbent and allowed elution of forskolin without much impurities. The residue, obtained from the eluate was purified and crystallized using different solvent mixtures to obtain pure forskolin. The forskolin isolated was analyzed and characterized by UV, IR, RP-HPLC, electrospray ionization MS, 1H NMR and 13C NMR. The yield was 0.097% w/w (RSD 5.6%). The purity was 96.9% w/w (RSD 0.3%) as determined by RP-HPLC. The present method enables researchers to produce high-purity forskolin in their labs by using common chemicals.

Theoretical analysis of chromatographic peak asymmetry and sharpness by the moment method using two peptides

The analyses of peak shapes in chromatography are useful in operating chromatographic system. The asymmetry and sharpness of a chromatographic peak are estimated by the reversed-phase adsorption of two standard peptides (angiotensin II bradykinin) on C18. In this work, the average particle diameters of C18 were 5 and 15 μm, while the pore sizes were 100 and 300 A. The composition of the mobile phase was 50/50 vol. % of a binary mixture of acetonitrile and water with 0.1% TFA, and the particles were packed in a stainless column (4.6×150 mm). The third and the fourth central movement were calculated from the chromatographic elution curves by moment analysis. The peak asymmetry was determined by two theoretical calculations: the asymmetry factor by elution peak analysis and skewness with moment analysis. The sharpness was estimated by the fourth central moment. In this work, the most acceptable skewness was calculated when the pore size was 300 A. The large excess was observed on small pore size.