Conventional C18 Research Articles

Investigation on the Retention and Separation of Glucosinolates With a Mixed-Mode Reversed-Phase/Weak Anion-Exchange Column.

Glucosinolates, a crucial group of secondary metabolites in Brassica vegetables, present significant chromatographic separation challenges due to their anionic form, structure diversities, and co-existence of other phenolic compounds. This study comparatively investigated the retention and separation of seven glucosinolates using a mixed-mode reversed-phase/weak anion-exchange column and a conventional reversed-phase C18 column. Separation factors for each glucosinolate with its adjacent peaks were over 1.0 on the mixed-mode column, while co-eluting was observed on the C18 column. The effects of mobile phase additives and pH on the separation and retention of glucosinolates were also investigated. Results showed that glucosinolate retention was inversely related to both buffer concentration and pH. The optimized method for the mix-mode column was applied to the complex Brassica vegetable samples. In addition to the 17 well-resolved glucosinolate peaks, 34 peaks for phenolic compounds were identified in broccoli microgreen, suggesting the successful application scenarios for qualitative analysis in comparison with the single mode reverse phase C18 column. This study demonstrates that the mixed-mode reversed-phase/weak anion-exchange column can be used as a promising separation tool for organic anions in a complex sample matrix.

Ionic-liquid/Carbowax 20 M functionalized capsule phase microextraction platform for the extraction of phosphodiesterase-5 inhibitors from human serum and urine prior to their determination by LC–MS

Capsule phase microextraction (CPME) is an efficient bioanalytical technique that streamlines the sample preparation by integrating the filtration and stirring mechanism directly into the device. A novel composite sorbent designed to be selective towards the target analytes consisting of mixed-mode sorbent chemistry synthesized by sol–gel technology is found promising and superior to the conventional C18 sorbents. Herein we describe the encapsulation of an ionic liquid (IL)/Carbowax 20M-functionalized sol–gel sorbent (sol–gel IL/Carbowax 20 M) in the lumen of porous polypropylene tubes for the capsule phase microextraction of three phosphodiesterase-5 inhibitors namely avanafil, sildenafil, and tadalafil in human serum and urine samples. The CPME device was characterized by Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared Spectroscopy (FT-IR). The experimental parameters of CPME procedure (e.g. sample pH and ionic strength, extraction time, stirring rate, elution solvent and volume) were carefully optimized to achieve the highest possible extraction efficiency for the analytes. Method validation was conducted in terms of precision, linearity, accuracy, matrix effect, lower limits of quantification, and limits of detection (LOD). The method linearity was investigated in the range of 50–1000 ng mL−1 for all analytes while the precision was less than 11.8 % in all cases. For all analytes, the LOD values were 17 ng mL−1. The IL/CW 20M-functionalized microextraction capsules could be reused at least 25 times both for urine and serum samples. The green character and the applicability of the proposed method were evaluated using the ComplexGAPI and BAGI indexes. The optimized CPME protocol exhibited reduced consumption of organic solvent and generation of waste, cost-effectiveness, and simplicity. Finally, the proposed method was successfully applied to the analysis of sildenafil in human urine after administration of drug-containing formulation.

Ammonium bicarbonate buffers combined with hybrid surface technology columns improve the peak shape of strongly tailing lipids

BackgroundLipids such as phosphatidic acids (PAs) and cardiolipins (CLs) present strongly tailing peaks in reversed phase liquid chromatography, which entails low detectability. They are usually analyzed by hydrophilic interaction liquid chromatography (HILIC), which hampers high-throughput lipidomics. Thus, there is a great need for improved analytical methods in order to obtain a broader coverage of the lipidome in a single chromatographic method. We investigated the effect of ammonium bicarbonate (ABC) on peak asymmetry and detectability, in comparison with ammonium formate (AFO) on both a conventional BEH C18 column and an HST-CSH C18 column. ResultsThe combination of 2.5 mM ABC buffer pH 8 with an HST-CSH C18 column produced significantly improved results, reducing the asymmetry factor at 10 % peak height of PA 16:0/18:1 from 8.4 to 1.6. Furthermore, on average, there was up to a 54-fold enhancement in the peak height of its [M − H]- ion compared to AFO and the BEH C18 column. We confirmed this beneficial effect on other strongly tailing lipids, with accessible phosphate moieties e.g., cardiolipins, phosphatidylinositol phosphate, phosphatidylinositol bisphosphate, phosphorylated ceramide and phosphorylated sphingosine. Furthermore, we found an increased detectability of phospho- and sphingolipids up to 28 times in negative mode when using an HST-CSH C18 column. The method was successfully applied to mouse liver samples, where previously undetected endogenous phospholipids could be analyzed with improved chromatographic separation. SignificanceIn conclusion, the use of 2.5 mM ABC substantially improved the peak shape of PAs and enhanced the detectability of the lipidome in negative mode on an RPLC-ESI-Q-TOF-MS system on both BEH C18 and HST-CSH C18 columns. This method provides a wider coverage of the lipidome with one single injection for future lipidomic applications in negative mode.

Proteomic Analysis of Human Saliva via Solid-Phase Microextraction Coupled with Liquid Chromatography-Mass Spectrometry.

Proteomics of human saliva samples was achieved for the first time via biocompatible solid-phase microextraction (bio-SPME) devices. Upon introduction of a porogen to a conventional C18 coating, porous C18/polyacrylonitrile (PAN) SPME blades were able to extract peptides up to 3.0 kDa and more peptides than commercial SPME blades. Following Trypsin digestion, salivary proteomic analysis was achieved via SPME-LC-MS/MS. Seven endogenous proteins were consistently identified in all saliva samples via bio-SPME. Taking advantage of this strategy, untargeted peptidomics was applied for the comparison of saliva samples between healthy and SARS-CoV-2 positive individuals. The results showed clear peptidomic differences between the viral and healthy saliva samples. This proof-of-concept study demonstrates the potential of bio-SPME-LC-MS/MS for peptidomics and proteomics in biomedical applications.

Unveiling Coformulants in Plant Protection Products by LC-HRMS Using a Polyhydroxy Methacrylate Stationary Phase.

A polyhydroxy methacrylate-based stationary reversed phase was used for the determination of coformulants in 20 plant protection products (PPPs). These samples were analyzed by liquid chromatography coupled to Q-Orbitrap high-resolution mass spectrometry (LC-Q-Orbitrap-HRMS) in full-scan MS and data-dependent acquisition (ddMS2) modes. A total of 92 coformulants were tentatively identified in these formulations by nontargeted and unknown analyses. Twelve out of them were quantified by analytical standards. The most concentrated coformulant was the anionic surfactant dodecylbenzenesulfonic acid, whose highest content was obtained in the Score 25 sample (6.87%, w/v). Furthermore, triethylene glycol monomethyl ether, 4-s-butyl-2,6-di-tert-butylphenol, 1-ethyl-2-pyrrolidone, sorbitan monostearate, 2,6-dimethylaniline, palmitamide, and N-lauryldiethanolamine were quantified for the first time in these products. Hence, the polyhydroxy methacrylate-based stationary phase increased the identification of new coformulants in PPPs, being complementary to conventional C18. This strategy could be applied in future studies to estimate potential coformulant residues from PPPs applied to crops.

Utility of “flip-flop” chromatography employing silica hydride stationary phases with simultaneous photodiode array ultraviolet and single quadrupole mass detection for the analysis of seized drugs

For confirmation and/or screening purposes, rapid, selective, and precise chromatographic methods are required. In this vein, the utility of SiH columns (C18, UDC Cholesterol, and Diamond Hydride) with photodiode array UV absorption and single quadrupole MS detection for multi-modal separation of representative drugs from different drug classes on a single column using the same solvent reservoirs was investigated. For a conventional two column approach employing a combination of conventional C18 and silica columns operating in both the reversed phase chromatographic and hydrophilic interaction chromatographic modes, gradient analysis is required for the first column and there is a lack of retention on the second column for non-amine analytes. In comparison, all analytes are retained for two relatively rapid (< 10 min), precise (% RSD <0.4%), and non-correlated isocratic separations (R2=0.2115) when using a UDC Cholesterol column.

Determination of 15 carbonyl compounds in soil using improved solid phase extraction-high performance liquid chromatography

An improved solid phase extraction (SPE)-high performance liquid chromatography method was established to determine 15 carbonyl compounds, namely, formaldehyde (FOR), acetaldehyde (ACETA), acrolein (ACR), acetone (ACETO), propionaldehyde (PRO), crotonaldehyde (CRO), butyraldehyde (BUT), benzaldehyde (BEN), isovaleraldehyde (ISO), n-valeraldehyde (VAL), o-methylbenzaldehyde (o-TOL), m-methylbenzaldehyde (m-TOL), p-methylbenzaldehyde (p-TOL), n-hexanal (HEX), and 2,5-dimethylbenzaldehyde (DIM), in soil. The soil was ultrasonically extracted with acetonitrile, and the extracted samples were derivatized with 2,4-dinitrophenylhydrazine (2,4-DNPH) to generate stable hydrazone compounds. The derivatized solutions were cleaned using an SPE cartridge (Welchrom® BRP) packed with N-vinylpyrrolidone/divinylbenzene copolymer. Separation was performed on an Ultimate® XB-C18 column (250 mm×4.6 mm, 5 μm), isocratic elution was performed with acetonitrile-water (65∶35, v/v) as the mobile phase, and detection was performed at a wavelength of 360 nm. The 15 carbonyl compounds in the soil were then quantified using an external standard method. The proposed method improves the sample processing method described in the environmental standard HJ 997-2018: Soil and sediment-Determination of carbonyl compounds-High performance liquid chromatography. A series of experiments revealed the following optimal conditions for soil extraction: acetonitrile as the extraction solvent, extraction temperature of 30 ℃, and extraction time of 10 min. The results showed that the purification effect of the BRP cartridge was significantly better than that of the conventional silica-based C18 cartridge. The 15 carbonyl compounds showed good linearities, and all correlation coefficients were above 0.996. The recoveries ranged from 84.6% to 115.9%, the relative standard deviations (RSDs) ranged from 0.2% to 5.1%, and the detection limits were 0.02-0.06 mg/L. The method is simple, sensitive, and suitable for the accurate quantitative analysis of the 15 carbonyl compounds in soil specified in HJ 997-2018. Thus, the improved method provides reliable technical support for studying the residual status and environmental behavior of carbonyl compounds in soil.

HPLC Determination of Biperiden in Solid Dosage Forms

A rapid, new analytical method, based on liquid chromatography with UV detection, has been developed and utilised for the determination of biperiden hydrochloride in solid dosage forms. The chromatographic separation was performed on a conventional C18 reversed phase column with a mobile phase composed of acetonitrile-buffer mixture. Ultraviolet detection was carried out at 205 nm. A rapid extraction procedure using ultrasonic bath obtained good extraction yield values for the analyte (≥ 98.4%). The method was developed specifically for routine analysis of biperiden in solid dosage forms in the applicable concentration range. The linearity and range of the method investigated for the assay of biperiden is between 2–6 μg mL−1. The method is selective and sufficiently precise. Thus, the method developed is suitable for routine analysis of biperiden.

Analysis of siRNA with Denaturing and Non-Denaturing Ion-Pair Reversed-Phase Liquid Chromatography Methods

In this paper, we describe denaturing and non-denaturing ion-pair reversed-phase liquid chromatography (RPLC) methods for analyzing small interfering ribonucleic acid (siRNA). Drug formulations consisting of one or two siRNA duplexes were analyzed in non-denaturing conditions at a low column temperature to separate intact duplexes from single-stranded oligonucleotide contaminants and quantify them. In a denaturing method, we used an elevated column temperature to ensure the denaturation of siRNA duplexes into their single-stranded oligonucleotide counterparts. The goal of the denaturing LC method was to investigate the impurities in daughter oligonucleotides in siRNA. A column with chemically modified C18 column hardware showed improvements in analytical performance for nucleic acids compared to a conventional C18 stainless-steel column with the same pore size.

Separation of ampicillin on polar-endcapped phase: Development of the HPLC method to achieve its correct dosage in cardiac surgery

AbstractThe accurate, simple, and selective reversed phase high performance liquid chromatography (RP-HPLC) has been established and validated for the determination of an antibiotic ampicillin (AMP) in human blood plasma. The SPE extraction was used for the sample preparation. Chromatographic separation was accomplished by a mobile phase containing 15 mM monopotassium phosphate solution of pH 3.3 and methanol (75:25, v/v) in an isocratic mode at a flow rate of 1.4 mL min−1 at 30 °C. The separation was evaluated on a column with a new polar-endcapped C18 stationary phase Arion® Polar C18 or well-known phase Luna® Omega Polar C18. Excellent linearity (R2 0.9998) was shown over range 10–300 mg L−1 with mean percentage recovery 90%. Peak shapes were symmetrical in both columns, Arion® Polar C18 and Luna® Omega Polar C18, with asymmetry factor of 1.0 and 1.4, tailing factor of 1.0 and 1.2, and retention factor of 4.6 and 5.6, respectively. The Arion® Polar C18 was almost 1.4-fold more effective than Luna® Omega Polar C18 phase. The LOQ for ampicillin was achieved 10 mg L−1 for Luna® Omega Polar C18 and 5 mg L−1 for Arion® Polar C18 using 20 µL of a solution containing 0.24 mg mL−1 of cephalexin as an internal standard.A number of articles dealing with the determination of ampicillin is limited, therefore, this study showed the HPLC method suitable for the determination of AMP in human blood plasma from patient who underwent elective cardiac surgical revascularization. In addition, the determination of AMP was also performed for the first time using an Arion® Polar C18 column, which effectively separated AMP from other compounds present in human blood plasma. This new polar-endcapped phase can help in separation of polar antibiotics or other polar compounds, which are unsuccessfully separated on conventional C18 column, and thus can help during method development.

Online Extraction Followed by LC-MS/MS Analysis of Lipids in Natural Samples: A Proof-of-Concept Profiling Lecithin in Seeds.

Sample preparation is usually a complex and time-consuming procedure, which can directly affect the quality of the analysis. Recent efforts have been made to establish analytical methods involving minimal sample preparation, automatized and performed online with the analytical techniques. Online Extraction coupled with Liquid Chromatography-Mass Spectrometry (OLE-LC-MS) allows a fully connected extraction, separation, and analysis system. In this work, the lecithin profile was investigated in commercial sunflower, almonds, peanuts, and pistachio seeds to demonstrate that the concept of extraction, followed by the online analysis of the extract, could be applied to analyze this class of analytes in such complex solid matrices without a prior off-line solvent extraction step. The extraction phase gradient method was optimized. Two different analytical columns were explored, one being a conventional C18 (50 × 2.1 mm, 1.7 µm SPP) and the other a novel self-packed SIGO-C18ec (100 × 0.5, 5 µm FPP), which resulted in better separation. The analysis repeatability was investigated, and suggestions to improve it were pointed out. A characteristic ion with a m/z of 184, related to lysophosphatidylcholine structure, was used to identify the lecithin compounds. The temperature effect on the chromatograms was also explored. In short, it was found that the OLE-LC-MS approach is suitable for the analysis of lecithin compounds in seeds, being a promising alternative for lipidomics approaches in the near future.

P-Terphenyl-based rigid stationary phases with embedded polar groups for liquid chromatography

Terphenyls are important building blocks for a wide range of functional molecules. Among the three isomers, p-terphenyl (C18H14) is particularly useful for the construction of optical devices on account of its unique structure. Herein, two rigid stationary phases bearing p-terphenyl as an external moiety and variable embedded carbamate groups (p-TerC with one embedded carbamate group and p-TerC2 with two embedded carbamate group) were presented. The proposed stationary phases were characterized by various means and evaluated in reversed-phase (RP) mode, using different classes of analytes, including polycyclic aromatic hydrocarbons (PAHs), alkylbenzenes, 4-alkylbiphenyls, substituted ureas, sulfonylureas, substituted sulfanilamides and aromatic acids. The comparison with conventional C18, several other polar-embedded aromatic and C18 equivalents indicated p-terphenyl-based stationary phases were featured by multiple retention mechanisms, involving π-π interaction, charge-transfer interaction, hydrogen-bonding and hydrophobic interaction in RP mode. A unusually high specificity to the analytes with linear structures was observed, as exemplified by an irreversible adsorption of tetracene and a readily separation of tetraphene and chrysene. The aliphatic linker used in the proposed stationary phases was an influential factor for retentivity, selectivity and column efficiency. Interestingly, p-TerC2 was operable in normal-phase mode for the separation of certain PAHs through polar-related interactions. The linear, rigid polyphenyl structure of p-terphenyl endowed the new stationary phase with distinctive chromatographic properties, in contrast to those of the preceding counterparts bonded with alkyl and/or polynuclear aromatic moieties.

Development and Application of Molecularly Imprinted Polymers for the Selective Extraction of Chlordecone from Bovine Serum

The widespread use of chlordecone (CLD), an organochlorine pesticide, until the 1990s to protect banana crops in the French West Indies led to significant pollution of water and soil and, subsequently, of bovine intended for human consumption. Carcasses are submitted to official controls based on perirenal fat CLD determination. In order to allow for pre-slaughter controls, a selective analytical method based on a molecularly imprinted polymer (MIP) associated to the LC/MS-MS method was developed to determine the level of CLD in bovine serum that can be collected before slaughter. Different synthesis conditions were therefore assayed by varying the nature of the monomer and of the porogen, and the most promising MIP in terms of selective retention for CLD (extraction recovery close to 100%) was completely characterized by solid-phase extraction (repeatability of the extraction procedure, of the synthesis, and of the cartridge filling) in pure medium. The capacity of the MIP was determined at 0.13 µmol g−1 of MIP. After application of a spiked bovine serum sample on the MIP, the selective retention was maintained (87 and 21%, respectively, on the MIP and on the corresponding non-imprinted polymer). Moreover, extraction on the MIP led to a cleaner extract compared to those issued from a conventional C18 sorbent.

Prediction of n-octanol/water partition coefficient of strongly ionized compounds by ion-pair reversed-phase liquid chromatography with silica-based stationary phase

反相液相色谱(RPLC)是测定正辛醇/水分配系数(log P)的有效方法,但由于缺少同类型模型化合物,RPLC在测定强离解化合物的log P时遇到挑战。该文在硅胶基质C18色谱柱上,采用离子抑制反相液相色谱(IS-RPLC)和离子对反相液相色谱(IP-RPLC)分别对中性化合物、酚酸、羧酸、磺酸及部分两性化合物的保留行为进行了系统研究。在IS-RPLC模式下,利用中性化合物、弱离解的酚酸和苯羧酸作为模型化合物,建立了表观正辛醇/水分配系数(log D)与纯水相保留因子对数值(log kw)的定量结构-保留行为关系(QSRR)模型,测定了19种离解化合物的log D值,作为后续IP-RPLC的模型化合物及验证化合物。在IP-RPLC模式下,将中性、弱离解和强离解化合物作为混合模型组,以溶质静电荷ne、氢键酸碱性参数A和B为桥梁,建立了线性良好的log D-log kw-IP模型,采用3种不同类型的离解化合物进行了外部验证实验,预测值误差低于10%,证实了模型的可靠性。在此基础上,预测了8种强离解化合物的log D7.0值(pH 7.0条件下的log D值)。研究表明,利用结构相关参数沟通不同类型的模型化合物,是实现IP-RPLC测定强离解化合物log D值的一种行之有效的方法。与聚乙烯醇基质色谱柱相比,通用型的硅胶基质色谱柱上尽管存在着更多的次级作用,但可以为强离解化合物log D的测定提供更灵活的选择。

Untargeted and targeted analysis of sarin poisoning biomarkers in rat urine by liquid chromatography and tandem mass spectrometry.

Chemical warfare agents continue to pose a real threat to humanity, despite their prohibition under the Chemical Weapons Convention. Sarin is one of the most toxic and lethal representatives of nerve agents. The methodology for the targeted analysis of known sarin metabolites has reached great heights, but little attention has been paid to the untargeted analysis of biological samples of victims exposed to this deadly poisonous substance. At present, the development of computational and statistical methods of analysis offers great opportunities for finding new metabolites or understanding the mechanisms of action or effect of toxic substances on the organism. This study presents the targeted LC-MS/MS determination of methylphosphonic acid and isopropyl methylphosphonic acid in the urine of rats exposed to a non-lethal dose of sarin, as well as the untarget urine analysis by LC-HRMS. Targeted analysis of polar acidic sarin metabolites was performed on a mixed-mode reversed-phase anion-exchange column, and untargeted analysis on a conventional reversed-phase C18 column. Isopropyl methylphosphonic acid was detected and quantified within 5 days after subcutaneous injection of sarin at a dose of 1/4 LD50. A combination of generalized additive mixed models and dose-response analysis with database searches using accurate mass of precursor ions and corresponding MS/MS spectra enabled us to propose new six potential biomarkers of biological response to exposure. The results confirm the well-known fact that sarin poisoning has a significant impact on the victims' metabolome, with inhibition of acetylcholinesterase being just the first step and trigger of the complex toxicodynamic response.

Comparison study of nanofibers, composite nano/microfiber materials, molecularly imprinted polymers, and core-shell sorbents used for on-line extraction-liquid chromatography of ochratoxins in Tokaj wines

On-line solid phase extraction coupled with liquid chromatography enables high sample throughput, preconcentration of analytes, efficient clean-up, and separation in a single step. Our comparison study focused on the selection of an optimal SPE sorbent for on-line extraction of ochratoxins A and B allowing fast and sensitive control of mycotoxin contamination. Four types of fibrous sorbents including polyethylene microfibers, polypropylene microfibers, polycaprolactone microfibers/nanofibers composite, and polycaprolactone microfibers/polyvinylidene difluoride nanofibers composite together with selective molecularly imprinted polymers, and conventional C18 core–shell particle sorbent were tested, and efficiency of extraction was compared in on-line mode. Clean-up efficiency and ability to remove matrix interferences with the subsequent chromatographic separation were optimized for all extraction materials followed by validation of the methods. Both nanofibers and molecularly imprinted polymer sorbents were packed in a stainless-steel cartridge and directly connected to the HPLC system. Only polyethylene microfibers among all the tested fibers achieved the selectivity desired for resolution of ochratoxins from the wine matrix with the validation parameters comparable to commercial C18 sorbent. The best results featuring a limit of detection 0.03–0.06 µg L-1, recoveries 92–97% with RSD < 2%, and only 6 min overall analysis time were obtained after extraction using C18 particles. Features including stability of fibers in organic solvents, under high pressure, and their multiple reusability were also proven. Comparison of several types of extraction sorbents for ochratoxins was demonstrated with their on-line extraction followed by liquid chromatography with fluorescence determination using Tokaj wine as a complex matrix.

Liquid chromatography-tandem mass spectrometry with a new separation mode for rapid profiling of the Z/E isomers of plant glucosylceramides

Plant glucosylceramide (GlcCer) is characterized by various long-chain bases (LCBs) containing a Z/E isomeric unsaturated bond at the Δ8 position. The isomer ratio of GlcCer is highly diversified among plant species and is involved in tolerance to membrane fluidity-associated stresses such as chilling and aluminum toxicity. Therefore, a plant GlcCer isomer-selective quantitative method is required, allowing further sphingolipidomic studies for crop breeding. We here report a new technique for rapid determination of the Z/E isomers of plant GlcCer. A Cholester column contains cholesteryl groups as the hydrophobic stationary phase and separated the GlcCer isomers more efficiently than a conventional C18 column. We also investigated various mobile phases and column temperatures. The optimized column, solvent, and temperature conditions provided comprehensive profiles of the Z/E ratios of GlcCer in crude extracts of plant materials in less than 20 min. This high-throughput method will facilitate the large-scale profiling of plant GlcCer isomers.

Enhancement of acidic lipid analysis by nanoflow ultrahigh performance liquid chromatography–mass spectrometry

Acidic lipids are associated with the regulation of the structure and function of membrane proteins. Therefore, accurate and highly precise analysis of acidic lipids is important for elucidating their biological roles and pathological mechanisms. In this study, an enhanced analytical method for the separation and quantification of acidic lipids, including phosphatidylserine (PS), phosphatidic acid (PA), cardiolipin, and their lyso-derivatives, was developed using nanoflow ultrahigh performance liquid chromatography–electrospray ionisation-tandem mass spectrometry. The separation and mass spectrometry detection of acidic lipids were optimised in terms of peak tailing and time-based separation efficiencies, with carbamate-embedded C18 as the stationary phase, in the presence of an appropriate liquid chromatography solvent modifier. This newly developed method was applied to analyse a lipid extract from porcine brain. A significant increase in the number of acidic lipids identified (176 vs. 134), including intact monolysocardiolipin (17 vs. 4), was observed with the new method compared with conventional C18. The quantification of acidic lipids was validated with plasma standard (NIST SRM 1950) spiked with a number of LPS and PS standards, and acceptable accuracy (<15%) was obtained. The present method was found to be reliable for the acidic lipid analysis based on qualitative results from tissue extract and plasma samples.

Preparative isolation of arylbutanoid-type phenol [(-)-rhododendrin] with peak tailing on conventional C18 column using middle chromatogram isolated gel column coupled with reversed-phase liquid chromatography.

Reversed-phase liquid chromatography coupled with middle chromatogram isolated gel column was employed for the efficient preparative separation of the arylbutanoid-type phenol [(-)-rhododendrin] from Saxifraga tangutica. Universal C18 (XTerra C18) and XCharge C18 columns were compared for (-)-rhododendrin fraction analysis and preparation. Although tailing and overloading occurred on the XTerra C18 column, the positively charged reversed-phase C18 column (XCharge C18) overcame these drawbacks, allowing for favorable separation resolution, even when loading at a on a preparative scale (3.69mg per injection). The general separation process was as follows. First, 365.0mg of crude (-)-rhododendrin was enriched from 165g Saxifraga tangutica extract via a middle chromatogram isolated gel column. Second, separation was performed on an XTerra C18 preparative column, from which 73.8mg of the target fraction was easily obtained. Finally, the 24.0mg tailing peak of (-)-rhododendrin on XTerra C18 column was selectively purified on the XCharge C18 analytical column. These results demonstrate that the tailing nonalkaloid peaks can be effectively used for preparative isolation on XCharge C18 columns.

Magnetic solid-phase extraction modified Quick, Easy, Cheap, Effective, Rugged and Safe method combined with pre-column derivatization and ultra-high performance liquid chromatography-tandem mass spectrometry for determination of estrogens and estrogen mimics in pork and chicken samples

In this study, conventional Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method was modified by magnetic solid-phase extraction (MSPE) for purification/pre-concentration of eleven estrogens and estrogen mimics from the extracts of pork and chicken muscles, prior to dansyl chloride (DNS-Cl) derivatization coupled with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) assay. Dual octadecyl- and 2-aminoethyl-3-aminopropyl- groups functionalized mesoporous silica core-shell magnetic nanoparticles (C18/NH2-Fe3O4@mSiO2 MNPs) were synthesized and employed as MSPE sorbent with remarkable aqueous compatibility in comparison with conventional C18 functionalized sorbent. The proposed MSPE is easier to handle than the traditional SPE purification process in QuEChERS method. The lab-prepared MNPs were characterized by transmission electron microscope (TEM), brunner-emmet-teller (BET), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric analysis (TGA) and vibrating sample magnetometer (VSM). Pre-column derivatization was conducted to significantly enhance the sensitivity of the analytes in MS/MS via analyzing their derivatives in positive ion mode instead of analyzing their original forms in negative ion mode. Under the optimal sample pretreatment and instrumental analysis conditions, the approach showed low limits of detection (LODs, 0.02‒3.00 µg kg–1), appropriate recoveries (81.1‒115.4%) and acceptable precisions (0.48‒15.1%, n = 6), with good feasibility and future prospect of trace compounds analysis in complex food samples.