Fused Silica Capillary Column Research Articles

Development of a unified method for the determination of legacy and metabolites of current pesticides in serum for exposure assessment.

The use of pesticides is often regarded as a fundamental aspect of conventional agriculture. However, these compounds have gained recognition as some of the oldest and most widely employed xenobiotic contaminants, necessitating effective strategies for human biomonitoring. In this context, a method was developed for the determination of 16 legacy organochlorine pesticides, 6 metabolites of current pesticides (2,4-D, malathion, parathion, fipronil, pyraclostrobin, cypermethrin, permethrin, cyfluthrin), and 1 triazine herbicide (atrazine) in serum. Samples were prepared with water, formic acid, acetonitrile, and ultrasound irradiation, followed by solid-phase extraction with Oasis Prime HLB. Subsequently, metabolites from current pesticides underwent derivatization using MTBSTFA with 1% TBDMSCl for analysis via gas chromatography-tandem mass spectrometry (GC-MS/MS), employing an SLB-5MS fused silica capillary column. Analytical curves were generated with limits of quantification from 0.3 to 4.0ng.mL-1. Accuracy ranged from 69 to 124%, and the coefficient of variation from 2 to 28%. Moreover, determining 1-(4-chlorophenyl)-1H-pyrazol-3-ol was suggested as a biomarker for pyraclostrobin biomonitoring. This analytical approach facilitated the determination of both legacy and metabolites of current pesticides in the same serum sample, presenting an interesting and cost-effective option for large cohorts, and multi-omics studies that evaluate time-dependent biomarkers in blood samples, thereby enabling biomonitoring within the same matrix. Furthermore, a proof-of-concept involving 10 volunteers demonstrated exposure to 9 pesticides at mean concentrations measured in ngmL-1, consistent with findings from various biomonitoring initiatives.

Single-drop microextraction application for the rapid and sensitive determination of endosulfan and its metabolites in water samples

This study aims to investigate the practical application of Single Drop Micro Extraction (SDME) as an efficient and sustainable technique for determining endosulfan and its metabolites in water. Experiments were performed with samples collected from different areas in the Loukkos region, Morocco, using a Finnigan MAT GCQ Model, equipped with a 30-m x 0.32-mm ID, ZB-5 (0.25-μm film thickness) fused-silica capillary column, Helium was used as a carrier gas (at 30 kPa), The ion trap mass spectrometer was operated in the electron ionization mode. The research highlights SDME's sensitivity in detecting and quantifying endosulfan and its metabolites in environmental samples, with achieved detection limits ranging from 0.3 to 0.5 μg/L. Furthermore, this study underscores the innovative potential of SDME by showcasing its compatibility with advanced detection techniques. These approaches have the potential to enhance sensitivity even further, potentially lowering detection limits to more stringent levels. Another notable aspect of SDME is its substantial reduction in solvent consumption, effectively minimizing costs and diminishing the ecological footprint associated with pesticide analysis. SDME may be considered a promising method due to its simplicity, cost-effectiveness, and eco-friendliness

A Novel Validated HS-GC-MS method for the trace level determination of Acetyl chloride as Isopropyl acetate in various anti-cancer drug substances

A novel, simple and precise headspace gas chromatography-mass spectrometry (HS-GC-MS) method was developed and validated for the determination of acetyl chloride (AC) in various anti-cancer drug substances like bendamustine HCl, Ibrutinib, trifluridine and abemaciclib drug substances. In this methodology, AC reacts with isopropyl alcohol and is converted into isopropyl acetate. Hence AC is quantified as Isopropyl acetate. The lower level of detection was achieved on the capillary GC column (DB-624, Fused silica capillary column; 30 m length; 0.32 mm internal diameter, coated with 6% Cyanopropylphenyl and 94% dimethyl polysiloxane stationary phase of 1.8 μm film thickness) with electron impact ionization (EI) technique by GC-MS in selective ion monitoring (SIM) mode. The mass ions were selected for the quantifier is 63 and the qualifier is 87 for isopropyl acetate. The performance of the method was assessed by evaluating the specificity, linearity, sensitivity, precision, accuracy and robustness experiments. The established limit of detection and limit of quantification values for the AC were 0.1 and 0.3 μg/g, respectively. This developed method was found to be linear with a correlation coefficient is greater than 0.999 for all four drug substances. The average recoveries of AC in bendamustine HCl, ibrutinib, trifluridine and abemaciclib were obtained 106.1, 109.0, 97.4 and 101.6%, respectively. The proposed method was validated successfully as per ICH guidelines. Hence, the proposed method can be routinely used for the quantification of AC in various anti-cancer drug substances.

Controlling the surface silanol density in capillary columns and planar silicon via the self-limiting, gas-phase deposition of tris(dimethylamino)methylsilane, and quantification of surface silanols after silanization by low energy ion scattering

Surface silanols (Si-OH) play a vital role on fused silica surfaces in chromatography. Here, we used an atmospheric-pressure, gas-phase reactor to modify the inner surface of a gas chromatography, fused silica capillary column (0.53 mm ID) with a small, reactive silane (tris(dimethylamino)methylsilane, TDMAMS). The deposition of TDMAMS on planar witness samples around the capillary was confirmed with X-ray photoelectron spectroscopy (XPS), ex situ spectroscopic ellipsometry (SE), and wetting. The number of surface silanols on unmodified and TDMAMS-modified native oxide-terminated silicon were quantified by tagging with dimethylzinc (DMZ) via atomic layer deposition (ALD) and counting the resulting zinc atoms with high sensitivity-low energy ion scattering (HS-LEIS). A bare, clean native oxide – terminated silicon wafer has 3.66 OH/nm2, which agrees with density functional theory (DFT) calculations from the literature. After TDMAMS modification of native oxide-terminated silicon, the number of surface silanols decreases by a factor of ca. 10 (to 0.31 OH/nm2). Intermediate surface testing (IST) was used to characterize the surface activities of functionalized capillaries. It suggested a significant deactivation/passivation of the capillary with some surface silanols remaining; the modified capillary shows significant deactivation compared to the native/unmodified fused silica tubing. We believe that this methodology for determining the number of residual silanols on silanized fused silica will be enabling for chromatography.

Nutrient and fatty acid composition of elephant and king grasses from different altitudes

Types of forage and the altitude it grows affect the quality of milk’s fatty acids (FA) profile. Thus, this study aimed to analyze the chemical and FA quality of elephant grass (EG) and king grass (KG) growth from different altitudes. The grass samples were collected from Pangalengan District, the highland, and Dramaga District, the lowland. Grass lipid extraction and FA methylation were done according to the AOAC method. FA was quantified using gas chromatography (GC-7820A), CP-Sil 88 fused-silica capillary column, and authentic standard (Supelco 37 Component FAME-Mix). The nutrient content was analyzed using FT-NIR Spectrometer Solids Cell, except for EE used the AOAC method. This study showed EE content was significantly different between species, with the higher content found in EG. The C17:0 was significantly different between altitudes. The SFA, UFA, and PUFA were significantly different between species. The EG had higher UFA and PUFA and lower SFA. It showed that the higher EE content was related to the higher FAs yield, followed by higher UFA and PUFA in EG than in KG. It was concluded that the grass species had a more significant effect on chemical and FAs profiles than the altitude.

Preparation of open tubular capillary column covalently coated with polystyrene sulfonate with 4,4'-azobis (4-cyanopentanoyl chloride) as polymerization initiator for electrochromatographic separation of alkaloids, sulfonamides and peptides.

An open tubular capillary electrochromatography column covalently bonded with polystyrene sulphonate was prepared via in situ polymerization using functionalized azo-initiator 4,4'-Azobis(4-cyanopentanoyl chloride). Scanning electron, fluorescence and atomic force microscopy techniques showed the formation of a relatively rough layer of polymer. In addition, -CN and C = O stretching vibrations from infrared spectroscopy proved the successful immobilization of the azo-initiator through covalent bonding and X-rayPhotoelectronSpectroscopy confirmed the elemental composition of the formed polymer layer. The prepared column was found to be appropriate for small and medium-sized molecules separation. Compared to bare fused silica capillary column higher selectivity and resolution were obtained for the separation of alkaloids, sulfonamides and peptides as a result of the electrostatic and pi-pi stacking interactions between the small organic molecules and the coated column without compromising the electroosmotic flow mobility. Separation efficiency was also increased compared to the bare capillary for the separation of alkaloids (about 1.5 times). Moreover, intraday, inter day, intra batch and inter batch relative standard deviation values of retention time and peak area of peptides were within 2% and 10%, respectively, indicating a good repeatability of the column preparation procedure. The developed method for the covalent bonding of polymers through a functionalized azo-initiator could represent a promising stable method for the preparation of open tubular column. This article is protected by copyright. All rights reserved.

Platform headspace gas chromatography method for high-throughput determination of residual solvents in pharmaceutical materials

Static headspace capillary gas chromatography (HSGC) has been employed to monitor the level of residual solvents in the pharmaceutical materials. Most of the HSGC methods, however, consume significant amounts of diluents and require considerable amount of sample preparation time. Accordingly, a HSGC method featured with fast turnaround time, and minimal amount of solvent use has been developed for the quantitative analysis of 27 residual solvents frequently used in the development and manufacturing processes of pharmaceutical industry. This HSGC-FID method employs a commercially available fused silica capillary column, a split injection (40:1), and a programmed temperature ramp. It was qualified for specificity, accuracy, repeatability/precision, linearity, LOQ, solution stability, and robustness using two representative sample matrices. The standards, samples and spiked samples were demonstrated to be stable for at least 10 days at room temperature in sealed headspace vials with a recovery of ≥ 93%. The method was also shown to be robust, and its performance was not affected by small changes of carrier gas flow rate, initial oven temperature or the headspace oven temperature. In this new approach, the analytical sample was prepared by dissolving the sample into 1 mL of the diluent and the standard solution was prepared by diluting 1 mL of the custom-made stock into 9 mL of the diluent whereas the traditional approach requires liters of the diluent, making the new approach environmentally friendly, sustainable, economical, agile, error-proofing and thus appropriate for a variety of pharmaceutical applications.

Volatomics-assisted characterization of aroma and off-flavor contributors in fresh and thermally treated kiwifruit juice

The distinctive aroma profile of kiwifruit juice was significantly changed during thermal treatment, however, the theoretical basis for clarifying and controlling the changes was deficient. In this study, we applied volatomics techniques to investigate the contributors of off-flavors in thermally treated kiwifruit juice. Sixteen aroma compounds were identified to be responsible for the typical “fruity”, “grassy”, and “cucumber-like” flavors of fresh kiwifruit by two different fused silica capillary columns coupled with chromatography-olfactometry/detection frequency (GC-O/DF) analysis and calculation of odor activity value (OAV). Thirty-one odor-active compounds were determined as important contributors to the sensory profile of thermally treated kiwifruit juice, 14 of which were common to all varieties investigated. The key aroma compounds on fresh kiwifruit significantly decreased after thermal treatment, while decanal, (E)-2-decenal, methional, β-damascenone, 1-octen-3-one, DMHF, and dimethyl sulfide which presented undesirable cooked cabbage/potato, roasted fruit, and sulfurous odors, were accumulated in a large amount. By applying PLSR analysis, (E)-2-decenal, methional, β-damascenone, DMHF, and dimethyl sulfide were further verified to have great contributions to the formation of the cooked off-flavor during thermal treatment. Moreover, XX was found to be more thermal-sensitive and more prone to forming cooked off-flavors after thermal treatment. This study could provide theoretical guidance for the regulation of thermal-induced off-flavors during the manufacturing of kiwifruit juice.

Nano-liquid chromatography with monolithic stationary phase based on naphthyl monomer for proteomics analysis

Monolithic poly(2-vinylnaphthalene-co-divinylbenzene) columns were introduced, for the first time, and were evaluated as the separation media for nano-liquid chromatography (nano-LC). These columns were prepared by in-situ polymerization of 2-vinylnaphthalene (2-VNA) as the functional monomer and divinylbenzene (DVB) as the crosslinker in a fused silica capillary column of 50 µm i.d. Various porogenic solvents, including tetrahydrofuran (THF), dodecanol and toluene were used for morphology optimization. Final monolithic column (referred to as VNA column) was characterized by using scanning electron microscopy (SEM) and chromatographic analyses. Alkylbenzenes (ABs), and polyaromatic hydrocarbons (PAHs) were separated using the VNA column while the column offered excellent hydrophobic and π-π interactions under reversed-phase conditions. Theoretical plates number up to 41,200 plates/m in isocratic mode for ethylbenzene could be achieved. The potential of the final VNA column was demonstrated with a gradient elution in the separation of six intact proteins, including ribonuclease A (RNase A), cytochrome C (Cyt C), lysozyme (Lys), β-lactoglobulin (β-lac), myoglobin (My) and α-chymotrypsinogen (α-chym) in nano LC system. The column was then applied to the peptide analysis of trypsin digested cytochrome C, allowing a high peak capacity up to 1440 and the further proteomics analysis of COS-7 cell line was attempted applying the final monolithic column in nano-LC UV system.

Optimization of solid phase microextraction conditions for determination of triazines

A simple, solvent-free, and field-compatible approach to sample preparation is provided by the basic process known as solid-phase micro extraction (SPME). The aim of this study was to improve the circumstances under which triazines were extracted from aqueous matrices. The complex technique enabled the detection of the analytes in the water at a physiological level. An evaluation of the practicability of the most commercially available fiber coatings has been conducted. The porous materials (Carbowax/DVB and PDMS/DVB) extracted more efficiently than homogeneous ones (PDMS and polyacrylate). Further investigation has been focused on 65 mm PDMS/DVB fiber. Solid phase microextraction is a technique based on the partition equilibrium of analytes between the sample and the fiber. Therefore, 60 minutes were required to reach equilibrium at room temperature. The desorption efficiency at 3 temperature levels had been compared and 270 °C was retained. Experiments were performed with a Finnigan MAT GCQ Model installed with a 30-m x 0.32-mm ID, ZB-5 (0.25-mm film thickness) fused-silica capillary column, and Helium as a carrier gas (at 30 kPa), The ion trap mass spectrometer was operated in the electron ionization (EI) mode. Keywords: Fiber coating, Gaz chromatography, Mass spectrometry, Pesticides, Water matrices, Analysis.

Chemical composition of essential oil of common juniper (Juniperus communis L.) branches from Estonia

For the treatment of the urinary system and kidney diseases, common juniper (Juniperus communis L.) fruits are widely used. This raw material is included in the European Pharmacopoeia (Ph.Eur.) and is one of the most popular kinds of official medicinal plant material with diuretic and uroantiseptic activity. However, the main biomass of bushes consists of green branches, which also contain a significant amount of essential oil that can be used in pharmaceutical practice. The branches become waste during bush cutting. So, it is advisable to investigate the chemical composition of essential oil isolated from common juniper branches from different regions of Estonia to prove the possibility of using this essential oil and branches in pharmaceutical practice.
 Aim. Therefore, the aim of the research was to determine the chemical composition of essential oil from common juniper (J. communis L.) branches from Estonia.
 Materials and Methods. The branches of juniper shrubs were collected in the summer months from 27 different habitats in Estonia. The essential oil was isolated from fresh juniper branches by the modified distillation method described in the European Pharmacopoeia monograph of Juniperi pseudo-fructus. GC/MS analysis was carried out using an Agilent 5975 Series MSDMSD, Agilent7890A GC (Agilent Technologies, Inc.) with two detectors (MSMS and FID) on a fused silica capillary column (30 m x 0.25 mm) with a bonded stationary phase: poly(5 %-diphenyl-95 %-dimethyl)siloxane (DB-5). The carrier gas was helium with a split ratio of 1:30, and the flow rate of 1.3 mL/min was applied. The temperature program was from 50°–240˚C at 2˚C/min and the injector temperature was 300˚C. The MS detector was operated in the EIEI mode of 70 eV and at a scan rate of 2 scans/s with a mass acquisition range of 20–400 u.
 Research results. The average amount of juniper essential oil in branches extracted during distillation using the Ph. Eur. method was 0.23±0.04 ml. 103 substances were identified in 27 different samples of juniper branches and quantified by the GC/MS method. The dominant components of Estonian common juniper essential oil are α-pinene (37.5-69.3 %), pinene, sabinene, β-myrcene and β-phellandrene. The juniper essential oils from Estonian raw materials were compared with Serbian, Iran, Portuguese, French and Greek ones. It was established that the common juniper growing in Estonia belongs to the α-pinene chemotype.
 Conclusions. Common juniper growing in Estonia belongs to the α-pinene chemotype. 103 substances were identified, and their assay was established in 27 different samples of juniper branches. The dominant components of Estonian common juniper essential oil are α-pinene (37.5-69.3 %), so it could be used as a source of a-pinene for the pharmaceutical industry.
 As the essential oils of common juniper branches didn’t meet all the requirements of the European Pharmacopoeia for juniper berries oil, so separate regulatory documentation must be developed for the essential oil from the branches

Novel Eco-Friendly Stability Indicating Capillary Zone Electrophoresis Method for Determination of Aripiprazole in Tablet Dosage form: DoE Directed Optimization, Development and Method Validation

In this work, a novel environment-friendly stability indicating capillary zone electrophoresis (CZE) method has been developed and validated for assaying the aripiprazole (ARP) in tablet dosage form. The separation of ARP from its degradation products and internal standard was achieved using a fused silica capillary column (30.2 cm x 75 μm ID), a background electrolyte containing 6 mmol L−1 ammonium formate buffer (pH 3) with 5% methanol under a potential of 15 kV and detection at 214 nm. The stability indicating ability of the method was investigated by analyzing ARP after being subjected to acidic, alkaline, thermal, photolytic, and oxidative stress conditions, according to ICH guidelines. Design of experiments was used during forced degradation and method optimization. Oxidation was the main degradation pathway among those evaluated. The drug was separated from its oxidative degradation products in less than 4 min. CZE method was linear between 60 – 140 μg mL−1, R2 = 0.9980, precise (intra-day 0.88% and inter-day 1.30%). The average recovery was 100.93 ± 0.77%. This is the first method in the literature for quantification of ARP in the presence of its related degradation products with high separation efficiency, low operation cost and minimum solvent consumption. This method could be helpful in the routine quality control analysis in the pharmaceutical industries with least harmful effect on the environment. CZE is considered an eco-friendly alternative of conventionally HPLC methods.

Simultaneous Determination of Fenchone and Trans-Anethole in Essential Oils and Methanolic Extracts of Foeniculum vulgare Mill. Fruits Obtained from Different Geographical Regions Using GC-MS Approach

The gas chromatography–mass spectrometry (GC-MS) approach is established for the simultaneous determination of fenchone (FCO) and trans-anethole (TOH) in the essential oils and methanolic extracts of fennel (Foeniculum vulgare Mill.) fruits obtained from India (IND), Pakistan (PAK), and Saudi Arabia (SA). The simultaneous determination of FCO and TOH was performed via Agilent 190914S HP–5MS fused-silica capillary column (30 m × 250 µm ID, 0.25 µm film thickness). The proposed GC-MS approach was linear in the range of 0.10–50 µg/g for FCO and TOH. FCO’s detection (LOD) and quantification (LOQ) limits were calculated to be 0.04 and 0.12 µg/g, respectively. The LOD and LOQ values for TOH, on the other hand, were calculated to be 0.05 and 0.15 µg/g, respectively. In addition, the proposed GC-MS approach was accurate and precise for the simultaneous determination of FCO and TOH. The amount of FCO in essential oils of F. vulgare was computed as 0.021, 0.034, and 0.029 mg/g in the samples obtained from IND, PAK, and SA, respectively. The amount of TOH in the essential oils of F. vulgare was computed as 7.40, 14.8, and 10.2 mg/g in the samples obtained from IND, PAK, and SA, respectively. However, the amount of FCO in the methanolic extract of F. vulgare was estimated as 0.031, 0.021, and 0.057 mg/g in the samples obtained from IND, PAK, and SA, respectively. On the other hand, the amount of TOH in the methanolic extract of F. vulgare was estimated as 0.440, 0.498, and 1.74 mg/g in the samples obtained from IND, PAK, and SA, respectively. These findings suggested that the proposed GC-MS approach might be used to simultaneously determine the FCO and TOH in a variety of essential oils and plant extracts.

Determination of 82 polychlorinated biphenyls in biological samples using accelerated solvent extraction-isotope dilution-high resolution gas chromatography-high resolution mass spectrometry

我国水产品中多氯联苯(PCBs)的检测方法,主要以6种指示性PCBs和12种二噁英类共平面PCBs为主,仅涵盖有限的PCBs。为更全面地获得生物体中PCBs的浓度水平,深入探讨PCBs在生物体内的代谢和富集特征,进而准确评价PCBs对人类的暴露水平及风险,以鱼和贝类作为生物样品代表,建立了加速溶剂提取-同位素稀释-高分辨气相色谱-高分辨质谱(ASE-ID-HRGC-HRMS)测定生物样品中82种PCBs的方法。比较了振荡提取和加速溶剂提取两种提取方式的回收率和重复性,最终采用正己烷-二氯甲烷(1∶1, v/v)对PCBs进行加速溶剂提取。考察了各流分淋洗液对PCBs的回收率,确定了样品提取液经8 g 44%酸性硅胶层析柱(内径15 mm), 90 mL正己烷洗脱的净化方式。样品提取液净化浓缩后进行HRGC-HRMS分析,色谱柱采用DB-5MS超低流失石英毛细管柱(60 m×0.25 mm×0.25 μm)。通过优化后的升温程序对化合物进行分离,以保留时间和两个特征离子精准定性,采用同位素内标法定量。结果表明,在0.1~200 μg/L范围内,平均相对响应因子(RRF)的相对标准偏差值(RSD, n=7)均≤20%,相关系数(r2)>0.99。生物样品中PCBs的方法检出限为0.02~3 pg/g;鱼类中PCBs平均加标回收率为71.3%~141%, RSD(n=7)为2.1%~14%;贝类中PCBs平均加标回收率为76.9%~143%, RSD为1.4%~11%。该方法灵敏、准确、可靠,可以更加全面具体地分析鱼和贝类等水产品受PCBs的污染情况,为国内外开展生物监测提供有效的技术支持,从而服务于相关生态环境管理及履行《斯德哥尔摩公约》。

Hydrophobic AEROSIL®R972 Fumed Silica Nanoparticles Incorporated Monolithic Nano-Columns for Small Molecule and Protein Separation by Nano-Liquid Chromatography.

A new feature of hydrophobic fumed silica nanoparticles (HFSNPs) when they apply to the preparation of monolithic nano-columns using narrow monolithic fused silica capillary columns (e.g., 50-µm inner diameter) was presented. The monolithic nano-columns were synthesized by an in-situ polymerization using butyl methacrylate (BMA) and ethylene dimethacrylate (EDMA) at various concentrations of AEROSIL®R972, called HFSNPs. Dimethyl formamide (DMF) and water were used as the porogenic solvents. These columns (referred to as HFSNP monoliths) were successfully characterized by using scanning electron microscopy (SEM) and reversed-phase nano-LC using alkylbenzenes and polyaromatic hydrocarbons as solute probes. The reproducibility values based on run-to-run, column-to-column and batch-to-batch were found as 2.3%, 2.48% and 2.99% (n = 3), respectively. The optimized column also indicated promising hydrophobic interactions under reversed-phase conditions, while the feasibility of the column allowed high efficiency and high throughput nano-LC separations. The potential of the final HFSNP monolith in relation to intact protein separation was successfully demonstrated using six intact proteins, including ribonuclease A, cytochrome C, carbonic anhydrase isozyme II, lysozyme, myoglobin, and α-chymotrypsinogen A in nano-LC. The results showed that HFSNP-based monolithic nanocolumns are promising materials and are powerful tools for sensitive separations.

METHOD DEVELOPMENT FOR THE DETERMINATION OF METFORMIN IN HUMAN PLASMA BY CAPILLARY ZONE ELECTROPHORESIS

Background: Metformin is an oral antidiabetic drug from the biguanide class and it is the first-line drug chosen for the treatment of type 2 diabetes. This is a drug on the list of pharmaceutical substances required to report bioequivalence study data when registering the drug. Objectives: (1) To develope a capillary zone electrophoresis method for determining metformin hydrochloride in human plasma. (2) To validate the method. Materials and methods: Human plasma, metformin hydrochloride, ranitidine hydrochloride. The method was developed and validated according to US-FDA 2018 and EMA 2011. Results: The procedure was developed by using the Agilent 7100 CE electrophoresis system with ranitidine hydrochloride as an internal standard. Sample preparation was accomplished through protein precipitation with acetonitrile. The optimal electrophoresis conditions are as follows: uncoated fused-silica capillary column of a total length of 40 cm (31.5 cm effective length, inner diameter 100 μm), phosphate buffer solution 100 mM (pH = 4), the voltage applied to both capillary ends of 15 kV, the inlet end of capillary dipped in water before sample injection, sample injection mode of 50 mBar in 7 seconds, using a PDA detector at 232 nm. The analysis method was validated according to the requirements of the US-FDA 2018 and EMA 2011 with the following criteria: system suitability with RSD < 3%; good specificity; the calibration curves were linear (r2 ≥ 0.98) in the concentration range of 0.1 – 4.0 μg/ml for metformin in human plasma; the lower limit of quantification was 0.1 μg/ml; the intra-day and inter-day accuracy were 99.41 – 105.28% and 92.47 – 106.26%, respectively; the intra-day and inter-day precision were 1.99 – 4.03% and 3.11 – 6.05%, respectively; the mean recovery of ranitidine (internal standard) was 86.2%, the mean recoveries of metformin at three levels LQC, MQC, and HQC were 72.9%, 75.9%, and 77.4%, respectively; plasma samples were stable to analysis. Conclusions: The developed method meets the requirements of US-FDA 2018 and EMA 2011 to determine metformin in plasma. Key words: Capillary zone electrophoresis, plasma, metformin

Analytical method validation for related substances in sodium valproate oral solution by gas chromatography

BackgroundSodium Valproate is the sodium salt of valproic acid (VPA). Valproic acid is mainly used for the treatment of epilepsy. The specific aim of the study is to develop and validate an optimized method for the determination of six related substances such as N,N-dimethyl valpronamide, valeric acid, 2-methyl valeric acid, 2-ethyl valeric acid, 2-isopropyl valeric acid and 2-n-butyl valeric acid in Sodium Valproate Oral Solution by Gas Chromatography. Chromatographic separations of these six related substances were achieved on DB-FFAP fused silica capillary column (30 m × 0.53 mm) bonded with a 0.5-µm layer of macrogol 20,000 2-nitroterephthalate materials used as stationary phase. The six related impurities were extracted using heptane and monitored by Gas Chromatography coupled with flame ionization detector. The performance of the developed method was assessed by evaluating system suitability, method precision, specificity, linearity and range, ruggedness, accuracy, robustness.ResultsThe correlation coefficient was within the acceptance criteria in the range of 0.9998. The evaluated concentrations for Sodium Valproate were in the ranges of 5.05–25.27 ppm. The average recovery values were in the range of 92.4–100.4%. Solution Stability experiments were performed to evaluate the degradation behavior of SVS.ConclusionA novel, precise and sensitive GC method was developed, validated and optimized for the determination of six related substances in sodium Valproate oral solution. The results obtained from the validation experiments demonstrated that the method is accurate, precise, linear, specific, sensitive and robust. Hence, the proposed method can be an alternative method, for the determination of related substances in sodium valproate oral solution drug substance.

A highly sensitive, simple, and fast gas chromatography-mass spectrometry method for the quantification of serum short-chain fatty acids and their potential features in central obesity.

Short-chain fatty acids (SCFAs) are the main gut microbe metabolites, which have no more than six carbons. SCFAs are an emerging biomarker in metabolic diseases, including central obesity. Commonly, SCFAs are measured in fecal samples, where they are highly abundant, but here they do not reflect direct interactions with related organs. Serum SCFAs are assumed to be more associated with metabolic disease than fecal SCFAs, albeit at very low concentrations. The aim of the present study is to develop a highly sensitive, simple, and fast method for measuring six SCFAs in the serum by gas chromatography-mass spectrometry (GCMS). The serum is mixed with meta-phosphoric acid and 2,2-dimethylbutyric acid, followed by homogenization and centrifugation. Supernatant is then injected into the fused silica capillary column. The method is linear from 0.12-500μmol/L for all SCFAs with an accuracy of 90-117%. The total coefficient of variation for precision ranges from 3.8 to 14.1%. A preliminary study is performed with 32 centrally obese subjects and 17 lean subjects. The mean values of all SCFAs, including acetic, propionic, isobutyric, butyric, isovaleric, and valeric acid, in the centrally obese subjects are significantly higher compared with lean subjects. A significant correlation also exists between all SCFAs, with the waist circumference indicating that serum SCFAs have potential features with respect to metabolic diseases, especially central obesity. The validated GCMS method provides highly sensitive, fast, simple, and reliable SCFA quantitation in the serum and demonstrates the potential features of circulating SCFAs in central obesity.

Nano-liquid chromatography with a new nano-structured monolithic nanocolumn for proteomics analysis.

Herein, we report the preparation and application of a new nano-structured monolithic nanocolumn based on modified graphene oxide using narrow fused silica capillary column (e.g., 50 μm internal diameter). The nanocolumn was prepared by an in situ polymerization using butyl methacrylate, ethylene dimethacrylate, and methacryloyl graphene oxide nanoparticles. Dimethyl formamide and water were used as the porogenic solvent. After polymerization, the obtained nanocolumn was coated with dimethyloctadecylchlorosilane in order to enhance the hydrophobicity. Both isocratic and gradient nano-liquid chromatographic separations for small molecules (e.g., alkylbenzenes) and macromolecules (e.g., intact proteins) were performed. Theoretical plates number up to 3600 plates/m in isocratic mode for propylbenzene were achieved. It was demonstrated that the feasibility of graphene oxide modified monolithic nanocolumn for high-efficiency and high-throughput nanoscale proteomics analysis. The high resolving power of monolithic nanocolumn yielded sensitive protein separation with narrower peak width while a high-resolution analysis of peptides from trypsin-digested cytochrome C could be obtained. Graphene oxide based monolithic nanocolumns are promising and can allow to powerful tools for trace proteom sample analysis.

Quantitative Phytochemical Screening and GC-MS Analysis of the Ethanolic Extract of </i>Tabebuia roseo-alba</i> (Ridl) Sand

Medicinal plants have been used in folkloric medicine to treat various ailments. The compound investigations of medicinal plants have largely been driven to discover new drugs to treat human diseases. The study was designed to estimate the amount of phytochemical constituents and also to explore the presence of bioactive compounds in ethanolic extract of Tabebuia roseo-alba using Gas Chromatography-Mass Spectrometry (GC-MS). Quantitative phytochemical analysis was carried out by standard procedures. GC-MS analysis of the plant extracts was performed by using GC SHIMADZU QP2010 system and Gas Chromatograph interfaced to a Mass Spectrometer (GC-MS) equipped with RXi -1ms fused silica capillary column. The total phenol content was found to be 112.67+0.03 in ethanolic extract of Tabebuia roseo-alba leaves. The GC-MS analysis revealed the presence of eight major peaks from which various bioactive compounds were ascertained. In conclusion, ethanolic extract of Tabebuia roseo-alba possess many bioactive constituents which may be accountable for its various pharmacological activities.