monolithic column
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Para Red (PR) and Sudan dyes have been illegally used as colorants to adulterate certain foods by enhancing their red/orange colour. In addition, they are toxic and carcinogenic. This work presents the development of a simple flow injection chromatographic method combined with chemometric tools to perform the determination of PR, Sudan I (SI) and Sudan II (SII) in food samples. The flow chromatographic system consisted of a low-pressure manifold coupled to a reverse phase monolithic column. A Partial Least Square (PLS) model was applied to resolve overlapped absorption spectra registered for each dye at the corresponding retention time. The relative errors of calibration (RMSECV, %) were 0.49, 0.85 and 0.23, and the relative errors of prediction (RMSEP, %) were 1.12, 0.75 and 0.33 for PR, SI and SII, respectively. The residual predictive deviation (RPD) values obtained were higher than 3.00 for all analytes. The method was successfully applied to quantify the dyes in six different commercial spices samples. The results were compared with the HPLC reference method concluding that there were no significant differences at the studied confidence level (α = 0.05). The proposed method can be used to rapidly determine the analytes in a simple, reliable, low-cost and environmentally-friendly manner.Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-021-05299-8.
- Publikační typ
- časopisecké články MeSH
The morphology, composition, and selectivity of a silica-based monolithic stationary phase, grafted by a layer of trioctyl(3/4-vinylbenzyl)phosphonium chloride ([P888VBn]Cl), is presented. The results of elemental analysis confirmed that the prepared stationary phase contains 38.8 at.% of silicon, 60.2 at.% of carbon, and 1.0 at.% of phosphorus. Capillary columns (150 × 0.1 mm) for liquid chromatography were evaluated using alkylbenzenes, monosubstituted benzenes, polyaromatic compounds, substituted benzene regioisomers, and aromatic carboxylic and amino acids. The prepared ionic liquid (IL)-based stationary phase exhibits hydrophobic, hydrophilic, and electrostatic interactions, as confirmed by experiments on the evaluation of the effect of the mobile phase composition (content of acetonitrile and ammonium formate) on the isocratic chromatographic separation. Thus, the IL-based capillary column demonstrates a unique separation selectivity compared to Phenyl-, C8-, and C18-stationary phases, and high efficiency for an expanding number of structurally diverse compounds.
A device with four parallel channels was designed and manufactured by 3D printing in titanium. A simple experimental setup allowed splitting of the mobile phase in four parallel streams, such that a single sample could be analysed four times simultaneously. The four capillary channels were filled with a monolithic stationary phase, prepared using a zwitterionic functional monomer in combination with various dimethacrylate cross-linkers. The resulting stationary phases were applicable in both reversed-phase and hydrophilic-interaction retention mechanisms. The mobile-phase composition was optimized by means of a window diagram so as to obtain the highest possible resolution of dopamine precursors and metabolites on all columns. Miniaturized electrochemical detectors with carbon fibres as working electrodes and silver micro-wires as reference electrodes were integrated in the device at the end of each column. Experimental separations were successfully compared with those predicted by a three-parameter retention model. Finally, dopamine was determined in human urine to further confirm applicability of the developed device.
Current organic polymer-based monoliths emerged some 30 years ago. Their well-known advantages include ease of the preparation, robustness, high permeability to flow, mass transport viaconvection, and a vast variety of chemistries. The early polymer-based monoliths were used almost entirely for the rapid separations of proteins and other large molecules using liquid chromatography. Anumber of new chemistries and functionalization meth-ods were meanwhile developed to produce monolithic columns for the separations in various chromatographic modes including gas chromatography, electrochromatog-raphy, and microfluidics. In addition to the typical chro-matographic separations, several new applications were recently reported thus confirming versatility of the mono-liths. For example, monoliths are excellent materials for sample preparation prior to chromatography. Their func-tionalization viaattachment of gold nanoparticles to pore surface thiols provides materials for highly sensitive sur-face enhanced Raman spectroscopy. Thin monolithic lay-ers are gaining more attention as well since they enable efficient separations of proteins using very simple means followed by an easy detection using mass spectrometry. This review is a showcase demonstrating just a few exam-ples of the substantial variety of applications of monoliths that were developed since their introduction.
Runtime is one of the essential parameters that are taken into account during development of analytical methods. Very sensitive and selective techniques based on chromatographic separation coupled with mass spectrometric detection are often utilized to meet heavy demands on the analysis of various samples. The separation time is critical during analysis of large numbers of samples or on the second column of two-dimensional chromatography. There are various approaches allowing for effective and rapid separation. These include applications of stationary phases based on fully porous particles with sub- 2 μm diameter, superficially porous particles or monolithic stationary phases. Compared to today's conventional fully porous particles (3 μm diameter and greater), higher efficiency is achieved, even at faster mobile phase flows. However, certain limitations, e.g. high working pressure (especially for sorbents with particles below 2 μm) might come into play. Furthermore, high separation efficiency provides narrow chromatographic zones, which is certainly desirable for distinguishing substances but may complicate their detection. Slow scan speed of a detector can be an issue. Ultra-high performance liquid chromatography, which is a well-established technique in analytical laboratories, is more and more often compared with previously uncommon ultra-high performance supercritical fluid chromatography. Both approaches achieve short separation times. This article presents examples of applications and mutual comparison of the mentioned techniques. Rapid chromatographic separations have become a common tool in research and control laboratories. It should be mentioned that the total duration of analysis, i.e., from sample preparation to separation and detection, followed by data interpretation, should be also considered.
- MeSH
- chromatografie kapalinová metody MeSH
- extrakce na pevné fázi MeSH
- farmakokinetika MeSH
- hmotnostní spektrometrie metody MeSH
- kontaminace léku MeSH
- kontaminace potravin analýza MeSH
- superkritická fluidní chromatografie * metody MeSH
- vysokoúčinná kapalinová chromatografie * metody MeSH
- Publikační typ
- práce podpořená grantem MeSH
An automatic flow-based system as a front end to liquid chromatography (LC) for on-line dynamic leaching of microplastic materials (polyethylene of medium density and poly(vinyl chloride)) with incurred phthalates and bisphenol A is herein presented. The microplastic particles were packed in a metal column holder, through which seawater was pumped continuously by resorting to advanced flow methodology. Each milliliter of the leachable (bioaccessible) fraction of chemical additives was preconcentrated on-line using a 10 mm-long octadecyl monolithic silica column placed in the sampling loop of the injection valve of a HPLC system that served concomitantly for analyte uptake and removal of the seawater matrix. After loading of the leachate fraction, the LC valve was switched to the inject position and the analytes were eluted and separated by a monolithic column (Onyx C18HD 100 × 4.6 mm) using an optimized acetonitrile/water gradient with UV detection at 240 nm. The automatic flow method including dynamic flow-through extraction, on-line sorptive preconcentration, and matrix clean-up was synchronized with the HPLC separation, which lasted ca. 9 min. The only two currently available multi-component certified reference materials (CRM) of microplastics (CRM-PE002 and CRM-PVC001) were used for method development and validation. Out of the eight regulated phthalates contained in the two CRMs, only the 2 most polar species, namely, dimethyl phthalate and diethyl phthalate as well as bisphenol A, were leached significantly by the seawater in less than 2 h, with bioaccessibility percentages of 51-100%. The leaching profiles were monitored and modeled with a first-order kinetic equation so as to determine the rate constants for desorption in a risk assessment scenario. Intermediate precision values of bioaccessibility data for three batches of CRMs were for the suite of targeted compounds ≤22%. This work for the first time reports a fully automatic flow method with infinite sink capacity (i.e., using a surplus of extracting solution) for the target species able to mimic the leaching of additives from plastic debris across the water body in marine settings under worst-case extraction conditions.
Since its inception, sequential injection chromatography (SIC) has evolved through several stages. Key moments including introduction of the novel technique combining sequential injection analysis and monolithic column, the first generation of commercial SIC system employing robust pump, the utilization of columns packed with fused-core particles, the on-line hyphenation of extraction and separation steps in SIC, are now followed by the second generation of commercial SIC system employing stainless steel syringe pump and parts optimized for chromatographic separation. The key developments always mean acceleration of the evolution by opening new avenues and reduction of compromises in automated analytical methods based on the flow analysis. The updates, new features, and prospects of the novel instrument are described and discussed on perspective of the method developed for extraction and separation of selected phenolic acids (gallic, protocatechuic, caffeic, p-coumaric and ferulic). The method hyphenates miniaturized on-line solid phase extraction using strong anion exchange sorbent in commercial cartridge for HPLC (20 × 1 mm) and liquid chromatography using chromatographic column (C18 50 × 4.6 mm, 5 μm particles) packed with fused-core particles in the SIC manifold. The separation in gradient mode used acetonitrile: aqueous formic acid pH 2.0 mobile phase and spectrophotometric detection at 270, 300, and 320 nm. Injected sample volumes were 200 and 500 μL. The performance of the extraction step was characterized by the recovery 94.0-107.8%, enrichment factors about 20 or 50, and the separation by peak capacities 13-34, peak symmetries 1.17-1.64, and resolutions 0.82-3.75). While using a sample volume of 200 μL, our method was characterized by the following validation parameters: LODs of 0.0075-0.03 mg L-1, LOQs of 0.025-0.10 mg L-1, calibration ranges 0.025-2.50 mg L-1 (r > 0.999), repeatability of signal at 0.50 mg L-1of RSD ≤ 1.46% (n = 6), and overall time of analysis 7.1 min. The results including pilot analysis of white and red wines demonstrated the capability of novel SIC instrument to enable fast, selective, and sensitive analysis.
- Publikační typ
- časopisecké články MeSH
Food analysis demands fast methods for routine control and high throughput of samples. Chromatographic separation enables simultaneous determination of numerous compounds in complex matrices, several approaches increasing separation efficiency and speed of analysis were involved. In this work, modern types of column with monolithic rod or superficially porous particles were employed and compared for determination of eight synthetic food dyes, their chromatographic performance was evaluated. During method optimization, cyano stationary phase Chromolith Performance CN 100 × 4.6 mm and Ascentis Express ES-CN 100 × 4.6 mm, 5 µm were selected for the separation of polar colorants. The separation was performed by gradient elution of acetonitrile/methanol and 2% water solution of ammonium acetate at flow rate 2.0 mL min-1. Mobile phase composition and the gradients were optimized in order to enable efficient separation on both columns. The method using fused-core particle column provided higher separation efficiency, narrow peaks of analytes resulted in increased peak capacity and shortening of analysis time. After the validation, the method was applied for analysis of coloured beers, soft drinks and candies.
A methodology for preparing phosphonium-based ionic liquid modified silica-based monolithic capillary columns is presented. The silica monolithic columns with dimensions of 150 × 0.1 mm were modified by a phosphonium-based ionic liquid (trioctyl(3/4-vinylbenzyl)phosphonium chloride) via 3-(trimethoxysilyl)propyl methacrylate. The prepared columns were evaluated under hydrophilic interaction liquid chromatography separation conditions, employing a sample mixture containing purine and pyrimidine bases and nucleosides. Detection was made by UV. The high efficiency of the original silica monolith was preserved even after modification, and it reached values in the range of 98,000-174,000 theoretical plates/m. The effects of the concentration of acetonitrile in the mobile phase, the presence of additives in the mobile phase, such as, acetic acid or ammonium acetate, and the pH of the mobile phase on the separation of some selected analytes were investigated. The prepared columns showed different separation selectivity compared to silica, phenyl and sulfobetaine stationary phases.
- MeSH
- betain analogy a deriváty chemie MeSH
- chromatografie kapalinová metody MeSH
- hydrofobní a hydrofilní interakce MeSH
- iontové kapaliny chemická syntéza chemie MeSH
- nukleosidy analýza MeSH
- organofosforové sloučeniny chemie MeSH
- oxid křemičitý chemie MeSH
- poréznost MeSH
- reprodukovatelnost výsledků MeSH
- Publikační typ
- časopisecké články MeSH
