In this work, an on-line SPE-HPLC method with spectrophotometric detection was developed for the determination of coumarins in complex samples. For the on-line cleanup of samples, a molecularly imprinted polymer was packed into the column cartridge and coupled directly with HPLC (MISPE-HPLC) using a column switching system. The separation of coumarins was performed on a C18 core-shell column (100×4.6mm, 5μm) with a mobile phase consisting of 0.3% acetic acid/acetonitrile with gradient elution at a flow-rate of 1mLmin-1. The total time of the whole analytical run, including the extraction step, was 13.25min. The on-line MISPE-HPLC method was optimized and validated. The results showed good linearity (0.10-100μgmL-1) with correlation coefficients higher than 0.99. The LOD values were from 0.03 to 0.15μgmL-1. The proposed method was successfully applied for analysis of real samples (Cassia cinnamon, chamomile tea, and Tokaj specialty wines) and obtained recoveries varied from 78.7% to 112.2% with an RSD less than 9%.

• Klíčová slova
• Chromatography, Column switching system, Coumarins, Molecularly imprinted polymers, On-line solid phase extraction,
• MeSH
• extrakce na pevné fázi * MeSH
• kumariny MeSH
• molekulový imprinting MeSH
• on-line systémy MeSH
• polymery MeSH
• vysokoúčinná kapalinová chromatografie MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• kumariny MeSH
• polymery MeSH

Reaching trace amounts of mycotoxin contamination requires sensitive and selective analytical tools for their determination. Improving the selectivity of sample pretreatment steps covering new and modern extraction techniques is one way to achieve it. Molecularly imprinted polymers as selective sorbent for extraction undoubtedly meet these criteria. The presented work is focused on the hyphenation of on-line molecularly imprinted solid-phase extraction with a chromatography system using a column-switching approach. Making a critical comparison with a simultaneously developed off-line extraction procedure, evaluation of pros and cons of each method, and determining the reliability of both methods on a real sample analysis were carried out. Both high-performance liquid chromatography methods, using off-line extraction on molecularly imprinted polymer and an on-line column-switching approach, were validated, and the validation results were compared against each other. Although automation leads to significant time savings, fewer human errors, and required no handling of toxic solvents, it reached worse detection limits (15 versus 6 μg/L), worse recovery values (68.3-123.5 versus 81.2-109.9%), and worse efficiency throughout the entire clean-up process in comparison with the off-line extraction method. The difficulties encountered, the compromises made during the optimization of on-line coupling and their critical evaluation are presented in detail.

• Klíčová slova
• column-switching chromatography, molecularly imprinted polymers, mycotoxin, on-line solid-phase extraction, patulin,
• MeSH
• extrakce na pevné fázi * MeSH
• molekulový imprinting * MeSH
• patulin izolace a purifikace   MeSH
• polymery MeSH
• reprodukovatelnost výsledků MeSH
• vysokoúčinná kapalinová chromatografie MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• patulin MeSH
• polymery MeSH

Polymers in nanofiber format promise a great potential as sorbents for extraction techniques. This tutorial provides an overview of direct coupling of extraction techniques based on nanofibers to liquid chromatography. Arrangements of the fibers in conventional extraction cartridges are demonstrated. Selection of suitable nanomaterials according to their surface density, wettability, and mechanical stability is proposed and personal experience of the authors commented. Optimization of on-line extraction procedure, practical aspects, technical problems, pitfalls, pros, and cons of using nanofibers for extraction in high-pressure chromatography systems are also discussed and several examples presented. The following text comprehensively summarizes numerous reports that dealt with the topic. Future perspectives of advanced nanofiber materials and approaches that concern polymer fibers modifications are also included.

• Klíčová slova
• Chromatography, Column switching, Electrospinning, Nanofibers, On-line solid phase extraction, Polymers,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Effective process, including a cartridge packing polypropylene fiber sorbent modified by following on-line polydopamine coating, for on-line solid phase extraction in 2D UHPLC system has been developed. Hydrophobic surface of mechanically stable polypropylene fibers was hydrophilized using an automated and reproducible in situ coating process to enable good wettability and effective extraction of polar compounds. Polymerization mixture consisting dopamine and TRIS buffer was circulated through the cartridge containing polypropylene fibers using a peristaltic pump to achieve polymerization. This process was optimized in terms of dopamine amount in the polymerization mixture, its flow rate, and polymerization time. Best results were obtained with 25 mL polymerization mixture containing 20 mg dopamine circulated through the cartridge at a flow rate of 2.07 mL min-1 for 60 min. Prepared cartridges were evaluated via measurement of the recovery and reproducibility using chlorogenic acid as a model compound. Overall reproducibility of our multistep process including eight cartridges in 2D UHPLC system, each measured in triplicate, was 3.61% (n = 24).

• Klíčová slova
• 2D UHPLC, Chlorogenic acid, Fibrous sorbent, On-line coating, On-line solid phase extraction, Sorbent modification,
• Publikační typ
• časopisecké články MeSH

A novel application of nanofiber polymers in the wide area of a sample preparation techniques known as solid phase extraction has been studied. We demonstrated application of nanofibers as sorbents for use in a system including on-line extraction coupled with column-switching high performance liquid chromatography. Four types of nanofibers including polyamide 6 with two different surface densities, poly(ε-caprolactone), and polystyrene were tested. We found that three of them were very efficient extraction sorbents sufficiently stable for application in the on-line system. Our results confirmed that the extraction efficiency of the nanofibers depended on the type and chemistry of the spun polymer as well as on the fabrication process of the nanofibrous mats that affected their density, structure, surface density, and mechanical functionality. We also compared performance of all four nanofibers with a conventional monolithic reversed-phase C18 sorbent in terms of extraction efficiency using on-line solid-phase extraction-HPLC system. Polyamide 6 was found to be the best sorbent for lipophilic analytes with a retention and extraction efficiency for the target analytes comparable with that of the C18 monolith.

• Klíčová slova
• Chromatography, Extraction, Nanofiber polymers, On-line SPE, On-line coupling,
• Publikační typ
• časopisecké články MeSH

The presented work describes the development of a simple, fast and effective on-line SPE-UHPLC-UV/vis method using fused core particle columns for extraction, separation and quantitative analysis of the nine illegal dyes, most frequently found in chilli-containing spices. The red dyes Sudan I-IV, Sudan Red 7B, Sudan Red G, Sudan Orange G, Para Red, and Methyl Red were separated and analyzed in less than 9 min without labor-consuming pretreatment procedure. The chromatographic separation was performed on Ascentis Express RP-Amide column with gradient elution using mixture of acetonitrile and water, as a mobile phase at a flow rate of 1.0 mL min(-1) and 55°C of temperature. As SPE sorbent for cleanup and pre-concentration of illegal dyes short guard fused core column Ascentis Express F5 was used. The applicability of proposed method was proven for three different chilli-containing commercial samples. Recoveries for all compounds were between 90% and 108% and relative standard deviation ranged from 1% to 4% for within- and from 2% to 6% for between-day. Limits of detection showed lower values than required by European Union regulations and were in the range of 3.3-10.3 µg L(-1) for standard solutions, 5.6-235.6 µg kg(-1) for chilli-containing spices.

• Klíčová slova
• Chilli-containing samples, Column switching, Fused core column, Illegal red Sudan dyes, On-line solid phase extraction, UHPLC,
• MeSH
• analýza potravin metody   MeSH
• azosloučeniny chemie   MeSH
• barvicí látky chemie   izolace a purifikace   MeSH
• Capsicum chemie   MeSH
• extrakce na pevné fázi metody   MeSH
• indikátory a reagencie chemie   MeSH
• koření analýza   MeSH
• naftoly chemie   MeSH
• on-line systémy MeSH
• potravinářská barviva chemie   MeSH
• vysokoúčinná kapalinová chromatografie metody   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• azosloučeniny MeSH
• barvicí látky MeSH
• fat red 7B MeSH Prohlížeč
• indikátory a reagencie MeSH
• methyl red MeSH Prohlížeč
• naftoly MeSH
• Orange G MeSH Prohlížeč
• para red MeSH Prohlížeč
• potravinářská barviva MeSH
• Scarlet Red MeSH Prohlížeč
• sudan red MeSH Prohlížeč

Polyamide 6 nanofiber polymers were used as modern sorbents for on-line solid phase extraction (SPE) coupled with liquid chromatography. The on-line SPE system was tested for the determination of bisphenol A in river water samples. Polyamide nanofibers were prepared using needleless electrospinning, inserted into a mini-column cartridge (5 × 4.6mm) and coupled with HPLC. The effect of column packing and the amount of polyamide 6 on extraction efficiency was tested and the packing process was optimized. The proposed method was performed using a 50-µL sample injection followed by an on-line nanofibrous extraction procedure. The influence of the washing mobile phase on the retention of bisphenol A during the extraction procedure was evaluated. Ascentis® Express C18 (10cm × 4.6mm) core-shell column was used as an analytical column. Fluorescence detection wavelengths (λex = 225nm and λem = 320nm) were used for identification and quantification of Bisphenol A in river waters. The linearity was tested in the range from 2 to 500µgL-1 (using nine calibration points). The limits of detection and quantification were 0.6 and 2µgL-1, respectively. The developed method was successfully used for the determination of bisphenol A in various samples of river waters in the Czech Republic (The Ohře, Labe, Nisa, Úpa, and Opava Rivers).

• Klíčová slova
• Bisphenol A, Fluorimetry, Nanofiber polymers, Nanofibrous extraction, On-line SPE, UHPLC,
• Publikační typ
• časopisecké články MeSH

Three different approaches has been used to obtain nano/micro fibers and their diversity and extraction properties were examined. The effect of their structure on stability in an ultra-high-performance liquid chromatography (UHPLC) system during on-line SPE procedure was monitored. Five types of various nano/micro fiber polymers were used as sorbents: polyamide 6 nanofibers, polyvinylidene difluoride nanofibers, polyethylene microfibers, and two new polycaprolactone microfiber/nanofiber and polycaprolactone microfibers/polyvinylidene difluoride nanofibers composite polymers. The fiber polymers were filled in a cartridge directly connected to the UHPLC system and tested. For each polymer, the optimal conditions of the on-line extraction were found and potential applicability on real samples was tested. The determination of ochratoxin A (OTA) in beer matrix was chosen as a case study. Relevant factors such as the mechanical and chemical stability of the nano/microfibers, filling the cartridges, fiber reusability and the possibility and the repeatability of all processes were involved in the proposed study. A new nano/micro composite sorbent consisting of polycaprolactone microfibers/polyvinylidene difluoride nanofibers was chosen as the most suitable sorbent for the on-line extraction of OTA from a beer matrix. The tested validation parameters had the value of intra-day precision lower than 1.48%, linearity in the range from 0.5 to 100 μg L-1 with r2 ≥ 0.9999 for standard and matrix calibration curve, and recovery in the range 99.1-103.9% at five concentration levels. Long-term precision evaluated for 31 analyses over the period of three months did not exceed 2.9% RSD. It confirmed the column reusability and perfect stability of nano/micro composite sorbent in the presence of organic solvents and after repeated injection of a complex beer matrix.

• Klíčová slova
• Ochratoxin A, On-line extraction, Polyamide 6, Polycaprolactone, Polyethylene nanofibers, Polyvinylidene difluoride,
• MeSH
• adsorpce MeSH
• extrakce na pevné fázi * MeSH
• nanostruktury chemie   MeSH
• ochratoxiny analýza   MeSH
• pivo analýza   MeSH
• polymery chemie   MeSH
• vysokoúčinná kapalinová chromatografie MeSH
• Publikační typ
• časopisecké články MeSH
• srovnávací studie MeSH
• Názvy látek
• ochratoxin A MeSH Prohlížeč
• ochratoxiny MeSH
• polymery MeSH

A new selective molecularly imprinted polymer has been prepared and used for extraction in on-line SPE-HPLC to achieve the selective determination of citrinin. Four different imprinted polymers varying in combinations of components were prepared by bulk polymerization and evaluated in terms of binding capacity and selectivity. Imprinted polymer prepared from a mixture comprising 1-hydoxy-2-naphtoic acid as the template molecule, acrylamide as the structural monomer, ethylene dimethacrylate as the cross-linker (in a molar ratio of 1:4:16), and acetonitrile as the porogenic solvent exhibited the best properties. The selectivity of this sorbent was confirmed by comparison with the non-imprinted counterpart prepared using the same polymerization carried out in the absence of template. Imprinted polymer was packed in a 20 × 3 mm i.d. steel cartridge and coupled to the on-line SPE-HPLC system through a six-port switching valve. The method for determination of citrinin including the on-line extraction step was then developed and validated. The sample in the form of methanolic extract was loaded, cleaned, and preconcentrated in the imprinted SPE cartridge. Subsequent separation of citrinin from residual interferences was achieved using the analytical column Kinetex Biphenyl 100 × 4.6 mm i.d., 5 μm particle size, and fluorescence detection (Ex 335, Em 500 nm). The total analysis time was only 9.50 min. Our fully validated method was also applied to analysis of food supplements based on red yeast rice extracts, the control of which is implemented in European legislation. Only minor yet acceptable contamination was found in tested samples.

• Klíčová slova
• Citrinin, Liquid chromatography, Molecularly imprinted polymer, Mycotoxin, On-line solid-phase extraction, Red yeast rice extracts,
• Publikační typ
• časopisecké články MeSH

New polyamide (PA) homopolymers and copolymers nanofibers with different alkyl chain lengths as novel materials have been investigated for the automation of on-line sample preparation step and extraction of polycyclic aromatic hydrocarbons (PAHs) from the environment. PA 4/6 nanofiber copolymer showed the highest extraction yield of tested analytes and comparable performance with commercial reversed phase C18 sorbent. Our study presents an automation of on-line solid phase extraction method coupled with ultra-high performance liquid chromatography with fluorescence detection for the analysis of nine PAHs in river water. The optimal conditions included 50 μL injection volume, washing with 10 % acetonitrile at a flow rate of 1.0 mL min-1 for 1 min, followed by backflush elution of analytes using a gradient of acetonitrile (from 60 % to 74 %) in water at 1.5 mL min-1 over 12.25 min on a YMC-Triart PFP column (150 × 4.6 mm, 3 μm particle size). The total analysis time, including extraction, separation, and column equilibration, was 14 min. This method provides excellent analytical performance, with linearity ranging from 0.01 to 0.5 μg L-1 for acenaphthene, anthracene, pyrene, chrysene, and 0.05-0.3 μg L-1 for benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(a,h)anthracene, indeno(c,d)pyrene and benzo(g,h,i)perylene, with coefficients of determination (R2) ranging 0.9989-0.9999. The limits of detection and quantification were 0.003-0.01 and 0.01-0.05 μg L-1, respectively. The recoveries were between 92 and 105 %, with RSD 1.53-6.66 %. The polyamide-based sorbent requires no modification and can be inexpensively prepared as homogeneous mats by electrospinning. It can be cut and manually packed into a column or filtration device, allowing for easy replacement, when needed, with inter-columns repeatability of RSD <13 %. In addition, a single extraction column can be reused repeatedly.

• Klíčová slova
• Automation, Copolymers, Liquid chromatography, On-line solid phase extraction, Polyamide homopolymers, Polycyclic aromatic hydrocarbons,
• Publikační typ
• časopisecké články MeSH