Electrochemical (EC) detection techniques in flow-based analytical systems such as flow injection analysis (FIA), capillary electrophoresis (CE), and liquid chromatography (LC) have attracted continuous interest over the last three decades, leading to significant advances in EC detection of a wide range of analytes in the liquid phase. In this context, the unique advantages of pulsed amperometric detection (PAD) in terms of high sensitivity and selectivity, and electrode cleaning through the application of pulsed potential for noble metal electrodes (e.g. Au, Pt), have established PAD as an important detection technique for a variety of electrochemically active compounds. PAD is especially valuable for analytes not detectable by ultraviolet (UV) photometric detection, such as organic aliphatic compounds and carbohydrates, especially when used with miniaturised capillary and chip-based separation methods. These applications have been accomplished through advances in PAD potential waveform design, as well as through the incorporation of nanomaterials (NMs) employed as microelectrodes in PAD. PAD allows on-line pulsed potential cleaning and coupling with capillary or standard separation techniques. The NMs are largely employed in microelectrodes to speed up mass and electron transfer between electrode surfaces and to perform as reactants in EC analysis. These advances in PAD have improved the sensitive and selective EC detection of analytes, especially in biological samples with complex sample matrices, and detection of electro-inactive compounds such as aliphatic organic compounds (i.e., formic acid, acetic acid, maleic acids, and β-cyclodextrin complexes). This review addresses the fundamentals of PAD, the role of pulsed sequences in AD, the utilisation of different EC detectors for PAD, technological advancements in PAD waveforms, utilisation of microelectrodes in PAD techniques, advances in the use of NMs in PAD, the applications of PAD, and prospects for EC detection, with emphasis on PAD in flow-based systems.

• Klíčová slova
• Electrochemical detector, Flow-based analytical systems, Pulsed amperometric detection,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

A fully automated spectrophotometric method based on flow-batch analysis has been developed for the determination of clenbuterol including an on-line solid phase extraction using a molecularly imprinted polymer (MIP) as the sorbent. The molecularly imprinted solid phase extraction (MISPE) procedure allowed analyte extraction from complex matrices at low concentration levels and with high selectivity towards the analyte. The MISPE procedure was performed using a commercial MIP cartridge that was introduced into a guard column holder and integrated in the analyzer system. Optimized parameters included the volume of the sample, the type and volume of the conditioning and washing solutions, and the type and volume of the eluent. Quantification of clenbuterol was carried out by spectrophotometry after in-system post-elution analyte derivatization based on azo-coupling using N- (1-Naphthyl) ethylenediamine as the coupling agent to yield a red-colored compound with maximum absorbance at 500nm. Both the chromogenic reaction and spectrophotometric detection were performed in a lab-made flow-batch mixing chamber that replaced the cuvette holder of the spectrophotometer. The calibration curve was linear in the 0.075-0.500mgL-1 range with a correlation coefficient of 0.998. The precision of the proposed method was evaluated in terms of the relative standard deviation obtaining 1.1% and 3.0% for intra-day precision and inter-day precision, respectively. The detection limit was 0.021mgL-1 and the sample throughput for the entire process was 3.4h-1. The proposed method was applied for the determination of CLB in human urine and milk substitute samples obtaining recoveries values within a range of 94.0-100.0%.

• Klíčová slova
• Clenbuterol, Diazotization-coupling reaction, Flow-batch analysis, Molecularly imprinted polymer, Solid phase extraction,
• MeSH
• analýza moči metody   MeSH
• barva MeSH
• klenbuterol analýza   izolace a purifikace   moč   MeSH
• kolorimetrie MeSH
• lidé MeSH
• limita detekce MeSH
• metody pro přípravu analytických vzorků MeSH
• molekulový imprinting * MeSH
• náhražky mléka chemie   MeSH
• polymery klasifikace   MeSH
• rozpouštědla chemie   MeSH
• teplota MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• klenbuterol MeSH
• polymery MeSH
• rozpouštědla MeSH

There has recently been an extensive amount of work regarding the development of optical, electrical, and mechanical (bio)sensors employing planar arrays of surface-bound nanoparticles. The sensor output for these systems is dependent on the rate at which analyte is transported to, and interacts with, each nanoparticle in the array. There has so far been little discussion on the relationship between the design parameters of an array and the interplay of convection, diffusion, and reaction. Moreover, current methods providing such information require extensive computational simulation. Here we demonstrate that the rate of analyte transport to a nanoparticle array can be quantified analytically. We show that such rates are bound by both the rate to a single NP and that to a planar surface (having equivalent size as the array), with the specific rate determined by the fill fraction: the ratio between the total surface area used for biomolecular capture with respect to the entire sensing area. We characterize analyte transport to arrays with respect to changes in numerous parameters relevant to experiment, including variation of the nanoparticle shape and size, packing density, flow conditions, and analyte diffusivity. We also explore how analyte capture is dependent on the kinetic parameters related to an affinity-based biosensor, and furthermore, we classify the conditions under which the array might be diffusion- or reaction-limited. The results obtained herein are applicable toward the design and optimization of all (bio)sensors based on nanoparticle arrays.

• MeSH
• algoritmy MeSH
• biosenzitivní techniky přístrojové vybavení   MeSH
• design vybavení MeSH
• difuze MeSH
• kinetika MeSH
• mikročipová analýza přístrojové vybavení   MeSH
• mikrofluidní analytické techniky přístrojové vybavení   MeSH
• nanočástice chemie   MeSH
• počítačová simulace MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

A concept based on the Peroxidase-chip (P-chip), antibody co-immobilization, competitive and enzyme-channeling principle was exploited to develop an integrated flow-through amperometric biosensor for detection of environmental pollutants such as s-triazine herbicides. In this concept, recombinant peroxidase is immobilized on the gold electrode (P-chip) in such a way that direct electron transfer is achieved. The recognition and quantitation the target analyte is realized through the competition between the simazine-glucose oxidase (GOD) conjugate and free simazine for the binding sites of the monoclonal antibody co-immobilized with peroxidase on the gold electrode. The arrangement allows to generate a specific signal in the presence of glucose through the channeling of H2O2 produced by GOD conjugate bound to the antibody. The immunosensor exhibited 50% signal decrease (IC50 value) at approximately 0.02 microg l(-1). A concentration of 0.1 ng l(-1) gave a signal clearly distinguishable from the blank whereas the ELISA using the same antibody had a typical detection limit of about 1 microg l(-1), which is four orders of magnitude higher compared to the presented biosensor system. The results demonstrated that gene engineering biomolecules, in this case recombinant peroxidase, might be attractive reagents for the development of electrochemical immunosensors.

• MeSH
• analýza selhání vybavení MeSH
• biosenzitivní techniky přístrojové vybavení   metody   MeSH
• čipová analýza proteinů přístrojové vybavení   metody   MeSH
• design vybavení MeSH
• elektrochemie přístrojové vybavení   metody   MeSH
• enzymy imobilizované MeSH
• imunoenzymatické techniky přístrojové vybavení   metody   MeSH
• koenzymy chemie   MeSH
• křenová peroxidasa chemie   genetika   MeSH
• mikrofluidika přístrojové vybavení   metody   MeSH
• monitorování životního prostředí přístrojové vybavení   metody   MeSH
• peroxid vodíku analýza   MeSH
• peroxidasy chemie   MeSH
• rekombinantní proteiny chemie   MeSH
• reprodukovatelnost výsledků MeSH
• senzitivita a specificita MeSH
• simazin analýza   MeSH
• Publikační typ
• časopisecké články MeSH
• hodnotící studie MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH
• validační studie MeSH
• Názvy látek
• enzymy imobilizované MeSH
• glucose peroxidase MeSH Prohlížeč
• koenzymy MeSH
• křenová peroxidasa MeSH
• peroxid vodíku MeSH
• peroxidasy MeSH
• rekombinantní proteiny MeSH
• simazin MeSH

A new type of electrochemical biosensors in a flow injection system with printed electrodes were developed and tested. A filter disc (7 mm diameter) with immobilized enzyme was placed at the printed electrode. This conception combines the advantages of biosensors with a bioreceptor at the electrode surface and systems with spatially separated enzymatic and detection parts. Filters of different composition (glass, quartz, and cellulose), thickness, porosity, and ways of binding enzyme to their surface were tested. Only covalent bonds throughout a filter-aminosilane-glutaraldehyde-enzyme chain ensured a long-time and reproducible biosensor response. The developed method of biosensor preparation has been successfully applied to enzymes glucose oxidase, laccase and choline oxidase. The dependences of peak current on detection potential, flow rate, injection volume, analyte concentration as well as biosensor lifetime and reproducibility were investigated for glucose oxidase biosensor. The sensitivity of measurements was two or more times higher than that of biosensor with a mini-reactor filled by powder with immobilized enzyme. The developed biosensor with laccase was tested by determining dopamine in the pharmaceutical infusion product Tensamin®. Results of the analysis (40.0 ± 0.7 mg mL-1, SD = 0.8 mg mL-1, RSD = 1.85 %, N = 11) show a good agreement with the manufacturer's declared value.

• Klíčová slova
• Biosensors, Electrochemistry, Enzymatic discs, Flow injection analysis, Printed electrodes,
• MeSH
• biosenzitivní techniky * metody   MeSH
• elektrody MeSH
• enzymy imobilizované chemie   MeSH
• glukosa MeSH
• glukosaoxidasa * chemie   MeSH
• lakasa MeSH
• reprodukovatelnost výsledků MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• enzymy imobilizované MeSH
• glukosa MeSH
• glukosaoxidasa * MeSH
• lakasa 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.

• Klíčová slova
• Automation, Bisphenol A, Dynamic leaching, Microplastics, Phthalates, Seawater,
• MeSH
• automatizace MeSH
• chemické látky znečišťující vodu analýza   MeSH
• chromatografie kapalinová metody   MeSH
• kinetika MeSH
• mořská voda chemie   MeSH
• plastické hmoty analýza   MeSH
• vysokoúčinná kapalinová chromatografie MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chemické látky znečišťující vodu MeSH
• plastické hmoty MeSH

UNLABELLED: 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.

• Klíčová slova
• Azo dyes, Chemometrics, Chromatography, Flow injection analysis, Food adulteration, Spices,
• Publikační typ
• časopisecké články MeSH

Chiral analysis is an important task of analytical chemistry. Besides separation techniques, mass spectrometry can be applied in this field. One mass spectrometric approach is based on Cooks' kinetic method. The method was successfully applied in a static system in which the concentration of the analyte as well as the chiral selector solution was constant during the experiment. The application of the kinetic method in dynamic systems (changing concentration of analyte) is presented. Such systems allow the speeding up of the analytical process (flow injection analysis (FIA)) or the use of the kinetic method for chiral detection after liquid chromatographic separation. The influence of the concentration of the components of the chiral selector solution as well as its flow rate on the recognition of enantiomers was evaluated. A new procedure for correction for the differences between ratio of enantiomers in the liquid phase and their observed ratio in the gas phase is also described. A significant improvement in accuracy using this procedure was achieved. Applicability of the method was demonstrated in the analysis of amino acids using FIA as well as HPLC/MS. After an achiral separation of leucine and isoleucine, chiral mass spectrometric detection was successfully used for enantiomeric recognition.

• MeSH
• algoritmy * MeSH
• aminokyseliny chemie   MeSH
• hmotnostní spektrometrie metody   MeSH
• isomerie * MeSH
• kinetika MeSH
• průtoková injekční analýza metody   MeSH
• vysokoúčinná kapalinová chromatografie metody   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• aminokyseliny MeSH

Short-chain fatty acids (SCFAs) are the main metabolites produced by bacterial fermentation of non-digestible carbohydrates in the gastrointestinal tract. They can be seen as the major flow of carbon from the diet, through the microbiome to the host. SCFAs have been reported as important molecules responsible for the regulation of intestinal homeostasis. Moreover, these molecules have a significant impact on the immune system and are able to affect inflammation, cardiovascular diseases, diabetes type II, or oncological diseases. For this purpose, SCFAs could be used as putative biomarkers of various diseases, including cancer. A potential diagnostic value may be offered by analyzing SCFAs with the use of advanced analytical approaches such as gas chromatography (GC), liquid chromatography (LC), or capillary electrophoresis (CE) coupled with mass spectrometry (MS). The presented review summarizes the importance of analyzing SCFAs from clinical and analytical perspective. Current advances in the analysis of SCFAs focused on sample pretreatment, separation strategy, and detection methods are highlighted. Additionally, it also shows potential areas for the development of future diagnostic tools in oncology and other varieties of diseases based on targeted metabolite profiling.

• Klíčová slova
• biomarker, cancer, capillary electrophoresis, chromatography, mass spectrometry, separation methods, short-chain fatty acids,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

About eight years ago, a new automation approach and flow technique called "Lab-In-Syringe" was proposed. It was derived from previous flow techniques, all based on handling reagent and sample solutions in a flow manifold. To date Lab-In-Syringe has evidently gained the interest of researchers in many countries, with new modifications, operation modes, and technical improvements still popping up. It has proven to be a versatile tool for the automation of sample preparation, particularly, liquid-phase microextraction approaches. This article aims to assist newcomers to this technique in system planning and setup by overviewing the different options for configurations, limitations, and feasible operations. This includes syringe orientation, in-syringe stirring modes, in-syringe detection, additional inlets, and addable features. The authors give also a chronological overview of technical milestones and a critical explanation on the potentials and shortcomings of this technique, calculations of characteristics, and tips and tricks on method development. Moreover, a comprehensive overview of the different operation modes of Lab-In-Syringe automated sample pretreatment is given focusing on the technical aspects and challenges of the related operations. We further deal with possibilities on how to fabricate required or useful system components, in particular by 3D printing technology, with over 20 different elements exemplarily shown. Finally, a short discussion on shortcomings and required improvements is given.

• Klíčová slova
• 3D printing of instrument elements, Lab-In-Syringe, automation of sample pretreatment, potentials and troubles, system setup and operation modes, tips and tricks in method development,
• MeSH
• chemické techniky analytické přístrojové vybavení   metody   normy   MeSH
• injekční stříkačky * MeSH
• laboratorní automatizace * MeSH
• limita detekce MeSH
• reprodukovatelnost výsledků MeSH
• Publikační typ
• časopisecké články MeSH