Sorption Of Analytes Research Articles

Multiscale simulation of liquid chromatography: Effective diffusion in macro–mesoporous beds and the B-term of the plate height equation

We performed multiscale simulations of analyte sorption and diffusion in hierarchical porosity models of monolithic silica columns for reversed-phase liquid chromatography to investigate how the mean mesopore size of the chromatographic bed and the analyte-specific interaction with the chromatographic interface influence the analyte diffusivity at various length scales. The reproduced experimental conditions comprised the retention of six analyte compounds of low to moderate solute polarity on a silica-based, endcapped, C18 stationary phase with water‒acetonitrile and water–methanol mobile phases whose elution strength was varied via the volumetric solvent ratio. Detailed information about the analyte-specific interfacial dynamics received from molecular dynamics simulations was incorporated through appropriate linker schemes into Brownian dynamics diffusion simulations in three hierarchical porosity models received from physical reconstructions of silica monoliths with a mean macropore size of 1.23 µm and mean mesopore sizes of 12.3, 21.3, or 25.7 nm. The mean mesopore size was found to have a similar influence on the effective mesopore diffusivity as the analyte polarity and the mobile-phase elution strength, which together determine the analyte residence time on a column. A smaller mesopore size attenuated the increase of the effective mesopore diffusivity with increasing mobile-phase elution strength significantly. The effective bed diffusivity was limited by the analyte residence time rather than by morphological details of the mesopore space. The stronger an analyte was retained by the chromatographic interface inside the mesopores, the slower became the mass transfer between the pore space hierarchies and the lower was the effective bed diffusivity. The B-terms of the plate height equation were finally generated with the bed diffusivities and phase-based retention factors derived from the hierarchical porosity models using additional information about the stationary-phase limit obtained from the analysis of analyte–bonded phase contacts. The B-terms highlight analyte- and mobile phase-specific behavior relevant to isocratic and gradient elution conditions in chromatographic practice. In particular, U-shaped B-term curves are observed due to the dominating contribution of the retention factor and the bed diffusivity to the B-term at low and high elution strength of the mobile phase, respectively.

Determination of Tetracaine and Oxymetazoline in Drugs and Saliva via Potentiometric Sensor Arrays Based on Fluoropolymer/Polyaniline Composites

AbstractA growing interest in dental practice in intranasal anesthesia using tetracaine and oxymetazoline dictates the need for their simultaneous determination in combination drugs and human saliva. Potentiometric multisensory systems based on perfluorosulfonic acid membranes, including polyaniline‐modified ones, were developed for these purposes. A change in the distribution of the sensor sensitivity to the related analytes was achieved by variation of the conditions for concentration polarization at the membrane interface with a studied solution due to a change in the intrapore volume, nature, and availability of the sorption centers, as well as the hydrophilicity of the membrane surface that were specified by the conditions for their synthesis and subsequent hydrothermal treatment. Reversibility of the analyte sorption using the chosen conditions for regeneration provided long‐term stable work of both the sensors and the calibration equations established by multivariate linear regression. The membrane modification promoted their resistance to fouling. The relative errors of the simultaneous tetracaine and oxymetazoline determination in the combination drug solutions were no greater than 7% and 11%, while in the artificial saliva solutions, they were 15% and 17%, respectively, when an array of the cross‐sensitive sensors based on the composite membranes prepared by different methods was used. The analysis errors were reduced to 3%–6% when analyzing the drug and to 0.2%–6% when analyzing the artificial saliva if an array was organized with the sensors based on the membrane with the dopant and the membrane without it, due to the decreasing correlation between their responses.

Elemental Analysis with Sorption Preconcentration by Graphene Oxide for Mineral Water by Inductively Coupled Plasma – Optical Emission and Mass Spectrometries (ICP-OES and ICP-MS)

The paper discusses using sorption preconcentration of elements from mineral waters by graphene oxide. The procedure aims to extract heavy metals such as Cd, Cr, Cu, Pb, Zn and other analytes from solution. Inductively coupled plasma – mass spectrometry (ICP-MS) and inductively coupled plasma – optical emission spectrometry (ICP-OES) were used to determine the analyte content. Graphene oxide was obtained by microwave exfoliation of graphite oxide. The sorption of analytes on the graphene oxide at different pH values and coexisting ion effect were studied in detail. Preliminary preconcentration of analytes provides good extraction recoveries using the optimal conditions. The limits of detection (LODs) of 27 analytes for the developed procedure ranged 0.1 to 200 ng L−1 for ICP-MS and from 5 to 1000 ng L−1 for ICP-OES. Sorption concentration provides recoveries of analytes from 80 to 110%. Graphene oxide was successfully employed for the sorption preconcentration of analytes from mineral and tap water.

Microplastics in the environment: analytical chemistry methods, sorption materials, risks and sustainable solutions.

This Feature Article reports general and more specific aspects about microplastic (MP) contamination in continental and marine waters as well as in terrestrial environment. It describes a critical vision of the analytical methods commonly used for MP characterization and determination, including recommendations on green analytical chemistry (GAC) protocols. Insights into MPs as sorption materials and carriers for a variety of emerging contaminants like pharmaceuticals and pesticides are highlighted. Risks to biota living in aquatic and terrestrial environments and human-health-related effects with specific examples of surface and groundwater used for drinking water sources near contaminated sites like landfills are summarized. Lastly, sustainable solutions for how to improve the analysis and comparison of MP detection at the global level is given, including the need for standardized analytical protocols as well as the performance of additional interlaboratory exercises. Additional recommendations include a global database on MP levels made available to all authors to better compare their data qualitatively with that previously published. Policy and remediation actions on how to reduce and mitigate MP pollution may include different types of actions like an improved waste management and reuse system, the development of bioplastics and new plastic materials, as well as legally binding additional funding to cope with increasing plastic pollution at the global scale.

Developing Green Sorbents Derived from Natural Materials for Microextraction and Determination of Emerging Contaminants

Developing Green Sorbents Derived from Natural Materials for Microextraction and Determination of Emerging Contaminants

Metal-Phenolic Film Coated Quartz Crystal Microbalance as a Selective Sensor for Methanol Detection in Alcoholic Beverages.

The facile real-time monitoring of methyl content in fermented beverages is of fundamental significance in the alcohol and restaurant industry, since as little as 4 mL of methanol entering the blood may cause intoxication or blindness. So far, the practical applicability of available methanol sensors, including the piezoresonance analogs, is somewhat limited to laboratory use due to the complexity and bulkiness of the measuring equipment involving multistep procedures. This article introduces a hydrophobic metal-phenolic film-coated quartz crystal microbalance (MPF-QCM) as a novel streamlined detector of methanol in alcoholic drinks. Unlike other QCM-based alcohol sensors, our device operates under saturated vapor pressure conditions, permitting rapid detection of methyl fractions up to seven times below the tolerable levels in spirits (e.g., whisky) while effectively suppressing the cross-sensitivity to interfering chemical compounds such as water, petroleum ether or ammonium hydroxide. Furthermore, the good surface adhesion of metal-phenolic complexes endows the MPF-QCM with superior long-term stability, contributing to the repeatable and reversible physical sorption of the target analytes. These features, combined with the lack of mass flow controllers, valves and connecting pipes delivering the gas mixture, outline the likelihood for future design of a portable MPF-QCM prototype suitable to point-of-use analysis in drinking establishments.

Investigation of Imidazolium-Based Ionic Liquids as Additives for the Separation of Urinary Biogenic Amines via Capillary Electrophoresis

Ionic liquids (ILs), such as imidazoles, can be used to prevent the sorption of analytes onto the walls of the capillary. Prior works have confirmed that coating the capillary wall with a cationic layer can increase its surface stability, thereby improving the repeatability of the separation process. In this study, micellar electrokinetic chromatography (MEKC) is employed to evaluate how two ILs with different anions—namely, 1-hexyl-3-methylimidazolium chloride [HMIM+Cl−] and 1-hexyl-3-methylimidazolium tetrafluoroborate [HMIM+BF4−]—affect the separation efficiency for biogenic amines (BAs) such as metanephrine (M), normetanephrine (NM), vanilmandelic acid (VMA), and homovanillic acid (HVA) in urine samples. To this end, solid-phase extraction (SPE) is employed using different sample pH values, with the results demonstrating that HVA and VMA is easily extracted at a sample pH of 5.5, while a sample pH of 9.0 facilitated the extraction of M and NM. In the applied SPE protocol, selected analytes were isolated from urine samples using hydrophilic–lipophilic-balanced (HLB) columns and eluted with methanol (MeOH). The validation data confirmed the method’s linearity (R2 > 0.996) for all analytes within the range of 0.25–10 µg/mL. The applicability of the optimized SPE-MEKC-UV method was confirmed by employing it to quantify clinically relevant BAs in real urine samples from pediatric neuroblastoma (NBL) patients.

Comparative study on high-voltage nanosecond pulses and dielectric barrier discharge effects on surface morphology and physico-chemical properties of natural pyrrhotite

In this paper we used analytical electron microscopy, potentiometric titration (electrode potential), sorption and flotation measurements and other methods to study changes in the surface morphology, electrochemical, and physicochemical properties of the natural pyrrhotite exposed to nonthermal action of the repetitive nanosecond high-power electromagnetic pulses and low-temperature plasma of dielectric barrier discharge in air at atmospheric pressure. As a result of exposure to high-voltage nanosecond pulses, a sharp shift in the electrode potential of pyrrhotite to the region of negative values caused a decrease in the sorption of the anionic collector on the mineral, a decrease in the hydrophobicity of the surface and flotation of the mineral was due to an increase in the content of oxidized ferric iron on the mineral surface. Dielectric barrier discharge treatment caused the shift of the electrode potential to the region of negative values (–60 mV) in the range of pH 9.7-12, which causes the effect of a decrease in the sorption and flotation activity of pyrrhotite. The advantages of using the short-term (10-30 seconds) energy impacts for structural and chemical modification of the surface and physicochemical properties of sulfide minerals of iron are shown.

The critical evaluation of the effects of imidazolium-based ionic liquids on the separation efficiency of selected biogenic amines and their metabolites during MEKC analysis

Ionic liquids (ILs) such as imidazole can be used to prevent the sorption of analytes onto the quartz walls of the capillary. Coating the capillary wall with a cation layer increases its surface stability, consequently improving the repeatability of separation process. Currently, examining the effects of dynamic coatings on the capillary wall is an emerging trend in capillary electrophoresis (CE) research. This study uses micellar electrokinetic chromatography (MEKC) to evaluate how ILs in the background electrolyte (BGE) affect the separation efficiency of biogenic amines (BAs). Specifically, this research focuses on 12 ILs built from cations containing an imidazole ring with different alkyl substituents and anions, as well as one IL containing a pyridinium cation with tetrafluoroborate anion. All analyzed ILs, which were added to the BGE in concentrations ranging from 1 to 20 mM, were tested for their ability to improve the electrophoretic separation of selected BAs, namely: homovanillic acid (HVA), vanililmandelic acid (VMA), dihydroxyphenylglicol (DHPG), 3-metoxy-4-hydroxyphenyl glicol (MHPG), normetanephrine (NM), metanephrine (M), and dihydroxyphenylacetic acid (DOPAC). The results showed that the most effective ILs added to the BGE were those with a chloride anion (1-hexyl-3-methylimidazolium chloride [HMIM+Cl−] and 1-ethyl-3-methylimidazolium chloride [EMIM+Cl−]) and those with a tetrafluoroborate anion (1-hexyl-3-methylimidazolium tetrafluoroborate [HMIM + BF4−]). Improved separation efficiency was also obtained for the BGE containing 1-hexyl-3-methylimidazolium hexafluorophosphate [HMIM + PF6−]. On the other hand, ILs with trifluoromethanesulfonate [OTf−] or bis(trifluoromethylsulfonyl)imide [NTf2-] anions, even at low concentrations in the BGE, disturbed the flow of current through the capillary and worsened the separation process. Overall, this study provides a critical evaluation of the impact of different types and concentrations of ILs on the performance of the MEKC method during the analysis of selected BAs.

Evaluation of an alternative sorbent for passive sampling of the herbicides 2,4-D and Dicamba in the air

The present study aimed to evaluate the Strata-X® sorbent, commonly used in cartridges, through analysis by high-performance liquid chromatography coupled with mass spectrometry. Due to the different physical-chemical characteristics of the compounds, different conditions of chromatography and mass analysis were necessary. The developed methods were validated in terms of selectivity, linear range, linearity (coefficient of determination, r2), the limit of detection (LOD), the limit of quantification (LOQ), accuracy (recovery, %), and precision (RSD, %). The results allowed us to select efficient extraction methods, using methanol acidified to pH 2 with formic acid, to elute the herbicides 2,4-D and dicamba in both sorbent materials. Besides, the Strata-X® sorbent was efficient in the sorption of analytes; thus, we indicate it for potential use in air sampling as an alternative to XAD-2.

A novel vortex assisted dispersive solid phase extraction of some trace elements in essential oils and fish oil

In this paper, a novel vortex assisted solid phase extraction procedure combined with inductively coupled plasma optic emission spectrometry was presented for determination of Mn, Cu, Ni, Cr, Cd and Pb directly in oily matrix. The suggested separation and preconcentration method was based on simultaneous sorption of the target analytes from real essential oil matrix onto γ-Al2O3 functionalized with fluorescein (Al-Flr) and transfer to aqueous eluent prior to quantification. The effect of different parameters including sorption and elution time, sample volume, eluent type and concentration and interfering ions were investigated. The working conditions were given as follows, vortex agitation for sorption and elution 40 s, sample volume 20 mL, eluent type HCl, eluent concentration 0.3 mol L−1. The detection limits were found to be 0.7 μg L−1 for Mn, 4.1 μg L−1 for Cu, 1.0 μg L−1 for Ni, 1.6 μg L−1 for Cr, 0.7 μg L−1 Cd and 1.0 μg L−1 Pb. The evaluation of the accuracy and precision of the method was tested via metallo-organic certified reference material. The recovery values have warranted the accuracy and found between 98.4 and 103.3% with 2.6–6.4% relative standard deviation (RSD, %). The sampling frequency of the procedure was calculated as 11.25 h−1.Finally, the proposed analytical method was successfully applied on analyte spiked and unspiked apricot, black cumin, pine turpentine, thyme, mint essential oils and fish oil samples without any need of performing mineralization pretreatments.

Preconcentration of Phenolic Compounds on Carbon Sorbents and Their Chromatographic Determination in Aqueous Extracts of Medicinal Plants

A possibility of using carbon sorbents for the extraction, preconcentration, and chromatographic determination of phenolic substances of plant origin is investigated. A method is proposed for the preconcentration of biologically active substances from extracts of medicinal plants with carbon sorbents followed by the desorption of analytes with organic solvents at elevated temperature and pressure. Some sorption characteristics of carbon materials Supelclean ENVI-Carb and HyperSep Hypercarb in relation to phenolcarboxylic acids and flavonoids isolated from aqueous extracts of St. John’s Wort Hypericum perforatum L. are studied. The conditions of the sorption and desorption of analytes of various classes are optimized. A possibility of using carbon sorbents for the extraction and preconcentration of phenolic substances from aqueous extracts of various medicinal plants is shown using an examples of creeping thyme Thymus serpyllum L. and sage Salvia officinalis L.

A rotating disk sorptive extraction based on hydrophilic deep eutectic solvent formation

An elegant preconcentration method assumed sorption of polar analytes from complex non-polar matrices on a rotating disk based on hydrophilic deep eutectic solvent formation is presented for the first time. The surface of poly(vinylidene fluoride-co-tetrafluoroethylene) rotating disk was coated with choline chloride acted as a precursor of deep eutectic solvent (hydrogen bond acceptor). The rotating disk was immersed in vegetable oil sample and phenolic compounds (hydrogen bond donors) were efficient separated on the disk during its rotation due to deep eutectic solvent formation. Ability of hydrophilic deep eutectic solvent decomposition in aqueous phase was used for fast analytes elution from the disk surface (2 min). Finally, the obtained aqueous solution of phenolic compounds and choline chloride was analyzed by high-performance liquid chromatography with fluorescence detection. Under optimal conditions, the limits of detection for gallic acid, protocatechuic acid, tyrosol, vanillic acid, p-coumarinic acid, syringaldehyde and thymol were in the range of 10–60 μg L−1. The developed approach allowed to significantly reduce sorption and elution time in comparison with previously reported rotating disk sorptive extraction approaches. The extraction mechanism based on deep eutectic solvent formation provided selective separation of target analytes with absolute extraction recovery in the range of 66–87%.

Cellulose mini-membranes modified with TiO2 for separation, determination, and speciation of arsenates and selenites

Sorptive and selective mini-membranes based on TiO2 directly synthesized onto cellulose filters (TiO2@cellulose) have been developed. The in situ synthesis of TiO2@cellulose applied is simple and economically advantageous. The obtained membranes can be useful for (1) separating arsenic(V) and selenium(IV) from other ions and organic matter, (2) speciation of arsenic and selenium, and (3) determining ulratraces of these ions in water samples. The membranes exhibit good stability and high maximum adsorption capacities for Se(IV) (71 mg g−1) and As(V) (41 mg g−1). A monolayer chemical adsorption of analytes on the membranes was confirmed. The structure of membranes was examined with scanning electron microscopy, x-ray diffractometry, and micro energy-dispersive x-ray fluorescence spectrometry (μ-EDXRF). The membranes were characterized by homogenous distribution of TiO2 onto cellulose. The TiO2@cellulose was used as a new sorbent in micro-solid phase extraction for determination of Se(IV) and As(V) by EDXRF. Using direct analysis of mini-membranes after sorption of analytes avoids the elution step. Thus, the proposed procedure is an attractive and solvent-free option for quantitative monitoring of Se(IV) and As(V) in different materials. Both analytes were quantitatively and simultaneously separated/determined from samples at pH 2 with very good recovery (close to 100%), precision (4.5%), and detection limits (0.4 ng mL−1 Se and 0.25 ng mL−1 As). TiO2@cellulose membranes were applied to water analysis.Graphical-abstractEffective method for determination of ultra trace arsenates and selenites using cellulose-based sorbent

Pattern Recognition of Solid Materials By Multiple Probe Gases

Introduction Chemical sensor arrays have attracted significant attention as a powerful tool for detecting, discriminating, and identifying target analytes, in particularly, various smells consisting of a complex mixture of gaseous molecules. In a chemical sensor array, sensing signals are obtained by measuring interactions induced by the sorption of target analytes in sensing materials designed to respond to a wide range of chemical classes. Although a wide range of applications has been demonstrated in a variety of fields, these pattern recognition-based analyses are basically limited to gaseous analytes.In this study, we propose the reverse approach, that is, pattern recognition of solid materials. As the sensing signals of chemical sensors are based on the interaction between gases and solids, a sensing element and a target analyte can be exchanged, i.e. solid materials as target analytes and gaseous molecules as sensing probes, leading to the pattern recognition of solid materials (Figure 1a). To demonstrate this new approach, we focus on a nanomechanical Membrane-type Surface stress Sensors (MSS) [1] as an example of sensing platform. A nanomechanical sensor detects mechanical information derived from the interactions between gaseous molecules and solid materials with high sensitivity [2]. Since it has been confirmed that almost all kinds of solid materials including organic small molecules, polymers and inorganic nanoparticles provide some signals as a result of the gas-solid interaction [1,3], a nanomechanical sensor is an ideal platform to examine various kinds of solid materials. We have demonstrated successful discrimination of polymers having different molecular weights as well as those composed of different monomers by means of pattern recognition [4]. Results and Conclusions We performed identification of 4 different polymers (polystyrene PS; poly(4-methylstyrene) P4MS; polycaprolactone PCL; poly(vinylidene fluoride) PVF) through the pattern recognition. Twelve different vapors are used as probes to acquire the signals for each gas-solid interaction. Upon exposure of each vapor, the polymers exhibited unique responses, reflecting the differences in chemical and physical affinity between each polymer and vapor. For the obtained dataset, we conducted principal component analysis (PCA) and linear discriminant analysis (LDA), respectively. With the all features from the 12 vapors, the 4 different polymers can be clearly distinguished by forming well-separated clusters by PCA as well as LDA (Figure 1b and c). On the LDA plane, PS and P4MS form clusters close to each other, reflecting their similarity in the chemical and physical affinity to each probe gas.We also developed machine learning models based on support vector machine (SVM) classifier. To optimize and evaluate the models, we employed 5 × 2 cross validation. All combinations of each probe gas were calculated to create SVM model. Identification accuracy depending on the combination of probe gases is shown as a dot plot in Figure 2c. Remarkably, almost a quarter of all combinations of probe gases resulted in 100% identification accuracy with 2 to 12 kinds of probe gases by the SVM analysis (Figure 1d and e). These results clearly indicate that the appropriate selection of probe gases depending on the target solid samples leads to the highly accurate and efficient identification.To evaluate further applicability of the pattern recognition of solid materials, we demonstrated the identification of molecular weight of polymers. The LDA provided clear discrimination of polystyrenes including PS and P4MS in terms of molecular weight. These results indicate that the pattern recognition can be also effectively applied to solid materials to identify each analyte even with similar chemical and physical properties. Furthermore, we also demonstrated the practical solids, in this case, differences of rice. Rice was grinded, and the resulting powder was coated on the MSS. By using water and ethanol as a set of probe gases, rice originated from different places can be clearly discriminated by PCA. Since the major components of rice are amyloid and amylopectin, this approach can be discriminate very minute differences. Conclusion In this study, we have demonstrated that solid specimens can be identified by pattern recognition, achieving 100% accuracy in the case of some specific combinations of probe gases. As proved by means of SVM as well as PCA and LDA, even slight differences in material properties such as rice can be also discriminated through this approach. Since any kind of gaseous or volatile molecules can be potentially utilized as a probe for this pattern recognition-based solid materials identification, this approach possesses unlimited possibilities to differentiate solid materials. The potential target solid materials of this concept include inorganic nanoparticles, functional organic materials and biomolecules. While nanomechanical sensors provide a versatile sensing platform, this concept is not limited to nanomechanical sensors but can be expanded to a variety of chemical sensors. Therefore, the presented concept of the pattern recognition-based analysis of solid materials will open a new world of chemical sensors and materials science.

Exploration of the Solid-State Sorption Properties of Shape-Persistent Macrocyclic Nanocarbons as Bulk Materials and Small Aggregates.

Porous molecular materials combine benefits such as convenient processability and the possibility for atom-precise structural fine-tuning which makes them remarkable candidates for specialty applications in the areas of gas separation, catalysis, and sensing. In order to realize the full potential of these materials and guide future molecular design, knowledge of the transition from molecular properties into materials behavior is essential. In this work, the class of compounds termed cycloparaphenylenes (CPPs)-shape-persistent macrocycles with built-in cavities and radially oriented π-systems-was selected as a conceptually simple class of intrinsically porous nanocarbons to serve as a platform for studying the transition from analyte sorption properties of small aggregates to those of bulk materials. In our detailed investigation, two series of CPPs were probed: previously reported hoop-shaped [n]CPPs and a novel family of all-phenylene figure-8 shaped (lemniscal) bismacrocycles, termed spiro[n,n]CPPs. A series of nanocarbons with different macrocycle sizes and heteroatom content have been prepared by atom-precise organic synthetic methods, and their structural, photophysical, and electronic attributes were disclosed. Detailed experimental studies (X-ray crystallography, gas sorption, and quartz-crystal microbalance measurements) and quantum chemical calculations provided ample evidence for the importance of the solid-state arrangement on the porosity and analyte uptake ability of intrinsically porous molecular nanocarbons. We demonstrate that this molecular design principle, i.e., incorporation of sterically demanding spiro junctions into the backbone of nanohoops, enables the manipulation of solid-state morphology without significantly changing the nature and size of the macrocyclic cavities. As a result, the novel spiro[n,n]CPPs showed a remarkable performance as high affinity material for vapor analyte sensing.

Comparison of silica-based materials for organophosphorus pesticides sampling and occupational risk assessment

A novel air sampler has been designed containing a sorbent based on UVM-7 mesoporous silica doped with Ti. The sorbent has been applied for the determination of organophosphorus pesticides in occupational air, followed by gas chromatography with mass spectrometry detection. Thus, several silica materials with different structures (mesoporous UVM-7 and microporous xerogels) were synthesized, and modified with the addition of Ti and Fe. The structure of these materials was proved by transmission electronic microscopy, energy-dispersive X-ray, X-ray diffraction, nitrogen adsorption-desorption and UV–Vis and Raman spectroscopy. The potential of these materials for the retention of pesticides was evaluated and Ti25-UVM-7 was selected as the best solid phase for analyte sorption. Then, several sampling parameters were optimized and analytical features such as breakthrough volume were determined. Using the designed samplers, quantitative retentions were achieved with recoveries in the range 93–107% for all analytes except for diazinon (82%). RSD values below 13% were obtained. Likewise, the sensitivity of the method was studied, and limits of quantification below 0.5 μg m−3 were obtained for all pesticides. The reusability of the material was also proved. The developed procedure has been applied to the air sampling and occupational risk assessment, during and after methyl-chlorpyrifos application in orange plantations. High concentrations and exposure rates above the limit value for ensure safe work conditions were obtained. At the same time, the air was sampled with XAD-2 samplers as a reference method, and results obtained with both devices were statistically comparable.

Sequential injection analysis system with DGA resin for sample pretreatment in ICP-MS determination of 239Pu in nuclear industry samples

The monitoring of the presence of plutonium isotopes is a very important issue in both nuclear energy industry and environmental protection for human health risk assessment. The developed method for the determination of 239Pu isotope with ICP-QMS detection is based on the use of sequential injection analysis (SIA) system for the pretreatment of samples to be analyzed with the use of a commercial sorbent called diglycolamide (DGA-b) for the analyte preconcentration and separation from 238U, which is the source of the most significant isobaric interference 238U1H+. Optimizing the size of the sorbent bed and the conditions of analyte sorption and elution of plutonium and uranium provides the analytical procedure for 239Pu determination, where at total analysis time of 45 min (at flow rate 10 mL min−1) the evaluated method detection limit (MDL) for 100 mL sample volume was 88 mBq L−1. This is satisfactory detectability for applications in both technological and environmental samples.

Covalent Coatings of Quartz Capillaries for the Electrophoretic Determination of Biologically Active Analytes

One of the main limitations of capillary electrophoresis (CE) is the sorption of basic compounds on the walls of a quartz capillary. To prevent this phenomenon in CE, supporting electrolytes with various additives that prevent the sorption of analytes due to the formation of dynamic coatings are commonly used. Alternatively, covalent coatings, which have a number of advantages and expand the analytical capabilities of CE, are used. The main methods of the formation of coatings covalently bound to the walls of a quartz capillary are considered.

Skeleton pseudomorphs of nanostructured silver for the surface-enhanced Raman spectroscopy

Pseudomorphs (mesocages) of metallic silver were prepared via either a shape-preserving reduction of polyhedral Ag2O precursors with H2O2 in aqueous ammonia or an ultrasonic spray pyrolysis of aqueous diamminesilver(i) hydroxide. Both the materials were revealed as suitable for the direct analysis at 0.1–1 μm concentrations of oil pollutants and pharmaceutical substances using surface-enhanced Raman spectroscopy due to their unique morphology providing either a larger surface area for sorption of analytes or additional ‘hot spots’ resulting in the enhancement factors of 106–108.