Hana Sklenářová - Academia.edu (original) (raw)

Papers by Hana Sklenářová

Chemicke Listy, 2009

A HPLC method for the determination of clotrimazole and its degradation products. (2-chlorophenyl... more A HPLC method for the determination of clotrimazole and its degradation products. (2-chlorophenyl)diphenylmethanol and imidazole, in Clotrimazol spray 1 % was developed. The development was focused on the selection of an optimal column, composition and pH of the mobile phase, and internal standard. A Discovery ZR-PBD column (5 ?m, 150 -× 4.6 mm) and spectrophotometric detection at 210 nm were selected. The optimal mobile phase was aqueous acetonitrile 1:1 (pH 9.7). The optimal injection volume and flow-rate were 3 ?l and 1 ml min-1, respectively. On the basis of robustness tests, ibuprofen was used as the internal standard. The analysis time was less than 4.5 min.

Elicitation is one of the methods for stimulation of secondary metabolism in plant cell cultures.... more Elicitation is one of the methods for stimulation of secondary metabolism in plant cell cultures. The present study tested HgCl2 solutions (0.5-100 μM) as an elicitor of the production of coumarins in angelica cell cultures. The HgCl2 toxicity was examined by evaluating its effect on cell growth (characterized by fresh and dry biomass at the end of a two-week subculture). Cultivations were performed in the dark or in light. The content of coumarins was determined fluorometrically by sequential injection analysis. The culture growth was not adversely affected by Hg concentrations up to 50 μM; the 100 μM concentration was lethal, independently of light conditions. HgCl2 stimulated production of coumarins. In the dark, the amount of coumarins in the medium increased with increasing Hg concentrations up to 20 μM (the coumarin contents in the medium increased by 70 % compared with control) while it was not influenced in cultured cells. In light, HgCl2 enhanced accumulation of coumarins b...

Journal of Pharmaceutical and Biomedical Analysis

Journal of Food Composition and Analysis

Journal of Chromatography A

An automatic flow-based system as a front end to liquid chromatography (LC) for on-line dynamic l... more 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.

Analytical Methods

Sequential injection analysis system with sensitive chemiluminescence detection using the flow-ba... more Sequential injection analysis system with sensitive chemiluminescence detection using the flow-batch detection cell was developed for real time monitoring of kinetic profiles of antioxidant activity of phenolic substances in luminol-Fe(III)-hydrogen...

Analytical and Bioanalytical Chemistry

AbstractA fully automated method for the determination of lovastatin in dietary supplements conta... more AbstractA fully automated method for the determination of lovastatin in dietary supplements containing red yeast rice has been developed. It uses a sequential injection analysis system combined with solid-phase extraction applying highly selective molecularly imprinted polymer sorbent. A miniaturized column for on-line extraction was prepared by packing 4.5 mg of the sorbent in a 5.0 × 2.5-mm-i.d. cartridge, which was used in the flow manifold. Sequential injection analysis manifold enabled all steps of lovastatin extraction and continuous spectrophotometric detection at 240 nm. A limit of detection of 60 μg g−1, a limit of quantitation of 200 μg g−1, and a linear calibration range of 200–2000 μg g−1 were achieved. Intra-day and inter-day precision values (RSD) were ≤ 6.7% and ≤ 4.9%, respectively, and method recovery values of spiked red yeast rice extracts at 200, 1000, and 2000 μg g−1 concentration levels were 82.9, 95.2, and 87.7%. Our method was used for determination of lovastatin lactone in four dietary supplements containing red yeast rice as a natural source of lovastatin, also known as monacolin K. The extracted samples were subsequently analyzed by the reference UHPLC-MS/MS method. Statistical comparison of results (F test, t test, α = 0.05) obtained by both methods did not reveal significant difference. A substantial advantage of the new automated approach is high sample throughput thanks to the analysis time of 7.5 min, miniaturization via down-scaling the extraction column, and smaller sample and solvent consumption, as well as reduced generation of waste. Graphical abstractᅟ

Talanta, 2017

A proof of concept of a novel automatic sample cleanup approach for metal assays in troublesome m... more A proof of concept of a novel automatic sample cleanup approach for metal assays in troublesome matrixes as a front-end sample pre-treatment to inductively coupled plasma optical emission spectroscopy - ICP-OES - is herein presented. Target metals, namely, copper, lead, and cadmium were complexed in-system quantitatively using ammonium pyrrolidine dithiocarbamate (APDC) and transferred into a minute volume of toluene as extractant employing lab-in-syringe magnetic stirring-assisted dispersive liquid-liquid microextraction (LIS-MSA-DLLME). After discharge of the sample, the analytes were back-extracted into nitric acid and injected on-line into ICP-OES. To promote and expedite this process in-syringe, advantage was taken from oxidative decomposition of the chelate by potassium iodate, reported in this article for the first time. Experimental conditions for LIS-MSA-DLLME were optimized by Box-Benkhen multivariate analysis using the geometric mean of analyte recoveries as the desirabil...

Journal of Luminescence

Abstract The effect of 0.01–100 µmol L −1 Quantum Dots (QDs) with different emission wavelengths ... more Abstract The effect of 0.01–100 µmol L −1 Quantum Dots (QDs) with different emission wavelengths (520–640 nm) and different surface modifications (mercaptopropionic, mercaptoundecanoic, thioglycolic acids and mercaptoethylamine) on permanganate-induced and luminol–hydrogen peroxide chemiluminescence (CL) was studied in detail by a sequential injection technique using a spiral detection flow cell and a flow-batch detection cell operated in flow and stop-flow modes. In permanganate CL system no significant enhancement of the CL signal was observed while for the luminol–hydrogen peroxide CL substantial increase (>100% and >90% with the spiral detection cell in flow and stop-flow modes, respectively) was attained for CdTe QDs. Enhancement exceeding 120% was observed for QDs with emissions at 520, 575 and 603 nm (sizes of 2.8 nm, 3.3 nm and 3.6 nm) using the flow-batch detection cell in the stop-flow mode. Pronounced effect was noted for surface modifications while mercaptoethylamine was the most efficient in CL enhancement compared to mercaptopropionic acid the most commonly applied coating. Significant difference between results obtained in flow and flow-batch conditions based on the entire kinetics of the extremely fast CL reaction was discussed. The increase of the CL signal was always accompanied by reduced lifetime of the CL emission thus application of QDs in flow techniques should be always coupled with the study of the CL lifetime.

Analytical chemistry, Jan 10, 2017

A proof of concept study involving the online coupling of automatic dispersive liquid-liquid micr... more A proof of concept study involving the online coupling of automatic dispersive liquid-liquid microextraction (DLLME) to inductively coupled plasma optical emission spectrometry (ICP OES) with direct introduction and analysis of the organic extract is herein reported for the first time. The flow-based analyzer features a lab-in-syringe (LIS) setup with an integrated stirring system, a Meinhard nebulizer in combination with a heated single-pass spray chamber, and a rotary injection valve, used as an online interface between the microextraction system and the detection instrument. Air-segmented flow was used for delivery of a fraction of the nonwater miscible extraction phase, 12 μL of xylene, to the nebulizer. All sample preparative steps including magnetic stirring assisted DLLME were carried out inside the syringe void volume as a size-adaptable yet sealed mixing and extraction chamber. Determination of trace level concentrations of cadmium, copper, lead, and silver as model analyte...

Microchemical Journal, 2016

Abstract Trace amounts of two sulfonylurea herbicides widely used for crops protection, metsulfur... more Abstract Trace amounts of two sulfonylurea herbicides widely used for crops protection, metsulfuron methyl (MSM) and chlorsulfuron (CSF) were simultaneously determined taking into account the different kinetic photodegradation behavior of their photoproducts in alkaline medium. As the analytes are present at trace concentration levels, a preconcentration by sorption on a mini-column packed with oxidized multiwall carbon nanotubes (ox-MWCNTs) at pH 3.0 was performed. The retained analytes were removed from the ox-MWCNTs mini-column with a mixture of ACN contained 10% (v/v) of NaOH pH 12.5. A total enrichment factor of 26-fold for a 14.50 mL sample volume was obtained. The eluate was photodegraded by UV radiation during 126 s and the fluorescent spectra corresponding to the analytes photoproducts were registered overtime between 300 and 500 nm. The kinetic second order data were analyzed by unfolded-partial least squares-residual bilinearization (U-PLS/RBL) and multidimensional-partial least squares-residual bilinearization (N-PLS/RBL) algorithms. The relative error of prediction (REP %) for N-PLS/RBL was 7.73% for MSM and 6.37% for CSF. In the case of U-PLS/RBL, this statistical parameter was 7.75% for MSM and 7.23% for CSF, respectively. The limits of detection (LOD) were 0.19 μg L− 1 for MSM and 1.14 μg L− 1 for CSF using N-PLS/RBL and 0.21 μg L− 1 for MSM and 1.03 μg L− 1 for CSF when U-PLS/RBL was applied. The entire procedure was performed in an on-line integrated fully automated flow system coupled to a low mercury UV lamp (15 W, 254 nm) and a spectrofluorometer. In this manner, the preconcentration, photodegradation and detection steps were performed in a reproducible way. After optimization, the method was successfully applied to the analysis of real water samples obtained in the south part of Buenos Aires province and used for irrigation and consumption.

Analytica Chimica Acta, 2016

A novel approach to the automation technique Lab-In-Syringe, also known as In-Syringe Analysis, i... more A novel approach to the automation technique Lab-In-Syringe, also known as In-Syringe Analysis, is proposed which utilizes a secondary inlet into the syringe void, used as a size-adaptable reaction chamber, via a channel passing through the syringe piston. This innovative approach allows straightforward automation of head-space single-drop microextraction, involving accurately controlled drop formation and handling, and the possibility of on-drop analyte quantification. The syringe was used in upside-down orientation and in-syringe magnetic stirring was carried out, which allowed homogenous mixing of solutions, promotion of head-space analyte enrichment, and efficient syringe cleaning. The superior performance of the newly developed system was illustrated with the development of a sensitive method for total ammonia determination in surface waters. It is based on head-space extraction of ammonia into a single drop of bromothymol blue indicator created inside the syringe at the orifice of the syringe piston channel and on-drop sensing of the color change via fiber optics. The slope of the linear relationship between absorbance and time was used as the analytical signal. Drop formation and performance of on-drop monitoring was further studied with rhodamine B solution to give a better understanding of the system's performance. A repeatability of 6% RSD at 10 μmol L(-1) NH3, a linear range of up to 25 μmol L(-1) NH3, and a limit of detection of 1.8 μmol L(-1) NH3 were achieved. Study of interferences proved the high robustness of the method towards humic acids, high sample salinity, and the presence of detergents, thus demonstrating the method superiority compared to the state-of-the-art gas-diffusion methods. A mean analyte recovery of 101.8% was found in analyzing spiked environmental water samples.

Analytical and Bioanalytical Chemistry, 2015

A novel flow-programming setup based on the sequential injection principle is herein proposed for... more A novel flow-programming setup based on the sequential injection principle is herein proposed for on-line monitoring of temporal events in cell permeation studies. The permeation unit consists of a Franz cell with its basolateral compartment mixed under mechanical agitation and thermostated at 37 °C. The apical compartment is replaced by commercially available Transwell inserts with a precultivated cell monolayer. The transport of drug substances across epithelial cells genetically modified with the P-glycoprotein membrane transporter (MDCKII-MDR1) is monitored on-line using rhodamine 123 as a fluorescent marker. The permeation kinetics of the marker is obtained in a fully automated mode by sampling minute volumes of solution from the basolateral compartment in short intervals (10 min) up to 4 h. The effect of a P-glycoprotein transporter inhibitor, verapamil as a model drug, on the efficiency of the marker transport across the cell monolayer is thoroughly investigated. The analytical features of the proposed flow method for cell permeation studies in real time are critically compared against conventional batch-wise procedures and microfluidic devices.

Anal. Methods, 2015

The simple colour reaction between aluminum(iii) and aluminon reagent was transferred to an autom... more The simple colour reaction between aluminum(iii) and aluminon reagent was transferred to an automated sequential injection system.

Analytical and Bioanalytical Chemistry, 2015

The use of small scale renewable sorbent material for automated solid phase extraction of multi-r... more The use of small scale renewable sorbent material for automated solid phase extraction of multi-residue pharmaceuticals in environmental samples exploiting the sequential injection analysis-bead injection with direct coupling to liquid chromatography-electrospray ionization tandem mass spectrometry (SIA-BI-μSPE-LC-ESI-MS/MS) is presented to determine beta-blockers, namely atenolol, sotalol, pindolol, acebutolol, timolol, metoprolol, labetalol, carazolol, propranolol and betaxolol. These compounds yielded the same product ions, therefore were affected in terms of quantification when flow injection analysis-mass spectrometry (FIA-MS) was used. Thus, analytes and matrix present in the sample travel together into the ionization source which can seriously affect the ionization efficiency and analyte signals due to monitoring over a short time period.

Talanta, Jan 15, 2012

A non-extractive sequential injection spectrophotometric method for the determination of molybden... more A non-extractive sequential injection spectrophotometric method for the determination of molybdenum has been developed. The method is based on the reaction between the thiocyanate complex of molybdenum and the polymethine dye (2-[2-(4-dipropylamino-phenyl)-vinyl]-1,3,3-trimethyl-3H-indolium chloride) in a hydrochloric acid medium. The calibration plot in the SIA system was linear from 0.080mgL(-1) to 1.92mgL(-1) of Mo; LOD was 0.021mgL(-1). The method was applied for the determination of molybdenum in spiked drinking water and mineral water.

Microchemical Journal, 2012

A novel approach for sequential injection-dispersive liquid-liquid microextraction (SI-DLLME) has... more A novel approach for sequential injection-dispersive liquid-liquid microextraction (SI-DLLME) has been suggested. The method is based on the aspiration and mixing of a sample and all required aqueous reagents in the holding coil of an SIA system, delivering it into a conical tube and adding in a mixture of extraction solvent, auxiliary solvent and disperser solvent at high flow rate, resulting in the formation of a cloudy state and the extraction of an analyte. The mixture of extraction and auxiliary solvent is immiscible with water and has a density significantly higher than that of water; consequently, the resulting fine droplets in the mixture, which contain the extracted analyte, are self-sedimented in a short time at the bottom of conical tube. Thus, no centrifugation and no use of a microcolumn are required for separation of the extraction phase. Afterwards, the extracted analyte is aspirated and transferred to a micro-volume Z-flow cell, and the absorbance is measured. The performance of the suggested approach is demonstrated by the SI-DLLME of thiocyanate ions in the form of ion associate with dimethylindocarbocyanine reagent, followed by spectrophotometric detection. A mixture of amyl acetate (as extraction solvent), tetrachloromethane (as auxiliary solvent) and acetonitrile (as disperser solvent) was selected for the DLLME procedure. The appropriate experimental conditions for conventional DLLME and automated SI-DLLME were investigated. The analytical performance of both these procedures was compared. The absorbance of the colored extracts at wavelength 555 nm obeys Beer's law in the range of 3.13-28.2 for conventional DLLME and 0.29-5.81 mg L − 1 of SCN for SI-DLLME, and the limit of detection, calculated from a blank test based on 3 s, is 0.110 for conventional DLLME and 0.017 mg L − 1 for SI-DLLME.

Guest edited as a special report on "New Methods for Drug Analysis in Biological Samples and Othe... more Guest edited as a special report on "New Methods for Drug Analysis in Biological Samples and Other Matrixes" by Danica Agbaba and Andjelija Malenovic.

Chemicke Listy, 2009

A HPLC method for the determination of clotrimazole and its degradation products. (2-chlorophenyl... more A HPLC method for the determination of clotrimazole and its degradation products. (2-chlorophenyl)diphenylmethanol and imidazole, in Clotrimazol spray 1 % was developed. The development was focused on the selection of an optimal column, composition and pH of the mobile phase, and internal standard. A Discovery ZR-PBD column (5 ?m, 150 -× 4.6 mm) and spectrophotometric detection at 210 nm were selected. The optimal mobile phase was aqueous acetonitrile 1:1 (pH 9.7). The optimal injection volume and flow-rate were 3 ?l and 1 ml min-1, respectively. On the basis of robustness tests, ibuprofen was used as the internal standard. The analysis time was less than 4.5 min.

Elicitation is one of the methods for stimulation of secondary metabolism in plant cell cultures.... more Elicitation is one of the methods for stimulation of secondary metabolism in plant cell cultures. The present study tested HgCl2 solutions (0.5-100 μM) as an elicitor of the production of coumarins in angelica cell cultures. The HgCl2 toxicity was examined by evaluating its effect on cell growth (characterized by fresh and dry biomass at the end of a two-week subculture). Cultivations were performed in the dark or in light. The content of coumarins was determined fluorometrically by sequential injection analysis. The culture growth was not adversely affected by Hg concentrations up to 50 μM; the 100 μM concentration was lethal, independently of light conditions. HgCl2 stimulated production of coumarins. In the dark, the amount of coumarins in the medium increased with increasing Hg concentrations up to 20 μM (the coumarin contents in the medium increased by 70 % compared with control) while it was not influenced in cultured cells. In light, HgCl2 enhanced accumulation of coumarins b...

Journal of Pharmaceutical and Biomedical Analysis

Journal of Food Composition and Analysis

Journal of Chromatography A

An automatic flow-based system as a front end to liquid chromatography (LC) for on-line dynamic l... more 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.

Analytical Methods

Sequential injection analysis system with sensitive chemiluminescence detection using the flow-ba... more Sequential injection analysis system with sensitive chemiluminescence detection using the flow-batch detection cell was developed for real time monitoring of kinetic profiles of antioxidant activity of phenolic substances in luminol-Fe(III)-hydrogen...

Analytical and Bioanalytical Chemistry

AbstractA fully automated method for the determination of lovastatin in dietary supplements conta... more AbstractA fully automated method for the determination of lovastatin in dietary supplements containing red yeast rice has been developed. It uses a sequential injection analysis system combined with solid-phase extraction applying highly selective molecularly imprinted polymer sorbent. A miniaturized column for on-line extraction was prepared by packing 4.5 mg of the sorbent in a 5.0 × 2.5-mm-i.d. cartridge, which was used in the flow manifold. Sequential injection analysis manifold enabled all steps of lovastatin extraction and continuous spectrophotometric detection at 240 nm. A limit of detection of 60 μg g−1, a limit of quantitation of 200 μg g−1, and a linear calibration range of 200–2000 μg g−1 were achieved. Intra-day and inter-day precision values (RSD) were ≤ 6.7% and ≤ 4.9%, respectively, and method recovery values of spiked red yeast rice extracts at 200, 1000, and 2000 μg g−1 concentration levels were 82.9, 95.2, and 87.7%. Our method was used for determination of lovastatin lactone in four dietary supplements containing red yeast rice as a natural source of lovastatin, also known as monacolin K. The extracted samples were subsequently analyzed by the reference UHPLC-MS/MS method. Statistical comparison of results (F test, t test, α = 0.05) obtained by both methods did not reveal significant difference. A substantial advantage of the new automated approach is high sample throughput thanks to the analysis time of 7.5 min, miniaturization via down-scaling the extraction column, and smaller sample and solvent consumption, as well as reduced generation of waste. Graphical abstractᅟ

Talanta, 2017

A proof of concept of a novel automatic sample cleanup approach for metal assays in troublesome m... more A proof of concept of a novel automatic sample cleanup approach for metal assays in troublesome matrixes as a front-end sample pre-treatment to inductively coupled plasma optical emission spectroscopy - ICP-OES - is herein presented. Target metals, namely, copper, lead, and cadmium were complexed in-system quantitatively using ammonium pyrrolidine dithiocarbamate (APDC) and transferred into a minute volume of toluene as extractant employing lab-in-syringe magnetic stirring-assisted dispersive liquid-liquid microextraction (LIS-MSA-DLLME). After discharge of the sample, the analytes were back-extracted into nitric acid and injected on-line into ICP-OES. To promote and expedite this process in-syringe, advantage was taken from oxidative decomposition of the chelate by potassium iodate, reported in this article for the first time. Experimental conditions for LIS-MSA-DLLME were optimized by Box-Benkhen multivariate analysis using the geometric mean of analyte recoveries as the desirabil...

Journal of Luminescence

Abstract The effect of 0.01–100 µmol L −1 Quantum Dots (QDs) with different emission wavelengths ... more Abstract The effect of 0.01–100 µmol L −1 Quantum Dots (QDs) with different emission wavelengths (520–640 nm) and different surface modifications (mercaptopropionic, mercaptoundecanoic, thioglycolic acids and mercaptoethylamine) on permanganate-induced and luminol–hydrogen peroxide chemiluminescence (CL) was studied in detail by a sequential injection technique using a spiral detection flow cell and a flow-batch detection cell operated in flow and stop-flow modes. In permanganate CL system no significant enhancement of the CL signal was observed while for the luminol–hydrogen peroxide CL substantial increase (>100% and >90% with the spiral detection cell in flow and stop-flow modes, respectively) was attained for CdTe QDs. Enhancement exceeding 120% was observed for QDs with emissions at 520, 575 and 603 nm (sizes of 2.8 nm, 3.3 nm and 3.6 nm) using the flow-batch detection cell in the stop-flow mode. Pronounced effect was noted for surface modifications while mercaptoethylamine was the most efficient in CL enhancement compared to mercaptopropionic acid the most commonly applied coating. Significant difference between results obtained in flow and flow-batch conditions based on the entire kinetics of the extremely fast CL reaction was discussed. The increase of the CL signal was always accompanied by reduced lifetime of the CL emission thus application of QDs in flow techniques should be always coupled with the study of the CL lifetime.

Analytical chemistry, Jan 10, 2017

A proof of concept study involving the online coupling of automatic dispersive liquid-liquid micr... more A proof of concept study involving the online coupling of automatic dispersive liquid-liquid microextraction (DLLME) to inductively coupled plasma optical emission spectrometry (ICP OES) with direct introduction and analysis of the organic extract is herein reported for the first time. The flow-based analyzer features a lab-in-syringe (LIS) setup with an integrated stirring system, a Meinhard nebulizer in combination with a heated single-pass spray chamber, and a rotary injection valve, used as an online interface between the microextraction system and the detection instrument. Air-segmented flow was used for delivery of a fraction of the nonwater miscible extraction phase, 12 μL of xylene, to the nebulizer. All sample preparative steps including magnetic stirring assisted DLLME were carried out inside the syringe void volume as a size-adaptable yet sealed mixing and extraction chamber. Determination of trace level concentrations of cadmium, copper, lead, and silver as model analyte...

Microchemical Journal, 2016

Abstract Trace amounts of two sulfonylurea herbicides widely used for crops protection, metsulfur... more Abstract Trace amounts of two sulfonylurea herbicides widely used for crops protection, metsulfuron methyl (MSM) and chlorsulfuron (CSF) were simultaneously determined taking into account the different kinetic photodegradation behavior of their photoproducts in alkaline medium. As the analytes are present at trace concentration levels, a preconcentration by sorption on a mini-column packed with oxidized multiwall carbon nanotubes (ox-MWCNTs) at pH 3.0 was performed. The retained analytes were removed from the ox-MWCNTs mini-column with a mixture of ACN contained 10% (v/v) of NaOH pH 12.5. A total enrichment factor of 26-fold for a 14.50 mL sample volume was obtained. The eluate was photodegraded by UV radiation during 126 s and the fluorescent spectra corresponding to the analytes photoproducts were registered overtime between 300 and 500 nm. The kinetic second order data were analyzed by unfolded-partial least squares-residual bilinearization (U-PLS/RBL) and multidimensional-partial least squares-residual bilinearization (N-PLS/RBL) algorithms. The relative error of prediction (REP %) for N-PLS/RBL was 7.73% for MSM and 6.37% for CSF. In the case of U-PLS/RBL, this statistical parameter was 7.75% for MSM and 7.23% for CSF, respectively. The limits of detection (LOD) were 0.19 μg L− 1 for MSM and 1.14 μg L− 1 for CSF using N-PLS/RBL and 0.21 μg L− 1 for MSM and 1.03 μg L− 1 for CSF when U-PLS/RBL was applied. The entire procedure was performed in an on-line integrated fully automated flow system coupled to a low mercury UV lamp (15 W, 254 nm) and a spectrofluorometer. In this manner, the preconcentration, photodegradation and detection steps were performed in a reproducible way. After optimization, the method was successfully applied to the analysis of real water samples obtained in the south part of Buenos Aires province and used for irrigation and consumption.

Analytica Chimica Acta, 2016

A novel approach to the automation technique Lab-In-Syringe, also known as In-Syringe Analysis, i... more A novel approach to the automation technique Lab-In-Syringe, also known as In-Syringe Analysis, is proposed which utilizes a secondary inlet into the syringe void, used as a size-adaptable reaction chamber, via a channel passing through the syringe piston. This innovative approach allows straightforward automation of head-space single-drop microextraction, involving accurately controlled drop formation and handling, and the possibility of on-drop analyte quantification. The syringe was used in upside-down orientation and in-syringe magnetic stirring was carried out, which allowed homogenous mixing of solutions, promotion of head-space analyte enrichment, and efficient syringe cleaning. The superior performance of the newly developed system was illustrated with the development of a sensitive method for total ammonia determination in surface waters. It is based on head-space extraction of ammonia into a single drop of bromothymol blue indicator created inside the syringe at the orifice of the syringe piston channel and on-drop sensing of the color change via fiber optics. The slope of the linear relationship between absorbance and time was used as the analytical signal. Drop formation and performance of on-drop monitoring was further studied with rhodamine B solution to give a better understanding of the system's performance. A repeatability of 6% RSD at 10 μmol L(-1) NH3, a linear range of up to 25 μmol L(-1) NH3, and a limit of detection of 1.8 μmol L(-1) NH3 were achieved. Study of interferences proved the high robustness of the method towards humic acids, high sample salinity, and the presence of detergents, thus demonstrating the method superiority compared to the state-of-the-art gas-diffusion methods. A mean analyte recovery of 101.8% was found in analyzing spiked environmental water samples.

Analytical and Bioanalytical Chemistry, 2015

A novel flow-programming setup based on the sequential injection principle is herein proposed for... more A novel flow-programming setup based on the sequential injection principle is herein proposed for on-line monitoring of temporal events in cell permeation studies. The permeation unit consists of a Franz cell with its basolateral compartment mixed under mechanical agitation and thermostated at 37 °C. The apical compartment is replaced by commercially available Transwell inserts with a precultivated cell monolayer. The transport of drug substances across epithelial cells genetically modified with the P-glycoprotein membrane transporter (MDCKII-MDR1) is monitored on-line using rhodamine 123 as a fluorescent marker. The permeation kinetics of the marker is obtained in a fully automated mode by sampling minute volumes of solution from the basolateral compartment in short intervals (10 min) up to 4 h. The effect of a P-glycoprotein transporter inhibitor, verapamil as a model drug, on the efficiency of the marker transport across the cell monolayer is thoroughly investigated. The analytical features of the proposed flow method for cell permeation studies in real time are critically compared against conventional batch-wise procedures and microfluidic devices.

Anal. Methods, 2015

The simple colour reaction between aluminum(iii) and aluminon reagent was transferred to an autom... more The simple colour reaction between aluminum(iii) and aluminon reagent was transferred to an automated sequential injection system.

Analytical and Bioanalytical Chemistry, 2015

The use of small scale renewable sorbent material for automated solid phase extraction of multi-r... more The use of small scale renewable sorbent material for automated solid phase extraction of multi-residue pharmaceuticals in environmental samples exploiting the sequential injection analysis-bead injection with direct coupling to liquid chromatography-electrospray ionization tandem mass spectrometry (SIA-BI-μSPE-LC-ESI-MS/MS) is presented to determine beta-blockers, namely atenolol, sotalol, pindolol, acebutolol, timolol, metoprolol, labetalol, carazolol, propranolol and betaxolol. These compounds yielded the same product ions, therefore were affected in terms of quantification when flow injection analysis-mass spectrometry (FIA-MS) was used. Thus, analytes and matrix present in the sample travel together into the ionization source which can seriously affect the ionization efficiency and analyte signals due to monitoring over a short time period.

Talanta, Jan 15, 2012

A non-extractive sequential injection spectrophotometric method for the determination of molybden... more A non-extractive sequential injection spectrophotometric method for the determination of molybdenum has been developed. The method is based on the reaction between the thiocyanate complex of molybdenum and the polymethine dye (2-[2-(4-dipropylamino-phenyl)-vinyl]-1,3,3-trimethyl-3H-indolium chloride) in a hydrochloric acid medium. The calibration plot in the SIA system was linear from 0.080mgL(-1) to 1.92mgL(-1) of Mo; LOD was 0.021mgL(-1). The method was applied for the determination of molybdenum in spiked drinking water and mineral water.

Microchemical Journal, 2012

A novel approach for sequential injection-dispersive liquid-liquid microextraction (SI-DLLME) has... more A novel approach for sequential injection-dispersive liquid-liquid microextraction (SI-DLLME) has been suggested. The method is based on the aspiration and mixing of a sample and all required aqueous reagents in the holding coil of an SIA system, delivering it into a conical tube and adding in a mixture of extraction solvent, auxiliary solvent and disperser solvent at high flow rate, resulting in the formation of a cloudy state and the extraction of an analyte. The mixture of extraction and auxiliary solvent is immiscible with water and has a density significantly higher than that of water; consequently, the resulting fine droplets in the mixture, which contain the extracted analyte, are self-sedimented in a short time at the bottom of conical tube. Thus, no centrifugation and no use of a microcolumn are required for separation of the extraction phase. Afterwards, the extracted analyte is aspirated and transferred to a micro-volume Z-flow cell, and the absorbance is measured. The performance of the suggested approach is demonstrated by the SI-DLLME of thiocyanate ions in the form of ion associate with dimethylindocarbocyanine reagent, followed by spectrophotometric detection. A mixture of amyl acetate (as extraction solvent), tetrachloromethane (as auxiliary solvent) and acetonitrile (as disperser solvent) was selected for the DLLME procedure. The appropriate experimental conditions for conventional DLLME and automated SI-DLLME were investigated. The analytical performance of both these procedures was compared. The absorbance of the colored extracts at wavelength 555 nm obeys Beer's law in the range of 3.13-28.2 for conventional DLLME and 0.29-5.81 mg L − 1 of SCN for SI-DLLME, and the limit of detection, calculated from a blank test based on 3 s, is 0.110 for conventional DLLME and 0.017 mg L − 1 for SI-DLLME.

Guest edited as a special report on "New Methods for Drug Analysis in Biological Samples and Othe... more Guest edited as a special report on "New Methods for Drug Analysis in Biological Samples and Other Matrixes" by Danica Agbaba and Andjelija Malenovic.