Electromembrane extraction - capillary zone electrophoresis for the quantitative determination of ß-lactam antibiotics in milk samples.

Three penicillin-based ß-lactam antibiotics (benzylpenicillin, amoxicillin, and ampicillin) were extracted by electromembrane extraction (EME) and determined in the resulting extracts by capillary zone electrophoresis (CZE) with UV-Vis detection. The EME was optimized for the simultaneous clean-up of complex samples and preconcentration of the three antibiotics and employed 1-octanol as the organic phase interface (impregnated in the pores of a hollow fiber), acidified donor solution (pH 3), and phosphate buffer (pH 5.6) as the acceptor solution. The EMEs were carried out for 20 min at 300 V and constant stirring (750 rpm) of the donor solution. At the optimized EME-CZE conditions, the sensitivity of the analytical method was sufficient for the determination of the three ß-lactam antibiotics in undiluted cow's milk at concentrations below the EU maximum residue limits (4 µg/L) in foodstuffs. The method was simple, rapid, and convenient and offered extraction recoveries of 13.5 - 87.3 %, enrichment factors of 23.6 - 152.8, repeatability (RSD values) better than 7.6 %, linear analytical response in the 1 - 100 µg/L (3 - 100 µg/L for benzylpenicillin) concentration range with correlation coefficients ≥ 0.9997, and limits of detection from 0.2 to 1.2 µg/L. The proposed analytical concept was used for the rapid control of milk quality (i.e. assessment of excessive use of antibiotics in dairy animals), moreover, it was further extended to the trace determination of ß-lactam antibiotics in other complex samples, such as in wastewater.

Micro-electromembrane extraction through volatile free liquid membrane for the determination of ß-lactam antibiotics in biological and environmental samples.

Micro-electromembrane extraction (µ-EME) was presented for the selective extraction of four main ß-lactam antibiotics (penicillin, phenoxypenicillin, ampicillin, and amoxicillin) from complex samples. A volatile solvent (ethyl acetate or chloroform) was sandwiched between a plug of the complex sample and another plug of an aqueous acceptor solution in a transparent polymeric tube and formed the so-called free liquid membrane (FLM). The use of the FLM eliminated the evaporation of the solvent and enabled the µ-EME of the antibiotics, which was carried out by the application of DC voltage to the terminal aqueous solutions. The drugs in the complex sample were selectively transferred through the FLM to the acceptor solution, which was directly used for their determination by micellar electrokinetic chromatography with ultraviolet detection (MEKC-UV). The µ-EME was characterized by sub-µA electric currents, high elimination of matrix components, high stability of operational solutions, and suitability for extracting undiluted complex samples. The µ-EME/MEKC-UV method yielded good analytical repeatability (RSDs of peak areas ≤5%), extraction recoveries (40-84%), accuracy (92-105%) and linearity over one and a half order of magnitude (R2 ≥ 0.9998), and was applied to the determination of the four ß-lactam antibiotics in human serum and waste water at clinically and environmentally relevant concentration levels. Further improvement in the method sensitivity was achieved by changing the µ-EME tube geometry (conical shape) and increasing the complex sample volume (100 µL). The analytes were enriched by factors of 7.6-11.5, the limits of detection dropped down to less than 18 ng/mL, and the modified µ-EME/MEKC-UV method enabled the trace determination of ß-lactam antibiotics in complex samples.

Volatile free liquid membranes for electromembrane extraction.

Volatile solvents are excellent extraction media for liquid-liquid extractions. However, their use in supported liquid membranes (SLMs) is limited by their evaporation from SLM and thus poor SLM stability and they have never been considered truly useful for electromembrane extraction (EME). In this contribution, volatile solvents were systematically investigated as liquid membranes for EME and their extraction characteristics were comprehensively examined for the first time. A short plug of a water immiscible volatile solvent (a free liquid membrane (FLM)) was sandwiched between two aqueous plugs (donor and acceptor solutions) in a narrow-bore polymeric tubing. Evaporation of the volatile FLM was thus completely avoided and excellent stability of the phase interface was ensured. Suitability of volatile FLMs for EMEs was justified by µ-EMEs of nortriptyline, haloperidol, loperamide and papaverine as model non-polar basic drugs. Extraction performance of µ-EME through ethyl acetate was comparable or better to that through standard non-volatile EME solvents and a high extraction selectivity was achieved for nortriptyline and haloperidol extracted through chloroform. µ-EMEs through the volatile FLMs were characterized by high extraction recoveries (62%-99% for standards and 40-89% for body fluids), low electric currents (10-1380 nA), no susceptibility to matrix ions and suitability for pretreatment of raw body fluids (human urine and serum). Resulting extracts were analysed by capillary electrophoresis with ultraviolet detection (CE/UV). Repeatability of the µ-EME-CE/UV method was excellent with intra-day and inter-day RSD values 0.8-3.2% and 1.8-4.6%, respectively. Further experiments demonstrated additional advantages of volatile FLMs by nearly exhaustive µ-EMEs of atenolol as the polar basic drug with no need for FLM modification by ionic carriers. The presented comprehensive examination of volatile solvents has broadened the range of liquid membranes suitable for EME and it is believed that this proof-of-concept study will stimulate further interest in a deeper investigation of volatile phase interfaces in EME.

Two-phase micro-electromembrane extraction with a floating drop free liquid membrane for the determination of basic drugs in complex samples.

A two-phase micro-electromembrane extraction (µ-EME) using a floating drop of an organic solvent was presented for rapid and efficient pretreatment of complex biological samples. The µ-EME system consisted of a glass vial containing aqueous sample (donor solution) and a small drop of a water-immiscible organic solvent (4-nitrocumene), which was floating on the surface of the aqueous solution in form of a free liquid membrane (FLM). The vial geometry and the optimized volume ratios of the donor and the FLM ensured a stable position of the FLM in the center of the vial during µ-EME, and one electrode of a d.c. power supply was inserted directly into the FLM while the other electrode was placed into the aqueous sample. The active surface area of the floating drop FLM contacting the sample was considerably larger in comparison to formerly reported µ-EME formats employing FLMs and resulted in a faster and a more efficient transfer of target analytes from the sample to the FLM. Four basic drugs (nortriptyline, papaverine, loperamide, and haloperidol) were selected as model analytes and were extracted from physiological solution, human urine, and dried blood spot samples. At the optimized µ-EME conditions (250 V, 15 min, 300 rpm, acidic donor) and the optimized ratio of the sample to the FLM volume (500:14 µL), extraction recoveries between 49 and 100% and enrichment factors up to 35.7 were achieved. Quantitative analyses of the basic drugs in the resulting FLMs (diluted with methanol) were performed by capillary electrophoresis with ultraviolet detection and demonstrated excellent repeatability (RSD ≤ 4.9%) and linearity (r2 ≥ 0.9997), and low limits of detection (5-28 ng/mL) of the method.

Two-phase micro-electromembrane extraction across free liquid membrane for determination of acidic drugs in complex samples.

A dynamic two-phase micro-electromembrane extraction (µ-EME) using electrically induced transfer of charged analytes directly into free liquid membrane (FLM) is proposed as a novel technique for improving enrichment capabilities of µ-EME. The presented set-up employs aqueous sample as donor solution and water immiscible organic solvent (1-octanol) as FLM, which form the two-phase µ-EME system for efficient extraction of model acidic drugs (ibuprofen, ketoprofen, naproxen and diclofenac) from standard solutions, human urine, human serum and wastewater samples. The FLM eliminates migration of matrix components from the complex samples and simultaneously it acts as an acceptor solution for selective trapping and enrichment of the analyte ions. Electrodes are immersed directly into the sample and the FLM and replenishment of analyte ions at the sample/FLM phase interface is accomplished by stirring the sample solution using a conventional laboratory stirrer. At optimized two-phase µ-EME conditions (100 V, 15 min, 1000 rpm) and optimized volume ratio of sample to FLM (480:16 µL), extraction recoveries of 60-97% and enrichment factors up to 29.1 were achieved. Determination of the acidic drugs in resulting FLMs was achieved by capillary electrophoresis with ultraviolet detection with good linearity (r2 ≥ 0.9998) and low limits of detection (4-20 ng/mL).

Recent progress of sample stacking in capillary electrophoresis (2016-2018).

Electrophoretic sample stacking comprises a group of capillary electrophoretic techniques where trace analytes from the sample are concentrated into a short zone (stack). This paper is a continuation of our previous reviews on the topic and brings a survey of more than 120 papers published approximately since the second quarter of 2016 till the first quarter of 2018. It is organized according to the particular stacking principles and includes chapters on concentration adjustment (Kohlrausch) stacking, on stacking techniques based on pH changes, on stacking in electrokinetic chromatography and on other stacking techniques. Where available, explicit information is given about the procedure, electrolyte(s) used, detector employed and sensitivity reached. Not reviewed are papers on transient isotachophoresis which are covered by another review in this issue.

Direct Analysis of Free Aqueous and Organic Operational Solutions as a Tool for Understanding Fundamental Principles of Electromembrane Extraction.

Aqueous and organic phases in microelectromembrane extraction (µ-EME) were formed as adjacent plugs of free immiscible solutions in narrow-bore polymeric tubing, and each single phase was recovered and analyzed after µ-EME. A three-phase µ-EME setup was employed for investigation of time-dependent distribution of model basic drugs among aqueous and organic phases. Exact concentrations of nortriptyline and papaverine in donor solution, acceptor solution, and free liquid membrane (FLM) were determined by capillary electrophoresis with ultraviolet detection (CE-UV). At typical µ-EME conditions (acceptor, 1 µL of 25 mM HCl; FLM, 1 µL of 4-nitrocumene; donor, 1 µL of basic drugs in 10 mM HCl; and extraction potential, 250 V), experimentally determined distribution of the drugs confirmed the kinetic model for electrically mediated transfer of charged analytes. Rapid depletion of the drugs from donor solution (0-180 s) and rapid saturation of FLM with the drugs (15-60 s) were followed by gradual transfer of the drugs across FLM and gradual liberation into acceptor solution (30-240 s). Exhaustive transfer of the drugs from donor to acceptor solution was obtained in 15 min. A good correlation between the analytes' distribution and µ-EME electric currents was observed; the currents increased during drugs' transfer across FLM, were concentration dependent, and demonstrated transfer of the drugs across FLM in their ionized forms. Proper understanding of the fundamental principles of µ-EME transfer enabled further fine-tuning of the µ-EME process. Transfer of the drugs across FLM was controlled by optimizing the composition and pH of acceptor solution, and quantitative fractionation of nortriptyline into aqueous acceptor (96%) and of papaverine into organic FLM (95%) was achieved based on their different pKa values. µ-EME fractionation of the two drugs was compatible with raw human urine and excellent repeatability (RSD ≤ 3.9%), linearity (r2 ≥ 0.9989), and limits of detection (≤ 0.15 µg/mL) were achieved for µ-EME-CE-UV of the drugs in standard solutions and urine samples.

Injections from sub-µL sample volumes in commercial capillary electrophoresis.

A simple sample injection procedure compatible with commercial capillary electrophoresis (CE) instrumentation was developed, which enables handling sample volumes as little as 250nL for analytical applications where sample volume availability is of concern. Single-use micro-sampling inserts were prepared by thermal modification of polypropylene micropipette tips and the inserts were accommodated in standard CE vials in CE autosampler carousel. To ensure direct contact of separation capillary injection end with sample solution and to avoid possible damage to the capillary, a soft compression spring was placed at the bottom of the vial underneath the micro-sampling insert. Injections from sub-µL samples were carried out in conventional as well as in short-end injection mode, were compatible with standard i.d./o.d. (25-100µm/365µm) fused silica capillaries and with various background electrolyte solutions and detection modes. Excellent repeatability of replicate injections from 250nL to 3µL was achieved based on RSD values of quantitative analytical measures (peak heights ≤2.4% and peak areas ≤3.7%) for CE-UV-vis, CE-ESI-MS and CE-contactless conductivity detection of model basic drugs. The achieved RSD values were comparable with those for replicate injections of the drugs from standard CE vials. The reported concept of injections from micro-sampling inserts was further demonstrated useful in evaluation of micro-electromembrane extraction (µ-EME) of model basic drugs. Sub-µL volumes of operational solutions resulted in reduced lengths of µ-EME phases and improved extraction recoveries (66-91%) were achieved.

Application of a macrocyclic compound, bambus[6]uril, in tailor-made liquid membranes for highly selective electromembrane extractions of inorganic anions.

A tailor-made liquid membrane consisting of a resistive organic solvent (nitrobenzene, NB) and a highly selective non-ionic macrocyclic compound (bambus[6]uril, BU6) was employed for electromembrane extraction (EME) of inorganic anions. BU6 facilitates strong host-guest interactions of its internal cavity with selected inorganic anions only and its presence in the liquid membrane ensured excellent selectivity of the EME process. EME transfers were directly related to association constants between BU6 and inorganic anions and nearly absolute selectivity was achieved for EMEs of iodide, bromide and perchlorate. Major inorganic anions (chloride, nitrate, sulphate and carbonate), which exhibit low interactions with BU6 cavity, were efficiently eliminated from the EME transfer. No interferences were observed for EMEs of target analytes from samples containing up to 100.000-fold higher concentrations of the major anions. Addition of species-specific macrocyclic modifiers to free and supported liquid membranes might thus open new directions in fine-tuning of EME selectivity. At optimized EME conditions (polypropylene hollow fiber impregnated with NB + 3% (w/w) BU6, extraction voltage 25 V, extraction time 15 min, deionized water as acceptor solution) perchlorate was selectively extracted from tap water at concentrations below the guideline value recommended by United States Environmental Protection Agency. Excellent selectivity of the tailor-made liquid membrane was further demonstrated by EME of bromide from sea water.

Recent progress of sample stacking in capillary electrophoresis (2014-2016).

The term "sample stacking" comprises a relatively broad spectrum of techniques that already form an almost inherent part of the methodology of CZE. Their principles are different but the effect is the same: concentration of a diluted analyte into a narrow zone and considerable increase of the method sensitivity. This review brings a survey of papers on electrophoretic sample stacking published approximately since the second quarter of 2014 till the first quarter of 2016. It is organized according to the principles of the stacking methods and includes chapters aimed at the concentration adjustment principle (Kohlrausch stacking), techniques based on pH changes, micellar methods, and other stacking techniques. Not reviewed are papers on transient ITP that are covered by another review in this issue.

Rapid determination of meldonium in urine samples by capillary electrophoresis with capacitively coupled contactless conductivity detection.

Capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D) was employed for fast determination of meldonium (MEL) in urine samples. Background electrolyte consisting of 2M acetic acid (pH 2.3) was used for separation of MEL from cationic compounds present in urine samples and the overall analysis time was less than 4min per sample. Direct injection of urine samples was possible after 1:9 dilution with deionized water. This simple sample pretreatment was sufficient to eliminate possible matrix effects on CE performance and allowed for precise and sensitive determination of free MEL in urine. Excellent linearity (r2≥0.9998) was obtained for two concentration ranges, 0.02-4µgmL-1 and 2-200µgmL-1, by simply changing injection time from 10 to 2s without the need for additional dilution of urine samples. Limit of detection was 0.015µgmL-1 and average recoveries from urine samples spiked at 0.02-123.5µgmL-1 MEL ranged from 97.6-99.9%. Repeatability of migration times and peak areas was better than 0.35% and 4.2% for intraday and 0.95% and 4.7% for interday measurements, respectively. The above reported data proved good applicability of the CE-C4D method to determination of various MEL concentrations in urine samples and good long-term performance of the analytical system. The method might be particularly useful in analyses of large batches of samples for initial testing of MEL-positive vs. MEL-negative urine samples.

Additional considerations on electrolysis in electromembrane extraction.

Optimized acceptor solutions, which eliminate electrolytically induced variations in their pH values, have been shown to improve electromembrane extraction (EME) performance. Acceptor solutions containing 500 mM formic acid (pH 1.97) ensured stable EME process for three basic drugs extracted at 50 V across 1-ethyl-2-nitrobenzene and constant extraction recoveries (66-89%) were achieved for 40-80 min EMEs. Back-extraction of analytes into donor solutions has been eliminated by application of optimized acceptor solutions, moreover, saturation of acceptor solutions with analytes had no additional effect on their back-extraction; the presence of up to 300-fold excess of analytes in optimized acceptor solutions led to slightly reduced but stable enrichment of analytes over the entire extraction time. Stable EME performance has been also achieved for extractions into 100mM HCl, note however, that seriously compromised performance of subsequent capillary electrophoretic analyses has been observed due to high conductivities of resulting acceptor solutions. Electrolytically produced H(+) and OH(-) ions have mostly remained in corresponding operating solutions, have determined their final pH values and have not been subjects of EME transfers across selective phase interfaces as was experimentally verified by pH measurements of anolytes and catholytes at various EME times.

Quantitative aspects of electrolysis in electromembrane extractions of acidic and basic analytes.

Electrolysis is omnipresent in all electrochemical processes including electromembrane extraction (EME). The effects of electrolysis on quantitative aspects of EME were comprehensively evaluated for a set of acidic (substituted phenols) and basic (basic drugs) analytes. EMEs were carried out across supported liquid membranes formed by 1-ethyl-2-nitrobenzene at standard EME conditions, i.e., acidic analytes were extracted from alkaline into alkaline solutions and basic analytes were extracted from acidic into acidic solutions. Electric potential applied across the EME systems was 50 V and extraction recoveries of analytes as well as pH values of donor and acceptor solutions were determined after each EME. It has been proven that electrolysis plays a more significant role than has ever been thought before in EME. Electrolytically produced H(+) and OH(-) ions had a significant effect on pH values of acceptor solutions and variations of up to 8.5 pH units were obtained at standard EME conditions. pH values of donor solutions were affected only negligibly due to their significantly higher volumes. The observed variations in pH values of acceptor solutions had fatal consequences on quantitative EME results of weak and medium strong acidic/basic analytes. A direct relation was observed between the decrease in extraction recoveries of the analytes, their pKa values and the acceptor solution pH values. Acceptor solutions consisting of high concentrations of weak bases or acids were thus proposed as suitable EME operational solutions since they efficiently eliminated the electrolytically induced pH variations, offered stable EME performances and were easily compatible with subsequent analytical methods.

Contemporary sample stacking in analytical electrophoresis.

This contribution is a methodological review of the publications about the topic from the last 2 years. Therefore, it is primarily organized according to the methods and procedures used in surveyed papers and the origin and type of sample and specification of analytes form the secondary structure. The introductory part about navigation in the architecture of stacking brings a brief characterization of the various stacking methods, with the description of mutual links to each other and important differences among them. The main body of the article brings a survey of publications organized according to main principles of stacking and then according to the origin and type of the sample. Provided that the paper cited gave explicitly the relevant data, information about the BGE(s) used, procedure, detector employed, and reached LOD and/or concentration effect is given. The papers where the procedure used is a combination of diverse fragments and parts of various stacking techniques are mentioned in a special section on combined techniques. The concluding remarks in the final part of the review evaluate present state of art and the trends of sample stacking in CE.

Fine-tuning of electromembrane extraction selectivity using 18-crown-6 ethers as supported liquid membrane modifiers.

Selectivity of electromembrane extractions (EMEs) was fine-tuned by modifications of supported liquid membrane (SLM) composition using additions of various 18-crown-6 ethers into 1-ethyl-2-nitrobenzene. Gradually increased transfer of K(+) , the cation that perfectly fits the cavity of 18-crown-6 ethers, was observed for EMEs across SLMs modified with increasing concentrations of 18-crown-6 ethers. A SLM containing 1% w/v of dibenzo-18-crown-6 in 1-ethyl-2-nitrobenzene exhibited excellent selectivity for EMEs of K(+) . The established host-guest interactions between crown ether cavities in the SLM and potassium ions in donor solution ensured their almost exhaustive transfer into acceptor solution (extraction recovery ∼92%) within 30 min of EME at 50 V. Other inorganic cations were not transferred across the SLM (Ca(2+) and Mg(2+) ) or were transferred negligibly (NH4 (+) , Na(+) ; extraction recovery < 2%) and had only subtle effect on EMEs of K(+) . The high selectivity of the tailor-made SLM holds a great promise for future applications in EMEs since the range of similar selective modifiers is very broad and may be applied in various fields of analytical chemistry.

Effects of selected operational parameters on efficacy and selectivity of electromembrane extraction. Chlorophenols as model analytes.

Effects of organic solvent type, pH value, and composition of donor/acceptor solution on the efficacy of electromembrane extraction (EME) were examined. For the first time, a comprehensive quantitative study, based also on measurements of electric charge passed through the EME system, was carried out, which demonstrates that apart from the pH value, also the nature of counter-ions in donor and acceptor solution plays a significant role in the electrically induced transfer of charged analytes across supported liquid membranes (SLMs). The EME transfer of model analytes correlated well with electrophoretic mobilities of inorganic cations, which were added to acceptor solutions during their alkalization with alkali metal hydroxides, and were highest for counter-cations with highest mobilities. Up to a 53-fold improvement of extraction efficiency was achieved for EMEs using optimized composition of donor (alkalized with KOH to pH 7) and acceptor (10 mM CsOH, pH 12) solutions. Six chlorophenols (CPs) were selected as model analytes due to the wide range of pH values that are required for their ionization and due to their high environmental relevance; quantitative measurements were carried out by CE with UV detection. Extraction recoveries of the six CPs ranged between 14 and 25% for 5 min EMEs at 150 V and 750 rpm across SLMs impregnated with 1-ethyl-2-nitrobenzene. Calibration curves were strictly linear (r(2) ≥ 0.999) in 0.01-10 µg/mL range, repeatability values of peak areas were between 0.7 and 5.6% and LODs for standard solutions and environmental samples were better than 5 ng/mL.

Contemporary sample stacking in analytical electrophoresis.

Sample stacking is a term denoting a multifarious class of methods and their names that are used daily in CE for online concentration of diluted samples to enhance separation efficiency and sensitivity of analyses. The essence of these methods is that analytes present at low concentrations in a large injected sample zone are concentrated into a short and sharp zone (stack) in the separation capillary. Then the stacked analytes are separated and detected. Regardless of the diversity of the stacking electromigration methods, one can distinguish four main principles that form the bases of nearly all of them: (i) Kohlrausch adjustment of concentrations, (ii) pH step, (iii) micellar methods, and (iv) transient ITP. This contribution is a continuation of our previous reviews on the topic and brings an overview of papers published during 2010-2012 and relevant to the mentioned principles (except the last one which is covered by another review in this issue).

Electromembrane extraction using stabilized constant d.c. electric current--a simple tool for improvement of extraction performance.

This contribution presents an experimental approach for improvement of analytical performance of electromembrane extraction (EME), which is based on the use of stabilized constant d.c. electric current. Extractions were performed using a high voltage power supply, which provided stabilized constant d.c. current down to 1µA and facilitated current-controlled transfer of ions of interest from a donor solution through a supported liquid membrane (SLM) into an acceptor solution. Repeatability of the extraction process has significantly improved for EME at constant electric current compared to EME at constant voltage. The improved repeatability of the extraction process was demonstrated on EME-capillary electrophoresis (EME-CE) analyses of selected basic drugs and amino acids in standard solutions and in human urine and serum samples. RSD values of peak areas of the analytes for EME-CE analyses were about two-fold better for EME at constant electric current (2.8-8.9%) compared to EME at constant voltage (3.6-17.8%). Other analytical parameters of the EME-CE methods, such as limits of detection, linear ranges and correlation coefficients were not statistically different for the two EME modes. Moreover, EME at constant electric current did not suffer from SLM instabilities frequently observed for EME at constant voltage.

Electric field-enhanced transport across phase boundaries and membranes and its potential use in sample pretreatment for bioanalysis.

Separation techniques, such as electrodialysis, electroextraction, electro-membrane extraction and extraction across phase interfaces, are reviewed and discussed as methods for sample cleanup and preconcentration. This survey clearly shows that electromigration of ionic species across phase interfaces, especially across supported liquid membranes, may be very selective and is strongly dependent on the chemical composition of these interfaces. Thus, electric field-enhanced transport across chemically tailored liquid membranes may open new perspectives in preparative analytical chemistry. This review offers comprehensive survey of related literature and discussion of the topic, which may stimulate interest of experts and practitioners in bioanalysis.

Standard systems for measurement of pK values and ionic mobilities: 2. Univalent weak bases.

This paper contributes to the methodology of measuring pK values and ionic mobilities by capillary zone electrophoresis by introducing the principle of constant ionic strength and minimum interaction of analytes with counterionic components and presenting a standard system of cationic buffers for measurements of weak bases. The system is designed so that all buffers comprise the same concentration of Cl(-) present as the only counter anion. This minimizes problems caused by interactions between the counterion and the analytes which may otherwise bring biased values of obtained effective mobilities. Further, the buffer system provides constant and accurately known ionic strength for an entire set of measurements. When additionally all measurements are performed with constant Joule heating, one correction for ionic strength and temperature is then needed for the obtained set of experimental data. This considerably facilitates their evaluation and regression analysis as the corrections for ionic strength and Joule heating need not be implemented in the computation software and may be applied only once to the final regression results. An experimental example of the proposed methodology is presented and the reliability and the advantages of the proposed system are shown, where the known problematic groups of amines and pyridine were measured with high accuracy and without any notice of anomalous behavior.