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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.

In contemporary analytical practice, the on-line CE-MS technique has established as a powerful separation and identification analytical tool. Its major instrumental aspects can be considered as solved and its routine use with specific applications to be implemented is the typical task at present. In that context, the chemical (wet, electrophoretic) part of the technique becomes very important as here the separation battle of the overall success of the developed method is fought. The review brings an overview of the electrolyte systems used in the CE part of the CE-MS technique together with a detailed insight into their pros and cons from the electrophoretist's viewpoint. Advanced electrophoretic approaches including sample stacking, ITP and use of non-aqueous solvents are also discussed. An overview of the electrolyte systems used in over 200 selected applications is given, sorted according to the analytes of interest.

Determination of pK values of weak bases and acids by CZE has already attracted big attention in current practice and proved to offer the advantage of being applicable for mixtures of analytes. The method is based on the measurement of mobility curves plotting the effective mobility vs. the pH of the background electrolyte, and following computer-assisted regression involving corrections for ionic strength and temperature. To cover the necessary range of pH for a given case, both buffering weak acids and bases are used in one set of measurements, which requires implementing computations of individual ionic strength corrections for each pH value. It is also well known that some components of frequently used background electrolytes may interact with the analytes measured, on forming associates or complexes. This obviously deteriorates the reliability of the resulting data. This contribution brings a rational approach to this problem and establishes a standard system of anionic buffers for measurements of pKs and mobilities of weak acids, where the only counter cation present (besides H(+)) is Na(+). In this way, the risk of formation of complexes or associates of analytes with counter ions is strongly reduced. Moreover, the standard system of anionic buffers is selected in such a way that it provides, for an entire set of measurements, constant and accurately known ionic strength and the operational conditions are selected so that they provide constant Joule heating. Due to these precautions only one correction for ionic strength and temperature is needed for the obtained set of experimental data. This considerably facilitates their evaluation and regression analysis as the corrections need not be implemented in the computation software. The reliability and the advantages of the proposed system are well documented by experiments, where the known problematic group of phenol derivatives was measured with high accuracy and without any notice of anomalous behaviour.

The determination of ethyl glucuronide (EtG), a marker of recent alcohol consumption, in human serum by hyphenation of capillary ITP (CITP) and CZE is reported. For CITP step, 1 x 10(-2) M hydrochloric acid adjusted with epsilon-aminocaproic acid (EACA) to pH 4.4 was used as the leading electrolyte, and 1 x 10(-2) M nicotinic acid with EACA, pH 4.4, was used as the terminating electrolyte (TE). All electrolytes contained 0.2% hydroxypropylcellulose to suppress electroosmosis. In CITP, EtG was separated from fast serum macrocomponents chloride, phosphate, lactate, and acetate. Zones of microcomponents including EtG that migrated between acetate and nicotinate were forwarded to the second capillary filled with a BGE identical with the TE. Conductivity detection was used in the CITP step. Sensitive detection in the CZE step was performed using indirect spectrophotometric detection at 254 nm. The assay is based on a 1:5 dilution of serum with deionized water and has a concentration LOD for EtG in diluted sample of 9.8 x 10(-9) M. The method was used for the determination of EtG in sera of volunteers consuming alcohol.

A method for determination of metabisulfite and hydrosulfite in poultice and decolorant by isotachophoresis was developed. Metabisulfite and hydrosulfite are ionizable oxoanions of sulfur of similar character that can easily be oxidized to sulfates. To protect the analytes from oxidation the solid samples were dissolved in a 1% (w/v) solution of formaldehyde. Hydrosulfite and metabisulfite present in the samples were transformed by the reaction with formaldehyde to stable compounds, hydroxymethanesulfinate and hydroxymethanesulfonate that were determined isotachophoretically without any pretreatment except for sample filtering and degassing. A capillary of 0.4mm i.d. and 100mm effective length made of fluorinated ethylene-propylene copolymer was filled with an electrolyte system consisting of 10 mmol L(-1) HCl+11 mmol L(-1) imidazole, 0.15% (w/v) hydroxyethylcellulose, pH 6.0 (leading electrolyte) and 5 mmol L(-1) benzoic acid+6 mmol L(-1) imidazole, pH 6.5 (terminating electrolyte). Separation was performed at a driving current of 80 microA and for detection current was decreased to 30 microA. Using contactless conductivity detection, the calibration curves in the tested concentration range up to 2.5 mmol L(-1) were linear for both metabisulfite and hydrosulfite complexes. The concentration detection limits for metabisulfite and hydrosulfite were 2.9 and 3.4 micromol L(-1), respectively. For 1 mmol L(-1) concentration, values of R.S.D. (n=6) were 2.6% for hydrosulfite and 0.8% for metabisulfite. Isotachophoretic determination took about 20 min. The elaborated isotachophoretic procedure is simple to perform, sufficiently sensitive and accurate. In addition to this, low cost of analyses makes the method an alternative procedure to methods used so far for the determination of oxoanions of sulfur.

A method has been developed for the determination of iodide in mineral water, seawater, cooking salt, serum, and urine based on hyphenation of capillary ITP and zone electrophoresis. A commercially available instrumentation for capillary ITP with column-switching system was used. ITP served for removal of chloride present in the analyzed samples in a ratio of 10(6)-10(7):1 to iodide, zone electrophoresis was used for evaluation. Isotachophoretic separation proceeded in a capillary made of fluorinated ethylene-propylene copolymer of 0.8 mm id and 90 mm total length to the bifurcation point filled with a leading electrolyte (LE) composed of 8 mM HCl + 16 mM beta-alanine (beta-Ala) + 10% PVP + 2.86 mM N(2)H(4)x2HCl, pH 3.2; and a terminating electrolyte composed of 8 mM H(3)PO(4) + 16 mM beta-Ala + 10% PVP + 5 mM N(2)H(4), pH 3.85 for all the matrices except seawater. For ITP of seawater the LE consisted of 50 mM HCl + 100 mM beta-Ala + 10% PVP + 2.86 mM N(2)H(4)x2HCl, pH 3.52. Distance of conductivity detector from the injection point and bifurcation point was 52 and 38 mm, respectively. Zone electrophoresis was performed in a capillary made of fused silica of 0.3 mm id and 160 mm total length filled with LE from isotachophoretic step. LODs reached for all matrices were 2-3x10(-8) M concentration (2.5-4 microg/L) enabled monitoring of iodide in all analyzed samples with RSD 0.4-9.3%. Estimated concentrations of iodide in individual matrices were 10(-6)-10(-8) M.

Sample stacking is a general term for methods in CE which are used for on-line concentration of diluted analytes. During the stacking process, analytes present at low concentrations in a long injected sample zone are concentrated into a short zone (stack). The stacked analytes are then separated and individual zones are detected. Thus stacking provides better separation efficiency and detection sensitivity. Many papers have been published on stacking till now, various procedures have been described, and, many names have been proposed for stacking procedures utilizing the same principles. This contribution brings an easy and unified view on stacking, describes the basic principles utilized, makes a list of recognized operational principles and brings an overview of principal current procedures. Further, it surveys selected recent practical applications ordered according to their operational principles and includes the terms, nicknames, and acronyms used for these actual stacking procedures. This contribution may help both newcomers and experts in the field of CE to orient themselves in the already quite complex topic of sample stacking.

The analysis of ethyl glucuronide (EtG), a marker of recent alcohol consumption, in serum with an optimized CZE assay is reported. The method uses a 0.1-mm id fused-silica capillary of 50 cm effective length that is coated with linear polyacrylamide, a pH 4.4 nicotinic acid/epsilon-aminocaproic acid (EACA) BGE, reversed polarity and indirect analyte detection. The assay is based on a 1:1 dilution of serum with deionized water and has LODs for EtG, lactate and acetate of 3.8 x 10(-7) M, 2.60 x 10(-6 )M and 2.18 x 10(-6 )M, respectively. Separation of EtG from endogenous macro- and microcomponents (anionic serum components of high and low concentration, respectively) and its quantification are shown to be possible for a wide range of lactate (stacker) and acetate (destacker) concentrations, macrocomponents that have an impact on the CZE behavior of EtG and that change after intake of ethanol. The assay has been successfully applied to the analysis of EtG, lactate and acetate in (i) sera of volunteers that ingested known amounts of alcohol and (ii) samples of patients that were classified (teetotalers and social drinkers vs. alcohol abusers) via analysis of carbohydrate-deficient transferrin.

Determination of impurities in ionic liquids (ILs) remains a difficult task. In this work, the hyphenation of isotachophoretic (ITP) preconcentration to zone electrophoresis (ZE) has been explored for the trace analysis of the cationic impurities Na(+), Li(+), and methylimidazolium (MI(+)) in butylmethylimidazolium (BMI(+))-based ILs. Simultaneous detection of UV-transparent and UV-absorbing impurities was ensured by a BGE composed of creatinine-acetate buffer. To induce ITP, three different strategies were evaluated: (i) Sample self-stacking ensured by the addition of ammonium acetate (NH(4)Ac) to 25-50-fold diluted IL solution (transient ITP). (ii) Complete ITP-ZE separation performed in a single capillary: ITP was realized in discontinuous electrolytes comprising an 80 mM NH(4)Ac, 40 mM acetic acid, 30 mM alpha-CD, pH 5.05, leading electrolyte (LE) and a 10 mM creatinine, 10 mM acetic acid, pH 4.9, terminating electrolyte (TE). To create the ZE stage, the ITP stack of analytes was moved back toward the capillary inlet by pressure and simultaneously the capillary was filled with the BGE. This protocol made it possible to accommodate a 2.5-times diluted IL sample. (iii) Complete counterflow ITP-ZE with continuous electrokinetic sample supply: the ITP stage was performed in a capillary filled with a 150 mM NH(4)Ac, 75 mM acetic acid, 30 mM alpha-CD, pH 5.0 LE, with 40-times diluted IL at the capillary inlet. BMI(+) from IL acts as the terminating ion. The LODs reached in this latter case were at the 10 and 1 ppb levels for MI(+) and Li(+) in diluted IL matrix, respectively.

A method for isotachophoretic determination of sweeteners of different character in candies and chewing gums was developed. A capillary of 0.8 mm ID and 90 mm effective length made of fluorinated ethylene-propylene copolymer is filled with an electrolyte system consisting of 10 mM HCl + 14 mM Tris, pH 7.7 (leading electrolyte) and 5 mM L-histidine + 5 mM Tris, pH 8.3 (terminating electrolyte). The analysis is performed at a driving current of 200 microA and for detection current is decreased to 100 microA. Boric acid is added to the aqueous sample solution to form borate complexes with substances of polyhydroxyl nature and make them migrate isotachophoretically. Using conductivity detection, the calibration curves in the tested concentration range up to 2.5 mM were linear for all components of interest: acesulfame K, saccharine, aspartame, cyclamate, sorbitol, mannitol, lactitol, and xylitol. The concentration detection limits ranged between 0.024 and 0.081 mM. Good precision of the ITP method is evidenced by favorable RSD values ranging from 0.8 to 2.8% obtained at the analyte concentration of 1.0 mM (n = 6). The analysis time was about 20 min. Simplicity, accuracy, and low cost of analyses make ITP an alternative procedure to methods used so far for the determination of ionizable sweeteners.

Accurate determination of pK(a) values is important for proper characterization of newly synthesized molecules. In this work we have used CZE for determination of pK(a) values of new compounds prepared from intermediates, 2, 3 and 4-(2-chloro-acetylamino)-phenoxyacetic acids, by substituting chloride for 2-oxo-pyrrolidine, 2-oxo-piperidine or 2-oxo-azepane. These substances are expected to have a cognition enhancing activity and free radicals scavenging effect. Measurements were performed in a polyacrylamide-coated fused-silica capillary of 0.075 mm ID using direct UV detection at 254 nm. Three electrolyte systems were used for measurements to eliminate effects of potential interactions between tested compounds and components of the BGE. In the pH range 2.7-5.4, chloride, formate, acetate and phosphate were used as BGE co-ions, and sodium, beta-alanine and epsilon-aminocaproate as counterions. Mobility standards were measured simultaneously with the tested compounds for calculations of correct electrophoretic mobilities. Several approaches for the calculation of the pK(a) values were used. The values of pK(a) were determined by standard point-to-point calculation using Henderson-Hasselbach equation. Mobility and pH data were also evaluated by using nonlinear regression. Three parameter sigmoidal function fitted the experimental data with correlation coefficients higher than 0.99. Results from CZE measurements were compared with spectrophotometric measurements performed in sodium formate buffer solutions and evaluated at wavelength where the highest absorbance difference for varying pH was recorded. The experimental pK(a) values were compared with corresponding values calculated by the SPARC online calculator. Results of all three used methods were in good correlation.

Borate buffers are common background electrolytes for analyses of anions in capillary zone electrophoresis. Usually, sodium borate at a given pH is used and this specification seems to be sufficient for a successful analysis. In this paper, we show that free migration of OH(-) may deteriorate the analysis of a typical anionic analysis of clinical samples due to uncontrolled migration of OH(-) throughout the systems of analyzed zones and may damage the stacking of anionic analytes of interest. We have proven that the use of ammonium borate may remedy the situation where the presence of ammonium may selectively stop the free migration of OH(-) ions, slow down their effective mobility and bring their safe behavior resulting in reproducible stacking of clinically important anions. Results of real analyses of human serum samples confirmed the proposed method and proved that substitution of sodium for ammonium in borate buffers offers reliable analyses of clinical samples having chloride as the bulk component. The experimental results given in this paper are supported also by computer simulation, which can not only support the positive results but also show the dynamics of the separation that is otherwise hidden to any detection possibilities.

For the determination of iodide in urine, where 80-90% of consumed iodine is excreted, a fast, simple, and sensitive method of capillary zone electrophoresis was elaborated and tested also for additional complex matrices such as human serum, cooking salt, and seawater. Several approaches were examined for the separation of iodide from other macro- and microcomponents in the tested matrices, and the best results were obtained when host-guest interaction with alpha-cyclodextrin or ion-pairing with polyethylenimine was employed. In both cases comparable resolution and sensitivity were reached. Due to the relatively high price of cyclodextrin only the method with polyethylenimine was further optimized and a simple procedure enabling the determination of iodide in untreated human urine, serum, cooking salt, and seawater was elaborated. The samples were injected for 20 s at 0.5 psi (3.45 kPa) into a fused-silica capillary (0.18 mm ID, 50 cm effective length) coated with polyacrylamide (electroosmotic flow < 2 x 10(-9) m(2)V(-1)s(-1)) and filled with the optimized background electrolyte composed of 20 mM KH(2)PO(4) and 0.7% m/v polyethylenimine. For detection, UV absorption at 200 and 230 nm was measured. Concentration limits of detection reached at 230 nm were for human urine 0.14 microM, for human serum 0.17 microM, for seawater 0.17 microM, and for cooking salt 89 nM. Relative standard deviations of iodide peak area and height in all matrices ranged within 0.93 to 4.19%.

Effects originating from the variability of the sample matrix can be efficiently eliminated when the separation conditions are selected so that compounds of like charge with high concentration referred to as macrocomponents are embodied into the system of transient isotachophoresis. For stacking and separation of anionic trace analytes in biological samples, the presence of chloride is shown to be important to balance out effects of other macrocomponents that act against isotachophoretic stacking. Having acetoacetate, malate, citrate, and some drug metabolites in untreated human serum samples, the stacking mechanism of these compounds in an electrolyte system comprising 5 mM mandelic acid and epsilon -aminocaproic acid, pH 3.8, is explained. Analytes are monitored by indirect UV-absorption detection. Attention is paid to the minimum chloride concentration required with respect to the concentration ratio of phosphate (stacker) and lactate (destacker) present in the sample so as to ensure both stacking and separation of trace analytes. Insight into the separation process is given both with computer simulations and experiments. For selected analytes, the effect of chloride concentration on quantitative evaluation, sensitivity and limit of detection is demonstrated as well. Moreover, the applicability of the mobility window between phosphate and lactate for an additional group of metabolites is sketched.

The review describes principles of procedures and techniques used in capillary zone electrophoresis for enhancement of sensitivity that are based on increasing analyte mass in its zone during the electromigration process, for which the term stacking is generally used. Attention is paid to intrinsic stacking in samples with low conductivity, transient isotachophoretic stacking applied in samples with high conductivity, and sweeping in micellar electrokinetic chromatography. Principles of these stacking schemes are explained, new procedures and instrumental arrangements are discussed, and all contributions involving stacking principles that have been published since the year 2000 are surveyed.

An information system Xemic applicable in analytical chemistry is described and its use in capillary electrophoresis for searching suitable separation conditions is demonstrated. This system is capable to provide suitable separation conditions even for analytes for which no electrophoretic experiments have been published so far. The system works with a database of components of anionic character the analyses of which have been performed, published in reviewed scientific journals, and included into a database created by an expert. Moreover, the system learned to search also in abstracts or complete scientific articles to find articles dealing with the determination of a substance in a given sample matrix. When no experiments have been published so far for a defined substance in a specific matrix, Xemic shows the separation conditions for determination of the substance regardless of the matrix. When no response can be found for the analyte of interest at all, the system Xemic works like an expert in the field and searches chemically similar substances and offers a series of substances the physicochemical properties of which are close to the followed analyte with respect to the behavior in the electric field, and shows working conditions for their analysis. Thus, the analyst puts only the order in the form of a given analyte in a given matrix and obtains a recommendation of a separation system that should enable to perform a successful separation. The system is not rigid and enables the operator to change the importance of individual attributes used in similarity search so as to obtain a broader or narrower group of similar components. With a certain probability the analyte of interest can be successfully analyzed under separation conditions that suited for the analysis of the most similar substances in the given matrix.

This contribution is aimed at providing a survey of the limitations of the peak-height technique. It is shown that the shape and the slope of calibration curves give a precise insight into the separation mechanism and can warn the analyst against improper selection of background electrolyte or sample dilution. This work investigates three typical situations where the sample contains (i) the minor analyte only, (ii) the minor analyte and a nonstacking bulk component, (iii) the minor analyte and a stacking bulk component, and various modes of measurement of the calibration curves differing in the medium used for the dilution of the original sample (water, background electrolyte, solution of the bulk component). Based on simple theoretical models, the shapes of the calibration curves are derived and elucidated for all modes, clearly demonstrating that only a few modes can provide useful results while most of them seem useless for quantitation. The knowledge of regularities affecting the character of calibration curves can be used for optimization of the analysis so that reliable results and highest attainable sensitivity can be reached. The outcome of this study brings a clear instruction how to successfully quantitate trace analytes even in samples with a complex and variable matrix*.

It is a frequent phenomenon in practice that a sample contains bulk levels of more than one coionic component that affect the stacking behavior of minor analytes and in this way also the sensitivity of the method. Here, attention is paid to stacking resulting from the presence of a macrocomponent of leading type that is deteriorated by the presence of another macrocomponent of like charge in the sample. Based on the isotachophoretic model of migration in the initial period of separation, a theoretical approach was elaborated both for strong and weak electrolytes which describes the separation process and finds the conditions that define whether transient isotachophoretic stacking of the analyte takes place or not. It is shown that the crucial parameter is the ratio of the concentrations of macrocomponents migrating in front and behind the analyte of interest. The destacking effect can also be expected when the coion of the background electrolyte is present in the sample. Rules how to cope with effects of destackers present in the sample are given. Theoretical considerations are illustrated by computer simulations and verified experimentally. Examples of antagonistic effects of macrocomponents are demonstrated for model serum samples.

The behavior of two different fractions of the electrically conducting polymer polyaniline (PANI) was studied in order to characterize them using fast, simple, and cheap methods of capillary zone electrophoresis. In contradistinction to the expectations that the particles will bear a positive charge on their surface, in the milieu of electrolytes used for electrophoresis (0.01-0.05 M buffers of pH 4-8.5), the surface was demonstrated to be slightly negatively charged, which led to a slow migration to the anode. An evident charge was given to the particles after their interaction with micelles formed from surface active components, cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS). An active electrophoretic migration and full separation of the PANI fractions was achieved by micellar electrokinetic chromatography (MEKC) with negatively charged SDS micelles. With this method, a reliable qualitative as well as quantitative analysis was performed in the concentration range of 0.1-1.6 mg/mL with a reproducibility of migration times better than 1.5%.

The techniques of the on-line combination of capillary isotachophoresis with zone electrophoresis in two coupled capillaries (ITP-CZE) and a single capillary zone electrophoresis (CZE) were used for the sensitive determination of orotic acid (OA) in human urine. The simple CZE system was successfully applied for fast and reliable analyses of urine of healthy adult volunteers (the detection limit 1.7.10(-6) M OA, the total time of analysis 6 min). However, this method failed in analyses of OA in urine of ill children due to more complex matrix of the samples. Here, the ITP preconcentration and preseparation step coupled on-line with CZE proved to serve well with an electrolyte system developed and optimized for this purpose. The maximum selectivity and resolution of OA from other sample constituents in ITP-CZE was achieved by use of an electrolyte system of very low pH 2.15 both for ITP and CZE stage. The sensitivity of detection and simplicity of OA identification were enhanced by use of an external UV scanning detector. High sensitivity of ITP-CZE combination (limit of detection 3.10(-7) M OA), low sample consumption (1 microliter), good reproducibility of migration times (inter-day RSD < 1.86%) and acceptable reproducibility of the determination of OA in urine samples (average RSD = 7.27%) make this technique suitable for routine determination of trace concentration of OA especially in urine of ill children under various pathological conditions and medication.

This review evaluates the literature on continuous free flow electrophoresis, published during the last four years. Its aim is to serve not only experts in the field but also newcomers, and, therefore, it also briefly describes the principles of the method and the techniques used, referring to fundamental papers published earlier. The actual commercial instrumentation is briefly outlined. A substantial part of this review is devoted to the optimization of the performance of this method. Finally, diverse applications of fractionations of charged species in solution, ranging from small ions to biological particles and cells, are surveyed.

On-line combination of capillary isotachophoresis and zone electrophoresis performed in two coupled capillaries (ITP-CZE) is used for the trace analysis of L-ascorbic acid in human serum, urine and stomach fluid. At the ITP stage, anionic sample components are separated into individual zones and macrocomponents are detected and driven out of the migration path. In the CZE stage, only a small segment of the sample zones containing L-ascorbic acid is analyzed. High sensitivity of this hyphenated method (limit of detection, 0.09-0.15 mg/L), low sample volume consumption (2 microL), and acceptable reproducibility of the results (relative standard deviation, 8%) in the concentration range 0.1-15 mg/L demonstrate that the method is applicable for the study of the relation between the content of L-ascorbic acid in body fluids and the state of health of a person, in which lower amounts of L-ascorbic acid than the normal levels (i.e., 5.1-15.1 mg/L in human serum and 12.5-26.8 mg/L in urine) are expected. Possible interferences of other components of the body fluids are excluded by good correlation of the results obtained by the ITP-CZE method and a routine colorimetric method.

The combination of capillary isotachophoresis and capillary zone electrophoresis may enhance greatly the performance of analytical capillary electrophoresis with respect to both separation power and the concentration sensitivity. The concentrating effects and the separation power of isotachophoresis allow the analysis of diluted samples and the elimination of interferences due to bulk components. The separation process of zone electrophoresis enables one to resolve the stack of trace analytes and detect the resulting individual zones with high sensitivity. The transition of isotachophoresis into zone electrophoresis plays the key role in the overall performance of this hyphenated technique. This article describes the dynamics of the conversion of isotachophoresis into zone electrophoretic mode and shows that the key role is played by the segments of the leading and terminating zones from the isotachophoretic stage. The magnitude of these segments directly effects the detection time as well as the separation width of the peaks of analytes. It is shown that these effects are also important in the analyses by capillary zone electrophoresis where isotachophoresis is induced by the sample itself. Finally, the paper presents a list of recommended, user-friendly, electrolyte systems which enable one to simply predict the performance of the combination isotachophoresis-zone electrophoresis.

Aracytidine (cytarabine, 1-beta-D-arabinofuranosylcytosine) is a synthetic analog of cytidine in which ribose is substituted by arabinose; it is used as a drug for the treatment of leukemia. A fast and reliable capillary electrophoretic method for the analysis of cytarabine and cytidine is described. The procedure utilizes the interactions with sodium dodecyl sulfate (SDS) micelles and borate, present in the background electrolyte, for the mobilization and selective separation of the analytes. The detection is carried out by UV absorbance at 275 nm. The method was applied both to pharmaceutical preparations and human serum. Analysis of an untreated serum requires 15 min; the detection limit is 0.8 microgram/mL and the relative standard deviation (RSD) is 5.3%.

Capillary zone electrophoresis was optimized for the separation of thiouracil, methylthiouracil and propylthiouracil. Methylthiouracil could be determined in various types of urine (human, bovine, horse), either without any pretreatment or in ethyl acetate extracts, within 15 min. For identification, the simultaneous detection at three UV wavelengths (216, 245 and 278 nm) was advantageously used while for quantification the wavelength of the absorbance maximum at 278 nm was preferred. Under optimized conditions a linear response of the detector in the concentration range 0.1-100 ppm was obtained. On analysis of untreated urine, a detection limit of 0.5 ppm was found; for urine extracts the detection limit was 0.1 ppm. Univocal peak identification, based on absorption at three wavelength, was only possible above 2 ppm. Relative standard deviation for standard solutions of methylthiouracil, diluted in the background electrolyte, was 1%; for methylthiouracil in extracts dissolved in the background electrolyte it was 4.5%, and for methylthiouracil in untreated urine, 12.7%.

A new approach is described for highly sensitive chiral analyses by capillary zone electrophoresis, based on using an on-line combination of two capillaries filled with either chiral selective or achiral background electrolytes (BGE). Thus, the BGEs are selected in such a way that the first capillary provides optimum chiral selectivity and the second one optimum detection sensitivity. Direct chiral separations of enantiomers of mandelic, m-methoxymandelic, 3-phenyllactic and 3-indolelactic acids served as a model example for testing the approach proposed. The analyses were performed in a BGE containing acetate as a coion and L-OH-proline or aspartame as a chiral selector. For high sensitive analyses, an arrangement containing on-line combined chiral and achiral media were tested in one or two capillaries coupled via a bifurcation block. A detection limit as low as 10(-18) moles was reached in the column-coupling system when the direct chiral separation was performed in the first capillary, filled with 20 mM acetate buffer, pH 4.4, containing 8 mM Cu (II) and 16 mM aspartame (L-aspartyl-L-phenylalanine methylester) and separated enantiomers were detected in the second capillary, filled with 20 mM acetate buffer, pH 3.1. The principle described is of general use in cases where the separation and detection of analytes in question require mutually different BGEs to reach the optimum selectivity and sensitivity, respectively.

A method has been developed for the determination of the coccidiocidic drug halofuginone in feedstuff concentrates which is based on the combination of capillary isotachophoresis and capillary zone electrophoresis in the column-switching mode. The high load capacity of the isotachophoretic step and high sensitivity of the zone electrophoretic step enabled analysis of up to 25 microliters of sample solution containing as little as 10(-8) M halofuginone with excellent reproducibility (R.S.D. about 1%). Attention was paid to the possibility of the existence of transient local isotachophoresis in the zone electrophoretic step, and experimental and theoretical methods of revealing zones migrating isotachophoretically in the background electrolyte were shown.

In the tops of corial papillae of the pig lip skin the authors sometimes observed besides typical sensory corpuscles also glomerular nerve endings. They are formed by one axon or they are polyaxon. The nerve fibres are richly branched in the formation. In electronogrammes a large number of axons is visible in cross sections round some of which there are more or less formed lamellous systems up to four lamellae. Between the axons there are nuclei of Schwann cells, on the surface there is a thin capsule of fibrocyte character. In non-primate mammals the typical receptor in the corium of the skin are simple corpuscles, in primates glomerular nerve endings. As concerns sensory corpuscles it is the other way round. The authors are of the opinion that the observed glomerular endings represent morphologically a transitory formation. With respect to the occurrence of lamellous complexes in the glomeruli, they can be considered as equivalent to simple sensory corpuscles with rapid adaptation.