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The nature of surface silanols is reviewed and their influence on retention of basic solutes in reversed phase chromatography is demonstrated and evaluated. The influence of the type of organic modifier and/or pH of buffer on retention of basic analytes with silica based RP columns is evaluated, and means for characterization of RP columns are discussed. Attempts are described to determine the surface silanol concentration of RP columns by chromatographic methods. Surprisingly the experimentally measured silanol concentrations with bare silica and with RP are by one order of magnitude lower than discussed in literature. At pH 7.6 values of 0.12 µmol m−2 have been measured for benzylamine with RP columns, corresponding to about 43% of the measurable silanols of plain silica. The break-through curves of amines let suggest that even at low pH values unprotonated species are present within the pores of the RP stationary phases and their interaction with the bonded alkyl groups contribute to retention.

This paper reports on the use of a polymer-based, strong anion-exchange stationary phase for rapid, selective and sensitive analysis of physiological important mono-, di- and oligosaccharides by high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD) under alkaline conditions. The adsorbent was obtained by direct nitration of 3 and 5 μm, spherical non-porous highly cross-linked, styrene-divinylbenzene copolymer (PS-DVB) beads, followed by reduction of superficially introduced nitro groups with nascent hydrogen and quaternization of the resultant amino groups with iodomethane. Extended exposure to high pressure and strong alkaline conditions did not have any untoward effect on mechanical stability and chromatographic performance. A comparison of the 3 and 5 μm beads showed, that the synthesized 3 μm highly cross-linked PS-DVB particles are the preferred phases for the separation of monosaccharides and the 5 μm particles are preferable for the separation of oligosaccharides. To demonstrate the suitability for the analysis of complex samples, the optimized and validated system was used for the determination of glucose, fructose and sucrose in apple juice and other soft drinks such as Coca Cola. Finally, analysis within a few minutes without sample pretreatment down to a lower limit of detection of 0.174–0.504 μg mL−1 at a linearity with R2>0.994 and a repooducibility higher than 98% further confirmed the efficiency of these polymeric sorbents.

Various polycarboxybetaines were synthesized using controlled radical polymerization processes followed by polymer analogous transformations. Structural variation of these exclusively aromatic or heteroaromatic systems includes distance between charges, hybridization and substitution of the ammonium moiety, and additional alkyl chains between the charges. For the first time capillary electrophoresis was used for systematic characterization of the solution properties. It was found to be a very sensitive method to detect even small structural differences and the resulting pH-dependent solution behavior. The electrophoretical mobility compared with an internal standard and the amount of its pH dependence are direct measures for the interaction of charges of polycarboxybetaines in solution. This method clearly reveals a gradual and more or less predictable content of "free" cationic charges dependent on structural and solution parameters. Results obtained coincide in a fairly good way with data from FTIR measurement and charge titration.

Die Chromatographie, die wichtigste und verbreitetste Methode der instrumentellen Analytik, ist fur Heinz Engelhardt die Methode des ausgehenden Jahrhunderts. Mit den rasanten Entwicklungen auf dem Gebiet der Massenspektrometrie und ihrer Kombination mit Flussigchromatographie und Kapillarelektrophorese sind die Weichen fur eine erfolgreiche Zukunft gestellt.

The preparation and evaluation of packed columns for CEC with porous and non-porous stationary phases with particle diameters between 1.5 μm and 5 μm is described. They are compared with respect of achievable efficiency, magnitude of EOF, dependence on buffer pH and concentration as well as on organic modifier content. No general correlation between chromatographically measured surface silanol concentration and magnitude of EOF could be found. Problems in reproducibility of retention in CEC may arise from in-column heat generation and overloading problems. The strong dependence of column efficiency on volume overloading is demonstrated. The use of peak area measurements for quantitative analysis is recommended. The application of CEC to the separation of herbicides and DNPH derivatives is demonstrated.

Capillary electrophoresis in entangled polymer solutions was applied to determine the molecular mass and polydispersity of polyelectrolytes. The separation selectivities of different polyethylene glycols as buffer additive can be correlated to their average molecular mass. A universal curve correlating the selectivity and the molecular mass could be obtained by using the instrinsic viscosity of the polyethylene glycol. The separation of poly(2-vinylpyridine) standards was compared to the separation of poly(4-vinylpyridine) standards. An indirect detection system was developed to characterize the cationic polyelectrolyte polydiallyldimethyl ammonium chloride. Various polymers with oppositely charged groups (polycarboxybetaines) were investigated with respect to structure dependence, pH dependence and molecular mass dependence of inter- and intramolecular association.

Determination of metal ions in aqueous samples using capillary electrophoresis can be accomplished with indirect UV detection. For optimal determination of alkali, alkaline earth, and transition metal ions, several electrolyte systems were studied. Detection at 214 nm was performed with a background electrolyte containing reagents with inherent absorbance in the UV range: imidazole, 4-methylbenzylamine and 4-aminopyridine. Glycolic acid and alpha-hydroxyisobutyric acid were used as complexing reagents. A mixture of 16 metal ions was successfully separated. The detection limits were between 92 ppb for Ca and 454 ppb for Cu with hydrostatic injection. All peaks were completely resolved and well separated. A separation efficiency of about 650,000 theoretical plates per meter was achieved for the Mg ion. The described methods can be used successfully in routine analysis of real samples. One of the methods was applied to an environmental water sample from the Georgian river Kasretula.

The competitive isotherms of the two enantiomers of oxazepam on two chiral stationary phases differing by the surface concentration of the chiral selector were derived from adsorption data measured with only the racemic mixture. Sample solubility problems limited the range of concentrations within which the measurements were possible. Slow racemization of oxazepam at room temperature prevented the use of any other sample composition than that of the racemic mixture. Two different approaches, the conventional binary frontal analysis method and the new frontal velocity method were applied for the determination of these competitive isotherms. Both sets of experimental data were found to fit well to the competitive-Langmuir isotherm equation. The best coefficients obtained with the two methods were close. The frontal velocity method has the advantages of a greater experimental simplicity, of being faster, and of requiring a smaller amount of material to acquire the necessary data. It may suffer, however, from the possibility of a systematic drift of the isotherm data due to cumulative errors.

ACE method has been developed for separation and determination on the active anthraquinone components physcion, chrysophanol, aloe-emodin, emodin, and rhein of the Chinese herbPolygonum multiflorum Thunb. The five anthraquinone compounds were separated to baseline with the optimum running buffer (24mm disodium hydrogen phosphate +30% (v/v) acetonitrile) and the amounts of the compounds in prepared and crude herb were quantitatively analyzed within 20 min. The effects of buffer pH and organic modifier (acetonitrile) concentration on the separation of the solutes were also investigated.

Die HPLC ist die am haufigsten verwendete chromatographische Analysenmethode nicht nur, weil die Anzahl der polaren und schwer fluchtigen Verbindungen die der Analyten ubersteigt, die der Gaschromatographie zuganglich sind, sondern weil neue Impulse aus der HPLC in die Bioanalytik gelangten. Und das, obwohl die Biochemiker anfanglich gegen stationare Phasen auf Kieselgelbasis, die Metallapparatur etc. Bedenken hatten.

In this paper, a micellar electrokinetic capillary chromatography (MEKC) method to analyze the active components of psoralen and isopsoralen in the Chinese herb Psoralea corylifolia L. was developed. It was found that the optimum separation condition for the analysis of these compounds was a buffer solution which contained phosphate, borate and sodium dodecyl sulfate (pH 9.2). Through optimization of the experimental condition, the two isomers could be baseline-separated and their contents in the methanol-extracted sample were quantitatively analyzed.

Positively charged capillaries for CE with reversed EOF have been prepared by copolymerization of trimethyl-ammoniumstyrene chloride with vinyl groups bonded covelently onto the capillary surface. The EOF was reversed up to pH values of 6 and amounted to the size achievable with uncoated fused-silica capillaries at pH 9, however in the opposite direction. By the addition of acrylamide to the polymerization reactions capillaries could be prepared reproducibly where the EOF was in the anodic direction and was zero at pH values above 7. The coating is stable up to pH of 10. Application of these capillaries for anion separations are shown.

Applications of CE separations with organic polymer capillaries are shown. Capillaries made from poly(methyl methacrylate) (PMMA) and polyether ether ketone (PEEK) show extremely good hydrolytic stabilities. Separations of sugars, amino acids and peptides could be achieved at high pH values. With a fluorescence detector it was possible to detect the analytes on-column, whereas for UV detection and with PEEK capillaries a detection window of fused silica had to be installed. With those capillaries it was possible to apply very high field strengths in the separation of inorganic cations via indirect UV detection.

Ultrafast high-performance liquid chromatographic separation of aldehyde and ketone 2,4-dinitrophenylhydrazones was carried out on reversed-phase 1.5 μm non-porous silica. Separation times of DNPH and a series of 12 aldehyde and ketone derivatives or potentially interfering compounds were less than 4 min compared to approximately 15 min using conventional columns. Formation of the formaldehyde derivative in solution was monitored using injection frequencies of 30 s for 15 min. The temperature dependence of the separation showed differences between the hydrazones of aliphatic aldehydes and those of unsaturated aldehydes.

The elution behavior of alkali and earth alkaline cations has been studied on a newly synthesized weak cationexchanger (WCX). Applying this stationary phase isocratic separation of these cations is possible. The dependence of retention on competing ion concentration is described via a simple model. The influence of crown ethers as well as organic eluent additives on selectivity and peak efficiency is demonstrated. With optimized separation such cations can be determined with detection limits of about 0.5 ppm using a conductivity detector without ion suppression.

The similarities and differences in indirect UV detection in ion-exchange chromatography (IEC) and capillary zone electrophoresis (CZE) are discussed. In IEC the UV absorption of the buffer is the limiting factor, because of the relative long detection path length of usually 10 mm. The highest signal-to-noise ratios are obtained at low buffer concentrations. As the retention time is also determined by the buffer concentration, the exchange capacity of the stationary phase additionally has to be optimized. In practice, it is optimal to work close to the cut-off of the buffer solution to achieve the highest detection sensitivity. In CZE, the UV absorption of the buffer usually does not cause any problems because of the far shorter optical path length, which is determined by the inside diameter of the capillary. Here, the optimum detection sensitivity can be achieved when working at the absorption maximum of the buffer. Optimization of buffer concentration can follow the CZE requirements, i.e., low heat generation and low electrodispersion. Indirect UV detection in CZE gives surprisingly high detection sensitivity in the ppb range. The independence of signal-to-noise ratio of optical path length derived for IEC, when commonly used eluent concentrations and molar absorptivities are applied, is not valid for CZE. It is borderline case for optical path lengths above 4 mm. For a fast understanding of the influence of all variables in indirect UV detection, a simplified mathematical model was derived. This may be applied to both IEC and CZE measurements.

Aus der Analytik sind die HPLC und ihre “jungere Schwester”, die Kapillarelektrophorese, heute nicht mehr wegzudenken. Beide Methoden stehen und fallen aber mit der Qualitat und Eignung der eingesetzten Saulen. Dem aktuellen Stand der Saulentechnologie ist diese Marktubersicht gewidmet.

Retention times in gradient liquid chromatography of synthetic polymers are often dependent on sample size. They increase with column load if the separation mechanism is governed by a solution process but decrease with increasing load if the mechanism is governed by adsorption. Since retention times independent of sample size are a prerequisite for peak identification as well as for the correct measurement of elution bands of samples with a broad distribution, measures to counteract sample-size effects deserve attention. Usually both solubility and adsorption are effective in gradient liquid chromatography of synthetic polymers. An appropriate balance of both effects is suitable for diminishing the influence of sample size on retention time of synthetic polymers. Ternary gradients allowing independent control of solubility and adsorption are promising.

The number of theoretical plates achievable in capillary electrophoresis has been proposed for the characterization of the quality of capillary coatings. It is shown that, as predicted by theory, the efficiency is independent of capillary inner diameter and increases with increasing field strength as long as dispersive effects can be neglected. On the other hand, in contrast to chromatography, there is no linear range within which the plate numbers are independent of the amount or volume of sample injected (from aqueous solutions). By optimization of the injection technique (use of dilute aqueous protein solutions, electrokinetic injection techniques, short injection times), up to 3 · 106 theoretical plates can be achieved. The plates generated by injection of similar amounts of sample from buffer solutions are lower by a factor of 20.

The stability of polyacrylamide coatings at high pH values has been tested. It could be shown that overall stability is not limited by the coating of the fused-silica surface with organo silanes or Grignard reagents. The instability of polyacrylamide capillaries could be traced back to the hydrolysis of the amide bond at pH 10. The SiOSi surface bonds are not affected at this pH by hydrolysis. The application of the sol-gel process to the preparation of stable homogeneous sublayers and a high density of olefinic groups within the capillary is described. The advantage for this method is the simple coating reaction and its independence of fused-silica surface properties.

By copolymerization of silica modified with vinyl groups and acrylic acid esters in suspension highly efficient, polymeric-encapsulated stationary-phases can be prepared. The suspending liquid has to be selected such that the monomers are at least partially adsorbed on the surface and the polymer formed does not precipitate. Under these conditions stationary phases capable of speedy mass transfer can be prepared, where the reduced plate heights are between 2 and 3. The silica surface shielding is optimized so that basic and acidic solutes elute with symmetrical peak.

In CE it is easy to optimize the elution order of enantiomeric pairs by reversal of the migration order. Several methods to achieve migration reversal for cationic as well as anionic enantiomers have been investigated. In principle three different approaches can be used. Firstly, electroosmotic flow can be reversed using different additives in the electrolyte buffer. Secondly, selecting different cyclodextrins as chiral additives can also reverse the migration order because of different separation and complexation mechanisms. Especially derivatized cyclodextrins have a great potential for this application and additionally contribute to the number of chiral selectors available in CE. In the third case, chargeable cyclodextrins offer the possibility for migration order reversal by varying the pH value.

The reversed-phase HPLC behaviour of double d -amino acid replacement sets of amphipathic and non-amphipathic helix-forming peptides consisting exclusively of leucine, lysine and alanine residues was studied on different polymer-encapsulated silica-based stationary phases. Plotting the retention times versus the position of d -amino acid substitution gives a characteristic pattern showing decreased retention times in the helical region. The retention time profile obtained using an amphipathic α-helix is caused by disturbance of the preferred binding domain of the stationary phase-bound peptide. However, the effect is similar but less pronounced using a non-amphipathic helical peptide that is unable to interact by a preferred binding site. The results demonstrate that reversed-phase HPLC data for peptide analogues provide an indication event of a non-amphipathic helical structure in peptides.

The sensitive and selective determination of polyalcohols without chromophores or fluorophores in the lower ppb-level is still an analytical task of high interest, especially in the field of environmental investigations. This paper describes a cation-exchange HPLC procedure for the separation and fluorescence detection of two quaternary ammonium compounds with polyalcoholic groups (degradation products of fabric softener) after derivatization with 9-fluorenylmethyl chloroformate (FMOC). Detailed experiments were carried out to determine optimum reaction conditions (pH, reaction time, temperature), linear range, detection limits, and kinetics of the reaction. The HPLC separation on a cation-exchange column includes a gradient program which provides complete separation from neutral compounds also reacting with FMOC and its hydrolysis products formed during the reaction in alkaline medium. High specificity for both investigated ammonium compounds with detection limits in the range of 1 ppb could be achieved. Spurenanalytik quaternarer Aminoalkohole als Abbauprodukte von Weichspulern in Abwasser Der empfindliche und spezifische Nachweis von Polyalkoholen ohne Chromophor bzw. fluoreszierende Gruppe stellt immer noch ein hochinteressantes analytisches Problem, insbesondere in der Umweltanalytik, dar. In dieser Arbeit wird eine HPLC-Methode beschrieben, die es erlaubt, quaternare Aminoalkohole nach ihrer Derivatisierung mit 9-Fluorenylmethylchlorameisensaureester (FMOC) und Trennung an einer Kationenaustauschersaule empfindlich mittels Fluoreszenzdetektion zu bestimmen. Umfangreiche Experimente wurden zur Ermittlung der optimalen Reaktionsbedingungen (pH-Wert, Reaktionszeit, Temperatur) sowie des linearen Bereichs, der Nachweisgrenze und der Reaktionskinetik durchgefuhrt. Die HPLC-Trennung an einer Kationenaustauschersaule erlaubt die Abtrennung neutraler Komponenten, die ebenfalls mit FMOC reagieren konnen. Gleichzeitig wird dabei auch das Hydrolyseprodukt des im Uberschus vorhandenen Reagenzes abgetrennt. Somit gelingt es, die quaternaren Aminoalkohole im Spurenbereich bis herab zu 1 ppb spezifisch nachzuweisen.

Copolymers from styrene and methyl methacrylate (MMA) were separated by both normal and reversedphase gradient chromatography. Both modes could be performed by sudden-transition gradients where the polymers were injected into a non-solvent whose polarity was either rather low (e.g.,n-heptane) or high (e.g., acetonitrile). Then the solvent strength of the starting eluent was rapidly increased to a given level by addition of dichloromethane. Under properly defined conditions, the sample components still remained on the column. Elution could be triggered off by the steady addition of another non-solvent whose polarity was opposite of that of the starting non-solvent. Thus, the mixture of five copolymers with MMA content ranging from 14 to 84% could be separated on a polar cyanopropyl column by injection inton-heptane and elution through acetonitrile (normal phase mode) and on a RP C18 column by injection into acetonitrile and elution throughn-heptane (reversed-phase mode), provided that in both modes about 30% dichloromethane was added to the starting non-solvent. The elution sequence in the reversed-phase mode was opposite to that in the normal-phase mode, obeying the approved polarity rules of chromatography in both cases.

Capillary electrophoretic methods with normal and reversed electroosmotic flows (EOF) and indirect UV detection were developed for the separation of fatty acids. Rapid separation of acids up to C12 was achieved via reversed EOF using 30% acetone, a cationic surfactant and 3,5-dinitrobenzoic acid as carrier electrolyte. Analysis of acids up to C18 was feasible by normal EOF with 60% acetonitrile and trinitrobenzenesulfonic acid as carrier. Also investigated was the influence of the concentration of various organic solvents on the magnitude and direction of the EOF and on the solubility of the fatty acid solutes. The reversed EOF method was applied to the analysis of acids in fat hydrolysates.

Copolymers from styrene and ethyl methacrylate have been separated according to composition byn-heptane gradients on a C18 bonded phase after injection into acetonitrile and subsequent sudden transition to a concentration of either dichloromethane or tetrahydrofuran between 30 and 50% or 20 and 50%, respectively. Acetonitrile is a polar non-solvent for the copolymers under investigation and ensures proper retention of the samples on a non-polar stationary phase. Dichloromethane and tetrahydrofuran are good solvents of moderate polarity. The addition of, e.g., 30 vol% of one of these solvents increased the dissolution power of the starting eluent but not to the extent necessary for elution. The latter was achieved by the addition ofn-heptane, which is a non-solvent for the polymers investigated. Thus, its eluting power must be understood as the consequence of its modifying effect on the polarity of the eluent mixture. The higher the content of copolymer in ethyl methacrylate the earlier it was eluted. Since acetonitrile andn-heptane are only partly miscible, phase diagrams were measured after the addition of either tetrahydrofuran or dichloromethane as a third component. Homogeneous mixtures were obtained on addition of about 30% solvent (one of both of the latter).

The variation in selectivity for aromatic hydrocarbons with mono-substituted polar groups is investigated in ternary mobile-phase systems on C18 stationary phases. The dependence of log k′ on the proportions of two modifiers was determined for the solutes within the concentration range of ternary systems obtained by mixing two binary eluents: methanol + water and tetrahydrofuran + water or acetonitrile + water and tetrahydrofuran + water. The nature of the relationships is explained in terms of molecular shape, molecular interactions between solute and extracted modifier and the ordering of solvated ligands on the stationary phase.

Capacity factor (k′) values of aromatic hydrocarbons with mono-substituted polar-groups are correlated for reversed-phase systems involving stationary phases with C18 or C4 ligands chemically bonded to silica and a binary aqueous eluent containing modifiers: methanol, acetonitrile, tetrahydrofuran, isopropanol, dioxane or dimethoxyethane. The relative retention variations of the solutes are interpreted with special consideration of their interactions with non-polar stationary phases and the molecular structure of the modifiers and solutes. Rules for retention and selectivity optimisation in RP-HPLC systems are given.

The coupling of packed column supercritical fluid chromatography with a commercial “Radioactivity Flow-Through Detector” for the sensitive and highly selective detection of radioactive nuclides (e.g.14C is described. The radioactivity flow-through detector showed no baseline shift when pressure or modifier (methanol) gradients were applied. The detector cell was pressure resistant even at high flow rates, over a period of approx. 100 hours and showed no leakage problems even at 40°C, 340 bar, 4.0 ml/min and a modifier content up to 20%.

The measurement of flow constancy and pulsation amplitudes of HPLC pump based on the photoconversion of malachite green leucocyanide is described. The irradiation time and hence the degree of conversion of the leucocyanide is correlated to flow fluctuations of piston driven HPLC pumps. It is possible to measure the amplitude of pulsations and determine the constancy of the flow rate. Most of the pumps show a flow stability better than ±1% measured as relative standard deviation of the flow rate under HPLC conditions (pressure drop 100 bar at 1 ml/min flow rate). The most expensive pump of those tested showed less than ±0.5% flow instability, however, this result was achieved by installation of a large-volume pulsation damper. The method described also allows flow rate measurements under FIA conditions where there is little or no pressure drop at the pump outlet.

Chargeable cyclodextrins (CD’s) offer new possibilities for the separation of enantiomers in capillary electrophoresis. Carboxymethylated, carboxyethylated, and succinylated β-cyclodextrin were used in these experiments in two different modes. At low pH ( pH 5), deprotonation of the carboxylic functions lead to mobility of the negatively charged chiral selectors themselves. They acted then as micellar-like systems which can be described as “moving stationary phases”. Under these conditions the separation of uncharged enantiomers was possible. Additionally the capability of these cyclodextrins as ion-pairing agents for the separation of enantiomers with positive charges has also been investigated. Employing the same cyclodextrin in the charged and the uncharged modes (at high or low pH) the migration order of the enantiomers could be reversed.

Different brands of commercially available quartz capillaries were investigated with respect to their optical and surface properties. Differences in inner diameter influence the detection sensitivity. Surface properties influence the electroosmotic flow (EOF). It is recommended to control the inner diameter and determine the EOF as a function of pH if new batches of capillaries are used. GC measurements and the dependence of retention on temperature permit one to characterize the coating procedure for non-polar coatings and to differentiate between polar and non-polar interactions. These values are in good agreement with measurements of the EOF and its dependence on pH.

Summary The use of cyclodextrin derivatives for the efficient separation of enantiomeric drugs is described. Hydroxypropylation, methylation or carboxymethylation of the cyclodextrin not only result in a better solubility of the cyclodextrin in aqueous solutions, but also favor, via additional hydrogen bonding, the stabilization of one of the cyclodextrin-analyte complexes. The influence of the background electrolyte on peak shape is also described here. Carboxymethylated cyclodextrin can be used in similar manner to uncharged cyclodextrins at low pH values (below 4). At pH values above 5, however, its charge also allows the separation of uncharged enantiomers as in a micellar-like system.

Capillary electrophoresis is a new analytical technique that has seen a great upswing in recent years, because this adaptation of electrophoresis may be automated and simple, direct quantification is possible. As in conventional electrophoresis, samples with a large range of molecular weights, from inorganic ions to biopolymers such as DNA and proteins, can be separated. Uncharged molecules can also be separated when micelle-forming detergents are added to the buffer; the distribution mechanism that then comes into play increases the separation efficiency of this micellar electrokinetic chromatography. Chiral additives such as cyclodextrins make the separation of enantiomers possible. The rapid increase in the popularity of capillary electrophoresis is reflected in instrument sales and the growing number of scientific publications dealing with the method, and it seems that the future of this technique is assured.

The application of supercritical fluid extraction (SFE) for the determination of the total fat content of meat and cheese products as an alternative to the official German solvent extraction is described. Under optimised conditions (40°C, 410 bar, 750 ml min−1), quantitative lipid extraction could be performed in only 35 min (compared to 5–6 hours by the classicial method) with an average recovery better than 95%. To determine the total fat content of a food sample, it must be acid-treated before extraction, otherwise, like the solvent extraction, the “free accessible fat” content is determined and not the “total fat” content. A further advantage of the acid treatment is that the lipids are separated from the particular sample matrix, prior to extraction, and fixed onto a filter. Extraction is, therefore, independent of the sample matrix, which makes this method of interest for many different foods and other samples.

Die Kapillarelektrophorese ist ein neues instrumentelles Analyseverfahren, das in den letzten Jahren einen starken Aufschwung erfahren hat, weil sie die Vorteile der elektrophoretischen Trennmethode mit der Moglichkeit zur Automatisierung und zu einfacher, direkter Quantifizierbarkeit verknupft. Wie mit der herkommlichen Elektrophorese lassen sich Proben uber einen weiten Molekulargewichtsbereich trennen, der von anorganischen Ionen bis hin zu Biopolymeren wie DNA und Proteinen reicht. Durch Zusatz von micellenbildenden Detergentien konnen auch ungeladene Molekule getrennt werden. Der zusatzliche Verteilungsmechanismus erhoht die Trenneffizienz dieser micellaren elektrokinetischen Chromatographie. Chirale Zusatze wie Cyclodextrine ermoglichen daruber hinaus die Trennung von Enantiomeren. Der schnelle Aufschwung der Kapillarelektrophorese spiegelt sich vor allem auf dem Geratemarkt sowie in der wachsenden Zahl der wissenschaftlichen Publikationen wider, was optimistisch fur die Zukunft dieser Methode stimmt.

Nicht ganz zufallig erscheint der folgende Uberblick uber Leistungsstand und Entwicklungsmoglichkeiten analytischer Trennmethoden im gleichen Heft wie die Jahresruckblicke uber Forschungsergebnisse in organischer, anorganischer, physikalischer und biologischer Chemie. Wie sieht der Analytiker sein Fach zu Beginn des Jahres 1993?

A new buffer system for the separation of cations with capillary electrophoresis using indirect UV-detection is described. p-Aminopyridine can be used in the wide pH-range between 3 and 10. High-speed separations of positively charged non-UV absorbing ions are possible. Separation of ions with similar mobilities can be achieved by the addition of complexation reagents. The separation of potassium and ammonium is possible either with the addition of crown ether or at high pH-values. Transition metals can be separated by adding 2-hydroxybutyric acid to the buffer.