毛细管电泳分离测定碘海醇及其杂质

 对新型造影试剂碘海醇及其杂质进行了分离和测 定研究。以硼酸盐为缓冲体系,使中性的多元醇类物质碘海醇及其杂质通过络合反应而带负 电,加入十六烷基三甲基溴化铵反转电渗流以加快分析速度,再加入适量异丙醇以进一步改 善分离结果。对该方法的定量线性范围和重现性进行了考察,将分离结果与用HPLC测定的结 果进行了比较。     

Impurity analysis of pharmaceuticals using capillary electromigration methods

This review deals with the determination of impurities in pharmaceuticals by electromigration methods in the capillary format. These separation methods are either based on the different effective mobility of the charged analytes (as in zone electrophoresis and isotachophoresis) or include hybrid methods such as micellar electrokinetic chromatography, microemulsion electrokinetic chromatography and electrochromatography. The pharmaceutically active compounds under consideration belong to chemotherapeutic agents, central nervous system drugs, histamine receptor drugs, cardiovascular drugs, anticancer drugs, anti-inflammatory drugs and some other drugs. The review discusses about 150 publications from the period between 1980 and 2007 with special emphasis on the recent trends and gives details about the experimental conditions applied for analyses and the obtained analytical performance parameters.     

Determination of impurities and counterions of pharmaceuticals by capillary electromigration methods

The review presents a survey of recent applications of high‐performance capillary electromigration methods—capillary zone electrophoresis, nonaqueous capillary electrophoresis, capillary isotachophoresis, micellar electrokinetic chromatography, microemulsion electrokinetic chromatography and capillary electrochromatography—for the determination of impurities of pharmaceuticals, including chiral impurities, for the period 2007–2013. In addition, due to the missing evaluation of the determination of counterions of pharmaceuticals by capillary electromigration methods in the last 20 years, the publications dealing with this topic since 1995 are included in this review. General aspects of both these types of applications of capillary electromigration methods in pharmaceutical analysis are discussed, and detailed experimental conditions used for determination of various chemical impurities and counterions of many particular drugs are described.     

Development and validation of a capillary zone electrophoretic method for the determination of bisphosphonate and phosphonate impurities in clodronate

Capillary zone electrophoresis with direct UV detection at low wavelength and reversed polarity was applied for the separation and quantitation of bisphosphonate and phosphonate impurities in clodronate bulk material. Polyacrylamide-coated capillaries were used to reduce the interactions between the analytes and the electric double layer of the capillary, and to minimize electroosmotic flow. Study was made of the major factors affecting the separation, i.e., pH and ionic strength of the electrolyte solution and various instrumental parameters. The developed method provided reproducible separations of clodronate and related impurities (between-day precision of migration times: RSD < 2.3%, 275 runs). Acceptable validation results in the impurity quantitation range of 0.5-7.5 microg ml(-1) (corresponding to 0.1-1.5% of clodronate working concentration) were obtained in specificity, within-day and between-day precision, accuracy and linearity.     

An initial assessment of the use of gradient elution in microemulsion and micellar liquid chromatography

Novel microemulsion and micellar HPLC separations have been achieved using gradient elution and columns packed with reverse phase material. Initial attempts at gradient microemulsion liquid chromatography proved impossible on use of a microemulsion successfully used in capillary electrophoresis. Optimisation of the microemulsion composition allowed the generation of stable microemulsions to achieve separations in HPLC. The novel use of organic-solvent micellar chromatography in gradient elution mode was shown to give efficient separations. A range of efficient separations of pharmaceuticals and related impurities were obtained. Acidic, basic, and neutral solutes were resolved covering a wide range of water solubilities and polarities. Elution times were in the order of 4-15 minutes. Separations were briefly compared to those accomplished with a micellar HPLC system. It is proposed that gradient elution in both microemulsion and micellar HPLC can be regarded as a highly successful means of achieving resolution of complex mixtures and should be considered for routine analysis and further investigation.     

Electrophoretic and gas-chromatographic analysis of an Afobazol pharmaceutical preparation

Procedures for determining 5-ethoxy-2-[2-(morpholino)ethylthio]benzimidazole dihydrochloride, an active component of the Afobazol medicinal preparation, and its potential impurities, 5-ethoxybenzimidazol-2-thione and N-(2-chloroethyl)morpholine hydrochloride by capillary zone electrophoresis in the range 2.0 × 10^?5 to 2.0 × 10^?3 M and ligand-exchange capillary electrophoresis in the range 1.0 × 10^?5 to 5.0 × 10^?3 M are developed. The optimum conditions for the separation and determination of these analytes using a quartz capillary tube are found. The reliability of the results obtained by capillary electrophoresis was confirmed by gas chromatography with a mass-selective detector.     

Large-volume stacking in capillary electrophoresis using a methanol run buffer

Highly sensitive nonaqueous capillary electrophoresis of weakly acidic organic compounds has been performed using methanol as the run buffer solvent. Methanol provided appropriate suppression of the electroosmotic flow and an increase in the electrophoretic mobilities of anionic solutes compared to water. These two effects allowed large-volume stacking using the electroosmotic flow pump (LVSEP) to be achieved for larger anions using a bare fused-silica capillary under an electric field of reverse polarity, whereas only fast-moving small anions were previously known to be suitable for LVSEP in aqueous media. A field-enhanced sample injection of an additional amount of analytes during the solvent plug removal further enhanced the limits of detection to below the nanomolar range with conventional UV absorption detection. Under optimum conditions, excellent linear responses and reproducibility in the migration times together with the corrected peak areas for ten analytes were obtained in the concentration range of 10-100 nM.     

Potential of microemulsion electrokinetic chromatography for the separation of priority endocrine disrupting compounds

This work examines the potential of microemulsion electrokinetic chromatography for the separation of several priority endocrine disrupting compounds (EDCs). The optimised microemulsion system comprised 25 mM phosphate buffer pH 2, 80 mM octane, 900 mM butanol, 200 mM sodium dodecyl sulphate and was further modified with 20% propanol. The use of a low pH buffer resulted in the suppression of electroosmotic flow within the capillary. Reversal of the conventional electrode polarity resulted in faster migration of hydrophobic compounds. Test analytes included the octylphenol, nonylphenol and nonylphenol diethoxylate, which are breakdown products of the alkylphenolic detergents. The synthetic oestrogens diethylstilbestrol and ethynyloestradiol were also included in the separation along with the plastic monomer bisphenol-A. Test analytes were selected due to their reported presence in environmental samples namely industrial and domestic wastewater treatment effluents and sludges. Using the optimised method a separation of six EDCs was achieved within 15 min. The optimised method was then applied to the analysis of a spiked wastewater influent sample with UV detection of all six compounds at 214 nm.     

Use of various β‐cyclodextrin derivatives as chiral selectors for the enantiomeric separation of ofloxacin and its five related substances by capillary electrophoresis

A capillary electrophoretic method for the enantioseparation of ofloxacin and its five related substances (potential impurities, indicated as impurities B–F) was developed using β‐cyclodextrin derivatives as chiral selectors. To our knowledge, there are no previous studies about using capillary electrophoresis for the separation of impurities B–D. Six β‐cyclodextrin derivatives including cationic (piperidine‐ and cyclohexylamine‐), neutral (dimethyl‐ and hydroxypropyl‐), and anionic (carboxymethyl‐ and sulfated‐) β‐cyclodextrin derivatives were tested and operational parameters such as buffer pH and concentration of β‐cyclodextrin derivatives were investigated. The best resolutions were all obtained with anionic β‐cyclodextrin derivatives: ofloxacin, impurities C–F could be best resolved with carboxymethyl‐β‐cyclodextrin at satisfactory resolutions of 8.27, 9.98, 5.92, 8.49 and 6.78, respectively, while for impurity B, a particularly impressive resolution value, up to 21.38, was observed using sulfated‐β‐cyclodextrin. The enhancement of enantioseparation observed for the tested analytes using anionic β‐cyclodextrin derivatives might be due to some favorable interaction between selectors and analytes. Given the fact that the selection of chiral selector depends on the structures of analytes, with the help of structural similarities and differences of the analytes, the structure–separation relationship was further discussed.     

New possibilities of micellar electrokinetic chromatography and microemulsion electrokinetic chromatography in the determination of catechols and catecholamines in natural samples

New possibilities were revealed and evaluative characteristics were obtained for different versions of capillary electrophoresis with UV detection, namely, micellar electrokinetic chromatography with normal and reversed polarity and microemulsion electrokinetic chromatography, used for determining catechols and catecholamines in green and black tea and in urine.     

Trace determination of arsenic species by capillary electrophoresis with direct UV detection using sensitivity enhancement by counter- or co-electroosmotic flow stacking and a high-sensitivity cell

Stacking techniques used independently and also with a high-sensitivity cell (HSC) were employed to optimise sensitivity and detection limits in the direct photometric detection of the following eight arsenic species by capillary zone electrophoresis (CZE): arsenite, arsenate, monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), 4-hydroxy-3-nitrophenylarsonic acid (Roxarsone), p-aminophenylarsonic acid (p-ASA), 4-nitrophenylarsonic acid (4-NPAA), and phenylarsonic acid (PAA) (target analytes). The stacking mechanisms, optimised stacking and separation conditions, and concentration sensitivity enhancement factors were discussed and compared for (i) normal stacking mode (NSM, sometimes also referred to as field-amplified stacking) in an uncoated fused-silica capillary in the counter-electroosmotic flow (EOF) mode, (ii) large-volume sample stacking (LVSS) with polarity switching, and (iii) the less often applied stacking method of co-EOF NSM stacking with EOF reversal using a poly(diallydimethylammonium chloride) (PDDAC)-coated capillary. The optimal injection volumes were 7.4, 60 and 17.2% of the total capillary volume, for the above three methods, respectively. LVSS with polarity switching gave the lowest limit of detection (LOD). The use of the HSC further reduced the LOD of each target analytes by a factor of 5-8 times. By combining LVSS and HSC, LODs of the target analytes could be reduced by a factor of 218-311, to 5.61, 9.15, 11.1, and 17.1 microg/L for As(III), DMA, MMA, and As(V), respectively. The method was demonstrated to be applicable to the determination of the target analytes in tap water and lake water, with recoveries in the range of 89.4-103.3%.     

Nonaqueous capillary electrophoresis with laser-induced fluorescence detection: a case study of comparison with aqueous media

A novel method based on separation by nonaqueous capillary electrophoresis (NACE) combined with laser-induced fluorescence (LIF) detection was developed and compared with classic aqueous modes of electrophoresis in terms of resolution of solutes of interest and sensitivity of the fluorescence detection. Catecholamines derivatized with 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) were chosen as test analytes for their subtle fluorescence properties. In aqueous systems, capillary zone electrophoresis (CZE) was not suitable for the analysis of test analytes due to complete fluorescence quenching of NBD-labeled catecholamines in neat aqueous buffer. The addition of micelles or microemulsion droplets into aqueous running buffer can dramatically improve the fluorescence response, and the enhancement seems to be comparable for micellar electrokinetic chromatography (MEKC) and microemulsion electrokinetic chromatography (MEEKC). As another alternative, NACE separation was advantageous when performing the analysis under the optimum separation condition of 20 mM sodium tetraborate, 20 mM sodium dodecyl sulfate (SDS), 0.1% (v/v) glacial acetic acid, 20% (v/v) acetonitrile (ACN) in methanol medium after derivatization in ACN/dimethyl sulfoxide (DMSO) (3:2, v/v) mixed aprotic solvents containing 20 mM ammonium acetate. Compared with derivatization and separation in aqueous media, NACE-LIF procedure was proved to be superior, providing high sensitivity and short migration time. Under respective optimum conditions, the NACE procedure offered the best fluorescence response with 5-24 folds enhancement for catecholamines compared to aqueous procedures. In addition, the mechanisms of derivatization and separation in nonaqueous media were elucidated in detail.     

Ultrasound-assisted emulsification microextraction for the determination of ephedrines in human urine by capillary electrophoresis with direct injection. Comparison with dispersive liquid-liquid microextraction

Ultrasound-assisted emulsification microextraction and dispersive liquid-liquid microextraction were compared for extraction of ephedrine, norephedrine, and pseudoephedrine from human urine samples prior to their determination by capillary electrophoresis. Formation of a microemulsion of the organic extract with an aqueous solution (at pH 3.2) containing 10% methanol facilitated the direct injection of the final extract into the capillary. Influential parameters affecting extraction efficiency were systematically studied and optimized. In order to enhance the sensitivity further, field-amplified sample injection was applied. Under optimum extraction and stacking conditions, enrichment factors of up to 140 and 1750 as compared to conventional capillary zone electrophoresis were obtained resulting in limits of detection of 12-33 μg/L and 1.0-2.8 μg/L with dispersive liquid-liquid microextraction and ultrasound-assisted emulsification microextraction when combined with field-amplified sample injection. Calibration graphs showed good linearity for urine samples by both methods with coefficients of determination higher than 0.9973 and percent relative standard deviations of the analyses in the range of 3.4-8.2% for (n = 5). The results showed that the use of ultrasound to assist microextraction provided higher extraction efficiencies than disperser solvents, regarding the hydrophilic nature of the investigated analytes.     

A 50% n-octylmethyl, 50% diphenyl-polysiloxane as stationary phase with unique selectivity for gas chromatography

An n-octylmethyl, diphenyl-polysiloxane called SOP-50-Octyl was prepared by a condensation reaction of bis(dimethylamino) n-octylmethylsilane with diphenylsilanediol. The resulting copolymer was a gum with high molecular weight and was obtained with a yield of 80%. 1H and 29Si NMR spectroscopy revealed that the copolymer was a 52% octylmethyl, 48% diphenyl-polysiloxane with random microstructure. Small cyclic impurities could be almost quantitatively removed via a purification step. SOP-50-Octyl was used as stationary phase for the preparation of wall coated open tubular fused silica capillary columns for gas-liquid chromatography. The capillary columns exhibited high separation efficiency and high inertness. The stationary phase offered a unique selectivity due to its unique composition. The Rohrschneider-McReynolds constants indicated a low overall polarity in spite of the high phenyl content, as the polarity was distinctly decreased by the octyl substituent. Furthermore, the octyl substituent was responsible for a high column bleed, reducing the maximum allowable operating temperature to 280 degrees C. The elution temperatures of apolar compounds were increased due to increased interaction of the octyl substituent with the analytes. Some applications with volatile and semi-volatile organic compounds illustrate that SOP-50-Octyl is an excellent choice for confirmational analyses.     

Determination of Low-Molecular-Mass Phenolic and Non-Phenolic Lignin Degradation Compounds in Wood Digestion Solutions by Capillary Electrophoresis

 Different capillary electrophoretic techniques were investigated and compared for the separation of low-molecular-mass phenolic and neutral lignin degradation compounds. Simple capillary zone electrophoresis (CZE) was not suited for this problem. Switching to micellar electrokinetic capillary chromatography (MEKC) by adding micelle-forming reagents to the carrier electrolyte enhanced the separation performance considerably. Alternatively, microemulsion electrokinetic chromatography (MEEKC) was investigated. This is a CE technique in which analytes interact with moving oil droplets present in a microemulsion buffer. Using the optimized carrier electrolyte systems and a 60 cm×50 μm I.D. bubble cell capillary it was possible to analyse solutions of different wood digestion procedures and to investigate differences in lignin degradation products during use of different kinds of wood (eucalyptus, beech, scotch pine and acacia). Received August 25, 1999. Revision April 13, 2000     

Optimisation by experimental design of a capillary electrophoretic method for the separation of several inhibitors of angiotensin-converting enzyme using alkylsulphonates

A statistical experimental design was used to optimise a capillary electrophoretic separation method for eight inhibitors of the angiotensin-converting enzyme: enalapril, lisinopril, quinapril, fosinopril, perindopril, ramipril, benazepril, and cilazapril. Because a free solution capillary electrophoresis system did not achieve a complete separation of these eight compounds in one run, the usefulness of alkylsulphonates as ion-pairing agents was investigated. After preliminary investigations to determine the experimental domain and the most important factors, a three-level full-factorial design was applied to study the impact of the pH and the molarity of the ion-pairing agent on the separation. Improved separations were obtained suggesting a favourable effect of ion-pairing interactions between analytes and the additive; however, it remained impossible to separate them all in one run. A combination of two systems was still necessary for the selective identification of these structurally-related substances.     

毛细管电泳法分离四环素及其杂质

用毛细管电泳方法分离四环素和它的主要杂质４－差向四环素，脱水四环素，４－差向脱水四环素和２－乙酰基－２－脱酰胺四环素，相对次要的杂质氯四环素和脱甲四环素也能被分 离。     

Determination of mercaptopurine and its four metabolites by large-volume sample stacking with polarity switching in capillary electrophoresis

This study describes approaches for stacking a large volume of sample solutions containing a mixture of mercaptopurine monohydrate, 6-methylmercaptopurine, thioguanine, thioguanosine, and thioxanthine in capillary electrophoresis (CE). After filling the run buffer (60 mM borate buffer, pH 8.5), a large sample volume was loaded by hydrodynamic injection (2.5 psi, 99.9 s), followed by the removal of the large plug of sample matrix from the capillary using polarity switching (-15 kV). Monitoring the current and reversing the polarity when 95% of current recovered, the separation of anionic analytes was performed in a run buffer < 20 kV. Around 44- to 90-fold improvement of sensitivity for five analytes was achieved by large-volume stacking with polarity switching when compared with CE without stacking. This method was feasible for determination of the analytes spiked in plasma. Removing most of electrolytes from plasma is a key step for performing large-volume sample stacking. Solid-phase extraction was used for pretreatment of biological samples. To our knowledge, this study is one of few applications showing the possibilities of this stacking procedure to analyze biological samples by large-volume sample stacking with polarity switching (LVSSPS) in CE.     

毛细管电泳法分离四环素及其杂质

用毛细管电泳方法分离四环素和它的主要杂质４－差向四环素，脱水四环素，４－差向脱水四环素和２－乙酰基－２－脱酰胺四环素，相对次要的杂质氯四环素和脱甲四环素也能被分离。并系统研究了缓冲液ｐＨ，缓冲液浓度以及毛细管温度和电压对分离的影响。紫外检测波长是２７０ｎｍ，测定的相对标准偏差为１．９％。所得结果与ＨＰＬＣ方法进行了比较     

Di-n-amyl L-tartrate-boric acid complex chiral selector in situ synthesis and its application in chiral nonaqueous capillary electrophoresis

A chiral selector, di-n-amyl L-tartrate-boric acid complex, was in situ synthesized by the reaction of di-n-amyl L-tartrate with boric acid in a nonaqueous background electrolyte (BGE) using methanol as the medium. And a new method of chiral nonaqueous capillary electrophoresis (NACE) was developed with the complex as the chiral selector. It has been demonstrated that the chiral selector is suitable for the enantioseparation of some β-blockers and β-agonists in NACE. Some chiral analytes that could not be resolved in aqueous microemulsion electrokinetic chromatography (MEEKC) with the same chiral selector obtained baseline resolutions in the NACE system. The enantioseparation mechanism was considered to be ion-pair principle and the nonaqueous system was more favorable for the ion-pair formation which is quite useful for the chiral recognition. The addition of a proper concentration of triethylamine into the BGE to control the apparent pH (pH*) enhanced the enantiomeric discrimination. In order to achieve a good enantioseparation, the effects of di-n-amyl L-tartrate and boric acid concentration, triethylamine concentration, applied voltage, as well as capillary length were investigated. Under the optimum conditions, all of the tested chiral analytes including six β-blockers and five β-agonists were baseline resolved.