Micellar electrokinetic chromatography of charged and neutral drugs in acidic running buffers containing a zwitterionic surfactant, sulfonic acids or sodium dodecyl sulphate separation of heroin, basic by-products and adulterants

A procedure for the separation of charged and neutral solutes in acidic micellar running buffers has been developed. The procedure is based on a zwitterionic surfactant 3-N,N-dimethylmyristylammoniopropanesulfonate (MAPS) and alkylsulfonates added to the running buffer at pH 4.0. The alkylsulfonates increase the migration-time window for elution of neutral substances by increasing electro-osmotic mobility and by creating a negative micellar electrophoretic mobility. The test solution contained opiates and adulterants found in heroin seizures. Both the test solution and actual heroin seizures were successfully separated using a running buffer containing 50 mM 6-aminocaproic acid adjusted to pH 4.0 with 50 mM MAPS, 5 mM 1-heptanesulfonic acid and 10% acetonitrile. The procedure offers an alternative to micellar electrokinetic chromatographic separations based on charged surfactants in alkaline buffers.     

Separation of charged and neutral isotopic molecules by micellar electrokinetic chromatography in coated capillaries

Some unique separations are reported of pairs of deuterated and non-deuterated compounds by capillary zone electrophoresis (CZE) in coated capillaries in the absence and presence of surfactant micelles. Pyridine (pyridine-h₅) and [² H₅]pyridine (pyridine-d₅) could be separated in plain buffer (R = 1.1) and in 2% Nonidet P-40 (R = 1.5). Owing to the good separation obtained, it was possible to assess the degree of cross-contamination when “pure” isotopes were analysed. A 1:1 mixture of benzoic-h₅ and -d₅ acid was poorly separated in the absence of detergent (R = 0.39) but well separated in 50 mM sodium dodecyl sulphate (SDS) (R = 1.14). Benzyl-h₅ and -d₅ alcohol were reasonably well separated in a micellar system containing 50 mM SDS (R = 1.02) (a separation previously unreported in the literature. Benzene-h₆ and -d₆ were well separated again in presence of 50 mM SDS (R = 1.59). It appears that CZE offers a unique environment for the separation of positively and negatively charged and neutral isotope mixtures, previously reported only using RP-HPLC and GC.     

Determination of synthetic food dyes by capillary electrophoresis

A method for the determination of synthetic tar dyes used as food additives using capillary electrophoresis with photodiode-array detection was investigated. The dyes Erythrosine (R-3), Phloxine (R-104), Rose Bengal (R-105), Acid Red (R-106), Amaranth (R-2), New Coccine (R-102) and Allura Red AC (R-40) were separated on a capillary column (50 cm × 75 μm I.D.) and identified from the absorbance spectra of each peak. The electrophoresis buffer used was a mixture of 25 mM sodium phosphate buffer and 25 mM sodium borate buffer (1:1) (pH 8.0) containing 10 mM sodium dodecyl sulfate (SDS). Substitution of β-cyclodextrin for SDS in the electrolyte buffer was effective for the separation of R-2 and R-102. This modified method could be employed as an additional assay method for these two dyes.     

Separation of coumarins by micellar electrokinetic capillary chromatography

Nine coumarins were successfully separated simultaneously using micellar electrokinetic capillary chromatography with 4-hydroxybenzoic acid as an internal standard. A carrier composed of buffer solution (20 mM sodium dodecyl sulfate-15 mM sodium borate-15 mM sodium dihydrogenphosphate)-acetonitrile (24:1) was found to be the most suitable electrolyte for this separation. The analysis time (22 min) was shorter than that using high-performance liquid chromatography (47 min). Contents of coumarins in the crude drug of Angelicae Tuhou Radix could be easily determined by the proposed method.     

Determination of bioactive diterpenoids from Andrographis paniculata by micellar electrokinetic chromatography.

The present paper describes the development of a micellar electrokinetic chromatographic (MEKC) method for simultaneous determination of andrographolide, deoxyandrographolide and neoandrographolide in ethanol extracts of Andrographis paniculata. Separations were carried out in a fused-silica capillary tube with UV detection at 214 nm. Good separation was achieved using a 20 mM borate buffer, containing 20 mM sodium dodecyl sulphate and 10 mM sodium cholate, adjusted to pH 8.3 at an operating voltage of 25 kV, temperature of 35°C and a hydrodynamic injection of 5 s. The method was validated with good correlation coefficients obtained (0.9986–0.9989) while relative standard deviation (RSD) of migration time was between 1.14 and 2.42. It is concluded that this method could be used for speedy and accurate qualitative and quantitative analysis of bioactive diterpenoids in andrographis herb and its derived products.     

Electrochromatography-electrospray mass spectrometry of textile dyes

Electrochromatography with its high chromatographic performance has been coupled with electrospray mass spectrometry (MS) for the analysis of non-ionic disperse textile dyes. Electrochromatography offers an alternative to micellar electrokinetic capillary chromatography (MECC) for the analysis of uncharged compounds in conjunction with MS, since MECC generally relies on MS incompatible compounds for micelle formation. Overall, the technique of electrochromatography-MS should find application in many areas.     

Analysis of water extracts from airborne dust samples by capillary isotachophoresis

Application of capillary isotachophoresis (CITP) for the analysis of water extracts of the dust samples collected in different periods in air-filtration devices in Prague car traffic tunnels and in Parisian metro station is presented. The extracts were analyzed in cationic mode with a leading electrolyte (LE) of 10 mM KOH, 25 mM acetic acid, pH 4.4, and a terminating electrolyte (TE) of 10 mM β-alanine, adjusted to pH 4.4 with acetic acid, and in anionic mode with LE 10 mM HCl, 20 mM histidine, pH 5.8 and TE 10 mM 2-(N-morpholino)ethanesulphonic acid, pH 3.7. Extracted amounts of UV-absorbing substances, including pollen allergens and organic pollutants, the number of the found components and concentrations of some inorganic ions (e.g. Cl⁻, K⁺, Na⁺, Ca²⁺) in the dust samples were determined. It was found that the extracted amounts of anionic components and their number were much higher than those of cationic components. Significant differences have been found in the analyses of the extracts of different origin. Much more material and more components were present in the extracts of samples from the pollen-rich period than from the pollen-free period, especially in anionic CITP mode.     

Determination of impurities in a novel analogue of adenosine 5′-triphosphate by capillary electrophoresis

A capillary electrophoretic method using an uncoated capillary was developed to resolve potential impurities in FPL 67085XX, a novel phosphonate analogue of adenosine 5′-triphosphate. The effects of buffers, buffer concentration, eleunt pH and methanol were investigated. Optimum resolution of the impurities was achieved using an eluent consisting of 7% (v/v) methanol in 25 mM phosphate buffer-2 mM EDTA adjusted to pH 6.6.     

Analysis of eleven iridoid glycosides by micellar electrokinetic capillary chromatography (MECC) and screening of plant samples by partial filling (MECC)-electrospray ionisation mass spectrometry

Of ammonium, lithium and sodium salts of dodecyl sulfate studied as surfactants in the separation of iridoid glycosides by micellar electrokinetic capillary chromatography (MECC), the last one gave the best results. Eleven neutral iridoid glycosides were separated by MECC with sodium dodecyl sulfate as surfactant, and the water–micelle partition coefficients of the compounds were calculated. The separation system was coupled via a coaxial sheath flow electrospray interface to a mass spectrometer, and the partial filling technique was used in the on-line analysis. Seven plant species belonging to five genera (Plantago, Veronica, Melampyrum, Succisa and Valeriana) were screened for the iridoid glycosides by the new method that was developed. The findings confirmed those of an earlier study on five of the iridoid glycosides. Some new iridoid glycosides were found in Plantago lanceolata, Veronica spicata and V. chamaedrys.     

Capillary electrophoresis of nicotinamide—adenine dinucleotide and nicotinamide—adenine dinucleotide phosphate derivatives in coated tubular columns

HPCE was shown to be an effective and convenient method for the determination of nicotinamide—adenine dinucleotide (oxidized, NAD⁺; reduced, NADH), nicotinamide—adenine dinucleotide phosphate (oxidized, NADP; reduced, NADPH) and their synthetic derivatives. The coenzymes were easily separated among themselves and from their degradation products, which are inhibitors of dehydrogenases, in 15 min in a coated capillary. Several coenzyme derivatives such as N⁶-(2-aminoethyl)-NAD(P)⁺ and N(1)-(2-aminoethyl)-NAD(P)⁺ were separated by zone electrophoresis in uncoated or coated capillaries using 50 mM 3-(N-morpholino)propanesulphonic acid (pH 7.0) or Tris—HCl (pH 8.0) as buffer systems. Capillary zone electrophoresis and micellar electrokinetic capillary chromatography can also be used to monitor continuously coenzyme chemical modifications.     

高效液相色谱法和毛细管电泳法测定甘草制品中甘草酸的含量

分别用高效液相色谱法（ＨＰＬＣ）、毛细管区带电泳法（ＣＺＥ）、胶束电动毛细管色谱法（ＭＥＣＣ）测定了甘草制品中甘草酸的含量。对ＨＰＬＣ,ＣＺＥ,ＭＥＣＣ的分析条件作了一些选择实验,结果表明ＭＥＣＣ法与ＨＰＬＣ法分析数据接近、比较准确,而且前者比ＨＰＬＣ法分离效率高、溶剂用量少,是一种很有发展潜力的分析方法。     

Multivariate optimisation of a cyclodextrin-assisted-capillary zone electrophoretic method for the separation of torasemide and its metabolites

In this work, a rapid cyclodextrin-assisted capillary electrophoretic method is developed for the separation of the diuretic torasemide and three of its metabolites. Both fractional factorial and central composite designs were employed to optimise the separation method. The factors studied were pH, concentration of methyl-β-cyclodextrin, concentration of the background electrolyte and percentage of acetonitrile as organic modifier. Monitored response was a composite quality response (Q*) which balanced conflicting normalized responses, such as resolution and migration time. Optimal separation of the four studied compounds was achieved in less than 6.5 min, using an electrolyte of 60 mM borate buffer with no organic modifier and 25 mM methyl-β-cyclodextrin concentration adjusted to pH 8.0 at a potential of 30 kV. Detection wavelength and temperature were 197 nm and 20 °C respectively. This work means a significant improvement with regard to a previous separation method for these compounds developed in our laboratory.     

胶束溶液体系对毛细管电动色谱酸性化合物分离的影响

以阴离子表面活性剂十二烷基硫酸钠（SDS）、非离子表面活性剂吐温20（ Tween 20）及两者组成的混合胶束体系作为毛细管胶束电动色谱（MECC）的分离介 质，进行4种结构相似的酸性化合物的MECC分离研究，考察了胶束的类型、表面活 性剂的浓度、缓冲溶液的pH值及有机改性剂乙醇对分离的影响。结果表明各因素对 酸性药物的MECC分离有不同的影响规律。SDS胶束体系对溶质的保留值最大， Tween 20体系的保留值最小，二者的分离选择性正好相反，混合胶束体系的分离行 为则介于两者之间；在SDS和Tween 20体系中，表面活性剂浓度增加，溶质的保留 时间均随之递增，混合胶束体系中，总浓度一定，随Tween 20配比的增加，溶质的 保留时间先减少后增加；缓冲溶液的pH值增大，使溶质的分离效果均能变差；有机 改性剂乙醇的加入对容量因子的影响主要与溶质的疏水性有关，并对分离作用机理 进行了探讨。在SDS和Tween 20 MECC体系下，分别进行了实样测定，取得了满意的 结果。     

Capillary electrophoresis for measuring major and trace anions in thermal water and condensed-steam samples from hydrothermal springs and fumaroles

A new application of capillary electrophoresis for measuring major and trace anions in thermal water and condensed-steam samples is presented. Ten fluid samples were collected from hydrothermal springs and fumaroles located in a volcanic zone of Deception Island, Antarctica. Anion separation was achieved in less than 6 min using indirect UV detection at 254 nm with a negative power supply (−15 kV). The electrolyte consisted of 4.7 mM sodium chromate, 4.0 mM electroosmotic flow modifier (OFM) hydroxide, 10 mM 2-(N-cyclohexylamino)ethanesulfonic acid and 0.1 mM calcium gluconate (pH 9.1). Major anions (Cl⁻, SO₄², PO₄H²⁻, and CO₃H⁻) were measured using hydrostatic injection (10 cm for 30 s) at 25°C. Trace amounts of anions (F⁻, Br⁻, and NO₃⁻) were better determined by electromigration injection (4 kV, 10 s) at 15°C. Good reproducibility of the migration times (<0.72% RSD), a satisfactory linear response and accuracy as well as acceptable detection limits were successfully obtained.     

电中性物质的毛细管胶束电动色谱

在自制的高效毛细管电泳装置上,使用内径为0.05毫米,长为450毫米的熔融石英毛细管,十二烷基硫酸钠胶束溶液,254nm检测波长,进行了电中性化合物的毛细管胶束电动色谱研究。并将乙醇-水混合溶剂引入体系,成功地进行了多环芳烃的分离。考察了电场强度,SDS浓度及乙醇含量对柱效的影响。     

Simultaneous separation of the enantiomers of cizolirtine and its degradation products by capillary electrophoresis

The simultaneous enantioselective separation of (±)-cizolirtine and its impurities: (±)-N-desmethylcizolirtine, (±)-cizolirtine-N-oxide and (±)-5-(-hydroxybenzyl)-1-methylpyrazole was investigated by capillary electrophoresis. Electrokinetic chromatography with carboxymethyl-β-CD (CM-β-CD) and sulfobutyl-ether-β-CD was tried, showing good enantioseparation but poor chemical selectivity. The four racemic pairs were baseline separated, in a single run, by cyclodextrin-modified micellar electrokinetic chromatography. The migration buffer composition was: (60 mM hydroxypropyl-β-cyclodextrin–150 mM sodium dodecyl sulfate–50 mM disodium tetraborate, pH 9.2, in water)–butanol (95:5, v/v). Work was done to determine the effect of buffer components and their optimal concentration on selectivity. The method was validated with respect to enantioselectivity of cizolirtine as well as its degradation products and separation selectivity between the different components. Linearity, limit of detection, limit of quantitation and precision were also determined. This method is suitable for the enantiomeric purity determination and stability control of cizolirtine (racemic mixture or enantiomers) and its degradation products. Examples of electropherograms of (R)-cizolirtine degraded under stressed conditions are shown.     

Rapid determination of drugs in biofluids by capillary electrophoresis Measurement of antipyrine in saliva for pharmacokinetic studies

A micellar electrokinetic capillary chromatography method was developed that permitted the resolution of antipyrine from endogenous compounds and its quantitation in neat saliva in as little as 1 min. Final conditions were: SpectraPhoresis 1000, 30(23) cm × 50 μm silica capillary, 50 mM sodium phosphate pH 9.6, 50 mM SDS, 10 s hydrodynamic load, detection scanning 200–300 nm or 260 nm, run 25 kV. To overcome the effects of Joule heating the capillary was cooled to 15°C. Sensitivity was <10 μM and linearity extended to 350 μM. Comparison with an HPLC assay demonstrated that hydrodynamic injection gave a loading bias unless samples and standards were of equal viscosity. For 75 samples from five subjects the correlation of CE vs. HPLC was then r = 0.99.     

Open tubular capillary electrochromatography of underivatized amino acids using Rh(III) tetrakis(phenoxyphenyl)porphyrinate as wall modifier

The separation of 17 “common” underivatized amino acids was attempted by open tubular capillary electrochromatography (OT-CEC) in fused-silica capillaries coated with Rh(III) tetrakis(phenoxyphenyl)porphyrinate (Rh(III)TPP(m-OPh)₄OAc) using sodium phosphate and Tris–phosphate buffers as background electrolytes (BGEs). The OT-CEC separation of amino acids was compared with that obtained by capillary zone electrophoresis in bare fused-silica capillaries using the same BGEs. The amino acids were not derivatized and the UV-absorption detection was set at 200 nm. Depending on the experimental conditions at least 15 amino acids were separated. The best separations were obtained in a Rh(III)TPP(m-OPh)₄OAc-coated capillary in 50 mM Tris–100 mM phosphate buffer at pH 2.25. Separation of the critical triplet Val–Ile–Leu was always at least indicated being better at higher BGE concentrations. Regarding the sensitivity of the method, lower concentration limits of detection (LODs) in the coated capillary were obtained for Thr, Gly, Tyr, and Val; the other amino acids exhibited lower LODs in the uncoated capillary. The separation of acidic amino acids was not achieved.     

寡糖的毛细管电泳分析

多种寡糖经α－萘胺衍生化后，用硼砂作为电泳介质，实现了高效毛细管电泳分离。比较了毛细管区带电泳和胶束毛细管电动色谱分离寡糖α－萘胺衍生物的电泳行为，对影响分离度的诸因素进行了考察，选择了最佳分离条件。