Total monitoring of the constituents of Danshen tablet using micellar electrokinetic chromatography fingerprinting for antioxidant activity profiling

A micellar electrokinetic chromatography fingerprint coupled with quantification was developed for assessing the quality consistency of Danshen tablets, a traditional Chinese medicine, with pharmacological activities of activating blood to remove blood stasis and regulating the flow of vital energy to alleviate pain. Square optimization method was proposed to select the suitable background electrolyte. Subsequently, the index of chromatographic fingerprints F was simultaneously employed as an objective function to evaluate capillary electrophoresis conditions. After that, the method was proved to meet the fingerprint analysis criteria by evaluating stability, linearity, limit of detection, limit of quantification, precision, accuracy, and repeatability. Moreover, systematic quantified fingerprint method was used to evaluate chromatographic fingerprints of 30 batches of samples in terms of both quality and quantitation. The result indicated that the chemical compositions of samples were basically similar while their contents showed marked variation. In addition, the fingerprint–efficacy relationship was established using partial least squares model, which can serve as anti‐oxidant activity evaluation of Danshen tablets as well as a reference for the selection of active constituents. The proposed method can be applied for the holistic quality control of Danshen tablets.     

Monitoring the quality consistency of Weibizhi tablets by micellar electrokinetic chromatography fingerprints combined with multivariate statistical analyses,the simple quantified ratio fingerprint method,and the fingerprint–efficacy relationship

Micellar electrokinetic chromatography fingerprinting combined with quantification was successfully developed and applied to monitor the quality consistency of Weibizhi tablets, which is a classical compound preparation used to treat gastric ulcers. A background electrolyte composed of 57 mmol/L sodium borate, 21 mmol/L sodium dodecylsulfate and 100 mmol/L sodium hydroxide was used to separate compounds. To optimize capillary electrophoresis conditions, multivariate statistical analyses were applied. First, the most important factors influencing sample electrophoretic behavior were identified as background electrolyte concentrations. Then, a Box–Benhnken design response surface strategy using resolution index RF as an integrated response was set up to correlate factors with response. RF reflects the effective signal amount, resolution, and signal homogenization in an electropherogram, thus, it was regarded as an excellent indicator. In fingerprint assessments, simple quantified ratio fingerprint method was established for comprehensive quality discrimination of traditional Chinese medicines/herbal medicines from qualitative and quantitative perspectives, by which the quality of 27 samples from the same manufacturer were well differentiated. In addition, the fingerprint–efficacy relationship between fingerprints and antioxidant activities was established using partial least squares regression, which provided important medicinal efficacy information for quality control. The present study offered an efficient means for monitoring Weibizhi tablet quality consistency.     

Micellar electrokinetic chromatography fingerprinting combined with chemometrics as an efficient strategy for evaluating the quality consistency and predicting the antioxidant activity of Lianqiao Baidu pills

An approach combining micellar electrokinetic chromatography fingerprinting with chemometrics was developed to evaluate the quality consistency of Lianqiao Baidu pills, which are traditional Chinese patent medicines composed of 19 herbs used mainly to treat skin ulcers, common cold, rheumatism, herpes, and constipation. The triangle optimization method was employed to choose a satisfactory background electrolyte, with the information index, I , as an objective function for assessing the capillary electrophoresis conditions. Then, under the optimal conditions, the micellar electrokinetic chromatography fingerprints of 28 batches of samples were established, and five marker compounds were quantitatively determined simultaneously. A limited‐ratio quantified fingerprint method was introduced to evaluate the chromatographic fingerprints both qualitatively and quantitatively. Principle component analysis revealed that the 28 batches of samples can be clustered according to different manufacturers. Moreover, the relationship between the fingerprint and the antioxidant activity was explored by orthogonal partial least‐squares regression, which provided critical medicinal efficacy information for quality control. The present study establishes a powerful and reliable method for monitoring the quality consistency of Lianqiao Baidu pill.     

Micellar electrokinetic capillary chromatography fingerprints combined with multivariate statistical analyses to evaluate the quality consistency and predict the fingerprint–efficacy relationship of Salviae miltiorrhizae Radix et Rhizoma (Danshen)

Micellar electrokinetic capillary chromatography fingerprinting combined with quantification was successfully established and applied to evaluate the quality consistency of Danshen, which is a medicinal herb used to treat various diseases, especially coronary cerebrovascular diseases. A background electrolyte composed of 20 mmol/L sodium tetraborate, 90 mmol/L orthoboric acid, 25 mmol/L sodium phosphate monobasic dehydrate, and 65 mmol/L sodium dodecyl sulfate was used to separate compounds. To optimize micellar electrokinetic capillary chromatography conditions, a response surface strategy was set up for orthogonal experimental design. In fingerprint assessments, a systematic quantified fingerprint method was established for integrated quality assessment of Danshen samples from qualitative and quantitative perspectives, by which the quality of 30 samples was well differentiated. The principal component analysis coupled with quantitative determination of two components was applied to explain that the quality consistency of the medicinal herb was relatively good within one harvest season, but poor among harvest seasons for the Danshen samples. In addition, the fingerprint–efficacy relationship between the chemical fingerprints and antioxidant activities was investigated utilizing orthogonal projection to latent structures, which provided important medicinal efficacy information for quality control. This work offered an efficient, holistic, and powerful approach to evaluate the quality consistency of Danshen samples.     

Separation of cationic analytes by nonionic micellar electrokinetic chromatography using polyoxyethylene lauryl ether surfactants with different polyoxyethylene length

Although nonionic micellar electrokinetic chromatography is used for the separation of charged compounds that are not easily separated by capillary zone electrophoresis, the effect of the hydrophilic moiety of the nonionic surfactant has not been studied well. In this study, the separation of ultraviolet‐absorbing amino acids was studied in electrokinetic chromatography using neutral polyoxyethylene lauryl ether surfactants (Adekatol) in the separation solution. The effect of the polyethylene moiety (the number of repeating units was from 6.5 to 50) of the hydrophobic test amino acids (methionine, tryptophan, and tysorine) was studied using a 10 cm effective length capillary. The separation mechanism was based on hydrophobic as well as hydrogen bonding interactions at the micellar surface, which was made of the polyoxyethylene moiety. The length of the polyoxyethylene moiety of the surfactants was not important in nonionic micellar electrokinetic chromatography mode.     

Comparison of the migration behavior of nanoparticles based on polyethylene glycol and silica using micellar electrokinetic chromatography

Nanoparticles, spherical particles with diameters less than 100 nm, are promising theranostic devices for noninvasive diagnosis and therapy. In this study, nanoparticles composed of polyethylene glycol and silica were prepared, and their migration behavior was examined using capillary electrophoresis. The effects of the sodium dodecyl sulfate concentration in the electrolyte, the nanoparticle size, and the encapsulated molecule on the migration were examined. The addition of sodium dodecyl sulfate into the electrolyte had a significant effect on the electrophoretic mobility of polyethylene glycol nanoparticles, but a small effect on that of silica nanoparticles. As for the size effect, the mobility became a little faster for smaller nanoparticle sizes for both polyethylene glycol and silica nanoparticles. The encapsulated molecule affected the mobility of the nanoparticles through interactions between the encapsulated molecules and sodium dodecyl sulfate. We propose that the large effect of sodium dodecyl sulfate on the migration of the polyethylene glycol nanoparticles was due to the large spaces within the nanoparticles. These results indicate that nanoparticle migration is mainly determined by the nanoparticle components.     

Determination of low-aliphatic aldehydes indoors by micellar electrokinetic chromatography using sample dissolution manipulation for signal enhancement

This work describes a novel approach for the analysis of selected aldehydes (formaldehyde, acetaldehyde, propionaldehyde, and acrolein) and acetone in environmental samples using micellar electrokinetic chromatography (MEKC). The method is based on the reaction of carbonyl compounds with 3-methyl-2-benzothiazoline hydrazone (MBTH) that gives an azine intermediate with maximum absorbance at 216 nm. A systematic evaluation of sample dissolution medium was conducted as a means to enhancing sensitivity. In the best condition, samples were dissolved in 0.030 mol.L(-1) tetraborate solution. This condition presented enhancement factors in the range of 35-54 for the aldehydes under investigation, computed as the improvement of the concentration limits of detection (LODs) with reference to the sample dissolved in pure water. The running buffer was 0.020 mol.L(-1) tetraborate, pH 9.3, containing 0.050 mol.L(-1) sodium dodecyly sulfate (SDS). The overall methodology presented several advantages over established methods for aldehydes. Worthy mentioning that MBTH is available in high purity degree, dispensing laborious reagent purification procedures. A few method validation parameters were determined revealing good migration time repeatability (< 2.5% coefficient of variation, CV) and area repeatability (< 4% CV), excellent linearity (20-120 micro g/L, r > 0.995) and adequate sensitivity for environmental applications. The LODs with respect to each single aldehyde were in the range of 0.54-4.0 micro g.L(-1) and 11 micro g.L(-1) for acetone. The methodology was applied to the determination of aldehydes indoors. Samples were collected in an impinger flask containing 0.05% MBTH solution, at a flow rate of 0.80 L.min(-1), during 2.5 h, at different times during the day. The most abundant carbonyls in the samples were acetone, followed by formaldehyde and acetaldehyde, with estimate peak concentrations of 452, 5.2 and 2.2 ppbv, respectively.     

Method development and validation for the analysis of didanosine using micellar electrokinetic capillary chromatography

A selective MEKC method was developed for the analysis of didanosine in bulk samples. Successful separation of didanosine from 13 of its potential impurities, derived from the various synthetic preparation procedures, was achieved. As CZE gave poor separation selectivity, MEKC was preferable. The use of EKC allowed achievement of the separation in a significantly shorter time than conventional HPLC. An anionic long-chain surfactant, lithium dodecyl sulfate (LiDS), was used as the pseudostationary phase and sodium tetraborate buffer as the aqueous phase. In order to obtain the optimal conditions and to test the method robustness, a central composite response surface modeling experiment was performed. The optimized electrophoretic conditions include the use of an uncoated fused-silica capillary with a total length of 40 cm and an ID of 50 microm, a BGE containing 40 mM sodium tetraborate and 110 mM LiDS at pH 8.0, an applied voltage of 18.0 kV, and the capillary temperature maintained at 15 degrees C. The method was found to be robust. The parameters for validation such as linearity, precision, and sensitivity are also reported. Three commercial bulk samples were analyzed with this system.     

Characterization of the SDS-induced electroosmotic flow in micellar electrokinetic chromatography with cationic polyelectrolyte-coated capillaries

Manipulation of the EOF is essential for achieving optimal separations by MEKC. In this paper, we present an extensive investigation of the effect of common experimental conditions on the EOF observed in a capillary coated with poly(diallyldimethylammonium chloride) (PDADMA) polyelectrolyte under MEKC conditions. It was found that highly reproducible cathodal EOF is achieved approximately at or just below the conditional CMC value of SDS in the electrolytes used. At concentrations of SDS greater than the CMC the EOF is independent of pH. The impact of common organic modifiers (ACN, methanol, urea, beta-CD and nonionic surfactant) on the EOF behavior in both a PDADMA-coated capillary and a bare silica capillary is compared. The suppressing effect of organic modifiers on the EOF is much stronger for coated capillary indicating that these compounds additionally reduce the negative charge density on the capillary surface due to alteration of the surfactant coating.     

Using micellar electrokinetic chromatography for the highly efficient preconcentration and separation of gold nanoparticles

In this paper, we report the use of micellar electrokinetic chromatography (MEKC) for the highly efficient preconcentration and separation of gold nanoparticles (Au NPs). We used the reversed electrode polarity stacking mode (REPSM) of the MEKC system for the on-line enhancement and separation of the Au NPs. Several parameters had dramatic effects on the systems’ performance, including the concentration of sodium dodecylsulfate (SDS) surfactant, the presence of salts in the NP solution, the pH of the running electrolyte, and the temperature of the capillary. Under the optimized conditions [buffer: SDS (70 mM) and 3-cyclohexylamino-1-propanesulfonic acid (CAPS; 10 mM) at pH 10.0; applied voltage: 20 kV; operating temperature: 25 °C; additive: sodium dihydrogenphosphate (NaH₂PO₄, 10 mM); REPSM strategy for sample preconcentration], the number of theoretical plates for the 5.3- and 40.1-nm-diameter Au NPs were 3000 and (an ultrahigh) 2.1 × 10⁶, respectively; in addition, the detection sensitivities toward the Au NPs were enhanced ca. 20- and 380-fold, respectively, relative to those obtained using standard MEKC analysis conditions. Furthermore, monitoring the electropherograms using diode-array detection allowed us to identify and characterize the sizes of the separated NPs from their UV–vis spectra. Our findings suggest that MEKC is a highly efficient tool for both the preconcentration and separation of NPs.     

毛细管胶束电动色谱法测定复方丹参滴丸中三种水溶性成份

在胶束电动色谱模式下考察了影响原儿茶醛、丹参素和原儿茶酸分离的重要因素并优化了关键的分离条件,建立了一种简单快速的利用毛细管胶束电动色谱DAD检测器分离分析原儿茶醛、丹参素、原儿茶酸的新方法.当缓冲溶液为50 mmol/L磷酸盐缓冲液(pH 7.2)和20 mmol/L SDS,分离电压为15 kV和分离温度为25℃时,三种分析物在10 min内实现了基线分离.结果表明,所建立的分离方法的线性范围宽,检出限低,重现性好.并利用该方法测定了复方丹参滴丸中的原儿茶醛和丹参素.     

Analysis of neutral and sialylatedN-liked oligosaccharides by micellar electrokinetic capillary chromatography with addition of a divalent cation

Summary Micellar electrokinetic capillary chromatography (MECC) has been investigated as an alternative mode of analyzing oligosaccharides released from glycoproteins. The influence on the separation of experimental parameters such as the concentrations of surfactant and electrolyte and the addition of divalent cations was examined. Solubilization, of neutral oligosaccharides by micelles was demonstrated whereas for the sialylated oligosaccharides the electrophoretic mobility remained the predominant factor. The addition of Mg⁺⁺ to sodium dodecyl sulfate (SDS)solutions provided an effective means of enhancing the selectivioty of the separation through both an increase of the time window and the differential complexation of carbohydrate with this divalent cation.     

Simultaneous separation of nitrofuran antibiotics and their metabolites by using micellar electrokinetic capillary chromatography

Mixtures comprising nitrofuran antibiotics (NFA) and nitrofuran metabolites (NFM) were resolved for the first time by using MEKC. Sodium deoxycholate (SDC) was chosen as the micelle-forming surfactant. Optimization of separation conditions was achieved by using a central composite experimental design (CCD) approach. Experimental parameters such as concentration ratio of borate to phosphate in the buffer, pH of the running electrolyte and voltage were investigated. The effect of concentration of the surfactant on resolution was significant. Under optimal conditions of 80 mM SDC, pH 9.0, (20 mM borate + 20 mM phosphate) and 16 kV, the resolution between eight consecutive peak pairs ranged from 1.9 to 11.8. Due to the absence of a UV-active chromophore in the metabolites, they were derivatized with 2-nitrobenzaldehyde (2-NBA). In order to mimic a proposed extraction procedure for the analysis of both NFA and/or derivatized NFM in a sample, aqueous samples (prederivatized with 2-NBA) were extracted by using C(18) SPE cartridges. After washing with H(2)O, the cartridges were eluted with a small portion of organic solvent with weak elution characteristics to remove excess 2-NBA (hexane was chosen). Target analytes were then recovered with ACN. Excellent reproducibility of migration time (t(mig)) was achieved for all analytes using the developed MECC approach, with absolute t(mig) <1% RSD and t(mig) ratio <0.2% RSD, and peak area ratio was 4% RSD. The LOD for each compound, calculated by extrapolating to an S/N of 3, were found to be 0.19-2.0 microg/mL.     

Simultaneous determination of catecholamines and amino acids by micellar electrokinetic chromatography with laser-induced fluorescence detection

A selective and sensitive method was developed for separation and simultaneous determination of catecholamines and amino acids by MEKC with LIF. Interestingly enough, such work has been firstly performed on catecholamines derivatized with 4-chloro-7-nitro-2,1,3-benzoxadiazole and the detailed derivatization mechanism was discussed. After derivatization at 60 degrees C for 20 min, NBD-labeled catecholamines and amino acids were separated in a buffer system containing 10 mM sodium tetraborate-Na2HPO4, 20 mM SDS, and 10% v/v ACN at pH 9.75. SDS micelles were employed to improve the fluorescence intensity of catecholamine derivatives efficiently. Under optimum conditions, two catecholamines and 11 amino acids were separated in a short 13 min analysis time and the RSDs for migration time and peak area were less than 0.60 and 6.50%, respectively. The method was successfully applied for the quantification of catecholamines and amino acids in Portulaca oleracea L., human urine sample, and mixed injection sample.     

Optimization of the separation of flavonoids using solvent-modified micellar electrokinetic chromatography

In this work the separation of eighteen flavonoids was attempted using reduced-flow micellar elektrokinetic chromatography (RF-MEKC) electrolytes modified by selected solvents with differing properties: methanol (MeOH), acetonitrile (ACN) and tetrahydrofuran (THF). Structural aspects such as unsaturation of the C ring, number and position of OH groups, methylation and glycosylation as well as solvent effects and their impact on the electrophoretic behavior of flavonoids were addressed. By evaluating the electropherograms obtained from mixture-designed electrolytes and searching for changes in the critical pairs, a favorable separation condition was achieved using 20 mmol/L phosphate buffer at pH 2.5 containing 50 mmol/L sodium dodecyl sulfate (SDS), 15% ACN and 5% THF (one critical pair) in less than 12 min with 1.5% coefficient of variation (CV) for retention factor and 3% CV for peak area (n = 5). The applicability of the proposed separation condition was demonstrated by the inspection of flavonoids in herbal extracts of Neem.     

Determination of neonicotinoid insecticides in environmental samples by micellar electrokinetic chromatography using solid‐phase treatments

A sensitive and reliable method based on MEKC has been developed and validated for trace determination of neonicotinoid insecticides (thiamethoxam, acetamiprid, and imidacloprid) and the metabolite 6‐chloronicotinic acid in water and soil matrices. Optimum separation of the neonicotinoid insecticides was obtained on a 58 cm long capillary (75 μm id) using as the running electrolyte 40 mM SDS, 5 mM borate (pH 10.4), and 5% (v/v) methanol at a temperature of 25°C, a voltage of 25 kV and with hydrodynamic injection (10 s). The analysis time was less than 7 min. Prior to MEKC determination, the samples were purified and enriched by carrying out extraction‐preconcentration steps. For aqueous samples, off‐line SPE with a sorptive material such as Strata‐X (polymeric hydrophobic sorbent) and octadecylsilane (C₁₈) was carried out to clean up and preconcentrate the insecticides. However, for soil samples, matrix solid‐phase dispersion (MSPD) was applied with C₁₈ used as the dispersant. Good linearity, accuracy, and precision were obtained and the detection limits were in the range between 0.01 and 0.07 μg mL^?1 for river water and 0.17 and 0.37 μg g^?1 for soil samples. Recovery levels reached greater than 92% for all of the assayed neonicotinoids in river water samples with Strata‐X. In soil matrices, the best recoveries (63–99%) were obtained with MSPD.     

Monitoring quality consistency of Liuwei Dihuang Pill by integrating the ultraviolet spectroscopic fingerprint,a multi‐wavelength fusion fingerprint method,and antioxidant activities

Liuwei Dihuang Pill, a classical traditional Chinese medicine, has been widely used to treat kidney yin deficiency in China for hundreds of years. Little attention, however, has been paid to quality control methods for this formulation. In the present study, we aimed to establish a comprehensive and practical quality evaluation system for Liuwei Dihuang Pill. Thus, ultraviolet spectroscopic fingerprints and multi‐wavelength fusion fingerprints have been proposed for quality consistency evaluation of the popular patent. The similarity analysis of Liuwei Dihuang Pill samples was evaluated by systematic quantitative fingerprint method from qualitative and quantitative perspectives. The results showed that 26 batches of samples were classified into five grades for fusion fingerprints and three grades for ultraviolet spectroscopic fingerprints. Moreover, the fingerprint–efficacy correlation was also established and confirmed through the partial least squares model to visualize the antioxidant activity of Liuwei Dihuang Pill in vitro. In conclusion, these results indicated that integrating ultraviolet spectroscopic fingerprints and multi‐wavelength fusion fingerprints coupled with antioxidant activities provide a rapid and effective approach to monitor the quality consistency of Liuwei Dihuang Pill.     

Direct injection of seawater for the analysis of nitroaromatic explosives and their degradation products by micellar electrokinetic chromatography

Practical considerations for the injection and separation of nitroaromatic explosives in seawater sample matrices are discussed. The use of high surfactant concentrations and long electrokinetic injections allows for improved detection limits. Sensitivity was enhanced by two mechanisms, improved stacking at the detector-side of the sample plug and desorption of analyte from the capillary wall by surfactant-containing BGE from the inlet side of the sample plug. Calculated limits of detection (S/N = 3) for analytes prepared in pure seawater were 70–800 ppb with injection times varying from 5 to 100 s.