Application of capillary electrophoresis for organic acid analysis in herbal studies

Separation of short and medium-chain fatty acids using capillary electrophoresis with indirect photometric detection: Part I: Identification of fatty acids in rat feces

Short and medium-chain fatty acids (SMCFAs) are known as essential metabolites found in gut microbiota that function as modulators in the development and progression of many inflammatory conditions as well as in the regulation of cell metabolism. Currently, there are few simple and low-cost analytical methods available for the determination of SMCFA. This report focuses on SMCFA analysis utilizing CE with indirect photometric detection (CE-IPD). A ribonucleotide electrolyte, 5'-adenosine mono-phosphate (5'-AMP), is investigated as an IPD reagent due to its high molar absorptivity and dynamic reserve compatible with separation and detection of SMCFA. The operating parameters like the composition of organic solvent, millimolar concentrations of the complexing agent (alpha-cyclodextrin), 5'-AMP and non-absorbing electrolyte (boric acid), as well as the applied voltage, are optimized for resolution, efficiency, and signal-to-noise ratio. A baseline resolution of all nine SMCFAs is achieved in less than 15 min. Additionally, the developed CE-IPD method shows promising potential to identifying SMCFA in rat fecal supernatant. The presented analytical assay is simple, economical, and has considerably good repeatability. The intraday and interday RSD of less than 1 and 2% for relative migration time, as well as less than 14 and 15% for peak area, respectively, were obtained for SMCFA in fecal solution.

Development of a micellar electrokinetic capillary chromatography method for the determination of four naphthalenediols in cosmetics and a comparison with a HPLC method

A micellar electrokinetic capillary chromatography (MEKC) method with ultraviolet visible (UV) detection was used for the determination of 1,7-naphthalenediol, 2,3-naphthalenediol, 1,5-naphthalenediol, and 2,7-naphthalenediol in cosmetics. The current method for their determination in various cosmetics is high-performance liquid chromatography (HPLC). Separation conditions affecting the MEKC method were optimized as 20 mM Na₂ B₄ O₇ -50mM SDS, pH 9.8, with 22 kV applied voltage and UV detection at 230 nm. Under optimal conditions, electrophoretic analysis was completed in less than 6 min, with limit of detection (LOD) of 0.070-0.19 μg/mL and limit of quantitation (LOQ) of 0.23-0.63 μg/mL. A good linear relationship (r² > 0.99) was obtained at the range of 0.75-20 μg/mL. Recoveries for the four naphthalenediols in lotion, loose powder, and sun cream are between 91.2-107.2% with relative standard deviation (RSD) less than 4.04%. The method has been successfully applied to the determination of the four naphthalenediols in different kinds of cosmetics. A comparison with HPLC-UV method was also carried out according to the National Standards of the People's Republic of China. The results obtained by MEKC and HPLC methods are comparable, but the proposed MEKC method can help us obtain a much shorter detection time and low cost.

Simultaneous Separation of Eight Lignans in Forsythia suspensa by β-Cyclodextrin-Modified Capillary Zone Electrophoresis

The aim of the study was to develop an alternative capillary zone electrophoresis (CZE) for simultaneous determination of phillyrin (1), phillygenin (2), epipinoresinol-4-O-β-glucoside (3), pinoresinol-4-O-β-glucoside (4), lariciresinol (5), pinoresinol (6), isolariciresinol (7) and vladinol D (8) in Forsythia suspensa. The structural types of lignans 1-8 could be attributed to bisepoxylignans (1-4 and 6), monoepoxylignans (5 and 8) and cyclolignan (7). The major difficulties in the CZE separation of 1-8 could be summarization as the simultaneous presence of free lignans (1, 2 and 5-8) and lignan glucosides (3 and 4) and simultaneous occurrence of two pairs of isomers (3 and 4 as well as 5 and 7). Without the addition of β-CD and methanol, the resolution of these analytes was quite poor. However, in this study, compounds 1-8 were excellently separated from each other within 15 min under optimized conditions with a borax running buffer (40 mM borax, pH 10.30) containing 2 mM β-CD and 5% methanol (v/v) at the voltage of 20 kV, temperature of 35 °C and detection wavelength of 234 nm. Validation of the method included tests of linearity, precision, repeatability, stability and accuracy. In addition, the method offered inherent advantages such as lower analytical cost, no need of specific columns and use of small amounts of organic solvents and reagents. Finally, this green and economic CZE was successfully applied for the determination of these bioactive components 1-8 in F. suspensa fruits and its commercial extracts.

Phenolic characterization and antimicrobial activity of folk medicinal plant extracts for their applications in olive production

Phytophthora spp is important in plant pathology due to the importance of the diseases it causes. In olive trees, severe damages are caused by the disease known as "dry branch" occasioned by Phytophthora nicotianae, P. citrophthora and P. palmivora. Much effort has been made to find efficient methods of control, with a low negative impact on environment. In this regard, treatment with plant extracts is a valid strategy. The aims of the present study are (i) to determine the polyphenol composition of extracts of Thymus vulgaris, Origanum vulgare, Matricaria recutita, and Larrea divaricata by CZE, (ii) correlate the analytical composition of these extracts with the inhibition on the mycelial growth, and (iii) determine the individual antimicrobial activity of the most active ingredients. A simple methodology was developed for the determination of catechin, naringenin, cinnamic acid, syringic acid, chlorogenic acid, apigenin, vanillic acid, luteolin, quercetin, and caffeic acid in plant extracts by CZE. The extraction of phenolic compounds in extract was performed by a miniaturized solid phase extraction using a home-made minicolumn packed with suitable filtering material (C18 , 50 mg). The optimized analyses conditions were: 30 mM boric acid buffer, pH 9.50; capillary, 57 cm full length, 50 cm effective length, 75 μm id, hydrodynamic injection 30 mbar, 2 s; 25 kV; 25°C, detection by UV absorbance at 290 nm. Sample results suggest that phenolic composition seems to have a great influence on inhibition of pathogens. The highest inhibitions of mycelial growth were observed for cinnamic acid and naringenin.

Field enhancement sample stacking for analysis of organic acids in traditional Chinese medicine by capillary electrophoresis

A technique known as field enhancement sample stacking (FESS) and capillary electrophoresis (CE) separation has been developed to analyze and detect organic acids in the three traditional Chinese medicines (such as Portulaca oleracea L., Crataegus pinnatifida and Aloe vera L.). In FESS, a reverse electrode polarity-stacking mode (REPSM) was applied as on-line preconcentration strategy. Under the optimized condition, the baseline separation of eight organic acids (linolenic acid, lauric acid, p-coumaric acid, ascorbic acid, benzoic acid, caffeic acid, succinic acid and fumaric acid) could be achieved within 20 min. Validation parameters of this method (such as detection limits, linearity and precision) were also evaluated. The detection limits ranged from 0.4 to 60 ng/mL. The results indicated that the proposed method was effective for the separation of mixtures of organic acids. Satisfactory recoveries were also obtained in the analysis of these organic acids in the above traditional Chinese medicine samples.

Application of ionic liquids based microwave-assisted extraction of three alkaloids N-nornuciferine, O-nornuciferine, and nuciferine from lotus leaf

The application of ionic liquids based microwave-assisted extraction (ILMAE) was successfully developed for extracting three alkaloids N-nornuciferine, O-nornuciferine, and nuciferine from lotus leaf. Seven kinds of 1-alkyl-3-methylimidazolium with different cations and anions were investigated in this work and 1.0M 1-hexyl-3-methylimidazolium bromide ([C(6)MIM]Br) solution was selected as solvent. In addition, the microwave parameters including irradiation power, extraction time and solid-liquid ratio were optimized. Compared with the regular MAE and conventional heat-reflux extraction (HRE), the proposed approach exhibited higher efficiency (0.9-43.7% enhanced) and shorter extraction time (from 2h to 2min), which indicated ILMAE was an efficient, rapid and simple sample preparation technique. Moreover, the proposed method was validated by the linearity, reproducibility, and recovery experiments. Good linearity was observed with the regression coefficients (r(2)) between 0.9998 and 0.9999. The recoveries of all methods were in the range of 94.6% and 105.5% with RSD lower than 6.6%, which indicated that the proposed method was credible.

The evaluation and comparison of trigonal and linear tricationic ion-pairing reagents for the detection of anions in positive mode ESI-MS

A general and sensitive method for detecting divalent anions by ESI-MS and LC/ESI-MS as positive ions has been developed. The anions are paired with tricationic reagents to form positively charged complexes. In this study, four tricationic reagents, 2 trigonal and 2 linear, were used to study a wide variety of anions, such as disulfonates, dicarboxylates, and inorganic anions. The limits of detection for many of the anions studied were often improved by tandem mass spectrometry. Tricationic pairing agents can also be used with chromatography to enhance the detection of anions. The tricationic reagents were also used to detect monovalent anions by monitoring the doubly charged positive complex. The limits of detection for some of the divalent anions by this method are substantially lower than by other current analytical techniques.

Profiling preparations of recombinant birch pollen allergen Bet v 1a with capillary zone electrophoresis in pentamine modified fused-silica capillaries

Three preparation batches of the recombinant birch pollen allergen Bet v 1a have been analyzed by capillary zone electrophoresis (CZE) using a separation electrolyte consisting of 100 mmol L(-1) phosphate at pH 6.50 with 2.0 mmol L(-1) tetraethylenepentamine (TEPA) added. TEPA improved the resolution by wall shielding and selective attachment to allergens, but reduced migration repeatability at concentrations >2.0 mmol L(-1). Heterogeneity of preparations determined by CZE and electrospray ionization-quadrupole-time-of flight-MS were in accordance and revealed chemically modified (carbamylated) allergens in one of the preparations. The method was validated according to the ICH-guidelines. Repeatability of effective electrophoretic mobility (mu(eff)) was <0.55% R.S.D. (n = 5). Migration time corrected peak areas were used for quantification. Limit of quantification (LOQ) was 25 microg mL(-1) for the major isoform Bet v 1a, based on a signal-to-noise ratio of 10, and detector response was linear between LOQ and 0.90 mg mL(-1). Purity of the different rBet v 1a preparations was determined to be between 40 and 92% depending on the manufacturing protocol.

Determination of paeonol and paeoniflorin in Chinese medicine Cortex Moutan and 'Shuangdan' granule by micellar electrokinetic capillary chromatography

An easy, simple and rapid micellar electrokinetic capillary chromatography (MEKC) method was developed for the separation of two active components paeonol (PN) and paeoniflorin (PF) within 7 min. Capillary electrophoresis (CE) was performed using a 50.0 cm (42.0 cm to the detector window) x 75 microm i.d. fused-silica capillary. The optimal running buffer containing 10mM borate and 25 mM SDS at pH 9.54 was employed. The applied voltage 15 kV and the temperature 25 degrees C was used in CE separation. The linearities between peak areas and the concentrations of the analytes were investigated, and they exhibited excellent linear behavior over the investigated concentration ranges (R(2): 0.9945 for PN and 0.9992 for PF). The method was successfully applied to the determination of these two components contained in Cortex Moutan and 'Shuangdan' granule. The average recoveries ranged between 97.6 and 105.3% for PN and 95.3 and 106.1% for PF, respectively.

Capillary electrophoresis for short-chain organic acids and inorganic anions in different samples

This review article is a comprehensive survey of capillary electrophoresis methods developed for the measurement of short-chain organic acids and inorganic anions in a wide variety of matrices, such as food and beverages, environmental, industry, and other applications, as well as clinical applications in body fluids such as urine, plasma or cerebrospinal fluid. Details of sample pretreatment and of electrophoretic conditions have been collected in tables, arranged by the type of matrix. Strategies employed for method development for the analysis of these compounds by capillary electrophoresis in real samples are discussed.

Determination of five toxic alkaloids in two common herbal medicines with capillary electrophoresis

A method was developed for the determination of five highly toxic alkaloids in two commonly used herbal medicines by capillary electrophoresis, which had not been applied to the determination of Aconitum alkaloids before. The buffer contained 40 mM ammonium acetate and 0.1% acetic acid in 80% methanol. Five alkaloids can be determined in 15 min by a single run. The calibration curves showed a linear range from 2 to 200 mg/l for these alkaloids with correlation coefficients (R2) between 0.9988 and 0.9999. Detection limits (SIN = 3) varied from 0.85 to 1.90 mg/l. Recoveries ranged from 95 to 108.8%. The method can provide an effective tool for the strict control of these fetal herbal medicine components.