Nonaqueous Capillary Electrophoresis Research Articles

Clindamycin phosphate-based deep eutectic solvent as a chiral selector for enantioseparation of amino alcohol drugs in nonaqueous capillary electrophoresis

Clindamycin phosphate (CP) exhibits good enantioselectivity for many basic drugs, but its separation effect for most amino alcohol drugs is not satisfactory. In this work, a deep eutectic solvent (DES) chiral selector based on CP was prepared for the first time and utilized as a single chiral selector in nonaqueous capillary electrophoresis (NACE) to separate twelve amino alcohol drugs. Compared with unmodified CP, the separations of model drugs in the DES chiral selector system were significantly improved. Most amino alcohol drugs could be completely separated, and the peak shapes were good. In addition, we used infrared spectroscopy and nuclear magnetic resonance method to study the specific separation mechanism and explored the reasons why DES chiral selector has better enantioselectivity. This work is the first to directly modify antibiotic chiral selector into DES, indicating a direction for us to develop novel chiral recognition materials.

Comparison of aqueous and non-aqueous capillary electrophoresis for the determination of four benzalkonium chloride homologues in compound chemical disinfectants

A new method was established for the simultaneous analysis of four homologous benzalkonium chlorides (dodecyldimethylbenzyl ammonium chloride, tetradecyldimethylbenzyl ammonium chloride, hexadecyldimethylbenzyl ammonium chloride, and octadecyldimethylbenzyl ammonium chloride) in compound chemical disinfectants using non-aqueous capillary electrophoresis (CE) based on a micellar electrokinetic chromatography mode with direct ultraviolet detection. The separation was performed on an uncoated fused quartz capillary with a total length of 60.2 cm and a diameter of 25 μm. The separation buffer consisted of a mixture of methanol/acetonitrile (60:40, v/v) containing 70 mmol/L sodium acetate, 60 mmol/L trifluoroacetic acid and 20 mmol/L sodium dodecyl sulfate. The sample buffer was a methanol solution containing only 2 mmol/L trifluoroacetic acid. The separation voltage was set at 8 kV with a working current of approximately 2.3 μA. The detection wavelength was 214 nm. Under optimal conditions, the limit of detection and limit of quantification for these four benzalkonium chlorides (BACs) were 1.0 mg/L and 5.0 mg/L, respectively. Good linearities were observed in the concentration ranges from 5.0 to 100.0 mg/L, with correlation coefficients above 0.999 for all compounds. The recoveries of these four BACs ranged from 92.5 % to 109.1 % with relative standard deviations below 4.7 %. With the new method, all four BACs could be analyzed in a single injection. In contrast, the aqueous CE method in the National Standard GB/T 26369-2020 only allowed for the simultaneous analysis of the first three homologous. The new method demonstrated the improved peak shape compared to the aqueous CE method and then was successfully applied to the analysis of 19 commercially available samples, such as object table disinfectants, hand sanitizers, and disinfectant wipes, which claimed to contain quaternary ammonium compound. The results obtained using the new method were compared with those of the aqueous CE of the National Standard Method, and no statistically significant differences were observed. The new method is simple in pre-treatment and provides accurate results, making it highly suitable for routine analysis.

Deep eutectic solvents as a green alternative to organic solvents for β-cyclodextrin pseudo-stationary phase in capillary electrophoresis

β-cyclodextrin (β-CD), as an important pseudo-stationary phase (PSP) in capillary electrophoresis (CE), frequently confronts challenges stemming from its limited water solubility, particularly when high concentrations are required for resolving complex analytes. Traditionally, researchers often resort to the use of (toxic) organic solvents to enhance the solubility of β-CD, establishing non-aqueous capillary electrophoresis (NACE) for specific separations. However, such practices are hazardous to health and run counter to the principles of green analytical chemistry. In this study, we demonstrate a deep eutectic solvent (DES), Proline:Urea (PU), as a promising alternative to conventional organic solvents for β-CD-based CE separations. The DES exhibits a solubility of up to 30% for β-CD, a significant improvement compared to the 1.8% solubility in the aqueous phase. Utilizing this DES-type separation medium, we achieved simultaneous baseline separation of a complex analyte composed of eight structurally similar naphthoic acid derivatives. Furthermore, we conducted a systematic comparison of β-CD's performance in aqueous CE buffers, organic solvents, and DESs, highlighting the superiority of this novel and environmentally friendly CE separation medium.

Capillary electrophoresis separations with deep eutectic solvents as greener separation media: A proof-of-concept study

Capillary electrophoresis (CE) has conventionally been classified into aqueous and non-aqueous categories based on the types of buffer solvents employed. Traditionally, non-aqueous CE has always been associated with the use of organic solvents, which are considered hazardous to health and environmentally detrimental. In this work, we introduce deep eutectic solvents (DESs) as CE separation media for the first time, presenting a novel and environmentally friendly approach to CE separations. The DES employed consists of proline and urea (Proline:Urea, PU), both of which are naturally occurring compounds that are readily available, cost-effective, and environmentally benign. Various fundamental aspects of the DES-type CE media were investigated, including thermal property, viscosity, electroconductivity, Joule heating effect, and compatibility with detectors. A simulated complex mixture of ten naphthalene-based compounds with varied charges and sizes was separated using the DES-based medium in capillary zone electrophoresis (CZE) mode. Moreover, we also established a DES-based micellar electrokinetic chromatography (MEKC) system utilizing Tween-20 as the surfactant. Six structurally similar naphthalene derivatives (isomers) that couldn't be resolved by CZE were effectively separated due to their strong hydrophobic interaction with Tween-20 micelles within the DES medium. Given that DESs are “designer” solvents with highly tunable properties and environmentally friendly characteristics, this study demonstrates the potential of employing DESs as an alternative to organic solvents for greener CE separations.

Quick and Concise Nonaqueous Capillary Electrophoresis Approach for Simultaneous Separation and Determining Five Phytohormones

A new, quick and concise nonaqueous capillary electrophoresis approach has been matured to separate phytohormones involving indobutyric acid, indoleacetic acid, abscisic acid, 1-naphthaleneacetic acid and gibberellin. Using a running buffer composed of 85% methyl cyanide, 0.8% 1.0 M caustic soda and 20.0 mM methanol ammonium acetate, satisfactory separation of five phytohormone standards was achieved within 4 mins. The lowest detection limit was obtained for 1-naphthaleneacetic-acid (0.06 and#181;g/ml) and the highest for gibberellin (1.71 and#181;g/ml). The approach has been utilized for wheat bud samples with spiked 5 phytohormones using a solid phase extraction procedure, acquiring recovery percentage ranging from 95 to 102%.

Expanding Lipidomic Coverage in Multisegment Injection-Nonaqueous Capillary Electrophoresis-Mass Spectrometry via a Convenient and Quantitative Methylation Strategy.

Orthogonal separation techniques coupled to high-resolution mass spectrometry are required for characterizing the human lipidome, given its inherent chemical and structural complexity. However, electrophoretic separations remain largely unrecognized in contemporary lipidomics research compared to established chromatographic and ion mobility methods. Herein, we introduce a novel derivatization protocol based on 3-methyl-1-p-tolyltriazene (MTT) as a safer alternative to diazomethane for quantitative phospholipid (PL) methylation (∼90%), which enables their rapid analysis by multisegment injection-nonaqueous capillary electrophoresis-mass spectrometry (MSI-NACE-MS). Isobaric interferences and ion suppression effects were minimized by performing an initial reaction using 9-fluorenylmethyoxycarbonyl chloride prior to MTT and a subsequent back extraction in hexane. This charge-switch derivatization strategy expands lipidome coverage when using MSI-NACE-MS under positive ion mode with improved resolution, greater sensitivity, and higher throughput (∼3.5 min/sample), notably for zwitterionic PLs that are analyzed as their cationic phosphate methyl esters. Our method was validated by analyzing methyl-tert-butyl ether extracts of reference human plasma, which enabled a direct comparison of 48 phosphatidylcholine and 27 sphingomyelin species previously reported in an interlaboratory lipidomics harmonization study. The potential for plasma PL quantification by MSI-NACE-MS via a serial dilution of NIST SRM-1950 was also demonstrated based on estimation of relative response factors using their reported consensus concentrations. Moreover, lipid identification was supported by modeling predictable changes in the electrophoretic mobility for cationic PLs in conjunction with MS/MS. Overall, this work offers a practical derivatization protocol to expand lipidome coverage in CE-MS beyond the analysis of hydrophilic/polar metabolites under aqueous buffer conditions.

Capillary electrophoresis in the analysis of therapeutic peptides-A review.

Therapeutic peptides are a growing class of innovative drugs with high efficiency and a low risk of adverse effects. These biomolecules fall within the molecular mass range between that of small molecules and proteins. However, their inherent instability and potential for degradation underscore the importance of reliable and effective analytical methods for pharmaceutical quality control, therapeutic drug monitoring, and compliance testing. Liquid chromatography-mass spectrometry (LC-MS) has long time been the "gold standard" conventional method for peptide analysis, but capillary electrophoresis (CE) is increasingly being recognized as a complementary and, in some cases, superior, highly efficient, green, and cost-effective alternative technique. CE can separate peptides composed of different amino acids owing to differences in their net charge and size, determining their migration behavior in an electric field. This review provides a comprehensive overview of therapeutic peptides that have been used in the clinical environment for the last 25 years. It describes the properties, classification, current trends in development, and clinical use of therapeutic peptides. From the analytical point of view, it discusses the challenges associated with the analysis of therapeutic peptides in pharmaceutical and biological matrices, as well as the evaluation of CE as a whole and the comparison with LC methods. The article also highlights the use of microchip electrophoresis, nonaqueous CE, and nonconventional hydrodynamically closed CE systems and their applications. Overall, the article emphasizes the importance of developing new CE-based analytical methods to ensure the high quality, safety, and efficacy of therapeutic peptides in clinical practice.

Analysis of Two Single and Three Double Long-Chain Quaternary Ammonium Compounds via Non-Aqueous Capillary Electrophoresis with Indirect Ultraviolet Detection

A novel method utilizing non-aqueous capillary electrophoresis (NACE) with indirect ultraviolet detection (IUD) has been developed for the analysis of five quaternary ammonium compounds (QACs). The QACs analyzed in this study include dodecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium bromide, dioctyl dimethyl ammonium chloride, octyldecyl dimethyl ammonium chloride and didecyl dimethy ammonium bromide. The separation process was carried out on an uncoated fused quartz capillary with a total length of 50.2 cm (effective length 40.0 cm) and a diameter of 50 μm. The separation buffer consisted of a mixture of MeOH/ACN (90:10, v/v) containing 2 mmol/L sodium acetate, 2 mmol/L trifluoroacetic acid (TFA) and 16 mmol/L dodecyl dimethyl benzyl ammonium chloride. The sample buffer utilized a mixture of MeOH/ACN (20:80, v/v) containing 2 mmol/L TFA. During analysis, a separation voltage of 7 kV was applied, resulting in a current of approximately 2.3 μA. The detection wavelength was set at 214 nm to ensure optimal sensitivity. Under optimal conditions, the method exhibited excellent performance characteristics, with a limit of detection of 0.5 mg/L and a limit of quantitation of 5.0 mg/L for the five QACs. Linear calibration curves were obtained in a concentration range of 5.0 to 100.0 mg/L, with correlation coefficients exceeding 0.999 for all compounds. The recoveries of the five QACs ranged from 92.3% to 114.7%, with relative standard deviations below 7.4%. To assess the applicability of the NACE-IUD method, 17 commercially available samples were successfully analyzed. The results confirmed the suitability of the method for accurate determination of the five QACs in disinfectant products. Notably, this method offers an environmentally friendly approach for the analysis of these QACs.

Determination of trimetazidine in urine by capillary electrophoresis with amperometric detection

In this contribution, nonaqueous capillary electrophoresis with end-column amperometric detection using a platinum ultramicroelectrode is presented along with several extraction procedures, both liquid–liquid extraction (LLE) and solid-phase extraction (SPE), for extracting trimetazidine from urine. Trimetazidine is an anti-ischemic drug, which changes hearth metabolism pathways and is being abused as a doping. Electrochemical detection in a nonaqueous environment provided a stable response with a relative standard deviation of only 3.6% (n = 10) in repeatability measurement at concentration of 50 µg cm−3. LOD and LOQ of the proposed method were determined as 0.054 µg cm−3 and 0.180 µg cm−3, respectively. From the point of view of LLE, the most efficient procedure was the double extraction with ethyl acetate as an extraction agent in combination with prior alkalinization of the sample by Na2CO3. Nevertheless, the extraction efficiency was only around 68%. The most efficient SPE procedure was based on the combination of HLB cartridge and elution with background electrolyte containing 20% of methanol. Its recovery reached up to 92% and 101% in case of 50 µg cm−3 and 5.0 µg cm−3 of trimetazidine in urine, respectively.Graphical abstract

Characterization of isomeric lipid A species from Pseudomonas aeruginosa PAO1 by non-aqueous capillary electrophoresis with positive and negative ion electrospray tandem mass spectrometry

Pseudomonas aeruginosa is a priority target pathogen for antibiotic research and development because of its high resistance to a wide range of antibiotics. Acquisition of resistance is sometimes associated with modifications of the lipid A component present in the outer membrane of most Gram-negative bacteria. For a deeper understanding of subtle chemical variations of lipid A in relation to biological properties, the structural elucidation of lipid A species within a bacterial strain is of crucial importance. However, the simultaneous presence of monophosphorylated positional isomers in naturally heterogeneous lipid A samples cannot easily be recognized with direct MS measurements or with conventional LC-MS strategies. Herein, we present the application of a non-aqueous capillary electrophoresis (NACE) method coupled to positive and negative ion electrospray tandem mass spectrometry with collision-induced dissociation (CID) activation technique for the in-depth analysis of the lipid A isolate of P. aeruginosa PAO1. The main advantage of our NACE strategy is its separation power regarding the site of phosphorylation of the lipid A structures, which makes it a good orthogonal technique to chromatographic characterizations of the bacterial lipid A composition, where the separation is mainly based on acylation differences of the species. Overall, the results of this electrophoretic approach revealed hitherto unreported isomeric monophosphorylated PAO1 lipid A constituents, including both phosphate and acyl chain positional isomers. The parallel fragmentation in the complementary positive and negative ion modes enabled the unequivocal assignment of the phosphorylation site and position of acyl chains in lipid A compounds of three acylation families ranging from tetra- to hexa-acylation. Moreover, C1-monophosphorylated lipid A species have been identified in P. aeruginosa for the first time.

Development of Novel Analytical Methods Based on Liquid Chromatography and Electrophoresis

High-performance liquid chromatography (HPLC) and electrophoresis are liquid phase separation methods and are frequently used in various research fields. Although their origins are sufficiently old, the development of novel separation methods based on HPLC and electrophoresis are still required for both fundamental and applicational functions. In this paper, we introduced our fundamental studies of the development of novel analytical methods based on HPLC and electrophoresis toward enhancing separation efficiency. The contents can be categorized as follows: (1) enhancement of separation in pressurized flow-driven capillary electrochromatography, (2) orthogonal electrochromatography for simultaneous two-dimensional separation, (3) development of new stationary phases/columns in HPLC, (4) development of low and ultra-low-temperature HPLC using liquefied gas mobile phase, (5) development of nonaqueous capillary electrophoresis for analyzing water-insoluble synthetic polymers, and (6) development of frequency division multiplex HPLC-MS.

Simultaneous determination of triclosan，triclocarban and p-chloro-m-xylenol in disinfectant，personal care products and oiltment by nonaqueous capillary electrophoresis

Triclosan （TCS）， triclocarban （TCC）， and p-chloro-m-xylenol （PCMX） are some of the most widely used antibiotics because of their broad-spectrum and highly-efficient bactericidal effects. In the context of disinfection， the National Standard GB 38598-2020 stipulates that the contents of the effective ingredients present in a disinfectant must be specified， wherein their range must fall within 90%-110% of the specified central value. To ensure a suitable product quality， analysis by high performance liquid chromatography （HPLC） is recommended by both the GB/T 27947-2020 and GB/T 34856-2017. However， the results analyzed according to the National Standard method often exceed the declared contents， thereby indicating the necessity to establish a new method based on a completely different principle （e. g.， capillary electrophoresis）， especially since it was not possible to analyze TCS， TCC， and PCMX in a single injection using the National Standard method. Moreover， using this method， large amounts of methanol were consumed， which could be potentially harmful to both operators and the environment. In terms of their water solubilities， this decreases in the order of PCMX>TCS>TCC， wherein TCC is insoluble in water. As such， the use of nonaqueous capillary electrophoresis （NACE） based on running buffer solutions prepared in pure organic solvents （e. g.， methanol or acetonitrile） is necessary. In this paper， a new NACE approach combined with an ultraviolet detection method was developed for the simultaneous analysis of TCS， TCC， and PCMX in disinfectants， personal care products， and ointments. For this purpose， an uncoated fused silica capillary （20 cm×50 μm， total length=30.2 cm） was used as the separation column with a separation buffer composed of 14 mmol/L sodium borate， 2 g/L polyethylene glycol （PEG） 20000， and 0.5 mmol/L dodecyltrimethylammonium bromide （DTAB） in methanol. Following optimization of the separation parameters， the complete and simultaneous separation of TCS， TCC， and PCMX was achieved when the sample solution was prepared using 5 g/L PEG 20000 in methanol-acetonitrile （50∶50， v/v）. It was possible to directly inject the sample into the analysis system after a simple dilution with the sample medium， and no interference was observed in any of the sample electropherograms when a separation voltage and detection wavelength of -12 kV and 214 nm were employed， respectively. Furthermore， TCS， TCC， and PCMX showed good linear relationships with their corrected peak areas within a mass concentration range of 1-100 mg/L， and the correlation coefficients （r） were all greater than 0.99. Moreover， the limits of detection （LODs， S/N=3） and limits of quantification （LOQs， S/N=10） were determined to be 0.2 and 1 mg/L， respectively. The spiked recoveries ranged from 94.5% to 104.4% with relative standard deviations of ≤4.8% in all cases. Subsequently， the established method was used to analyze 31 commercial samples， including hand sanitizer， disinfectant， baby powder， and antibacterial cream. A comparative analysis of HPLC， the developed NACE method， and our previously reported micellar electrokinetic chromatographic （MEKC） method was also carried out for the quantitative determination of TCS， TCC， and PCMX. Although no statistically significant differences were observed among the three methods， the results determined for 16 out of the 31 samples did not match the claimed contents. These results therefore indicate the necessity to further control the compositions of disinfectant products. Our results indicate that the newly established NACE method can be an important alternative to HPLC for routine laboratory analyses， especially considering that it minimizes waste generation， requires only a simple sample pretreatment process， and exhibits a good selectivity to the target compounds. It is therefore hoped that the NACE method will be incorporated into the National Standard method in the near future.

Coupling capillary electrophoresis-electrospray ionization mass spectrometry with sheathless interface for drug analysis

Capillary electrophoresis-mass spectrometry （CE-MS） combines the advantages of capillary electrophoresis， such as the high separation efficiency and low sample consumption， and the high detection sensitivity of mass spectrometry and the ability for providing the structural information for structure elucidation of unknown components. However， the interface technology for coupling capillary electrophoresis and mass spectrometry is still not well resolved. In the present work， we explored the application of the sheathless CE-MS interface which was prepared by gold foil-wrapped CE separation column tip directly as a spray electrode for the analysis of five tyrosine kinase inhibitors， namely sunitinib， imatinib mesylate， gefitinib， dasatinib and erlotinib. This interface integrates separation and electrospray ionization in one capillary， which is easy to manufacture， low in cost， and can be produced in batches. We found that using the nonaqueous CE separation mode can not only achieve baseline separation of five tyrosine kinase inhibitors， but also obtain stable mass spectrometry signals. First， we investigated the effect of the electrolyte solution composition on the separation. The optimized background electrolyte composition was obtained： 2% （v/v） acetic acid and 5 mmol/L ammonium acetate in acetonitrile-methanol （80∶20， v/v）. Under optimized conditions， the five kinase inhibitors could be baseline separated， meantime， the sheathless interface could also maintain stable electrospray for a long time. The relative standard deviation （RSD） values of the intraday and interday repeatability of the analyte retention times were less than 0.5% and 0.8%， respectively， and the RSD value between interface batches is less than 2.6%. Compared with CE-MS with aqueous phase， the separation column efficiency of the five tyrosine kinase inhibitors under nonaqueous phase conditions is higher， the detection sensitivity is higher， and the absolute detection limit reaches amol level. In addition， we evaluated the sheathless interface with various organic acids， such as palaflin A， salvianolic acid C， and rosmarinic acid， as well as hydrophobic macrolide antibiotics， azithromycin， erythromycin， and sporin A， good separation effect and mass spectrometric detection results can be obtained.

Advances in the Applications of Capillary Electrophoresis to Tobacco Analysis

Background: Capillary electrophoresis (CE) has found a wide range of applications because of its high separation efficiency, low expense, short analysis time and minimal sample volume requirement. The tobacco quality depends on the nature and quantity of numerous substances. CE has been applied in the constituent analysis of tobacco and tobacco products for quality control and tobacco research. Methods: The advances in the applications of CE to tobacco analysis are reviewed. The main subjects cover the separation modes of CE, the detection techniques of CE, sample preparations and the applications of CE in the measurements of various constituents in tobacco samples. In addition, the CE-based metabonomic investigation of tobacco is also introduced. Results: Capillary zone electrophoresis, micellar electrokinetic chromatography, capillary isotachophoresis, capillary gel electrophoresis, capillary electrochromatography and non-aqueous CE have been applied in the determination of a variety of constituents in tobacco and tobacco products. The assayed substances include alkaloids, amines, saccharides, organic acids, inorganic ions, phenols, phenolic acids, flavonoids, amino acids, peptides, proteins, hormones, agricultural chemicals, etc. Conclusion: This review demonstrates that CE is a promising analytical technique in the field of tobacco analysis. It is anticipated that CE will find more and more applications in tobacco investigations.

Nonaqueous Capillary Zone Electrophoresis for Polyesters and Polyamides Using Hexafluoroisopropyl Alcohol as Electrophoretic Medium

Nonaqueous capillary zone electrophoresis (NACZE) utilizing cationic reagents as an electrophoresis promoter has the potential for separating water-insoluble synthetic polymers and that with tetrahydrofuran based electrophoretic media containing cationic reagents has been reported. In this study, NACZE using hexafluoroisopropyl alcohol (HFIP)-based media was developed for separating polyesters and polyamides, which were insoluble in tetrahydrofuran. Nonaqueous media of HFIP containing 400 mM cetyltrimethylammonium chloride (CTAC) and 50 mM trihexyl(tetradecyl)phosphonium chloride (P66614Cl) were used, and it was found that hydrophobic P66614 cation enhanced the electrophoresis of both polyesters and polyamides compared with cetyltrimethylammonium cation. The media containing CTAC resulted in partially separated poly(ethylene terephthalate)/poly(hexamethylene terephthalate) and poly(ethylene terephthalate)/poly(ethylene naphthalate), but P66614Cl failed to separate them. By contrast, nylon 6I and nylon 6/6I were separated with the P66614Cl media, whereas they were co-eluted in the media with CTAC.

Non-aqueous capillary electrophoresis–time of flight mass spectrometry method to determine emerging mycotoxins

Enniatins (ENN) and beauvericin (BEA) are emerging mycotoxins that have been traditionally determined by liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS). However, to the best of our knowledge, no analytical methods based on capillary electrophoresis (CE)–MS/MS have been reported so far. Due to their non-polar nature, in this work, a non-aqueous CE (NACE) method coupled to quadrupole time-of-flight–MS is proposed for the first time to identify and quantify these mycotoxins. Determination was achieved in 4 min under optimum conditions: 40 mM ammonium acetate in 80:20 (v/v) acetonitrile-methanol (buffer), 30 kV (voltage), 80 cm (capillary length), 20 °C (capillary temperature) and 50 mbar × 30 s (injection). Higher selectivity can be achieved when compared with LC due to the formation of exclusive CE adducts such as [M + CH3CH2NH3]+. “All Ions” acquisition mode was selected as it allows the quantification of the usual ENNs, as well as the identity confirmation of less common ENNs.The method was validated for wheat samples, obtaining limits of quantification from 4.0 to 8.3 μg/kg depending on the emerging mycotoxin, recovery values higher than 87.4%, and intra- and inter-day precision values (RSDs) lower than 15.1% in all cases. Finally, 29 wheat samples were analyzed, finding 26 samples with concentrations of enniatin B higher than the limit of quantification (7.5–1480 μg/kg), 20 for enniatin B1 (5.2–550 μg/kg), 7 for enniatin A (10–55 μg/kg), 4 for enniatin A1 (12.6–77 μg/kg) and 5 for BEA (9.2–16.4 μg/kg). Moreover, two other ENNs were tentatively identified.

A Non-aqueous Capillary Electrophoresis for Determination of Eugenol in Cloves and Dental Preparations

A total non-aqueous capillary electrophoresis method was developed and applied for the first time for the quantification of eugenol in cloves and dental preparations. The optimized conditions included a buffer consisting of 150 mM sodium acetate and 300 μL 1 M acetic acid methanol solution (30 mM), an applied voltage of 25 kV, and a temperature of 25 °C and an applied wavelength of 214 nm. The developed method of determining the eugenol was characterized by the following parameters: a detection time within 1.97 min, good linearity (R2 = 0.9989–0.9999), detection limit at the level from 0.19 to 0.35 µg mL−1, very good extraction yield of 99.6–100.6% from both methanol standard solutions, clove buds’ matrix, and dental preparations. Limit of quantitation at the level from 0.81 to 0.98 µg mL−1. The method is based on the developed one-step extraction procedure. Moreover, the developed method does not require the use of any eugenol solubility enhancers such as SDS.

Solid phase extraction prior to non-aqueous capillary electrophoresis with ultraviolet detection as a valuable strategy for therapeutic drug monitoring of cabozantinib

Solid phase extraction (SPE) prior to non-aqueous capillary electrophoresis (NACE) with ultraviolet detection was used for the first time for the determination of cabozantinib (CBZ), the main drug used for the treatment of metastatic renal cancer, in urine. SPE was carried out in commercial C18 cartridges loaded with 8 mL of urine. Tamoxifen (TAM) was added as internal standard. After removal of the matrix with 8 mL of phosphate buffer (pH 7.0; 10 mM), 7 mL of MeOH:H2O (30:70; v/v) and 0.5 mL of MeOH, CBZ and TAM were eluted with 1.5 mL of methanol. The eluate was evaporated to dryness and reconstituted in background electrolyte (BGE). The CE method was carried out in a fused silica capillary (30 cm × 75 µm i.d.) at 19 °C at 10 kV with a BGE consisting of ammonium acetate (pH 7.0; 8 mM) containing 3 % acetic acid (v/v) in methanol.The preconcentration factor achieved was 5.3, and the limits of detection and quantification were 3.7 and 12 µg/L in urine, respectively. Linearity was observed up to 950 µg/L. Intra-day precision at 20, 400, and 850 µg/L of CBZ (n = 8) was below 10 % in peak areas. As for inter-day precision, no statistical differences were found in two consecutive days, according to the Snedecor “F” test (p > 0.05). Recovery studies in spiked urine samples ranged from 91.4 to 116.6 %.The present method was applied to samples from a patient under treatment with CBZ for metastatic renal cancer as an alternative to the current strategies for therapeutic drug monitoring.

Separation and Determination of Matrine, Oxymatrine and Sophoridine in Composite Preparations by Non-aqueous Capillary Electrophoresis

A new, simple, and quick method for the simultaneous determination of three alkaloids (matrine, sophoridine, and oxymatrine) in composite preparations by nonaqueous capillary electrophoresis has been developed. A running buffer composed of 60% acetonitrile + 0.75% acetic acid + 25 mM ammonium acetate in methanol was found to be the most suitable for this separation. The limits of detection for three alkaloids were over the range of 0.45–0.6 μg/ml. In the tested concentration range, good linear relationships between peak areas and concentrations of the analytes were obtained. This method has been successfully applied to simultaneous determination of the three alkaloids with recoveries over the range of 95.6 to 97.2%. This new non-aqueous capillary electrophoresis method established has been successfully used for the simultaneous separation and determination of sophoridine, matrine and oxymatrine in complex preparations in 5 minutes.

High Performance Separation of Metal Complexes by Non-aqueous Capillary Gel Electrophoresis Using Hydroxypropyl Methylcellulose

High Performance Separation of Metal Complexes by Non-aqueous Capillary Gel Electrophoresis Using Hydroxypropyl Methylcellulose