Peak Migration Time Research Articles

Quantitative Analysis of Chondroitin Sulfate and Dermatan Sulfate Using Capillary Electrophoresis With Gaussian Distribution‐Based Peak Fitting for Improved Peak Resolution

ABSTRACTIn this work, capillary electrophoresis with Gaussian distribution‐based peak fitting for improved peak resolution for simultaneous quantitative analysis of chondroitin sulfate (CS) and dermatan sulfate (DS) was developed for the first time. The effects of different pH, voltage, and peak shapes on the peak fitting were investigated. The results indicate that separation conditions that affect peak shape have a significant impact on peak fitting. Under optimized separation conditions, the peak fitting achieves high accuracy and precision, the relative standard deviation (n = 5) of peak area and migration time of CS and DS were 1.1%, 1.8% and 0.94%, 0.84%, respectively. Furthermore, the results obtained by peak fitting were close to real values. The developed method was used to analyze the purity of CS. The results had a high consistency with the labeled value; furthermore, the peak fitting could point out the number of possible impurities. The developed method has good potential for the analysis of other glycosaminoglycans with peak overlap.

Study of reactive dyes and their hydrolyzed forms in a real trichromatic dyeing process by capillary electrophoresis with UV detection.

Detecting the concentration of reactive dyes and their hydrolyzed products is essential for controlling the dyeing process and is an important guide for upgrading and improving textile dyeing technology. In this study, capillary electrophoresis (CE) with UV detection was for the first time applied in a real trichromatic dyeing process to provide qualitative and quantitative determination of reactive dyes and their hydrolyzed forms. Here, three original reactive dyes (SES-Cl-red-195, SES-Cl-yellow-145, and SES-Cl-blue-194), their vinyl sulfone forms (VS-Cl-red-195, VS-Cl-yellow-145, and VS-Cl-blue-194), and complete hydrolyzed forms (HES-OH-red-195, HES-OH-yellow-145, and HES-OH-blue-194) could be baseline separated in our developed BGE comprised of 10.0 mol/L Na2B4O7, 15% (V/V) ACN at pH 8.50 that adjusted by 0.50 mol/L H3BO3. The LODs (S/N = 3) of nine analytes ranged from 0.3 to 1.3 mg/L, and high sensitivities were achieved with UV detection. The RSDs of peak area and migration time were in the ranges of 1.4-3.8% and 0.39-1.29%, which indicated the CE methods were reliable for studying different dye forms in complex dye baths, and for evaluating dyeing process quality. Thus, the percentage of dye-uptake in single and trichromatic combination dyes was calculated based on the concentration of the original and their vinyl sulfone and hydrolyzed forms, and the result was consistent with the traditional UV-Vis method.

SUB-MINUTE CAPILLARY ZONE ELECTROPHORESIS METHOD FOR DETERMINATION OF HYDROCHLOROTHIAZIDE IN COMBINATION WITH OTHER ACTIVE INGREDIENTS IN NINE DIFFERENT PHARMACEUTICAL SAMPLES

Capillary electrophoresis (CE) methods have unique potential for applications in quality control of pharmaceutical formulations. Here, we show that a single and ultra-fast CE method can be used for the determination of hydrochlorothiazide (HCT) in combination with nine other active ingredients in a single run in different pharmaceutical samples: atenolol (ATE), metoprolol (MET), propranolol (PRO), benazepril (BEN), captopril (CAP), enalapril (ENA), lisinopril (LIS), ramipril (RAM), and valsartan (VAL). This goal was achieved using a single and simple background electrolyte (BGE) composed of 10 mmol L-1 of boric acid with pH adjusted to 9.0 with sodium hydroxide. All samples can be analyzed in less than 1 min with the attainment of good analytical performance, such as high-resolution separation (r > 1.3), low sample and reagents consumption (environmentally friendly method), low relative standard deviation (RSD) values for peak area (< 4.0%) and migration times (< 1.7%), and linear relationships with good correlation coefficients (> 0.995). Furthermore, recovery tests showed good results (100 ± 5%) for all evaluated compounds.

A-163 Abnormal HbA1c Results Lead to an Unexpected Chronic Myeloid Leukemia Diagnosis

Abstract Background Hemoglobin A1c (HbA1c) is used to assess and monitor glycemic control, as it reflects average levels of blood glucose over the previous two to three months. HbA1c can be measured by capillary electrophoresis (CE) which calculates percent HbA1c from the HbA1c and HbA peaks in the electropherogram. CE is a prominent method in reference labs as it provides complete automation with fast separation and less interference than what can be observed with other assay formats. The high-resolution capability of CE allows the quantification of HbA1c, even in the presence of labile HbA1c, carbamylated and acetylated hemoglobins, and major hemoglobin variants. These variants are commonly recognized as causes of interference in HbA1c measurements. Case presentation A 70-year-old male with a history of type 2 diabetes mellitus presented to an outpatient laboratory for routine venipuncture to evaluate glycemic management and cardiovascular disease risk. HbA1c analysis by CE resulted with a flag for an atypical profile in the electropherogram and no HbA1c value was reported. HbA1c measurements throughout the past year demonstrated HbA1c values ≥6.5% yet trending downward, consistent with his diagnosis and treatment of diabetes mellitus. HbA1c was repeated with a different instrument and fresh specimen collected at a different phlebotomy location and showed similar inconclusive results. Unusual shifts in hemoglobin peak migration times were observed upon close review of the electropherogram, suggesting a potential analytical interference of the HbA1c measurement. Results Because atypical peak migration times due to elevated leukocyte counts or increased viscosity are documented by the manufacturer, a follow up complete blood count (CBC) was recommended for this patient. CBC results revealed a highly elevated leukocyte count of 175.80 k/μL (reference interval: 4.30–11.30 k/μL), suggesting the abnormal HbA1c migration profile was possibly due to leukocytosis. The elevated leukocyte count led the patient to visit an oncology clinic where leukemia/lymphoma phenotyping, ancillary studies, and cytogenic testing, confirmed a diagnosis of chronic myeloid leukemia. The diagnosis was completely unexpected, as the patient’s only complaint was feeling fatigued over the last few weeks. The patient began chemotherapy treatment immediately. Conclusion The present case is an example of how leukocytosis and hyperviscosity can interfere with HbA1c measurement by CE. Although this specific clinical situation is uncommon, clinicians and laboratorians should be aware of these potential interferences, as they have not been discussed in detail in the literature. Further, these interferences warrant recognition in the cancer patient population, as this population may be directly impacted by elevated leukocyte count and hyperviscosity in their specimens, which may impact glycemic control monitoring during treatment. The incidence of diabetes in cancer patients is six times greater than in the general population, making glycemic control monitoring key for cancer patients. Many diabetic patients undergoing chemotherapy will prioritize their cancer treatment over management of their diabetes, which increases their risk for poor glycemic control. These patients should be carefully monitored to ensure HbA1c results are accurate as poor glycemic control can lead to increased risk for infections and hospitalizations, which may decrease survivorship.

Analysis of naphthenic acids in produced water samples by capillary electrophoresis-mass spectrometry.

A capillary electrophoresis-mass spectrometry method was used to analyze naphthenic acids in produced water samples. It was possible to detect cyclopentanecarboxylic, benzoic, cyclohexanebutyric, 1-naphthoic, decanoic, 3,5-dimethyladamantane-1-carboxylic, 9-anthracenecarboxylic, and pentadecanoic acids within ca. 13min using a buffer composed of 40mmol/L ammonium hydroxide, 32mmol/L acetic acid and 20% v/v isopropyl alcohol, pH 8.6. The proposed method showed good repeatability, with relative standard deviation (RSD) values of 6.6% for the sum of the peak areas and less than 2% for the analysis time. In the interday analysis, the RSD values for the sum of the peak areas and migration time were 10.3% and 10%, respectively. The developed method demonstrated linear behavior in the concentration range between 5 and 50mg/L for benzoic, decanoic, 3,5-dimethyladamantane-1-carboxylic and 9-anthracenecarboxylic acids, and between 10 and 50mg/L for cyclopentanecarboxylic, cyclohexanebutyric, 1- naphthoic, and pentadecanoic acids. The detection limits values ranged from 0.31 to 1.64mg/L. Six produced water samples were analyzed and it was possible to identify and quantify cyclopentanecarboxylic, benzoic, cyclohexanebutyric, and decanoic acids. The concentrations varied between 4.8 and 98.9mg/L, proving effective in the application of complex samples.

A hydrodynamic injection approach for capillary electrophoresis using rotor-stator valves.

Sample injection is a critical step in a capillary electrophoresis (CE) analysis. Electrokinetic injection is the simplest approach and is often selected for implementation in portable CE instruments. However, in order to minimize the effect of sample matrix upon the results of a CE analysis, hydrodynamic injection is preferred. Although portable CE instruments with hydrodynamic injection have been reported, injection has always been performed at the grounded end of the capillary. This simplifies fluidic handling but limits coupling with electrochemical detectors and electrospray ionization-mass spectrometry (ESI-MS). We demonstrated previously that injection at the high-voltage (HV) end of the capillary could be performed using an HV-compatible rotary injection valve (fixed-volume injection). However, the mismatch between the bore sizes of the channels on the rotor-stator valve and the separation capillary caused peak tailing and undesired mixing, impairing analytical performance. In this work, we present an HV-compatible hydrodynamic injection approach that overcomes the issues associated with the fixed-volume injection approach reported previously. The performance of the CE instrument was demonstrated by analyzing a mixture of 13 amino acids by CE coupled to laser-induced fluorescence, which showed relative standard deviations for peak area and migration time below 5% and 1%, respectively, for triplicate analysis. Additionally, replicate measurements of a mixture of amino acids, peptides, nucleobases, and nucleosides by CE coupled to electrospray ionization-mass spectrometry (CE-ESI-MS) were performed to evaluate peak tailing, and results were similar to those obtained with a commercial CE-ESI-MS setup.

Development of a capillary electrophoretic method for determination of ketorolac enantiomers in human plasma using cationic β-cyclodextrin derivative as a chiral selector.

A novel approach for the separation of ketorolac enantiomers by capillary electrophoresis is presented. A cationic β-cyclodextrin derivative based on imidazole was synthesized and used as a chiral selector in the background electrolyte. The influence of pH and ionic strength of background electrolyte, as well as cationic β-cyclodextrin derivative concentration on the resolution of ketorolac enantiomers, was investigated. The highest value of the resolution for ketorolac enantiomers was 1.46 when the background electrolyte consisted of 25mM NaH2 PO4 (pH 6.4) with 1mM 1-butyl-3-β-cyclodextrinimidazolium tosylate. Additionally, the possibilities of cationic derivatives for the separation of ketoprofen enantiomers were shown (peak resolution 1.06). The two-step preconcentration mode was developed to reduce the limit of detection of individual enantiomers. The proposed approach was successfully applied to determine ketorolac enantiomers in tablet "Ketorol express" and human plasma. The calibration range of ketorolac enantiomers for plasma samples was 0.25-2.50μg/ml with coefficients of determination ≥ 0.99. The relative standard deviation both of the peak area and migration time was less than 15%, as well as the accuracy ranged from 90.1% to 110.2% for both analytes. The limits of detection were 44 and 55ng/ml for R- and S-ketorolac. The quantity of ketorolac in plasma was verified with high-performance liquid chromatography.

Determination of naphthenic acids in produced water by using microchip electrophoresis with integrated contactless conductivity detection

This study reports for the first time the use of a microchip electrophoresis (ME) device with integrated capacitively coupled contactless conductivity detection (C4D) to analyze naphthenic acids in produced water. A mixture containing 9-anthracenecarboxylic, 1-naphthoic, and benzoic acids was separated and detected using a running buffer composed of 10 mmol L−1 carbonate buffer (pH = 10.2). The separation was achieved within ca. 140 s with baseline resolution greater than 2 and efficiency values ranging from 1.9 × 105 to 2.4 × 105 plates m−1. The developed methodology provided linear correlation with determination coefficients greater than 0.992 for the concentration ranges between 50 and 250 µmol L−1 for benzoic and 9-anthracenecarboxylic acids, and between 50 and 200 µmol L−1 for 1-naphthoic acid. The achieved limit of detection values varied between 4.7 and 7.7 µmol L−1. The proposed methodology revealed satisfactory repeatability with RSD values for a sequence of eight injections between 5.5 and 7.7% for peak areas and lower than 1% for migration times. In addition, inter-day precision was evaluated for sixteen injections (a sequence of four injections performed during four days), and the RSD values were lower than 11.5 and 4.9% for peak areas and migration time, respectively. Five produced water samples were analyzed, and it was possible to detect and quantify 9-anthracenecarboxylic acid. The concentrations ranged from 1.05 to 2.24 mmol L−1 with recovery values between 90.8 and 96.0%. ME-C4D demonstrated satisfactory analytical performance for determining naphthenic acids in produced water for the first time, which is useful for petroleum or oil industry investigation.

Analytical characterization of choline chloride in oilfield process waters and commercial samples by capillary electrophoresis

In this study, a rapid and sensitive method using capillary electrophoresis with indirect UV detection and minimal sample pretreatment was developed and evaluated to analyze choline chloride in oilfield process water samples. To improve peak resolution and separation of choline chloride from other cations present in the samples, the addition of a cationic visualization agent in the background electrolyte, imidazole, and a complexing agent, 18-crown-6, were introduced. Other factors affecting separation and sensitivity were also investigated. Under optimized conditions, choline chloride was baseline separated (<7 min) from common cationic adulterants in commercial choline chloride products with a peak resolution of >1.5 between adjacent peaks. The limits of detection (signal-to-noise ratio = 3) and quantitation (signal-to-noise ratio = 10) were 14.7 and 48.9 mg L−1, respectively. The peak area and migration time’s intraday and interday precision (percent RSD) were all <15%, and the recoveries ranged from 79.4% to 115.2% at different spiking levels. Finally, statistical (Student’s t-test) comparison of the choline chloride content data of oilfield process water samples from the proposed capillary electrophoresis (CE) method compare favourably with traditional methods such as liquid chromatography – mass spectrometry (LC–MS) and Reinecke salt gravimetry.

A Capillary Electrophoresis-Based Method for the Measurement of Hydroxychloroquine and Its Active Metabolite Desethyl Hydroxychloroquine in Whole Blood in Patients with Rheumatoid Arthritis.

A capillary electrophoresis method was developed to detect and measure hydroxychloroquine (HCQ) and its active metabolite desethyl hydroxychloroquine (DHCQ) in whole blood in patients with rheumatoid arthritis. The best separation in terms of peak area reproducibility, migration time, peak shape, and resolution of adjacent peaks was obtained in a 60 cm, 75 µm i.d. uncoated fused-silica capillary using a background electrolyte mixture of an aqueous 55 mmol/L TRIS solution brought to pH 2.6 with phosphoric acid and methanol (85:15) and a voltage and a temperature of separation of 20 kV and 30 °C, respectively. Analytes were separated in less than 12 min, with excellent linearity (R2 ≥ 0.999) in the concentration range of 0.5–8 µmol/L. The recovery of analytes spiked in whole blood was 99–101% for HCQ and 98–99% for DHCQ. Analysis of five samples from patients with rheumatoid arthritis receiving HCQ 400 mg daily yielded mean steady-state concentrations of 2.27 ± 1.61 and 1.54 ± 0.55 μmol/L for HCQ and DHCQ, respectively, with a HCQ to DHCQ ratio of 1.40 ± 0.77.

Changes in waterfowl migration phenologies in central North America: Implications for future waterfowl conservation.

Globally, migration phenologies of numerous avian species have shifted over the past half-century. Despite North American waterfowl being well researched, published data on shifts in waterfowl migration phenologies remain scarce. Understanding shifts in waterfowl migration phenologies along with potential drivers is critical for guiding future conservation efforts. Therefore, we utilized historical (1955–2008) nonbreeding waterfowl survey data collected at 21 National Wildlife Refuges in the mid- to lower portion of the Central Flyway to summarize changes in spring and autumn migration phenology. We examined changes in the timing of peak abundance from survey data at monthly intervals for each refuge and species (or species group; n = 22) by year and site-specific temperature for spring (Jan–Mar) and autumn (Oct–Dec) migration periods. For spring (n = 187) and autumn (n = 194) data sets, 13% and 9% exhibited statistically significant changes in the timing of peak migration across years, respectively, while the corresponding numbers for increasing temperatures were 4% and 9%. During spring migration, ≥80% of significant changes in the timing of spring peak indicated advancements, while 67% of significant changes in autumn peak timing indicated delays both across years and with increasing temperatures. Four refuges showed a consistent pattern across species of advancing spring migration peaks over time. Advancements in spring peak across years became proportionally less common among species with increasing latitude, while delays in autumn peak with increasing temperature became proportionally more common. Our study represents the first comprehensive summary of changes in spring and autumn migration phenology for Central Flyway waterfowl and demonstrates significant phenological changes during the latter part of the twentieth century.

CE with Cu2+ ions and 2-hydroxypropyl-β-cyclodextrin additives for the investigation of amino acids composition of the culture medium in a cellular model of non-alcoholic fatty liver disease

CE method with CuSO4 and 2-hydroxypropyl-β-cyclodextrin additives in sodium acetate background electrolyte pH 4.3 for the simultaneous determination of amino acids and lactic acid was adapted for the comparative study of metabolism in "healthy" and non-alcoholic fatty liver disease model cells HepG2. In vitro model of the disease was developed by exposure HepG2 cells with oleate and palmitate to simulate an excessive flow of fatty acids into hepatocytes. The model was proven to be consistent with the disease pathophysiology, since intracellular triglyceride and cytokine interleukin 8 levels were increased, while cells viability was decreased. In order to check whether the metabolism of amino acids changes in pathology, we proposed sample preparation of culture medium and characterized the CE method by evaluating linear dynamic range, repeatability and intermediate precision of peak areas and migration times, accuracy (recovery rate and trueness estimated by reference method), detection limits and quantitation limits. The method proved to be sensitive, reliable and highly accurate for the quantitation of amino acids and lactic acid. The concentrations of amino acids in the culture medium of healthy and the disease model cells were measured and altered levels of Arg, Ala, Glu, Gln and lactic acid have been found in comparison to health control.

Determination of the enantiomers of salmeterol xinafoate in salmeterol fluticasone powder inhalant by chiral nonaqueous capillary electrophoresis

昔萘酸沙美特罗是目前治疗哮喘夜间发作和哮喘维持治疗的理想药物之一,它在临床上以外消旋体形式给药。昔萘酸沙美特罗的两个对映体在药理活性和毒理作用等方面差异较大,建立昔萘酸沙美特罗对映体的手性分离分析方法对提高手性药物质量、保证临床用药安全有效具有重要意义。该文以L(+)-酒石酸-硼酸络合酸为手性选择剂,建立了测定沙美特罗替卡松粉吸入剂中昔萘酸沙美特罗对映体含量的非水毛细管电泳法。实验考察了L(+)-酒石酸浓度、硼酸浓度和表观pH(apparent pH, pH* )对手性分离效果的影响。优化的缓冲溶液为:含120.0 mmol/L L(+)-酒石酸和120.0 mmol/L硼酸的甲醇溶液,pH* 为0.93;其他实验条件为:未涂层弹性熔融石英毛细管(内径50.0 μm,总长度64.5 cm,有效长度55.5 cm),重力进样17.5 cm×10.0 s,检测波长225 nm,室温,工作电压20.0 kV。在优化的实验条件下,昔萘酸沙美特罗的两个对映体在18.0 min内获得了2.18的分离度;在27.5~800.0 mg/L质量浓度范围内,与峰面积呈现良好的线性关系,相关系数(r)大于0.9990;检出限和定量限分别为7.5和25.0 mg/L;加标回收率为98.1%~101.9%,相对标准偏差为1.2%~1.9%。随机购买市面上出售的沙美特罗替卡松粉吸入剂,对其昔萘酸沙美特罗对映体的含量进行了分析检测。结果显示,昔萘酸沙美特罗对映体1和对映体2的标示量百分含量均为98.7%, RSD分别为2.5%和2.7%。该方法操作简便易行,结果准确可靠,消耗低,可用于市售沙美特罗替卡松粉吸入剂中昔萘酸沙美特罗对映体的含量测定。

Study on development of an analytical procedure to quantify glyphosate by capillary electrophoresis method and its application for beverage

Nowadays, the issue of fresh food, drinks, and residue analysis of toxic compounds in food and drinks is increasingly interested in society. In this study, an analytical procedure for quantitative analysis of the glyphosate residue in beverages such as tea infusion and beer was developed based on the capillary electrophoresis method with capacitively-coupled contactless conductivity detector combined with sample preparation using solid phase extraction technique. The analytical conditions optimised for capillary electrophoresis equipment included: histidine/acetic acid background electrolyte solution with histidine concentration of 1 mM and pH value was adjusted to 2.75 by acetic acid; a separation voltage was 20 kV was applied and a high voltage injection at 20 kV for 10 seconds was chosen. The optimised analytical procedure has resulted in a low detection limit of glyphosate (0.42 μg/l), the repeatability and reproducibility expressed by the relative standard deviation of the peak area and migration time were both less than 10%, a wide linear range, and the obtained recovery efficiency of glyphosate on different drinks were achieved to values ranging from 88.7 to 96.3%.

Characterization of capillary inner surface conditions with streaming potential.

Streaming potential is created when an electrolyte solution is forced to flow pass a charged surface. For an uncoated fused silica capillary, the streaming potential is measured between the inlet and outlet vials while applying a pressure across the capillary. The changes in streaming potential can be used to characterize the properties of the capillary inner surface. In this work, HCl, NaCl, and NaOH solutions ranging from 0.4 to 6mM were used as the background electrolyte (BGE) at temperatures of 15 to 35 °C for the mesurements. The streaming potential decreases with the increase in BGE concentration, and the trend is amplified at higher temperatures. When buffer solutions in the pH range of 1.5 to 12.7 were used as the BGE, streaming potential was shown to be sensitive to changes in pH but reaches a maximum at around 9.5. At pH <3.3, no streaming potentials were observed. The pH of zero surface charge (streaming potential equals 0) changes with temperature, and is measured to be 3.3 to 3.1 when the temperature is changed from 15 to 35°C. Zeta potentials can be calculated from the measured streaming potential, conductivity, and the solution viscosity. Surface charge densities were calculated in this work using the zeta potentials obtained. We demonstrated that capillary surface conditions can significantly change the streaming potential, and with three different solutions, we showed that analyte-dependent adsorption can be monitored and mitigated to improve the peak symmetry and migration times reproducibility.

A novel method of reversed migration capillary electrophoresis for determination of linear alkylbenzene sulfonates

A reversed migration capillary electrophoresis (RMCE) has been developed to determine linear alkylbenzene sulfonates (LAS). The sample stacking and separation conditions have been systematically investigated and optimized under reversed separation voltage at a low pH value. The separation effect of LAS homologs has been greatly improved based on the relative motion of electrophoresis and electroosmotic flow. RMCE demonstrates a good linear range of 0.1 mg/l to 10.0 mg/l, and the detection limit of LAS homologs reaches 0.001–0.004 mg/l. The relative standard deviations (n=6) of peak area and migration time were 2.25–4.40% and 0.67–0.75%, respectively. RMCE has also been applied for LAS detection in practical wastewater. The results show RMCE exhibits easy pretreatment, fast detection, high sensitivity, good peak shapes and resolution, and less solvent consumption, compared with the established high-performance liquid chromatography method.

Covalent cationic copolymer coatings allowing tunable electroosmotic flow for optimization of capillary electrophoretic separations

Electroosmotic flow (EOF) plays a pivotal role in optimization of capillary electrophoresis (CE) separations of (bio)molecules and (bio)particles. EOF velocity is directly related to analysis time, peak resolution and separation efficiency. Here, we report a concept of charged polymer coatings of the inner fused silica capillary wall, which allows anodic EOF with mobility ranging from 0 to ∼(30–40) × 10−9 m2V−1s−1. The capillary wall is modified by covalently bound cationic copolymer poly(acrylamide-co-(3-acrylamidopropyl)trimethylammonium chloride) (PAMAPTAC) containing variable ratio of the charged monomer in the 0–60 mol. % interval. The EOF mobility showed minor variability with composition of background electrolyte (BGE) and pH in the 2–10 interval. The coatings were evaluated by CE-UV and nanospray CE-MS in the counter-EOF arrangement for a series of basic drug molecules in acetic acid based acidic BGE. Tunable EOF velocity was demonstrated as a useful tool for optimization of peak resolution, separation efficiency and migration time of analytes. Electrostatic repulsion of positively charged capillary surface was shown as beneficial for suppression of analyte adsorption, notably for hydrophobic cationic analytes.

Identifying i-motif formation using capillary electrophoresis.

Over the past few years, intercalated motifs (i-motifs) have attracted attention due to the direct visualization of their existence in the nuclei of human cells. Traditionally, i-motifs have been studied using expensive and complicated NMR, and/or relatively inexpensive but less common circular dichroism spectrometry. The aim of this study was to investigate the feasibility of using less expensive, less complicated, and more widely available CE as an alternative for i-motif related research. The mobilities of two DNA and RNA i-motifs in CE were determined under different pH conditions. Our results demonstrate that CE is able to identify and differentiate mostly folded, partially folded, and mostly unfolded DNA and RNA i-motifs through changes in peak shape and migration time, thus providing a new method to study both i-motif conformation and the interactions between i-motifs and their ligands.

Analysis of selenium nanoparticles in human plasma by capillary electrophoresis hyphenated to inductively coupled plasma mass spectrometry.

Nanoparticles (NPs) are increasingly applied in research and development of new therapies. Characterization of NP systems most often include size, shape, size distribution, and charge but information on the chemical stability of NPs and investigation of the presence of dissolved species is most often missing in efficacy studies due to lack of appropriate methods. In this study, a method based on capillary electrophoresis coupled to inductively coupled plasma mass spectrometry (CE-ICP-MS) was established for analysis of selenium (Se) NPs and dissolved Se species in aqueous media. Peak area and migration time precisions (RSD) of 1.4-3.0% and 1.0-2.6%, respectively, were obtained. CE-ICP-MS analysis of a commercially available SeNP suspension (Q-SeNP) revealed large amounts of selenite corresponding to 32% of the total Se content in the suspension, indicating considerable NP degradation upon storage. The CE-ICP-MS method was modified using a coated fused silica capillary in order to analyze SeNPs in human plasma. Peak area and migration time precisions (RSD) in the range of 3.3-10.7% and 0.8-2.8%, respectively, were achieved. Degradation of polyvinyl alcohol (PVA)-coated SeNPs to selenite in human plasma was demonstrated using the modified method. The amounts of SeNP and selenite were estimated based on a correction factor for the ICP-MS signals of PVA-SeNP and dissolved Se. To the best of our knowledge, this is the first study of SeNPs by CE-ICP-MS and highlights the potential of CE-ICP-MS for quantitative characterization of the behavior of SeNPs in biological media.

Qualitative determination of chiral compounds using capillary electrophoresis

As a well-established analytical separation technique, capillary electrophoresis (CE) is widely used in the separation of chiral substances because of its numerous advantages such as high separation efficiency, short analysis time, small sample dosage, and flexible separation modes. In the previous studies, the CE separation mode, selection of the chiral dispersant and improvement of the separation degree of chiral compounds have been reported in detail. Moreover, it is important to determine the quality of chiral substances and confirm the order of enantiomer peaks after successful separation. This paper summarizes the qualitative detection methods for CE chiral compounds, based on whether the separation analysis of chiral compounds depends on the classification of standard materials. There are two common methods for the qualitative determination of chiral substances in CE. One method compares the difference in the peak migration time, while the other compares the change in peak area before and after the addition of a single enantiomer standard. Both methods are accurate and simple to operate. A diverse range of detectors are used in CE. Based on the type of detector, CE analysis based on standard products is divided into optical, mass spectrometric and electrochemical detection modes. Optical detection involves the use of ultraviolet-visible (UV-vis), laser-induced fluorescence (LIF), chemiluminescence (CL) and other detectors. Among these, the UV detector has the advantages of stable performance, simple structure, and high cost performance and it is most widely used in CE detection as one of the fixed commercial detectors. The LIF detector is a kind of fluorescence detector with a laser as an excitation source. It has the advantages of low background and high signal-to-noise ratio, which make it the most sensitive CE detector. However, this detector is expensive and the sample must be able to provide a fluorescence signal. Otherwise, it is necessary to use a derivatization reagent for sample pretreatment, which renders the analysis complicated. The type of detector leads to a difference in the sample pretreatment, and the resulting spectra and qualitative methods for chiral compounds are also widely different. Therefore, we must choose the most suitable detector to be combined with CE depending on the sample properties and experimental requirements. The above mentioned methods require at least one chiral molecular standard of one configuration. However, for many chiral enantiomers, especially some novel chiral drugs, there is no single commercially available standard enantiomer, and even if there is one, it is very expensive. In this case, the available CE chiral separation methods include enzyme digestion, addition of antibodies, and computational methods. Enzyme digestion entails the addition of refers to adding the corresponding degrading enzyme or oxidase into the tested sample, so that qualitative analysis is possible by observing the change in peak area. In the method based on antibody addition, it is necessary to find antibodies that respond to a single enantiomer. Nevertheless, it is difficult to acquire the corresponding digestion enzymes or specific antibodies for most chiral molecules. Hence, the application scope of these two methods is limited. On the other hand, the computational method is a chiral qualitative method that is rapid, economical, and simple to operate, with a wide range of applications. This technique combines the circular dichroism (CD) spectroscopy with theoretical calculations within the premise of CE separation. The underlying principle of this method covers two aspects. On the one hand, all chiral compounds can give CD signals, and a racemic mixture of isomers gives equal signals but with opposite signs. However, in the case of a non-racemic chiral isomer mixture, only the CD signal of the dominant isomers observed. Using the time-dependent density functional theory (TDDFT), the theoretical CD spectrum of a single isomer can be obtained. By comparing the theoretical and experimental spectra, the configuration of the dominant enantiomer is determined. On the other hand, the peak area in electrophoresis is linearly related to the enantiomeric excess in the CE spectrum. By combining CE with CD, accurate separation and qualitative detection of chiral substances can be easily achieved. The method of calculation, independent of the standard, will greatly promote the development of chiral molecular analysis.