Fused-silica Capillary Research Articles

Method Development, Optimization, and Validation of the Separation of Ketamine Enantiomers by Capillary Electrophoresis Using Design of Experiments

Capillary electrophoresis was chosen as cost-effective and robust method to separate ketamine enantiomers. For the method development, first different native and modified cyclodextrins were tested. The most promising chiral selector was α-cyclodextrin. A design of experiments (DoE) was carried out, which started with the screening of relevant factors. Based on these results, the method was optimized according to the significant factors (buffer, cyclodextrin concentration, pH value, voltage, temperature) of the screening based on the response resolution and migration time of the later migrating enantiomer. The optimized conditions consisted of a background electrolyte with 275 mM TRIS, adjusted with 85% phosphoric acid to a pH of 2.50, and 50 mM α-cyclodextrin, at a temperature of 15 °C, an applied voltage of 30 kV and an injection pressure of 1.0 psi for 10 s. A fused-silica capillary with a total length of 70 cm and an effective length to the detector of 60 cm was used. The method was validated according to ICH guideline Q2 R(1). The limit of quantification was 3.51 µg mL−1 for S-ketamine and 3.98 µg mL−1 for R-ketamine. The method showed good linearity for racemic ketamine with R2 of 0.9995 for S-ketamine and 0.9994 for R-ketamine. The lowest quantifiable content of S-ketamine found in R-ketamine was 0.45%.

Capillary gel electrophoresis of very high molecular weight glycoproteins. Commercial and tailor-made gels for analysis of human monomeric and secretory immunoglobulin A

Capillary gel electrophoresis (CGE) has been widely used for analysis of proteins according to their size. However, to our knowledge, this technique has not been optimized to immunoglobulin A (IgA) analysis, a protein of current and emerging high interest in several fields. IgA is the first barrier of human body against pathogens. This protein in human milk and colostrum is essential for immune protection of newborns and treatment of milk for storage in Human Milk Banks may alter IgA. The emerging use of IgA as therapeutic treatment also encourages the development of analysis methods for this class of immunoglobulins.IgA is far more heterogeneously glycosylated and complex than the well-studied IgG molecules. IgA in serum is mainly monomeric (mIgA) with about 160 kDa, while in secretions such as saliva, milk, colostrum, etc, secretory immunoglobulin A (sIgA) is the predominant form. This is a dimer where both monomers are linked by the J-chain and the secretory component accounting all together for a MW higher than 400 kDa including the glycans. This size is far from the 225 kDa MW for which commercial CGE kits are intended.The general rules governing CGE behavior of analytes cannot be directly applied to every protein. Addressing studies directed specifically to target proteins is specially needed for the large size and highly complex target analytes of this study. In this work the effect of several factors on CGE analysis of human serum and colostrum IgA is studied. The feasibility of performing analysis of both IgA classes using a commercial CGE kit is shown. In addition, this work introduces another novelty by preparing tailor-made reproducible gel buffers and to characterize them in terms of dynamic viscosity, conductivity, and electroosmotic flow mobility in bare fused silica capillaries. The possibility of analyzing mIgA and sIgA in less than 10 min using these tailor-made gels is demonstrated. Inter-day variation (RSD) for the main peak of sIgA is 0.25% for migration time (tm) and 0.27% for percentage corrected peak area (Acorr).

Integration of a fused silica capillary and in-situ Raman spectroscopy for investigating CO2 solubility in n-dodecane at near-critical and supercritical conditions of CO2

To determine the solubility of CO 2 in n -dodecane at T = 303.15–353.15 K, P ≤ 11.0 MPa, an integrated fused silica capillary and in-situ Raman spectroscopy system was built. The Raman peak intensity ratio ( I CO 2 / I C - H ) between the upper band of CO 2 Fermi diad ( I CO 2 ) and the C–H stretching band of n -dodecane ( I C - H ) was employed to determine the solubility of CO 2 in n -dodecane based on the calibrated correlation equation between the known CO 2 molality in n -dodecane and the I CO 2 / I C - H ratio with R 2 = 0.9998. The results indicated that the solubility of CO 2 decreased with increasing temperature and increased with increasing pressure. The maximum CO 2 molality (30.7314 mol/kg) was obtained at 303.15 K and 7.00 MPa. Finally, a solubility prediction model ( ln S = ( P − A ) / B ) based on the relationship with temperature ( T in K) and pressure ( P in MPa) was developed, where S is CO 2 molality, A = − 8 × 10 − 6 T 2 + 0.0354 T − 8.1605 , and B = 0.0405 T − 10.756 . The results indicated that the solubilities of CO 2 derived from this model were in good agreement with the experimental data.

Easy to assemble dielectric barrier discharge plasma ionization source based on printed circuit boards

Here, we present a new and an easy to assemble dielectric barrier discharge plasma ionization source based on printed circuit boards with two parallel isolated electrodes for generating a plasma inside an inert fused silica capillary. For demonstration, this plasma source is coupled to an ion mobility spectrometer. With two different sample gas feeds the analytes can either pass through the plasma or bypass the plasma before entering the reaction region of the ion mobility spectrometer, allowing for different ionization pathways, e.g. electron impact ionization, ionization by excited species, e.g. helium metastables, or chemical ionization via reactant ions generated inside or downstream of the plasma. The plasma source, in particular, the electrode geometry and the capillary diameter were designed with the help of electric field simulations. A rectangular electrode with a height of at least twice the outer diameter of the capillary turned out to be ideal, in both the simulation and the experiment. Furthermore, a simple control electronics has been developed, which can be easily applied to other plasma sources. With the plasma source presented here, detection limits in the mid pptv range have been reached.

An improved design of the fused silica capillary flow cell for absorbance detection in microcolumn liquid chromatography

Efficient absorbance detection of a low-volume chromatography peak is a difficult task. In this work, an improved design of the fused silica capillary flow cell for absorbance detection in microcolumn liquid chromatography is described. The cell was fabricated from 0.15 mm I. D. fused silica capillary and silica optical fibres. Optical fibres were fully integrated into the cell design and enabled a convenient and effective connection of the cell with the light source and light detector (265 nm UV LED and photodiode in this work). Manufactured cells covered the range of physical lengths 3.1–9.9 mm (55–175 nL) and were used without any focusing optics and slits. Baseline noise was typically below 0.05 mAU and the effective optical path determined in the experiments was 83–97% of the cell's physical length. The level of stray (parasitic) light indicated by a 1% deviation from linearity at 1.7 AU was 0.08% only. The proposed cell design was found to be moderately susceptible to the refractive index change (20–35 mAU baseline change in 5–95% (v/v) gradient of acetonitrile or methanol in a mixture with water, G index up to 4 AU·s/RIU). Manufactured cells were finally applied for absorbance detection of components of test the mixture eluted off 0.3 mm I. D. microcolumn. 9.9 mm cell (175 nL) with an effective optical path of 8.9 mm exhibited contribution to the broadening of chromatography peak comparable with commercial 6 mm (80 nL) rectangular flow cell.

Implementation of two sustainable chromatographic methods for the simultaneous micro-quantitation and impurity profiling of metformin and rosuvastatin in recently approved fixed dose pills: Greenness and whiteness studies

Rosuvastatin-Metformin is an emerging fixed dose combination (FDC) for the treatment of diabetes mellitus-associated dyslipidemia. Generally, the beneficial outcomes of FDC in reduction of pills burden, cost and complexity of medications protocols, encouraged analysts and we in turn for the development of rapid sustainable analytical methods for the simultaneous estimation of such important drug combinations. Within this framework, two validated analytical methodologies have been implemented for the neat separation and quantitation of metformin (MET) and rosuvastatin (RSV) in presence of the pharmacopeial impurities cyanoguanidine (CYG) (impurity A of MET) and the rosuvastatin-related substance B (RSV-impurity B). The latter was freshly prepared and then confirmed using Liquid Chromatography-Mass spectrometry (LC-MS). Method I represented the first electro-driven separation method for the assay of this FDC using Micellar Electrokinetic Chromatography (MEKC). The optimized conditions were 50 mM borate buffer containing 100 mM sodium dodecyl sulfate (SDS) at pH 9.2 using a deactivated fused silica capillary (50 cm effective length × 50 μm id). Method II was High Performance Liquid Chromatography (HPLC) method using Microsorb MV-C18 (4.6 × 250 mm, 5 μm particle size) column with 20 mM sodium dihydrogen phosphate buffer (pH 3.5), acetonitrile and methanol as mobile phase constituents. The separation was achieved with a linear gradient program and flow rate 1.5 mL/min all over the run. The Diode Array Detector (DAD) detector was set at wavelengths 243 nm for RSV and 235 nm for MET in both methods. The 4 peaks were separated in about 8 and 5 min for methods I and II, respectively. Linear relationships were obtained between peak areas and concentrations of metformin and rosuvastatin in the ranges 10–100 μg/mL for MEKC and 1–150 μg/mL for HPLC. The 2 techniques fulfilled the International Council for Harmonization (ICH) validation criteria, as well as the green and white analytical chemistry principles which were evaluated using the trendiest AGREE, hexagon and RGB12 tools. The interpretation of scores indicated that the suggested methods outperformed the reported methods in terms of eco-friendliness and sustainability. They offered fast, feasible, stability indicating and accurate analysis of both drugs in bulk and in pills.

Heroin detection in a droplet hosted in a 3D printed support at the miniaturized electrified liquid-liquid interface

Simple sensing protocols for the detection of illicit drugs are needed. Electrochemical sensing is especially attractive in this respect, as its cost together with the analytical accuracy aspires to replace still frequently used colorimetric tests. In this work, we have shown that the interfacial transfer of protonated heroin can be followed at the electrified water-1,2-dichloroethane interface. We have comprehensively studied the interfacial behavior of heroin alone and in the presence of its major and abundant cutting agents, caffeine and paracetamol. To maximally increase developed sensing protocol applicability we have designed and 3D printed a platform requiring only a few microliters of the aqueous and the organic phase. The proposed sensing platform was equipped with a cavity hosting a short section of Ag/AgCl electrode, up to 20 µL of the aqueous phase and the end of the micropipette tip being used as a casing of a fused silica capillary having 25 µm as the internal pore diameter. The volume of the organic phase was equal to around 5 µL and was present inside the micropipette tip. We have shown that under optimized conditions heroin can be detected in the presence of caffeine and paracetamol existing in a sample with 10,000 times excess over the analyte of interest. The calculated limit of detection equal to 1.3 µM, linear dynamic range spanning to at least 50 µM, good reproducibility, and very low volume of needed sample is fully in line with forensic demands.

Simultaneous Determination of Nicotine and Phenolic Compounds in Tobacco by Capillary Electrophoresis with Pipette Tip Electrodes

Aim: The aim of this work is to fabricate pipette tip electrodes for the capillary electrophoretic determination of nicotine and phenolic compounds in tobacco. Background: The content of nicotine affects not only the quality of tobacco products but also the health of smokers. Phenolic compounds are important flavor precursors in tobacco. The quantity of phenolic compounds is one of the most important evaluation indicators of tobacco quality. It is of high importance to determine nicotine and phenolic compounds in tobacco for quality control and the health of smokers. Objective: A method based on capillary electrophoresis and amperometric detection was developed for the simultaneous determination of nicotine, rutin, chlorogenic acid, quercetin, ferulic acid, gallic acid, and protocatechuic acid in tobacco leaves. Pipette electrodes were designed and fabricated for their amperometric detection. Method: Nicotine, rutin, chlorogenic acid, quercetin, ferulic acid, gallic acid, and protocatechuic acid were determined by capillary electrophoresis in combination with the detection electrodes that were fabricated by packing the composite of carbon nanotube and epoxy in pipette tips. Results: Detection potentials, the acidity and concentrations of background electrolyte, separation voltages, and injection times were optimized. At a high voltage of 12 kV, separation of the seven analytes could be achieved in less than 11 min in a piece of 40 cm long fused silica capillary with a background electrolyte of 50 mM borate buffer (9.2). Linearity was observed between the peak currents and the concentrations, with the limits of detection ranging from 0.1 to 0.2 μM for the seven analytes at the pipette electrodes. The method was applied in the simultaneous determination of nicotine and phenolic compounds with satisfactory assay results. Conclusions: The pipette tip electrodes were successfully coupled with capillary electrophoresis for tobacco analysis. The CE-AD method provides not only a simple approach for the quality control of tobacco and its preparations but also an alternative technique for the constituent and fingerprint investigation of other plants.

Simultaneous determination of vitamin B6 and magnesium using capillary electrophoresis coupled with contactless conductivity detection: Method development, validation, and application to pharmaceutical and nutraceutical samples

Vitamins and minerals are usually incorporated in pharmaceutical and nutraceutical products, but a simple, rapid, and inexpensive analytical method for their simultaneous determination is still lacking. In this study, we developed a quantification method for pyridoxine (vitamin B6) and magnesium (Mg) by using purpose-made capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D) instrument. Main analytical conditions include: fused silica capillary (total length 55 cm, effective length 40 cm, inner diameter 50 μm); background electrolyte consisted of 10 mM L-arginine/acetic acid (pH 5) with 20% acetonitrile; separation voltage + 20 kV; hydrodynamic injection (siphoning at 20 cm in 25 s). Detection limits of vitamin B6 and Mg were 1 and 0.1 mg/L, respectively. Good linearity (R2 > 0.999) was observed for vitamin B6 and Mg calibration curves over concentration ranges of 3–100 and 0.3–200 mg/L, respectively. The method was applied to analyze vitamin B6 and Mg in several pharmaceutical and nutraceutical samples. The analytical results obtained by our method were in good agreement with reference methods (i.e., HPLC for vitamin B6 and ICP-OES for Mg). High-efficient and low-cost CE-C4D method can accordingly serve as a promising tool for concurrent analysis of inorganic and organic species in pharmaceutical and nutraceutical analysis.

Covalent anionic copolymer coatings with tunable electroosmotic flow for optimization of capillary electrophoretic separations.

We present a method for finely adjustable electroosmotic flow (EOF) velocity in cathodic direction for the optimization of separations in capillary electrophoresis. To this end, we use surface modification of the separation fused silica capillary by the covalently attached copolymer of acrylamide (AM) and 2-acrylamido-2-methyl-1-propanesulfonate (AMPS), that is, poly(AM-co-AMPS) or PAMAMPS. Coatings were formed by the in-capillary polymerization of a mixture of the neutral AM and anionic AMPS monomers premixed in various ratios in order to control the charge density of the copolymer. EOF mobility varies in the 0 to ∼40×10-9 m2 V-1 s-1 interval for PAMAMPS coatings ranging from 0 to 60mol.% of charged AMPS monomer. For EOF in PAMAMPS-treated capillaries, we observed (i) a negligible dependence on pH in the 2-10 interval, (ii) a minor variance among background electrolytes (BGEs) in function of their components and (iii) its standard decrease with increasing ionic strength of the BGE. Interest in variable cathodic EOF was demonstrated by the amelioration of separation of two kinds of isomeric anionic analytes, that is, monosaccharides phosphates and helquat enantiomers, in counter-EOF mode.

Triazole-based covalent gels assembled from small molecules with superior stability for supported catalysis in a monolithic microfluidic reactor

A novel catalysis-assisted gelation strategy is exploited to assemble a catalogue of covalent gels with superior stability from small molecules via strong covalent bonding. Triazole-based covalent gels with hierarchical porous structure and large surface area are fabricated based on copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) polymerization between 1,4-diazidobenzene (A1) and tetrakis(4-ethynylphenyl)methane (B1) /2,2',7,7'-tetraethynyl-9,9'-spirobifuorene (B2) (denoted as triazole-A1B1 and -A1B2 gels). The BET specific surface areas of the triazole aerogels are up to 368 m2 g-1. The triazole gels show superior chemical stability, offer the hierarchical porous structure and rich triazole coordination sites for metal nanoparticles immobilization, and can therefore serve as catalyst supports. A range of metal nanoparticles are readily supported in the gels after wet impregnation and reduction. Among them, Ru nanoparticles are anchored within the gel matrix with small nanoparticle size of 2.95 nm. A microfluidic reactor is fabricated by loading Ru@triazole-A1B2 gel monolith in fused-silica capillary. The triazole-A1B2 gel and Ru@A1B2 gel monoliths have high permeability of 2.27 × 10-11 m2 and 1.59 × 10-11 m2, respectively. The Ru@triazole-A1B2 microfluidic reactor achieves high catalytic activity and selectivity, and ultrafast flow synthesis is developed for the reduction of nitrobenzene derivatives to the corresponding anilines with maximum conversion of 91.8 % and 87.3 % selectivity within 25 s. The reactor shows superior stability and the conversion of nitrobenzene remains above 92 % during 60 h of continuous-flow catalytic reaction.

Capillary electrophoretic methods for classification of methicillin-resistant Staphylococcus aureus (MRSA) clones

This study describes differentiation of methicillin-resistant Staphylococcus aureus (MRSA) isolates belonging to different genotype groups by the combination of electrophoretic techniques, transient isotachophoresis and micellar electrokinetic chromatography. MRSA isolates were separated in fused silica capillary with roughened inner surface prepared by etching with supercritical water. Separation temperature together with the rinsing procedure of the capillary turned out to be the key factors of successful analysis. The individual genotype groups were baseline-resolved in 40 min. Partial separation of the individual isolates within the groups was also observed. Relative standard deviations of the migration times of the isolate zones ranged from 0.32 to 0.79%. In addition, capability of the developed CE method to concentrate and separate MRSA isolates in clinical samples was proved by the analysis of blood sample.

Porous capillary monolithic column coupled with ultrahigh performance liquid chromatography-tandem mass spectrometry for fast and effective separation and determination of estrogens

In this work, a porous capillary monolithic column was simply prepared by in situ thiol-alkyne click polymerization of dipentaerythritol hexakis (3-mercaptopropionate) and dimethyl dipropargylmalonate in fused-silica capillary. The capillary monolithic column shows excellent permeability, high porosity, and thoiether-rich groups, thereby, a high-efficient capacity for trace estrogens from complex samples are obtained via electron-donor-acceptor π-π interaction and hydrophobic interaction. The highest adsorption efficiency for estrogens is achieved at pH = 7.0 with a flow rate of 0.200 mL min−1. The superior adsorption capacities of the as-prepared capillary column for eight estrogens range from 0.092 mg m−1 to 0.31 mg m−1. A simple, reliable, and sensitive method for the determination of eight estrogens in biological and environmental samples is developed using the monolithic polymer as in-tube solid-phase microextraction coupled with ultrahigh performance liquid chromatography-tandem mass spectrometry (SPME-UPLC-MS/MS), and the total instrumental analysis time for the SPME-UPLC-MS/MS procedures was about 60 min per sample. The developed method shows a wide linear range (0.0500–5.00 μg L−1), and low limits of detection (5.34–9.63 ng L−1) for estrogens. The concentrations of estrogens in serum, urine, and pond water samples are found to be no more than 3.69, 0.741, and 1.04 μg L−1, respectively, and the satisfying recoveries for the eight estrogens range from 80.3% to 113% with relative standard deviations (n = 5) of 1.5–9.4%. The established method is highly potential for extraction and analysis of ultratrace target estrogens in complex matrices, such as biological and environmental samples.

Intentional and unintentional nitrite intoxications: A novel diagnostic strategy based on the direct ion determination by capillary electrophoresis

Discussion of analytical and interpretative aspects of nitrite intoxication in 12 forensic cases. In recent years, a significant increase of reports about suicidal cases due to intentional sodium nitrite intake has been described. Also, accidental poisonings can occur by exposure to contaminated food due to the use of sodium nitrite as a coloring agent or preservative in food, as well as an antimicrobial agent in meat and fish. The human toxicity of nitrite is mainly related to its capability to oxidize the Fe2+ of the hemoglobin to Fe3+, thus converting hemoglobin to methemoglobin, which is unable to bind and transport oxygen. The determination of nitrite in blood is challenging since it is rapidly oxidized to nitrate by hemoglobin. Thus, the diagnosis of nitrite intoxication is generally based on methemoglobin quantification. However, methemoglobin is only an indirect non-specific evidence of nitrite intoxication, as increases of this form of oxidized hemoglobin can be observed in different genetic defects and acquired conditions, including treatment with drugs. Consequently, a specific diagnosis of nitrite intoxication can be achieved only by the direct identification and measurement of the toxic compound or its derivatives. Recently, our research group validated a capillary electrophoresis (CE) method specifically devoted to the direct determination of nitrite/nitrate in biological fluids including postmortem blood (Taus F, et al. Forensic Sci Int 2021;325:110855). The aim of the present study was the discussion of analytical and interpretative aspects of 12 forensic cases of intentional and unintentional nitrite intoxication ( n = 4 fatalities; n = 3 suicidal attempts and n = 5 food intoxications). An automated capillary electrophoresis system Capel-205 (Lumex Instruments, Vancouver, Canada) equipped with a spectrophotometric detector was used. The analyses were carried out on a bare fused-silica capillary (75 mm inner diameter) using 100 mM tetraborate (pH 9.24) as background electrolyte and applying a voltage of - 15 kV. The detection was obtained by direct UV absorption recorded at 214 nm wavelength. All the biological samples (blood, urine and vitreous humour) were, after centrifugation, diluted 1:20 with the internal standard solution (Bromide: 250 μmol/L) prior to injection. Nitrate concentrations in blood ranged from 1400 to 6500 μmol/L in fatalities and from 910 and 2590 μmol/L in the suicide attempts. In food intoxication cases nitrate was always below 400 μmol/L. Nitrite was found only in not quantifiable traces due to its rapid conversion to nitrate. No interferences were observed from sample components, including proteins and ions. The proposed CE method allows for the direct and specific determination of nitrite/nitrate in different biological samples (serum/plasma or urine) as well as in postmortem specimens (cadaveric blood and vitreous humor). These characteristics, in addition to the speed and cheapness of the analysis, make this novel approach particularly suitable for the reliable diagnosis of nitrite intoxication in both clinical and forensic cases.

The First Online Capillary Electrophoresis-Microscale Thermophoresis (CE-MST) Method for the Analysis of Dynamic Equilibria-The Determination of the Acidity Constant of Fluorescein Isothiocyanate.

This article presents the first successful application of a capillary electrophoresis-microscale thermophoresis tandem technique (CE-MST) for determining the values of equilibrium constant, realized by connecting online the CE and MST instruments using a fused-silica capillary. The acid-base dissociation of fluorescein isothiocyanate, expressed by the acidity constant value (pKa), was used as a model. The measurement procedure consisted of introducing a mixture containing the analyte and a deliberately added interferent into the CE capillary, electrophoretic separation of the analyte from the interferent, the detection of the analyte with a CE-integrated detector, detection with a MST detector, and then stopping the flow temporarily by turning off the voltage source to conduct the thermophoretic measurement. The analysis of migration times, peak areas and MST responses obtained concurrently for the same sample allowed us to determine the pKa value using three independent methods integrated within one instrumentation. The analyte was effectively separated from the interferent, and the acidity values turned out to be consistent with each other. An attempt was also made to replace the standard commercial CE instrument with a home-made portable CE setup. As a result, the similar pKa value was obtained, at the same time proving the possibility of increasing cost efficiency and reducing energy consumption. Overall, the CE-MST technique has a number of limitations, but its unique analytical capabilities may be beneficial for some applications, especially when sample separation is needed prior to the thermophoretic measurement.

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.

Nanoflow Sheath Voltage-Free Interfacing of Capillary Electrophoresis and Mass Spectrometry for the Detection of Small Molecules.

Coupling capillary electrophoresis (CE) to mass spectrometry (MS) is a powerful strategy to leverage a high separation efficiency with structural identification. Traditional CE-MS interfacing relies upon voltage to drive this process. Additionally, sheathless interfacing requires that the electrophoresis generates a sufficient volumetric flow to sustain the ionization process. Vibrating sharp-edge spray ionization (VSSI) is a new method to interface capillary electrophoresis to mass analyzers. In contrast to traditional interfacing, VSSI is voltage-free, making it straightforward for CE and MS. New nanoflow sheath CE-VSSI-MS is introduced in this work to reduce the reliance on the separation flow rate to facilitate the transfer of analyte to the MS. The nanoflow sheath VSSI spray ionization functions from 400 to 900 nL/min. Using the new nanoflow sheath reported here, volumetric flow rate through the separation capillary is less critical, allowing the use of a small (i.e., 20 to 25 μm) inner diameter separation capillary and enabling the use of higher separation voltages and faster analysis. Moreover, the use of a nanoflow sheath enables greater flexibility in the separation conditions. The nanoflow sheath is operated using aqueous solutions in the background electrolyte and in the sheath, demonstrating the separation can be performed under normal and reversed polarity in the presence or absence of electroosmotic flow. This includes the use of a wider pH range as well. The versatility of nanoflow sheath CE-VSSI-MS is demonstrated by separating cationic, anionic, and zwitterionic molecules under a variety of separation conditions. The detection sensitivity observed with nanoflow sheath CE-VSSI-MS is comparable to that obtained with sheathless CE-VSSI-MS as well as CE-MS separations with electrospray ionization interfacing. A bare fused silica capillary is used to separate cationic β-blockers with a near-neutral background electrolyte at concentrations ranging from 1.0 nM to 1.0 μM. Under acidic conditions, 13 amino acids are separated with normal polarity at a concentration ranging from 0.25 to 5 μM. Finally, separations of anionic compounds are demonstrated using reversed polarity under conditions of suppressed electroosmotic flow through the use of a semipermanent surface coating. With a near-neutral separation electrolyte, anionic nonsteroidal anti-inflammatory drugs are detected over a concentration range of 0.1 to 5.0 μM.

Progresses in Fluid Inclusion Synthesis in Quartz

High-temperature and high-pressure (HTHP) fluids are one of the most extensive participants in geological events. The representative in situ sampling of the HTHP fluids, which is an essential prerequisite for precisely characterizing the HTHP fluids (including compositional and volumetric properties), has been a vital challenge. The technique of fluid inclusion synthesis (FIS) in quartz is one of the only options. It has experienced an almost 40-year development since the standard fracture healing method was invented. Considerable advances in our understanding of physicochemical properties of geological fluids and their roles in many geological processes have been achieved by the use of the FIS techniques. A set of methodologies for fluid inclusion synthesis have been established. Great progresses have also been made, which includes the various pretreatment FIS techniques, the in situ fracturing FIS technique closely associated with the HTHP apparatus, the in situ fracturing refilled FIS technique for large fluid inclusion synthesis at controlled time under unfavorable conditions, and the novel fluid inclusion synthesis by fused silica capillary. Such great many progresses of the quartz FIS techniques have been scattered in the geochemists’ individual research work, and systematic collection and objective evaluation are missing. Consequently, we synthesize existing research, describe and identify the basic operations, discuss the methodological issues like pros and cons, and highlight the problems and prospects of the quartz FIS techniques. Furthermore, it is suggested that in situ and (or) large volume fluid inclusion synthesis will be an important future direction in view of the growing applications of the FIS techniques in combination with microanalytical techniques, especially the Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). Our review would provide technical guidance to those who wish to investigate HTHP fluids and be beneficial to the future development and applications of the FIS techniques.

Profiling protein interactions by purification with capillary monolithic affinity column in combination with label-free quantitative proteomics

An approach for profiling protein-protein interactions by using affinity purification with capillary monolithic immobilized metal affinity chromatography column (cm-IMAC) in combination with label free quantitative proteomics was described in the present work. The cm-IMAC columns were prepared in a single step by copolymerization of the function monomer, namely (S)-2,2′-((1-carboxy-5-(pent‑4-enamido)pentyl)azanediyl)diacetic acid which provide a nitrilotriacetate (NTA) moiety to form chelated complexation with Ni (II) ions, inside the fused silica capillaries. The His6-tagged bait protein can be easily immobilized on the cm-IMAC columns through the formation of chelating complexation with the NTA-Ni (II) functional groups of the matrix. The cm-IMAC columns were used to explore protein-protein interactions (PPIs) on a proteomic scale when combined with label-free proteomics. A known interaction pair of proteins, namely NDP52 (amino acid sequence 10–126) and NAP1 (33–75) as well as Bcl-2 family proteins were used for proof of concept. New interactors of Bcl-XL were identified and validated by co-immunoprecipitation.

Determination of sulfonamide residues in cultured sea cucumber by pre-column derivatization capillary electrophoresis with fluorescence detection

A simple and mild method for the separation of sulfonamide residues based on a condensation reaction with O-phthalaldehyde solution (OPA) as labeling reagent with capillary electrophoresis has been developed. A 58.5 cm × 50 μm i.d. (50 cm effective length) untreated fused-silica capillary was used. To optimize the separation conditions, the background electrolyte concentration, pH, column temperature, voltage and other factors were evaluated. The optimal separation conditions were as follows: 20 mmol L−1 borate buffer; pH 9.1; column temperature 20 °C; separation voltage 18 kV, pressure 50 mbar and injection time 8 s. Under the optimal conditions, 10 kinds of sulfonamide derivatives could be well-separated within 8 min, and the linear ranges were 0.35–100 μg kg−1. The detection limit (at a signal-to-noise ratio of 3) was in the range of 0.12–0.25 μg kg−1, and the quantification limit (at a signal-to-noise ratio of 10) was in the range of 0.35–0.70 μg kg−1. The sulfonamide residues from cultured sea cucumber samples were determined under the optimal conditions with satisfactory results.