Saccharides form one of the major constituents of biological macromolecules in living organisms. Many biological processes including protein folding, stability, immune response and receptor activation are regulated by glycosylation. In this work, we optimized a capillary electrophoresis method with capacitively coupled contactless conductivity detection for the separation of eight monosaccharides commonly found in glycoproteins, namely D-glucose, D-galactose, D-mannose, N-acetyl-D-glucosamine, N-acetyl-D-galactosamine, D-fucose, N-acetylneuraminic acid, and D-xylose. A highly alkaline solution of 50 mM sodium hydroxide, 22.5 mM disodium phosphate, and 0.2 mM CTAB (pH 12.4) was used as a background electrolyte in a 10 μm id capillary. To achieve baseline separation of all analytes, a counter-directional pressure of -270 kPa was applied during the separation. The limits of detection of our method were below 7 μg/ml (i.e., 1.5 pg or 1 mg/g protein) and the limits of quantification were below 22 μg/ml (i.e., 5 pg or 3 mg/g protein). As a proof of concept of our methodology, we performed an analysis of monosaccharides released from fetuin glycoprotein by acid hydrolysis. The results show that, when combined with an appropriate pre-concentration technique, the developed method can be used as a monosaccharide profiling tool in glycoproteomics and complement the routinely used LC-MS/MS analysis.
- MeSH
- Acetylgalactosamine MeSH
- Acetylglucosamine MeSH
- Cetrimonium MeSH
- Chromatography, Liquid MeSH
- Electrophoresis, Capillary methods MeSH
- Electrolytes chemistry MeSH
- Fetuins MeSH
- Phosphates MeSH
- Fucose MeSH
- Galactose MeSH
- Glucose MeSH
- Glycoproteins chemistry MeSH
- Sodium Hydroxide MeSH
- N-Acetylneuraminic Acid * MeSH
- Mannose MeSH
- Monosaccharides * analysis MeSH
- Tandem Mass Spectrometry MeSH
- Xylose MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Capillary electrophoresis represents a promising technique in the field of pharmaceutical analysis. The presented review provides a summary of capillary electrophoretic methods suitable for routine quality control analyses of small molecule drugs published since 2015. In total, more than 80 discussed methods are sorted into three main sections according to the applied electroseparation modes (capillary zone electrophoresis, electrokinetic chromatography, and micellar, microemulsion, and liposome-electrokinetic chromatography) and further subsections according to the applied detection techniques (UV, capacitively coupled contactless conductivity detection, and mass spectrometry). Key parameters of the procedures are summarized in four concise tables. The presented applications cover analyses of active pharmaceutical ingredients and their related substances such as degradation products or enantiomeric impurities. The contribution of reported results to the current knowledge of separation science and general aspects of the practical applications of capillary electrophoretic methods are also discussed.
A fast method for the determination of tropane alkaloids, using a portable CE instrument with a capacitively coupled contactless conductivity detector (CE-C4D) was developed and validated for determination of atropine and scopolamine in seeds from Solanaceae family plants. Separation was obtained within 5 min, using an optimized background electrolyte consisting of 0.5 M acetic acid with 0.25% (w/v) β-CD. The limit of detection and quantification was 0.5 µg/mL and 1.5 µg/mL, respectively, for both atropine and scopolamine. The developed method was validated with the following parameters-precision (CV): 1.07-2.08%, accuracy of the assay (recovery, RE): 101.0-102.7% and matrix effect (ME): 92.99-94.23%. Moreover, the optimized CE-C4D method was applied to the analysis of plant extracts and pharmaceuticals, proving its applicability and accuracy.
Bicarbonate and phosphate constitute major salivary buffering components, and their importance consists in the neutralization of acidic gastric contents during reflux episodes. In this work, capillary electrophoresis with capacitively coupled contactless conductivity detector was applied for the analysis of bicarbonate, phosphate, and another inorganic (chloride, nitrite, nitrate, sulfate, thiocyanate) and organic anions (acetate, butyrate) to evaluate their levels in saliva. The background electrolytes of different composition and pH between 6.02-9.41 were assessed for the bicarbonate and phosphate determination by comparison of the real analyses of a model solution with the simulation by PeakMaster software. The optimized background electrolyte was composed of 10 mM 2-(N-morpholino)ethanesulfonic acid, 20 mM arginine, and 30 µM cetyltrimethylammonium bromide, pH 8.95. Using this BGE, the anion levels were compared in saliva from 20 patients suffering from gastroesophageal reflux disease (GERD) and saliva from 12 healthy subjects. Bicarbonate levels were significantly elevated in saliva from GERD patients suggesting the possible applicability of bicarbonate as a biomarker in non-invasive diagnostics of GERD by CE-C4 D.
- MeSH
- Anions analysis MeSH
- Electric Conductivity MeSH
- Electrophoresis, Capillary methods MeSH
- Phosphates analysis MeSH
- Gastroesophageal Reflux diagnosis MeSH
- Bicarbonates analysis MeSH
- Humans MeSH
- Saliva chemistry MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
The developments of analytical contactless conductivity measurements based on capacitive coupling over the two years from mid-2018 to mid-2020 are covered. This mostly concerns applications of the technique in zone electrophoresis employing conventional capillaries and to a lesser extent lab-on-chip devices. However, its use for the detection in several other flow-based analytical methods has also been reported. Detection of bubbles and measurements of flow rates in two-phase flows are also recurring themes. A few new applications in stagnant aqueous samples, e.g. endpoint detection in titrations and measurement on paper-based devices, have been reported. Some variations of the design of the measuring cells and their read-out electronics have also been described.
- MeSH
- Food Analysis MeSH
- Electric Conductivity * MeSH
- Electrophoresis, Capillary methods MeSH
- Industry MeSH
- Water MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Review MeSH
The publications concerning capacitively coupled contactless conductivity detection for the 2-year period from mid-2016 to mid-2018 are covered in this update to the earlier reviews of the series. Relatively few reports on fundamental investigations or new designs have appeared in the literature in this time interval, but the development of new applications with the detection method has continued strongly. Most often, contactless conductivity measurements have been employed for the detection of inorganic or small organic ions in conventional capillary electrophoresis, less often in microchip electrophoresis. A number of other uses, such as detection in chromatography or the gauging of bubbles in streams have also been reported.
Simultaneous electromembrane extraction (EME) of six trace metal cations (Cu2+ , Zn2+ , Co2+ , Ni2+ , Pb2+ , Cd2+ ) from saline samples was investigated. CE with capacitively coupled contactless conductivity detection (C4 D) was used to determine the metals in acceptor solutions due to its excellent compatibility with the minute volumes of acceptor solutions. Bis(2-ethylhexyl)phosphate (DEHPA) was selected as a suitable nonselective modifier for EME transport of target metal cations. Both, the individual effect of each major inorganic cation (Na+ , K+ , Ca2+ , Mg2+ ) and their synergistic effect on EME of the trace metal cations were evaluated. In both cases, a decrease in extraction efficiency was observed when major inorganic cations were present in the sample. This effect was more significant for Ca2+ and Mg2+ . The system was optimized for simultaneous extractions of the six target metals from saline samples (50 mM Na+ , 5 mM Mg2+ , 1 mM K+ , and 1 mM Ca2+ ) and following EME conditions were applied. Organic phase consisted of 1-nonanol containing 1% (v/v) DEHPA, acceptor solution was 1 M acetic acid (HAc) and sample pH was adjusted to 5. Sample was stirred at 750 rpm and EMEs were carried out at extraction potential of 10 V for 20 min. The method presented a repeatability between 8 and 21.8% (n = 5), good linearity in 0.5-10 μM concentration range (R2 = 0.987-0.999) and LOD better than 2.6 nM. Applicability of the EME-CE-C4 D method to the analyses of metal cations in drinking water, seawater, and urine samples was also demonstrated.
The development of capacitively coupled contactless conductivity detection for the two-year period from mid-2014 to mid-2016 is covered in this review. This includes a survey of fundamental studies and further developments of the measuring technique reported as well as a discussion of new applications. These mostly concern capillary electrophoresis carried out in conventional capillaries as well as on microchip electrophoresis devices. The main focus is on the determination of small non-UV-absorbing organic ions and inorganic ions in different types of samples of clinical, nutritional or environmental interest. Outside of electrophoresis contactless conductivity detection is finding uses in detection in column chromatography, flow-injection analysis and industrial applications.
- MeSH
- Inorganic Chemicals analysis MeSH
- Chromatography methods MeSH
- Equipment Design MeSH
- Electric Conductivity MeSH
- Electrodes MeSH
- Electrophoresis, Capillary instrumentation methods MeSH
- Electrophoresis, Microchip instrumentation methods MeSH
- Ions analysis MeSH
- Humans MeSH
- Organic Chemicals analysis MeSH
- Computer Simulation MeSH
- Flow Injection Analysis methods MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Review MeSH
An axial design of a capacitively coupled contactless conductivity detector was tested in combination with fused-silica capillaries with internal diameters of 10, 15, and 25 μm, which are used for high-efficiency electrophoretic separation. The transmission of the signal in the detection probe dependent on the specific conductivity of the solution in the capillary in the range 0-278 mS.m-1 has a complex character and a minimum appears on the curve at very low conductivities. The position of the minimum of the calibration dependence gradually shifts with decreasing frequency of the exciting signal from 1.0 to 0.25 MHz toward lower specific conductivity values. The presence of a minimum on the calibration curves is a natural property of the axial design of contactless conductivity detector, demonstrated by solution of the equivalent electrical circuit of the detection probe, and is specifically caused by the use of shielding foil. The behavior of contactless conductivity detector in the vicinity of the minimum was documented for practical separations of amino acids in solutions of 3.2 M acetic acid with addition of 0-50% v/v methanol.
- MeSH
- Amino Acids analysis MeSH
- Electric Conductivity MeSH
- Electrophoresis, Capillary * MeSH
- Calibration MeSH
- Publication type
- Journal Article MeSH
Capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C(4)D) was employed for fast determination of meldonium (MEL) in urine samples. Background electrolyte consisting of 2M acetic acid (pH 2.3) was used for separation of MEL from cationic compounds present in urine samples and the overall analysis time was less than 4min per sample. Direct injection of urine samples was possible after 1:9 dilution with deionized water. This simple sample pretreatment was sufficient to eliminate possible matrix effects on CE performance and allowed for precise and sensitive determination of free MEL in urine. Excellent linearity (r(2)≥0.9998) was obtained for two concentration ranges, 0.02-4μgmL(-1) and 2-200μgmL(-1), by simply changing injection time from 10 to 2s without the need for additional dilution of urine samples. Limit of detection was 0.015μgmL(-1) and average recoveries from urine samples spiked at 0.02-123.5μgmL(-1) MEL ranged from 97.6-99.9%. Repeatability of migration times and peak areas was better than 0.35% and 4.2% for intraday and 0.95% and 4.7% for interday measurements, respectively. The above reported data proved good applicability of the CE-C(4)D method to determination of various MEL concentrations in urine samples and good long-term performance of the analytical system. The method might be particularly useful in analyses of large batches of samples for initial testing of MEL-positive vs. MEL-negative urine samples.
- MeSH
- Doping in Sports MeSH
- Electric Conductivity MeSH
- Electrophoresis, Capillary methods MeSH
- Electrolytes MeSH
- Humans MeSH
- Methylhydrazines urine MeSH
- Substance Abuse Detection methods MeSH
- Water MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
