Conductivity detection Dotaz Zobrazit nápovědu
A simple rule stating that the signal in conductivity detection in capillary zone electrophoresis is proportional to the difference between the analyte mobility and mobility of the background electrolyte (BGE) co-ion is valid only for systems with fully ionized electrolytes. In zone electrophoresis systems with weak electrolytes both conductivity signal and electromigration dispersion of analyte peaks depend on the conductivity and pH effects. This allows optimization of the composition of BGEs to give a good conductivity signal of analytes while still keeping electromigration dispersion near zero, regardless of the injected amount of sample. The demands to achieve minimum electromigration dispersion and high sensitivity in conductivity detection can be accomplished at the same time. PeakMaster software is used for inspection of BGEs commonly used for separation of sugars (carbohydrates, saccharides) at highly alkaline pH. It is shown that the terms direct and indirect conductivity detection are misleading and should not be used.
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 ve sportu MeSH
- elektrická vodivost MeSH
- elektroforéza kapilární metody MeSH
- elektrolyty MeSH
- lidé MeSH
- methylhydraziny moč MeSH
- odhalování abúzu drog metody MeSH
- voda MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Conductivity detection is a universal detection technique often encountered in electrophoretic separation systems, especially in modern chip-electrophoresis based devices. On the other hand, it is sparsely combined with another contemporary trend of enhancing limits of detection by means of various preconcentration strategies. This can be attributed to the fact that a preconcentration experimental setup usually brings about disturbances in a conductivity baseline. Sweeping with a neutral sweeping agent seems a good candidate for overcoming this problem. A neutral sweeping agent does not hinder the conductivity detection while a charged analyte may preconcentrate on its boundary due to a decrease in its effective mobility. This study investigates such sweeping systems theoretically, by means of computer simulations, and experimentally. A formula is provided for the reliable estimation of the preconcentration factor. Additionally, it is demonstrated that the conductivity signal can significantly benefit from slowing down the analyte and thus the overall signal enhancement can easily overweight amplification caused solely by the sweeping process. The overall enhancement factor can be deduced a priori from the linearized theory of electrophoresis implemented in the PeakMaster freeware. Sweeping by neutral cyclodextrin is demonstrated on an amplification of a conductivity signal of flurbiprofen in a real drug sample. Finally, a possible formation of unexpected system peaks in systems with a neutral sweeping agent is revealed by the computer simulation and confirmed experimentally.
The methodology for separations of saccharides in standard electrophoretic systems has been transferred to the short-capillary electrophoresis format. The laboratory-designed apparatus used employs a quartz capillary with an internal diameter of 10 μm, a total length of 10 cm, and an effective length of 4 cm, in combination with contactless conductivity detection. It has been applied to separations of neutral mono- and disaccharides. The saccharides are separated in the anionic form, in solutions of alkali hydroxides, namely, KOH, NaOH, and LiOH. The separation of a model mixture of five saccharides (sucrose, lactose, glucose, fructose, and ribose) takes less than 1 min, the LOD equaling 15, 35, 19, 17, and 24 mg L(-1) and the LOQ equaling 52, 117, 63, 53, and 79 mg L(-1) for sucrose, lactose, glucose, fructose, and ribose, respectively. The technique developed has been used to determine sucrose, glucose and fructose in high-energy drinks. The separation is finished within less than 50 s; the saccharide contents determined are identical with the declared values within the reliability interval in most cases, the RSD value being mostly less than 2%. In general, the separation system developed is very convenient for rapid analyses of large sets of similar samples, e.g., in product quality control or environmental monitoring.
- MeSH
- časové faktory MeSH
- design vybavení MeSH
- elektrická vodivost MeSH
- elektroforéza kapilární ekonomika přístrojové vybavení MeSH
- energetické nápoje analýza MeSH
- limita detekce MeSH
- monosacharidy analýza izolace a purifikace MeSH
- sacharosa analýza izolace a purifikace MeSH
- Publikační typ
- časopisecké články MeSH
- hodnotící studie MeSH
- práce podpořená grantem MeSH
An overview of the developments of capacitively coupled contactless conductivity detection in CE and related techniques over approximately the last 2 years is given. The method has seen strong growth, and diverse new applications are being reported. Besides more advanced techniques on conventional capillaries, these include further developments of detection on lab-on-chip devices as well as in miniaturized chromatographic systems and some methods not involving separations. An increasing number of reports are based on the now readily available commercial detectors, but, while few publications on fundamental studies have appeared recently, interesting new approaches on creating low cost devices have also appeared.
The developments in the field of capacitively coupled contactless conductivity detection in the approximate period from July 2010 to June 2012 are traced. Few reports concerning fundamental studies or new detector designs have appeared. On the other hand, applications in standard CZE are flourishing and contactless conductivity measurements are increasingly being employed as part of novel or more sophisticated experimental systems. Work on the lab-on-chip devices integrating contactless conductivity detection is continuing. A range of reports on the use of the simple yet powerful detection technique of contactless conductivity measurements in chromatographic separation as well as for analytical methods not including a separation step have also appeared.
- MeSH
- analýza potravin metody MeSH
- elektrická vodivost MeSH
- elektroforéza kapilární přístrojové vybavení metody trendy MeSH
- elektroforéza mikročipová metody MeSH
- klinická chemie přístrojové vybavení metody MeSH
- kontaminace léku prevence a kontrola MeSH
- léčivé přípravky analýza MeSH
- mikrofluidní analytické techniky přístrojové vybavení metody MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
The review covers the progress of capacitively coupled contactless conductivity detection over the 2 years leading up to mid-2014. During this period many new applications for conventional CE as well as for microchip separation devices have been reported; prominent areas have been clinical, pharmaceutical, forensic, and food analyses. Further progress has been made in the development of field portable instrumentation based on CE with contactless conductivity detection. Several reports concern the combination with sample pretreatment techniques, in particular electrodriven extractions. Accounts of arrays of contactless conductivity detectors have appeared, which have been created for quite different tasks requiring spatially resolved information. The trend of the use of contactless conductivity measurements for applications other than CE has continued.
- MeSH
- analýza potravin přístrojové vybavení metody MeSH
- design vybavení MeSH
- elektrická vodivost MeSH
- elektroforéza kapilární přístrojové vybavení metody MeSH
- elektroforéza mikročipová přístrojové vybavení metody MeSH
- lidé MeSH
- monitorování životního prostředí přístrojové vybavení metody MeSH
- průtoková injekční analýza přístrojové vybavení metody MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy 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
- analýza potravin MeSH
- elektrická vodivost * MeSH
- elektroforéza kapilární metody MeSH
- průmysl MeSH
- voda MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy 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.
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
- anorganické látky analýza MeSH
- chromatografie metody MeSH
- design vybavení MeSH
- elektrická vodivost MeSH
- elektrody MeSH
- elektroforéza kapilární přístrojové vybavení metody MeSH
- elektroforéza mikročipová přístrojové vybavení metody MeSH
- ionty analýza MeSH
- lidé MeSH
- organické látky analýza MeSH
- počítačová simulace MeSH
- průtoková injekční analýza metody MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
