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.
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
A new portable CE instrument is presented. The instrument features the concurrent separation of anions and cations in parallel channels. Each channel has a separate buffer container to allow independent optimization of separation conditions. The microfluidics circuit is based on off-the-shelf parts, and can be easily replicated; only four valves are present in the design. The system employs a miniature automated syringe pump, which can apply both positive and negative pressures (-100 to 800 kPa). The application of negative pressure allows a semi-automatic mode of operation for introducing volume-limited samples. The separations are performed in a thermostatted compartment for improved reproducibility in field conditions. The instrument has a compact design, with all components, save for batteries and power supplies, arranged in a briefcase with dimensions of 52 × 34 × 18 cm and a weight of less than 15 kg. The system runs automatically and is controlled by a purpose-made graphical user interface on a connected computer. For demonstration, the system was successfully employed for the concurrent separation and analysis of inorganic cations and anions in sediment porewater samples from Lake Baldegg in Switzerland and of metal ions in a sample from the tailing pond of an abandoned mine in Argentina.
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
- Food Analysis instrumentation methods MeSH
- Equipment Design MeSH
- Electric Conductivity MeSH
- Electrophoresis, Capillary instrumentation methods MeSH
- Electrophoresis, Microchip instrumentation methods MeSH
- Humans MeSH
- Environmental Monitoring instrumentation methods MeSH
- Flow Injection Analysis instrumentation methods MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Review MeSH
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
- Food Analysis methods MeSH
- Electric Conductivity MeSH
- Electrophoresis, Capillary instrumentation methods trends MeSH
- Electrophoresis, Microchip methods MeSH
- Chemistry, Clinical instrumentation methods MeSH
- Drug Contamination prevention & control MeSH
- Pharmaceutical Preparations analysis MeSH
- Microfluidic Analytical Techniques instrumentation methods MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Review 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.
CE methods for the speciation of inorganic and organomercury compounds are reviewed. Sample preparation, separation conditions and detection modes are discussed. Efficient separation and sensitive determination of mercury species by CE typically involves complexation with various thiols, chromogenic and other chelating agents; however, some methods do not require complexation. Spectrophotometric detection based on UV-visible absorption is by far the most commonly used. Hyphenated techniques, such as CE/inductively coupled plasma (ICP)-MS, hydride generation coupled to ICP-MS or atomic fluorescence spectrometry and CE/atomic absorption spectrometry are gaining popularity due to their high sensitivity and selectivity. Last, but not least, the potential and applications of electrochemical methods for detection of separated mercury species are outlined.
