•Developments and applications of C4D in analytical techniques are reviewed.•The period of the last two years from mid-2018 to mid-2020 is covered.•Instrumental innovations and practical examples of ...C4D are discussed.•Applications in CE, MCE, IC, LC, flow through and paper-based analytical techniques are presented.•Analyses of food, clinical, environmental, industrial and academic samples are summarized.
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.
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.
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•A review of the current status of the use of LEDs in analytical devices is given.•Fundamental aspects with relevance to quantitative measurements are discussed.•A broad overview of ...the reported applications is given.
A general overview of the development of the uses of light-emitting diodes in analytical instrumentation is given. Fundamental aspects of light-emitting diodes, as far as relevant for this usage, are covered in the first part. The measurement of light intensity is also discussed, as this is an essential part of any device based on light-emitting diodes as well. In the second part, applications are discussed, which cover liquid and gas-phase absorbance measurements, flow-through detectors for chromatography and capillary electrophoresis, sensors, as well as some less often reported methods such as photoacoustic spectroscopy.
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.
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.
A study on the use of flexible printed circuit board material for the construction of drift tubes for ion mobility spectrometry is reported. This is significantly less complicated than the ...conventional approach based on stacked electrode and insulator rings, as the material can simply be rolled up to obtain a string of circular electrodes. The size and spacing of the electrodes was found to have a strong effect on the resolving power. For an optimized geometry with electrodes of 1.5 mm width at a pitch of 3.5 mm resolving powers of up to 80 were achieved for quaternary amines introduced by electrospray ionization into a drift tube of 10 cm length and an applied voltage of 4200 V. This performance was found to be comparable to that of a conventional drift tube based on stacked rings with otherwise identical geometry and operating conditions. The entire instrument was constructed in-house. Its utility was demonstrated with the determination of the C12, C14 and C16 benzalkonium ions in several commercial cleaning products with limits of detection of 20, 25, and 38 μg L−1, respectively.
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•The use of a flexible printed circuit board allows the facile construction of drift tubes for ion-mobility spectrometry.•A comparison with the traditional stacked ring design demonstrated a matching performance in terms of resolving power.•The quantitative determination of benzalkonium in disinfectants was possible with the in-house constructed instrument.
The composition of gas mixtures may be determined via changes of the speed of sound. As this affects the resonance frequency of the gas inside a tube, indirect measurements through a frequency ...analysis are also possible. It is demonstrated that this may be carried out with unprecedented simplicity by the novel employment of a piezoelectric tube which serves at the same time as a resonance tube and as transducer into the electronic domain. Experiments were run using a simple diecast aluminum box as the measuring cell, inside which the piezoelectric tube made from lead zirconium titanate with 30-mm length and 5.35-mm inner diameter was suspended. A small loudspeaker placed into the cell served for excitation of the resonance. Peak frequencies between 3910 and 14,590 Hz (for pure CO
and He, respectively) were obtained. Two component mixtures of O
/N
, CO
/N
, and He/N
at various composition were tested. A linear frequency change from 4790 to 5100 Hz was observed when going from pure O
to pure N
.
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 analysis of tobramycin was demonstrated successfully as an example for electrospray ionization on an open-source hardware ion mobility spectrometer. This instrument was assembled inexpensively ...in-house, and required only very few purpose-made components. The quantitative determination of tobramycin required 20 s for a reading. The calibration curve for the range from 50 to 200 μM was found to be linear with a correlation coefficient of
r
= 0.9994. A good reproducibility was obtained (3% relative standard deviation) and the limit of detection was determined as 8 μM. As the concentration of the active ingredient in the eye drops (ophthalmic solutions) is too high for the sensitivity of the instrument, the samples had to be diluted appropriately.
Graphical abstract
Early deafness leads to enhanced attention in the visual periphery. Yet, whether this enhancement confers advantages in everyday life remains unknown, as deaf individuals have been shown to be more ...distracted by irrelevant information in the periphery than their hearing peers. Here, we show that, in a complex attentional task, a performance advantage results for deaf individuals.
We employed the Useful Field of View (UFOV) which requires central target identification concurrent with peripheral target localization in the presence of distractors - a divided, selective attention task. First, the comparison of deaf and hearing adults with or without sign language skills establishes that deafness and not sign language use drives UFOV enhancement. Second, UFOV performance was enhanced in deaf children, but only after 11 years of age.
This work demonstrates that, following early auditory deprivation, visual attention resources toward the periphery slowly get augmented to eventually result in a clear behavioral advantage by pre-adolescence on a selective visual attention task.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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