An Open Tubular Ion Chromatograph

Abstract

We describe an open tubular ion chromatograph (OTIC) that uses anion exchange latex coated 5 μm radius silica and 9.8 μm radius poly(methyl methacrylate) tubes and automated time/pressure based hydrodynamic injection for pL-nL scale injections. It is routinely possible to generate 50,000 plates or more (up to 150,000 plates/m, columns between 0.3 and 0.8 m have been used), and as such, fast separations are possible, comparable to or in some cases better than the current practice of IC. With an optimized admittance detector, nonsuppressed detection permits LODs of submicromolar to double digit micromolar for a variety of analytes. However, large volume injections are possible and can significantly improve on this. A variety of eluents, the use of organic modifiers, and variations of eluent pH can be used to tailor a given separation. The approach is discussed in the context of extraterrestrial exploration, especially Mars, where the existence of large amounts of perchlorate in the soil needs to be confirmed. These columns can survive drying and freezing, and small footprint, low power consumption, and simplicity make OTIC a good candidate for such a mission.

Contactless conductivity detection for analytical techniques— Developments from 2014 to 2016

“…Dasgupta and coworkers carried out a detailed study of the characteristics of C 4 D for conditions not previously investigated, i.e. with a special focus on very narrow capillary diameters (down to ∼ 1 μm) and electrolyte concentrations much lower than usually encountered in CZE , as they were mainly interested in detection in open tubular ion chromatography (OT IC) . Both factors lead to very high resistance values for the cell.…”

“…C 4 D is predominantly used in CE and MCE (see the former sections), but conductivity measurements are also useful for various other flow‐through analytical techniques, including LC, capillary LC, flow/sequential injection analysis and in microfluidic platforms. In the reviewed period, several publications on C 4 D in IC , open‐tubular IC , capillary IC and standard LC were reported. A reversed phase isocratic LC method was optimized for determination of aminoglycosidic antibiotics, which lack UV‐absorbing chromophores and are thus not suitable for LC analyses with conventional UV‐Vis absorbance detection .…”

“…C 4 D ensures high detection sensitivity even with low ID capillaries and CE‐C 4 D is regularly carried out in 10 μm ID separation capillaries. The admittance detector for low diameter capillaries developed by Dasgupta and coworkers discussed above allowed for sensitive detection in columns down to diameters of 1 μm and holds a great promise for further miniaturization in analytical chemistry . The admittance detector was used for detection in OT‐IC as well as in flow injection analysis .…”

Design and applications of miniaturized, portable LED based colorimeter

“…The analysis that can be performed in situ provides several advantages: (i) reduces analysis errors due to the fact that sample transportation is not needed, and chemical degradation is avoided, and (ii) reduces the duration of the total analytical process [5]. Several chemical analyftical techniques have been applied, or are being developed for field-portable or autonomous applications: (i) liquid chromatography [6,7], (ii) capillary electrophoresis [8][9][10][11], (iii) digital microfluidics [12] and (iv) electrochemical analysis [13]. Designing portable or autonomous instruments can be problematic due to the following reasons: (i) such instrumentation has the limited battery power supply, (ii) a low number of mechanical and moving parts must be used in the design, and (iii) such instrumentation is susceptible to changing environment and especially temperature fluctuations [10,14].…”

Coaxial flow‐gating interface for capillary electrophoresis

“…The usage of the flow‐gating principle is not limited to connecting flow‐through analytical methods with electrophoretic capillary— see above cited reviews. It has more general usage, e.g., in hydrodynamic injection of sample into chromatographic column or electrophoretic capillary , controls flushing of the sample system between separation runs , etc.…”