Quick stabilization of capillary for rapid determination of potassium ions in the blood of epilepsy patients by capillary electrophoresis without sample pretreatment

Mutations in the potassium channel genes may be linked to the development of epilepsy and affect the blood potassium levels. Therefore, accurate determination of potassium in the blood will be critical to diagnose the cause of epilepsy. CE is a competent technique for the fast detection of multiple ions, but complicated matrices of a blood sample may cause significant variation of migration times and the peak shape. In this work, a procedure for rapid stabilization of the capillary inner surface through preflushing of a blood sample was employed. The process takes only 40 min for a capillary and then it can be used for more than 2 weeks. No pretreatment of the blood sample or other surface modification of the capillary is needed for the analysis. The RSDs of the migration time and peak area were reduced to 1.5 and 5.1% from 12.6 and 14.5%, respectively. The proposed method has been successfully applied to the determination of the potassium contents in the blood sample of patients with epilepsy at different stages. The recoveries of potassium ions in these blood samples are in a range from 86.5 to 104.5%.

An ionophore-based persistent luminescent ‘Glow Sensor’ for sodium detection

Optical sensors have numerous positive attributes such as low invasiveness, miniaturizability, biocompatibility, and ease of signal transduction. Recently, there has been a strong research focus on using phosphorescent readout mechanisms, specifically from long-lifetime phosphorescent or ‘persistent luminescence’ particles, for in vitro and in vivo sensors. Persistent luminescence readouts can avoid cellular autofluorescence during biological monitoring, leading to an improved signal-to-noise ratio over a more traditional fluorescence readout. In this study, we show for the first time an ionophore-based optical bulk optode sensor that utilizes persistent luminescence microparticles for ion detection. To achieve this, we combined long-lifetime strontium aluminate-based ‘glow-in-the-dark’ microparticles with a non-fluorescent pH-responsive dye in a hydrophobic plasticized polymer membrane along with traditional ionophore-based optical sensor components to create a phosphorescent ‘Glow Sensor’. The non-fluorescent pH indicator dye gates the strontium aluminate luminescence signal so that it decreases in magnitude with increasing sodium concentration. We characterized the Glow Sensor in terms of emission lifetime, dynamic range, response time, reversibility, selectivity, and stability.

A sodium-selective bulk-optode sensor is created by coupling persistent luminescence microparticles with a pH-sensitive dye through an ionophore-based detection mechanism.

Impedance-based sensor for potassium ions

A conductometric sensor for potassium ions in solution is presented. Interdigitated, planar gold electrodes were coated with a potassium-selective polymer membrane composed of a poly(vinyl chloride) matrix with about 65 wt% of plasticiser and 2-5 wt% of a potassium-selective ionophore. The impedance of the membrane was measured, using the electrodes as a transducer, and related to the concentration of potassium in a sample solution in contact with the membrane. Sensitivity was optimised by varying the sensor components, and selectivity for potassium over sodium was also shown. The resulting devices are compact, miniature, robust sensors which, by means of impedance measurements, eliminate the need for a reference electrode. The sensor was tested for potassium concentration changes of 2 mM across the clinically relevant range of 2.7-18.7 mM.

Improvement of heat transfer by promoting dropwise condensation using electrospun polytetrafluoroethylene thin films

Homogeneous superhydrophobic PTFE thin films showed stable dropwise condensation and much higher heat transfer. They contribute to energy-efficient transfer.