C-H···π interactions disrupt electrostatic interactions between non-aqueous electrolytes to increase solubility

Grid-scale energy storage applications, such as redox flow batteries, rely on the solubility of redox-active organic molecules. Although redox-active pyridiniums exhibit exceptional persistence in multiple redox states at low potentials (desirable properties for energy storage applications), their solubility in non-aqueous media remains low, and few practical molecular design strategies exist to improve solubility. Here we convey the extent to which discrete, attractive interactions between C-H groups and π electrons of an aromatic ring (C-H···π interactions) can describe the solubility of N-substituted pyridinium salts in a non-aqueous solvent. We find a direct correlation between the number of C-H···π interactions for each pyridinium salt and its solubility in acetonitrile. The correlation presented in this work highlights a consequence of disrupting strong electrostatic interactions with weak dispersion interactions, showing how minimal structural change can dramatically impact pyridinium solubility.

Performance of blood glucose meters in compliance with current and future clinical ISO15197 accuracy criteria

Since 2003, blood glucose meters for patient self testing are approved in Europe based on the accuracy performance criteria as defined by the ISO15197 guideline. A new draft ISO guideline is currently under regulatory review, which suggests more strict accuracy acceptance criteria, and which may not be entirely fulfilled by currently commercialized blood glucose meter systems. In order to investigate the compliance of BG*Star and iBG*Star and several other blood glucose meters with the new draft ISO guideline, we performed a post-hoc analysis of data obtained from a recently performed ISO-conforming clinical accuracy performance study. This study was performed with 106 patients, clinically presenting with blood glucose levels distributed over the entire measurement range and in line with the glucose distribution requirements as demanded by the guideline. The YSI 2300 STAT Plus analyzer (glucose oxidase) served as reference method. While all tested meters had been in a high degree of compliance with the current ISO criteria, performance was lower when analyzed in accordance with the new acceptance criteria (95% of readings have to be within ±15 mg/dL for values <100 mg/dL, and within ±15% for values ≥100 mg/dL). The following meters met the new criteria: Accu-Chek Aviva (95.5%/98.6%), BG*Star (98.5%/97.3%), iBG*Star (98.5%/97.3%), FreeStyle Freedom Lite (95.5%/96.6%), and OneTouch Ultra2 (95.5%/96.5%). One meter failed with low blood glucose values (Contour: 90.9%/95.9%). In conclusion, BG*Star and iBG*Star and several other branded meters met the new draft ISO15197 acceptance criteria, when tested in accordance with the instructions for use and with the ISO accuracy testing protocol in a clinical setting.