Most electrochemical sensing requires affordable, portable and easy-to-use electrochemical devices for use in point-of-care testing and resource-limited settings. This work presents the design and evaluates the analytical performance of a near-field communication (NFC) potentiostat, a flat card-sized electrochemical device containing a microchip for electrical analysis and an NFC antenna for smartphone connection. The NFC interface is a wireless connection between the microchip and smartphone to simplify measuring units and make the potentiostat into a passive operated device, running without a battery. The proposed potentiostat can perform the common electrochemical techniques including cyclic voltammetry and chronoamperometry with a current range and voltage range of ±20 µA and ±0.8 V. The performance of the NFC potentiostat is compared to a commercial benchtop potentiostat using ferricyanide as a standard solution. The results show that the NFC potentiostat is comparable to a commercial benchtop potentiostat for both cyclic voltammetry and chronoamperometry measurements. The application of the proposed potentiostat is demonstrated by measuring ascorbic acid concentration. As described, the NFC potentiostat, which is compatible with a smartphone, is low-cost, small in size and user-friendly. Thus, the device can be developed for on-site measurement to apply in various fields.

Objective Dehydroepiandrosterone sulfate (DHEAs), a prohormone secreted by the adrenal gland, plays a role in the synthesis of sex hormones, namely, androgen and estrogen. It has been found that the amount of DHEAs is correlated with age, although most studies have focused on the correlation of serum DHEAs levels with age and sex. Thus, this noninvasive, cross-sectional study aimed to investigate the correlation of urine DHEAs levels with age and sex in healthy Thai volunteers aged 20–80 years. Methods DHEAs levels were measured in 178 healthy volunteers using electrochemiluminescence immunoassay and then normalized by creatinine. Multiple regression was performed to determine the correlation of urine DHEAs levels normalized by creatinine with age and sex. Results The normalized DHEAs levels are correlated with age group for both sexes. Moreover, an increasing trend in DHEAs levels was found in the age group 20–29 years, and the DHEAs level peaked at the age group 30–39 years before declining with advancing age. Based on the multiple regression analyses, the significance of the interaction term ( P ​< ​0.05) indicates that both age and sex significantly contribute to the prediction of ln (DHEAs/Creatinine). Our fitted model implies the following: as age increases by 1 year, DHEAs/Creatinine is expected to decrease by 3.63% in females and by 2.18% in males. Conclusion This study reports more data on clinical reference value of urine DHEAs levels in healthy volunteers. Our result demonstrates urine DHEAs levels are associated with age and sex and decline by 2–3% a year.