Ultra-trace detection of caffeine and theophylline with high sensitivity and selectivity using Gd2(MoO4)3 nanosheets

Abstract

In this study, gadolinium molybdate, Gd2(MoO4)3 (Gam) nanosheets have been substantially synthesized using a hydrothermal method with varying reaction temperatures. PXRD, XPS, and HR-TEM confirmed the crystal phase and morphology of Gam nanosheets. According to CV, LSV, and EIS techniques, Gam (synthesized at 150 ℃) modified GCE possesses excellent electrochemical properties and further has been used for caffeine and theophylline detection. The limit of detection of caffeine was found to be 4.1 nM with a linear range of 0.01 – 0.1 μM and 0.2 – 1.6 μM. Limit of detection of theophylline was calculated to be 11.9 nM with a linear range of 0.03 – 1.5 μM and 2.0 – 4.5 μM. Gam modified GCE was applied for caffeine and theophylline detection in green tea leaves (GS-1) and coca (CS-2) samples and interestingly found capable for caffeine detection without spiking. After spiking, recoveries of caffeine and theophylline in GS-1 were achieved 100.6 – 101.7% and 102.57–105.21% respectively. In CS-2 the recoveries for caffeine and theophylline were found to be 98.3 – 101.8% and 97 – 99.33% respectively. The excellent long-term stability, recyclability, and real sample analysis validated the sensor for biological as well as pharmaceutical samples diagnosis.