Spectrophotometic Determination of Caffeine and Vitamin B6 in Selected Beverages, Energy/Soft Drinks and Herbal Products

In this study, a simple, sensitive and reproducible spectrophotometric technique has been developed and validated for the determination of caffeine and vitamin B6 in beverages, energy/soft drinks and herbal products. The determination of caffeine and vitamin B6 in the respective samples were carried out at maximum (λmax) absorbance of 272 and 290 nm respectively. The method was validated in terms of linearity, sensitivity (limit of Detection (LOD) and limit of Quantification (LOQ), accuracy (% Recovery), precision (relative standard deviation). The method was linear from (4-20 µg/ml and 50 - 250 µg/ml with r 2 of 0.9991 and 0.9996 for vitamin B6 and caffeine respectively. The accuracy of the method ranged from 99.48 - 101.42% for caffeine and 99.94% - 102.35% for vitamin B6. The detection limit and quantification limit were 0.192 µg/ml and 0.640 µg/ml for vitamin B6 while 0.0155 µg/ml and 0.0518 µg/ml was obtained for caffeine. The method for the two analytes was found to be precise as the percentage relative standard deviation was below 5%. Therefore, the method proposed in this study is rapid, suitable and can be used as a quality control index for caffeine and vitamin B6 in beverages, energy/soft drinks and herbal products in industries. Keywords: Caffeine, Vitamin B6, Beverages, Energy/Soft drinks, Herbal products, Spectrophotometr

Bioactive microfluidic paper device for pesticide determination in waters

This work presents a new optical microfluidic paper biosensor for the detection of organophosphate pesticides and carbamate pesticides. The assay strip is composed of a paper support (1 × 17.6 mm) onto which acet- ylcholine esterase (AChE) and acetylcholine chloride (AChCl) are deposited, in such a way that there is a small hole between them that ensures that they only come into contact in the reaction zone when they are carried by a solution of the sample by lateral flow to the reaction zone containing bromocresol purple (BCP) as the pH indicator, immobilized by sol-gel. The sensor operates at room temperature and the rate of the inhibited reaction serves as an analytical signal, which is measured using a camera by quantifying the appropriate colour co- ordinate. Calibration curves were obtained for chlorpyrifos and carbaryl, with a useful concentration range from 0.24 to 20 μg L−1 for carbaryl and from 2.00 to 45 μg L−1 for chlorpyrifos. The detection limits were 0.24 and 2.00 μg L−1, respectively, and with reproducibility around 4.2–5.5%. The method was applied to the de- termination of pesticides in different water samples, with no sample preparation.This study was supported by a project from the Spanish MINECO (CTQ2016-78754-C2-1-R), a project partially supported by European Regional Development Funds (ERDF)