Smartphone-based miniaturized, green and rapid methods for the colorimetric determination of sugar in soft drinks

Total sugar content of soft drinks was determined in a 3D-printed chamber equipped with an USB camera attached to the smartphone to take pictures directly from the vessels used for the reaction of monosaccharides with cupric ion from Benedict's reagent. The freely available PhotoMetrix UVC application was used to control the device and process images. Reaction time, total volume of solution and illumination were evaluated. Images were captured before and after centrifugation and the results were compared with official method (AOAC 923.09, Lane-Eynon titration). Partial least squares calibration was used reaching suitable values (R2 above 0.99; Root mean square error of calibration (RMSEC) and Root mean square error in cross-validation (RMSECV) values lower than 0.07 and 0.23 mg mL−1, respectively). The proposed methods presented agreements from 95.3 to 108.7% to the official one. Hundreds of samples can be analyzed in one hour and reductions in energy expenditure by 5.5 times and waste volume by 78 times were obtained in relation to the AOAC method

Green microsaponification-based method for gas chromatography determination of sterol and squalene in cyanobacterial biomass

Sterol analysis of complex matrices can be very laborious. To minimize the existing drawbacks, a new micro-method of sterols and squalene determination in cyanobacteria was developed and applied to monitor their production of Phormidium autumnale cultured heterotrophically. Sample extraction/saponification and GC analysis of the target compounds were optimized separately using Plackett-Burman design (PB) followed by a central composite rotational design (CCRD). The most influential variables were identified to maximize compound recovery. Chloroform presented the highest capability to extract all target compounds with a horizontal shaker table (HST) for homogenization in the saponification step. For the pretreatment, a small amount of chloroform was used for 90 min at 50 °C and 6 min for the saponification time. The sample introduction in the GC injector was studied by evaluating pressure and injector temperature. High response for sterols and squalene were obtained between 19 and 23 psi and at 310 °C of injection temperature. The new method was able to determine different sterol concentrations: 0.2–0.6 mg kg−1 of squalene, 5–18 mg kg−1 of stigmasterol, 6 mg kg−1 of cholesterol, and 3 mg kg−1 of β-sitosterol, showing high analytical performance and fulfilling all steps, thus proving to be a promising technique.This work was supported by the Institutional Internationalization Program CAPES-PRINT nº 41/2017 and financed by CAPES – Brazilian Federal Agency for Support and Evaluation of Graduate Education within the Ministry of Education of Brazil. Additionally, we are grateful to the financial support by the National Council for Scientific and Technological Development (CNPq) – Brazil; PQ-2018, Process: 311125/2018-2 and Universal (MCTI/CNPq) 1/2016 Process: 428691/2016-1.Peer reviewe