Simple Protein Analysis by Droplet Paper Spray Ionization Mass Spectrometry with Polyolefin Silica-Based Paper.

Paper spray ionization mass spectrometry (PSI MS) has emerged as a notable method for the rapid analysis of biological samples. However, the typical cellulose-based paper tip is incompatible with protein detection due to the strong interaction between cellulose hydroxyl groups and proteins. In this study, we utilized a commercially available polyolefin-based synthetic paper, Teslin®, as an alternative PSI substrate for simple protein analysis. We have named this method "droplet PSI" MS, as the aqueous protein solution droplet retains its shape on the Teslin® paper tip. For droplet PSI, no further chemical pretreatment was necessary for the Teslin® substrate; the only required preparation was shaping the Teslin® paper into a triangular tip. In droplet PSI MS, protein ion signals were instantly detected from a protein solution droplet upon applying a spray solvent in situ along with high voltage (HV). When compared with conventional PSI MS, our method demonstrated superior sensitivity. The droplet PSI MS utilizing Teslin® also showcased flexibility in real-time observation of protein alterations induced by an acid additive. Additionally, the effects of spray solvent composition and the application method were discussed.

Photodegradation of tetracycline and sulfathiazole individually and in mixtures.

Antibiotics in environment can be of concern as they can enter the food chain posing risks to ecosystems and human health. Photodegradation has been considered as a promising way of naturally degrading antibiotics in environment. Antibiotics are usually present in mixtures in environment; however, previous studies focused on individual compounds. Therefore, this study investigated the effect of UV irradiation on the degradation of tetracycline (TC) and sulfathiazole (STH) in individual solutions and mixtures. Under dark conditions, the initial masses of TC and STH were reduced by about 35% and 26%, respectively, over a 35 d-reaction period. With UV irradiation TC and STH were completely removed within 14 d and 35 d, respectively, regardless of the initial concentrations. Both the TC and STH removals were faster (i.e., 2-4 times) when they were in mixtures. This may be partly attributed to the byproducts such as sulfate that can promote indirect photolysis and partly to the enhanced hydrolysis due to changes in the solution pH. Overall, this study suggests that when photodegradation is used to remove antibiotics in water, the removal kinetics of antibiotics individually and in mixtures can be considered to develop more efficient treatment technologies.