Photodegradation of norfloxacin in ice: Role of the fluorine substituent

Ice is an important medium in cold regions, because it regulates the environmental behaviors and the fate of pollutants. The photodegradation of fluoroquinolone (FQ) antibiotics as emerging contaminants of concern in ice remains poorly understood. Here, the photodegradation of fluorine-containing norfloxacin (NOR) as one model of FQs in ice formed from freezing solutions was investigated. Pipemidic acid (PPA) as a structural analogue of NOR was selected to compare the effect of molecular structure on the antibiotic photodegradation in the ice. Results suggested that the photodegradation rate constant of NOR in ice relative to pure water increased by 40.0%. Both the absorbance in the absorption spectra and quantum yields of NOR in ice over water increased by 1.4 times. Direct photodegradation mainly caused the defluorination of NOR, which was more important than cleavage and oxidation of the piperazine ring by self-sensitized photooxidation in ice. The defluorination rate of NOR in the ice relative to water increased by about 12.7%. The fluorine substituent played a more important role in the NOR photodegradation in the ice, resulting in a 1.6-fold increase in the photodegradation rate constant of NOR relative to PPA. This work provides a new insight into the role of fluorine substituents in the photodegradation of fluorinated pharmaceuticals in cold regions.

Quality changes in squid (Loligo duvaucelli) tubes chilled with dry ice and water ice

Squid tubes were packed with 100% (w/w of squid) dry ice (PI), 20% dry ice and 50% water ice (PII) and 50% water ice (PIII) in polyethylene bags and store in thermocole boxes at room temperature (32 ± 2°C) for 24 h. Quality changes curing storage were studied. Lowest temperature of -30.3°C was attained in PI while it was 15-16°C in PII and PIII at 1 h of storage. The gas compositions in packages initially were 21% O2, 0.4% CO2 and 78.1% N2 in PI, PII and PIII, respectively. During storage for 24 h highest level of 82.5% CO2 was noticed in PII. Fresh squid tubes had bacterial flora of Hafnia, Pseudomonas, Bacillus, Flavobacterium and Alcaligens. Hafnia constituted 74% of the flora. Alcaligenes (47%), Alteromonas (30%) and Alcaligenes (56%) were dominant in squid tubes stored in 100% dry ice, in the combination package, and in 100% water ice, respectively. Increase in total volatile base nitrogen and trimethylamine nitrogen, no definite trend in free fatty acid values in all packages while increase in pH in PI and PIII and no consistent changes in PI were noticed during storage for 24 h. The PI had lowest bacterial counts and PIII the highest. Squids stored in PI and PII were sensorily acceptable after 24 and 18 h, respectively.