Ocean optics usb4000 spectrophotometer

The total chlorophyll content was extracted and measured according to a study by Porra et al. (1989 (link)). A leaf was taken and scanned with a flatbed scanner. The area was then estimated using the ImageJ software (https://imagej.nih.gov/ij/), Canon LIDE120 flatbed scanner (Canon, Tokyo, Japan). Afterwards, the leaves were ground using a pestle and mortar in 5 ml of 80% v/v acetone. The extracts were centrifuged (13,000 g) for 5 min and the supernatant was collected. The absorbance was then measured using an Ocean Optics USB4000 spectrophotometer (Ocean Optics, Dunedin, FL, USA).

The release of tetracycline from hydrogels containing tetracycline was determined using the following procedure: 1 g of a gel containing 1.5 mg of tetracycline was placed in a plastic tube with a dialysis membrane fixed to the end and the tetracycline-containing gel evenly distributed over the surface of the dialysis membrane. The tube was immersed in a vessel containing 30 mL saline (0.9% NaCl solution). The release was promoted by constant stirring at 30 °C. At specific time intervals, 1 mL of the solution was removed, combined with 0.3 mL 1 M NaOH, and used to determine the concentration of tetracycline spectrophotometrically with an Ocean Optics USB4000 spectrophotometer (Ocean Optics Inc., Largo, FL, USA) using a calibration curve (380 nm, 0–0.05 mg/mL; R² = 0.998). The sampled volume was replaced with 1 mL of saline.