We currently conducting a research study titled "Bioluminescent Bacteria Isolated from Squid Ink (Uroteuthis edulis) as a Biosensor for Detecting Dibutyl Phthalate." We are uncertain about the correct method for preparing a DBP stock solution using dimethyl sulfoxide (DMSO) as a solvent, and we want to ensure that the final concentration of DMSO does not negatively affect the bioluminescent bacteria. Below is the approach we have developed based on our research:   A stock solution of DBP (CAS No. 84-74-2; purity: ≥ 99%) will be prepared by dissolving DBP in DMSO to achieve a concentration of 1000 µg/mL (1 mg/mL). Some studies have used a final concentration of 1M. This stock solution will then be diluted with a sodium chloride solution (the medium for the bioluminescent bacteria) to obtain the desired DBP concentrations of 25, 50, 100, 400, and 500 µg/L. These concentrations were selected based on environmentally reported DBP levels ranging from 0 to 300 µg/L (Guo et al., 2016) and up to 500 µg/L (Fatoki & Ogunfowokan, 1993). We will also ensure that the final concentration of DMSO remains at 0.02% in all test solutions.   For each test, 50 µL of bacterial suspension will be mixed with 50 µL of the corresponding toxicant solution in a 96-well plate. DMSO will serve as the solvent and vehicle control, while zinc sulfate will be used as the positive control.  

Can you explain detailed preparation on making the final DMSO concentration (0.02%)

Should we follow the preparation guidelines from [this source](https://www.medchemexpress.com/Dibutyl_phthalate.html?srsltid=AfmBOooBHvDhMCM_JHk_IC8uHn1XMXTaI6vuoOCEBHDsedkLLeZ2WR_a), or would it be acceptable to follow other methods from previous studies?