If you are using HPLC follow this method (PDF attached), or if any other spectroscopic analysis then check out this review, Article Progress in quantitative analysis of plant hormones

To prepare a 1 mg/ml stock solution: Add 100 mg of the plant growth regulator to a 100 ml volumetric flask or other glass container. Add 2-5 ml of solvent to dissolve the powder. Once completely dissolved, bring to volume with double processed water. Stirring the solution while adding water may be required to keep the material in solution. Store the stock solution as recommended. Add 1.0 ml of the stock solution to 1 liter of medium to obtain a final concentration of 1.0 mg/L of the plant growth regulator in the culture medium.

For more details please follow the link:

https://www.sigmaaldrich.com/technical-documents/protocols/biology/growth-regulators.html

Dear Mr Muhammad Younas Mr Muhammad Nadeem and Mr Francisco X Nascimento

Thank you very much for your helps. Unfortunately, those are not the answer I seek. I am planning to use the solution on pear fruit by spraying method, directly on the fruit on the field. This is not for analysis but for exogenous application or treatment on plant organs.

I appreciate your help

Thank you very much

Best regard

Imad