Usually ppm or mg/lit is used for evaluation of ionic species in water / aqueous  samples.  this question is already discussed in Research gate.

Arsha,

  I would weigh out 0.0103 grams of the lindane, place it in a 1.0 liter volumetric flask then bring to volume with the solvent of your choice. You can also make the more concentrated 50 ppm stock by adding 0.05155 grams to a 1,0 liter flask, then perform a 5:1 dilution to obtain the 10 ppm concentration.

Good luck

Steve 

Dear Arsha,

In water ppm or mg/L is almost same. However, the solubility of lindane is only 7.3 mg/L at 25 C (practically insoluble in water). Please see the data sheet below

https://pubchem.ncbi.nlm.nih.gov/compound/lindane#section=Flash-Point

Therefore, you need to prepare a high concentration stock solution (say 500 ppm) of Lindane in organic solvents such as chloroform, ethyl ether, ethanol etc. Then perform the dilution to obtain 10 ppm in water.

Hope, this would help you.

Thank you.

Thank you very much Dr.Virendra Kumar Saxena, Dr.Steve A. Carrand Dr. Raj Kamal Singh for your valuable reply. The comments and suggestions are very helpful for my research work.

Arsha,  the organic solvent must be sufficiently soluble in water when you do the 'dilution' so that there is only one liquid phase, Paul.

Asha,

Please let me know how much volume of do you have of 50mg/ml.