Dear Volodymyr Skalka

Simply add 10 micro liter of your sample and complete the volume to one liter, you will get 1:100000 dilution. 

Dear Volodymyr,

At first you can choose ELISA kit with wide range assay.

e,g for assessment Insulin concentration there are three types ELISA kits:

High Sensitive Insulin ELISA kit

Insulin ELISA kit

Wide range Insulin ELISA kit.

The third type for islet cells function and high Insulin concentration is ok.

Anyway for many proteins there are these three type ELISA kits.

If you prepared the ELISA kit and can not change it, there is no way except dilution.

But you need only three steps dilutions:

1) First 1:100  (e.g 10 micro liter +990 micro liter buffer)

 2) Second 1:100 (e.g 10 micro liter of the first dilution + 990 micro liter buffer)

3) final 1:10 dilution (e.g 100 micro liter of the second diluted protein + 900 micro liter buffer).

In this way, with three step dilutions 10-50 mg/ml converted to 100-500 ng/mL.

best

Mehdi

Dear Volodymyr Skalka

Simply add 10 micro liter of your sample and complete the volume to one liter, you will get 1:100000 dilution. 

Dear All. Thank you for your  answers, advice and useful link.