Blood collection done with precautions for asceptic conditions will not get contaminated. It is better to use vacuuatainer, and if it is manual method i.e. collecting with syringe and needle and opening the collection vial, then we have to ensure that; there are no direct air currents like fan etc. nearby, use two burners, light them some 10 minutes before and open the vial between the two, use only Sodium Heparin as anti-coagulation factor, and most imp., mix it well and store at room temperature only, set the cultures not later than 36 to 38 hours, and it should yield proper metaphases. Also when you add the sample to culture media see if it is very old, in that case  L-Glutamine can be added to ensure active proliferation.

hello, when it comes to peripheral blood better use Sodium Citrate tubes 9NC or Heparin lithium and store at room temp (18-22 °C) in a vertical position for less than 24 hrs before culture. When it comes to bone marrow blood, you need at least 5 ml EDTA tubes, store at same conditions before culture. When the blood withdrawal is done correctly no fear of "contamination" 

Thank you for all of the answer. So, that methods does not change the quality of the chromosomes?. Thanks

Absolutely not. The quality is preserved, in all cases the "culture quality" is of a great importance for the next 48-72 hrs.

Sounds good thank you so much for both of you Sonal and Khaled :D

I have to try it