Best skin disinfectant for central line insertion is:
"Chlorhexidine is now the disinfectant recommended for all catheter placement procedures and for routine site cleansing during dressing changes."- Comprehensive Hospital Medicine: An Evidence-Based And Systems Approach By Mark V. Williams, Scott A. Flanders, p320
"Use of antiseptic solution for skin disinfection at the catheter insertion site helps prevent catheter-related infection. 
Chlorhexidine-based solutions appear to be superior to both aqueous and alcohol-based povidone-iodine in reducing the risk for catheter colonization and catheter-related bloodstream infection. If there is a contraindication to chlorhexidine, tincture of iodine, an iodophor or 70 per cent alcohol can be used as alternatives"-uptodate.com
Povione iodine
Alcohol
Cetrimide
Chlorhexidine