hope experts will provide exact-gyan, in the meanwhile...
here's FDA references...
“Powder-Free”
Gloves with trace amounts of residual former-release powder (2 mg or less per glove) and no intentionally added donning powders are commonly referred to as “powder free.”
http://www.fda.gov/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocuments/ucm073111.htm
http://www.fda.gov/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocuments/ucm072528.htm
couple of documents give away the reference standards of ASTM which need are relevant/appropriate for respective category as well.
powder free gloves are stated to meet requirement of ASTM < 2 mg/glove
http://www.accessdata.fda.gov/cdrh_docs/pdf11/K110016.pdf
http://www.accessdata.fda.gov/cdrh_docs/pdf11/K111878.pdf)
ISO seems to cover these requirement in equal detail...
ISO 21171 Medical gloves - determination of removable surface powder.
which actually sets limits for different 'materials' of gloves. (viz., latex, synthetic, vinyl, nitrile, etc.,) and also ''surgical vs general gloves'
and limits seem to be relatively stringent as well.
hope that helps...