Yes – low heat treatment will not affect assay results.
This will depend on how the samples have been stored. If samples are stored at 4°C, they should not be kept any longer than 2 days. You may conserve samples at -20ºC for long-term storage (for up to about 5 years), but be sure that recipients are well sealed to avoid evaporation. Avoid repeated freezing/thawing cycles (preferably no more than three).
Yes. Milk samples containing preservatives, such as Bronopol and sodium azide, may be used.