How should I handle and store absolute quantitation standards for real-time experiments?
FAQ ID -9099

Store the standards at a high concentration in aliquots at -20oC to -70oC. If using low concentrations, stabilize standards with carrier nucleic acid. It is always best to use freshly diluted standards for each experiment. If possible, use siliconized tubes for standard (and target) dilutions. This will prevent any unspecific binding of nucleic acids to the plastic.