Incubating the QIAamp Mini spin column loaded with Buffer AE or water for 5 minat room temperature before centrifugation generally increases DNA yield.A second elution step with a further 200 μl Buffer AE will increase yields by upto 15%.Volumes of more than 200 μl should not be eluted into a 1.5 ml microcentrifugetube because the spin column will come into contact with the eluate, leading topossible aerosol formation during centrifugation.Elution with volumes of less than 200 μl increases the final DNA concentration inthe eluate significantly, but slightly reduces the overall DNA yield (see Table 5,page 25). For samples containing less than 1 μg of DNA, elution in 50 μl BufferAE or water is recommended. Eluting with 2 x 100 μl instead of 1 x 200 μl doesnot increase elution efficiency.For long-term storage of DNA, eluting in Buffer AE and storing at –30 to –15°C isrecommended, since DNA stored in water is subject to acid hydrolysis.A 200 μl sample of whole human blood (approximately 5 x 106 leukocytes/ml)typically yields 6 μg of DNA in 200 μl water (30 ng/μl) with an A260/A280 ratio of1.7–1.9.For more information about elution and how to determine DNA yield, purity, andlength, refer to pages 24–25 and Appendix A, page 50.