A-1 Low concentration of cells or virus in the starting sample

—Enrich the concentration of cells or viruses.

A-2 Insufficient lysis of the samples

—The samples has not been mixed thoroughly with the lysis buffer. It is suggested to thoroughly mix by pulse-vortexing for 1-2 times.

—Insufficient cell lysis caused by the activity decrease of proteinase K.

—Insufficient cell lysis or protein degradation due to insufficient warm bath time. It is suggested to cut the tissue into small pieces and extend the bath time to remove all the residue in the lysate.

A-3 Insufficient DNA adsorption.

—No ethanol or low-percentage instead of 100% ethanol was added before the lysate was transfer to the spin column.

A-4 The pH value of elution buffer is too low.

—Adjust the pH to between 8.0-8.3.

Residual ethanol in the eluent.

—There is residual washing buffer PW in the eluent. The ethanol can be removed by centrifuging the spin column for 3-5 min, and then placing at room temperature or 50℃ incubator for 1-2 min.

A-1 The sample is not fresh.

—Extract a positive sample DNA as control to determine whether the DNA in the sample has degraded.

A-2 Improper pre-treatment.

—Caused by excessive liquid nitrogen grinding, moisture regaining, or too large amount of the sample.

The pretreatments should vary for different samples. For plant samples, make sure to thoroughly grind in liquid nitrogen. For animal samples, homogenate or thoroughly grind in liquid nitrogen. For samples with cell walls that are hard to break, such as G+ bacteria and yeast, it is suggested to use lysozyme, lyticase or mechanical methods to break the cell walls.

The genomic DNA was extracted from different volumes of human whole blood samples by TIANamp Blood DNA Kit. The results are as follow. The results are listed as reference only, the actual extraction results depends on the conditions of samples.