QIAEX II Gel Extraction Kit (500)

A silica-particle-based DNA purification kit from QIAGEN enables extraction and purification of DNA from agarose and polyacrylamide gels, and can also be used to desalt and concentrate DNA from solutions. The method relies on solubilization of agarose and selective adsorption of nucleic acids to QIAEX II silica particles in the presence of high salt, eliminating the need for phenol extraction or ethanol precipitation. The kit is compatible with 0.3–2% standard or low-melt agarose gels run in TAE or TBE buffer and is intended for molecular biology applications.

Each kit contains QIAEX II Suspension, Buffer QX1 (with a pH indicator), Buffer PE concentrate, and a Quick-Start Protocol. DNA molecules of 40 bp to 50 kb are adsorbed to the particles, and non-nucleic-acid impurities such as agarose, proteins, salts, and ethidium bromide are removed during washing. Specifications state a maximum binding capacity of 5 µg DNA per 10 µl QIAEX II suspension, recovery of 60–95% for DNA fragments of 40 bp – 50 kb, and a minimum elution volume of 20 µl. Adsorption efficiency is typically 95% when the binding mixture pH is ≤ 7.5, with the pH indicator in Buffer QX1 appearing yellow in this range and turning orange or violet if the pH exceeds it.

DNA is eluted in a low-salt solution such as 20 µl of 10 mM Tris·Cl (pH 8.5) or water. DNA fragments smaller than 4 kb are recovered with 70–95% efficiency when eluted at room temperature (15–25°C) with a 5-minute incubation, while fragments larger than 4 kb require incubation at 50°C. The purified DNA is suitable for restriction digestion, labeling, ligation, transformation, PCR, sequencing, in vitro transcription, and microinjection. The kit should be stored dry at room temperature (15–25°C) and, when handled appropriately, remains stable for at least 12 months without reduction in performance, capacity, or quality of separation.