Guanidine and ethanol, both introduced during the prep, can reduce the A260/A230 ratio. Following the protocol will ensure these components are removed. Additionally, some particulates may elute that affect the ratio as well. If this is the case, an additional 15- second spin of the eluted DNA prior to evaluation by spectrometry (Nanodrop®) should help. Withdrawing the DNA sample from the top of the sample can help to avoid transferring any particulates.