I partly agree with Mahesh. The high absorbance at 230 nm is probably due to guanidine isothiocyanate, not ethanol. At high concentrations, it will inhibit further enzyme reactions, but some can still be tolerated. See for example the instruction manual of the Machery Nagel Nucleospin Gel and PCR Clean-up kit, available on line .You can ge rid of most of it by performing a second wash with the ethanol wash buffer and wiping the collecting tube as recommended by Mahesh.

There are several reasons but most likely you have ethanol contamination. Next time when you rerun this sample for gel extraction, here is what I follow - I usually use ice cold wash buffer, it protects DNA. After removing wash buffer as per manufacturer instruction- I throw away the waste, wipe it with paper, and again spin it for 30 Sec. Minor issue would be you didnt blank with your buffer, you just used water for nanodrop. If you want to be very precise then rule of thumb is everything should be at same pH.

Please check and quote your ratios : 260/280 and 260/230. 260/230 is always higher than 260/280 for pure dna extraction prep. 230-260-280 should be 1-1.8-1

I partly agree with Mahesh. The high absorbance at 230 nm is probably due to guanidine isothiocyanate, not ethanol. At high concentrations, it will inhibit further enzyme reactions, but some can still be tolerated. See for example the instruction manual of the Machery Nagel Nucleospin Gel and PCR Clean-up kit, available on line .You can ge rid of most of it by performing a second wash with the ethanol wash buffer and wiping the collecting tube as recommended by Mahesh.

Guanidium carryover is remarkably common in gel extraction kits (in my experience).

If you can't do a second on-column wash as suggested by Pierre Béguin (for example, if you've already eluted), you can also simply reprecipitate the DNA: make the DNA solution up to 500ul with H2O, add 50ul of 3M sodium acetate (pH5.5), 10ug of glycogen (optional, increases recovery), and 500ul of room temperature isopropanol. Mix well, leave for 20mins at room temp, then spin in a benchtop (10-15min at max speed) and wash 2x with ice cold 75% ethanol. Air dry, resuspend.

I typically recover ~70-80% of my DNA/RNA, but it's invariably much less salty.

High 230 nm absorption of nucleic acid is generally due to phenolic impurities, carbohydrates and EDTA. Apart from following the suggestions from Mahesh and Pierre, i will suggest you to use ultra pure water and not the elution buffer. Elution buffer generally contain TE and if it is not fresh it may cause this problem.

To Vivek: a) carbohydrates don't absorb at 230 nm; b) contamination of a PCR reaction with phenolics is highly unlikely, unless a huge amount of heavily impure template DNA was used as a template;it would be washed away in the EtOH was anyway; c) the elution buffer provided with the kits at least with the MN kit contains no EDTA (hence no TE) as this may impair further enzyme reactions (ligation, restriction etc.) it is un;ikely to go bad as it is usually made of low concentration (5 mM) Tris buffer c) the thiocyanate that is used to dissolve agarose in PCR + Gel clean-up kits does absorb like crazy at 230 nm

Looks like the 230 absorption was due to GITC. Repeated ethanol washes and wiping the tubes helped. Thanks for all your quick responses

In my experience, it is not any problem. If DNA concentration is quitely high after gel purification , as a result you don't need too high volume , even 5-10uL, it is also ok through dilition by biowater for restriction or ligation reaction downstream. Hope to help