Use speed vacuum centrifugation or 2-Butanol precipitate method 

You can use the centrifugal vacuum concentrator.

Hi Mukta,

Use an universal vacuum system

If it is too diluted precipitate with ethanol in the presence of sodium acetate. Adding Butanol works well. It is not precipitation. Add equal volume of Butanol and Butanol absorb water from your  sample. Centrifuge and remove the Butonol Phase  and DNA is in the aqueous phase. repeat the same until you get desired concentration. 

Protocol from Current protocols

CONCENTRATION OF DNA USING BUTANOL

It is generally inconvenient to handle large volumes or dilute solutions of DNA. Water molecules (but not DNA or solute molecules) can be removed from aqueous solutions by extraction with sec-butanol (2-butanol). This procedure is useful for reducing volumes or concentrating dilute solutions before proceeding with the basic protocol.

1. Add an equal volume of sec-butanol to the sample and mix well by vortexing or by gentle inversion if the DNA is of high molecular weight. Perform extraction in a

polypropylene tube, as butanol will damage polystyrene.

2. Centrifuge 5 min at 1200 × g (2500 rpm), room temperature, or in a microcentrifuge for 10 sec.

3. Remove and discard the upper (sec-butanol) phase.

4. Repeat steps 1 to 3 above until the desired volume of aqueous solution is obtained.

5. Extract the lower, aqueous phase with 25:24:1 phenol/chloroform/isoamyl alcohol and ethanol precipitate as in steps 1 to 9 of the basic protocol, or remove sec-butanol by two ether extractions as described in the second support protocol.

Addition of too much sec-butanol can result in complete loss of the water phase into the sec-butanol layer. If this happens, add 1 ⁄2 vol water back to the sec-butanol, mix well, and spin. The DNA can be recovered in this new, aqueous phase and can be further concentrated with smaller amounts of sec-butanol.

The salt concentration will increase in direct proportion to the volume decrease. The DNA can be precipitated with ethanol to readjust the buffer conditions.

Vaccum dryer can increase the concentration of your DNA,,, in other way.. if you use 100 micro l elution buffer for extraction sometimes DNA may be diluted.. try to reduce the amount of dilution buffer.. i used 50 micro in such cases..

i did ethanol precipitation...but now my 260/280 ratio is 1.80 and 260/230 ratio is 1.49.Should i now proceed to PCR.

Don't worry more about the ratios. Go ahead and test. If it is for PCR I wouldn't have advised you to concentrate.

All the best

 Thanks all of u for your guidance

Hi all

if DNA is dissolved in Tris acetate (TE) these methods can be applicable 

Panduranga Rao , how much of the 25:24:1 phenol/chloroform/isoamyl alcohol and ethanol is used after the butanol?

Equal volume to DNA sample