Both methods give basically the same results in the end - but are different in the details. Ethanol needs to be incubated in the freezer for good results, this costs some time. But its easier to dry the sample afterwards, since ethanol is more volatile. Isopropanol is better for larger samples and can be done at room-temperature, incubation times are shorter. But it takes much longer to get rid of the isopropanol residues.

Using chilled solvents is helpful since the solubility of DNA in the cold mixture is ways lower (hence the freezing step with EtOH) than at room-temperature.

The low pH is used to make sure that the phosphate backbone of the DNA is protonated, together with the salt ions this lowers the solubility to make it precipitate.

Hi, Sunil. check here

http://www.qiagen.com/literature/qiagennews/0399/993prah.pdf

good luck

From large volumes is better to precipitate DNA with isopropanol. Also isoprpanol precipitation could be performed at room temperature.

Sergey Sir thanx for the information. Based on the attachment I also want to know why ammonium or potassium acetate is added in low pH (5.2). What is the mechanism behind this?

Both methods give basically the same results in the end - but are different in the details. Ethanol needs to be incubated in the freezer for good results, this costs some time. But its easier to dry the sample afterwards, since ethanol is more volatile. Isopropanol is better for larger samples and can be done at room-temperature, incubation times are shorter. But it takes much longer to get rid of the isopropanol residues.

Using chilled solvents is helpful since the solubility of DNA in the cold mixture is ways lower (hence the freezing step with EtOH) than at room-temperature.

The low pH is used to make sure that the phosphate backbone of the DNA is protonated, together with the salt ions this lowers the solubility to make it precipitate.

Hi, Sunil,

You should use much less isopropanol volume (70-80% of the DNA contain solution) to compare with 200-250% of the ethanol. It is also recommended to use ice-cold propanol for DNA precipitation: the precipitation will be faster. Moreover, I recommend to wash DNA pellet 1-2 times with 70% ethanol after isopropanol precipitation. Good luck!

Previous comments include accurate and very valuable information, so I will not repeat it. I would like to add that, from my experience, high molecular DNA (e.g. chromosomal DNA) has a higher recover rate when precipitated with isopropanol at room temperature, followed by 1-2 wash of DNA pellet with ice-cold 70% ethanol (as recommended by Dr. Pasternak). In contrast, smaller DNA molecules (like plasmid DNA) are better recovered by ice-cold ethanol precipitation. Hope it helped.

The best is 0.54 V of isopropanol, vs. 2 V ethanol. Isopropanol works better on ice, 0 centrigrade. This was demonstrated several years ago using radiolabelled DNA.

One thing we noticed in comparison of ethanol versus isopropanol was in DNA preps using phenol. The isopropanol preps did not seem to remove phenol as well. This could have been the researcher performing the preparations. But we had seen this in several cases. The application was template DNA submitted for Sanger sequencing.

I agree with Doug, isopropanol is not effective in removing organic compounds like phenol or chloroform.. That's why after isopropanol precipitation one should wash 1-2 times with 70% cold ethanol.

The recommendation to use chilled ethanol is mostly lab lore (as far centrifugation in microcentrifuges is concerned). Back in the 80's BRL had a wonderful newsletter called BRL Focus that investigated the factors necessary for efficient precipitation [Zeugin JA, Hartley JL (1985). "Ethanol Precipitation of DNA" . Focus 7 (4): 1–2]. They concluded (and backed up with data) that chilling did not increase the recovery and may in fact decrease it slightly. Length of centrifugation time was the most important factor. As others have stated, the primary benefit of isopropanol is that it only requires an equal volume to carry out the precipitation rather than 2 volumes as with ethanol.

Hi, Sanaj, the volume is very important of you use DNA isolation from a big samples, For effective homogenization and extraction one must use at least 1:8 ratio between material and homogenization buffer. So, in the case of big samples it is a reason to reduce volume by isopropanol. However, I recommend you to wash after isopropanol DNA pellet with 70% ethanol because you can easy dry it before re-dissolving.

Thank u all for ur useful and interesting suggestions. I also referred some references where I came to know that as the temperature of an alcohol-aqueous solution decreases, its dielectric constant also increases, which means the viscosity of the solution increases, which ultimately retards the movement of the nucleic acid aggregate, especially if the aggregate is small (Zeugin and Hartley 1985). Therefore since solubility decreases at lower temperatures, more salts will begin to co-precipitate with the nucleic acids at lower temperatures. Hence can we recommend to carry out ethanol precipitation upto 0°C only to avoid more salt precipitation at temperature below 0 degree? please give ur opinions in this regard.

Right, zero is the best temperature.

On a general basis, we all agree ethanol is preferable to Isopropanol due to the fact that, Isopropanol coprecipitates salts and is less volatile and slow to dry. I agree with Sanjay Kumar above that chilling might even reduce the yield owing to the fact that it will decrease the time of volitity thereby leaving residues that might eventual affect the PCR downstream.

Quite good discuusion of the issue yone can find here:

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0011963

About the temperature, it may dependent form DNA size and amount. I agree that low temperature may increase salt precipitation, but one should was smaples with 70% ethanol to remove slat.

Isopropanol is better because you keep the volume smaller, then you get more DNA during precipitation, which is the goal. Also we wash tree times with 70% ethanol, which improves digestibility and sequencing of DNA. it is published here:

A rapid and simple method for small-scale DNA extraction in Agavaceae and other tropical plants

Miguel Keb-Llanes, Gerardo González, Bartolomé Chi-Manzanero, Diógenes Infante

The file is in my profile.

Precipitation with ethanol is less effective in the presence of phenol. I recommend using phase-lock to minimize contamination of the aqueous phase with organic solvents. The yield and purity of DNA increased dramatically since my co-workers, including inexperienced students, started using phase-lock.

Thank you Dr. Irina Minko. Can you please share some more details on "phase-lock". I have never used this method.

Just to inform about another thread on Researchgate (Isopropanol& DNA) cf.

https://www.researchgate.net/post/DNA_precipitation_with_isopropanol

To Sanul Kumar Sahu: We buy the phase-lock gel from 5Prime. They have two types, heavy and light. The choice depends on the nucleic acid nature and the composition of organic and aqueous phases.

Sorry Sunil, I typed your name wrong...

Salts will get dissolve in ethanol not in propanol ,use half vol for eg if u have 200 ul vol of dna use 100 ul of isopropanol ,if ethanol use 400 ul, ice chilled ethanol will make the pellet fast

Use ethanol if:

You have room to fit two volumes of ethanol to sample in your tube

The sample needs to be stored for a long period of time and will be chilled

You need to precipitate very small pieces of DNA or you have a very low concentration of sample so you want to chill it longer and colder.

Use Isopropanol if:

You have limited in space in your tube and can fit only 1 volume of sample

You need large molecular weight species because incubation at room temperature for short periods of time will not be conducive to precipitating small species of nucleic acid

You are in a hurry and want to accelerate the precipitation of nucleic acids at room temperature

Both are chaotropic agents which destabilize H-bonds and other weaker bonds in macromolecules like DNA and they are precipitated out with salt. Isopropanol is a better chaotropic agent than ethanol and so the vol required for precipitation is much less. One has to remove these reagents for further processing and it is much easier to remove ethanol than isopropanol.

Ethanol is highly volatile when compared to propanol.Low temperature(chilled) will facilitate salt precipitation.

When the cations and negatively charged nucleic acid backbone interact, nucleic acids are neutralized, therefore no longer dissolve in water and precipitate out of solution.

Ethanol which has lower dielectric constant compared to water increases the interaction of the salt and the Coulomb force of attraction between the cations and the negatively charged nucleic acid backbone (that is, the resistance from the solvent’s electric field sufficiently diminishes to permit efficient interaction; the solvation shells surrounding the solute’s charges depletes).

http://bit.ly/1ndv10G

It dependes on the protocol. The kind of salt used to precipited interferes if it is ethanol or isopropanol. Follow xactly what says the protocol you are using.

1. Ethanol is costlier than isopropanol. 

2. Again isopropanol is faster in precipitation of DNA accompanying salts too whereas ethanol needs time and salts are dissolved.

3. Isopropanol works at room temperature while ethanol requires freezing temperature.

4. The longer your incubation time at freezing temperature, the more the yield of DNA in case of ethanol,

5. Ethanol gives about 10 fold higher yield of DNA than that of isopropanol.

So, if the time and costs are the factors, better to choose isopropanol. And if the quality and yield are the concern, ethanol is the best option.  

@Md. Asaduzzaman Shismir Especially regarding the temperatures I recommend you take a look at Zeugin JA, Hartley JL (1985). Focus 7 (4): 1–2: http://www.lifetechnologies.com/content/dam/LifeTech/migration/en/filelibrary/pdf/focus.par.56415.file.dat/focus%20volume%207%20issue%204.pdf

Dear,

It depends on the purpose. I'll suggest you to read about DNA extraction in a Molecular Biology Manual. the classical one is Sambrook...Best,

I agree with Maria. "Molecular cloning, a laboratory manual" (Sambrook J and Russel DW, eds.). Cold Spring Harbor Laboratory, New York, is a great resource.

Also, currently available, on the Cornell website is a pdf resource with lots of details about how ethanol precipitation works. They talk about the various salts that can be used and discuss isopropanol versus ethanol.

http://physiology.med.cornell.edu/faculty/mason/lab/zumbo/files/ETHANOL_PRECIPITATION.pdf

Our lab uses one of three salts where the concentrations are in the DNA solution prior to adding 2.2 to 2.5 volumes of 100% ethanol:

Na-Acetate, 0.3 M

NH4-Acetate, 2.1 M

NaCl, 0.2 M

Then the precipitation is often done at -20 C overnight and the DNA is pelleted down in a 4C centrifuge the next morning.

Hello Stephanie.

I've read the article about ethanol precipitation that you shared with us. I found that they recommend not to use low temperatures during DNA precipitation. Have you compared yields from incubation at room and cold temperatures?