[Smriti]

Thanks everyone for your input!
Right now I am looking for a preliminary estimation on % ds DNA recovery from my experiments. So, Qubit looks best to me after reading posts on this thread.

[ETHANol]

With regards to Qubit you have to be careful as a significant portion of your library my not be double stranded DNA. As primers become limiting in the PCR enrichment step bubbles and daisy chains of molecules form as the adapters anneal on fragments with non-complementary inserts.

So if you use Qubit it is extremely important to not do too many cycles of PCR enrichment. Given the exponential nature of PCR this is easier said then done.

[GW_OK]

We use the KAPA Biosciences kit. It comes with standards and everything you need to quant your adapted libs. We use this routinely with the bioanalyzer to QC our libraries before sequencing.

Same thing in my lab. It's the best way to go, I've found.

[NextGenSeq]

We never use our Qubit. All our libraries are QCed by Bioanalyzer to check for adapter artifacts and quantified by QPCR.

If you have a good library and your NanoDrop is calibrated properly the QPCR and OD260 concentration should agree within 20%

[lterhune]

I am looking to purchase one of these- Qubit or NanoDrop, which one is better in terms of accuracy and long run? Please provide your input.

We have used both of these in our lab but almost always go with the Qubit. The Nanodrop seems to be less accurate with smaller concentrations, and can skew dramatically high or low if any contaminants are in the sample. The Qubit is also selective for dsDNA. We have had some minor problems with the Qubit (can be 10-20% off), however, it is much better than any alternative we have. Just make sure to spec your Qubit standards ahead of time, as we received a bad lot once which made our readings up to 50% high (Invitrogen replaced them for free).

[protist]

I am looking to purchase one of these- Qubit or NanoDrop, which one is better in terms of accuracy and long run? Please provide your input.

Personally I would choose the Qubit, while the Qubit will not give you a 260/280 ratio it is far more accurate for low ng quantities. Added to that it is far cheaper. We have been using ours for library and RNA input quantification for over 3 years and have had no problems.

[Smriti]

I am looking to purchase one of these- Qubit or NanoDrop, which one is better in terms of accuracy and long run? Please provide your input.

[BIG_SNP]

Kapa

We use the KAPA Biosciences kit. It comes with standards and everything you need to quant your adapted libs. We use this routinely with the bioanalyzer to QC our libraries before sequencing.

[ETHANol]

The biggest problem here (for me at least) is that I prepare and quantitate the library and then I send it out to a core facility to sequence. It makes it difficult to figure out what goes wrong, why, how it can be fixed/optimized. When I get poor cluster generation I don't even know if it is from too much or too little DNA. I think a lot of people are in this same situation. So we just sort of muddle along looking for something that works and nothing ever really does. Bottom line is the quantification step is a problem. All the methods work and don't work. I use qPCR but as said that has problems too.

[Heisman]

Hi Friends

Thanks all for posting replies. Some people whom I talked here at my place suggested qPCR can be best. Anyone knows whether some company provides any standard for it? Of course I would be trying qubit and bioanalyzer.

Biochembug

For a standard it would be best to use a library (prepared similarly) that you have already sequenced.

[biochembug]

Thanks for reply

Hi Friends

Thanks all for posting replies. Some people whom I talked here at my place suggested qPCR can be best. Anyone knows whether some company provides any standard for it? Of course I would be trying qubit and bioanalyzer.

Biochembug

[protist]

We use Qubit to quantify ng/uL and Bioanalyser to get correct peak size for 10 nM dilution calulations.

[pmiguel]

A search of the forum will find several threads that address this topic.

That said, I don't think there is good answer to this oft repeated question yet.

The problem is not so much with perfect libraries -- where
(1) nearly every molecule is an amplicon (has adapters on both ends)
(2) the size distribution of the amplicons is even
(3) there are aren't small amplicons hidden amongst the large ones (by adapter-adapter annealing?)
(4) the solution is free of substances that confound quantitation.

I think most bench ninjas get to the "perfect library" point quickly and thus can't understand the travails the rest of us mere mortals have to deal with. Sad, because they are the ones who know the right path to traverse to get a good outcome almost every time. But they tend to be completely incapable of describing how they do it in a way someone without their intuition/outlook can absorb.

Anyway, I would say, read those earlier posts to get a sense of the issues you may face as a whole. Don't let the issues paralyze you, just let you knowledge of them guide you.

Each of the techniques you mention does have weaknesses:
(1) The bioanalyzer is not designed to give accurate estimations of the amount of a sample -- rather it would be better at telling you the length distribution. Also, the bioanalyzer lull you into thinking you know more than you do -- specifically it doesn't distinguish between single stranded and double stranded molecules. Further migration of single stranded molecules is slower than I would naively expect, such that ssDNA can run slower than dsDNA of the same length. Nevertheless a very useful tool.
(2) Double stranded fluorescence assays can tell you the amount of dsDNA in a solution. Some fluors, like pico green, barely fluoresce at all in the presence of ssDNA, nucleotides, oligos. Also this assay tends to be insensitive to compounds that light up other assays like a Christmas tree. (eg, phenol with a UV spec). But it still is not perfect. Ethidium bromide, for example, in a library shifted the emission spectrum of a fluor we were using (either ribo green or pico green) so dramatically, we had to purify the sample before it could be quantitated.
(3) qPCR is also impacted by EtBr. At least the type of qPCR that uses a SYBR green assay. Further, the presence of small amplicons mixed in your library (possibly, as mentioned above, complexed with larger molecules in such a way that they do not show up on gels or ds bioanalyzer assays) can cause inaccuracies in this method as well.

--
Phillip

[HESmith]

A search of the forum will find several threads that address this topic.

[aplany]

Qbit

Qbit seems to be the most reliable method for quantification for us.