I'm face one problem, that is while taking readings on nano-drop for DNA concentration, I'm getting negative reading. I'm taking same solution in which I have dissolved my DNA so can anybody tell me reasons.
Hi,
Negative measurement means no DNA absorbance difference detected in the samples compare to the blank. The problem could come from either your blank or your samples.
- with your blank make sure you have the same composition with your sample diluent. It is also good to try using new blank just in case your blank is contaminated.
- with your samples, it could be that your samples are contaminated with the DNase or somehow your DNA is degraded. Make sure you mix your samples properly before put them on Nanodrop.
- to get some hints try to measure another DNA samples which diluted in the same diluent just to check if everything is okay with the blank and the machine itself. If everything is okay then the problem must be your DNA samples.
Good luck!
its happen frequently, if the last blank measure has 1 hour or more, if the blank it is contaminated, or if your sample is contaminated (sometimes). You must to try i) to put blank again, clean the arm, Vortexing sample, or restart the program.
Usually this happens if your calibration solution is contaminated with DNA/RNA. Try using a fresh batch of water or whatever solution your nucleic acids are eluted with.
Hi Milind,
Below is one of the suggestions from the Technical Bulletin of Thermo Scientific NanoDrop Spectrophotometers, please also refer to the attached Bulletin for other suggestions:
"Make sure that the measurement sample surfaces are clean before starting the software modules. Dirty sample pedestals may cause erroneous absorbance readings (even negative values) and signal saturation. It is always good practice to first clean the sample surfaces with de-ionized water to remove any dried sample that might be present."
I know this is an old question, but I'm going to share my findings to fix this issue in hopes it will serve someone who encounters it today. :) I had Nanodrop readings where the RNA concentration as well as the 260/280 ratio looked fine, but where the 260/230 ratio was either negative(!) or VERY high (10-20) depending on the sample. I remeasured it, reblanked, nothing helped. The solution was that the sample volume that I used (1 uL) was too low. While they say in the manual that 1 uL is theoretically sufficient, it's better to use 1.5 uL-2 uL. Using 2 uL fixed every weird sample I had. Both ratios were then around 2.0.
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