Traditionally DNA concentration has been determined by measuring absorbance of the sample at 260nm. Disadvantages of this method include its poor sensitivity and the impossibility to distinguish between single-stranded and double-stranded DNA.
There are a variety of different DNA and RNA quantification kits available.
PicoGreen is a fluorescent dye that undergoes a dramatic fluorescence enhancement upon binding to dsDNA that can be measured using a microplate fluorometer.
Here we used the Invitrogen PicoGreen DNA quantitation kit together with the Twinkle microplate fluorometer to determine double-stranded DNA concentrations in solution.

All reagents (TE buffer, Lambda DNA standard) were obtained from the PicoGreen dsDNA quantitation kit from Invitrogen. The assay was performed as outlined in the protocol supplied with the kit. Samples were pipetted in a black 96 well plate and excited at 485nm (standard filter). Emission was measured at 535 nm (standard filter).

Using the PicoGree dsDNA kit and the Twinkle fluorometer was possible to detect a concentration of as little as 25 pg/ml double-stranded DNA in solution. This concentration corresponds to the detection limit of the kit determined by the kit manufacturer. An almost perfect line response is achieved over the whole range of measured concentrations.
So the Twinkle is ideally suited to determine dsDNA concentrations with the PicoGreen dsDNA kit.

Kits:

• PicoGreen^® dsDNA Quantitation Kit (Invitrogen)
• RiboGreen RNA Quantitation Kit (Invitrogen)
• RediPlate 96 PicoGreen dsDNA Quantitation Kit (Invitrogen)