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DNA analysis and quantification have become a common process in these laboratories daily as a starting point of the different procedures being performed in the molecular biology laboratory.
DNA quantification is an important pre-analytical method, which is of great importance for many molecular biological analysis methods and can even determine their success. Often the DNA has to be analyzed in trace amounts of samples, e.g. in medically relevant applications like the detection of cell-free fetal DNA in the maternal circulation or of circulating tumor cells. It is also a routine technique in procedures for translational research such as Next-Generation Sequencing (NGS), Polymerase Chain Reaction (PCR) or Real-Time PCR (quantitative PCR; qPCR), cloning or transfection which initiates the subsequent workflow. In the following, methods for DNA quantification, the appropriate instrumentation and factors that can determine the accuracy of the measurement will therefore be discussed in more detail.

Spectrophotometry is a form of electromagnetic spectroscopy, pertaining to the quantitative measurement of the transmission or reflection properties of a material as a function of wavelength. DNA Spectrophotometers use detectors that record the intensity of a light beam at a range of wavelengths.
DNA spectrophotometers are frequently used for ultraviolet, infrared, and visible radiation, however, they can also interrogate many other elements of the electromagnetic spectrum. Wavelength range (the colors that it can transmit through the test sample) is an important feature of DNA spectrometers. Additionally, the sample-transmission percentage, the logarithmic range of sample-absorption, and occasionally a percentage of reflectance measurement are important features for some applications.

In a solution, DNA spectrophotometers can measure the levels of ultraviolet light absorbed by the bases. DNA and other nucleic acids absorb light at a peak wavelength of 260nm. The amount of light absorbed is proportional to the concentration of DNA in the sample. The concentration is calculated from the amount of transmitted light using the Beer-Lambert equation. To quantify DNA with a spectrophotometer, the DNA should be suspended in a solvent and the spectrophotometer should be blanked with the solvent to correct for any background absorbance.
Spectrophotometers are extremely precise, accurate, and sophisticated devices, which can be used as a benchtop or models in labs or portable for fieldwork