Photometry

Extinction

• Quick and easy direct measurement method Harmless and stable, since no chemicals have to be used Provides information about sample purity
• Harmless and stable, since no chemicals have to be used
• Provides information about sample purity

Fluorescence

• High sensitivity; therefore particularly suitable for the analysis of samples with low concentrations; saves valuable sample material
• High accuracy due to the high specificity for the target molecule

Kinetics

• Measurement over a period of time with reliable temperature control of the Reactions through the cuvette shaft with integrated Peltier element
• Time-saving processing as the time window can be adjusted after the measurement, including statistical data about the curve fit

Fluorescence Samples

UV-based quantification of nucleic acids has limits which can be bypassed by using fluorescence detection, qPCR, or chip-based capillary electrophoresis systems.

The amount of nucleic acid is calculated based on the intensity of the fluorescent signal. For excitation and detection, fluorimeter or a photometer with a fluorescence module is required.

Nucleic acids quantification via fluorescence is based on fluorescent dyes which bind to the nucleic acids. Only the complex consisting of nucleic acid and dye is excited by light of a specific wavelength (dependent on the dye) and will subsequently emit light of a slightly longer wavelength.

Kinetic Process

The enzymatic activity measurements quite often need to be performed at a specific temperature. For reducing measurement variations, the cuvette shaft of the spectro meter needs to be temperature-controlled. Enzyme activity [U/mg] can be done time-consuming by hand or by fast calculation of the spectrometer. Software based »linear regression« is useful for the accurate definition of the linear range of a kinetic measurement.

Transmission Samples

Transmission is calculated from the ratio of I (light leaving the cuvette) and I0 (light entering the cuvette) and expressed in percent as %T.

As an alternative data output to absorbance or concentration, the pre-programmed method »Transmission« of BioPhotometer D30 and BioSpectrometers provides you the percentage transmission of the sample. When using the »Transmission« method, the light trans mittance of the sample is given as T% instead of the absorbance, which is directly used to calculate the sample concentration. These raw data can also be used as a basis for further own calculations.

T = I/I0
%T = I/I0 * 100
The photometer automatically calculates the absorbance
(A) from the measured transmission (T).
A = -log10T = lg(I0/I)