Eppendorf BioPhotometer - Manual (Page 45)

87
12 Calculation
Conversion key: Calculating the molar concentration
Application: Calculating the molar concentration from the mass concentration and the relative molar mass.
The molar mass is either entered directly or calculated by the device using the number of bases / base pairs
per molecule.
C
mol
= C / N
C
mol
= Molar concentration (calculated)
N = Relative molar mass, in kDa (entered using the key)
If, instead of the relative molar mass, the number of bases / base pairs per molecule has been entered, N is
calculated using the number of bases / base pairs:
dsDNA: N = bp x 2 x 330 x 10 -3
ssDNA, RNA, Oligo: N = b x 330 x 10 -3
N = Calculated relative molar mass, in kDa
bp = Number of base pairs per molecule (dsDNA)
b = Number of bases per molecule (ssDNA, RNA, Oligo)
The unit for molar concentration is programmed for each method using the key.
12.2 Direct photometric determination of protein
Selection for calculation of results:
– Absorbance
– Calculation of the concentration via factor
– Calculation of the concentration via one-point calibration
– Calculation of the concentration via Warburg formula
Calculation of the concentration via facto r
See Section 12.1; Measuring wavelength: 280 nm
When the factor is entered using the key, the unit of concentration which has been programmed must
be taken into consideration.
Calculation of the concentration via standard (one-point calibration)
F = C
S
/ A
S
F = Calculated factor
C
S
= Nominal concentration of the standard (method-specific programming using the key)
A
S
= Measured absorbance of the standard
If the standard multiple measurement (2x, 3x) has been programmed, calculation is based on the
absorbances measured, including the zero value, via linear regression. After the regression has been
calculated, a CV (coefficient of variation in "%") value is formed as a measure of the scattering of the
measured values. If the CV value is greater than 10 %, it appears in the display. In this case, the calibration is
not stored automatically; it must first be confirmed by the user (see Section 12.3).
The calculation of the sample concentration is carried out using the calculated factor:
C = A 280 x F
Calculation of the concentration via Warburg formula
C = 1.55 x A 280 - 0.76 x A 260 for "mg/mL" concentration unit
C = (1.55 x E 280 – 0.76 x A 260 ) x 1000 for " µ g/mL" concentration unit
Conversion
Parameter
Parameter
Parameter
12_Auswertg_e.fm Seite 87 Montag, 20. Februar 2006 11:34 Uhr