biochrom Libra S21 - Basic Modes; Absorbance (1.1); Transmission (1.2); Factor Concentration (1.3)

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6 Libra S21/S22, English Issue 02 - 04/2004
Basic Modes (1)
Absorbance (1.1)
Absorbance mode measures the amount of light that has passed through a sample
relative to a blank (this can be air). The procedure is as follows:
• Enter appropriate wavelength and press OK (F3)
• Insert reference and press green run key. The cell changer, if fitted,
automatically moves to position 2 and displays the result for the reference
measurement (0.000)
• Xenon lamp based instruments are “press to read”, whereas deuterium /
tungsten lamp instruments measure continuously. Thus to monitor sample
stabilisation, the simple kinetics mode must be used
• This reference value is used for subsequent samples until changed
• Insert samples as required and press (repeat as necessary)
• To go back and change the wavelength press Method (F1)
% Transmission (1.2)
Transmission mode measures the amount of light that has passed through a sample
relative to a blank (this can be air), but displays the result as a percentage. The
procedure is as follows:
• Enter appropriate wavelength and press OK (F3)
• Insert reference and press green run key
• This reference value is used for subsequent samples until changed
• Insert samples as required and press (repeat as necessary)
• To go back and change the wavelength press Method (F1)
Factor Concentration (1.3)
Concentration mode is used when a conversion factor is known, and converts the
absorbance measurement for a sample at a specific wavelength into a concentration,
by a simple multiplication of absorbance x factor. The procedure is as follows:
• Enter appropriate wavelength and press OK (F3)
• Enter known factor (range 0.01-9999) and press OK (F3)
• To enter a negative factor press – (F1); the reference should have a higher
absorbance than the samples
• Insert reference and press green run key
• This reference value is used for subsequent samples until changed
• Insert samples as required and press (repeat as necessary)
• To go back and change the wavelength or factor press Method (F1)