System information

4 Absorbance

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3. Touch the white text button to select a protocol or modify the displayed parameters. See

Figure 4-3(B).

4. Single or dual wavelengths can be selected by toggling the WAVELENGTH button. See

Figure 4-3(C).

5. Touch the WAVELENGTH FILTER SELECTION button to select a wavelength. There is an

option for each of the installed filters. For custom filters, select either position A or B.

6. Touch the PLATE button and select wells to be read. Green is selected, grey is deselected,

and REF is for reference. See Figure 4-3(D).

7. Touch the DOOR button to automatically open the instrument door. See Figure 4-3(E).

8. Place the sample plate on the Microplate Sample Tray. The A1 well must be at the top right

corner.

9. Touch the DOOR button again to retract the sample plate back into the instrument.

10. Touch the START button. See Figure 4-3(F).

11. To name the results file, touch the EDIT button to activate the keypad. Enter the results file

name and touch the OK button when editing is complete.

12. Touch the OK button on the dialog box. The Modulus™ Microplate Reader will automatically

begin reading samples.

13. To interrupt a reading at any time, touch the STOP button.

14. Remove the sample plate after the reading is complete.

REMINDER: To prevent evaporation and spills,

remove

the sample plate from the

instrument when a reading is complete.

4.4 Ratiometric Assay

For ratiometric assays, two wavelengths can be selected for each well reading. Only OD values

at each wavelength or a ratio of the two readings appear on the RESULTS screen. For more

details on absorbance results, see Section 4.5.

4.5 Absorbance Data

Single wavelength absorbance data can be displayed in three different units: Optical Density

(OD), Percent Transmittance (%T), and Percent Absorbance (%A). Data exported to .csv format

is only in OD units. To view the different units in the RESULTS screen, toggle the button

corresponding to the unit type.

Data calculations:

Transmittance (T) =

%T = 100T

OD = -log10

(A)

Absorbance = 2 – log10

(%T)

I is the light intensity at a specific wavelength that has passed through the sample. I

is the light

intensity before it enters the sample.

NOTE: The maximum OD value of 5.0 means there was zero transmittance.