General Operation; Bichromatic Differential Operation; Loading And Formatting A Plate - Awareness Technology Stat Fax 4200 Operator's Manual

2.4 General Operation

2.4.1 Bichromatic Differential Operation

The option to operate this instrument using differential absorbance readings is available for
every mode. The absorbance readings at the differential wavelength are subtracted from
the absorbance readings at the operating (primary) wavelength. Use of the bichromatic
differential absorbance values corrects for optical imperfections in the plastic wells and
removes the effects of meniscus and turbidity.
Whenever possible, differential reading is recommended because precision is significantly
improved.
In order to preserve sensitivity, it is important not to choose a differential wavelength where
the chromophore being assayed exhibits substantial absorbance. To test your
chromophore, read a darkly colored solution in the Absorbance Mode at the operating
wavelength with no differential filter, and again at the operating wavelength with the
differential filter selection. If the two absorbance readings are within 10% of each other,
then bichromatic differential reading is beneficial. If the difference between the absorbance
readings with and without a differential wavelength is greater than 25%, then the
chromophore is absorbing at or near the differential wavelength and bichromatic reading at
this wavelength is probably not desirable.
If no bichromatic wavelength is selected, exercise every measure to enhance repeatability.

2.4.2 Loading and Formatting a Plate

The footprint for most 96 well plates and strip trays are similar and will fit the Stat Fax
4200. Test the fit of an empty plate before beginning an assay. Place the plate into the
instrument with well A-1 at the rear right corner so that row 1 is going into the reader first.
As you press the first row back and down you will feel slight tension on the plate stretching
the carrier so that the front fits in. The plate requires a snug fit.
22 Stat Fax ® 4200 Operator's Manual Doc. 4200 Rev. K
Place the plate into the
instrument with well A-1 at the
right rear so that row 1 is
going into the reader first.
When using a single Blank(s)
alw
ays is located in A1.
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