Endy:Victor3 plate reader\Measurement variation

Also see: Victor3 plate reader

I measured the variation in repeated measurements on the plate reader.

Fluorescence

I measured the fluorescence of a well containing E. coli expressing YFP and a well containing untransformed MG1655. Ten measurements were taken over a 5min period.

Variation in repeated YFP measurements

Reading	MG1655.YFP	MG1655
1	108445	8142
2	109492	8320
3	110628	8194
4	109728	8188
5	109334	8304
6	109988	8329
7	110382	8480
8	109248	8205
9	107576	8238
10	107560	8228
Mean	109238	8263
Stdev	1016.07	93.1
CV	0.0093	0.011

Absorbance

I measured the absorbance of the same wells. Measurements were taken over the same 5min period.

Variation in repeated absorbance measurements

Reading	MG1655.YFP	MG1655
1	0.476	0.650
2	0.471	0.651
3	0.469	0.648
4	0.463	0.644
5	0.462	0.643
6	0.465	0.643
7	0.460	0.641
8	0.457	0.639
9	0.458	0.639
10	0.456	0.639
Mean	0.46	0.64
Stdev	0.00623	0.0042
CV	0.013	0.0065

Notes

The absorbance readings for both wells appear to decrease over time. Over a 5 min time course this is unlikely to be due to evaporation. It may be due to settling of the cells in the well. The same effect was not observed for the fluorescence readings.