Accuracy of manual counts with an hemacytometer depend on:
HYCOR: Kova system for standardized urinalisys No 87144 (expect 10% variability or more)
Hycor Biomediacal Inc.
Garden grove CA 92841
Hemacytometer Fisher scientific No 02671 5
Dilute your cell sample in Trypan Blue dye exclusion medium. Dead cells will be blue, live cells will be birefringent. Suggested dilution 1:20 (5µl cell suspension in 95 µl Trypan Blue).
Carefully and continuously fill evenly at once the hemacytometer chamber.
Leave undisturbed for 1-2 min. (If you need to leave for longer, use a humid chamber). This will allow deposition of the cells on the counting plane.
Count under the microscope two 1x1x0.1 mm areas (delimited by a double line; nine small squares), from two chambers. Ideally you should count more than 200 cells and less than 500 per chamber.
The number of cells per 1x1x0.1 mm areas = cells x 1*10-4 cm3 (1*10-4 ml).
With a 1:20 dilution the easy count is:
number of cells in two 1mm squares divided by 10 = cells x 106 / ml.
(2 squares / 2 x 20 x10,000 / 1,000 = 106 cells / ml)
(2 squares x 10 x 10,000 / 1,000 = 106 cells / ml)
(2 squares x 100 = 106 cells / ml)
(2 squares / 10 = millions / ml)
If your cell suspension is way above 500 / square, count as many smallest squares you can, calculate the mean: this number multiplied by 0.9 will approximate the number of millions / ml.