If a lab technician dilutes a blood sample with tryptan blue by 1:1 and counts 100 cells in 5 large squares, what is the resulting cell concentration?

To determine the resulting cell concentration when a blood sample is diluted and counts are made, the dilution factor and the number of counted cells must be considered carefully.

In this case, a 1:1 dilution means that the sample has been diluted by a factor of 2. If the technician counted 100 cells in 5 large squares of a counting chamber, the total number of cells counted is 100.

The total volume in which cells are counted needs to be understood in conjunction with dilution. Since 5 large squares are counted, and typically each large square in a hemocytometer represents a specific volume, we need to calculate total volume for accurate concentration. Conventionally, one large square of a hemocytometer represents a volume of 0.1 mm³ or 0.0001 mL. Thus, 5 large squares would represent 0.5 mm³ or 0.0005 mL.

Next, we apply the following calculation for concentration:

1. Calculate the concentration in the diluted sample:

• Cell count: 100 cells

• Volume counted: 0.0005 mL

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\text{Concentration (cells/mL)} = \frac{\text{Number of