The suspension contains ~16 μm diameter polystyrene microspheres (ρ=1.3 g/cm3), Milli-Q high-purity deionized water, potassium chloride to increase density (25% KCl solution) and <0.1% tween 80 (a surfactant).
The suspension was calibrated by automated Bio-Rad TC10 cell counter at the University of Minnesota Department of Pharmacology. Batch 5 statistics are as follows:
Concentration: 5.0×104 spheres/mL ± 8% (stdev)
The spike suspension is supplied in individual 250 mL capped Erlenmeyer flasks with stir-bars. These flasks are stored dark at room temperature until time of purchase or use. Each flask contains a minimum of 200 mL of usable spike suspension.
Microspheres have a density and chemical resistance similar to that of fossil pollen, and can thus be added to the sample at the beginning of preparation. Spheres are easily recognizable as slightly translucent black-brown balls in the pollen slide.
Microsphere spike next to pine pollen.
Spike solution should be kept tightly capped when not in use. Solubility of KCl at 4 deg C is about 280 g/L, so refrigeration should not cause KCl to come out of solution; however, the high salinity of the solution should preclude microbial growth, making refrigeration unnecessary. Place on a magnetic stir plate at room temperature for at least one hour before use. If not consumed within 18 months from time of first opening, solution should be recalibrated using a hemo-cytometer or particle counter. Appearance of KCl precipitate is also an indicator that evaporation has occurred and suspension concentration should be checked.
If you would like to purchase a bottle of spike, please fill out the pollen spike order form. For questions, contact or .