Mechanical Micropipets Laboratory Operations Review 33
Types
Air displacement
Positive displacement
Calibration
Uses suction to aspirate & dispense sample through polypropylene tip. 1- or 2-stop. With 2-stop, button is
depressed to 2nd stop to “blow out.” Tips can only be used once. Seals require periodic lubrication. Follow
manufacturer’s instructions for use.Uses a glass capillary tip fitted with Teflon-tipped plunger. No carryover. Tips are reusable. Plunger setting
must be checked & Teflon tip replaced periodically. Follow manufacturer’s instructions for use.Verify accuracy & precision on receipt, after service or repair, & on regular schedule. Most accurate method
for calibration is gravimetric method (weight of distilled water delivered). Secondary method is spectropho-
tometric (absorbance of potassium dichromate or p-nitrophenol delivered).