clin chem- colorimetry,

colorimetry

lab technique used to measure the concentration of a solution by the intensity of its color

colorimetry- color change

• serum + reagent (binds with specific proteins in serum) = color change

  • the more intense the color the greater the concentration

visual colorimetry

U/A dipstick

colorimetry machines work on Beer’s law

the concentration of a solution is directly proportional to the amount of light absorbed by that solution and is inversely proportional to the amount of light transmitted thru the solution

machines that use colorimetry

• colorimeter

• spectrophotometer

• dry chemistry analyzers

4 cuvettes needed for spectrophotometer

• blank

• standard

• control

• patient

blank cuvette

• contains reagent only

• used to calibrate the machine to 100% transmittance and 0% absorbance

standard cuvette

• contains standard solution only

• has a known concentration

  • used to calculate patient concentration

control cuvette

• reagent + control solution

• has an acceptable range of vaules

  • tells you if test is valid or not

patient cuvette

• reagent + patient serum

2 ways to calculate patine concentration

• use standard solution directly

• set up calibration curve

dry chemistry analyzers

• measures light reflected off reagent pads then calculates concentration

• includes normal ranges

• serum or lithium heparin plasma pipetted off and onto pads

manual sperm cell count- squares to count

diagonal squares of the center large square ( only one diagonal line)

manual sperm cell count- line rule

• top and right lines are valid

  • left and bottom are skipped