Coulter Counter

Question 1

What is a Coulter counter?

What are its components?

Answer 1

device to determine concentrations of different formed elements of blood

Components:

• current generator
• measuring vial
• measuring tube with 70 μm capillary)
• 2 measuring electrodes (1 in vial, 1 in tube)
• 1 auxiliary electrode in tube

Question 2

How does a Coulter counter work?

Answer 2

1. current generator creates current, physiological salt solution (good conductor) closes circuit
2. physiological salt solution is pumped from measuring vial into measuring tube
3. when particles of different resistivity pass through capillary → cross section area A changes → voltage pulse (proportional to volume of particle) due to Ohm’s law
4. pumping out begins when liquid level reaches auxiliary electrode (particles counted twice, but displayed only once)
5. DD counts voltage pulses in preset channel

Question 3

What is a current generator?

Answer 3

source of electric current that has constant output current intensity and its internal R is infinitely large

⇒ according to Ohm’s law the measurable voltage pulse (U = I_gen * R) dependent on connected R

Question 4

What is a integral discriminator?

Answer 4

device that

• lets through pulses of amplitude higher than a certain level, the discriminator level
• blocks those of smaller amplitude

Question 5

What is a differential discriminator?

Answer 5

device that

• lets through pulsed for which the amplitude is between 2 DD levels, the channel
• blocks those of the amplitude outside the channel

⇒ used to make size distribution of pulses

Question 6

What is a multichannel analyzer (MCA)?

What is one of its big advantages?

Answer 6

• many DD circuits working simultaneously
• frequency distribution can be displayed immediately

Question 7

What are 2 solution types important for the proper function of the Coulter counter?

Answer 7

• physiological salt solution: maintains formed elements intact, provides conductivity
• calibration solution: = redcal, contains stabilized human RBC of known conc. for verification and calibration

Question 8

How was the Coulter counter calibrated?

How can the concentrations of all RBC measurements be calculated?

Answer 8

• calibration value h = c_actual/c_measured = c_actual/(n*10⁴/μl)
  
  • n = no. displayed
• c_RBC = n_RBC * 10⁴/μl * calibration value