This document provides an introduction to basic equipment used in clinical chemistry laboratories, including weighing balances and centrifuges. It describes the types and uses of mechanical and electronic balances for weighing small quantities of substances. It also outlines the components, types (swinging bucket, fixed angle, ultra), and operating principles of centrifuges used to separate mixtures by centrifugal force. Key applications include separating serum from blood and concentrating urine sediment.

1. CLINICAL
CHEMISTRY 1
INTRODUCTION (PART 2)
Prepared by:
LGG, RMT

2. CHEMISTRY
BASIC
EQUIPMENTS

3. ● In a microscope with a fixed tube length the magnification is obtained by
multiplying the objective and ocular magnification.
I. Weighing Balances:
- Used in making solutions or reagents
- Weighing done by comparing an unknown with a known mass.
- Used in clinical lab for weighing small quantities.
● Weight = mass x gravity
● For same gravitational force, weights should be equivalent to
the masses.
● Hence, in actual practice:
Mass ≌ weight (used interchangeably)

4. II. Types of Balances:
A. Mechanical
1. Torsion Balance
- Found in pharmacy
- Uses metal bands to
support weight of the beam
instead of the knife-edge
fulcrum.

5. 2. Double-pan balance
- 2 weighing pans dangling from ends of beam; knife-edge fulcrum
at center.
- Substance to be weighted placed on left pan, while standard
weight on the right.

6. 3. Single-pan balance
- With arms of unequal length
- Knife-edge fulcrum located near the weighing pan.
- Arm w/ 2-3 parallel beams to which different size weights are
attached.

7. 4. Precision balance
- Capable of weighing 1 mg or 1000 ug
5. Microbalance
- Capable of weighing 0.1 ug

8. 6. Mechanical analytical balance
- Also called a “substitution balance”
- single-pan , enclosed by sliding transparent doors, which
minimize the environmental influences on pan movement.
- Substance to be measured placed with a “tarred” (a deduction
from gross weight made to allow for the weight of paper
container) weighing vessel on the sample pan.
- Capable of weighing 0.01 mg

9. II. Electronic Balances
1. Electronic analytical balance
- Single pan balance on arm of movable hanger
- Utilizes magnetic force restoration cells instead of weights
- Position of hanger is monitored by an electrical position-scanning
device
- A microprocessor converts the “compensation current (needed to
restore the pan’s original position)” into corresponding weight value
in a “digital display”
2. Electronic single-pan top-loading balance
- most often self-balancing
- coupled to a computer or recording device
- the beam tilts downward on weighing
- a “null detector” senses the deviation of the beam from the equilibrium
point.

10. ELECTRONIC ANALYTICAL BALANCE
ELECTRONIC SINGLE-PAN
TOP-LOADING BALANCE

11. III. Centrifuges
- Used to separate fractions of a mixture by spinning at high speed in a
circular motion. (centrifugal force)
- Used to separate serum or plasma from red cells
- Used to concentrate urine sediment.
● Ultracentrifuge - used to separate lipid components such as
chylomicrons from other components
● 3 components:
a. Rotor b. Drive shaft c. motor
● Rpm = revolution per minute
➢ Relative Centrifugal force (RCF)
- Force required to separate 2 phases in a centrifuge
- Is the product of radial acceleration & mass of the mixture

12. RFC = 1.12 x 10⁻⁵ x r x rpm²
● R = radius in cm from center of rotation to bottom of tube.
Reported as RFC x g (gravity)
● Centrifugal analyzers utilize centrifugal force for the purpose of mixing
sample and reagents.
3 Types of Centrifuges
a. Swinging buckler or horizontal head
b. Fixed angle or angle head
c. ultracentrifuges

13. ➢ Swinging buckler or horizontal head
a. Centrifugation process
- Tubes at horizontal position
- Particles evenly distributed at
the end of the tube.
b. At rest
- Tubes at vertical position
- Sediments flat w/ supernatant
above it
The unique 6 place horizontal rotor
(swing head) spins at 3, 380 RPM.
SWING HEAD CENTRIFUGES

14. ➢ Fixed angle or angle head
- Holds the tubes at specified angle (25-50⁰)
- Particles move along side during centrifugation
- Forms sediment packed against side & bottom
- Produce less heat * friction than swinging bucket

15. ➢ Ultracentrifuge
- High speed centrifuges
- Used to separate lipoprotein from
serum or plasma
* centrifugal analyzers utilize centrifugal
force for the purpose of mixing sample and
reagents.

16. ➢ Manually operated centrifuges
- Maintenance free
- Independent of external power supply

17. Thank
you