This document provides information on the use and maintenance of various small lab instruments. It describes 16 common instruments including an ultrasonic cleaner, homogenizer, drying oven, desiccators, pH meter, balance, rotary evaporator, freeze dryer, centrifuge, water bath, melting point apparatus, hot plate, heating mantle, UV chamber, vortex mixer, and filtration unit. For each instrument, it explains its typical uses and provides guidance on operation, maintenance, troubleshooting, and safety precautions.

1. 70th TRAINING PROGRAM OF NITUB

2. Use, Maintenance and
Troubleshooting of Small Lab-
Instruments
Dr. Md Shahinul Haque Khan
Professor (cc)
Department of Chemistry
Bangladesh University of Health Sciences
125/1, Darus salam, Mirpur 1
Emai: khanshahinul@yahoo.com

3. Name of the common Instruments
used in a Laboratory
1. Ultrasonic cleaner
2. Homogenizer
3. Drying oven
4. Desiccators
5. pH meter
6. Balance, Weight box
7. Rotary Vacuum Evaporator
8. Freeze dryer
9. Centrifuge machine
10. Water bath
11. Melting point apparatus
12. Hot plate with Magnetic stirrer
13. Heating Mantle
14. UV Chamber
15. Vortex Mixer
16. Filtration Unit

4. Ultrasonic Cleaner
Ultrasonic cleaning is a process that
uses ultrasound (usually from 20–400 kHz) and an
appropriate cleaning solvent to clean items.
 Ultrasonic cleaning uses cavitation bubbles
induced by high frequency pressure (sound)
waves to agitate a liquid. The agitation produces
high forces on contaminants adhering to
substrates like metals, plastics, glass, rubber, and
ceramics.
 used to clean many different types of objects,
including jewelry, lenses and other optical
parts, watches, dental and surgical
instruments, tools, car fuel injectors, musical
instruments, industrial parts and electronic
equipment. electronic repair workshops.

5. Homogenizer
Used for
 the homogenization of various types of
material, such as tissue, plant, food, soil, and
many others.
 sample preparation step prior to the analysis
of nucleic acids, proteins, Cell, pathogens, and
many other targets.

6. Drying Oven

7. Desiccators
Desiccators are sealable or sealable with vacuum
enclosures containing desiccants.
It is used to
 preserving moisture-sensitive items,
 protect chemicals which are hygroscopic ,
 prevent reaction with water from humidity,
 keep materials in drying condition,
 reduce temperature during moisture determination

9. Vacuum Desiccators

10. UV Blocking Vacuum Desiccator

11. Sizes of Desiccators
1. Desiccator, Glass, Clear, I.D. 110 mm
2. Desiccator, Glass, Clear, I.D. 180 mm
3. Desiccator, Glass, Clear, I.D. 240 mm
4. Vacuum Desiccator, Glass, Amber, I.D. 240 mm
5. Space Saver Vacuum Desiccator, 19.7cm ID
6. Desiccator, Glass, Clear, I.D. 150 mm
7. Cabinet type

12. Desiccant
A desiccant is a hygroscopic substance that induces or sustains a state of
dryness in its vicinity.
Characteristics : chemically inert, non-toxic, water insoluble
Performance efficiency
# ratio or percentage (water storable : mass of desiccant)
# relative humidity of the air or other substance being dried

14. pH meter
It is a scientific instrument used to measure
 the hydrogen-ion activity in water-based solutions,
 the acidity or alkalinity,
 the difference in electrical potential between a pH
electrode and a reference electrode.

15. Electrode:
# pH electrode and
# reference electrode design

16. pH-sensitive glass membrane, 0.4 mm thickness

17. Construction of an electrode
1. A sensing part, a bulb made from a specific glass
2. Internal electrode, silver chloride electrode or calomel electrode
3. Internal solution, usually a pH=7 buffered solution of 0.1 mol/L
KCl for pH electrodes.
4. When using the silver chloride electrode, a small amount of
AgCl can precipitate inside the glass electrode
5. Reference electrode,
6. Reference internal solution, usually 0.1 mol/L KCl
7. Junction with studied solution, usually made from ceramics or
capillary with asbestos or quartz fiber.
8. Body of electrode, made from non-conductive glass or plastics.

19. Selection of pH electrode
The types of pH electrodes are many and various. The epoxy
bodied combination electrode is suitable for the majority of
tests carried out on aqueous solutions.
For other applications, such as low ionic strength, high
temperatures and strongly acidic solutions a more suitable
pH/reference electrode pair may be required

20. Storing the pH electrode
1. After Use - Rinse thoroughly with distilled water.
Short Term Storage - Immerse in storage solution
Long Term Storage - Fit wetting cap filled with storage solution
and replace in original packaging.
2. Electrodes should be stored
a) away from direct sunlight
b) in a vertical position
c) within their specified temperature range
3. Always ensure the electrode is used within its specified
temperature range. Ageing of electrodes used above their
specified temperature is rapid and irreversible.

21. Precautions
1. DO NOT touch the sensitive glass pH membrane or reference
junction. Excess droplets of solution may be removed by gently
blotting with filter paper or tissue.
2. DO NOT wipe the electrode as this may induce an electrostatic
charge

22. CLEANING OF GLASS ELECTRODES
Deposit Cleaning agents
General deposits Mild detergent solution
Inorganic coatings Commercial glass cleaning solution (not strongly acidic)
Metal compounds Acid solution, not stronger than 1M
Oil/Grease Complexing agent (EDTA) or suitable solvent
Resins/Lignins Acetone, alcohol or detergent (not strongly alkaline).
Proteins (blood, etc) Enzyme solutions e.g. Pepsin in 0.1M HCl
Stubborn deposits Weak hydrogen peroxide solution, Sodium Hypochlorite
solution or domestic bleach.
If Electrodes is dried out, (dry deposit of KCl crystals on the electrode body), by
soaking overnight in warm deionised water.
Note: The epoxy bodied electrode should not be cleaned with aggressive solvents.

23. ROUBLESHOOTING GUIDE
FAULT PROBABLE CAUSE ACTION
power a. Battery failure
b. Battery polarity incorrect
a. Replace batteries
b. Refit batteries
Cal error 1, 2 or 3 a. Incorrect value buffer used
b. Contaminated buffer solution
a. Use correct value
b. Use fresh buffer solutions
Cal error No 1 or 2 a. pH electrode defective
b. Same buffer used for 2 point cal
a. Replace pH electrode
b. Recalibrate by 2 point buffer solution
Unstable display pH electrode defective Replace pH electrode
Display shows 1 or -
1 only
a. Intermittant or no connection
b. pH electrode defective
c. Contaminated solutions
a. Check electrode connection to unit
b. Replace pH electrode
c. Replace solutions
Intermittant display Probes not fitted correctly Check connections
I/O switch not
working
a. I/O key not held down >2 secs
b. Batteries not fitted
a. Retry holding key for 2 seconds
b. Fit batteries

24. CHECKING the pH METER FUNCTION
 Adjust temperature to 25°C using the keys.
 Check buffer solution
 pH 7 and the display should read 7 pH.
 pH 4 and the display should read 4 pH.
 pH 10 the display should show 10 pH.
 the run unknown sample to read its pH value.

25. Weighing Scales
These are devices to measure weight or calculate
mass.
a. Spring balances or spring scales: measure
force (weight) of gravity against the force on a
spring. Example: electronic balance, digital scale.
b. A balance or pair of scales: compares masses
by balancing the weight due to the mass of an
object against the weight of a known mass.
Example: Pan balance

26. Installation of a balance
# On a solid, vibration-free surface, away from direct sunlight and at an
constant temperature.
# precisely levelled, using the built-in spirit level:
# Protect the balance from drafts of air. Air moving across the pans will
cause inaccurate readings.
# Always keep the balance and weights clean and dry to protect them
from corrosion.
# Check the weight 10 mg, 50 mg and 100 mg and keep note
Other items
Weighing paper;
Set of calibrating weights;
Dust brush.
Silica blue desiccant

27. Precautions
# Never put materials directly on the pan of the balance.
# Use the weighing container or paper.
# Keep container or the weighing paper in the middle of the pan.
# Clean the balance with a soft, clean brush after use.
# Pans and the working area can be disinfected with 70% ethanol

28. Operating procedure
# Check the power cord
# Keep the balance ‘ON’ for 15 min before use
# Check whether the sensitivity
# Zero the balance with weighing paper keeping door closed
# Put material on weighing paper
# Read the weight of the substance directly from the screen
Note: When the balance is not in use, keep it under an airtight plastic
cover for protection against dust. Place a dish of with blue silica under the
cover to remove humidity from the air. (When the silica desiccant has
turned red, it must be regenerated by heating.)

29. Quality Control
Daily
Using an appropriate milligram/gram weight, check daily that the
weight registered by the balance agrees with the calibrating weights.
Record this check in the logbook.
Annually
Calibration of the balance should be carried out annually or after any
repair or re-siting by a qualified service technician and registered in
the logbook.
Repair of the balance should be carried out by a qualified service
technician.

30. Rotary Vacuum Evaporator
It’s a Laboratory Instruments used to reduce solvent by
reducing pressure at an elevated temperature (less than the
boiling point of the solvent to be evaporated). This
promotes the rapid removal of excess solvent from less
volatile samples.
Parts of the
1. Water bath
2. Evaporating tube coupled with a rotor
3. Condenser
4. Solvent trap
5. Chiller / cooling water
6. Vacuum pump

31. What to do before start rotary evaporator?
Pour the required volume of water to the water bath
Connect the tubing between vacuum pump and condenser
Connect cooling water inlet and outlet tubing
Clamp the solvent trap flask
Connect all the electric cord to the mains
 Keep close the air releasing bulb

32. How to start a Rotary Evaporator?
Turn the mains ON position
Turn the switch of the water bath to ON
Set the desired temperature i.e. 400C
Wait until the bath temperature reached to set temperature
Connect the round bottomed flask with sample to the evaporating tube
Close the air release bulb
Turn on the vacuum pump
Turn on the rotor

33. Quickly evaporating solvents
1. n-Hexane
2. DCM
3. Chloroform
4. Ethyl acetate
5. Methanol
6. Ethanol
Slowly evaporating solvent
1. n- Butanol
2. Water

34. How to turn off the rotary evaporator?
Stop the rotation
Release the vacuum
Take out the flask with semidried sample
Turn off the switch
Close the cooling water tap.

35. Maintenance and care
Distilled water should be used in the heating bath to minimize the
scale build up in the bath. Clean the water bath regularly
To remove algae gunk from the inside of a coiled water condenser, the
condenser has to be removed from the rotavap and the coil is soaked
in a dilute nitric acid solution for a few hours.
The ground glass joint holding the flask does not need to be greased,
If a mechanical pump is used instead of an aspirator to produce a
vacuum, a secondary trap has to be used to prevent that the solvent
destroys the membrane or is absorbed in the oil.

36. Freeze Dryer
Freeze-drying or lyophilisation, lyophilization, or cryodesiccation—
It’s a dehydration process
Solid phase to gas phase (sublime method) i.e. Ice to vapor
It is used to
# preserve a perishable material or
# make the material more convenient for transport.
# dry frozen material under reduced pressure.

37. 1 atm = 101.325 kPa = 760 torr

39. Operating procedure
Turing ON the freeze dryer
 Turn on the mains
 Turn on the refrigerator
 Turn on pump after <- 400C has reached
 until the vacuum has reached < 400 mTorr
 Connect sample and open vacuum bulb

40. Turning OFF the freeze dryer
Release the vacuum
Turning off the pump
Defrost the chamber
Turning off the mains

41. Maintenance and troubleshooting
If the freeze dryer does not obtain a satisfactory vacuum, perform the
following maintenance tests
Gaskets, Tubing, Connections, Sample Valves
A. Ensure the gasket is clean. Apply vacuum grease to the gasket.
B. Check the drain line and ensure the drain plug.
C. Check all rubber vacuum tubing for signs of deterioration or cracking.
D. Check all connections and make sure they are secure and leak tight.
E. Check all sample valves on the drying chamber
F. When checking the sample valves,
g. check the vacuum pump

42. Centrifuge machine
It is a piece of equipment that puts an object in rotation around a fixed
axis (spins it in a circle), applying a potentially strong force perpendicular
to the axis of spin (outward).
The centrifuge works using the sedimentation principle, where the
centripetal acceleration causes denser substances and particles to move
outward in the radial direction.
Objects that are less dense are displaced and move to the center.
Denser particles to settle to the bottom of the tube, while low-density
substances rise to the top.

44. Maintenance and care
Avoiding Rotor Failures
Tube Breakage
Chemical Resistance : If uncommon solvents are used then precautions
should be taken
Aerosol Generation: If any liquid is spilled on a rotor, it will be dispersed
as a particulate mist when the centrifuge is run. Rotor should be
cleaned immediately.
Handling Human Samples: Human blood or blood components can
transmit an infectious disease or virus if the patient or donor carries
these.
Lubricating
Disinfection

45. Water bath
Used to
 incubate samples
warming of reagents,
 melting of substrates
 incubation of cell cultures
 enable certain chemical reactions
 heating flammable chemicals instead of an
open flame to prevent ignition
Precaution
 Do not use moisture sensitive substances
 Use distilled water only
 It should be use inside the fume- hood
 Raise temperature up to 900 C for
decontamination,

46. Melting point apparatus
Used to
 determine the melting point of a
substance.

47. Hot Plate with magnetic stirrer
Used for
 chemical reactions
 making homogeneous solution

48. Heating mantle
Used to
 apply heat to containers
 extract oil using Soxhlet extractor
 prevent excessive temperature
gradients
 distillate solvent
 heat oil bath

49. UV Chamber
Used to
 Set wavelength at 254 nm and
366 nm used to detect the spot or
band sample on the tlc plate

50. Vortex Mixer
The variable rotational speed settings
ranging from 100 to 3,200 rpm
Used to
 properly mix solution in a small vials
 mix the reagents of an assay
 mix an experimental sample and
a dilutant.

51. Filtration unit
Used to
 filter mobile phase
 filter solvent or mixutre
solvents

52. Thank you
for
your kind patience