Module 3 — Basic Laboratory Skills

What four major types of hazards may be encountered in a laboratory?

Chemical hazards, biological hazards (biohazards), electrical hazards, and fire hazards.

What safety training must laboratory personnel receive?

An initial safety briefing; instruction on handling chemicals, biohazards, and waste; training on emergency equipment; and updated training when conditions change. Competency should be checked before independent work.

What is personal protective equipment (PPE), and what examples are used in laboratories?

Equipment worn to protect against specific hazards, including safety glasses, splash goggles, protective gloves, laboratory coats, and closed-toe shoes.

When should safety glasses versus splash goggles be used?

Safety glasses with side protection are suitable when splash risk is low; splash goggles provide greater protection when there is a higher risk of liquids splashing.

How should laboratory gloves be selected?

Choose gloves based on the hazards involved. Latex provides a basic barrier, chemically resistant materials are chosen based on chemical compatibility and penetration time, and thermal gloves protect against extreme temperatures.

What is a Safety Data Sheet (SDS)?

A document describing a chemical's hazards, storage requirements, physical properties, reactivity, first-aid measures, and disposal precautions. It must be accessible before the chemical is used.

When should a chemical fume hood be used?

When an experiment may release hazardous gases or vapours or involves hazardous volatile or flammable chemicals requiring ventilation.

What are biosafety levels (BSL), and how are they classified?

Four laboratory containment levels, BSL-1 through BSL-4, assigned according to the biological agents' hazards and exposure risks. Higher levels require stricter containment and training.

What characterizes BSL-1 laboratories?

They handle biological agents not typically associated with disease in healthy adults, with minimal hazards. Examples in the slides include nonpathogenic E. coli and baker's yeast.

What characterizes BSL-2 laboratories?

They handle agents posing moderate health hazards, including some bloodborne pathogens. They require additional protective equipment, restricted access, safe sharps handling, and biological safety cabinets for aerosol-generating procedures.

What characterizes BSL-3 laboratories?

They handle agents that may cause serious or potentially lethal disease through inhalation. Requirements include controlled access, biological safety cabinets, negative airflow, and specialized containment.

What characterizes BSL-4 laboratories?

They handle the highest-risk agents, including those capable of causing life-threatening disease with limited treatment options. Features include isolated facilities, specialized protective systems, and extensive decontamination procedures.

What is the difference between a chemical fume hood and a biological safety cabinet (BSC)?

A fume hood protects workers from hazardous chemical vapours; a BSC uses controlled airflow and filtration to reduce exposure to biological aerosols. Some BSC classes also protect the samples.

How should biological, chemical, and broken-glass waste be handled?

Biological waste goes into labelled biohazard containers for appropriate decontamination; chemicals follow hazardous-waste regulations; broken glass goes into designated rigid containers.

What do the nine Globally Harmonized System (GHS) hazard pictograms represent?

Oxidizer, serious health hazard, environmental hazard, compressed gas, flammable material, explosive material, acute toxicity, corrosive material, and general irritation or harmful effects.

What is a cleanroom, and how does it prevent contamination?

A controlled environment designed to reduce airborne particles and microorganisms. It regulates temperature, humidity, and pressure, uses airlocks, and filters supplied air through HEPA filters.

What does HEPA stand for?

High Efficiency Particulate Air; HEPA filters remove airborne particles and help protect cleanroom environments and biological safety systems.

Why is a laboratory notebook important?

It creates a permanent record of an experiment so procedures, observations, results, and conclusions can be reviewed and the work can be reproduced.

What structural features should a laboratory notebook have?

Bound, permanently numbered pages; descriptive experiment titles; links between nonconsecutive pages; and spaces for researcher and witness signatures and dates.

What information should a complete laboratory notebook entry contain?

Title, appropriate hypothesis, materials and equipment details, procedures and calculations, observations and results, labelled figures and tables, conclusions, and relevant references.

How should mistakes and blank spaces be handled in laboratory notebooks?

Write entries chronologically. Cross out mistakes with one line so the original remains legible; cross out unused spaces diagonally; initial and date all corrections.

Why are laboratory equipment usage logs important?

They record when and how equipment is used, helping schedule access, estimate its remaining useful life, and support equipment management.

What four common variables are measured in biotechnology laboratories?

Volume, mass, temperature, and pH, each requiring suitable measuring instruments.

What are the relationships between litres, millilitres, and microlitres?

1 L = 1,000 mL = 1,000,000 µL; 1 mL = 1,000 µL.

What is a graduated cylinder, and how is its volume read?

A vessel used to measure moderate liquid volumes. Read the bottom of the meniscus at eye level and select the smallest cylinder that can hold the required volume.

What is a volumetric flask, and how does it differ from a graduated cylinder?

A narrow-necked flask with a calibration mark for preparing one precise final solution volume. It is more accurate for this purpose than an ordinary graduated cylinder.

What are vacuum-assisted pipets used for?

Measuring and transferring liquid volumes, commonly around 1–25 mL, using a bulb or pump to draw liquid into the pipet.

How do Pasteur pipets, plastic transfer pipets, and volumetric pipets differ?

Pasteur pipets are usually ungraduated glass pipets for transferring liquids; plastic transfer pipets have an integrated bulb; volumetric pipets deliver a specific volume very accurately.

What is the difference between Mohr and serological graduated pipets?

Mohr pipets retain a residual volume that should not be expelled beyond their graduation limits; serological pipets are designed to deliver their full contents, including the final drops.

What types of vacuum-assisted pipet pumps are described?

Rubber bulbs, tri-valve fillers with three pinch valves, manual thumb-wheel pumps, and motorized pipet pumps with suction and delivery controls.

What is a micropipet, and what are its common volume ranges?

A precision instrument for dispensing small liquid volumes, usually 1 mL or less. Common ranges are 0.5–10 µL, 2–20 µL, 20–200 µL, and 100–1,000 µL.

How do you select an appropriately sized micropipet?

Choose a pipet whose operating range includes the desired volume, preferably near its middle or upper range, because the slides note reduced accuracy near the bottom of its range.

What is forward pipetting, and what is the purpose of the two plunger stops?

Press to the first stop before drawing up liquid, release gently to aspirate, press to the first stop to dispense, then to the second stop to expel residual liquid. Change tips between reagents.

Why are disposable micropipet tips replaced between reagents?

To prevent cross-contamination between solutions, samples, and experiments.

What is a burette, and when is it used?

A long graduated glass tube with a stopcock at the bottom, used to accurately dispense and measure variable liquid volumes, especially during titration.

What are Erlenmeyer flasks used for?

Mixing and swirling liquids without spilling and growing liquid cultures. Their approximate graduations are not suitable for highly precise measurements; some culture flasks have baffles to improve agitation.

What are reagent bottles and Wheaton bottles used for?

Reagent bottles store laboratory solutions. The slides describe Wheaton bottles as suitable for storage but warn that the examples shown are not made of heat-resistant glass for heating or autoclaving.

What are the relationships between kilograms, grams, milligrams, and micrograms?

1 kg = 1,000 g; 1 g = 1,000 mg = 1,000,000 µg.

How do analytical, mechanical, and electronic balances differ?

Analytical balances measure very small masses precisely and often have draft shields; mechanical balances compare masses physically; electronic balances provide digital measurements.

Why are draft shields and vibration-resistant surfaces used with analytical balances?

Air movement and vibration can affect highly precise mass measurements, so these features reduce interference.

Why must weighing paper or weigh boats be used when weighing chemicals?

They prevent direct contact with the balance and reduce contamination. Excess chemical removed from a stock bottle should not be returned to it.

What temperatures are commonly used for laboratory experiments and reagent storage?

Room temperature about 22°C; human body temperature 37°C; refrigeration 4°C; freezer −20°C; ultralow freezer −80°C; liquid nitrogen approximately −196°C.

How do alcohol and infrared thermometers work?

An alcohol thermometer measures temperature through the expansion of coloured liquid; an infrared thermometer measures temperature remotely when aimed at a target.

What is pH, and what mathematical relationship defines it?

pH measures acidity in terms of hydrogen ion concentration: pH = −log10[H+], with [H+] expressed in moles per litre.

Why does temperature matter when measuring pH?

The pH of a solution can change with temperature, so pH specifications and measurements should consider temperature.

How does a pH meter work, and how is it calibrated?

It compares signals from a hydrogen-ion-sensitive electrode and a reference electrode. Calibrate using standards such as pH 4, 7, and 10 that bracket the expected sample pH.

How should a pH electrode be handled before and after measurement?

Rinse with distilled water, place it in the solution until the reading stabilizes, rinse afterward, and store in the appropriate solution to prevent the electrode drying out.

What is instrument calibration, and how are micropipets and balances checked?

Calibration verifies measurement accuracy and precision. Micropipets can be checked using the mass of dispensed water; balances are checked using standard weights. Calibration records should be maintained.

What are the basic steps for washing laboratory glassware?

Scrub with laboratory detergent and a suitable brush, rinse thoroughly with tap water until free of detergent, rinse with distilled water, and allow to dry.

What is the difference between disinfection and sterilization?

Disinfection eliminates or reduces most microorganisms; sterilization eliminates all forms of microbial life, including resistant spores.

What is an autoclave, and what conditions are listed in the presentation?

An instrument using pressurized steam for sterilization. The slides describe approximately 121°C and 15–20 psi, with cycle duration depending on the load.

What is the difference between dry and liquid autoclave cycles?

Dry cycles are used for suitable instruments and empty containers; liquid cycles are designed for sterilizing solutions. The appropriate cycle depends on the material and volume.

How are heat-sensitive solutions sterilized according to the slides?

By membrane filtration, commonly using a 0.22 µm filter; syringe filters are suitable for smaller volumes and vacuum filter units for larger volumes.

What are the uses of bleach, alcohol, and germicidal ultraviolet light in laboratory cleaning?

Bleach can disinfect surfaces and degrade DNA; 70% alcohol is used for exposed-surface disinfection; germicidal UV is used in specialized workstations to damage microbial DNA.

What four essential details should appear on a prepared solution label?

Solution name, concentration, date prepared, and name or initials of the person who prepared it. Hazard and ownership information may also be required.

What do the colours of the NFPA hazard diamond mean?

Blue = health hazard; red = fire hazard; yellow = reactivity/instability; white = special hazards. The numerical hazard scale runs from 0 (minimal) to 4 (most severe).

What are significant figures, and why do they matter?

Digits reflecting the precision of a measurement. Calculated results should not imply greater precision than the original measurements.

How do significant-figure rules differ for addition/subtraction and multiplication/division?

For addition or subtraction, round to the fewest decimal places in the measurements; for multiplication or division, round to the fewest significant figures.

What is scientific notation, and how are 1,050,000 and 0.0000102 written?

Scientific notation expresses numbers using a coefficient and a power of ten: 1.05 × 10^6 and 1.02 × 10^−5.

What metric prefixes and powers of ten are listed in the presentation?

Kilo (k) = 10^3; deci (d) = 10^−1; centi (c) = 10^−2; milli (m) = 10^−3; micro (µ) = 10^−6; nano (n) = 10^−9; pico (p) = 10^−12.

What are solute, solvent, and aqueous solution?

Solute = substance dissolved; solvent = substance doing the dissolving; aqueous solution = a solution whose solvent is water. The slides recommend distilled or ultrapure water for solution preparation.

What do 5% (w/v) and 5% (v/v) mean?

5% w/v means 5 g of solute per 100 mL of final solution; 5% v/v means 5 mL of liquid solute per 100 mL of final solution.

What formula is used to dilute a stock solution?

C1V1 = C2V2, where C1 and V1 are the starting concentration and stock volume, and C2 and V2 are the desired concentration and final total volume.

How much of a 10% stock solution is needed to prepare 100 mL of a 2% solution?

20 mL. Using C1V1 = C2V2: (10%)(V1) = (2%)(100 mL), so V1 = 20 mL; dilute to a final volume of 100 mL.

What does a 10× stock solution mean?

The stock is ten times as concentrated as the working solution. To prepare 1×, dilute one part stock to ten parts final total volume.

What is a mole, and what is Avogadro's constant?

One mole contains approximately 6.02 × 10^23 particles; Avogadro's constant is the number of particles per mole.

What is molar mass, and how is it calculated?

The mass of one mole of a compound in g/mol, calculated by adding the atomic masses of all atoms in its chemical formula.

What is molarity, and how is it different from a mole?

Molarity (M) = moles of solute per litre of final solution. A mole measures quantity of substance; molarity measures concentration.

What formula determines the mass of solute required for a molar solution?

Mass (g) = desired molarity (mol/L) × final volume (L) × molar mass (g/mol).

How is 1 L of 1 M calcium chloride (CaCl2) prepared in the slides?

Using anhydrous CaCl2 with molar mass 110.98 g/mol, weigh 110.98 g, dissolve in less than 1 L of water, and bring the final solution volume to 1 L.

How are compound molar solutions and small-volume dilutions prepared?

For multiple solutes, calculate each required mass separately before dissolving and bringing to final volume. For small dilutions, use M1V1 = M2V2 with consistent volume units and a suitable micropipet.

What is normality (N), and how does it relate to molarity?

Normality is equivalents per litre: N = molarity × equivalents per mole. For acid-base reactions, it relates to the number of H+ or OH− equivalents involved.