labware

Course Objectives

• Identify the function of labware pieces used in the clinical laboratory: Understanding the specific roles labware plays in laboratory environments assists in accurate experimentation and analysis.

• Explain TD (To Deliver) and TC (To Contain): Grasping the distinctions between To Deliver and To Contain measurements is crucial for precise laboratory practices and interpreting results correctly.

• Describe glassware cleaning according to specification: Proper cleaning methods are vital for maintaining the integrity of glassware, ensuring safety, preventing contamination, and producing reliable results in experiments.

Definition of Labware

• Labware: Articles or containers specifically designed for laboratory use, often constructed from materials that can withstand various laboratory conditions.

• Uses:

• Testing Procedures: Essential for accurately conducting laboratory tests and experiments.

• Preparing Reagents: Involves mixing chemicals or solutions necessary for tests.

• Storing Reagents: Labware provides safe and effective storage for reagents, which are often critical for laboratory analyses and experiments.

Labware Safety

• Top Safety Rules:

• Label Labware Before Adding Contents: Clear labeling prevents mix-ups and ensures that hazardous materials are identified quickly.

• Always Use Personal Protective Equipment (PPE): Standard safeguards like gloves, goggles, and lab coats reduce the risk of contamination and exposure to harmful substances.

• Store Unused Labware at the Back of the Bench: This minimizes the risk of accidental spills and breakage, creating a safer work environment.

• Carry Test Tubes in a Rack: Using a test tube rack prevents tip-overs and accidents while moving multiple tubes.

• Ensure Correct Preparation of Reagents: Accurate preparation of solutions is vital for obtaining reliable patient testing results and ensuring the validity of experimental outcomes.

Types of Labware

Plasticware

• Advantages:

• Cost-Effective: Generally less expensive than glassware, making it accessible.

• Durable (Unbreakable): Ideal for environments where breakage could lead to safety hazards or loss of materials.

• Flexible Applications: Particularly effective in situations requiring chemical resistance, such as storing alkaline substances.

• Disadvantages:

• Less Stability: Risks such as leaching, permeability, or evaporation may occur.

• Generally Less Clarity Compared to Glass: Not suitable for applications requiring clear visibility of the contents.

Common Plastic Types

• Polyethylene:

• Used for various containers; has limitations regarding heat resistance which may limit its applications.

• Polypropylene:

• Known for its rigidity, heat resistance, and capability of withstanding autoclaving for sterilization purposes.

• Polystyrene:

• Commonly utilized in Petri dishes and microtiter plates; however, it lacks heat resistance, limiting its use with hot substances.

• PVC/Tygon:

• Typically used in tubing applications; known for its flexibility and clarity, making it suitable for fluid transfer.

Glassware

• Types of Glass:

• Borosilicate Glass: Offers high thermal resistance, often exemplified by Pyrex, suitable for heating and contamination-sensitive procedures.

• Alumina-Silicate Glass: Provides enhanced optical properties, often used for applications demanding clarity, although it is pricier.

• Low-Actinic Glass: Protects light-sensitive materials from degradation due to exposure to light.

• Soda Lime Glass: The least expensive option; typically not recommended for storing substances long-term due to its reactive nature.

Measurement Classifications

• Non-Critical Measurements: Involves estimated volumes using less precise devices (e.g., beakers), sufficient for general applications where accuracy is not paramount.

• Critical Measurements: Requires precise measurements essential for accuracy, typically using calibrated glassware to ensure reliable results.

Calibration of Glassware

• Importance: Validating method accuracy using known standards is necessary for confirming results in scientific experimentation.

• Class A Glassware: This type meets stricter calibration standards to assure users of accuracy in measurements.[Volumetric Flask]

To Contain vs. To Deliver

To Contain (TC)

• Specifically designed to hold a specified volume of liquid; however, it typically delivers less due to liquid adhering to the walls of the container, which is crucial for users to understand to avoid measurement errors.

  To Contain (TC)

  • Labeling: Written on the side of all lab glassware.

  • Design Purpose: Designed to contain a certain amount of volume. When transferred to another container, it will deliver less than the indicated volume due to liquid clinging to the side (remaining in the primary container).

  • Transfer Loss: Approximately 0.5-1% of the liquid being transferred sticks to the side walls of the measuring container.

To Deliver (TD)

• Designed to deliver an exact indicated volume; in practice, it often involves delivering a slight excess of liquid to ensure complete transfer of contents, making it suitable for precise applications in laboratory settings.

Key Labware Categories

• Containers: Includes test tubes, beakers, and flasks (including Erlenmeyer and Florence), essential for holding and mixing samples.

• Volumetric Ware: Comprised of volumetric flasks, cylinders, and pipettes designed for accurate measurement of liquids.

• Calibration of Lab Glassware

  • Calibration Temperature: Most glassware for routine lab use is calibrated at 20°C.

  • Definition of Calibration: Validating a method by using a known standard.

  • Temperature Consideration: Liquid and glassware must all be at room temperature for measurement to be accurate.

  • Physical Properties: Remember that liquids expand when hot and contract when cooled.

Specific Labware Examples and Use Cases

• Test Tubes: Available in various sizes for handling biological samples and assays effectively.

• Reagent Bottles: Should be chosen based on compatibility with their contents; it’s essential to avoid using low-quality glass for long-term storage of volatile chemicals.

• Beakers: Best for mixing solutions and estimations rather than for performing precise measurements due to their design.

• Volumetric Flasks: Specifically designed to hold precise volumes and are used in preparing critical standard solutions, ensuring accuracy in concentration.

Meniscus

• Definition: The curvature of a liquid’s surface due to surface tension, which is an important aspect of liquid measurement in labware.

• Measuring: Always ensure that the meniscus is at eye level when reading volume for accurate measurement, as parallax error can lead to miscalculation.

Tolerance of Error

• Definition: The permissible deviation from a specified volume, as noted on the measurement markings of glassware; understanding this is critical for achieving consistent and reliable experimental outcomes.

• Example: A 10 mL flask may have a tolerance of ± 0.025 mL, which indicates the precision expected during measurement routines.

to contain [TD]

Test Tubes

• Material: Can be made from plastic or glass.

• Sizes and Shapes: Available in different sizes and shapes, ordered according to length and diameter (e.g., 10 mm x 75 mm holds about 3 mL).

• Contents: May hold blood, urine, plasma, serum.

• Graduation: May be graduated but not calibrated to be accurate.

• Heating: If tubes need to be heated, choose those made of heat-resistant borosilicate glass (e.g., Pyrex or Kimax).

Reagent Bottles

• Material Considerations: Plastic bottles should be used only for reagents that don’t interact with plastic. Low-quality glass containers slowly release ions into the reagents, so they should not be used for long-term storage.

• Sizing: Bottles should be only slightly larger than the volume of reagent within.

• Light Protection: Opaque plastic or brown glass bottles should be used for light-sensitive reagents.

Beakers (TC)

• Size Range: Available in a wide range of sizes (i.e., 25 mL, 50 mL, 400 mL, etc.).

• Design: Wide-mouthed, straight-sided, and with a pouring spout.

• Uses: Used for stirring, mixing, or heating liquid; ideal for estimating volumes (not for precise measurements).

• Calibration: Not calibrated but labeled to indicate approximate capacity in mL and estimated accuracy (e.g., 250 mL ± 5%).

Erlenmeyer Flask (TC)

• Shape: Flat bottom with sloping sides that gradually narrow.

• Opening: Bottle-like opening, which can be plain or threaded.

• Volume Range: Available in various volumes (10 mL to 4000 mL).

• Uses: Ideal for mixing solutions without the risk of spilling.

Florence Flask (TC)

• Design: Rounded sides and a long neck.

• Uses: Used for holding and heating solutions and reagents.

Volumetric Flask (TC)

• Volume Range: Can be found in various volumes from 5 to 1000 mL.

• Manufacturing Standards: Manufactured to strict standards - To Contain (TC).

• Accuracy: Guaranteed to contain a specific volume at a certain temperature.

• Graduation Line: Etched graduation line indicates the correct fill.

• Critical Measurements: Used for the preparation of standard solutions.

To Deliver (TD)

• Design Purpose: Designed to deliver a precise volume by holding slightly more than the indicated volume on the glassware, ensuring that the accurate volume is delivered.

• Usage: Often involves delivering a slight excess of liquid to ensure complete transfer of contents, making it suitable for precise applications in laboratory settings.

Graduated Cylinder (TD)

• Design: Upright, straight-sided, flared base.

• Calibration: Features calibrated markings for measuring.

• Accuracy: More accurate than beakers and some flasks, but not used for precise measurements – To Deliver.

• Example of Use: Measuring the volume of 24-hour urines.

• Volume Capacities: Range from 5 to 2000 mL.

Meniscus

• Definition: Curvature in the top surface of a liquid.

• Cause: Surface tension draws up the edges of the liquid.

• Measurement: The lowest part of the meniscus should be on the calibration marks.

• Reading Position: The calibration mark must be at eye level for accurate measurement.