Lecture 3 - Laboratory Equipment Flashcards
Advantages of using plastic labware
- Less expensive
- More durable/unbreakable
- Glass can be damaged by certain chemicals
Disadvantages of using plastic labware
- Permeability to water vapor
- Evaporation
- Absorption of dyes, stains, or proteins
Advantages of using glass labware
- Less permeable and less absorption
- Easily washable and reusable
Disadvantages of using glass labware
- More expensive
- May corrode or break over time (some reagents may eat away at glassware)
Borosilicate (Thermal-Resistant) Glass
Commercially known as Pyrex, this glass is the most common in laboratory grade glassware.
Resistant to heat, corrosion, and thermal shock.
Alumina-Silicate Glass
- Used for high precision analytical work
- Radiation resistance
- Used for optical reflectors and mirrors
- Not common for lab glassware
Acid-Resistant and Alkali-Resistant Glass
- Used for strong acid and base solutions
- “Soft glass” - much less thermally resistant (compared to borosilicate glass)
Low-Actinic (Amber Colored) Glass
- Reduce the amount of light traveled through them
- Used for light sensitive substances
Flint Glass (soda lime glass)
- Least expensive
- Low thermal and chemical tolerances
- Variety of glassware
- Not generally used for analytical work
Disposable Glass
- Inexpensive
- Not designed to be washed and reused
- Test tubes, glass slides, etc.
Accuracy Tolerances - Class A
Class A is most accurate for measuring liquids.
Tolerances can be as low as 0.08 mL for a Class A 100 mL flask or pipette.
To Contain “TC”
Holds a calibrated volume of liquid
To Deliver “TD”
Disperses a calibrated volume of liquid
Examples of containers and receivers
Beakers, test tubes, erlenmeyer flasks, reagent bottles.
Examples of Volumetric Ware
Pipettes, volumetric flasks, graduated cylinders, burets.
Properties of Beakers
- Wide, straight-sided cylindrical vessel
- Used for general mixing and reagent preparation
Properties of Erlenmeyer Flasks
-Used for preparing reagents and titration procedures
Properties of Test Tubes
- Usually disposable
- May be made of borosilicate glass - resistant to thermal shock and chemical reactions or disposable glass
Properties of Reagent Bottles
- Reagents - chemicals used in the testing process
- Glass or plastic
- Many different volumes
When using volumetric glassware, where should the readings be made?
The meniscus of the liquid level.
Tolerance
Allowable limits within which a volume must lie.
Capacity Tolerance of 0.08 mL (100 mL volumetric flask)
Allowable limits for the volume of a 100 mL volumetric flask would be 99.92 - 100.08 mL
Uses of Volumetric Flask
Preparation of reagents or solution that require high accuracy and precision.
When would a graduated cylinder be used?
To measure volumes of liquids when a high degree of accuracy is less essential (assay/procedure dependent).
When would a volumetric pipette be used?
To transfer a specific volume from one vessel to another.
What are the two volumetric pipettes that are able to deliver multiple different volumes?
Serological and Mohr Pipettes
Pipettes
Instruments used to transfer a specific volume of liquid from one vessel to another.
Manual Pipettes
Pipettes that require a bulb or other device to manually draw up liquid into the pipette.
TD calibrated Volumetric Pipette
Calibrated “to deliver” a fixed amount of liquid via drainage. Should NOT be blown out using a bulb.
TC calibrated Serological Pipette
Calibrated “to contain” a certain amount of liquid. Should be BLOWN OUT using a bulb if entire volume is to be dispensed (TD) double ring
Mohr Pipette
Similar to serological pipette but not graduated down to the tip. Should not be used to dispense the full volume; no blow out required.
Function of Semi-Automated Pipettes
Calibrated to draw up a specific volume of liquid using a manually operated plunger. Can be calibrated for one volume or multiple volumes; use of disposable pipettes.
Ex: MLA Pipette, Pipetman Pipette
Function of Automated Pipettes
Pipettes accurate volumes at the push of a button, but requires disposable pipette tips.
Technology is common in automated analyzers.
What are the two types of analytical balances?
Two pan manual and electronic.
What counterbalance is used in Manual two-pan balances?
Weights that correspond to the weight of DI water.
What counterbalance is used in electronic analytical balances?
Uses electromagnetic force to counterbalance the load.
Define Centrifugation
Separates solid material from liquid material using gravitational force via rapid spinning
Define Precipitate
Solid material or sediment packed in the bottom of a centrifuged tube
Define Supernatant
Liquid/top portion of the centrifuged tube
What are the two most common types of centrifuges?
Conventional horizontal-head centrifuge and fixed angle-head centrifuge.
What is a cytocentrifuge?
A centrifuge that spreads a layer of cells across a special slide producing a small sample size.
How is centrifuge speed measured?
Revolutions per minute (RPM)
With respect to force, how can centrifuge speed be measured?
Relative Centrifugal Force (RCF) (RPMs and centrifugal force generated are expressed as RCF).
What is the RPMs of conventional centrifuges?
<3,000
What is the RPMs of ultracentrifuges?
Up to 90,000 RPMs
When loading a centrifuge, what is important not to forget?
To balance the centrifuge.
