CC LEC: PLASTICWARES AND GLASSWARE

• Purpose of laboratory glasswares and plasticwares:

  • Storage
  • Measurement
  • Containment
• Plasticwares:

  • Advantages:
  • Cheaper
  • More durable
  • Greatest advantage: unbreakable
  • Used to store alkaline solutions
  • Preferred for some analyses (ex. testing for heavy metals)
  • Disadvantages:
  • Leaching of surface-bound constituents into solutions
  • Permeability to water vapor
  • Evaporation through breathing of the plastic
  • Absorption of dyes, stains, or proteins
  • Polystyrene:
  • Rigid, clear type of plastic that should not be autoclaved
  • Will crack and splinter when crushed
  • Not resistant to most hydrocarbons, ketones, and alcohols
• • Used in manufacturing: Capped graduated tubes and test tubes
  • Polypropylene:
  • Characteristics:
  • Flexible or rigid
  • Chemically resistant
  • Can be autoclaved
  • Other uses:
  • Several tube designs: specimen tubes and test tubes
  • Specially formulated polypropylene is used for cryogenic procedures; can withstand temperatures down to -190°C
  • Polyethylene:
  • Used in manufacturing: Test tubes, bottles, graduated tubes, stoppers, disposable transfer pipets, volumetric pipets, and test tube racks
• • Disadvantage: may bind or absorb proteins, dyes, stains, and picric acid
  • Polycarbonate:
  • Used in manufacturing: Tubes for centrifugation, graduated cylinders, and flasks
  • Characteristics:
  • The usable temperature range is broad: -100°C to +160°C
  • A very strong plastic but is not suitable for use with strong acids, bases, and oxidizing agents
  • May be autoclaved but with limitations
  • Teflon:
  • Used for manufacturing: Stirring bars, tubing, cryogenic vials, and bottle cap liners
  • Characteristics:
  • Teflon is almost chemically inert
• • Suitable for use at temperatures ranging from -100°C to +400°F (-73°C to 204°C)
  • Resistant to a wide range of chemical classes, including acids, bases, alcohol, and hydrocarbons
• Glasswares:

  • Routinely used clinical chemistry glassware should consist of high thermal borosilicate or aluminosilicate glass and meet the Class A tolerances recommended by the NIST/ASTM/ISO 9000
  • Class A glassware ("A") are preferred for laboratory applications
  • All laboratory utensils used in critical measurement should be Class A whenever possible to maximize accuracy and precision and decrease calibration time
  • Preferred because of its chemical stability and clarity
  • Can be heated
  • Allow longer storage of some chemicals
• • It is important to use the correct type of glass for the determinations being made
  • Borosilicate:
  • The most common type of glassware encountered in volume measurements
  • Characteristics:
  • High degree of thermal resistance
  • Has low alkali content and is free from the magnesium-lime-zinc group of elements, heavy metals, arsenic, and antimony
  • Commercial brands:
  • Pyrex: Strain point 515°C
  • Kimax: Strain point 513°C
  • Precautions for heating
  • High Silica Glass:
  • Silica fused to quartz
  • More expensive than borosilicate glass
• • Cleaning glasswares and plasticwares:
  • In most laboratories, glass or plastic that is in direct contact with biohazardous material is usually disposable
  • If not disposable, it must be decontaminated
  • Precautions for cleaning glassware
• • Use: Spectrophotometer cuvettes
  • Alumina-Silicate Glass:
  • Characteristics:
  • With aluminum oxide
  • Strengthened chemically rather than thermally
  • High-impact, extremely strong glass
  • Greater chemical durability and can withstand higher operating temperatures
  • Common Use: manufacture of calibrated centrifuge tubes
  • Corex:
  • Six times stronger than borosilicate glass and will outlast conventional glassware by tenfold
  • Radiation-resistant
  • Resists clouding and scratching better
  • Uses: High-precision analytical work, optical reflectors and mirrors
• Acid-Resistant & Alkali-Resistant Glass:

  • Boron-free
  • A.k.a. "soft glass"
  • Used for strong acid or alkaline solutions
  • Vycor® (No. 7900):
  • Made up of fused silica
  • 2 in 1 characteristics: heat-resistant and chemically inert
  • Unique characteristics
  • Low Actinic Glass:
  • Characteristics
  • Commonly used in containers used to store control material and reagents
  • Soda-Lime Glass:
  • A.k.a. flint glass
  • Characteristics
• Mixture of oxides of silicon, calcium, and sodium:

  • Soda = sodium oxide
  • Lime = calcium oxide
• Characteristics of this glass:

  • Most inexpensive
  • Readily made into variety of glassware types
  • Less resistant to high temperatures and sudden changes in temperature
  • Fair resistance to chemical attack
  • Minerals can be leached from the glass into stored solutions
• Common uses:

  • Volumetric flasks
  • Stirring rods
  • Single-use pipets or test tubes
• Graduated Cylinders:

  • Long, cylindrical tubes held upright by an octagonal or circular base
  • Calibration marks along its length
  • Semi-accurate
  • Extremely convenient for rapid liquid measurement
  • Should NEVER be heated
• Burets:

  • Long cylindrical graduated glassware with stopcock at one end
  • Glass for acid, rubber for alkali
  • Extremely accurate in dispensing aliquots of a solution
  • Used for dispensing a specific volume of liquid during a titration
• Volumetric flasks:

  • Round lower portion with a flat bottom and a long thin neck with an etched calibration line
  • Calibrated to hold one exact volume of liquid
  • Lower meniscus near the calibration line requires a pipet for adding final drops
  • Generally used for preparation of standard solutions and measuring liquid volume accurately
• Pipets:

  • Glass or plastic utensils used to transfer liquids, can be reusable or disposable
• TC (To Contain) pipets:

  • Must be refilled or rinsed out with appropriate solvent after initial liquid drainage
  • Holds a particular volume but does not dispense that exact volume
  • Examples: Sahli-hemoglobin pipets, Long-Levy pipets
• TD (To Deliver) pipets:

  • Designed to drain by gravity
  • Calibrated to deliver the designated amount of fluid
  • Must be held vertically and tip placed against the side of the container
  • Examples: Mohr pipet, Serologic pipet, Volumetric transfer pipet
• Blow-out pipet:

  • Continuous etched ring or two small, close, continuous rings near the top
  • Last drop of liquid should be expelled into the receiving vessel
  • Never pipet or blow out solutions by mouth, always use an appropriate pipetting aid
• Self-draining pipet:

  • Contents drain by gravity
  • No frost/etched/double lines
• Measuring/Graduated pipets:

  • Calibrated to distribute fractional quantity of liquid
  • Used for measurement of reagents, making dilutions, and transferring solutions
• Automatic & Semi-automatic pipets:

  • Micropipet: pipet with pipetting capability of less than 1 mL
  • Automatic macropipet: dispenses greater than 1 mL
• Air Displacement pipets:

  • Relies on a piston for creating suction to draw the sample into a disposable tip
  • Piston does not come in contact with the liquid
  • Tip is placed into the liquid to be aspirated and dispensed from
• Positive Displacement pipets:

  • Uses a Teflon-tipped plunger inside the capillary
  • Capillary tips are reusable and carryover is negligible if properly maintained