Good Lab Practice-1

7/30/2019 Good Lab Practice-1

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Good Laboratory Practice



Clothing

• Always wear a laboratory coat (correctlyfastened ) and remove it if you leave the

laboratory



Clothing…

• Wear safety glasses for handling hazardous

chemicals



Clothing…

Wear disposable gloves for handlinghazardous chemicals



Clothing…

• No open-toed footwear in the

labs



Laboratory Wasteisposal

• Only a few “safe” chemicals canbe sent into the natural environment directly

(lab sink or garbage can)



• Chemicals that may be flushed down the sink

must be water soluble,

nonflammable, noncorrosive ,

nonreactive and nontoxic

• If a chemical fails to satisfy even one of these

criteria, it cannot be disposed of in the sink or

the garbage can



Laboratory Waste Disposal… •

The most common errors in waste handling

- Improper labeling of waste; the contents of

the bottles should be listed



Laboratory Waste Disposal…

- Improper segregation of waste; mixingincompatible chemicals in a waste container

can cause a fire or explosion

- Improper storage of waste (eg.Fume hood or metal can)




• The most common errors in waste handling…

- Failing to cap waste bottles or leaving a

funnel in the waste bottle




The most common errors in waste handling…

Accumulation of excessive waste. Ideally, you should have

no more than one bottle of each kind of waste in your lab




• Containers should not react with the waste

being stored

• Often the original container is perfectly

acceptable

• Do not list reactants, only products

e.g. if a cyanide was used in a rxn but all of the

material was oxidized to a cyanate before

disposal, do not list cyanide on the label



Sharp Disposal

Sharp is the term used to describe any itemthat is capable of puncturing the skin

such as syringes, needles, broken glass, etc.



Sharp Disposal…

All sharp disposal containers

should be

• Made of a heavy duty plastic

• Able to close with a tight-

fitting, puncture-proof lid

• Upright and stable during use

• Leak resistant

• Properly labeled



Glassware

• Volumetric flasks

• Volumetric pipettes

• Graduated pipettes

• Graduated cylinders



Volumetric Flasks and Volumetric

Pipettes

• High accuracy and repeatability of

measurements

• Flasks are designed to contain (TC,IN) knownvolume of solution

• Pipettes are generally designed to deliver

(TD,EX) known volume (rarely TC)



Volumetric Flasks and Volumetric Pipettes…

• When you empty pipette you deliver exactly

required volume and you don’t have to worry

about the solution that is left

• Volumetric flask is known to contain required

volume, but if you pour the solution to

some other flask you will never know howmuch of the solution was transferred



Graduated Pipettes and Graduated

Cylinders

• They are designed to deliver requested

amount of solution• Their accuracy is much lower than the

accuracy of volumetric glass

•They are used to measure amounts of auxilliary reagents, like buffers



Classification of Glass

• Volumetric glassware used in labs can

either class A or class B (or non classified)

• Class A is more accurate than class B



• According to ASTM, tolerance of class A1000 ml volumetric flask should be ± 0.3, this

means 0.6 for class B flask



• Cylinder

• B: Class B

• In: to contain

• No idea why this cylinder is calibrated to

contain



• Volumetric pipette

• A: class A

• Ex: calibrated to deliver

• 15 s: 15 seconds

• TS: touching side of the pipette tip to theinside of the flask till solution is delivered



Glass containers

• The USP has four different classifications forglass containers ranging from type I to type NP

• Type I is the best, typically made of borosilicate

glass* least reactive glass

* least pH shift

* highly resistant to temperature changes

(low coefficient of expansion)



Proper Use of Volumetric Glassware

• You must never dry any volumetric glassware

in a drying oven



Proper Use of Volumetric Glassware….

• You must never expose any volumetricglassware (vol. pipette, vol. flask) to sources of heat

• Heat exposure will adversely affect thecalibration

• When measuring volume of solution, the

bottom of the concave meniscusmust be precisely on thecalibration mark



How to Clean Laboratory Glassware

• Cleaning lab glassware is not as simple as

washing the dishes

• It is generally easier to clean glassware if you

do it right away• Tap water and detergents are not

desirable

•

Rinse the glassware with the propersolvent, then finish with a couple of rinseswith deionized water



How to Dry Laboratory Glassware

• Avoid drying glassware with a paper towel or

forced air

• Allow the glassware to air dry on the shelf

• If glassware is to be used immediately after

washing and must be dry, rinse it 2-3 times

with acetone (remove water and evaporate

quickly)



Performing Studies

• It is necessary to educate the individualsperforming studies

• Unique identification of the study and all its

parts• All observations in a study should be

immediately and clearly recorded

•

All records should be in the form of boundnotebooks or on continuously numberedsheets



Performing Studies….

• You should always record your work at the timeyou carry out the experimental work

• You should never make notes on loose pieces orsheets of paper

• You should write in ink, do not use any correctionfluid to repair mistakes

• All entries and corrections should be dated andinitialized

• Do not omit certain data points in order to makethem look more convincing



Performing Studies…



Weighing techniques

• Weighing is a frequent step in analytical

procedures

• Weighing is a common source of error

• Do not assume that the balance has been left

in the proper operating condition by the

previous user

• Calibration: The manufacturer must provide a

set of calibration weights



Weighing techniques….

• The proper receiver for the material must be

selected

• Receivers: weighing bottles, weighing funnels,

flasks, weighing papers

• The weighing funnel is often the most

satisfactory receiver, because it can function

as both a weighing dish and a transfer funnel,

allowing easy transfer to volumetric flasks



Weighing Funnels

•Ensures complete sample transfer

•Sits flat on balance

•Pouring necks designed to fit in volumetric flasks



Proper pipetting techniques

• Take the ambient temperature into account(calibrated at RT)

• Take the sample temperature into account

• Use the largest volume possible

• To get the maximum accuracy: use yourpipette to dispense the volume you need but

do it into a tared container on a balance.Then calculate the actual pipetted volumefrom mass and density



Ideal Solutions

• No change in the properties of the

components other than dilution

•Cohesive forces = adhesive forces

• No heat is evolved or absorbed during mixing

• No shrinkage or expansion

• 100 ml methanol + 100 ml ethanol = 200 ml



Real Solutions

• Cohesive forces ≠ Adhesive forces

• Heat is evolved or absorbed

•

Shrinkage or expansion• 100 ml H2SO4 + 100 ml H2O = 180 ml

• Volume expansion or contraction should be

taken into considerationEg. 20% v/v ethanol in water

Good Lab Practice-1

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