Basic Laboratory Skills

LIQUID VOLUMES ARE MEASURED WITH:

• Graduated Cylinders – liters & milliliters• Beaker – liters & milliliters• Flasks – liters & milliliters • Pipettes – milliliters• Micropipets – microliters

To Convert Between Metric Units of Measurement

• Move the decimal point left when going to a bigger unit

• Move the decimal point right when going to a smaller unit

Example – 2.50 L = _____ mL (2.50 L x 1000 mL/1L = 2500 mL) Example - 95 mL = _____L (95 mL x 1L / 1000 mL = 0.095 L)

Graduated Cylinders:

• Use to measure volumes > 10 milliliters

• Read volume markings at eye level

• Measurements should be at bottom of the Meniscus (lowest point of concave surface)

Graduated Cylinder Sizes: 10 mL, 25 mL,

100 mL, 250 mL, 500 mL, & 1 L

Pipettes(Straw with Graduations)

• Use when measuring volumes < 10 mL• Select smallest pipette for job to < error• Pipettes maybe volumetric (deliver specific volume) • Serological pipettes deliver graduated amounts

(i.e. 1.2 mL,1.3 mL,1.4 mL…)• Pipettes range in size from 1 mL – 10 mL

• NEVER MOUTH PIPETTE• Use a pipette bulb or pump for pipetting & dispensing the solution

Micropipettes• Micropipettes measure volumes < 1mL

or 10 – 100 microliters (μ)

1 microliter (μ)= 1,000,000 L or 1 L = 1000mL & 1 mL = 1000 microliter (μ )

• Micropipettes have 2 stops controlled by a plunger: Press to 1st stop and allow to fill. Evacuate by pressing past 2nd stop.

Micropipette Tips are used & disposed of after each use

Micropipettes can be checked for accuracy using a balance

Multichannel Pipette

• This pipette holds 4 – 16 tips &

is controlled with one plunger

• It accurately measures and dispenses identical samples at the same time

• This saves time and energy

ACCURACY OF MICROPIPETTES

• A BALANCE CAN BE USED TO DETERMINE IF A MICROPIPETTE IS ACCURATE

• 1.5 mL OF H20 SHOULD WEIGH 1.5 g

• 0.25 mL OF H20 SHOULD WEIGH 0.25 g

• 0.15 mL of H20 SHOULD WEIGH 0.15 g

Review / Practice:

Which instrument would you use to perform

The following measurements:

25 μ ?

125 mL ?

2.5 mL ?

450 μ ?

8.5 mL ?

MICROPIPETTE

GRADUATED FLASK

PIPETTE

MICROPIPETTE

PIPETTE

SECTION TWO

MASS OR WEIGHT

• IS MEASURED ON BALANCES OR SCALES

• STANDARD UNIT OF MASS IS GRAM

• MASS MAY ALSO BE MEASURED IN MILLIGRAM (mg) OR KILOGRAMS (kg)

• 1,000 MICROGRAM (μ) = 1 MILLIGRAM (mg)

• 1,000 MILLIGRAMS (mg) = 1 GRAM (g)

• 1,000 GRAMS (g) = 1 KILOGRAM (kg)

Preparing Solutions:

• Solution is one or more solutes dissolved in a solvent• The substance being dissolved is a solute • The solvent is usually a liquid • Water is the most common solvent• Concentration is the proportion of solute to solvent

Common units of concentration: Mass / Volume, % Mass / Volume, Molarity and X Concentration

MASS / VOLUME

____ G / mL x ____ mL = ____g of solute

concentration volume to be weighed out &

desired desired dissolved in solvent

OR

0.12 g / mL x 100 mL = 12 g of NACL

Measure 12 g NACL, add to solvent up to 100 mL

% MASS / VOLUME __9__% = _______

PERCENT VALUE DECIMAL VALUE OF g / mL

OR

_______ X ________ = _______g of solute

Decimal value Volume measured & added to

(g/ mL) Desired volume desired

OR

0.09 x 100 mL = 9 g NACL

decimal value desired total measure & mix with

(g/mL) (mL) solvent up to 100 mL

MOLARITY [# moles of solute in liter of solution]• 1 mole of NACL = 58.4 (atomic mass units)• 2 moles of NACL = 116.8 “ “• 1 mole of CACl2 = 111 “ “ Volume X Molarity X Molecular = # grams to wanted(L) Desired Wt. of be dissolved

(mol /L) Solute(g/mol) in solvent to volume desired

0.02L x 0.5 mol /L x 111g / mol = 1.1 g CACL2 (w/ solvent to 20 ml)

C1V1 = C2 V2

- IS USED TO CALCULATE HOW TO MAKE A SPECIFIC SOLUTION –

C1 = CONCENTRATION OF STOCK SOLUTIONV1 = VOLUME TO BE USEDC2 = DESIRED CONCENTRATION OF SAMPLEV2 = DESIRED VOLUME OF DILUTED SAMPLE ? 1 L NaCl from 100 mg/mL concentrated sol. 100mg / mL x V1 = 1 mg/mL x 1000mL V1 = 1 mg/ml x 1000 mL or V1 =1000mL / 100 = 10mL

100mg/ml [ or 10ml to 990 ml solvent]

Labeling Solutions• Procedures & protocols vary slightly from lab

to lab, but follow standard protocol

• Laboratory techs must come up with specific procedures for developing reagents & buffers

• Solutions & reagents must be labeled after they’re prepared to avoid error

• All solutions are labeled with at least:

Name & concentration of reagent

Date, Time & Initials of preparer

• Reagents must be stored properly & safely

PPE – PERSONAL PROTECTIVE EQUIPMENT

• Protect yourself & avoid contamination when working with infectious agents & chemicals.

• Wear eye protection, gloves, lab coat & masks.

• Dispose of biohazards in proper containers.

• Follow Aseptic Technique.