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

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__% = _______ OR __9__% = _______ PERCENT VALUE DECIMAL VALUE OF g / mL OR _______ X ________ = _______g of solute Decimal value Volume measured & added to (g/ mL) Desired volume desired 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 SOLUTION V1 = VOLUME TO BE USED C2 = DESIRED CONCENTRATION OF SAMPLE V2 = 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.