The Basic Skills of the Biotechnology Workplace

• Volume is a measurement of the amount of space something occupies

• Liquid volume can be measured in• Liters (L)• Milliliters (mL) • Microliters (µL)

Converting Units• Often volumes are

measured in one unit of measurement and reported in another

• Using metric units• Need Conversion Factors

To measure larger liquid volumes, technicians usually use a graduated cylinder.

Measuring liquids

Pipets are available that measure volumes between 0.1

mL and 50 mL. Serological pipettes

Pipets are available that measure volumes between 0.1

mL and 50 mL. Transfer pipettes

Reading a graduated cylinder:

Make sure you know the total volume it will hold and the value of each of the graduations.

In the lab, common graduated cylinders include 10 mL, 25 mL, 100 mL, 250 mL, 500 mL, and 1 L.

Using Pipettes

• “Never mouth pipette!”

• Instead, you must use one of a number of pipetting devices available (pipet fillers).

Using Micropipettes• Measuring units smaller than 1mL requires a micropipette.

A micropipette has four parts• Plunger button• Ejector button• Volume display• Dispensing tip

Picking and Using the Appropriate Micropipette

• P-100 or P-200 micropipette

• P-10 or P-20 micropipette• P-1000 micropipette

The plunger has two “stops.”

Pressing to the first stop evacuates air to the volume in the display.

Pressing to the second stop evacuates that volume plus another 50% or so.

P-10 micropipettes are common in biotechnology labs.

A P-10 micropipette will measure volumes as small as 0.5 mL and has precision to 0.02 mL.

P-100 Micropipette.

This micropipette will measure volumes as small as 10 mL and has precision to 0.2 mL.

1 mL = 0.001L

1000mL = 1L

1μL = 0.001mL

1000μL = 1mL

1,000,000μL = 1L

Using a micropipette:P1000

0 x 1000 = 0 3 x 100 = 300+ 5 x 10 = 50

thousands of µL

hundreds

tens

Volume = 350µL

Using a micropipette:P200

Volume = 95µL

hundreds of µL

tens

ones

0 x 100 = 0 9 x 10 = 90+ 5 x 1 = 5

Using a micropipette:P20

Volume = 2.5µL

tens of µL

ones

tenths

0 x 10 = 0 2 x 1 = 2+ 5 x 0.1= 0.5

Using a micropipette:P2

Volume = 0.5µL

ones of µL

tenths

hundredths

0 x 1 = 0 5 x 0.1 = 0.5+ 0 x 0.01= 0

Your Turn

Answers

The p20 is used for volumes between 2 μL and 20 μL.

Attempting to set the volume beyond the pipette’s minimum or maximum values can

damage it.

The p200 is used for volumes between 20 μL and 200 μL

Attempting to set the volume beyond the pipette’s minimum or maximum values can

damage it.

The p1000 is used for volumes between 200μL and 1000 μL

Attempting to set the volume beyond the pipette’s minimum or maximum values can

damage it.

See how the dial is set to 153?P20The volume = 15.3 μL

1 x 10 = 10 5 x 1 = 5 + 3 x 0.1= 0.3

See how the dial is set to 097?

P200Volume = 97 μL.

0 x 100 = 0 9 x 10 = 90 + 7 x 1 = 7

One useful way to convert units is to use the metric "staircase"

• Concentration is measured in several ways:•Mass/volume•Volume/volume•% mass/volume•Molarity•Normality

Solutions of Given Mass/Volume Concentrations

Mass/Volume Solution. Solvent is added until a volume of 10 mL is reached.

The protein solution has a concentration of 1 mg/mL and it is considered fairly concentrated.

Concentration in Mass/Volume Units

____ g/mL X ____ mL = ____ g of solutionconcentration volume to be weighed out,

desired desired dissolved in the solvent

A percentage represents something that is part of 100.

Concentration % Mass/Volume Equation____ % = _______

percent value decimal value of the g/mL

____ X ____ = ____ g of solute todecimal total volume be measured andvalue desired (mL) added to the volume desired of solvent

Molarity Concentration Equation

volume molarity molecular the number of grams to bewanted (L) X desired X weight of the = dissolved in solvent, up to

(mol/L) solute (g/mol) the total volume of solution desired

Periodic Table. The Period Table of Elements shows the elements (atoms) found in compounds (molecules). Each element is listed along with the atomic weight (mass) of each atom in the element. A NaCl molecule has a molecular weight of about 58.4 atu (atomic mass units) because the Na atom weighs about 23 amu, and the Cl atom weighs about 35.4 amu. Together, in the NaCl molecule, the atoms total approximately 58.4 amu. The mass of a hydrogen atom equals 1 amu.

Dilutes of Concentrated Solutions

Concentrating 1 L Solution.

Concentrated solutions can be prepared initially with a greater amount of solute to solvent, or a solution can be concentrated by removing water.

A diluted solution can be prepared by adding solvent to the solution.

Diluting a 100 mg/mL Stock Solution to 1 mg/mL.