FOOD CHEMISTRYPractical-Demo
BY
DR BOOMINATHAN Ph.D.
M.Sc.,(Med. Bio, JIPMER), M.Sc.,(FGS, Israel), Ph.D (NUS, SINGAPORE), PDF (USA)
PONDICHERRY UNIVERSITY
I lecture
6/7August/2012
Source: Collected from different sources on the internet and presented by Dr L. Boominathan
PREPARING LABORATORY
SOLUTIONS AND REAGENTS
I THE BASICS
TOPICS
• Where do solution recipes come from?
• Concentration of solute: calculations
• Preparing solutions
– Making diluted solutions from concentrated ones
– Buffers
– Bringing solutions to proper pH
• Calculations for solutions with more than one
solute, next lecture
WHERE DO SOLUTION "RECIPES"
COME FROM?
•
Original Scientific Literature
•
Lab manuals (instructional)
•
Lab Manuals (professional)
•
Handbooks
•
Manufacturers and suppliers
INTERPRETING RECIPES
DEFINITIONS:
• SOLUTES -- substances that are
dissolved
• SOLVENTS -- substance in which solutes
are
dissolved (usually water)
• AMOUNT -- how much
CONCENTRATION versus
AMOUNT
• CONCENTRATION -- amount / volume
• Fraction where:
– Numerator, the amount of solute
– Denominator, usually volume of entire solution
• solvent + solute(s)
Each star represents 1 mg of NaCl.
What is the total amount of NaCl in the tube? _____
What is the concentration of NaCl in the tube (in mg/mL)? _____
Each star represents 1 mg of NaCl.
What is the total amount of NaCl in the tube?
4 mg
What is the concentration of NaCl in the tube (in mg/mL)?
4 mg = ?_
5 mL
1 mL
? = 0.8 mg, so the concentration is 0.8 mg/mL
WAYS TO EXPRESS CONCENTRATION
OF SOLUTE
• Source of confusion: more than one
way to express concentration of
solute in a solution
CONCENTRATION EXPRESSIONS
1. WEIGHT PER VOLUME
2. MOLARITY
3.
PERCENTS
a. Weight per Volume %
(w/v %)
b. Volume per Volume %
(v/v %)
c. Weight per Weight %
(w/w %)
MORE CONCENTATION EXPRESSIONS
4. PARTS
Amounts of solutes as "parts"
a. Parts per Million (ppm)
b. Parts per Billion (ppb)
c. Might see ppt
d. Percents are same category (pph %)
STILL MORE CONCENTRATION
EXPRESSIONS
TYPES NOT COMMON IN BIOLOGY
MANUALS:
5. MOLALITY
6. NORMALITY
•
for NaOH and HCl, molarity = normality, however,
this is not always true for all solutes
WEIGHT / VOLUME
• Means a fraction with:
weight of solute in numerator
total volume in denominator
EXAMPLE:
• 2 mg/mL proteinase K
– 2 mg of proteinase K in each mL of solution.
• How much proteinase K is required to
make 50 mL of
solution at a
concentration of 2 mg/mL?
PROPORTION PROBLEM
2 mg proteinase K
1 mL solution
=
X
50 mL solution
X = 100 mg
= amount proteinase K needed.
MOLARITY
• Molarity is: number of moles of a solute
that are dissolved per liter of total solution.
• A 1 M solution contains 1 mole of
solute per liter total volume.
MOLE
• How much is a mole?
From Basic Laboratory Methods for Biotechnology: Textbook and Laboratory Reference, Seidman and
Moore, 2000
EXAMPLE: SULFURIC ACID
For a particular compound, add the atomic weights
of the atoms that compose the compound.
H2SO4:
2 hydrogen atoms 2 X 1.00 g = 2.00 g
1 sulfur atom
1 X 32.06 g = 32.06 g
4 oxygen atoms 4 X 16.00 g = 64.00 g
98.06 g
EXAMPLE CONTINUED
• A 1M solution of sulfuric acid contains 98.06
g of sulfuric acid in 1 liter of total solution.
• "mole" is an expression of amount
• "molarity" is an expression of concentration.
DEFINITIONS
• "Millimolar", mM, millimole/L.
– A millimole is 1/1000 of a mole.
• "Micromolar", µM, µmole/L.
– A µmole is 1/1,000,000 of a mole.
FORMULA
HOW MUCH SOLUTE IS NEEDED FOR A SOLUTION OF
A PARTICULAR MOLARITY AND VOLUME?
(g solute ) X (mole) X (L) = g solute needed
1 mole
L
or
FW
X molarity
x volume = g solute needed
EXAMPLE
How much solute is required to make 300
mL of 0.8 M CaCl2?
ANSWER
mole
(111.0 g) (0.8 mole) (0.3 L) = 26.64 g
L
From Basic Laboratory Methods for Biotechnology: Textbook and Laboratory Reference, Seidman and Moore,
2000
TO MAKE SOLUTION OF GIVEN
MOLARITY AND VOLUME
1. Find the FW of the solute, usually from label.
2. Determine the molarity desired.
3. Determine the volume desired.
4. Determine how much solute is necessary by
using the formula.
PROCEDURE CONT.
5. Weigh out the amount of solute.
6. Dissolve the solute in less than the desired final
volume of solvent.
7. Place the solution in a volumetric flask or
graduated cylinder. Add solvent until exactly the
required volume is reached, Bring To Volume,
BTV.
PERCENTS
X % is a fraction
numerator is X
denominator is 100
Three variations on this theme.
WEIGHT/VOLUME
TYPE I:
Grams of solute
100 mL total solution
Most common in biology.
%
EXAMPLE
20 g of NaCl in
100 mL of total solution
= 20% (w/v) solution.
EXAMPLE: BY PROPORTIONS
How would you prepare 500 mL of a 5 %
(w/v) solution of NaCl?
ANSWER
By definition:
5 g
=
100 mL
5%= 5g
100 mL
?
500 mL
? = 25 g = amount of solute
BTV 500 mL
BY EQUATION
How would you prepare 500 mL of a 5 % (w/v)
solution of NaCl?
1. Total volume required is 500 mL.
2. 5% = 0.05
3. (0.05) (500 mL) = 25
% EXAMPLE CONTINUED
4. 25 is the amount of solute required in
grams.
5. Weigh out 25 g of NaCl. Dissolve it in
less than 500 mL of water.
6. In a graduated cylinder or volumetric
flask, bring the solution to 500 mL.
From Basic Laboratory Methods for Biotechnology: Textbook and Laboratory Reference, Seidman and
Moore, 2000
TWO OTHER FORMS OF %
v/v
mL solute
100 mL solution
w/w
g solute
100 g solution
WEIGHT/WEIGHT
• How would you make 500 g of a 5%
solution of NaCl by weight (w/w)?
ANSWER
1.
2.
Percent strength is 5% w/w, total weight desired is
500g.
5% = 5g/100g
3.
5g X 500 g = 25 g
4.
5.
100 g
500 g – 25 g = 475 g = amount of solvent needed
Dissolve 25 g of NaCl in 475 g of water.
= NaCl needed
PARTS
Parts may have any units but must be
the same for all components of the
mixture.
EXAMPLE:
A solution is 3:2:1 ethylene:chloroform:isoamyl
alcohol
Might combine:
3 liters ethylene
2 liters chloroform
1 liter isoamyl alcohol
PPM AND PPB
• ppm: The number of parts of solute per 1
million parts of total solution.
• ppb: The number of parts of solute per
billion parts of solution.
PPM EXAMPLE:
5 ppm chlorine = 5 g of chlorine in 1 million g
of
solution,
or 5 mg chlorine in 1 million mg of solution,
or 5 pounds of chlorine in
1 million pounds of solution
CONVERSIONS
To convert ppm or ppb to simple weight per
volume expressions:
5 ppm chlorine = 5 g chlorine =
106 g water
5 g chlorine
106 mL water
= 5 mg/1 L water
= 5 X 10-6 g chlorine/ 1 mL water
= 5 micrograms/mL
PPM TO MICROGRAMS/mL
For any solute:
1 ppm in water = 1 microgram
mL
Each star represents 1 mg of dioxin.
What is the concentration of dioxin in tube expressed as ppm (parts per
million)? ____________
What is the total amount of dioxin in beaker? ___________
Each star represents 1 mg of dioxin.
What is the total amount of dioxin in tube? 25 mg
What is the concentration of dioxin in tube expressed as ppm?
____________
1 ppm in water = 1 μg
mL
25 mg/500 mL = 0.05 mg/mL = 50 μg/mL
so the concentration is 50 ppm
A COMPARISON OF METHODS OF EXPRESSING THE CONCENTRATION OF A
SOLUTE
CONCENTRATION OF SOLUTE
(Na2
2SO4
4)
AMOUNT OF SOLUTE
AMOUNT OF WATER
1M
142.04 g Na2SO4
BTV 1 L with water
1m
142.04 g Na2SO4
Add 1.00 kg of water
1 N
71.02 g Na2SO4
BTV 1 L with water
1 %
10 g Na 2SO4
BTV 1 L with water
1 ppm
1 mg
BTV 1 L
PREPARATION OF SOLUTIONS
• Preparing Dilute Solutions from
Concentrated Ones (C1V1=C2V2)
• Biological Buffers
• Preparing Solutions with More Than
One Solute
• Assuring the Quality of a Solution
PREPARING DILUTE SOLUTIONS FROM
CONCENTRATED ONES
• Concentrated solution = stock solution
• Use this equation to decide how much
stock solution you will need:
C1V1=C2V2
C1 = concentration of stock solution
C2 = concentration you want your dilute solution
to be
V1 = how much stock solution you will need
V2 = how much of the dilute solution you want to
make
EXAMPLE
• How would you prepare 1000 mL of a 1 M
solution of Tris buffer from a 3 M stock of
Tris buffer?
– The concentrated solution is 3 M, and is C1.
– The volume of stock needed is unknown, ?, and is V1.
– The final concentration required is
1 M, and is C2.
– The final volume required is 1000 mL and is V2.
SUBSTITUTING INTO THE
EQUATION:
C1 V1 = C2 V2
3 M (?) 1 M (1000 mL)
? = 333.33 mL
So, take 333.33 mL of the concentrated
stock solution and BTV 1 L.
“X” SOLUTIONS
• The concentration of a stock solution is
sometimes written with an “X”.
• The “X” is how many more times the stock
is than normal.
• You generally want to dilute such a stock
to 1X, unless told otherwise.
EXAMPLE
• A can of frozen orange juice is labeled 4X. How
would you dilute it to make 1L of drinkable
drinkable juice?
• Using the C1V1=C2V2 equation:
C1 V1 = C2 V2
4X (?) = 1X (1L)
? = 0.25 L
Use 0.25 L of orange juice, BTV 1L.
BIOLOGICAL BUFFERS
• Laboratory buffers
solutions to help maintain a biological
system at proper pH
• pKa of a buffer
the pH at which the buffer experiences
little change in pH with addition of acids or
bases = the pH at which the buffer is most
useful
TEMPERATURE
• Some buffers change pH as their
temperature and/or concentration changes
• Tris buffer, widely used in molecular
biology, is very sensitive to temperature
DILUTION
• Some buffers are sensitive to dilution
• Phosphate buffer is sensitive to dilution
ADJUSTING THE pH of a
BUFFER
• This is done to set the buffer to a pH value
which is...
– somewhat close to its pKa
– useful for the biological system the buffer is to
be used with
• Often adjust pH using NaOH or HCl
– Not method used for phosphate buffer (see
textbook)
BRINGING A SOLUTION TO THE
PROPER pH
• Adjust the pH when the solution is at the
temperature at which you plan to use it.
• Mix the solute(s) with most, but not all, the
solvent. Do not bring the solution to volume.
• Stir solution.
• Check the pH.
• Add a small amount of acid or base.
– The recipe may specify which to use.
– If not, HCl and NaOH are commonly used.
• Stir again and then check the pH.
• Repeat until the pH is correct, but don’t
overshoot.
• Bring the solution to volume and recheck
the pH.
ASSURING THE QUALITY OF A
SOLUTION
• Documentation, labeling, recording what
was done
• Traceability
• SOPs
• Maintenance and calibration of
instruments
• Stability and expiration date recorded
• Proper storage
Solution Chemistry
It’s all about the concentration
Common units of concentration
% by mass – g solute /100 g solution
% by volume – mL solute/100 mL solution
% by mass-volume – g solute/100 mL solution
Molarity – moles solute/L solution
Molality – moles solute/kg solvent
Normality – equivalent moles of solute/L solution
ppt – grams solute/thousand grams solution
ppm –g solute/million g solution
ppb – g solute/billion g solution
lb solute/million gallons solution
Some conversion problems:
Convert 136 μg NaCl/mL pond water to lb
NaCl/million gallons pond water
.
Some conversion problems:
136 μg NaCl ….
? lb NaCl
mL pond water million gallons pond water
What do we need to know?
Some conversion problems:
136 μg NaCl ….
? lb NaCl
mL pond water million gallons pond water
What do we need to know?
•
•
How many μg in a lb?
How many mL in a million gallons?
Some conversion problems:
136 μg NaCl ….
? lb NaCl
ml pond water million gallons pond water
453.6 g = 1 pound
1 μg = 10-6 g
1 mL = 10-3 L
1.057 L = 1 quart
4 quarts = 1 gallon
Some conversion problems:
136 μg NaCl * 10-6 g * 1 lb
= 2.998x10-7 lb
mL pond water 1 μg 453.6 g mL pond water
2.998x10-7 lb * 1 mL * 1.057 L = 3.17 x10-4 lb
mL pond water 10-3 L 1 qt
qt
3.17 x10-4 lb * 4qt * 106 gal = 1.26x103 lb
qt
1 gal million gal million gal
Some conversion problems:
Convert 36% by mass of HCl to Molarity.
How do we start?
Some conversion problems:
Convert 36% by mass of HCl to Molarity.
How do we start?
Units! Units! Units!
Some conversion problems:
Convert 36% by mass of HCl solution to
Molarity.
36 g HCl ……..
100 g solution
Moles HCl
1 L solution
What do we need to know?
Some conversion problems:
Convert 36% by mass of HCl solution to Molarity.
36 g HCl ……..
100 g solution
Moles HCl
1 L solution
What do we need to know?
• Molar mass of HCl
• Density of HCl solution
Some conversion problems:
Convert 36% by mass of HCl solution to Molarity.
36 g HCl ……..
100 g solution
Moles HCl
1 L solution
What do we need to know?
• Molar mass of HCl (36.46 g/mol – from Periodic
table)
• Density of HCl solution (from where???)
Density – your critical judgment
For a solution, sometimes you know the density,
sometimes you don’t.
There are tables, but they are not all inclusive.
You might, for example, find in a table that:
Density (30% HCl) = 1.12 g/mL
Density (40% HCl) = 1.23 g/mL
Density (36% HCl) = ???
Interpolate or Assume
Density (30% HCl) = 1.12 g/mL
Density (40% HCl) = 1.23 g/mL
Density (36% HCl) = ???
You could assume that 36% is closest to 40% and use
1.23 g/mL. This is legitimate, although not 100%
accurate. Results may vary, depending on how good
the assumption is.
Interpolate or Assume
Density (30% HCl) = 1.12 g/mL Density (40% HCl) = 1.23 g/mL
Density (36% HCl) = ???
You could assume that density changes linearly with concentration (it doesn’t,
but it is pseudo-linear for small changes). In that case, you would “linearly
interpolate” the density.
1.23 g/mL – 1.12 g/mL = 0.011 g/mL = 0.011 g
40% HCl-30%HCl
%
mL%
1.12 g/mL + 0.011 g/mL% * 6% = 1.186 g/mL = 1.19 g/mL
This is legitimate, although still not 100% accurate, but probably better than
the previous assumption.
If I don’t have Density tables…
For dilute solutions, you can get pretty close by
assuming the density of the solution is the
same as the density of pure water.
For concentrated solutions (like 36%), this is
probably not a good assumption, but it is
better than nothing!
Solving the problem (finally)
Convert 36% by mass of HCl solution to Molarity.
36 g HCl ……..
100 g solution
Moles HCl
1 L solution
What do we need to know?
• Molar mass of HCl (36.46 g/mol – from Periodic
table)
• Density of HCl solution (1.19 g/mL – by assuming
linear change)
Solving the problem (finally)
36 g HCl * 1 mol * 1.19 g * 1000 mL
100 g sol 36.46 g 1 mL 1 L solution
= 11.7 mol HCl
L solution
= 11.7 M HCl
(if you don’t specify solvent, usually assumed to
be water)
Common units of concentration
% by mass – g solute /100 g solution
% by volume – mL solute/100 mL solution
% by mass-volume – g solute/100 mL solution
Molarity – moles solute/L solution
Molality – moles solute/kg solvent
Normality – equivalent moles of solute/L solution
ppt – grams solute/thousand grams solution
ppm –g solute/million g solution
ppb – g solute/billion g solution
lb solute/million gallons solution
All are important, but…
Moles! Moles! Moles!
Molarity – moles solute/L solution (most common)
Molality – moles solute/kg solvent (not very common)
Normality – equivalent moles of solute/L solution (specialized
usage)
What’s “equivalent moles”?
Normality vs. Molarity
Molarity = moles solute/L solution
- generic, just the moles folks
Normality = equivalent moles of solute/L
solution
- specific, it takes into account the actual
chemistry of the solute.
Acids
What’s an acid?
Acids
What’s an acid?
Within the Bronsted-Lowry theory of
acids/bases, an acid is a proton (H+) donor and
a base is a proton acceptor.
Can you think of examples of acids or bases?
Some acids and bases
NaOH – base
Mg(OH)2 – base
HCl – acid (hydrochloric acid)
HF – acid (hydrofluoric acid)
H2SO4 – acid (sulfuric acid)
Acid – what’s it good for?
????
Acid – what’s it good for?
Protons
If we define an acid as a proton donor, the
proton is what makes it what it is.
Consider two solutions:
1 M HCl
1 M H2SO4
How are they the same? How are they
different?
Consider two solutions:
1 M HCl
1 M H2SO4
1 mole molecules/L
1 mole molecules/L
Consider two solutions:
1 M HCl
1 M H2SO4
1 mole molecules/L
H+ Cl- in solution
1 mole molecules/L
H+ and SO42- in solution
HCl(aq) → H+(aq) + Cl-(aq)
HCl(aq) + H 2O(l)
→
H3O+(aq) + Cl-(aq)
→
H2SO4
(aq)
H2SO4
(aq) +
2 H+ (aq) + SO42-(aq)
2 H2O(l)→ 2 H3O+ (aq) + SO42-(aq)
Consider two solutions:
1 M HCl
1 M H2SO4
1 mole molecules/L
H+ Cl- in solution
1 mole molecules/L
H+ and SO42- in solution
HCl(aq) → H+(aq) + Cl-(aq)
HCl(aq) + H 2O(l)
→
H3O+(aq) + Cl-(aq)
1 mol H+/L solution
→
H2SO4
(aq)
H2SO4
(aq) +
2 H+ (aq) + SO42-(aq)
2 H2O(l)→ 2 H3O+ (aq) + SO42-(aq)
2 mol H+/L solution
Consider two solutions:
1 M HCl
1 M H2SO4
1 mole molecules/L
1 mole H+/L solution
1 mole molecules/L
2 mol H+/ L solution
They are both acids, they are defined by their ability to donate
protons. The protons are the “equivalents” for an acid.
1 N HCl
2 N H2SO4
Lab Exercise 0ne
Carbohydrate Analysis: Estimation of
Sugars
Lab
Biochemical Assay
• Biochemistry deals with the identification and
quantification of bio-molecules from a variety
of living systems
• Rely on the chemical reactivity and physical
properties of bio-molecules to make
identification and quantification.
• Primary tool is the spectrophotometer
– Uses absorption of mono chromatic light
Spectrophotometer
Measure quantity
• Some bio-molecules have properties which
allow direct measurement.
– proteins have aromatic amino acids (280nm)
– Nucleic acids have unsaturated ring structures
(260nm)
• Other molecules have chemical properties
which can be used in indirect measurement.
Introducing concept of standard curve
• Uses dilutions of a solution of known
concentration to determine concentration of
unknown
A540
m = y/x
b
(may or may
not equal 0)
0
[glucose(red)]
0
Standard Curve
• Assumes that unknown will respond in assay
the same as the known
– Valid in todays assay as they (the reactive groups.
glucose) are the same
– Problem in other assay as they may not contain
same amount of reactive groups
• Protein assays (have to choose)
• But usually close
Our model carbohydrate is the
sugar glucose
We will exploit its ability to reduce other
compounds to produce a product which
can be measured optically
Reducing Sugars
• Have aldehyde group
• Can be oxidized to
acid
• Reduces another
compound
Requirement placed on sugar
• Must be an aldehyde
– Ketones and hemiacetal configurations are not
reducing
• Conditions of reactions favor conversion to
aldehyde by lowering aldehyde concentration
Sugars as Reducing Agents
Equilibrium between
hemiacetal and open chain
is driven to open chain as
oxidation to acid form takes
place. This ensures a
quantitative conversion with
time and a stoicheometric
production of reduced
copper.
Nelson Assay (a two step Rx)
• In the Nelson assay Cu+2 is reduced to Cu+1 by the
reducing activity of the sugar (step 1)
• Cu+1 is oxidized to Cu+2 by addition of arsenomolybdic
acid (colorless) (step 2)
• Results in blue (reduced) arsenomolybdous acid
• Amount is directly related to [CU+1]
• Will detect any reducing sugar (concentration of
sugar must be limiting factor)
We will do the DNS assay
• Is a direct assay
• Measures the reducing capability of glucose
• Uses a color conversion reaction from yellow to red
brown @ A540
• Conversion of moles of DNS equals moles of glucose.
3,5-dinitrosalicylic acid (DNS)
• Sugar reduces the organic DNS which absorbs
maximally at yellow wave length
• Results in change (shift) in absorption spectrum
from red/orange to red/brown at 540nm
– Different from Nelson reaction
• Measured at 540nm
– Unreacted DNS not seen at this wavelength
– Amount of absorbance directly related to amount of
reducing sugar
The DNS reagent
From the MSDS:
– LABEL PRECAUTIONARY STATEMENTS TOXIC (USA)
HARMFUL (EU) HARMFUL BY INHALATION, IN CONTACT
WITH SKIN AND IF SWALLOWED. IRRITATING TO EYES,
RESPIRATORY SYSTEM AND SKIN. IN CASE OF CONTACT
WITH EYES, RINSE IMMEDIATELY WITH PLENTY OF WATER
AND SEEK MEDICAL ADVICE.
 3,5-dinitrosalicylic acid is reduced to 3-amino,5nitrosalicylic acid
The DNS assay
• Experimental design and flow charts
• Be sure to read “Hazards”
• Data analysis
Today's Experiment
• Measure the concentration of glucose by
detecting the reducing end of the
monosaccharide.
• This group converts the oxidized form of 3,5dinitrosalicylic acid, DNS, to reduced form
which absorbs at 540nm.
• Amount of reduced DNS proportional to
amount of glucose.
What are we doing today?
Important
• Pipetting technique is critical to accuracy and
to preventing cross contamination of samples
– Pipetters have two stops
• First to take up selected volumes
• Second to deliver
• Choose pipetter “in the range” that you need.
You will create a standard curve
• You are provided a stock solution which
contains 1.2 mg/ml
• You will dilute this stock solution in a specified
manner always producing a 4 ml solution
• You will read the absorbance of each solution
at 540 and plot vs concentration
• You will compare the A540 of unknown to
standard curve
Table A.1-2. DNS Assay Components
DNS
(ml)
Tube Number
Water Volume
(ml)
Glucose
“Standard”
Volume
(ml)
Unknown
Volume
(ml)
1
3.000
0.000
0.000
1.00
-
2
2.750
0.250
0.000
1.00
-
3
2.500
0.500
0.000
1,00
-
4
2.250
0.750
0.000
1.00
-
5
2.000
1.000
0.000
1.00
-
6
2.750
0.000
0.250
1.00
7
2.500
0.000
0.500
1.00
8
2.000
0.000
1.000
1.00
A540
Amount
(mg)
[Glucose]
(mg/ml)
Standard curve
• Uses dilutions of a solution of known
concentration to determine concentration of
unknown
A540
m = y/x
b
(may or may
not equal 0)
0
[glucose(red)]
0
Important
• Careful handling of Cuvettes is essential for
accuracy and prevent contamination
– Handle only with gloves
– Touch only the areas not in the light path
– Rinse carefully with DH2O after each use
– Always go from lowest concentration to highest
concentration.
– Wipe clear surface if necessary with “Kimwipe”
Extremely Important
•
•
•
•
Put cuvette into Spec slot that is in the beam path
Be certain that clean panes face the beam path
Measure only with the lid closed
Always set the spec with a blank (line 1 table A.1-2, page 38)
– Contains all components of reaction except that which is
to be measured
– Always use same cuvette
PLEASE DO NOT SLAM THE SPEC LIDS
Important
•
•
•
•
•
1. Wear Gloves and Safety Glasses
2. Record the code number of your unknown
3. Be certain that test tubes are clean
4. Water/H2O always means distilled water
5.Have TA initial your data before you leave.
See lab exit requirements page
Lab reports for this class
• Abstract. Statements regarding:
–
–
–
–
WHAT you are doing (-> procedure)
WHY you are doing it (-> your hypothesis)
WHAT you hope to accomplish (-> also hypothesis)
Cf. ‘purpose/goal’ in a good lab notebook! Might think of it as a very
short introduction
• Background information and theory
• Results/Data/Data Analysis
• Discussion MUST relate data analysis to hypothesis!
Application quiz
Address in your report
• What does the portable glucometers used by
diabetics measure?
• How do they measure it?
Reminder
• Lab Reports are PERSONAL
Grading for This Experiment
•
•
•
•
Number of lab periods = 1
Lab Report = points
Pre lab= points
Total = points
Clean up (Please)
before you go
• See page 44. Waste Disposal &
Clean up
• Return pipetts to rack