Transcript BITC 1402

BITC 1402
General, Organic and Biochemistry or
GOC, Chapters 3, 4, 5
Review of General Chem 1
Laboratory Methods or LM, 24, 14, 15
Chapter 3
What is the octet rule?
Define electronegativity
Compare and contrast ionic and covalent
bonding, which is stronger etc.
Compare and contrast nonpolar and polar
covalent bonding
What is a Lewis structure and what does it
show for a molecule?
Compare and contrast Lewis structure and
VSEPR models
What is a dipole?
How are binary molecular compounds
named?
Chapter 4
Be able to calculate formula, molecular
weights
Be able to write chemical equations including
a net ionic equation
Be able to determine limiting reagent, percent
yield
Be able to determine spectator ions
Be able to determine what is oxidized and
what is reduced in a redox rxn
Define heat of reaction, exothermic and
endothermic, and heat of combustion
Chapter 5
Define intermolecular forces of attraction and
be able to list them in order of increasing
strength
Define surface tension, vapor pressure,
boiling point, melting point, and crystallization
Define phase, phase change, sublimation,
heat of fusion, heat of vaporization, triple
point, and a phase diagram
Chapter 7
pg 201
Le Chatelier’s Principle:
If an external stress is applied
to a system in equilibrium, the
system reacts in such a way
as to partially relieve that
stress
Activities Chapters 3, 4, and 5
Ch3: 53, 58, 69, 72, 77, 102, 105
Ch4: 29, 41, 46, 50, 53, 73, 90, 92
Ch5: 51, 56, 57, 88
LM: Chapter 24
Contaminants of water (table 24.1)
Dissolved inorganics
Dissolved organics
Suspended particles
Dissolved gases
Microorganisms
Pyrogens/endotoxins
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Measure total organic carbon (TOC)
Measure total solids (TS)
Types of Water (Table 24.3)
I (highest purity) used for analytical
procedures, tissue culture, some HPLC,
electrophoresis buffers, immunology assays
II suitable for microbiology procedures
III used for initial glassware rinses
Biologically pure- tissue culture
Organically pure- HPLC, GC/MS
WFI- water for injection
Methods of Water Purification
Review table 24.4
What method(s) will remove pyrogens, dissolved
ionized gases?
Distillation
Ion Exchange
Deionization (remove all ionic contaminants)
Carbon Adsorption –remove dissolved organic
compounds
Filtration
 Depth
 Microfiltration
 Ultrafiltration
 Reverse osmosis
Other Methods
UV oxidation – removes organic
contaminants and may kill bacteria
Ozone – kills bacteria
Systems in the Lab
RO
Deionization  distillation
What type(s) of water are possible and
how do we determine what type(s) of
water are being produced?
Handling of Reagent Water
Highly purified water is an extremely
aggressive solvent
Readily leach contaminants from any
vessel and will also dissolve carbon
dioxide from the air (Is this why the pH
value continually changed?)
 Type 1 cannot be stored for any length of
time –Type II can be stored for short
periods of time
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Monitoring
Resistivity – The theoretical max ionic
purity for water is 18.3 megohm-cm and
17 is acceptable
Bacterial counts
Pyrogens
Organic carbon (potassium
permanganate)
Maintenance
Distilled water: frequent cleaning
prepared daily
Ion exchange/ deionization: regenerated
and sanitized
Filters: tested, flushed and sanitized
Activated carbon: washed/ recharged
UV: replaced annually
DOCUMENTATION
Characteristics & Cleaning of
Glass and Plastic Labware
Review tables 24.5 and 24.6
Cleaning
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Prerinse
Contaminant removal (review table 24.7)
Rinse
Final rinse
Drying
(I used chromic acid to clean pipettes in
graduate school—why is this a problematic
process in today’s lab?)
Sterilization and Storage of
Solutions
Review Tables 24.9 and 24.10
Activity: problem 1 and 3
Chapter 14: Introduction to
Instrumental Methods and Electricity
Mechanical measurement instrument
has these components: Interface 
Transducer (Sensor)  Signal
Processor  Display (Readout)
Identify these components in a balance
Certain Requirements Must be Met:
The instrument’s response must have a
consistent and predictable relationship with
the property being measured
The instrument’s response must be related to
internationally accepted units of
measurement
Calibration is the process by which the
response of an instrument is related to
internationally accepted measurement units
Calibration of Common
Bioinstrumentation
pH meter
Balance
Centrifuge
(How is calibration different from
validation?)
Basic Terminology and
Concepts of Electricity
Define the following:
Current
 Amperes or amps (6.25 x 1018
electrons/sec = 1amp)
 DC (delivered by batteries)
 AC (USA- frequency is 60 times/sec) 1
Hz=1cycle/sec (why is AC delivered by
power companies and NOT DC?)
 Rectification- change AC to DC
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Voltage
What is the definition of energy?
Potential energy?
Electrical potential is also called
electromotive force (EMF) or voltage
(V).
The voltage supplied by the power
company is either in the range of 110 to
120 or 220.
Resistance
Impedance to electron flow
The units are ohms (1 ohm is the value
of resistance through which 1 V
maintains a current of 1 A)
What is a conductor? What is a
semiconductor? An insulator?
Ohm’s Law
V=IR
Application of Ohm’s Law
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Gel electrophoresis: The sample mixture is placed
in a gel matrix. The gel is placed in a box, buffer is
poured over it, and a current (I) is applied. The
positive and negative ions in the gel and the buffer
conduct the current. A power supply provides the
voltage (V), source of the I. The gel provides R,
which increases with time as the ions are run out
of the gel. Therefore, to maintain I, V must be
increased BUT this also increases the heat in the
gel-thus, it is better to maintain constant V instead
of constant I TO prevent excessive heating of the
gel.
Power, Work, and Circuits
Power = voltage x current or
W = (V)(I)
A good equation to know if you’re trying
to figure out how many instruments you
can run in a lab at one time
Equipment in the Laboratory
Power supplies convert AC to DC
Transducers or detectors generate an
electrical signal in response to a
physical or chemical property of a
sample (review table 14.1)
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Detection limit, sensitivity or range of the
equipment is the minimum level of the
material or property of interest that causes
a detectable signal
Electrical noise is an important factor in
determining range
Noise
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Short-term is defined as random, rapid “spikes”
Long-term or drift is a relatively long-term increase
or decrease in readings due to changes in the
instrument
Expressed as signal-to-noise ratio: the higher the
ratio, the better the performance (root mean
square noise- RMS)
The detection limit of a detector is therefore often
defined in practice as the minimum level of sample
that generates a signal at least twice the average
noise level
The dynamic range of a detector is the range of
sample concentrations that can be accurately
measured by the detector
Signal Processing Units
Amplifier boosts the voltage or current
from a detector in proportion to the size
of the original signal
Gain is the degree to which a signal can
be increased or decreased
For example, if input is 1 mV and the
output is 100 mV then Gain =
100/1=100
Attenuator reduces a signal in order to best
display it by a readout device
Readout devices
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Meters, strip chart recorders, computer screens
Quality and Safety Issues
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Preventive maintenance
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Performance verification
Instrument validation
Environmental Factors that Affect the
Performance of Instruments (table 14.4)
Electrical Safety (table 14.5)
Problems: 1, 2, 8
BITC 1402
The Measurement of Weight
Chapter 15
Chapter 15: Weight
The force of gravity on an object
Balances are instruments used to measure
this force
Mass
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The amount of matter in an object expressed in
units of grams
Why are these instruments named balances?
How is a mechanical balance different from an
electronic balance?
Which one would you use to balance tubes for
centrifugation?
Characteristics and Types of
Balances
Range (highest to lowest)
Capacity (the heaviest sample that can be
weighed)
Sensitivity (or readability)- the smallest value
of weight that will cause a change in the
response of the balance (determines the no.
of places right of the decimal point)
Which is more sensitive, an analytical
balance or a pan balance?
(review figure 15.4)
How about the balances in the lab?
How Does an Electronic
Balance Work?
The weighing pan is depressed by a small
amount when an object is placed on it.
The balance has a detector that senses the
depression of the pan
An electromagnetic force is generated to
restore the pan to its original (“null”) position.
This force is measured as an electrical signal
that is in turn converted to a digital display of
weight value (i.e. the balance compares the
electrical signal of the unknown sample to the
signal of standard(s) of known weight)
General Procedure for Weighing a
Sample with an Electronic Analytical
Balance
Make sure the balance is level
Adjust the balance to zero (the pan should be
clean and doors shut to avoid air currents)
Tare the weighing container or weigh the
empty container
Place the sample on the weighing pan & read
the value for the measurement
Remove the sample; clean the balance and
area around it (I will fail you if you do not!)
Factors That Affect the Quality
of Weight Measurements
Temperature (samples are heavier when they
are cold)
“Warming up” period for the balance?
Static charge (ionizing blower, antistatic
brush)
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Ground yourself (hold the sample on the spatula
and touch the balance)
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Review table 15.1
Calibration and Maintenance
of a Balance
Must be checked periodically
Must be checked when a balance is
moved
For microbalances (5 places pass the
decimal to the right), they must be
calibrated when the weather changes!
Mechanical Balance
Must be calibrated by a trained
technician (ASTM Standard E 319-85)
Electronic Balance: Two-point
Calibration
The balance is set to zero using the appropriate
knob, when the weighing pan is clean and empty
The first weight is added and the balance is set to the
value of the standard
The second weight (usually heavier than the first) is
added and the balance is set to the value of the
standard
A quick check is to add exactly 1mL of water to a
tared weigh boat-it should weigh exactly 1g (of
course your micropipettor needs to be measuring
exactly 1 mL)
Standards
Purchased with a certificate showing their traceability
to NIST
The appropriate weights for a balance have been
established by ASTM Standard E 617
There are different classes: 1, 2, 3 and 4 with 1 being
the most rigorous (4 is recommended for student
use)
Handle with tongs because they are damaged by skin
oils and by cleaners that remove such oils
(Keep two sets: one for use and one for storage;
every 6 months measure the one for use against the
one for storage
Review the Appendix
Quality Programs and
Balances
Laboratories that meet the requirements
of a quality system, such as ISO 9000
or cGMP, have procedures that detail
how to operate each balance and how
to maintain, calibrate, and check their
performance.
Verifying Balance Accuracy,
Precision, and Linearity
Accuracy is tested by weighing one or more
mass standards
Precision is measured by weighing a sample
multiple times and calculating the standard
deviation
Linearity is tested by weighing subsets of
weights and comparing the sum of the
subsets to the weight of the objects all
together
Checking the Linearity of a
Balance
Select 4 items whose weight is about the
capacity of the balance and label them A, B,
C, D
Weigh all 4 items separately and added up
the values
Weigh all 4 items together and compare that
value to the summed value
Do this for a low weight (25%), the midpoint
weight (50%) and for a weight close to
capacity of the balance (75%)
Writing SOPs for the Use of
Balances
Examples are found on page 292
Mass versus Weight
The major force measured in weighing is the
force of gravity. However there is also a slight
buoyant force from air. Therefore objects
weighed in a vacuum are heavier than
weighed in air. This is the priniciple of
buoyancy.
(Note 1 g of metal weighs differently than 1 g
of water)
The discrepancy between mass and weight is
called the buoyancy error-usually this error is
ignored!
Exercises: 4, 5, 6