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 3What is the octet rule?Define electronegativityCompare and contrast ionic and covalent bonding, which is stronger etc.Compare and contrast nonpolar and polar covalent bondingWhat is a Lewis structure and what does it show for a molecule?Compare and contrast Lewis structure and VSEPR modelsWhat is a dipole?How are binary molecular compounds named?

Chapter 4Be able to calculate formula, molecular weightsBe able to write chemical equations including a net ionic equationBe able to determine limiting reagent, percent yieldBe able to determine spectator ionsBe able to determine what is oxidized and what is reduced in a redox rxnDefine 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 7pg 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 inorganicsDissolved organicsSuspended particlesDissolved gasesMicroorganismsPyrogens/endotoxins 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 PurificationReview table 24.4What method(s) will remove pyrogens, dissolved ionized gases?DistillationIon ExchangeDeionization (remove all ionic contaminants)Carbon Adsorption –remove dissolved organic compoundsFiltration 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 solventReadily 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

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 sanitizedFilters: tested, flushed and sanitizedActivated carbon: washed/ rechargedUV: replaced annuallyDOCUMENTATION

Characteristics & Cleaning of Glass and Plastic Labware

Review tables 24.5 and 24.6Cleaning 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:CurrentAmperes 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

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 LawV=IRApplication of Ohm’s Law 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 DCTransducers or detectors generate an electrical signal in response to a physical or chemical property of a sample (review table 14.1)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 rangeNoise 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 signalGain is the degree to which a signal can be increased or decreasedFor 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 deviceReadout devices Meters, strip chart recorders, computer screens

Quality and Safety Issues Preventive maintenance

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 1402The Measurement of Weight

Chapter 15

Chapter 15: Weight

The force of gravity on an objectBalances are instruments used to measure this forceMass 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 panAn 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

BalanceMake sure the balance is levelAdjust the balance to zero (the pan should be clean and doors shut to avoid air currents)Tare the weighing container or weigh the empty containerPlace the sample on the weighing pan & read the value for the measurementRemove 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) Ground yourself (hold the sample on the spatula

and touch the balance)

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 emptyThe first weight is added and the balance is set to the value of the standardThe second weight (usually heavier than the first) is added and the balance is set to the value of the standardA 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)

StandardsPurchased with a certificate showing their traceability to NIST The appropriate weights for a balance have been established by ASTM Standard E 617There 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 storageReview 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, DWeigh all 4 items separately and added up the valuesWeigh all 4 items together and compare that value to the summed valueDo 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 WeightThe 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