Analytical Chemistry Chem 215

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Analytical Chemistry Chem 215
Associate Prof. Mustafa Culha Genetics and
Bioengineering Department Room B503 Phone
216-578 1587, internal 2587 mculha_at_yeditepe.edu.t
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Course Policies
Attendance It is mandatory to attend the
lectures for a good passing grade. If you fail to
attend less then 80 of the lectures, you will
get an F in the course. Besides I urge you to
check with your department or faculty
attendance policies. In some cases those may
overrule the policy above. No make-up exams will
be scheduled. Attendance at the class is
monitored. You will be given a sign up sheet at
the beginning of each session. If you are
unable to take an exam due to an emergency or a
disaster, you must inform Me and Student Affairs
Office as soon as possible or before the
scheduled exam.
Grading Midterm Exams and Final Exam The two
one-hour exams are given during the semester and
a final (cumulative) exam at the end of the
semester. Each hour exam and the final will be
100 points. Midterm 1 15 Midterm 2
15 Quizzes and Homework 5
Final 40 Lab 25 Total 100 End
of the semester, your grade will be evaluated
against the class performance and overall success
of students taking the course in the other
sections as well. Thus, your passing score/ grade
may change or remain the same.
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Course Policies
Office Hours Monday 1000-1200 and Thursday
1400-1700 or by appointment You may also
contact me by e-mail to arrange a time to meet
other than office hours. I check my e-mail often
and we can arrange a meeting within one or two
days. In your e-mail, please briefly state the
problem and suggest a meeting time. I will get
back to you as soon as possible. Please keep in
mind that meetings take place in my office. In
some cases, we may resolve problems or questions
by exchanging e-mail only, so contact me anytime
with concerns or questions.
Academic Dishonesty You may not talk or pass
notes to each other on any subject during exams.
Possessing materials with you other than those
allowed for the work within your reach during a
test, or sharing calculators and other devices,
is assumed cheating. During tests you must keep
away any devices, which may allow you to
communicate with others or access databases. If
you are caught while cheating by any means, you
will be dismissed from the class and get an F
in the course.
Other Issues Please turn off all cell phones and
pagers while in the classroom Smoking is not
allowed in the classroom. No food or drink is
allowed in class as well.
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How to study this course?
"I'm trying to free your mind I can only show
you the door. You have to walk through it."
Morpheus speaking to Neo in the movie, Matrix.
"Can one be fully human without experiencing
tragedy? The only tragedy there is in the world
is ignorance all evil comes from that. The only
tragedy there is in the world is unwakefulness
and unawareness., Anthony DeMello, Awareness.
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How to succeed in this course!

• Attend course regularly
• Study 2 or more hours for every hour of lecture,
  i.e. minimum 6 hours a week for this course
• When you need help, do not hesitate using office
  hours (even outside of office hours)
• Do the homework problems and quizzes

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Review

• Syllabus
• Introduction

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What is Analytical Chemistry? And What does it do?

• Analytical chemistry is concerned with the
  chemical characterization of matter.
• We consider two major subsections
• Qualitative analysis
• Quantitative analysis
• Qualitative analysis is concerned with the
  detection of elements, ions or compounds present
  in a sample (i.e. what chemical species are
  present), whereas quantitative analysis deals
  with how much of one or more constituents is
  present in a sample.
• We mostly discuss quantitative analysis in
  this course.

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Analytical chemistry is the science ofmaking
quantitative measurements.

• In practice, quantifying analytes in a complex
  sample becomes an exercise in problem solving.
• To be effective and efficient, analyzing samples
  requires expertise in
• the chemistry that can occur in a sample
• analysis and sample handling methods for a wide
  variety of problems (the tools-of-the-trade)
• proper data analysis and record keeping
• To meet these needs, Analytical Chemistry courses
  usually emphasize equilibrium, spectroscopic and
  electrochemical analysis, separations, and
  statistics.

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The analytical process.

• The analytical process consists of the following
  unit operations
• Problem definition
• Obtaining a representative sample
• Preparation of a sample for analysis
• Performing necessary chemical separations
• Performing the measurement
• Calculation of results, data presentation and
  data interpretation.

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Problem definition.

• Need to translate general question into specific
  questions. Amenable to be answered by chemical
  measurement.
• What information is needed?
• What type of sample is to be analyzed?
• How sensitive must the method be?
• What degree of accuracy and precision required?
• How are interferences to be eliminated?
• These considerations will help to determine the
  specific techniques adopted.
• Other major considerations
• Skill and training of analyst.
• Facilities, equipment and instruments
  available.
• Sensitivity and precision required.
• Cost versus available budget.
• Time required for analysis versus target
  deadlines.

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Obtaining a representative sample.

• Usually only a small portion of sample is
  subjected to quantitative analysis, hence this
  laboratory sample must be representative of the
  parent sample.
• Samples may be homogeneous or heterogeneous.
• Homogeneous samples present no problem, a
  simple grab sample approach taken at random
  will suffice.
• Several samples have to be taken if parent
  sample is heterogeneous.
• Methods of sampling solids, liquids and gases
  are given in standard reference books.
• Precautions in handling and storing samples
  must be taken to minimize or prevent
  contamination, loss, decomposition or matrix
  change.
• Sample stability is an important consideration.
• Conditions under which sample is collected is
  important for biological fluids.

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Sample Preparation.

• Always determine amount (volume or weight) of
  sample being analyzed.
• Replicate samples prepared to facilitate
  subsequent statistical analysis of data.
• Solid samples must be dissolved in solution
• Inorganic materials dissolution in various
  acids, redox or complexing media
• For organic materials containing inorganic
  analytes such as trace metals, the organic matrix
  is destroyed via
• Dry ashing involves slow combustion at
  400-7000 oC, which leaves behind the inorganic
  residue which is soluble in dilute acid.
• Wet digestion heat organic with oxidizing
  acids (HNO3/H2SO4 mixture), inorganic residue
  left behind.
• Biological fluids proteins must be removed use
  methods listed above, or precipitate protein
  using specific reagents and subsequently filter
  or centrifuge to yield protein free filtrate.
• Organic analytes oxidizing methods not
  applicable. Instead extraction from sample,
  dialysis or dissolution in appropriate solvent.
  Separation step.

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Separation step.

• Separation of analyte from matrix is performed to
  
• Eliminate interferences.
• Provide suitable selectivity.
• To cause preconcentration of analyte for more
  sensitive or accurate measurement.
• Separation steps may include precipitation,
  extraction into an immiscible solvent,
  chromatography, dialysis and distillation.
• We summarize separation techniques and phase
  systems as follows
• Solvent extraction liquid/liquid liquid/solid
• Liquid (column) chromatography liquid/solid
  liquid/liquid
• Gas chromatography gas/solid gas/liquid
• Gel permeation chromatography liquid/solid
• Electrophoresis liquid/solid
• Thin layer chromatography liquid/solid
  liquid/liquid
• Paper chromatography liquid/liquid
• Ion exchange chromatography liquid/solid
• Precipitation liquid/solid

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Analytical Measurement

• The analytical measurement is often the simplest
  stage of the analytical process.
• All reagents used must be of high purity (Reagent
  grade). For trace analysis, a blank measurement
  must be performed, the results of the latter
  being subsequently subtracted from the raw
  analytical measurement.
• Analytical measurements are divided into two
  types classical (gravimetric, volumetric) and
  instrumental.
• Gravimetric analysis involves selective
  separation of analyte via precipitation followed
  by measurement of mass of precipitate.
• Volumetric analysis here the analyte reacts
  with a measured volume of reagent of known
  concentration in a process known as titration. A
  change in some physical or chemical property
  signals completion of the reaction.
• Gravimetric and titrimetric methods provide
  results accurate and precise to ca. 0.1 but
  require relatively large (mmol or mg) quantities
  of analyte.

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Method Validation.

• Instrumental methods based on measurement of a
  physical property of an analyte which may be
  directly related to concentration.
• Instrumental methods are generally more sensitive
  and selective than classical methods, but are
  less precise (accurate to ca. 1). Instrumental
  methods are rapid, may be automated, and the
  possibility exists for the determination of more
  than one analyte at a time.
• The validation of a particular analytical method
  is important. Most instrumental methods of
  analysis are relative the instrument registers
  a signal due to some physical property of the
  solution. The signal observed must be related to
  the signal recorded for a sample of known
  concentration (a validated sample) in order that
  an unknown analyte concentration be determined.

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More on Method Validation.

• It is important that an analytical method be
  subjected to rigorous validation. Equipment must
  be properly calibrated, standards should be run
  intermittently with samples.
• A control sample (a standard of known
  concentration) should be run daily and the
  results plotted as a function of time to prepare
  a quality control chart which is then compared
  with the known standard deviation of the method.
• The instrument response as a function of analyte
  concentration (a calibration curve) must be
  produced.
• Calibration is accomplished by preparing a series
  of solutions of the analyte at known
  concentrations, and measuring the instrument
  response to each of these samples, to prepare an
  analytical calibration curve of response versus
  concentration.
• The sample matrix may affect the instrument
  response to the analyte. In such cases
  calibration may be accomplished by the method of
  standard addition. Here, a portion of the sample
  is spiked with a known quantity of standard, and
  the increase in signal observed is attributed to
  the standard. Hence the standard is subjected to
  the same environment as the analyte under
  investigation.

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Classical and instrumental analytical methods.
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Data Analysis and Interpretation

• Once the concentration of the analyte in the
  sample solution has been determined, the results
  are used to calculate the amount of analyte
  present in the original sample.
• If replicate (three or more) analyses are
  performed then a precision of the analysis may be
  reported using standard statistical analysis
  (standard deviation, mean value etc).
• A knowledge of the precision is important since
  it quantifies the uncertainty in the result.
• The result should be critically evaluated to see
  if it is reasonable, and if it is related to the
  analytical problem as originally stated.
• Careful thought should be given to data
  presentation, so that it is readily digested and
  conclusions are clearly demonstrated.

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Key Terminology

• Qualitative Analysis
• Quantitative Analysis
• Analyte
• Sample (noun and verb)
• Aliquot
• Determination
• Calibration
• Homogeneous
• Heterogeneous
• Interference

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Usage Some Terms

• In order to determine trace amount of iron, I
  will use an aliquot from my tap-water sample to
  conduct a quantitative analysis.
• The sample I have was originally heterogeneous.
  By mixing, a homogeneous sample was created from
  which an aliquot was taken for analysis.
• The calibration scheme was designed to account
  for the effects of any interferences which would
  impact the analytical results.

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Units

• Derived SI Units
• Frequency (Hz, s-1)
• Pressure (Pa, N/m2)
• Charge C
• Electric Potential (V)
• Force (N)

• Fundamental SI Units
• Meters (m)
• Kilograms (kg)
• Time (s)
• Temperature (K)
• Quantity (mol)
• Electric Current (A)

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Unit Prefixes
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Dimensional Analysis (Math w/Units)

• Units in mathematical operations cancel out.
• If you have setup the problem and the units
  cancel correctly, youre right 99 of the time!
• How much lead is there in 1 liter of a 99 ppm
  lead solution (ppm ug/mL)?
• Cancel out the units just as you would with
  numerical values! I expect this is how you will
  do problems!

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Common Units

• Molarity (M) moles of analyte/L of solution
• Molality (m) moles of analyte/kg of solvent
• Weight Percent (mass percent, wt or WT) (mass
  of analyte/mass of sample)100
• Volume Percent (volume of solute/volume of
  solution) x 100

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• Parts Per Million (ppm)
• Weight based unit
• Interchangeable in aqueous solutions
• VERY COMMON in environmental work
• Since the density of water is very close to 1
  g/mL, and many aqueous solutions are primarily
  water, this approximation applies for most dilute
  aqueous solutions.

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• Parts Per Billion (ppb)
• Weight based unit
• Interchangeable in aqueous solutions
• VERY COMMON in environmental work
• Since the density of water is very close to 1
  g/mL, and many aqueous solutions are primarily
  water, this approximation applies for most
  aqueous solutions.