ANALYTICAL CHEMISTRY

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ANALYTICAL CHEMISTRY CHEM 421/821, Spring
2009 MWF 1130-1220, Rm 130 Hamilton
Hall COURSE OUTLINE Instructor Dr. Robert
Powers Office Labs Add
ress 722 HaH 720 HaH Phone
472-3039 472-5316 e-mailrpowers3_at_unl.edu web
page http//bionmr-c1.unl.edu/ Office Hours
1030-1130 am MWF or by Special
Appointment. Required Items (i) Chem 482
484 are prerequisites (ii) Text Principals of
Instrument Analysis, 6/e D. A. Skoog, J. F.
Holler and S R. Crouch Thomson, New
York (iii) Calculator for exams (TI-89 style or a
simpler model) Text Principals of Instrument
Analysis, 6/e by D. A. Skoog, J. F. Holler and
S. R. Crouch Thomson, New York
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Course Outlined (cont.)
Course Work Exam 1 100 pts (Mon., Feb.
9) Exam 2 100 pts (Fri., Mar. 6) Exam
3 100 pts (Mon, Apr. 13) Final 200 pts (10
am Wed., May 6) Written Report 50 pts (Fri.,
Apr. 17) Problem Sets 150 pts (various due
dates) Total 700 pts
Answer keys for the problem sets and exams will
be posted on BlackBoard, on the bulletin board
next to Room 722 Hamilton Hall and on the web
(http//bionmr-c1.unl.edu/). If removed for
photocopying, these keys must be returned to the
bulletin board immediately after use.
Grading scale A95 A90 A-85 B80
B75 B-70
C65 C60 C-55 D50 D-45 F40
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PAPER ON INSTRUMENTAL METHODS

• Paper General
• 4-5 pages single space text
• Additional pages for figures, references
• 12 pitch font
• Double spacing between paragraphs and headings
• Paper Topic
• Instrumental method
• Principals behind technique
• How the technique is used
• Kind of instrumentation
• What samples are used
• Advantages/disadvantages

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PAPER ON INSTRUMENTAL METHODS

• Application of instrumental method
• Brief review of the properties of sample of
  interest
• How these properties are used to analyze sample
• What types of techniques are available
• Advantages/disadvantages
• Source of ideas
• Journals Analytical Chemistry, Trends in
  Analytical Chemistry(TrACs), CE News, Science,
  Nature
• Grading (50 points total)
• Content
• Clarity of Presentation
• Comprehension of material
• Paper topic needs to be approved by Monday, March
  9th
• Due Date 1130 am, Monday April 17th

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Lecture Topics Date Chapter
Topic
I. Introduction to
Analytical Chemistry Jan 12 Chap
1 Introduction II. Spectroscopic
Methods Jan 14 Chap 6 Introduction to
Spectroscopy Jan 16 Chap 6 Jan 21 Chap
7 Instrumentation for Spectroscopy Jan
23 Chap 7 Jan 26 Problem Set 1 due Jan
28 Chap 13-14 UV/Visible Molecular Absorption
Spectroscopy Jan 30 Chap 13-14 Feb 2 Chap
13-14 Feb 4 Chap 15 Molecular Luminescence
Spectroscopy Feb 6 Problem Set 2 due Feb
9 EXAM 1 Feb 11 Chap 16-17 Infrared
Spectroscopy Feb 13 Chap 16-17 Feb
16 Chap 18-19 Raman Spectroscopy Feb
18 Problem Set 3 due Feb 20 Chap
8-10 Atomic Spectroscopy Feb 23 Problem
Set 4 due Feb 25 Chap 26 Introduction to
Chromatography III. Separation Methods Feb
27 Chap 27 Gas Chromatography Mar 2 Chap
27 Mar 4 Problem Set 5 due Mar 6 EXAM 2
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Lecture Topics Date Chapter
Topic Mar 9 Chap 28 Liquid
Chromatography/Paper Topic Approvals Mar 11 Chap
28 Mar 13 Chap 29-30 Other Separation
Methods March 16-20 Spring Break Mar
23 Problem Set 6 due   IV. Electrochemical
Methods Mar 25 Chap 22 Introduction to
Electrochemistry Mar 27 Chap 22 Mar
30 Chap 22 Apr 1 Chap 23 Potentiometry Apr
3 Chap 23 Apr 6 Chap 24 Coulometry Apr
8 Chap 25 Voltammetry Apr 10 Problem Set 7
due Apr 13 EXAM 3   V. Other Techniques Apr
15 Chap 19 NMR Apr 17 Chap 19 Instrumental
Methods Paper Due Apr 20 Chap 19 Apr 22 Chap
19 Apr 24 Chap 11,20 Mass Spectrometry Apr
27 Chap 11,20 Apr 29 Problem Set 8 due May
1 Review Session May 6 FINAL EXAM


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Introduction to Analytical Chemistry
Background A.) ANALYTICAL CHEMISTRY The Science
of Chemical Measurements. B.) ANALYTE The
compound or chemical species to be measured,
separated or studied C.) TYPES of ANALYTICAL
METHODS 1.) Classical Methods (Earliest
Techniques) a.) Separations precipitation,
extraction, distillation b.) Qualitative
boiling points, melting points, refractive index,
color, odor, solubilities c.)
Quantitative titrations, gravimetric
analysis 2.) Instrumental Methods
(post-1930s) a.) separations chromatography,
electrophoresis, etc. b.) Qualitative or
Quantitative spectroscopy, electrochemical
methods, mass spectrometry, NMR,
radiochemical methods, etc.
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CHOOSING AN ANALYTICAL METHOD
What Factors to Consider What type of
information does the method provide? What are
the advantages or disadvantages of the technique
versus other methods? How reproducible and
accurate is the technique? How much or how
little sample is required? How much or how
little analyte can be detected? What types of
samples can the method be used with? Will other
components of the sample cause interference? Othe
r factors speed, convenience, cost,
availability, skill required. How Do We Answer
or Address These Questions?
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CHARACTERISTICS OF AN ANALYTICAL METHODS
Accuracy The degree to which an experimental
result approaches the true or accepted
answer. Ways to Describe Accuracy Error An
experimental measure of accuracy. The difference
between the result obtained by a method and the
true or accepted value. Absolute Error (X
m) Relative Error () 100(X
m)/m where X The experimental result m
The true result All Methods, except counting,
contain errors dont know true value Two
types of error random or systematic
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CHARACTERISTICS OF AN ANALYTICAL METHODS
Random Error results in a scatter of results
centered on the true value for repeated
measurements on a single sample. Systematic
Error results in all measurements exhibiting a
definite difference from the true value
Random Error
Systematic Error
plot of the number of occurrences or population
of each measurement (Gaussian curve)
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CHARACTERISTICS OF AN ANALYTICAL METHODS
Precision The reproducibility of results. The
degree to which an experimental result varies
from one determination to the next.
Precision is related to random error and
Accuracy is related to systematic error.
Illustrating the difference between accuracy
and precision
Low accuracy, high precision
Low accuracy, low precision
High accuracy, low precision
High accuracy, high precision
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CHARACTERISTICS OF AN ANALYTICAL METHODS
Ways to Describe Precision Range the high to
low values measured in a repeat series of
experiments. Standard Deviation describes the
distribution of the measured results about
the mean or average value. Absolute Standard
Deviation (SD) Relative Standard
Deviation (RSD) or Coefficient of Variation
(CV) where n total number of
measurements Xi measurement made
for the ith trial mean result
for the data sample
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CHARACTERISTICS OF AN ANALYTICAL METHODS
Response The way in which the result or signal
of a method varies with the amount of compound
or property being measured. Ways to Describe
Response Calibration Curve A plot of the
result or signal vs. the known amount of a known
compound or property (standard) being
measured.
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CHARACTERISTICS OF AN ANALYTICAL METHODS
Parameters used to Describe a Calibration Curve
S mc Sbl S measured signal c
analyte concentration Sbl instrument signal
for blank Sensitivity calibration sensitivity
slope (m) of calibration curve. analytical
sensitivity (g) slope (m)/standard deviation
(Ss) ability to discriminate between small
differences in analyte concentration. Slope
and reproducibility of the calibration curve.

Method A
Method B
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Selectivity degree to which the method is free
from interference by other species in the
sample
No method is totally free from interference from
other species. Selectivity coefficient
(k) kB,A mB/mA Relative slopes of
calibration curves indicate selectivity S
mA(cA kB,Acb) Sbl
Species A
Species B
Interested in detecting species A, but signal
will be a combination of signal from the presence
of species A and species B.
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Limits of Detection (cm ) (minimum analyte
signal (Sm) - mean blank signal(
))/slope(m) minimum/maximum concentration or
mass of analyte that can be detected at a
known confidence level. Signal-to-noise
Ratio (S/N) Noise random variation in signal
or background Signal net response recorded by
a method for a sample (Note a value of S/N
2 or better is considered to be the minimum ratio
needed for the reliable detection of a true
signal from a sample.)

• Estimate S/N
• Multiple determination of blank samples.
• Estimation of best-fit to calibration curves

signal
noise
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Dynamic Range linear region of calibration
curve where the lower limit is ten times the
standard deviation of the blank. LOQ - limit of
quantitation LOL - limit of linearity
Concentration (mM)
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Example 1 The data in the table below were
obtained during a colorimetric determination of
glucose in blood serum. A serum
sample gave an absorbance of 0.350. Find the
glucose concentration and its standard deviation,
calibration sensitivity, detection limit and
dynamic range.