ANALYTICAL CHEMISTRY
CHEM 421/821, Spring 2013
MWF 11:30-12:20, Rm 130 Hamilton Hall
COURSE OUTLINE
Instructor: Dr. Robert Powers
Office
Labs
Address: 722 HaH
721 HaH
Phone: 472-3039
472-5316
e-mail:rpowers3@unl.edu
web page: http://bionmr-c1.unl.edu/
Office Hours: 10:30-11:30 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
Course Outlined (cont.)
Course Work:
Exam 1:
Exam 2:
Exam 3:
Final:
Written Report:
Problem Sets (8):
Total:
100 pts.
100 pts.
100 pts.
200 pts.
50 pts.
150 pts.
700 pts.
(Mon., Feb. 4)
(Fri., Mar. 1)
(Mon, Apr. 8)
(10-12, Wed., May 1)
(Fri., Apr. 13)
(various due dates)
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: A+=95%; A=90%; A-=85%; B+=80%; B=75%; B-=70%;
C+=65%; C=60%; C-=55%; D=50%; D-=45%; F=40%
Course Outlined (cont.)
Class Participation
• Reading assignments should be completed prior to each lecture.
• You are expected to participate in ALL classroom discussions
Exams
• All exams (except the final) will take place at 6 pm in Hamilton Hall Rm.
130 on the scheduled date.
• The length of each exam will be open-ended. You will have as much time
as needed to complete the exam.
• Bring TI-89 style calculator or a simpler model, approved translator and
text book (you will be able to use certain charts, tables and appendix)
• A review session will take place during the normal class time.
• ALWAYS SHOW ALL WORK!!!!
Course Outlined (cont.)
Problem Sets
• Problem sets are worth either 15 or 20 points each and are selected from
the questions/problems at the end of each chapter in the text.
• You may work together in groups, but everyone must submit their own set
of answers to the problem set.
• Please feel free to visit me during office hours for assistance in answering
the problem sets.
• You must show all work to receive full credit.
• Problem sets are due at the beginning of class on the due dates listed in
the syllabus course schedule.
 Late Problem sets will incur a 5 point penalty.

Problem sets will not be accepted after the next problem set due
date has occurred or after the last day of class.
Course Outlined (cont.)
Problem Sets (cont.)
• Students generally perform very well on the problem set, which provides a
“grade cushion” to the more challenging Exams.
PLEASE DO THE PROBLEM SETS!
• DO NOT USE THE INTERNET, ANSWER KEYS OR SOLUTION
MANUALS TO COMPLETE YOUR PROBLEM SET.
 Failure to comply will result an automatic zero score for ALL problem
sets.

You will receive a zero out of the possible 150 points

Penalty will occur for a single infraction.

A single problem on a single problem set – no exceptions.
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
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, Analytical Biochemistry Trends in
Analytical Chemistry(TrACs), C&E News, Science, Nature
• Grading (50 points total)
–
–
–
–
–
Content
Clarity of Presentation
Comprehension of material
Paper topic needs to be approved by Monday, March 4th
Due Date: 11:30 am, Friday April 12th
PAPER ON INSTRUMENTAL METHODS
• Your Paper is Not a “Cliff” Notes Summary of a Scientific
Journal Article
– Write the paper in a manner that explains the technique or
application to a colleague or friend
– Use Specific Data and/or Comparisons
– Examples:
• Poor – “mass spectrometry is very sensitive”
• Excellent – “mass spectrometry has very high femtogram limits of
detection compared to the micrograms required by NMR.
– Use Figures within the text
• It is much easier to describe a concept or results by referring to and
describing the details of a figure
•
DO NOT PLAGIRAZE!
– Plagiarism will result in an automatic failing grade and the incident
of academic dishonesty will be reported to the Dean of Students.
Lecture Topics
Date
Chapter
Topic
I. Introduction to Analytical Chemistry
Jan 7
Chap 1
II. Spectroscopic Methods
Jan 9
Chap 6
Jan 11
Chap 6
Jan 14
Chap 7
Jan 16
Chap 7
Jan 18
Jan 23
Chap 13-14
Jan 25
Chap 13-14
Jan 28
Chap 13-14
Jan 30
Chap 15
Feb 1
Feb 4
Feb 6
Chap 16-17
Feb 8
Chap 16-17
Feb 11
Chap 18-19
Feb 13
Feb 15
Chap 8-10
Feb 18
Feb 20
Chap 26
III. Separation Methods
Feb 22
Feb 25
Feb 27
Mar 1
Introduction
Introduction to Spectroscopy
Instrumentation for Spectroscopy
Problem Set #1 due
UV/Visible Molecular Absorption Spectroscopy
Molecular Luminescence Spectroscopy
Problem Set #2 due
EXAM 1
Infrared Spectroscopy
Raman Spectroscopy
Problem Set #3 due
Atomic Spectroscopy
Problem Set #4 due
Introduction to Chromatography
Chap 27
Chap 27
Gas Chromatography
Problem Set #5 due
EXAM 2
Lecture Topics
Date
Chapter
Topic
Mar 4
Mar 6
Mar 8
Mar 11
Chap 28
Chap 28
Chap 29-30
Liquid Chromatography/Paper Topic Approvals
Problem Set #6 due
IV. Electrochemical Methods
Mar 13
Chap 22
Mar 15
Chap 22
March 17-24
Mar 25
Chap 22
Mar 27
Chap 23
Mar 29
Chap 23
Apr 1
Chap 24
Apr 3
Chap 25
Apr 5
Apr 8
V. Other Techniques
Apr 10
Apr 12
Apr 15
Apr 17
Apr 19
Apr 22
Apr 24
Apr 26
May 1
Other Separation Methods
Chap 19
Chap 19
Chap 19
Chap 19
Chap 11,20
Chap 11,20
Introduction to Electrochemistry
Spring Break
Potentiometry
Coulometry
Voltammetry
Problem Set #7 due
EXAM 3
NMR
Instrumental Methods Paper Due
Mass Spectrometry
Problem Set #8 due
Review Session
FINAL EXAM
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-1930’s)
a.) separations: chromatography, electrophoresis, etc.
b.) Qualitative or Quantitative: spectroscopy, electrochemical methods,
mass spectrometry, NMR,
radiochemical methods, etc.
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?
Other factors: speed, convenience, cost, availability, skill required.
How Do We Answer or Address These Questions?
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 – don’t know “true” value
Two types of error: random or systematic
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)
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, low precision
High accuracy, low precision
Low accuracy, high precision
High accuracy, high precision
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):
SD 
n
2
(
X
i

X
)
/( n  1)

i 1
Relative Standard Deviation (RSD) or
Coefficient of Variation (CV):
RSD (%)  ( SD / X )100
where: n = total number of measurements
Xi = measurement made for the ith trial
X = mean result for the data sample
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.
sulfate calibration curve
y = 14427x - 12024
R2 = 0.999
1400000
1200000
peak area
1000000
800000
600000
400000
200000
0
0
10
20
30
40
50
60
concentration (ppm )
by area
Linear (by area)
70
80
90
CHARACTERISTICS OF AN ANALYTICAL METHODS
S = mc + Sbl
Parameters used to Describe a Calibration Curve:
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.
70
60
50
Method A
40
30
Method B
20
10
0
0
2
4
6
8
Concentration (mM)
10
12
Selectivity:
degree to which the method is free from interference by other
species in the sample
70
No method is totally free from
interference from other species.
60
50
40
Selectivity coefficient (k):
Species A
30
kB,A = mB/mA
20
Species B
Relative slopes of calibration
curves indicate selectivity:
10
0
0
2
4
6
8
Concentration (mM)
10
12
S = mA(cA + kB,Acb) + Sbl
Interested in detecting species A, but signal will be a combination of signal
from the presence of species A and species B.
Limits of Detection (cm ): (minimum analyte signal (Sm) - mean blank signal(Sbl ))/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.)
signal
noise
Estimate S/N:
1) Multiple determination of
blank samples.
2) Estimation of best-fit to
calibration curves
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)
Example 1: The data in the table below were obtained during a colorimetric determination
of glucose in blood serum.
Glucose
Concentration, mM
Absorbance, A
0.0
0.002
2.0
0.150
4.0
0.294
6.0
0.434
8.0
0.570
10.0
0.704
A serum sample gave an absorbance of 0.350. Find the glucose concentration and its
standard deviation, calibration sensitivity, detection limit and dynamic range.