CHEM 524 -- Course Outline (Sect

CHEM 524-- Course Outline (Sect. 1)

FOR A PDF VERSION OF THE 2002 NOTES WITH EMBEDDED FIGURES CLICK HERE

I.Introduction -- Optical Spectroscopy in Analytical Chemistry

Review of Syllabus materials, see handout

Obtain a class list with contact and interests

A.Analytical uses of Spectroscopy

1.Qualitative --"what is it?"

àProperty detection (characteristic of analyte)

Spectral transitions -- difference in E-levels

Types of transitions -- spectral region studied (ref. Text: Table 1-1)

2.Quantitative --"how much is it?"

àgenerally used to detect concentration

Optical Spectra --sensitive and widely useful, conc. to pM

--flexible and general, all states (gas, liq. sol.)

Calibrateby comparison to a standard (determine a linear range)

Simple/inexpensive-- many commercial instruments available

B.Spectroscopy -- (Assign: -- Read text: Chap 1 & 2, establish terms)

1. Responseof system to light -- as function of frequency /wavelength

--process is important to determine detectability, selectivity

--absorption, emission, excitation, scattering, ionization, etc.

2. Needs: Source - depends on spectralregions

Control light (optics)--to maximize S/N

Sampling- vital for accuracy, - species/question dependent

Detection- spectral region and sensitivity dependent

Analysis--involves: standards/linearity/interference

3. Types ofAnalyses:

Dispersionof response à Qualitative

Amountof response à Quantitative

4. Basic Quantities

Wavelength/frequency -- (ref.Text: Table 1-1)

Measures of light strength: from source and onto detector

--(ref. Text: Table 2-1. Table 2-2)

Energy: Q, à Flux: F=dQ/dt; à Intensity: I=dF/dW

Source radiance: B(l)=d²F/dWdA_scosq

Irradiance on Detector:E=dF/dA_det

5. Methods -- all analyte population dependent

Absorbance/transmittance (figure I-1):

T=F/F_o à A = -log₁₀(T)-- derive dF = -k(c) F(z) dz

Beer Lambert Law: A=e(l)bc , e--[M^-1cm^-1], const. range of c

Concentration dependence has a linear regime (land instr. dep.)

Cross-section: s–[cm²], A =0.434 s b n , n — conc. in number[#/cm³]

Note: Need 2 measurements for absorption, Fand F_o,

Optional design, double beam, done simultaneously

Emission (figure I-2): – emitting states in equilibrium (thermal), n_j~n_t

Luminescence – specific state excited (cool), n_j~n_t

Works if low abs. F_L= kF₀(1-10^-A)-- expand

Scattering --elastic (w_s= w_o) and inelastic (w_s< w_o),

Figure 1. Absorption schematic Figure 2. Emission schematic

Homework link to set #1

Text reading this sectioncovers: Chapter1, Chapter 2-2, 2-3, 2-5

Read on your own: Chap.2-4Selection of information (we will do later)

Chap.2-5Analytical signal — Sorting out various contributions to the signal measured from background, etc. — This topic will recur and be tested.(also Sect. 7-10)

Homework: (For discussion only: Chap. 1:#3, 4, 6, 10, Chap. 2 #5, 10

Chap2: #1, good model test question, often on 1^st exam)

To eventually hand in: Chap.2: # 3, 4 (assume all light hits detector), 15, 16 &

Calculate population of molecular states for vibrations at 100, 600 cm^-1 and3000 cm^-1 for T=300K

Link to slides used in class

Links to spectroscopy courses on line:

Course on several methods, byBrian Tissue, giving a instrumental analysis level survey, (on a Korean server)may be incomplete, quite terse, some figures

http://elchem.kaist.ac.kr/vt/chem-ed/analytic/ac-meths.htm- spectroscopy

http://elchem.kaist.ac.kr/vt/chem-ed/courses/spec/toc.htm- intro

MIT lab course – links to pdf files – Phys chem. labstyle—two versions:

http://web.mit.edu/5.33/www/lectures.html

http://ocw.mit.edu/OcwWeb/Chemistry/5-33Advanced-Chemical-Experimentation-and-InstrumentationFall2002/LectureNotes/

Akron University molecular Spectroscopy organic course, very simple

http://ull.chemistry.uakron.edu/analytical/Mol_spec/

Iowa Statecourse, properties of light,

http://avogadro.chem.iastate.edu/CHEM513/513-1.pdf

physicaloptics

http://avogadro.chem.iastate.edu/CHEM513/513-2.pdf

http://avogadro.chem.iastate.edu/CHEM513/513-3.pdf