Spectrometry

Question 1

Qualitative Analysis

Answer 1

1. What is the identity or properties of the drug or substance?
2. Separation, isolation, or purification required in most cases, but not all

Question 2

Quantitative Analysis

Answer 2

1. How much substance is present

Question 3

Major identification technique involves the interaction of the molecules of interest with ____________________

Answer 3

Electromagnetic Energy

Question 4

Electromagnetic energy has properties of ________ and has ____________ and wavelengths

Answer 4

1. Properties of waves

2. Has frequency

Question 5

Frequency

Answer 5

1. Hertz (hz) (1 cycle/second), kilohertz (1,000 cycles/sec)

2. Think of it as how quickly it gets to you

Question 6

Wavelengths

Answer 6

1. Meters
2. Think of a typical wave going up and down
   Example: standing on beach- every time waves hits you that’s the frequency. Distance between the peaks and trophy is the wavelength

Question 7

1 micron (u)

Answer 7

10-6 meters

Question 8

1 nanometer (nm)

Answer 8

10-9 meters (1 mu)

Most frequently seen in chemistry

Question 9

1 angstrom (A)

Answer 9

10-10 meters

Question 10

The Electromagnetic Spectrum: Radio, tv, radar VS x rays and gamma rays?

Answer 10

1. Radio, tv, radar: lower frequency, long wavelengths

2. X rays and gamma rays: high frequency, short wavelengths

Question 11

Wavelengths of the visible part of the spectrum in nanometers and in angstroms:

Answer 11

1. 390 nm-750 nm

2. 4300 A (violet)- 7000 (red)

Question 12

The shorter the wavelength, the ____________ the frequency and the ___________ the energy

Answer 12

1. The greater the frequency

2. Higher the energy

Question 13

Angstrom length (m)

Answer 13

10 (-10)

Question 14

Nanometer Length

Answer 14

10 (-9)

Question 15

Micrometer

Answer 15

10 (-6)

Question 16

Millimeter length

Answer 16

10 (-3)

Question 17

Centimeter length

Answer 17

10 (-2)

Question 18

Meter length

Answer 18

1

Question 19

As molecules are exposed to light (or other energy) they can absorb energy by:

Answer 19

1. Electromagnetic excitation: electrons in the molecule goes from low energy state to a higher energy state
2. Molecular vibrations: each compound has a natural vibration frequency

Question 20

After a molecule is excited it can release the energy in various forms: (3)

Answer 20

1. Heat ** most common result
2. Rupture of molecule
3. Re-emission of energy as altered electromagnetic energy (fluorescence)

Question 21

The useful parts of the spectrum are UV, visible, and ________ radiation?

Answer 21

1. Infrared radiation

Question 22

UV and visible absorption:

Answer 22

1. Electronic absorption (electrons in molecules are excited to a higher energy state). Then they relax and emit energy

Question 23

Infrared absorption is due to:

Answer 23

1. Vibrational energies of a molecule: bending, stretching, and rotation. (lower energy radiation)

Question 24

Most molecules have chromophores that do what?

Answer 24

1. Absorb light.

2. Chromophores may be certain molecular groups, such as phenyl groups or double bonds

Question 25

Basic instrument components: (4)

Answer 25

1. Energy source to produce radiation, usually UV or visible light by deuterium (UV) or tungsten lamp (visible)
2. A system to select limited part of spectrum (prism or grating)
3. Sample chamber
4. Detector (photomultiplier tube-converts light energy to electrical energy)

Question 26

For any compound, absorbency is proportional to: (2)

Answer 26

1. The thickness of the cuvette (or light path)— thicker=more absorption
2. Concentration of the compound

Question 27

Absorption is dependent on the probability of radiation causing an electron being ___________ in the substance?

Answer 27

1. Electron being excited.

2. If coefficient is small, substance poorly absorbs light

Question 28

Light intensity across a cell is exponential decay equation?

Answer 28

Log 10= IO/I = K X L / 2.303

I= emergent light
IO= incident light
K= constant for any pure compound
L= length of light path

Therefore, absorbance is proportional to the thickness of the cell (L)

Question 29

Absorbance, extinction and optical density?

Answer 29

1. All mean the same thing, that light is being absorbed

Question 30

Beer- Lambert Law

Answer 30

A= E X L X C

If c is measured in moles x L (-1), and length (L) is in cm, then E has the units of L x moles (-1) x cm (-1). This is referred to as the molar absorption coefficient
Note: beer-lambert law assumes one wavelength

Question 31

Using multiple wavelengths different compounds in a single solution can what?

Answer 31

1. Both can be measured
2. Example: Nad+ and NADH
3. Wavelength that gives the best absorbance is usually chosen for compound measurement, however, when measuring NADH for example it is best to use the wavelength of maximum difference