Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

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0004 Since the energy required to stimulate an electronic

transition is greater than that for a vibrational transi-

tion, which in turn is greater than for rotational

transition, it is found that more than one transition

is usually stimulated so that, for example, pure vibra-

tional spectra are not seen and are nearly always

complicated by rotational transitions.

0005 The normal way for interaction of the radiation to

occur is through one of four processes: (1) absorption,

(2) emission, (3) elastic scatttering, although there is

not net energy absorption, and (4) inelastic scattering.

These mechanisms are described in more detail under

the appropriate headings as the spectroscopies are

discussed in more detail. The first to be discussed

are ultraviolet and visible (UV/VIS) spectroscopies,

both of which involve electronic transitions.

Electronic Transitions

0006 In UV/VIS spectroscopies, absorption of radiation is

the result of the excitation of bonding electrons. The

types of bonds that give rise to absorption are known

as chromophores and in the UV the electrons of the

chromophore are either directly used in bond forma-

tion or are nonbonding or unshared outer electrons of

an electronegative atom, such as oxygen, nitrogen, or

sulfur. The general mechanism in a chromophore such

as C

—

C, in which orbitals are used for bonding, in-

volves the promotion of an electron in a bonding p

orbital into a nonbonding p* orbital (a so-called pp*

transition), which typically requires about 7 eV, cor-

responding to a wavelength of 180 nm. It is also pos-

sible for a nonbonding electron to be promoted to a p*

(an np* transition). These two are the most common

transitions, although similar ones exist for single (s)

bonds (ns*orss*). However, because the latter

required much higher energies, they are seen in the

vacuum-UV and are harder to observe. The frequen-

cies of the absorption can be influenced by solvents

and by delocalization in conjugated systems.

0007Transition-metal ions absorb in the UV/VIS region

and the transitions responsible involve 4f and 5d

electrons. Alternatively, in some inorganic complexes

the process of charge-transfer absorption occurs.

0008Most UV/VIS spectroscopy involves absorption

processes and normally a spectrophotometer is used

to measure a spectrum. The major components are a

source, a dispersing system, and a detector. Normally,

light from a suitable source is passed to a prism or

grating where it is dispersed into its component fre-

quencies. The dispersing element may be rotated so

that each frequency is passed in turn through a

narrow slit. This light may be divided so that half

passes through a channel containing the sample and

half through a reference channel. The emerging

beams can be directed in ratios at a detector and the

absorbance of the sample as a function of frequency

(or wavelength), i.e., the spectrum, can be plotted.

0009It should be noted that UV/VIS spectra do not

consist of discrete lines. The reason is that the high

energy of the UV/VIS region can be transferred into

the vibrational and rotational substates so that both

types of transition are simultaneously stimulated. In

Figure 2 the energy level diagram for a chromophore

is shown. E

and E

represent the ground and excited

electronic energy levels of a molecule. Each electronic

level has associated with it various vibrational sub-

levels, v

0,1

0,2

, etc., which in turn have rotational

sublevels. An electron may be promoted from the E

to E

electronic state but may go from the v

0,0

to v

1,0

or v

1,1

state; i.e., there is a simultaneous vibrational

transition. The range of vibration subtransitions pos-

sible, combined with rotational transitions, means

that there is no discrete frequency at which transition

occurs.

0010Furthermore, if an electron is promoted from the

0,0

state of E

to the v

1,1

state of E

it may lose

energy by collision, for example, and may become

lowered into the v

1,0

state. During relaxation to

the ground electronic state a photon is emitted of

Radio frequency

NMR ESR UV/VISMicrowave Infrared X-ray

γ-ray

−8

eV 10

Increasing energy

10 m 100 cm 1 cm

100 µm1 µm 10 nm 10 pm

Increasing wavelength

fig0001 Figure 1 The electromagnetic spectrum. NMR, nuclear magnetic resonance; ESR, electron spin resonance; UV/VIS, ultraviolet and

visible. Reproduced from Spectroscopy: Overview, Encyclopaedia of Food Science, Food Technology and Nutrition, Macrae R, Robinson

RK and Sadler MJ (eds), 1993, Academic Press.

SPECTROSCOPY/Overview 5407

different energy from that absorbed, and this process

is called fluorescence.

Vibrational Spectroscopy

0011 The transitions between the vibrational energy levels

are the basis of infrared and Raman spectroscopies.

The infrared region is divided into the near, middle (or

mid) and far infrared. This division is on the basis of

instrumental factors as well as the types of vibration

that occur in each region. It is easiest to consider first

the middle infrared, which is usually considered to lie

between 2.5 and 25 mm in wavelength. It is common

practice, however, for vibrational spectroscopists to

usetheunitwavenumber(reciprocalofthewavelength

in centimeters) rather than wavelength; this has units

of cm

1

, which is a frequency term. The middle infra-

red then stretches from 4000 to 400 cm

1

0012 The bond between two atoms can be considered to

be rather like a spring that has a certain strength of

force constant (k). The bond, or spring, can be

stretched and caused to oscillate. It will do so at

some natural frequency, f, that depends upon k and

the masses of the atoms according to Hooke’s law:

f ¼ð1=2 pÞ

ﬃﬃﬃﬃﬃﬃﬃﬃ

k=m

ð2Þ

where m is the reduced mass given, defined as:

m ¼ðm

Þ=ðm

þ m

Þð3Þ

and m

being the masses of the individual atoms

constituting the bond. Equation (2) shows that a

particular bond will give rise to a characteristic

frequency that depends upon the masses of the atoms

and the strength of the bond. Therefore, a C

—

O bond,

which has a greater force constant than a C—O bond,

will have a vibrational frequency which is larger. In

practice, different functional groups give rise to char-

acteristic vibrational frequencies. This is the major use

for vibrational spectroscopy; it is a highly useful probe

for the identification of functional groups and for

structural determination. It has greater selectivity

than UV/VIS in this respect.

0013Equation (2) is derived from classical physics, but

of course the actual process is quantized and (2)

should be written as:

F ¼ðh=2p Þ

ﬃﬃﬃﬃﬃﬃﬃﬃ

k =m

ð4Þ

where h is Planck’s constant.

0014In the main, an infrared spectrum is generated by

absorption using a similar arrangement to that used

for UV/VIS but with different source, detector, and

dispersing optics. The process is illustrated in

Figure 3. The energy level diagram shows the ground

0,0

) and excited (v

1,0

) vibrational states. Also shown

are the various rotational substates (J

and J

). Exci-

tation can occur from v

0,0

¼ 0) to v

1,0

¼ 0),

corresponding to the band center of the absorption

band. However, excitation from the J

¼ 1toJ

¼ 1

rotational substates (i.e., DJ ¼ 0) will produce a

slightly different frequency as the rotational sublevels

are not equally spaced. It is also possible for DJ to be

+1, giving rise now to a complicated absorption

1,1

1,0

0,1

0,0

Energy

Electronic absorption

with simultaneous

vibrational transition

Emitted radiation

equal to absorbed

Origin of

fluorescence

Emitted energy

of different

from absorbed

fig0002 Figure 2 Energy levels for a chromophore, showing electronic

and vibrational levels. Reproduced from Spectroscopy: Over-

view, Encyclopaedia of Food Science, Food Technology and Nutrition,

Macrae R, Robinson RK and Sadler MJ (eds), 1993, Academic

Press.

J' = 2

J' = 1

J' = 0

J'' = 2

J'' = 1

J'' = 0

1,0

0,0

Energy

∆J = 0 ∆J = +1

∆J = +1

∆J = −1

Q branch R branch P branch

nb: For all absorptions ∆v = 1

PQR

fig0003Figure 3 Energy levels for infrared transitions, showing vibra-

tional and rotational levels. Reproduced from Spectroscopy:

Overview, Encyclopaedia of Food Science, Food Technology and Nu-

trition, Macrae R, Robinson RK and Sadler MJ (eds), 1993, Aca-

demic Press.

5408 SPECTROSCOPY/Overview

band comprising of a central absorption (Q branch)

with equally spaced lines either side called the P branch

(DJ ¼1), and the R branch (DJ ¼þ1). This structure

is only seen as such in the gas phase. In solid or solution

state the result is that a broad absorption rather than a

sharp line is seen. However, no absorption will be seen

at all unless the selection rule is applied. This states

that for absorption to occur there must be a change in

dipole moment during the vibration. Consequently,

homonuclear bonds do not absorb.

0015 At normal room temperature most molecules will

be in the ground vibrational state. However, as the

temperature is increased, a more significant popula-

tion will develop in the excited state. As a result

transitions from the v

to v

state can occur with the

emission of a photon. This is the process of infrared

emission which is, albeit rare, an alternative to

absorption spectroscopy. In this case the (heated)

sample acts as the infrared source.

0016 Infrared spectroscopy has, until recently, been of

little use for industrial, biological, and food use owing

to the difficulties of sample handling and the time of

data acquisition. However, the recent development of

Fourier transform methods involving the replacement

of the dispersing element with an interferometer has

benefits of increased speed, throughput, and fre-

quency reproducibility. Coupled with new methods

of sample presentation, this has led to a reawakening

of interest in the middle infrared.

0017 The absorptions in the middle infrared are known

as the fundamentals. However, various overtones and

combinations of the fundamentals can arise. For

example, a molecule with two fundamentals at fre-

quencies v

and v

may give overtones at 2v

,3v

,or2v

, etc., or combinations at, say, v

þv

. In practice, not all fundamentals give rise to

overtones, usually only bonds in which a heavy atom

such as N or O is coupled to hydrogen. The overtone

and combinations constitute the near infrared

(2.50.7 mm) which, despite the apparent complexity

of the spectra, has found considerable application to

food problems.

Raman Spectroscopy

0018 If a sample is illuminated with monochromatic visible

light, it is found that much of the light is scattered and

that the scattered light is of the same frequency as the

illuminating light. This is elastic or Raleigh scattering.

However, analysis shows that a small amount

(< 10

6

) of the incident radiation is scattered with a

different frequency. A series of lines is found with

frequencies less than the incident light. A weaker

series is found with higher frequencies. When the

former set of lines are presented as a spectrum of

intensity versus frequency shift, the result is some-

thing similar to an infrared spectrum with the shift

scale from about 4000 to 20 cm

1

. This effect is the

Raman effect and the spectrum is called the Raman

spectrum. The lines comprising the spectrum are

called Stokes lines. Those of higher frequency than

the exciting line are called anti-Stokes lines and con-

sist of the same peaks with the same shift, but there

may be different intensity ratios.

0019The electrical field of the incident radiation inter-

acts with the electrons in the sample and causes peri-

odic polarization and depolarization so that energy is

momentarily absorbed in a distorted, polarized state

or virtual state. Most molecules relax by the emission

of energy of the same frequency to that absorbed. In

a few cases some of the energy will be dissipated

amongst the vibrational energy levels, causing vibra-

tional excitation and giving rise to the Raman spec-

trum. Even fewer molecules will not be in the ground

vibrational state before excitation but in the virtual

state may relax and the emitted photon will be of

higher energy than that incident, leading to the anti-

Stokes lines. In contrast to infrared spectroscopy, the

selection rule for absorption is that, during vibration

of the bond, there must be a change in the electronic

polarizability. There is thus a distinct difference in the

two spectra and vibrations that may be weak or absent

from infrared spectra, e.g., C—C are present and per-

haps strong in the Raman. The two spectroscopies are

thus complementary and together provide a complete

picture of the vibrational states of a molecule.

Far Infrared/Microwave

0020To complete the picture, at lower energy there is the

far infrared (40010 cm

1

), which has major appli-

cations in inorganic chemistry as bonds between

metals and organic ligands appear here as well as

skeletal vibrations of molecular backbones. This

region is of limited application in food and nutritional

studies.

0021In the microwave region, at even lower energy,

pure rotational spectra can be produced. However,

they will not be addressed here as this is also of

limited application.

0022At the radiofrequency end of the spectrum is NMR

spectroscopy which involves transitions between

magnetic quantum levels of atomic nuclei. Nuclei

have properties of spin and magnetic moment. Split-

ting of the energy levels can be induced by placement

in a magnetic field and transitions can be induced by

the application of radiofrequency radiation. Today,

this is usually achieved by irradiating the sample ex-

posed to a high magnetic field with a pulse of broad-

band radiation. After excitation the nuclei reemit

SPECTROSCOPY/Overview 5409

energy at their resonance frequencies and the observed

signal is a combination of these frequencies, and this

decays with time. A spectrum can be produced by

Fourier transformation of this decaying signal. The

usefulness of the technique lies in the fact that the

resonance frequency of a given nucleus depends upon

its chemical environment. However, the range of

NMR experiments possible is very large indeed and

it is a very powerful method for structural analysis.

0023 In the food industry the use of NMR spectra as

such is increasing but relaxation time measurements

are still more important, particularly in the determin-

ation of solid/liquid ratios. The relaxation rate from

the excited state depends on environmental factors

and molecular mobility.

Absorption Laws

0024 In UV, near infrared, and mid-infrared adsorption

spectroscopy, the fundamental law governing adsorp-

tion is the Beer–Lambert relationship. For a sample

illuminated by radiation of intensity I

the amount

transmitted, I, is given by:

I ¼ I

ecl

ð5Þ

where c is the concentration of absorbing species, l is

the pathlength through which the light passes, and e

is the molar absorptivity.

0025 For quantitative analysis, spectra are usually pre-

sented in absorbance units, where absorbance, A,is

defined as

A ¼logðI=I

Þ¼ecl ð6Þ

so that A is directly proportional to the concentration

at constant pathlength.

0026 Practically, optical spectroscopy requires that e

be determined for any absorbing species. This is

achieved by calibration and their absorbance is meas-

ured. Solutions of the sample to be determined are

prepared at known concentration and their absor-

bances are measured. When the latter are plotted

against the concentration, a linear plot results of

slope e. Unknown concentrations can be calculated

by measuring absorbance and interpolating from the

calibration curve.

0027 Deviations from the Beer–Lambert relationship can

occur if too wide a range of concentration is chosen so

that solute–solute interactions occur, or where there is

chemical interaction between components.

0028 A particular problem that exists in the near and

mid-infrared is where significant overlap of absorb-

ance peaks occurs. Clearly, the absorbance at a given

wavelength may then depend upon more than one

concentration, so that:

A ¼ e

¼ e

þ e

... ð 7Þ

Hence, more complicated solutions to the Beer–

Lambert relationship may be required for multi-

component analysis. Such methods include p and k

matrix, partial least-squares, or principal components

regression.

0029In NMR single-pulse experiments the signal ob-

served is directly proportional to the number of

nuclei, provided sufficient time is allowed between

pulses for the reestablishment of equilibrium. Under

such circumstances the NMR experiment is quantita-

tive and requires no calibration. Double-resonance

experiments can, however, lead to enhanced signals

for certain nuclei (nuclear Overhauser effect) so that

some form of calibration is necessary. In relaxation

measurements the magnetization decay can be broken

down into components from fast (solid) and slow

(liquid) components, the relative magnitude of each

reflecting the relative concentrations.

0030Practical details and applications of the most rele-

vant spectroscopies in food analysis can be found in

following chapters.

See also: Spectroscopy: Infrared and Raman; Near-

infrared; Fluorescence; Atomic Emission and Absorption;

Nuclear Magnetic Resonance; Visible Spectroscopy and

Colorimetry

Further Reading

Andrews DL (ed.) (1990) Perspectives in Modern Chemical

Spectroscopy. Berlin: Springer-Verlag.

Banwell CN and McCash EE (1994) Fundamentals of

Molecular Spectroscopy, 4th edn. London: McGraw

Hill.

Colquhoun IJ and Goodfellow BJ (1994) Nuclear magnetic

resonance spectroscopy. In: Wilson RH (ed.) Spectro-

scopic Techniques for Food Analysis. New York: VCH.

Wilson RH (ed.) (1994) Spectroscopic Techniques for Food

Analysis. New York: VCH.

Infrared and Raman

B Schrader, Essen, Germany

S Keller, Hamburg, Germany

Principles

0001A molecule can be identified uniquely by its vibra-

tional spectrum, since this depends on every struc-

tural feature. The vibrational spectrum consists of

the frequencies and intensities of the vibrations

5410 SPECTROSCOPY/Infrared and Raman

observed by infrared and Raman spectroscopy. Both

are nondestructive methods. This means that the

samples can be investigated afterwards by other

methods. The intensity of the bands in the infrared

and Raman spectra gives complementary information

about the nature of the vibrating bonds. Therefore, it

is advisable to evaluate both the infrared and Raman

spectra in order to obtain the maximum amount of

analytical information.

0002 Now, the advantages of both methods, IR and

Raman spectroscopy, can be employed by power-

ful spectrometers, thus making vibrational spectros-

copy a very useful tool in food analysis. State-of

the-art instruments for vibrational spectroscopy

are equipped with interferometers coupled to com-

puters for the transformation of interferograms

into spectra, so-called Fourier transform infrared

(FTIR), Fourier transform near-infrared (FTNIR),

or FT Raman spectrometers. Compared with

grating instruments, interferometers have several

advantages, in particular the fact that the radiant

flux analyzed is larger by about two orders of

magnitude. Interferometers therefore permit reliable

routine analyses of small samples and of low concen-

trations.

2000 0/cm

−1

4000

(a)

(b)

2500 1800 1500

OH NH CH SH

XYX Y X Y

ZYZ

2πc

fig0001Figure 1 Principles of infrared and Raman spectroscopy: (a)

model and equation describing frequency of diatomic molecule;

(b) frequency ranges of different small molecules.

VIS-Raman

488 nm

100%

(b)

QY: 10

−10

(c)

Fluorescence

QY:

(d)

NIR-Raman

1064 nm

46%

QY: 10

−12

Infrared

(a)

Quantum

yield (QY)

QY: 10

−2

fig0002 Figure 2 Term scheme of spectra: (a) infrared; (b) Raman (excitation in the VIS); (c) fluorescence; (d) Raman (excitation in the NIR).

tbl0001 Table 1 Comparison of infrared, near-infrared and Raman spectrometry

Infraredspectrometry Raman spectrometry Near-infrared spectrometry

Sample preparation Partly expensive, moisture-sensitive Simple Simple

Sample container Cells of KBr, NaCl, ZnSe, Si, Csl, TlBr/TlJ Glass, quartz Glass, quartz

Bands of water Strongly disturbing Low intensity Strong intensity

Observed vibrations Antisymmetric polar groups, substituents Symmetric unpolar

groups, skeletons

Overtones and combinations

of C—H, N—H and O—H

Intensity, I, , concentration, c log(l

/l) * cl* c log (l

/l) * c

Spectral range 400–4000 cm

1

standard, 10–400 cm

1

with FIR-optics

10–4000 cm

1

4000–12 500 cm

1

SPECTROSCOPY/Infrared and Raman 5411

Basic Theory

0003In Figure 1, the theory necessary to understand infra-

red and Raman spectroscopy is outlined. Every mol-

ecule can be considered as being built up from atoms

with a definite mass, connected by chemical bonds

behaving like elastic springs (Figure 1a). The fre-

quency,

nn, is usually measured in wavelengths per

centimeter, called the wavenumber (cm

1

). For a di-

atomic molecule of two bound atoms, the frequency

of the vibration is proportional to the square root of

the force constant (f ), – which is approximately pro-

portional to the bond order – and the sum of the

reciprocal masses.

0004For larger molecules, the vibrations of the frag-

ments couple and produce complicated ‘fingerprint’

patterns. However, most of the structural units

keep their typical frequency range. Thus, X—H

bonds, with X any element, show their typical vibra-

tions between 4000 and 2500 cm

1

(Figure 1b),

followed by groups with triple bonds or cumulated

double bonds in the range 2500–1800 cm

1

. Groups

with ‘double’ bonds show their characteristic vibra-

tions between 1800 and 1500 cm

1

, and groups

tbl0002 Table 2 Characteristic frequencies and Raman and infrared

intensities of food components

Assignment Infrared

(cm

1

)

Raman

(cm

1

)

d(C—O), sugar 479

n(S—S) 520–540

Phenylalanine (skeletal) 622

Tyrosine (skeletal) 642

Adenine 725

Thymine 750

Breathing vib. (a-anomers,

Type III, sugar)

756–776

Tryptophan 759

Breathing vib. (b-anomers,

Type III, sugar)

765–783

Cytosine, uracil (ring, str) 785

n(—O—P—O—)

, A-helix 810–814

Tyrosine 829

n(—O—P—O—)

, B-helix 830

—H bending (a-anomers,

Type II, sugar)

836–852 840–850

Tyrosine 852

—H bending (b-anomers,

Type II, sugar)

884–898 890–910

Ring vibration (a-anomers,

Type I, sugar)

904–930

Ring vibration (b-anomers,

Type I, sugar)

915–925

n(PO

)

s,as

960

(C—N

—C), choline 970

Phenylalanine 1004

n(C—N) and n(C—C) 1061

Deoxyribose – Z-DNA 1065

n(O—P

—

—O)

1070–1100 (m) 1080–1100 (s)

n(C—N) and n(C—C) 1093

n(C—N), n(C—C) 1129

n(C—C), carotenoids 1157

n(PO

3

)

– Z-DNA 1215

n(O—P

—

—O)

1225 (s) 1225 (vw)

Amide III, (b-structure) 1225–1245 (s)

n(PO

3

)

– B-DNA 1225

n(PO

3

)

– A-DNA 1240

Amide III (random coil) 1241–1251

(PO



) 1250

—

—C—H)

i.p.b.

unsaturated

fatty acids

1267

Amide III (a-helix) 1270–1300

(vw, br)

d(CH

), twisting 1295

(CH

)

1342–1180

Tryptophan 1358

n(CH

) 1374

Aspartic acid, n(COO



) 1408

Deoxyribose – A-DNA 1418

Deoxyribose – B-DNA 1425

Glutamic acid, n(COO



) 1437

d(C—H) 1445

d(CH

) 1470

Amide II, d(N—H)

(antiparallel b-sheet)

1510–1540

n(C

—

—C), aromate (tyrosine),

carotinoids

1515 1519

d(N—H), amide II (b-sheet

structure)

1530–1545

Amide II, d(N—H) (a-helix) 1540–1560

Amide II, d(N—H) (random coil) 1535

Amide II, d(N—H)

(parallel b-sheet)

1550

Guanine, adenine (ring, str) 1575

Tryptophan 1578

Phenylalanine 1606

n(COO



), carboxylate 1610

Tyrosine 1614

Tryptophane 1621

Amide I n(C

—

—O) (parallel

b-sheet structure)

1632–1648

Amide I, n(C

—

—O), (a-helical

structure)

1655 1658

Amide I, n(C

—

—O) (random coil) 1655–1660 1665

n(C

—

—C) unsaturated fatty lipids 1657

Amide I, n(C

—

—O) (antiparallel

b-sheet and b-turn structure)

1685–1700 1665–1675

– Z-DNA 1695

– A-DNA 1705

– B-DNA 1715

n(C

—

—O), ester 1720–1750 1746

n(C

—

—O), carboxylic acid 1730

n(CH

)

lipid 2849 2847

Methyl 2872

n(CH

)

, protein, n(CH

)

, lipid 2890

(CH

) 2918

n(CH

)

, lipid, n(CH

)

, protein 2935

(CH

) 2956

n(CH

)

, protein, n(CH

)

, lipid 2975

(CH

)

3028

n(C

—

—C—H)

, lipid 3010

n(NH), n(OH), base sugar 3300–3600 (m)

5412 SPECTROSCOPY/Infrared and Raman

2400 2200 2000 1800 1600 1400 1200 1000 800 600 400

0.2 

200 026002800300032003400

3600

III

L-Cystine

Raman Infrared

499

3678

3784

92917

62969

10101 W

4200 W

393 S

1.5616 M

847 S

1127 S

0.51298 S

2.51340 S

21410 VS

1485 VS

1585 VS

~3030 S

(a)

Grubb Parsons IS 3 Solid B 10 mg/150 mg PE; C 25 mg/150 mg PE 5 cm

−1

Bspl : 6.25  / 25  MW 240.30 m.p. 261d(lit):FIR

: Perkin Elmer 521 Solid A 0.8 mg/400 mg K J 2 cm

−1

B 7 − 01

Coderg PHO Solid ~ 2 mg I 1; II 0.2III Pellet 140 mg 0.3  6/1 cm

−1

EGA5145 A; 700 mWDC; s20; 612; AAA:Ra

2400

MW 294.48

bp.: 215

(lit.)

C2 − 08

2 cm

−1

GC > 98%IR: Perkin−Elmer 521

Liq A 30 µ Cs Br; B 100 µ Cs Br;

2200 2000

1800

1600 1400 1200 1000 800 600 400 200 026002800300032003400

3600

4 cm

−1

DC; S20; 708v; BBB

FLUKA

Ra: Coderg PHO

Liq 0.3; 90; I 1  ⊥;II 0.2  ⊥

5145 A; 1000 mW

Infrared

0.2

0.9

0.8

0.9

0.1

0.5

0.2

0.9

Raman

7.5

838

1072

1265

1440

1658

2905

725

1170

1435

1743

2855

2925

3010

972

Linoleic acid methyl ester

(b)

fig0003 Figure 3 Infrared transmission (above) and Raman spectrum (below) of: (a) cystine; (b) linolenic acid methyl ester; (c) retinol,

vitamin A; (d) caffeine; (e) thiamine hydrochloride, vitamin B

; (f) L-ascorbic acid, vitamin C; (g) a-D-glucose; (h) sucrose. From

Schrader B (1989) Raman/Infrared Atlas of Organic Compounds, 2nd edn. Weinheim: VCH Verlagsgesellschaft with permission.

SPECTROSCOPY/Infrared and Raman 5413

Figure 3 Continued

3600 3400 3200 3000 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 400

Raman infrared

877

965

1004

1008

1078

1155

1193

1266

1270

1278

1359

1382

1448

1586

1627

1664

1717

1.5

9.5

5.5

4.5 sh

200 0

III

CCH

All-trans-retinol

Vitamin A

(c)

IR:

FIR:

RA:

Perkin-Elmer 180

Cary 81

Solid:

ORD, −EXPS. 100

5830 A, 300 MW

DC, S20, 1050V, BBB

3/1

MW 286.46 MP 58−60

C4 − 01

FLUKA

−1

3mm: III 0.1 II 0.2 

A 2.0 mg / 200 mg KCI

B 10 mg / 80 mg PE

1 mm: I 1  ,

3200 3000 2800 2600 2400 2200 2000 1800 1400 1200 1000 800 600 400 200 01600

B/C

III

FIR

Ra.

MW 194.19

I 14 − 02

m.p. 238

EGA

: Grubb Parsons IS 3

Perkin − Elmer 521

Cary 81 DC; S20; 1300; AAB

5 cm

−1

2 cm

−1

6/1 cm

−1

Bspl.: 6.25/25

Solid B/C 20 mg/150 mg PE

Solid A 1 mg/400 mg KJ

Solid 3 mg I 1  II 0.4  ; 250 mg III 0.05  5145 A: 300 mW

Raman infrared

445

483

557

611

644

743

760

974

1023

1239

1283

1324

1358

1487

1551

1601

1656

1699

2957

3115

3.5

0.5

4.5

1.5

3.5

5.5

3.5

13.5

0.5

Caffeine

(d)

Continued

5414 SPECTROSCOPY/Infrared and Raman

Figure 3 Continued

IR:

Solid:

Perkin−Elmer 180

Cary 81 **

FIR:

RA:

3000 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 800 600 400 200 0

A 1.5 mg, B 4.0 mg / 400 mg KI

C 5 mg / 80 mg PE

1 mg: I 1  , II 0.25 2 mm: III 0.1 

2 cm

−1

2 cm

−1

4/2 cm

−1

ORD.−EXPS. 100

5145 A, 2000 MW DC,S20,1120V,BBB

CLN

MW 300.81

FLUKA

J8 − 11

0.7 mg

III

3200

106 24

544

347

6.5

751

937

1382

1252

1478

1608

1648 10

1661

2927

~3028

9.5

1043

1220

581

ν Raman Infrared

HOCH

−

Thiamine

Monohydrochloride

Vitamin B

(e)

IR: Solid:

Solid:

Pellet:

Perkin−Elmer 180

Cary 81 **

FIR:

RA:

(f)

A 0.8 mg / 400 mg KI

L-Ascorbic acid

B 10 mg / 80 mg PE

2 mg: I 1 , II 0.25

2 cm

−1

5 cm

−1

1 cm

−1

ORD.−EXPS. 130

5145 A, 790 MW DC, S20, 1168V, CCB

MW 176.14

MW 190 d

Merck

3600 3400 3200 3000 2800 2600 16002400 1400 1200 1000 800 600 400 200 0

448

367

3.5

628

756

1129

1026

1138

1256

1275

1319

1667

1673

2918

7.5

820

989

565

ν Raman Infrared

5.5

OHHO

Continued

SPECTROSCOPY/Infrared and Raman 5415

Figure 3 Continued

IR: Solid:

Solid:

Perkin−Elmer 180

Cary 81 **

FIR:

RA:

(g)

A 1.0 mg / 400 mg KI

B 10 mg / 80 mg PE

6 mg: I 1  , II 0.25 2 mm: III 0.1

2 cm

−1

2 cm

−1

6/1 cm

−1

ORD.−EXPS. 150

5145 A, 830 MW DC, S20, 1138V, BBC

MW 180.16

MP 147−48

MERCK

III

3200 3000 2800 2600 2400 2200 1400 1200 1000 800 600 400 200 03400

3600

HO OH

α-D-(+)-glucose

404

619

540

913

1022

1117

1110

1148

1343

1457

2840

2945

~3310

1049

1071

839

ν Raman Infrared

7.5

2.5

4.5

3.5

III

Sucrose

IR: Solid:

Solid:

Perkin−Elmer 180

Cary 81 **

FIR:

RA:

(h)

A 3.0 mg/400 mg KI

B 8 mg/80 mg PE

3 mg: I 1  , II 0.2 3 mm: III 0.02 

2 cm

−1

2 cm

−1

5/2 cm

−1

ORD.−EXPS. 150

5145 A, 2000 MW DC, S20, 1170V, BBB

MW 342.30

MP 183−5

K2 − 01

PFEIFER U. LANGEN

3600 3400 3200 3000 2800 2600 2400 2200 1400 1200 1000 800 600 400 200 0

HOH

OH H

HOH

400

638

522

865

906

1067

1036

1122

1235

1280

1347

1460

920

987

846

ν Raman Infrared

4.5

5.5

2912

2940

~3390

5416 SPECTROSCOPY/Infrared and Raman