Fundamentals of Color

Measurement

ISA NorCal TECH May 2

Bill Deutschlander

WorleyParsons 925-313-5628

Spectrum of Light

Near Infrared Ultraviolet

Red

Orange

Yellow

Green

Blue

Indigo

Violet

Microwave

Radio Wave Infrared (IR)

Visible

Ultraviolet

X-Ray

Gamma Ray

10 1 10 10 10 10 10 10 10 10 10 10 10 10 10-1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12 -13

3um 2um 1um 700nm 400nm 200nm

Spectrum of Color measurement

100 206 400 700 1100 Wavelength

(nm)

385 430 550 620 670

Yellow red blue green = color of liquid

Visible Light

(VIS)

Ultraviolett

(UV)

Near Infrared

(NIR)

Color Scales and Terms

• APHA - American Public Health Assoc., Hazen Standard

• ASTM – American Society for Testing and Materials, Hazen and SayBolt Standards

• EBC – European Brewery Convention; 430 nm, 1 cm

• Hazen – Unit of the Color Standard Scale for

APHA/ASTM. Also know as Pt-Co.

• Saybolt – Color Scale unit for Petroleum Products based upon visual comparison of Optical Filters

Photometry - Principles

I0 IR

Absorption of light:

Scattering of light:

IS

I0 ID

Absorption - Lambert Beer´s Law I

I = I0 ·exp[-ε ·c ·d]

T = I / I0

A: Absorbance

T: Transmission

ε: Molar decading coefficient

of absorption (l / mol*cm)

c: Concentration of absorbing

substance (mol / l)

d: optical path length (OPL) (cm)

I 0 I

d

A = – log T = ε ·c · d

Absorption - Lambert Beer´s Law II

A: Absorbance

E: Extinction (Europe)

AU: Absorbance Units

CU: Concentration Units

(competitor)

OD: Optical Density

A = – log T = ε ·c · d

Units of Absorption:

OD = A / OPLcm

Absorption - Lambert Beer´s Law III

0

1

2

3

4

5

Concentration

100

90

80

70

60

50

40

30

20

10

0

Absorbance

Ab

so

rba

nce

(A)

% Transmission

% T

ran

sm

issio

n

Absorption - Lambert Beer´s Law IV

Absorbance Transmission

(CU) (%)

0 100

0,5 32

1 10

2 1

3 0,1

4 0,01

A = -log T

Absorption - Different Colors

0,0

0,1

0,2

0,3

0,4

350 400 450 500 550 600 650 700

Wellenlänge / Wavelength (nm)

Sig

na

l (C

U)

Gelb/Yellow

Rot/Red

Blau/Blue

Color Analysis, e.g. APHA

0

1

2

3

4

380 430 480 530 580

Ab

so

rba

nc

e

0,0

0,1

0,2

0,3

0,4

0,5

380 430 480 530 580

Ab

so

rban

ce

Wavelength (nm)

500 APHA

5 cm cuvette

50 APHA

5 cm cuvette

Color Analysis

Single BeamAbsorption:

Dual BeamAbsorption:

A = ε ·c · d

A = Ameas - Aref

Aref

Ameas

Color Analysis - Comparison Single

and Dual Beam

Single Beam Absorption:

• No Turbidity

• No Bubbles

• Significant color changes

Dual Beam Absorption:

• Compensation of turbidity

• Compensation of bubbles

• High sensitivity

• Compensation of lamp aging

Aref

Ameas

Color Intensity

Color Analysis - Typical Apps Single

and Dual BeamAref

Ameas

• Color dosage

• Quality control / Purity (absence of color)

• Decolorization control

• Color scales: APHA, Hazen, EBC, ASBC, ASTM, ICUMSA, Lovibond

• Concentration of inks / colorants

• Residual color in waste water

• Metals in solution: Iron, copper, nickel, chromium

• Huminic matter in drinking water

• Chlorophyll in edible oil

• Bleaching of edible oil, sugar syrup...

• Lignin in hydrosulforic acid

• Dissolved water in organics

• Phase separation: organic and aqueous phase

• Chlorine / chlorine dioxide / hypochlorite

• Phase separation:

- Beer / Water

- Wine / Water

- Juice / Water

- Hemoglobin

concentration in blood

Color Analyzer Manufacturers

• Ametek Process Instruments Model 4000

• Galvanic Applied Sciences Monitek Monispec AD

• Optek Model AF26

• Sigrist ColorPlus

• Wedgewood Analytical Model AF21, AF22

Ametek Model 4000

GAS Monitek Monispec AD

Optek Control 4000/AF26

Sigrist ColorPlus

Wedgewood Analytical

980/AF21,AF22