This document introduces a method for measuring the equivalent alkane carbon number (EACN) of fragrance oils to rank their polarity. Ranking fragrance polarity helps optimize formulations by accounting for the range of hydrophilic-lipophilic differences between fragrances. The method involves measuring the salinity at which microemulsions form for mixtures of each fragrance oil and limonene. From these measurements, the EACN of the mixtures and limonene alone are used to calculate the individual fragrance EACNs via a linear mixing rule. This practical approach allows for rapid formulation optimization across a range of fragrance polarities.

1. Measurement and Application of Equivalent
Alkane Carbon Number of Fragrance Oils
AOCS Meeting – May, 2014
D.R. Scheuing, Erika Szekeres
Clorox

2. Outline
Introduce the Fragrance Problem
Relate the Problem to Hydrophilic-Lipophilic
Difference (HLD) and Equivalent Alkane Carbon
Number (EACN)
Introduce a Practical Approach to the Problem
Example and Watch-Outs

3. The Good News -
Chemically Complex Modern
Fragrances Drive Consumer
Preference

4. The Bad News -
Chemically Complex Modern
Fragrances Drive Consumer
Preference

5. Multiple Fragrances Needed !
Lemon
1.5% Surfactant
Lavender
1.7% Surfactant
Watery Fresh
1.2% Surfactant
Spring Blooms
1.3% Surfactant
4 Fragrances Need 4 Different Minimum Surfactant Levels
One Answer = 4 Different Formulations
Another Answer = Use 1.7% Surfactant For All
Or –
Rank the Fragrances in Terms of Polarity with a Simple Method
Design One Robust Formulation for All Fragrances
Understand that Wide Range in Polarities Will Drive Costs

6. Classic Fish Diagram Shows the Formulation Problem
– in terms of Temperature
Surfactant concentration
Temperature
w/o micelle
+
excess water
o/w micelle
+
excess oil
bicontinuous
3 phase
w
oil
oil
oil
water
w
oil
Product
Non-ionic surfactant

7. HLD View of the Problem – What is the Range of
Fragrance HLD?
Surfactant concentration
HLD
(oilpolarity)
2 phase
2 phase
3 phase
Polar
fragrance oil
Hydrophobic
fragrance oil
Single phase
(-)
(+)
𝑪 𝒔
HLD = hydrophilic-lipophilic difference
Varied via oil polarity variation

8. A Wider Range of Fragrance HLD Requires Higher Concentration
of a Given Surfactant – Costs Are Increased
Surfactant concentration
HLD
(oilpolarity)
2 phase
2 phase
3 phase
(-)
(+)
𝑪 𝒔 𝑪 𝒔
Hydrophobic
fragrance oil
Polar
fragrance oil

9. Even Worse for Cost – Selection of the Wrong Surfactant
Package for the Range of Fragrances
Surfactant concentration
HLD
(oilpolarity)
2 phase
2 phase
3 phase
(-)
(+)
𝑪 𝒔 𝑪 𝒔
Surfactant is too hydrophobic for this range of HLD – Higher Concentration Required
Polar
fragrance oil
Hydrophobic
fragrance oil

10. Rank Fragrance Oil Polarities Via EACN Measurement
Use the HLD equation for anionic surfactant
0 = ln 𝑺∗
− 𝑘 ∙ 𝑬𝑨𝑪𝑵 + 𝐶𝑐
𝐻𝐿𝐷 = ln 𝑆 − 𝑘 ∙ 𝑬𝑨𝑪𝑵 + 𝐶𝑐 − 𝑎 𝑇 ∙ 𝑇 − 25 + 𝑓(𝐴)
HLD (reflects overall formulation hydrophobicity):
• Electrolyte (S) – vary this experimentally
• Oil polarity (EACN) - unknown
• Surfactant head/tail (k and Cc) – these are known
• Temperature (T) – fix this at 25C
• Alcohol – f(A) don’t add alcohol
Experimentally determine S* at which optimum formulation is achieved
HLD = 0
Calculate EACN
𝐸𝐴𝐶𝑁 =
ln 𝑆∗
+ 𝐶𝑐
𝑘

11. Salt scan on the SOW phase map
Surfactant concentration, wt%
NaClwt%
w/o micelle
+
excess water
o/w micelle
+
excess oil
HLD =0S*
Anionic surfactant

12. Salt scan in the test tubes
with SDHS surfactant and Limonene
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
2.7 3.7 4.7 5.7 6.7 7.8 8.8 9.8 10.8 11.8 12.9 13.9
Relativephasevolume aq. NaCl %
Relative phase volumes
Excess water Microemulsion Excess oil
0
1
2
3
4
5
2 3 4 5 6 7 8 9 10 11 12 13 14
Volume,ml
NaCl %
Volume of oil and water in the
microemulsion phase
Water
OIL
S*
S* = 7% EACN = 6.05
The more positive the
EACN the
more hydrophobic the oil
SDHS= sodium
dihexyl
sulfosuccinate
Water/oil
volume ratio = 1

13. Adaptation to Fragrance Oil Ranking
Problem
• Fragrance oils are quite polar
• The Winsor I-III-II phase sequence might be impossible to find
Solution
• Run salt scan with fragrance oil/limonene mixture rather than with
pure fragrance oil and determine the EACN of the oil mixture;
• Run a limonene salt scan control to determine limonene EACN
• Use linear mixing rule by volume to calculate fragrance oil EACN from
oil mixture EACN and limonene EACN data

14. Salt scan with fragrance/limonene mixture
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
2 3 4 5 6 7 8 9 10 11 12 13 14
Volume,ml
NaCl %
Volume of oil and water in the microemulsion
phase
W…
O…
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
2.69 3.71 4.74 5.72 6.74 7.77 8.80 9.82 10.8511.8312.8513.88
Relativephasevolume
aq. NaCl t%
Relative phase volumes
Excess water Microemulsion Excess oil
S* oil mixture = 4.8%
EACN fragrance = - 5.05
S* mix  calculate EACN mix using HLD  calculate EACN fragrance with linear mixing rule
Oil mixture = 0.2 vol fraction
fragrance/limonene mixture

15. Watch-outs
Limonene oxidation – polar shift possible
Run SDHS +limonene control scan
SDHS solution from Aldrich seems reproducible
Ester hydrolysis/residual alcohol ?
Room temperature is usually good enough
Use water/oil ratio = 1
Always add fragrance oil at 0.2 volume fraction

16. Calculated fragrance EACN depends on mixing ratio !
Oil mixture EACN is a nonlinear
function of mixing ratio
-4
-3
-2
-1
0
1
2
3
4
5
6
7
0 0.2 0.4 0.6 0.8 1
EACNofoilmixture
Fragrance oil volume fraction
Limonene + fragrance oil mixture, 10% SDHS,
salinity scan using NaCl
-14
-12
-10
-8
-6
-4
-2
0
0 0.2 0.4 0.6 0.8 1
EACNofpurefragrance
Fragrance oil volume fraction
EACN of fragrance oil calculated using linear mixing rule
Stick to a fixed 0.2 volume fraction
for all EACN measurements

17. Measured EACN of Fragrances and Solvents
0
1
2
3
4
5
6
7
8
9
10
-14 -12 -11 -10 -9 -8 -6 -5 -4 -3 0 1 5
Frequency
Fragrance EACN value
Typical fragrance EACN values
-28
-26
-24
-22
-20
-18
-16
-14
-12
-10
solvent 1 solvent 2 solvent 3 solvent 4 solvent 5
Solvent EACN values

18. Example - Individual Fragrance Components
Nerol – 97% from Acros
EACN measured with current
approach = -21.9
Linalool – 97% from Acros
EACN measured with current
approach = -14.5
Empirical Formula = C10H18O

19. Summary
Complex Modern Fragrances Exhibit a Wide Range of Polarity
Formulation Costs Can Be Driven By Range of Polarity –
Equivalent to a Range in HLD
Ranking of Fragrance Polarities Via EACN Drives Rapid
Formulation Optimization
Simple Approach – Measure EACN of Limonene/Fragrance Oil
Mixtures to Rank Fragrances
Rankings Will Be Correct – Even if the Measured EACNs are
Not the Real Ones
Approach Is Practical – And Could Drive Inter-Lab Collaboration

20. Thanks !
AOCS – S&D Division
Clorox
And –
You – The Audience and Consumer !

21. References
The EACN scale for oil classification revisited thanks to fish diagrams
Journal of Colloid and Interface Science 312 (2007) 98–107
S. Queste, J.L. Salager, R. Strey, J.M. Aubry
Classification of terpene oils using the fish diagrams and the Equivalent
Alkane Carbon (EACN) scale
Colloids and Surfaces A: Physicochem. Eng. Aspects 338 (2009) 142–147
Francois Bouton, Morgan Durand, Véronique Nardello-Rataj, Marie Serry,
Jean-Marie Aubry
A Two-State Model for Selective Solubilization of Benzene-Limonene Mixtures in
Sodium Dihexyl Sulfosuccinate Microemulsions
Langmuir 2004, 20, 6560-6569 Erika Szekeres, Edgar Acosta, David A.
Sabatini, Jeffrey H. Harwell