Measurement and Application of Equivalent Alkane Carbon Number of Fragrance Oils

AOCS Meeting – May, 2014D.R. Scheuing, Erika Szekeres Clorox

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

The Good News -

Chemically Complex Modern Fragrances Drive Consumer Preference

The Bad News -

Chemically Complex Modern Fragrances Drive Consumer Preference

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 LevelsOne Answer = 4 Different FormulationsAnother 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

Classic Fish Diagram Shows the Formulation Problem – in terms of Temperature

Surfactant concentration

Tem

pe

ratu

re

w/o micelle+

excess water

o/w micelle+

excess oil

bicontinuous3 phase

Single phase

w

oil

oil

oil

water

w

oil

Product

Non-ionic surfactant

HLD View of the Problem – What is the Range of Fragrance HLD?

Surfactant concentration

HL

D

(oil

po

lari

ty)

2 phase

2 phase

3 phase

Polar fragrance oil

Hydrophobic fragrance oil

Single phase

(-)

(+)

𝑪𝒔

HLD = hydrophilic-lipophilic differenceVaried via oil polarity variation

A Wider Range of Fragrance HLD Requires Higher Concentration of a Given Surfactant – Costs Are Increased

Surfactant concentration

HL

D

(oil

po

lari

ty)

2 phase

2 phase

3 phase Single phase

(-)

(+)

𝑪𝒔 𝑪𝒔

Hydrophobic fragrance oil

Polar fragrance oil

Even Worse for Cost – Selection of the Wrong Surfactant Package for the Range of Fragrances

Surfactant concentration

HL

D

(oil

po

lari

ty)

2 phase

2 phase

3 phase

Single phase

(-)

(+)

𝑪𝒔 𝑪𝒔

Surfactant is too hydrophobic for this range of HLD – Higher Concentration Required

Polar fragrance oil

Hydrophobic fragrance oil

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−𝑎𝑇 ∙ (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 achievedHLD = 0

Calculate EACN

𝐸𝐴𝐶𝑁=ln (𝑆∗ )+𝐶𝑐

𝑘

Salt scan on the SOW phase map

Surfactant concentration, wt%

Na

Cl w

t%

w/o micelle+

excess water

o/w micelle+

excess oil

bicontinuous

3 phase

Single phase

HLD =0S*

Anionic surfactant

Salt scan in the test tubes with SDHS surfactant and Limonene

2.687

3.714

4.740

5.718

6.744

7.770

8.797

9.823

10.850

11.827

12.854

13.880

0%10%20%30%40%50%60%70%80%90%

100%

Relative phase volumes

Excess water Microemulsion Excess oil

aq. NaCl %R

ela

tiv

e p

ha

se

vo

lum

e

2 3 4 5 6 7 8 9 10 11 12 13 140

1

2

3

4

5

Volume of oil and water in the mi-croemulsion phase

WaterOIL

NaCl %

Vo

lum

e, m

l

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

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

Salt scan with fragrance/limonene mixture

2 3 4 5 6 7 8 9 10 11 12 13 140

0.51

1.52

2.53

3.54

4.55

Volume of oil and water in the microemulsion phase

NaCl %V

olu

me

, ml

2.687

3.714

4.740

5.718

6.744

7.770

8.797

9.823

10.850

11.827

12.854

13.880

0%10%20%30%40%50%60%70%80%90%

100%

Relative phase volumes

Excess water Microemulsion Excess oil

aq. NaCl t%

Re

lati

ve

ph

as

e v

olu

me

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

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

Calculated fragrance EACN depends on mixing ratio !

Oil mixture EACN is a nonlinear function of mixing ratio

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-4

-2

0

2

4

6

8

Limonene + fragrance oil mixture, 10% SDHS, salinity scan using NaCl

Fragrance oil volume fraction

EACN

of o

il m

ixtu

re

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-14

-12

-10

-8

-6

-4

-2

0

EACN of fragrance oil calculated using linear mixing rule

Fragrance oil volume fraction

EACN

of p

ure

frag

ranc

e

Stick to a fixed 0.2 volume fraction for all EACN measurements

Measured EACN of Fragrances and Solvents

-14 -12 -11 -10 -9 -8 -6 -5 -4 -3 0 1 50

1

2

3

4

5

6

7

8

9

10

Typical fragrance EACN values

Fragrance EACN value

Fre

qu

en

cy

solvent 1 solvent 2 solvent 3 solvent 4 solvent 5-28

-26

-24

-22

-20

-18

-16

-14

-12

-10

Solvent EACN values

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

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

Thanks !

AOCS – S&D Division

Clorox

And –

You – The Audience and Consumer !

References

The EACN scale for oil classification revisited thanks to fish diagramsJournal of Colloid and Interface Science 312 (2007) 98–107S. Queste, J.L. Salager, R. Strey, J.M. Aubry

Classification of terpene oils using the fish diagrams and the EquivalentAlkane Carbon (EACN) scaleColloids and Surfaces A: Physicochem. Eng. Aspects 338 (2009) 142–147Francois 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 MicroemulsionsLangmuir 2004, 20, 6560-6569 Erika Szekeres, Edgar Acosta, David A. Sabatini, Jeffrey H. Harwell