Measurement and Application of Equivalent Alkane Carbon Number of Fragrance Oils AOCS Meeting – May, 2014 D.R. Scheuing, Erika Szekeres Clorox
Measurement and Application of Equivalent Alkane Carbon Number of Fragrance Oils
AOCS Meeting – May, 2014 D.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
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
Classic Fish Diagram Shows the Formulation Problem – in terms of Temperature
Surfactant concentration
Tem
pera
ture
w/o micelle +
excess water
o/w micelle +
excess oil
bicontinuous 3 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
HLD
(o
il po
larit
y)
2 phase
2 phase
3 phase
Polar fragrance oil
Hydrophobic fragrance oil
Single phase
(-)
(+)
𝑪𝒔
HLD = hydrophilic-lipophilic difference Varied via oil polarity variation
A Wider Range of Fragrance HLD Requires Higher Concentration of a Given Surfactant – Costs Are Increased
Surfactant concentration
HLD
(o
il po
larit
y)
2 phase
2 phase
3 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
HLD
(o
il po
larit
y)
2 phase
2 phase
3 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 ∙ 𝑬𝑬𝑪𝑬 + 𝐶𝑐
𝐻𝐻𝐻 = ln 𝑆 − 𝑘 ∙ 𝑬𝑬𝑪𝑬 + 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 achieved HLD = 0
Calculate EACN
𝐸𝐴𝐶𝐸 =ln 𝑆∗ + 𝐶𝑐
𝑘
Salt scan on the SOW phase map
Surfactant concentration, wt%
NaC
l wt%
w/o micelle +
excess water
o/w micelle +
excess oil
HLD =0
S*
Anionic surfactant
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 13.9Rel
ativ
e ph
ase
volu
me
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
Volu
me,
ml
NaCl %
Volume of oil and water in the microemulsion phase
WaterOIL
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
00.5
11.5
22.5
33.5
44.5
5
2 3 4 5 6 7 8 9 10 11 12 13 14
Volu
me,
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
Rel
ativ
e ph
ase
volu
me
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
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
-4-3-2-101234567
0 0.2 0.4 0.6 0.8 1
EACN
of o
il m
ixtu
re
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
EACN
of p
ure
frag
ranc
e
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
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
Freq
uenc
y
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
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
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