313ISSN 0326-2383

KEY WORDS: Emulsions, Griffin, HLB, Hydrophilic-Lipophilic Balance, Surfactants.*Author to whom correspondence shoud be addressed. E-mail: rcpasquali@yahoo.com

Latin American Journal of Pharmacy(formerly Acta Farmacéutica Bonaerense)

Lat. Am. J. Pharm. 28 (2): 313-7 (2009)

Note to the Editor

Received: January 13, 2009Accepted: January 17, 2009

The Studies on Hydrophilic-Lipophilic Balance (HLB): Sixty Yearsafter William C. Griffin’s Pioneer Work (1949-2009)

Ricardo C. PASQUALI *, Natalia SACCO & Carlos BREGNI

Cátedra de Farmacotecnia I, Departamento de Tecnología Farmacéutica,Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires,

Junín 956, 6° piso (1113) Buenos Aires, Argentina.

SUMMARY. The Hydrophilic-Lipophilic Balance (HLB)was formally presented by William C. Griffinsixty years ago at a meeting in Chicago for the first time and later on in an article published in the firstvolume of the Journal of the Society of Cosmetic Chemists. In later publications, Griffin proposed formu-las for the HLB value calculation that are satisfactory for non-ionic surfactants of various types. Severalexperimental methods developed then in order to obtain the HLB values of surfactants and required HLBof oils in a way simpler than with Griffin’s original experimental method. Also there were proposed math-ematical equations that HLB values of surfactants allows to calculate from its chemical formulae and alsofrom quality control data of surfactants and its components.

Short biography of W.C. GriffinWilliam C. Griffin was born in October 9,

1914, in Mount Pleasant, Pennsylvania, thirtymiles southeast of Pittsburgh. He graduatedfrom Pennsylvania State University in 1936 witha Bachelor of Science degree in Chemical Engi-neering. Upon graduation, he began to work atthe Atlas Powder Company, which later becamepart of Imperial Chemical Industries. Later, ICIgave the name of Uniqema to the surfactantsportion of the business and a few years latersold it to Croda, USA. In 1940 he was co-authorof a paper that proposed and demonstrated theutilization of electronic endpoint detection ofthe Karl Fisher endpoint for water analysis andthe method is still in practice. In 1949 his firstpaper on the use of the HLB system for emulsi-fier selection was published. In 1953 he wasawarded a Master of Science by Penn State Uni-versity based on a thesis detailing this work. Asecond paper on HLB was published in 1954.Heretired from ICI in 1979 after 43 years. Griffin re-ceived the 1999 Maison G. deNavarre Awardfrom the Society of Cosmetic Chemists in recog-

nition of the early HLB studies. In 2008, Crodadedicated a laboratory as the William C. GriffinInnovation Center (Fig. 1).

HLB History (by William C. Griffin)Atlas Powder Company, my first employer in

1936, manufactured and sold dynamite and alsothe blasting caps that were required to detonatethe dynamite. They were small copper tubesfilled with mercury fulminate with attachedwires to make them explode. They were sensi-tive to mechanical shock and if dropped theywould explode spreading shards of copper ev-erywhere.

Atlas learned of a person who had foundthat mannitol hexanitrate was an equally goodexplosive to detonate dynamite and that it wasdramatically safer. In fact, one could drive a nailthrough them without their exploding. He andAtlas got together and designed a new blastingcap based on mannitol hexanitrate.

Atlas decided to manufacture the caps and tomake mannitol for them. Mannitol is a sugar al-cohol. In the process, they produced four

314

PASQUALI R.C., SACCO N. & BREGNI C.

pounds of sorbitol for every pound of mannitol.Our small laboratory group, fewer than a dozen,had the task to find these markets.

Sorbitol was hygroscopic and a possible al-ternate for glycerin in many products. The fattyacid derivatives of sorbitol were also possible al-ternates for glycerol monostearate and the like.At the end of World War II one of our staff,Rudolph Maximilian Goepp, was a part of thescientific group that traveled to Germany to as-sess their scientific efforts. When he returned hesuggested that the sorbitan esters be reactedwith ethylene oxide. When this was done, theirproperties changed from oil soluble esters toproducts dispersible in or eve soluble in water.Here was a true opportunity for new productsthat were non-ionic and not dependant uponionic surfactants.

Since you could add one or five or twenty orfifty or more molecules of ethylene oxide toeach ester you suddenly had an infinite numberof products. We found that you could blend the

Figure 1. William C.Griffin with the president of Cro-da Inc., USA, in the inauguration of the William C.Griffin Innovation Center.

water soluble ones with the oil soluble onesand get the same effect as an in-between lengthof ethylene oxide, so the initial product lineconsisted of mono and tri esters with addedethylene oxide ranging from zero to twentymolecules.

The next question was how could one de-cide which product or products to use for thehundreds of different products that our potentialcustomers could produce? We soon found thatyou could determine the required HLB for theoils and waxes that were in the products. Like-wise, with a mixture of different oils and/orwaxes the required HLB for the blend could becalculated based on weight percentages.

Of course, at first we blended variousamounts of low and high HLB emulsifiers foreach product but soon we made an array of testemulsifiers with HLB values of 2, 4, 6, 8, 10, 12,14 and 16. These became our HLB Kit withwhich the approximate required HLB for ablend could be easily. Then with final blendingof high and low, the best HLB is easily deter-mined. Further, one will choose the composi-tion of the surfactants based on the desiredcharacteristics of the final product.

Our calculations of HLB at that time werecrude compared with today’s tools. It was basi-cally the percentage of the hydrophilic portionof the molecule multiplied by twenty. This in-cluded not only the ethylene oxide but also thesorbitan portion.

Suffice to say, today’s methods of determin-ing the HLB of a surfactant is so far beyond myimagination back on those days.

The Studies on Hydrophilic-LipophilicBalance (HLB)

The Hydrophilic-Lipophilic Balance (HLB)for emulsifier classification and selection wasfirst issued in 1948 in an Atlas Powder Compa-ny’s brochure 1. The following year, William C.Griffin, one of the company’s chemists, formallypresented the HLB concept at a meeting inChicago for the first time and later on in an arti-cle published in the first volume of the Journalof the Society of Cosmetic Chemists 2 (Fig. 2). Inthis innovative paper, Griffin explained someexperimental details for the determination of thenumerical HLB values of the emulsifiers and therequired HLB for oils. Griffin stated that HLBvalues for emulsifier mixtures and required HLBvalues for oil mixtures were obtained by apply-ing the additive property.

In later publications, Griffin 3,4 proposed for-

315

Latin American Journal of Pharmacy - 28 (2) - 2009

mulas for the HLB value calculation that are sat-isfactory for non-ionic surfactants of varioustypes. However, non-ionic surfactants contain-ing propylene oxide, butylene oxide, nitrogenor sulphur, exhibit a behavior which has notbeen related to their composition. For theseproducts, an experimental method must beused.

Greenwald et al. 5 proposed that the titrationby water of a dioxane-benzene solution of anoil or a surface active agent to a cloud endpoint can be used to determine a value relatedto the hydrophile-lipophile balance character ofthe oil or surface active agent.

Moore & Bell 6 introduced the H/L numbersfor non-ionic surfactants with polyoxyethylene.This number is defined as 100 by the quotientof the number of ethylene oxide units and thecarbon atoms number of the lipophilic moiety.Like HLB value, a high value of H/L number in-dicates that the surfactant is hydrophilic.

In a study about the coalescence rates ofemulsions, Davies 7 found that HLB values for

Figure 2. Facimilar copy ot the article “Classificationof surface-active agents by “HLB”, by William C. Grif-fin, published in the Journal of the Society of Cosmet-ic Chemists, vol. 1, pp. 311-26.

surface active agents can be consistently calcu-lated directly from the chemical formulae, usinggroup numbers. For surfactants with poly-oxyethylene as the sole hydrophilic moiety, theDavies scale differs substantially from the Griffinscale in the entire range of practical applications8.

Robbers & Bhatia 9 developed a techniquefor the rapid determination of HLB and re-quired-HLB values. In this method, a series ofemulsions are prepared which cover the rangeof HLB values between two stocks emulsions.The desired amounts of each stock emulsion areweighed into a 15 mL graduated centrifuge tubeto make a total of 10 g of mixed emulsion.Then, the tubes are centrifuged at 1500 rpm.The HLB value of the emulsifiers in the emul-sion showing the least separation is taken to beequal to the required HLB value.

Chun & Martin 10 developed an interfacialtension method for the evaluation of HLB valuesof water soluble surface-active agents. One-tenth percent aqueous solutions of surfactantwere overlayered with toluene and the interfa-cial tension were measured. A linear relation-ship resulted when the interfacial tension valueswere plotted again HLB values.

Huebner 11 developed a rapid method of de-termining relative polarity of surfactants. Thismethod is based on a comparison of the reten-tion times of methanol and n-hydrocarbonswhen a surfactant is used as the liquid phase ina gas-liquid chromatography column. Huebnerdefined the “polarity index”, a parameter relatedto the hydrophile-lipophile properties of thesurfactant tested. Based on the study of Huebn-er, Fineman12 founded a linear relationship be-tween polarity index and HLB value’s of surfac-tants formed by ethylene oxide adducts.

Gorman & Hall 13 founded a linear relation-ship with the log dielectric constant of surfac-tants and its HLB values. These authors alsofounded a linear relationship with the log di-electric constant and required HLB of oils.

Becher & Birkmeier 14 determined HLB val-ues by gas-liquid chromatography. The differentretention times of two liquids, one being polarand the other non-polar, allows for the mea-surement of the HLB value of a surfactant or amixture of surfactants, if used as a substrate, viagas-liquid chromatography.

The additively of HLB values of non-ionicemulsifiers and required HLB of oils was evalu-ated experimentally by Ohba 15,16 and Becher &Birkmeier 14.

316

PASQUALI R.C., SACCO N. & BREGNI C.

Shinoda 17 developed a phase inversion tem-perature (PIT) system for selecting an emulsifierand compared with the HLB-value system. TheHLB value of a nonionic surfactant changes withthe temperature and the inversion of an emul-sion type occurs at which these two propertiesjust balance.

Ben-Et & Tatarsky 18 determined HLB valuesfor various commercial nonionic surfactants bymeans of high resolution NMR. The results ob-tained are in good agreement with given HLBvalues. The method is rapid, nondestructive andrequires only small samples.

Little 19 proposed a mathematical relationshipbetween solubility parameter and the HLB val-ue, which was tested with anionic and non-ion-ic surfactants. This equation is not applicable forcationic surfactants.

Schott 20 compared the solubility parametersof various polyoxyethylated nonionic surfactantswith their HLB values. The compounds includedthree homologous surfactant series based on do-decanol, octylphenol, and fatty acid esters ofsorbitan, respectively, a polyoxyethylated sor-bitol ester, and a polyethylene glycol. Solubilityparameters were calculated by Schott from mea-sured heats of vaporization for the polyoxyethy-lated dodecanol series and from molar attractionconstants for all three surfactant series. Whenthe solubility parameter was corrected for hy-dration by including a hydrogen-bonding com-ponent, plots of HLB versus this new solubilityparameter were nearly linear and parallel for thethree series of surfactants, with slopes of 5.0 ±0.2. The three lines were spaced apart only 1.2(cal/cm3)1/2 despite structural differences amongthe surfactants, indicating that the chemical na-ture of the hydrocarbon moiety exerts only alimited effect on the solubility parameter.

In an interesting paper about the requiredhydrophilic-lipophilic balance for emulsification,Graciaa et al. 21 propose that the intrinsic stabili-ty or lack of stability of an emulsion depends on

the HLB number of the emulsifier present in theinterfacial regions separating oil from water.This HLB number is generally quite differentfrom the value assigned to the emulsifier systemblended with the oil and water to create theemulsion because some of the emulsifiermolecules will tend to dissolve into the oil andwater as well as be adsorbed at the interface.These authors proposed equations that permitto calculate the HLB number of the emulsifierpresent in the interfacial region. In this calcula-tions, the authors used incorrectly molar frac-tions instead of mass (or weight) fractions to ex-press the additively of the HLB values of thesurfactant mixtures (adducts with different quan-tities of ethylene oxide, for example). Moreover,the Poisson equation that expressed the distri-bution of ethylene oxide in adducts is incorrect-ly used 22.

Pasquali et al. 23 obtained a correlation be-tween the required HLB values and the solubili-ty parameters of oils, a more precise correlationbetween the required HLB values and the di-electric constant, than the one obtained by otherauthors; and new values of the required HLB foro/w emulsions of solid fatty acids and alcoholsfrom the values of the solubility parameters anddielectric constants, that could be more trustfulthan the ones obtained by the methodologybased in emulsion stability studies. Pasquali etal. 24 obtained equations that permit to calculatethe HLB value of polyoxyethylene esters fromquality control data of the raw materials (fattyacids and polyethylene glycol) and the finishedproduct (surfactant). These data are: acid valueof the fatty acid, hydroxyl value of the polyethy-lene glycol and hydroxyl value of the surfactant.These calculations permit, moreover, to knowthe mean molecular masses of fatty acids, ofpolyethylene glycol, of monoester and diester,and the proportion of polyoxyethylene mo-noester and polyoxyethylene diester.

REFERENCES

1. Atlas Powder Company (1948) “Surface ActiveAgents”. Atlas Powder Company, Wilmington,Delaware.

2. Griffin, W.C. (1949) J. Soc. Cosmet. Chem. 1:311-26.

3. Griffin,W.C. (1954) J. Soc. Cosmet. Chem. 5:249-56.

4. Griffin, W.C. (1955) Am. Perf. Essent. Oil Rev.May 1955: 26-9.

5. Greenwald, H. L., G. L. Brown & M. N. Fine-man (1956) Anal. Chem. 28: 1693-7.

6. Moore, C. D. & M. Bell (1956) Soap, Perf.Cosm. 29: 893-6.

7. Davies, J. T. (1957) “A quantitative kinetic the-ory of emulsion type. I. Physical chemistry ofthe emulsifying agent. Gas/Liquid andLiquid/Liquid Interfaces”. Proceedings of 2ndInternational Congress Surface Activity, Butter-worths, London, pp. 426-38.

317

Latin American Journal of Pharmacy - 28 (2) - 2009

8. Schott, H. (1989) J. Colloid Interface Sci. 133:527-9.

9. Robbers, J. E. & V. N. Bhatia (1961) J. Pharm.Sci. 50: 708-9.

10. Chun, A. H. C. & A. N. Martin (1961) J. Pharm.Sci. 50: 732-6.

11. Huebner, V. H., (1962) Anal. Chem. 34: 488-91.

12. Fineman, I. G. A. (1969) J. Am. Oil Chem. 46:296-8.

13. Gorman, W. G. & G. D. Hall (1963) J. Pharm.Sci. 52: 442-6.

14. Becher, P. & R. L. Birkmeier (1964) J. Am. OilChem. 41: 169-72.

15. Ohba, N. (1962) Bull. Chem. Soc. Japan 35:1016-20.

16. Ohba, N. (1962) Bull. Chem. Soc. Japan 35:1021-5.

17. Shinoda, K. (1969) “The comparison betweenthe PIT system and the HLB-value system toemulsifier selection”. Proceedings of the 5th In-ternational Congress of Surface Activity,Barcelona, Spain. Vol. 2, pp. 275-83.

18. Ben-Et, G. & D. Tatarsky (1972) J. Am. OilChem. 49: 499-500.

19. Little, R.C. (1978) Colloid Interface Sci. 65: 587-8.

20. Schott, H. (1984) J. Pharm. Sci. 73: 790-2. 21. Graciaa, A., J. Lachaise, G. Marion & R.S.

Schechter (1989) Langmuir 5: 1315-8.22. Pasquali, R. C., J. C. López, N. Sacco & C.

Bregni (2009) J. Disp. Sci. Tech. 30 in press.23. Pasquali, R. C., C. Bregni & M. Taurozzi (2009)

J. Disp. Sci. Tech. 30: 328-31.24. Pasquali, R. C., N. Sacco & C. Bregni (2010) J.

Disp. Sci. Tech. 31 in press.