40 PRESERVATIVES
human non-enveloped viruses such as the human enteroviruses and rhinoviruses) than to enveloped viruses (herpes viruses, HIV and hepatitis B virus).11,12
Formulation guidelines When formulating, water-soluble preservatives should always be added to the water phase. Limited water-soluble preservatives should first be dissolved in a water-miscible solvent for addition to the water phase of a product formulation. Improper addition may affect the partitioning of an oil- and water-soluble preservative if added to the incorrect phase of an emulsion CPC shows good physical compatibility with most formulation ingredients, with a few exceptions. Among the synthetic polymer thickeners, most carbomer and acrylate- type varieties require special formulation guidance based on formulation type, such as homogenisation. Most cellulosic natural thickeners (e.g.
cationic guars and hydroxyethylcellulose) are compatible with CPC but so far, most vegetable gums (e.g. xanthan gum) appear to have issues with it, as do certain inorganics, such as clays. CPC is not compatible with magnesium aluminum silicate Many thickeners can be used with a pre-
mix of 40% CPC in propylene glycol, but some additional steps are required. The pre-mix of 40% CPC in propylene glycol must be solubilised prior to adding to the thickened gel at a 3:1 ratio. Suitable solubilisers are: ■ Polyoxyalkylene alkyl ether ■ PPG-5 ceteth-20 ■ Polysorbate-80 ■ Polysorbate-20 ■ PEG-40 castor oil Neutralise the polymer first, pre-blend the
CPC blend, then add solubilised CPC to the thickened, clear gel. It is suggested that the formulator should increase the pH 0.2 units above the polymer suppliers’ recommended specifications. This is shown in Figure 2, where the jar on the right shows that CPC can form white particulates if not formulated properly.
Deodorants CPC is effective at inhibiting growth and reducing the concentration of odour producing bacteria. When used in a soap-based product, it enhances the effect of odour reduction and, when used in an antiperspirant, it provides additional reduction of odour.
TABLE 3: DEODORANT ‘GEL STICK’ FORMULA Phase
INCI name A Water
Disodium EDTA Propylene Glycol Dipropylene Glycol
B C
Sodium Stearate, Vegetable Steareth-2
Cetylpyridinium Chloride (and) Propylene Glycol PEG-8
Perflourononylethyl Carboxydecyl PEG-10 Dimethicone PPG-5-Ceteth-20
PERSONAL CARE February 2022
Figure 2: Bacteria reduction in deodorant formulations As shown in Table 2, CPC achieved a 3-log
(>99.9%) reduction of bacteria at one, seven, 14, 21 and 28 days as measured by the PCPC method. Tables 3 and 4 show the formulations used in these tests.
Summary CPC is an effective antibacterial agent. In the US, it may be used as a preservative for use in many personal care products. It is applicable in a variety of formulations such as oral care, skin care, hair care, colour cosmetics and toiletries. CPC has activity against many microorganisms including gram-positive and gram-negative bacteria, yeast and mould. It shows good physical compatibility with most formulation ingredients, with a few exceptions.
References: 1 Sykes GA. Disinfection & sterilisation: Theory & practice. 1967. (2nd edition). Spon
2 Block SS. Disinfection, sterilisation & preservation. 2001. (5th edition). Lippincott, Williams & Wilkins
3 Bereswill S, Vey T, Kist, M. Federation of European Microbiological Societies Immunology & Medical Microbiology. 1999. 24:189-192.
4 Prince EL, Perez-Giraldo C, Morton
w/w % 18.02 0.10
60.00 10.00 4.25 1.25
0.38 2.00 2.00 2.00
Trade name
LHG. International biodeterioration & biodegradation. 1997. 39:1-7
5 Southwest Meat Association. Infomeat Newsletter, 22 May 2000: http://www.
southwestmeat.org/sma/newsletter.html
6 Gardener, JF, Peel MM. Introduction to sterilisation, disinfection & infection control 1991. (2nd edition) Churchill Livingstone
7 Broadley SJ, Furr JR, Russell, AD. Journal of Medical Microbiology. 1995. 43: 415-420
8 Russell, AD. The destruction of bacterial spores. 1982. Academic Press. 169-231
9 Loeberg RM, Hegna, IK. Pharm. Acta Helv. 1979. 54: 244-248
PC
10 Giuliana G, Pizzo G., Milici ME, Musotto GC, Giangreco, R. J. Periodontology. 1997. 68:729-733
11 Maillard, JY, Hann AC, Beggs TS, Day MJ, Hudson RA, Russell AD. Journal of Medical Microbiology. 1995. 42: 415-420.
12 Russell AD, Hugo WB, Aycliffe GAJ. (1999) Principles & practice of disinfection, preservation & sterilisation 1999. (3rd edition). Blackwell Science
13 Tattawasart U, Maillard JL, Furr JR, Russell AD. Int. J. Antimicrob. Agents. 2000. 16: 233- 238
14 Tattawasart U, Maillard JL, Furr JR, Russell AD. J. Appl. Microbiol. 1999. 87:323-331
TABLE 4: DEODORANT ‘WAFFLE TOP GEL’ FORMULA Phase A
INCI name
Deionised Water Ethyl Alcohol
Propylene Glycol PEG/PPG 8/3 Laurate
B C
Polyacrylate Crosspolymer-6
TEA (adjust pH to 6.0) Triethylamine PPG-5-Ceteth-20
Cetylpyridinium Chloride (and) Propylene Glycol
w/w % 65.74 25.00 3.00 2.50
2.50 q.s.
1.00 0.50
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