Analysis of Coloring agents

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Analysis of Coloring agents in Drugs & Cosmetics: 

Analysis of Coloring agents in Drugs & Cosmetics Prafulla Kumar Sahu Alliance Institute of advanced Pharmaceutical and Health Sciences 1

Coloring agents: 

Coloring agents Coloring agents are used mainly to impart a distinctive appearance to a pharmaceutical dosage form. The main categories of dosage form that are colored are: Tablets: either the core itself or the coating. Hard or soft gelatin capsules: the capsule shell or coated beads. Oral liquids . Topical creams and ointments . 2


Applications Color is a useful tool to help identify a product in its manufacturing and distribution stages. Patients, especially those using multiple products , often rely on color to be able to recognize the prescribed medication. The use of different colors for different strengths of the same drug can also help eliminate errors . Many drug products look similar; hence color in combination with shape and/or an embossed or printed logo can help with identification . Unattractive medication can be made more acceptable to the patient by the use of color, and color can also be used to make a preparation more uniform when an ingredient in the formulation has itself a variable appearance from batch to batch . Some of the insoluble colors or pigments have the additional benefit when used in tablet coatings or gelatin shells of providing useful opacity, which can contribute to the stability of light-sensitive active materials in the tablet or capsule formulation. Pigments such as the iron oxides, titanium dioxide, and some of the aluminum lakes are especially useful for this purpose. 3


Classifications There are many possible classifications of coloring agents: Soluble In Water (Dyes): Colors for clear liquid preparations Insoluble In Water (Pigments): for coating of tablets, the choice of color is usually restricted to insoluble pigments. The reasons for this include their lack of color migration, greater opacity, and enhanced color stability over water-soluble colors. Lakes: are largely water-insoluble forms of the common synthetic water-soluble dyes. They are prepared by adsorbing a sodium or potassium salt of a dye onto a very fine substrate of hydrated alumina, followed by treatment with a further soluble aluminum salt. The lake is then purified and dried. Lakes are frequently used in coloring tablet coatings since, for this purpose, they have the general advantages of pigments over water-soluble colors. 4

Schematic classification of colouring agents: 

Schematic classification of colouring agents 5

Colorants for Cosmetics: 

Colorants for Cosmetics 6

Hydrosoluble colorants: 

Hydrosoluble colorants These colorants are used to colour mixtures in lotions, perfumes, emulsions, soaps and bath products, where a covering effect is not necessary. These are molecules which contain one or more water-soluble groups such as sulfonic (SO3 Na+) or carboxylic ( COONa +) moieties. These colorants are very sensitive to pH, UV rays, as well as to oxidative or reductor chemicals. Examples: Carminic acid, caramel, FD&C Yellow No. 5, FD&C Blue No. 1, D&C Orange No. 4, D&C Red No. 33, FD&C Red No. 40. 7

Liposoluble colorants: 

Liposoluble colorants These colorants are used to colour anhydrous mixtures where concealing is not necessary (e.g. tanning oils, bath oils, sticks, etc.). These molecules do not contain water-soluble groups and their stability in oil rarely goes beyond a few grams per litre . They are also sensitive to UV radiation. Examples: Carotene, D&C Red No. 17, D&C Yellow No. 11, D&C Green No. 6 and D&C Orange No. 5. 8


PIGMENTS Mineral pigments Organic pigments 9

Mineral pigments: 

Mineral pigments Mineral pigments are more resistant to light than organic colorants and they are also more opaque but less shiny. Examples: Iron oxides, which offer excellent stability and are the most widely mineral pigments in make-up. There are three basic shades of iron oxides: yellow (which corresponds to hydrated ferrous oxide, i.e. FeO · nH2O), red (which is attributed to ferric oxide, i.e. Fe2O3) and black (which is a mixture of both iron oxides). Chromium oxides are also employed in decorative cosmetics. Chromium oxide greens (Cr2O3) and chromium hydroxide greens (Cr2O3 · 2H2O) are typical mineral pigments with excellent light fastness, heat stability and bleed resistance. They also offer a high covering capacity, but their colour-giving power is weak. 10

Mineral pigments: 

Another class of pigments is the so-called ultramarines, which have a range of shades including green, pink and blue. They are synthetic pigments composed of complex sodium aluminium sulfosilicates . They are very stable to heat and pH alkaline, but not very stable in acid surroundings. Another inorganic pigment is Manganese Violet, which is a very bright colour. Chemically it is MnNH4P2O7. It is very stable to light and organic solvents. Titanium dioxide (TiO2) is a white pigment, with high coverage that offers excellent stability to heat and light. It is probably the most frequently used white pigment. Mineral pigments 11

Organic pigments: 

Organic pigments There are three types of organic pigments: Lakes Toners True Pigments 12


Lakes Lakes are water-soluble dyes that are absorbed into insoluble substrates by means of Vander Waals forces. They give dazzling shades although they have moderate covering capacity. Their stability is weak in the face of light and chemical agents; however, they offer good heat stability. These pigments are widely used in lipsticks and nail lacquers. When used, the preparation procedure is attained by absorption of a hydrosoluble colorant on an insoluble substrate. The most commonly used substrates are hydrated aluminium , titanium dioxide and aluminium benzoate, among others. 13

Toners : 

Toners They are water-soluble dyes that are precipitated as metal salts. They differ from lakes, where there is absorption on a substrate. The most used metals are calcium and barium. 14

True pigments: 

True pigments True pigments are pigments that based on their chemistry, precipitate back to they are made from. They are insoluble compounds which contain no metal ions. Examples: D&C Red No. 36 and D&C Red No. 30. 15

Pearlescents : 

Pearlescents A pearl effect can also be obtained by using appropriate pigments. They are the so called pearlescents . Pearlescent pigments reflect and transmit light by their transparency. The pearlescent effect of a pigment is obtained by super positioning plates of transparent material and different refractive indexes. This structure allows the reflection of part of the incident light and transmits the remainder to the plates below. Example: bismuth oxychloride ( BiOCl ), which is a synthetic pearlescent in the form of octagonal platelets giving a very shiny metallic pearlescent effect. It offers strong covering effects and good adhesion to skin surface. It is soft and silky to the touch. However, due to its poor stability to light, it has a tendency to darken after prolonged exposure. 16

Interferential pigments: 

Interferential pigments Mica also has pearlescent properties. It gives a pearly aspect to skin, because it has a refractive index which is different to that of air. A new generation of pearlescent pigments appeared when refined (micronized) mica dust was coated with highly refringent substances such as titanium dioxide and iron oxides. These are called interferential pigments. 17

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For surface coloring only 18

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The lake is not permitted in medicinal products 20

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Related Substances: 

Related Substances Beta-carotene; indigo carmine; iron oxides; sunset yellow FCF; tartrazine; titanium dioxide. 22

Analytical methods for determining colouring agent components: 

Analytical methods for determining colouring agent components Analytical methods are continuously developed in order to implement FDA’s colour additive batch certification program. These methods are used to enforce the limiting specifications for subsidiary colours , intermediates and side-reaction impurities listed in 21 CFR Parts 74 and 82. Some of the methods have been presented in detail by Leatherman et al. (1977) and Marmion (1991). New technologies have been developed, analytical instrumentation has been improved, and, as a result, some of the described methods have been replaced. Some modern analytical techniques applicable to synthetic colour additives also have been described (Peters and Freeman, 1995). 23

Inorganic components: 

Inorganic components Triphenylmethane dyes are generally prepared in two steps: a condensation reaction that results in a colourless intermediate, a leuco base; and an oxidation reaction of the leuco base, resulting in the coloured material (Fierz-David and Blangey, 1949). The oxidizing agents used for the second step are typically manganese dioxide or a dichromate salt. Because traces of manganese and chromium may remain in the final product, specifications that limit the amount of these metals in the triphenylmethane colour additives are listed in the CFR. Two new methods based on X-ray fluorescence were developed for the determination of chromium (Hepp, 1996) and manganese (Hepp, 1998) in FD&C Blue No. 1 (CI 42090). The analyses are completely automated, require about 5 min per element, and can be performed in conjunction with lead and arsenic determinations in the same sample portion. Mercury (calculated as elemental mercury) is limited to “not more than 1 part per million” in most certifiable colour additives listed in the CFR. 24

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A new method was developed that uses microwave digestion of the sample prior to the determination of mercury in colour additives by cold-vapor atomic absorption spectrometry (Hepp et al., 2001). That method was later modified and extended to the determination of mercury in the recently approved colour additive D&C Black No. 2 (CI 77266) (Hepp, 2006), listed in 21 CFR Part 74 in 2005. It should be noted that this method of mercury determination cannot be applied to colour additives that contain iodine , such as FD&C Red No. 3 (CI 45430), D&C Orange No. 10 (CI 45425:1) and D&C Orange No. 11 (CI 45425), because digestion produces iodine, which penetrates Teflon tubing and subsequently binds mercury (Hepp et al., 2001). CFR specifications for most certifiable colour additives limit arsenic (calculated as elemental arsenic) to “not more than 3 parts per million”. A new method was developed that uses dry ashing followed by hydride-generation atomic absorption for the determination of arsenic at levels well below the specified limit (Hepp, 1999). That method has become the preferred one when quantification of arsenic is needed in certifiable colour additives. 25

Organic components: 

Organic components A capillary-electrophoresis (CE) method was developed for the determination of the main component and two subsidiary colours in FD&C Red No. 3 (CI 45430) (Evans III, 2003). The reference materials used for that method, 2,4,5-triiodofluorescein, 2,4,7-triiodofluorescein, and 2,4,5,7-tetraiodofluorescein, were obtained by pH zone- refining (Weisz et al., 1994b). 26

LC method: 

LC method An LC method was developed for the determination of the intermediates (2-chloro-4- nitroaniline and 2-naphthol) and an impurity (2,4-dinitroaniline) in the monoazo colouring agent D&C Red No. 36 (CI 12085) (Table 4.2.2) ( Scher and Adamo , 1993). An impurity found by LC in the monoazo colouring agent FD&C Red No. 40 (CI 16035) (Table 4.2.2) was identified by gas chromatography (GC) coupled with a mass spectrometry (MS) detector as 4-nitro- p-cresidine (2-methoxy-5-methyl-4-nitrobenzenamine) (Richfield- Fratz et al., 1989). This impurity was found in all 28 certified batches of dye analyzed. This newly found impurity and other aromatic amines ( p- cresidine and aniline) were quantified at parts per billion ( μg /kg) levels in the colouring agent using an LC method . 27

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Analytical methods were developed to determine, at μg /kg levels, the total quantity of benzidine (free aromatic amine and combined forms) in the colouring agents FD&C Yellow No. 5 (CI 19140) (Davis and Bailey, 1993; Prival et al., 1993) and FD&C Yellow No. 6 (CI 15985) ( Peiperl et al., 1995). These methods have several components in common: the reduction (with sodium dithionite) of any combined benzidine present in the colour additive as azo and/or disazo dyes, to free benzidine ; an extraction step and diazotization and coupling with pyrazolone -T (for FD&C Yellow No. 5) or with 2-naphthol-3,6-disulfonate (for FD&C Yellow No. 6), followed by LC analysis of the coupling product. 28

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Various techniques were used for the determination of impurities (not specified in the CFR) in the colour additives D&C Red Nos. 21 and 27 (CI 45380:2 and CI 45410:1, respectively) (Table 4.2.5) and D&C Red Nos. 22 and 28 (CI 45380 and CI 45410, respectively). Thus, solid-phase microextraction (SPME) combined with gas chromatography- mass spectrometry (GC-MS) was used to determine 2,4,6-tribromoaniline (TBA) in D&C Red Nos. 21 and 22 ( Weisz et al., 2004), and hexachlorobenzene (HCB) and 2-bromo-3,4,5,6-tetrachloroaniline (2BTCA) in D&C Red Nos. 27 and 28 ( Andrzejewski and Weisz , 1999 and Weisz and Andrzejewski , 2003, respectively). LC methods were used to quantify 1-carboxy-5,7-dibromo-6-hydroxy-2,3,4-trichloroxanthone (HXCA) ( Weisz , 1997) and the decarboxylated analog of tetrabromotetrachlorofluorescein (BCPX) ( Weisz et al., 2006) in D&C Red Nos. 27 and 28. 29

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A method was developed that uses thin-layer chromatography (TLC) to separate colour components (specified in 21 CFR 74.1327 and 74.1328) in D&C Red Nos. 27 and 28 and then uses videodensitometry to quantify them (Wright et al., 1997). Thus, the TLC videodensitometry method has been developed for the in situ quantification of lower halogenated subsidiary colours (such as the 2,4,5-tribromo derivative) or of the ethyl ester of the main component (the 2,4,5,7-tetrabromo derivative) in multiple dye samples on the same analytical TLC plate. The total time for the analysis of five standards and four samples applied to each plate is at most 45 min. This technique replaced the classic method of quantifying the amount of dye in a spot/band by scraping the spot/band from the plate, dissolving the dye in a solvent, and analyzing the solution using ultraviolet/visible spectrophotomety (UV/VIS) . 30

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An LC method has been developed for the quantification of 2,4,6-triiodoresorcinol (I3R) and other specified intermediates and side-reaction products in the colouring agent FD&C Red No. 3 (CI 45430) (Mai et al., 2006). 178 4. Analytical Methods LC methods have also been developed for the identification and quantification of subsidiary colours in triphenylmethane colouring agents . Specifically, Matsufuji et al. (1998) determined five subsidiary colours in Brilliant Blue FCF (CI 42090), certifiable as FD&C Blue No. 1, and Tsuji et al. (2006) determined subsidiary colours in Fast Green FCF (CI 42053), certifiable as FD&C Green No. 3. The latter study compared TLC-UV/VIS and LC methods and recommended the LC method for the quantification of the subsidiary colours in Fast Green FCF. MS was shown to be a useful technique in structural assignment of isomeric mono- and disulfonic acid components of the colouring agent Quinoline Yellow (CI 47005) ( Weisz et al., 2001, 2002). Quinoline Yellow may or may not be certifiable in the U.S. (as D&C Yellow No 10) depending on the proportion of these components. 31

Thin-layer chromatography: 

Thin-layer chromatography TLC is one of the most common techniques of separating the multiple dyes within a mixture from each other (Touchstone, 1992; Gupta, 2003). Silica gel is the most widely used adsorbent , followed by alumina and microcrystalline cellulose . After the dye solution is spotted or streaked , the TLC plate is developed with a suitable solvent system and then it is dried . Next, the separated dye bands are individually removed by scraping and the dyes are extracted from the adsorbent in a solvent. Finally, they are identified and quantified spectrophotometrically . The use of TLC was described for the separation of synthetic dyes (Wall, 2000; Cserhati and Forgacs, 2001a; Gupta, 2003) and natural pigments (Pothier, 1996; Cserhati and Forgacs, 2001b; Francis and Andersen, 2003). 32

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As applied to cosmetic products, TLC was used primarily for the separation of colouring agents present in lipsticks . Thus, Silk (1965) developed a method whereby 15 colouring agents used in lipsticks were analyzed without the need for a preliminary cleanup because the lipstick was directly applied to a warm silica gel TLC plate. The colouring agents were separated in two steps : Elution with methylene chloride brings the fats and oils to the top of the plate and enables separation of the oil-soluble dyes and leaves the water-soluble dyes and the pigments at the origin; Then the water-soluble dyes were separated from each other by elution with ethyl acetate:methanol:8.7% ammonium hydroxide (15:3:3). The separated colour bands were removed by scraping, and the dyes were extracted from the silica gel in a solvent and identified/quantified by UV/VIS. This method was also applied to the analysis of dyes in nail polishes and blushers (Leatherman et al., 1977). 34

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By modifying the solvent systems used to develop the TLC plate, the method was extended to the separation of other oil-soluble , fluorescein -type , sulfonated , and basic colouring agents from lipsticks, blushers, make-up, and nail polish (Bell, 1977). In the above studies, the determination of the separated dyes was by UV/VIS . Sjoberg and Olkkonen (1985) analyzed synthetic organic colouring agents in lipsticks after separating them by direct application of the sample on the TLC plate and then determining the extracted colouring agents by LC . Direct application of lipsticks on the TLC plate combined with developing the plate with a series of selective eluants of increasing polarity , or use of solvent extraction with dimethylformamide followed by TLC , enabled Perdih (1972) to separate more than 150 dyes, 37 of which were found in lipsticks. 35

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Gagliardi et al. (1995) presented the ratio to front ( Rf ) (also called retardation factor) values obtained for the 20 colouring agents most frequently encountered in cosmetic products, when they were developed on silica gel TLC plates with eight different solvent systems. Those authors also reported the volume of solvent needed for the elution of the colouring agents with three LC solvent systems. The described methods were applied to the analysis of the colouring agents present in 25 cosmetic products (lipsticks, mouthwash, toothpaste, eye shadows, and blushers). The authors considered the information obtained by the TLC analysis as preliminary, as screening tests, and complementary to the LC analyses. 36

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Ohno et al. (1996) developed a reversed-phase TLC on octadecylsilica (C18) gel method that complementarily employs four solvent systems to separate 45 water-soluble dyes, most of which are used for colouring cosmetics or food in Japan . They applied that method in combination with scanning densitometry to separate and identify dyes in a cosmetic lotion, a bath preparation, and imported candies. Another reversed-phase TLC-scanning densitometry method, which involves two developing solvent systems, has been used by Ohno et al. (2003) to separate and identify 11 oil-soluble cosmetic dyes . That method was applied to the separation and identification of colouring agents present in two kinds of nail polishes and other cosmetic products. 37

Liquid chromatography: 

Liquid chromatography Currently, LC combined with UV/VIS detection is the most used analytical technique for the determination of dyes and pigments. Ion-exchange LC uses strong anion-exchange columns (or weak anion-exchange columns for separation of azo dyes ) and gradient elution with buffered eluants . Reversed-phase LC uses columns packed with short-chain alkyl-bonded silica (e.g. octyl (C8), octadecyl (C18)), amino-bonded, and cyano -bonded phases , or cross-linked polystyrene- divinylbenzene copolymer packing materials . Depending on the composition of the eluant (usually buffered to obtain an appropriate pH level and modified with an organic solvent such as methanol or acetonitrile ), one can influence the affinity of the analyte for the column packing material by ion suppression or an ion-pairing mechanism, using either isocratic or gradient elution . The preferred method of detection is with a UV/VIS diode-array detector (DAD) , which has the capability of simultaneously recording absorbance data from 190 to 800 nm. Another advantage of DAD is that matching with spectral libraries of previously analyzed standard compounds may identify eluted peaks. 38

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Wegener et al. (1987) characterized 126 colouring agents through their retention time and UV/VIS spectra obtained with an ion-pair reversed phase LC system . A C18 bonded silica-packed column and gradient elution were used with an eluant made of distilled water and a dilute solution of tetrabutylammonium hydroxide (ion-pairing reagent) in aqueous methanol (pH 7.0 adjusted with phosphoric acid). The UV/VIS spectra were recorded with a DAD . The method was applied to the determination of the colouring agents used in 45 cosmetic products including lipsticks, nail polish, shampoos, foam bath, face powder, makeup, eye shadow, after-sun cream, and bar soap. Sample preparation: included heating the sample with dimethylformamide (DMF) that contained 5% phosphoric acid, followed by filtration. The filtrate was diluted with aqueous 0.1 M tetrabutylammonium hydroxide and extracted twice with chloroform. The combined extracts were concentrated and analyzed by LC. This general extraction procedure was slightly modified, according to the type of cosmetic product processed (e.g. lipsticks had to be defatted by extraction of the acidic DMF solution with n-hexane, prior to filtration). 39

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Rastogi et al. (1997) built a spectral library consisting of retention times and UV/VIS spectra of 130 organic cosmetic colouring agents using an ion-pair reversed-phase LC method. An Analytical Column Packed With A Polymeric Material Gradient Elution was used with a mobile phase that consisted of three solvents: citrate buffer containing tetrabutylammonium hydroxide as the ion-pairing reagent (pH 9.0 adjusted with concentrated ammonia), acetonitrile and tetrahydrofuran . The UV/VIS spectra were recorded with a DAD . The method was applied to the analysis of colouring agents present in 139 cosmetic products. Those products were collected from 52 manufacturers representing 12 European countries and the U.S. Among the products analyzed were lipsticks, nail polishes, mascara, eyeliner, eye pencil, eye shadow, shampoos, bath gel, body lotion, roll-on deodorant, skin tonic, aftershave, and beauty toner. Detailed sample preparation procedures were presented for the various cosmetic products, including an SPE method for the extraction of the colouring agents from cosmetics with complex matrices. 40

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Several LC methods have been developed to identify xanthene dyes in lipsticks. Gagliardi et al. (1988) analyzed 99 lipsticks for the presence of xanthene dyes by a reversed-phase LC method. A C18 bonded silica-packed column and gradient elution were used Eluant made of water (pH 3 adjusted with glacial acetic acid) and acetonitrile . Detection was performed with a variable-wavelength UV/VIS detector . The dyes were extracted from the lipsticks following the sample-preparation methods described by Etournaud and Aubort (1983) and Lehmann (1986). 41

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Gagliardi et al. (1996) developed a method for the extraction, separation, identification, and quantification of the aminoxanthene dye , Rhodamine B (CI 45170), in cosmetic products (prohibited as a cosmetic colouring agent in both the U.S. and the EU). Extraction methods are given according to the type of cosmetic (i.e. anhydrous or aqueous formulations). A reversed-phase LC method was developed that uses a C18 column Gradient elution with a mobile phase composed of acetonitrile and 0.1 M aqueous sodium perchlorate (pH 3 adjusted with perchloric acid). The UV/VIS spectra were recorded with a DAD . The method was successfully applied to the analysis of Rhodamine B in cosmetic products (e.g. shampoos, lipsticks, foam bath) which were spiked with the dye. 42

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Scalia and Simeoni (2001) developed an assay of six xanthene dyes in lipsticks using an inverse supercritical fluid-extraction (SFE) method for sample preparation. The SFE extraction produced recoveries that were comparable to those with a conventional liquid–liquid extraction method. The separation of the extracted dyes was performed by LC with a cyanopropyl packed column , Isocratically eluted with aqueous sodium acetate (0.02 M, pH 4.5) : acetonitrile : methanol (55:35:10) . The spectra were recorded with a variable wavelength UV/VIS detector . 43


Spectrophotometry Simultaneous determination of up to four colouring agents in cosmetic products was demonstrated by applying various spectrophotometric techniques. In all cases, the colouring agents were isolated from the cosmetic product by liquid–liquid extraction with an ethanol/water/ methylene chloride two-phase solvent system. The aqueous phase contained the dyes of interest and the interfering compounds remained in the organic phase. The absorbance of the colouring agents was measured directly in the aqueous phase or after isolation by SPE in Sephadex DEAE A-25 gel . Thus, solid-phase spectrophotometry was applied to the simultaneous determination of Quinoline Yellow (CI 47005) and Brilliant Blue FCF (CI 42090, certifiable as FD&C Blue No. 1) in perfumes, aftershave lotion and a shampoo gel (Capitan- Vallvey et al., 1996). 44

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First-derivative spectrophotometry methods were used for the simultaneous determination of tartrazine (CI 19140), certifiable as FD&C Yellow No. 5, and Brilliant Blue FCF in cologne and Eau de Cologne (Capitan- Vallvey et al., 1995) and of tartrazine and Sunset Yellow FCF (CI 15985), certifiable as FD&C Yellow No. 6, in shampoos, bath gel, and cologne (Capitan- Vallvey et al., 1997a). A method that was based on partial least-squares multivariate-calibration UV/VIS spectrophotometry was applied to the simultaneous determination of Sunset Yellow (CI 15958), tartrazine (CI 19140), Brilliant Blue FCF (CI 42090), and Quinoline Yellow (CI 47005) in cologne, bath salts, aftershaves, deodorants, facial tonics, bath gels, and shampoos (Capitan- Vallvey et al., 1997b). 45

Other methods: 

Other methods Desiderio et al. (1998) reported a quantitative method of analyzing dyes in lipstick using micellar electrokinetic capillary chromatography (MEKC) with diode array UV detection . This electrophoretic method was optimized for the separation of seven cosmetic dyes: Eosin Y (CI 45380), certifiable as D&C Red No. 22; erythrosine (CI 45430); cyanosine (CI 45410), certifiable as D&C Red No. 28; Rhodamine B (CI 45170); Orange II (CI 15510), certifiable as D&C Orange No. 4; Chromotrope FB (CI 14720); and tartrazine (CI 19140), certifiable as FD&C Yellow No. 5. The process was fast (3 min per separation). The colouring agents in the lipstick samples were extracted using a modified shortened version of Etournaud and Aubort’s (1983) general sample-preparation method. The method was successfully applied to the analysis of a lipstick sample in which Eosin Y and cyanosine were present. 46

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Rodger et al. (1998) demonstrated the use of surface-enhanced resonance Raman scattering (SERRS) spectroscopy , without any separation procedure , to analyze dyes and pigments in lipsticks. Lipsticks smeared on glass and cotton surfaces required treatment with a surfactant, for example, poly(L-lysine), and silver colloid prior to the analysis. This in situ SERRS method was applied to six commercial lipstick samples. Discrimination between the samples and identification of some of the pigments present were achieved. The method is qualitative in nature and was suggested to have potential for forensic and quality-control applications . 47



The importance of determining colouring agents: 

The importance of determining colouring agents There are several reasons for determining colouring agents in cosmetic products. The determinations have Regulatory , Forensic , or Manufacturing significance. To ensure that only permitted colouring agents are added to the cosmetic product To ensure that the information on the label is complete and correct To determine the cause of allergic and dermatologic reactions To help in forensic investigations To determine the stability of a colouring agent added to various matrices Quality control 49

(a) To ensure that only permitted colouring agents are added to the cosmetic product: 

(a) To ensure that only permitted colouring agents are added to the cosmetic product Colouring agents permitted in one country are sometimes not approved in others. For example, erythrosine is permitted in cosmetics as a colouring agent in the EU (as CI 45430) and as a colorant in Japan (as Aka3), but it is not permitted for use in cosmetics in the U.S. (21 CFR 81.30(u)). A different case is the colouring agent Quinoline Yellow . This quinoline -type dye consists of a mixture of mono-, di -, and trisulfonated positional isomers, the relative proportions of which depend on the degree of sulfonation obtained during its manufacture. A mixture of the monosodium salts of the 6- and 8-monosulfonic acids with up to 15% of the disodium salts of the disulfonated isomers is certifiable in the U.S. as the colour additive D&C Yellow No. 10 (Table 4.2.7) (21 CFR 74.1710). A mixture that contains mostly di - and trisulfonated components is permitted as a cosmetic colouring agent in the EU (as CI 47005) and as a colorant in Japan (as Ki203) (see Rosholt, 2003). Even though both of these variant forms are indexed as CI 47005, the latter mixture (i.e. consisting mainly in di - and trisulfonated components) is not certifiable in the U.S. and is therefore not permitted in cosmetics that are imported and sold in the U.S. 50

(b) To ensure that the information on the label is complete and correct: 

(b) To ensure that the information on the label is complete and correct In U.S. , for example, the colouring agents that are part of a cosmetic product must be declared by name on the product’s label (21 CFR Section 701.3). Analysis of the cosmetic may find undeclared certified or certification-exempt colour additives. If the information is not complete or not correct, the product is misbranded and may also be adulterated depending on what is found. 51

(c) To determine the cause of allergic and dermatologic reactions: 

(c) To determine the cause of allergic and dermatologic reactions Contact of the human body with certain colouring agents, their impurities , or their decomposition products (that may occur during processing or storage of the cosmetic product) can produce allergic reactions, sensitization , or photosensitization in susceptible people (Rosenthal et al., 1988; Wei et al., 1994, 1995; Mselle , 2004; Antonovich and Callen , 2005; Klontz et al., 2005). Determination of the colouring agent(s) present in the cosmetic product used may provide a clue to the source of the unexpected reaction . 52

(d) To help in forensic investigations: 

(d) To help in forensic investigations Lipstick smears left on drinking glasses, cups, and cigarette butts can link a suspect to a crime scene. When found on a suspect’s clothing, they can prove a link between the suspect and victim. Results obtained from the analysis of lipstick smears in a forensic science laboratory are often found to be important evidence in criminal cases (Barker and Clarke, 1972; Andrasco, 1981; Russel and Welch, 1984; Gennaro et al., 1994; Griffin et al., 1994; Ehara and Marumo , 1998; Rodger et al., 1998). 53

(e) To determine the stability of a colouring agent added to various matrices: 

(e) To determine the stability of a colouring agent added to various matrices The stability of a colouring agent can be affected by many factors during storage of the cosmetic product. Such factors are light, heat, pH, nature of the packaging , nature of the product base , etc. (Rush, 1989; Otterstatter, 1999). 54

( f ) Quality control: 

( f ) Quality control Cosmetic manufacturers must determine colouring agents present in their products in order to ensure that quality standards are consistently maintained (Rodger, 1998). This quality control may be conducted at various stages in the production and pre-marketing process. The sample tested is compared with a standard using various analytical techniques such as colorimetry and spectroscopy (DRAGOCOLOR, 2004). 55