Cosmetovigilance in Hair Straighteners: Determination of Formaldehyde Content by Spectrophotometry and Label Evaluation

The aim of this work was to identify and quantify formaldehyde present in commercial hair straightening formulations, the application of cosmetovigilance from organoleptic/physicochemical tests and label analysis being approached. Samples A1, A3, A5, and A8 had a formaldehyde concentration ranging from 1.5 to 3.83% (w/v), corresponding to concentrations of 7.5, 16.45, 7.9, and 19.15 times higher than that allowed by the National Agency of Sanitary Monitoring (ANVISA), resulting in strong odor characteristic of this active substance. Of these samples, A3 and A5 did not indicate the presence of formaldehyde on the label besides ignoring the warning information and restrictions of use. The absence of the registration number granted by ANVISA for sample A5, which may be an indication of a clandestine product, was also verified. As to the organoleptic and physicochemical properties, only the A2 sample presented different viscosity and centrifugation results. In view of these results, it was concluded that 50% of the analyzed products were reproved because of the presence of formaldehyde out of the allowed concentration, being evident the importance of the implantation of cosmetovigilance system to guarantee the final quality of the cosmetic products, mainly in view of the safety and efficacy of these products.


Introduction
The beauty market, including toiletries, perfumes, and cosmetics, is one of the fastest growing of all market segments. According to data collected by the Brazilian Association of Personal Hygiene, Perfumes and Cosmetics Industry, Brazil is the third largest sales market with a turnover of approximately R $ 29.4

Reagents
For the accomplishment of this research, the following reagents were used: formaldehyde PA 37% (Impex), 99% chromotropic acid (disodium dihydrate salt, Sigma-Aldrich), and 98% magnesium sulfate (Sigma-Aldrich), all of analytical grade. Distilled water was used for the preparation of all solutions.

Collection of samples
For the development of the research, eight samples of permanent and progressive hair straighteners in cosmetic cream from different manufacturers were collected in salons of the municipality of Cuité, PB. The samples were named A1-A8, and their qualitative compositions are described in Tables 1 and 2.

Dosing of formaldehyde
The methodology used to identify and quantify the formaldehyde content in progressive brush products was applied according to the standard method recommended by the National Institute of Occupational Safety and Health [11], followed by the modifications described by Gasparini et al. [12].

Preparation of solutions
The stock solution of formaldehyde with of 1000 mg. L −1 was prepared using 2.7 ml of 37% (v/v) formaldehyde solution diluted with distilled water in a 1000 ml volumetric flask. An aqueous solution of chromotropic acid (CA) 5% (w/v) was prepared, dissolving 1.25 g of solute with distilled water in a 25 ml volumetric flask. An aqueous solution of magnesium (MgSO 4 7.H 2 O) 60% (w/v) was prepared, dissolving 60 g of solute with distilled water in a volumetric flask 100 ml.

Analytical curve for the identification of formaldehyde
The identification of formaldehyde in the solutions was done through the reaction that occurs between the chromotropic acid and formaldehyde in the presence of magnesium after heating, thus producing a colored compound, indicating the presence of formaldehyde in a solution. For the determination of the analytical curve of formaldehyde, the following test was performed: 90, 120, 150, 180, 210, 220, and 230 μl of stock solution containing formaldehyde were transferred to test tubes. In Then, 290 μl of solution of 5% (w/v) chromotropic acid and 3.0 ml of solution of 60% (w/v) magnesium sulfate, with stirring. The tubes were heated for 60 minutes in a steam (100°C), followed by cooling to 25°C. The solutions were transferred to 25 ml flasks and the volume filled with distilled water, obtaining the concentrations of formaldehyde (ppm): 3.6, 4.8, 6.0, 7.2, 8.4, 8.8, and 9.2, respectively. The measurements of absorbance were recorded at 535 nm. All reviews were carried out in triplicate, in order to guarantee the accuracy of the results obtained.

Determination of formaldehyde in the sample
For each commercial sample, 3.0 g was weighed and then dissolved in about 20 ml of distilled water, and the final volume was completed to 100 ml, yielding a solution with concentration (C1) of 30,000 μg ml −1 . After 5.0 ml of this solution (C1) were diluted in 25 ml of distilled water (C2 = 6000 μg ml −1 ). Aliquots of 1.0 ml of the solutions (C2) were transferred to test tubes together with 290 μl of chromotropic acid 5% (w/v) and 3.00 ml of magnesium sulfate 60% (w/v). The tubes were heated for 60 minutes in a steam bath (100°C), followed by cooling to 25°C. The solutions were transferred to 25 ml volumetric flasks, and then the volume was filled with distilled water resulting in a concentration (C3) of 240 μg ml −1 . The measurements of absorbance were performed at 535 nm.

Organoleptic and physicochemical properties
The organoleptic and physicochemical tests were performed to assess the characteristics of the products in study. The organoleptic and physicochemical characteristics evaluated were odor, color, appearance, pH, viscosity, density, and centrifugation [13], which were correlated between samples.

Determination of pH
For the determination of the pH, the potentiometric method was used. The samples were diluted to 10% (w/v) in distilled water, at room temperature, in triplicate [13][14][15].

Determination of viscosity
The viscosity was measured in triplicate in an analog rotary viscometer using 40 g of sample, spindle 4 and speed of 6 rpm. Next, the rotor was inserted vertically into the sample free of blister up to the groove of the rotor rod, and the apparatus was leveled, by reading the viscosity according to the operating procedure of the device [13].

Determination of density
The density was determined by pycnometry. Initially the empty pycnometer (M0) was weighed, first, with distilled water (M1) and, finally, (clean and dry) with the sample (M2). The masses were noted for calculation using the following formula [13]: where d is the sample density in g/cm 3 ; M0 is the mass of the empty pycnometer, in grams; M1 is the mass of the pycnometer with distilled water, in grams; and M2 is the mass of the pycnometer with the sample, in grams.

Centrifuge test
From each sample, 5 g was placed in centrifugal tubes and submitted to cycles of 1000 and 2500 rpm for 15 minutes each. The homogeneity of the study formulations was evaluated by observing macroscopic separation of phases after performing the described procedure [13,14,16].

Label analysis
A qualitative analysis of the primary and secondary packaging of the tested products by a critical visual investigation was carried out, following the criteria laid down by national legislation-RDC 211/2005 which defines the labeling rules for cosmetic products [17] and RDC 332/2005 which deals with regulation and implementation of cosmetology in the cosmetic industries [6]. The analyzed items were specified according to Figure 1.

Analytical curve for the identification and determination of formaldehyde
The identification of formaldehyde was evidenced by the production of a pink compound resulting from the reaction between chromotropic acid and formaldehyde in the presence of magnesium sulfate. The analytical curve data, resulting from the average of three calibration curves, were adjusted by linear regression (Figure 2), whose equation of the line is given by absorbance = 0.0922 × [formaldehyde solution, chromotropic acid, and magnesium sulfate] (ppm) − 0.0234. The correlation coefficient obtained was 0.996, a significant linear regression. Samples A1, A3, A5, and A8 developed a coloration after heating, indicating the presence  of formaldehyde in these formulations, which tends to be as darker as greater the concentration of said substance. The samples A3 and A8, on the other hand, presented more intense in relation to others, which justifies a higher concentration of formaldehyde. The percentages of formaldehyde calculated by the equation from the analytical curve confirm these results and are described in Table 3.

Organoleptic and physicochemical characteristics
The results obtained in organoleptic and physicochemical tests of the study samples are listed in Table 4. Regarding appearance and color, observed macroscopically, the samples presented as homogeneous creams, whether or not colored and without precipitation or exudation. The odor was checked directly through the smell, being possible to smell characteristic of formaldehyde in samples A1, A3, A5, and A8, capable of causing some mucosal irritation and burning in the eyes during observation, confirming symptoms caused by exposure to formaldehyde. The sample A5, although with a strong chocolate odor, failed to mask the presence of formaldehyde in the product. Samples A6 and A7 showed an odor of sulfur, a characteristic of thioglycolic acid. The samples A2 and A4 presented no strong or unpleasant smell, only the essence odor used in these products.
Samples A2 and A4 showed a pH of very acid (1.0 and 1.3, respectively), which may damage the capillary wires [18]. In the other hand, the sample A8 has a pH   within the range that tends to assist in the maintenance of wires. The samples A1, A3, and A5 also have a pH slightly acidic, being able to close the capillary cuticle and help in preserving the color deposited in the hair. The samples A6 and A7 presented extremely high pH, a characteristic of products for permanent straightening.
The analyzed samples did not present significant variation in relation to the determination of the density and did not need to correct the weighing to carry out the dosing of the formaldehyde.
The formulations showed without phase separation, precipitation, formation of caking, and coalescence, except the A2 sample that presented phase separation after being subjected to the centrifugation.
The viscosity results can be in Figure 3. These results point to discrepant values between formulations, ranging from extremely low (A2) to extremely high (A6 and A7).

Label analysis
The results of the analysis of the product labels are presented in Table 5. Samples A1, A3, A5, and A8 presented formaldehyde content in the procedure spectrophotometric assay; however, only samples A1 and A8 indicated formaldehyde in their composition. Samples A3 and A5, in addition to the absence of the substance, presented other irregularities on the label, both ignoring the warning information and usage restrictions. Sample A5 does not yet have registration number granted by ANVISA, evidencing the likely clandestine origin of this product.
The samples A2, A4, A6, and A7, whose labels said formaldehyde-free, are not really content of the substance, being in compliance and complying with the technical requirement legislations.

Discussion
According to the NIOSH 3500 [11] reference method, formaldehyde is determined by spectrophotometry through reaction with chromotropic acid in the presence of concentrated sulfuric acid, after heating, to obtain a soluble polymer violet-red that can be detected in length of wavelength of 580 nm. However, although the method is selective, not suffering interference from other aldehydes, it has some drawbacks. The main one is the use of concentrated sulfuric acid by the toxicity and corrosivity that it presents. Therefore, some authors have proposed modification methodology that could minimize these disadvantages [12,[19][20][21][22][23].
According to Toutianoush et al. [22], it is possible to dose the formaldehyde by spectrophotometry in the presence of a solution of magnesium sulfate (MgSO 4 •7H 2 O) instead of sulfuric acid. A red/pink is produced after heating of formaldehyde with an excess of chromotropic acid in a steam bath. In the absence of magnesium sulfate, this reaction does not occur. It is likely that the oxygen atoms of the cyclotetrachromotropylene-hydroxyl are pre-arranged for complexation with magnesium. Gasparini et al. [12] used this method to dose formaldehyde disinfectants and hair care products, considering the adequate method, low operating cost, and simplicity and selectivity, meeting the requirements of green analytical chemistry.
Thus, the applicability of the proposed method to determination of formaldehyde in straightening hair products of different brands proved to be appropriate, possible to identify the presence of formaldehyde in samples A1, A3, A5, and A8 in concentrations ranging from between 1.5 and 3.83% (w/v), i.e., concentrations 7.5; 16.45; 7.9 and 19.15 times that allowed by ANVISA [5].
Some authors also dosed formaldehyde in commercial formulations of hair straighteners using methods such as HPLC, gas chromatography, and mass spectrometry, finding concentrations of 1.6-11.5%, similar results to that of this research, with concentrations above that accepted, evidencing the use of formaldehyde as a hair straightener and not just as a preservative at the maximum concentration of 0.2%, as recommended by health legislation. This shows the lack of supervision by regulatory institutions and the deep lack of knowledge or lack of concern for part of consumers and professional hairdressers in face of the risks that these products bring to health [24,25].
In addition to the assay, it is also important to analyze the organoleptic and physicochemical characteristics of a cosmetic formulation, because usually the texture, odor, color, and appearance of the product are examined before your purchase; these being important parameters from the commercial point of view, consumers may or may not be attracted to these characteristics. The sample A5 presents a dark-brown tone and chocolate essence; these characteristics tend to seduce the consumer. The color of a product, however, has no connection with the presence or absence of formaldehyde, differently from the intense odor, which may be indicative, since even using extremely high essences fragrant, it is still possible to smell it.
The pH of the hair strands ranges from 4.5 to 5.5. Capillary formulations with extreme pH variations can damage the capillary wire, because the hair shrinks and stiffens or even dissolves completely at very high pH acid or increases porosity as the layers of cuticle dilate, resulting in a dry appearance, opaque, reaching to complete hair dissolution in strongly alkaline pH. The pH values of samples A1, A3, A5, and A8 were compatible with the hair samples, while samples A2, A4, A6, and A7 had a pH out of the tolerated range, the integrity of the capillary wire [18]. In this way, products for professional use should be used with caution and applied by trained professionals.
© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Viscosity is a measure of resistance of a flow system when submitted to a mechanical stress. Therefore, the higher the viscosity, the higher the resistance and the force to be applied to flow with a certain velocity [26]. In the case of the products tested, there was a considerable variation of this parameter, of samples having viscosities less than 4000 cP to samples with viscosities above of 12,000 cP, thus presenting flow profile applicability. The viscosity results can also inform the influence of the sedimentation rate of the droplets present in the cosmetic cream form, complementing the result of the centrifugation.
The centrifugation test provides quick information about phase separation, thus predicting whether the product will separate as a function of time [13], which can lead to significant differences in the content of assets. In the present study, only the A2 sample presented separation of post-centrifugation phases, which can be influenced by the low viscosity of the sample (566 ± 57.7 cP). According to Stokes's law, the speed of sedimentation is inversely proportional to viscosity and directly proportional to the size of the droplets, the gravity, and the density difference between the dispersed medium and dispersant [27].
The evaluation of product quality parameters for progressive brush becomes essential, once beauty salons are frequently visited by sales promoters that offer products that are capable of providing a "true miracle" in straightening the hair without formaldehyde in its composition. However, they may have a high concentration, masked by an extremely fragrant and unidentified formula of its presence on the label [28], which could be proven in the present study, where 50% of the products for hair straightening analyzed were disapproved due to the presence of formaldehyde out of the concentration allowed, as well as irregularities in the labels.

Conclusion
The chapter is important to the cosmetovigilance system to ensure the final quality of cosmetic products, taking into safety, efficacy, and information to ANVISA, to the manufacturer, and to the consumer. In this way, this system may provide numerous benefits to the cosmetics industry as a whole. As measures, it would be important to distribute orientation books and flyers of cosmetic products since the vigilance is not only the responsibility of companies but also of the consumers and competent institutions.