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Colorants in transferable picture tattoos for the skin

4 Results

All-in-all 42 products of picture tattoos (or products to which picture tattoos were attached) and similar products were purchased from the Danish retail outlets. Two of the products 4-0224 and 4-0225 were purchased twice (4-0287 and 4-0288 respectively) by different persons in the different part of the country. Often, the picture tattoos in each product were different figures composed of different colours. Therefore, 36 picture tattoos (22 products) were selected for the analysis, so that the most of the colorants used in the collected tattoo stickers were represented.

In a preliminary investigation, 6 different picture tattoos were extracted with various solvents (acetone, methanol, hexane, dichloromethane, acetonitrile, tetrhydrofuran, HPLC-solvent and water). Furthermore, both shaking and ultrasonic treatment was used to investigate the dissolution/release of the tattoo colorants into the solvent. The preliminary study revealed that ultrasonic treatment of the samples (picture tattoos sticking on a paper) in a solvent, followed by gently scraping off the remaining coloured material from the paper into the solvent, was the most suitable method for extracting the colorants from picture tattoos into the solvent. Most of the colorants (but not all) were soluble in HPLC-solvent and THF. But some colorants, especially Black and Blue, were not soluble in the solvents used. To perform a systematic investigation of colorants in all picture tattoo samples, the method described in 3.2 was chosen.

Both HPLC-solvent and THF extracts were analysed by HPLC. The colorants in the sample extracts were identified by matching the retention time and spectrum of each HPLC peak with the retention times and spectra of reference colorants analysed under the same conditions. The identification of colorants in some of the sample extracts is shown in Figures 2-5. As shown in Figures 2C and 5B, the spectrum of sample peak does not match 100% with the spectrum of reference colorant. However, this is not unusual when the concentration of the colorant is very low.

The colorants identified in the picture tattoos are described in Table 2. The unidentified colours in the sample extracts as well as the undissolved colours of the samples are also described in Table 2. The unidentified colorants may be those, which are not included in our library of colours or the concentration of these may be below the detection limit (0.5 ppm).

The colorant(s) in two out of the three Black picture tattoos could not be dissolved in the solvents used in the present study. The black colour in the third product (4-0460) was soluble in ACN:THF (1:1).However, the dissolved black colour from this sample could not be identified by the method used in the present investigation (no HPLC peak). Most of the remaining picture tattoos (31 out 33) were composed of colorant CI15850. Other colorants presents in the investigated picture tattoos were: CI 11920 in 2 out of 33 samples, CI 45220 in 10 out of 33 samples, CI 75300 and CI 74180 each in 4 out of 33 samples, CI 13015 and CI 45100 each in 3 out of 33 samples, and CI 14815 in 2 out of 33 samples. CI 15225, CI 16255 and CI 42170 were present only in one picture tattoo each.

The Blue colour CI 74180 was identified in four of the analysed tattoo stickers. However, the Blue colour in several of the samples could not be extracted. This may also be the reason that green (blue+yellow) and violet (blue+red) colours could not be identified in several of the investigated samples. Sample No. 4-0382 is declared to contain CI 19140 (yellow), CI 15985 (yellow) and CI 42090 (blue), but these colorants could not be identified in the subsamples investigated. It is possible that the content of these colorants in the investigated subsamples is below the detection limit (0.5 ppm) of these.

The contents (semi-quantitative determination) of the identified colorants in the investigated picture tattoos are described in Table 3. The content of the colorants is described as total content of these found in HPLC- solvent and THF extracts. In some samples, the content of certain colorants could not be determined because of the interference from other HPLC-peaks, very close to the HPLC-peak of the target colorant in the sample extract. Furthermore, in some samples the content of certain identified colorants could not be determined due to a very small HPLC-peak. In such cases, approximate content (<2 ppm) is given, calculated on the basis of detection limits of these colorants. The contents of the identified colorants in the investigated samples were: 6-4479 ppm CI 11920, <2 -2926 ppm CI 15850, <2-800 ppm CI 13015, <2-103 ppm CI 45220, <2-35 ppm CI 75300 and 217 ppm CI 15525. The contents of the remaining identified colorants in the tattoo stickers were <12 ppm.

Click here to see figure 2.

Figure 2: Identification of colorants in the HPLC-solvent extract of sample no. 225-2. A: HPLC chromatogram, B: spectrum of 14,118 min chromatographic peak with the spectrum of CI 15850, C: spectrum of 33,122 min chromatographic peak with the spectrum ofCI 75300.

Click here to see figure 3.

Figure 3: Identification of colorants in THF extract of sample no. 226-2. A: HPLC chromatogram, B: spectrum of 14,169 min chromatographic peak with the spectrum of CI 15850, C: spectrum of 21,519 min chromatographic peak with the spectrum of CI 74180.

Click here to see figure 4.

Figure 4: Identification of colorants in the THF extract of sample no.229-2. A: HPLC chromatogram, B: spectrum of 14,841 min chromatographic peak with the spectrum of CI 45220.

Click here to see figure 5.

Figure 5: Identification of colorants n the THF extract of sample no. 250-2. A: HPLC chromatogram, B: spectrum of 24,535 min chromatographic peak with the spectrum of CI 11920.

Table 2: Identification of colorants in picture tattoos

Table 3: Colorants contents (semi-kvantitativt) in picture tattoos

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Version 1.0 August 2005, © Danish Environmental Protection Agency