Before the chemical analysis, pepper spray packaging and bottles were visually inspected, which revealed the low quality of these products. Spelling and/or grammatical errors were found, as well as malfunctioning nozzle sprayer, which leaked and backfired upon being pressed, spraying the solution onto the user’s hands.
Infrared spectroscopy (IR) is a simple and efficient tool to identify active ingredients in manufactured products. In the case of pepper spray, the presence of natural capsaicin (capsaicin + dihydrocapsaicin) and nonivamide can be detected. Figure 2 shows the FTIR spectrum of sample 3 after chloroform extraction and evaporation of the solvent and database FTIR spectra of nonivamide, natural capsaicin and CS gas.
The results of the infrared analysis of the three pepper sprays brands were basically the same. The FTIR spectra of the samples were quite similar to the nonivamide spectrum stored in the database, with the most important and characteristic bands corresponding to N-H stretching vibration (3288 cm− 1), aliphatic C-H stretching vibration (2923 cm− 1 and 2853 cm− 1), C = O stretching vibration (1639 cm− 1), aromatic C-C stretching vibration (1514 cm− 1), N-H bending and C-N stretching vibration (Amide) (1514 cm− 1), and C-O-C asymmetric stretching vibration (1273 cm− 1) [16, 17].
The identification of nonivamide and the absence of natural capsaicin and ortho-chlorobenzylidene malononitrile in the samples were confirmed based on GC-MS analysis, as illustrated in Fig. 3. The GC-MS analysis of the three pepper spray brands revealed basically the same results.
Identification of the active ingredient in manufactured products was based on similarities between the samples and standard reference material. The chromatogram of a sample shows a single peak with the same retention time as the nonivamide standard (Fig. 3a). In addition, the mass spectrum of this peak showed a pattern of fragmentation identical to that presented by the nonivamide standard, with the most important and characteristic fragments at m/z 195, 178, 151, 137, 122, 94 e 41 (Figs. 3b and 3c) [18]. No peaks were detected in the retention times presented by the standards of natural capsaicin (mostly capsaicin and dihydrocapsaicin) or ortho-chlorobenzylidene malononitrile. Moreover, no m/z fragments characteristic of these compounds were found. (Figs. 3d-3f).
As discussed earlier herein, the chemical analysis revealed the presence of active ingredients that do not match the compositions described on their labels, indicating that they are counterfeit or falsified products. Table 2 compares the active ingredients listed on the labels of the confiscated sprays and those identified in our analysis.
Table 2
Comparison of active ingredients listed on labels and those identified by chemical analysis.
CODE
|
Active ingredient (label)
|
Identified by the analysis
|
A
|
CS (Ortho-Chlorbenzylidenmalononitril)
|
Nonivamide
|
B
|
Natural capsaicinand*
|
Nonivamide
|
C
|
Oleoresin capsicum
|
Nonivamide
|
* misspelled word included on the label, among other errors |
Sample A merits an additional comment. The active ingredient that appears on the label of spray A is ortho-chlorobenzylidene malononitrile, i.e., technically, this spray is tear gas and not pepper spray. As mentioned earlier, the only component identified by chemical analysis was nonivamide. Therefore, the label on this sample is completely misleading. As for the other two sprays, B and C, whose labels list natural capsaicin and capsicum oleoresin, respectively, as active ingredients, they are also at odds with our chemical analysis, which basically revealed the presence of nonivamide and the absence of capsaicin, the main capsaicinoid of both natural capsaicin and OC.
As can be seen in Fig. 4, the GC-MS analysis also revealed the presence of traces of n-nanoic acid (Fig. 4a) and the trimethylsilyl derivative (TMS) of nonivamide (Fig. 4b). n-nanoic acid can be used as a precursor in the synthesis of nonivamide [10]. The TMS derivative of nonivamide is not a naturally occurring compound. It can be obtained by means of silylation (introduction of a triorganosilyl moiety, especially the trimethylsilyl species (TMS), into organic compounds), a reaction widely used in organic synthesis [19–21]. Thus, in addition to the prevalent presence of nonivamide and the absence of other capsaicinoids, the presence of n-nanoic acid and TMS-nonivamide suggests the nonivamide is of synthetic origin. Again, this contradicts the information given in the labels of samples B and C, since the terms “natural capsaicinoids” and “Oleoresin Capsicum” refer to products of natural origin.
The other components of the pepper sprays, i.e., solvents and/or propellants, were also subjected to chemical analyses. FTIR spectra obtained directly from non-pretreated samples basically identified methanol (Fig. 5a). The main characteristic bands are O-H stretching vibrations (3307 cm− 1), C-H bond stretching (2944 cm− 1) and stretching vibrations of the C-O bond (1449 cm− 1, 1115 cm− 1 and 1020 cm− 1). Figures 5b and 5c illustrate the result of the GC-MS analysis, identifying methanol by comparing the retention time and mass spectrum with those of standard methanol, showing the most important and characteristic fragments at m/z 30, 31, 32, 33.
Pepper spray is applied by spraying it into the eyes of the target individual. Therefore, the presence of methanol as a solvent is dangerous. Methanol poisoning can cause irreversible neurological sequelae. Although ingestion is the most common route of contamination, methanol can also be absorbed by inhalation and dermal exposure, which are less common routes of chronic and acute poisoning. Studies on chronic methanol poisoning, particularly through skin absorption and inhalation, are scanty, but the few existing studies describe the possibility of serious problems associated with this type of poisoning, such as loss of vision and severe metabolic acidosis, parkinsonism and cerebral vasculopathy [22–23].
The GC-MS analysis also revealed the presence of propane and butane in the samples, suggesting that these substances are used as propellants in the analyzed sprays. Figure 6 compares a representative mass spectrum of the samples (black lines) and mass spectra (blue lines) of propane (Fig. 6a) and butane (Fig. 6b) in the NIST 2.3 library.
Concerns about the flammability and toxicity of pepper sprays are well known and have been widely discussed for some time [13, 24–29]. In general, solvent carriers and propellants are the flammable components of greatest concern. Thanks to the widespread development of pepper sprays, less flammable and toxic substances are now commonly used, such as ethanol, water, propylene glycol and isopropanol. With regard to flammability, almost every formula contains some proportion of alcohol to prevent the mixture from freezing, and its flammability depends on this amount, which is often a limiting factor [25].
Holopainen et al. (2003) described the toxic effect of the carrier in a pepper spray, based on a study in which an individual was exposed to a pepper spray with no active ingredient, i.e., with only carrier. This individual, exposed only to the carrier, suffered corneal erosion similar to that of people exposed to spray with an active ingredient [27].
Regarding toxicity, our analysis basically identified methanol as a carrier solvent, which is a highly toxic substance. The use of methanol in this type of product is entirely unjustified, given the ready availability of various alternative and less toxic carriers. This finding was the main motive for carrying out this work, since, to the best of our knowledge, the use of methanol as a carrier solvent in pepper sprays has not been reported in the literature prior to the date of this study.