Theoretically develop a new sampling technique and a new analytical method for the analysis of triclosan on human skin capable of detecting 5 ppb
Abstract
In this experiment, a novel method of detecting trace amounts of the organic compound triclosan is explored, ideally at a five parts-per-billion (ppb) range. In order to achieve this, triclosan should be adsorbed onto a pad that can undergo semi-automated solid phase extraction so the compound can be injected into a reverse-phase high-performance liquid chromatography (RPLC) column, then detected via electrospray ionization mass spectroscopy (ESI-MS). Before injecting the compound into the column, it should be diluted to a known amount, such as 100 microliters, as that is the lowest volume that can be utilized with a column that has a diameter of 0.21 cm and can undergo ESI-MS, 1,2 with a nonpolar solution such as hexane. While the theory behind this analytic method was explored, the experiment has yet to be conducted; ESI-MS can be used to detect ionizable chemicals in the low parts-per-billion range, indicating it would likely be effective for measuring triclosan. The results of this study would likely be consistent within uncertainty limits due to the sensitivity of the instrument and the known effectiveness of separating triclosan using high-performance liquid chromatography (HPLC). 3,4
Introduction
Triclosan is the common name for the compound 5-chloro-2-(2,4-dichlorophenoxy)phenol, which has the molecular formula C12H7AgCl3O2. 5 The compound is a white powder 6 with a molecular weight of 397.404 grams per mole. 5 Furthermore, triclosan has a solubility of 12 grams per liter in water at 20 °C, a melting range from 56 °C to 60 °C, and a boiling range from 280 °C to 290 °C, decomposing at high heat. The compound has low biodegradability and is toxic to fish and other aquatic invertebrates; it is also a known eye and skin irritant. 6 A standardized method of sampling triclosan from the skin does not currently exist; due to the risk of skin irritation caused by the compound and other potential dangers, a novel analytical method should be developed in order to detect its presence.
Much of the research involving triclosan relates to the environment and how to sample it in bodies of water. The paper “Study on detection methods for triclosan in environmental samples” by Liyun Yuan and Xiaodong Dong suggests using HPLC coupled with a tandem mass spectrometry system to identify the compound in bodies of water. The limit of quantification in this study was 0.083 mg/g and the limit of detection was 0.016 mg/g, meaning this method of detection would be ineffective for trace analysis. 4 However, a study focusing on the microextraction of triclosan in water samples experienced success measuring the compound in the low parts-per-billion range using electrospray ionization mass spectroscopy (ESI-MS). 3 Detecting triclosan on human skin at a trace amount of five parts-per-billion could theoretically be achieved through a series of novel adaptations to sampling, separation, and detection techniques previously studied. In order to sample the compound, it could be removed from the skin using an adsorbent pad, the pad could be used as the stationary phase in high-performance liquid chromatography, and electrospray ionization mass spectrometry could be successful for detecting the triclosan at the desired amount.
Experimental Method
In this experiment, one would need an adsorbent pad cut to an approximate size of 0.21 by 15 centimeters in order to fit in a standard HPLC column; the pad would need to be hydrophobic in order to allow the triclosan to adsorb. SpillFreak Bronze Series Oil Only Adsorbent Pads would work to collect triclosan from the skin as it is a nonpolar, hydrophobic compound. 8 The pad would be placed on a section of skin of interest and allowed to sit for five minutes to ensure the compound was fully adsorbed.
Once sampling was completed, an RPLC column should be assembled, and the inner side of the column should be lined with the pad in order to use it as a stationary phase. First, a polar eluent such as deionized and distilled water, then a medium-polarity eluent such as ethyl acetate, and finally a non-polar eluent such as hexane would be ran through the column. Any triclosan in the sample would be eluted with the hexane. Once the column had finished running, triclosan could then be detected using ESI-MS. To determine if a peak indicated triclosan, once a spectrum was collected, the sample could be spiked with a 10 ppb triclosan standard. From there, the peak could be statistically analyzed and the concentration of triclosan in the original sample could be determined. 9 Based on its detection range, ESI-MS would be able to accurately analyze a five part-per-billion sample of triclosan. 3
This experiment should first be run using a control group. Human sebaceous glands produce sebum, which are lipids that help to protect the skin and are fat-soluble. 9 An adsorbent pad should be placed on skin that has been washed with soap and water, and has not been exposed to products containing triclosan. From there, reverse-phase HPLC can be ran using the method previously described, and analyzed with ESI-MS to create a baseline and account for peaks indicating sebum.
Projected Data and Results¬¬
In order to obtain meaningful results from this study, several factors would need to recorded and analyzed. The time the adsorbent pad was left on the test subject’s skin should be recorded; it should be given ample time to adsorb, so leaving the pad for five minutes would be sufficient. The amount of time and amount of material eluted should also be recorded and has the potential to help determine percent recovery. Peaks shown by the ESI-MS should be documented before spiking, then again after spiking. Finally, based on the information provided by the analytical technique, the concentration of triclosan can be calculated if it was detected.
Experiment Pad left on skin
(minutes) Time to elute (minutes) Amount euted
(mL)
Baseline Five minutes Water
X minutes Water
X mL
Ethyl Acetate
X minutes ¬Ethyl Acetate
X mL
Hexane
X minutes Hexane
X mL
Skin exposed to triclosan Five minutes Water
X minutes Water
X mL
Ethyl Acetate
X minutes Ethyl Acetate
X mL
Hexane
X minutes Hexane
X mL
Ethyl Acetate
X minutes Ethyl Acetate
X mL
Hexane
X minutes Hexane
X mL
Experiment ESI-MS peaks before spiking
(m/z, au)
ESI-MS peaks after spiking
(m/z, au) Triclosan concentration
(ppb)
Baseline X m/z
X au X m/z
X au 0 ppb
Skin exposed to triclosan X m/z
X au X m/z
X au X ppb
Discussion and conclusions
Based on the type of data this experiment provides, it would be possible to conclude if triclosan was present on human skin, and if so, to what extent assuming there was at least a five ppb concentration. Adsorbent pads such as those sold by SpillFreak are designed with the purpose of adsorbing hydrophobic products, indicating that it would allow triclosan to adsorb; if given an adequate amount of time to sit on the skin, most of the compound would likely adsorb. 8 Furthermore, as other researchers have experienced success using liquid chromatography methods to separate triclosan from a matrix 3,4, and considering that it is a non-polar compound, RPLC should be able to separate it and allow for a high percent yield. By recording the amount of liquid eluted and the time it takes for each eluent to run, it would be possible to calculate the percent recovery later and determine the extent of the success of the method. Moreover, based on the low limit of detection offered by ESI-MS, and previous studies illustrating its effectiveness, it should be able to give an accurate, precise reading for a sample of triclosan at five ppb. 3 Spiking the sample could help confirm the accuracy; if a known amount of triclosan standard was added, it would be possible to calculate the total amount in the sample. These results would likely support the hypothesis that an adsorbent sampling method combing with RPLC-ESI-MS analysis would be effective. Overall, this novel analytical technique shows a feasible way to detect trace amounts of triclosan, allowing researchers to sample the compound directly from a person’s skin.
References
1. Oliver, R. W.A., editor. HPLC of Macromolecules: A Practical Approach. 2nd ed., vol. 872,
Oxford University Press, 1998.
2. “Sample Preparation Guidelines.” QB3Berkeley Macrolab, QB3Berkeley Macrolab, qb3.berkeley.edu/msf/sample-preparation-guidelines/.
3. Zhao, R S, et al. “Trace Determination of Triclosan and Triclocarban in Environmental Water Samples with Ionic Liquid Dispersive Liquid-Phase Microextraction Prior to HPLC-ESI-MS-MS.” PubChem, U.S. National Library of Medicine, www.ncbi.nlm.nih.gov/pubmed.
4. Yuan, Liyun, and Xiaodong Dong. “Study on Detection Methods for Triclosan in Environmental …” International Journal of Chemical Studies, International Journal of Chemical Studies, www.bing.com/cr?IG=14685C82FD744FBFB9B7CDE919B83DE6&CID=0CF7AEEC0CF56F72035FA2DF0D086E06&rd=1&h=WOazy0dIvDymK_7EuXK1jWyMenzef31l1zmA4kTsEtk&v=1&r=https://pdfs.semanticscholar.org/c4fb/16dd55793ef60cfd44f0d92d4e7a7c595f42.pdf&p=DevEx.LB.1,5501.1.
5. “5-Chloro-2-(2,4-Dichlorophenoxy)Phenol;Silver.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, pubchem.ncbi.nlm.nih.gov/compound/87205408#section=Top.
6. “Safety Data Sheet.” Sigma-Aldrich, Merck KGaA, www.sigmaaldrich.com/MSDS/MSDS/DisplayMSDSPage.do?country=US&language=en&productNumber=524190&brand=ALDRICH&PageToGoToURL=https://www.sigmaaldrich.com/catalog/product/aldrich/524190?lang=en.
7. Cotton, Simon. “TRICLOSAN.” University of Bristol School of Chemistry, University of Bristol, Nov. 2014, www.chm.bris.ac.uk/motm/triclosan/triclosanh.htm.
8. “Spillfreak™ Bronze Series Oil Only Pads (100 Count).” Spillfreak, SPILLFREAK INC., spillfreak.com/oil-only-pads-sfbsop100.
9. Picardo, Mauro, et al. “Sebaceous Gland Lipids.” Dermatoendocrinology, vol. 1, no. 2, 2009, pp. 68–71. National Center for Biotechnology Information, www.ncbi.nlm.nih.gov/pmc/articles/PMC2835893/.