Integrating Elemental Analysis and Chromatography Techniques by Analyzing Metal Oxide and Organic UV Absorbers in Commercial Sunscreens

Abstract

A series of undergraduate laboratory experiments that utilize reversed-phase HPLC separation, inductively coupled plasma spectroscopy (ICP), and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) are described for the analysis of commercial sunscreens. The active ingredients of many sunscreen brands include zinc or titanium oxide in addition to organic acids. Students determine the zinc content using ICP, and the chemical composition as well as particle sizes using SEM-EDS. The organic UV absorbers octocrylene and oxybenzone are quantified using HPLC. With the incorporation of these interesting characterization techniques in second or fourth-year chemistry courses, and by having students analyze sunscreen samples that are medically relevant in terms of health effects, students engage in timely research and at the same time gain exposure to a variety of instruments in the analysis of a familiar household product.

Benzophenone Accumulates over Time from the Degradation of Octocrylene in Commercial Sunscreen Products

“…The mixtures were sonicated for 30 min in the sweep mode and then centrifuged at 23,000 g for 10 min. 31 For each tube, the supernatant (20 μL) was collected and diluted in acetonitrile (980 μL) in an HPLC vial. For every seven sunscreens, a control analysis (no sunscreen in the Ependorf tubes) was conducted similarly.…”

Examining Particle Size of Inorganic Active Ingredients within Sunscreens Using Dynamic Light Scattering

“…The use of sunscreens has increased over the years due to the general public's growing awareness of the phototoxic effects that can be caused by the sun's ultraviolet rays. 1 Sunscreen development has matured over time in accordance with overthe-counter drug regulations issued by the Food and Drug Administration (FDA). 2 Consumer products are labeled with sun protection factor (SPF) ratings that inform the consumers about the sunscreen's protection against UV-B rays, which occur at wavelengths 290−320 nm and can cause phototoxic effects like melanoma.…”

“…4−6 Avobenzone is one of the most frequently used UVabsorbers along with oxybenzone, octinoxate, octisalate, octocrylene and homosalicylate. 1 However, some of these FDA approved organic ingredients have recently been banned in coastal areas, such as Hawaii, due to the toxicity of organic UV filters to coral species at different life stages. 7,8 In the area surrounding just a single Hawaiian island, Oahu, 8 different UV filters were found in coral and sediment in 19 different sites.…”

“…Although the sunscreen may have a listed SPF of 15 or 30, the sunburn protection is not doubled; the sunscreen may only have an approximate 18% difference in the radiation coverage. 1,10,11 As a result of the disadvantages of organic UV filters (environmental and otherwise), inorganic UV filters may be favored. Inorganic UV filters, including titanium dioxide (TiO 2 ) and zinc oxide (ZnO), are commonly used in a nanoparticle form due to the thermal stability, economical pricing, and ability to scatter UV light from 200 to 500 nm.…”

“…Inorganic UV filters, including titanium dioxide (TiO 2 ) and zinc oxide (ZnO), are commonly used in a nanoparticle form due to the thermal stability, economical pricing, and ability to scatter UV light from 200 to 500 nm. 1 However, these metal oxides also have disadvantages. While there is not scientific consensus over the ability of ZnO to permeate through the skin, studies have shown potentially problematic increases of Zn 2+ in blood and urine following sunscreen application to healthy skin.…”