167 UV FILTERS IN SUNSCREEN PRODUCTS primary cause of these photobiologic consequences. As a result, UV filters in sunscreens have become more popular as a photoprotection technique over the last decade. The most extensively used UVB filter in sunscreens is OMC, also known as ethylhexylmethoxycinnamate or octinoxate (see Figure 1). Due to its potential risks of DNA damage (3–4) associated with the demonstrated endocrine disruptor effects (5) in humans, the safety of this organic filter is a current health concern. When exposed to light, the UVB filter becomes photo unstable due to the UV-absorbing ingredients of sunscreen. Antioxidants have a potential to neutralize UV-induced free radicals (6–7) so their use as UV filter stabilizers is a novel photoprotective strategy (8). OMC is present in more than 85–95% of personal care products, including sunscreens. Depending on the mode of action, sunscreens can be classified into physical sunscreens (i.e., zinc oxide and titanium dioxide, which stay on the surface of the skin and mainly deflect [9] UV light) or chemical sunscreens (i.e., UV organic filters, which absorb the UV light). On the other hand, benzophenone-3 is a chemical sunscreen agent that absorbs UV-B and short-length UV-A rays (280–350 nm) with its peak protection at 288 nm. It is highly stable, unlike many other chemical sunscreens (10), but its UV-absorbing powers are poor and it must always be coupled with additional sunscreen agents for effective protection. It is often utilized as a photo stabilizer rather than a true sunscreen agent, as it can effectively protect formulations from UV damage. The safety of benzophenone-3 is a sensitive subject. Its molecules are tiny (228 Da) and exceedingly lipophilic (oil-loving), resulting in excellent absorption, and it is optimal to have sunscreens on the skin’s surface, not in the bloodstream, therefore this is a concern for Benzophenone-3. In fact, it absorbs so well that it may be detected in urine 4 hours after applying a sunscreen cream containing benzophenone-3. Figure 1. Chemical structures of four UV filters (19).

168 JOURNAL OF COSMETIC SCIENCE Avobenzone (butyl methoxydibenzoylmethane) is an oil-soluble ingredient used in sunscreen products to absorb the full spectrum of UVA rays and offers protection from both UVA and UVB rays. The maximum absorption wavelength of avobenzone is 357 nm, and it can absorb UV light over a wider range of wavelengths than many other sunscreen agents. When avobenzone is exposed to the sun for 30 minutes, it completely degrades, providing very little protection to persons who are exposed to the sun for long periods of time. As a result, it is combined with octocrylene, which is exceptionally stable and gives hours of sun protection when combined with avobenzone. Octocrylene, also known as octocrilene, is an organic UV filter that absorbs mostly UVB and short UVA wavelengths. However, the amount of this component in most recipes is kept to no more than 10% or 12%. Octocrylene is a photo stable UVB filter that is oil-soluble, liquid, and has excellent dissolving characteristics. UVB and short-wave UVA photons with wavelengths in the range of 280–320 nm are absorbed by the conjugated acrylate component, protecting (11– 12) the skin from direct DNA damage. There are many methods reported for UV filters in sunscreen such as spectrophotometry (11), high performance thin layer chromatography (13), HPLC (14–18) (this method is less time consuming), and single run analysis. EXPERIMENTAL MATERIALS AND REAGENTS Working reference standards of avobenzone, octinoxate, octocrylene and benzophenone-3 and HPLC grade methanol and chloroform were purchased from Merck Limited (Merck Life Science Private Limited, Mumbai, India). The 0.45 μm PTFE and nylon syringe filter were procured from AXIVA (Axiva Sichem Pvt. Ltd., Sonipat, Haryana -131028, India). Water for HPLC was generated using a Milli-Q water purification system (Merck Millipore, Milford). CHROMATOGRAPHIC CONDITIONS AND EQUIPMENT Equipment used consisted of a UFLC-SHIMADZU system (Lab Solutions, Shimadzu Analytical (India) Pvt. Ltd., Mumbai, India), XS105 dual range balance (Mettler Toledo India Pvt. Ltd., Mumbai, India), a 20 µL injection loop and Nexera liquid chromatograph LC-30AD and SPD-M20A Prominence diode array detector, column oven CTO-20A, and degassing unit DGU-20A 3R . All chromatographic experiments were performed in the isocratic mode. Separation was achieved on a stationary phase of Baker bond Q2100 C 18 (250 × 4.6 mm, 5 µm in particle size) column by using a mixture of methanol and water (90:10 vol/vol) as the mobile phase. The run time was 25 min at room temperature and the mobile phase was pumped at a flow rate of 0.7 mL/min, while the eluents were monitored at 303 nm. The column was equilibrated by pumping the mobile phase through the column for 20 minutes before the injection. PROCEDURE Standard solution preparation. Twenty-five mg each of the following reference standards were weighed into a 100-ml volumetric flask: avobenzone, octinoxate, octocrylene and benzophenone-3. Two mL of chloroform were added to dissolve the analytes and 20 mL