Subcritical water chromatography (SBWC) refers to a new reversed‐phase liquid chromatography (RPLC) technique where high‐temperature water is used as the sole mobile phase component. The major advantage of SBWC is the elimination of toxic mobile phase organic solvents required in traditional RPLC. These organic solvents are not only expensive in terms of purchasing price but also costly in their waste disposal. Therefore, the SBWC technique offers both economical and environmental benefits. Additional advantages of SBWC are fast analysis time; temperature‐dependent efficiency, selectivity, and resolution; temperature‐programmed elution; and ability to accommodate both gas‐ and liquid‐phase detectors. Most importantly, after years of academic studies, industry started paying attention to this economical and green separation technique. For example, Procter & Gamble has recently funded an SBWC project in developing green SBWC methods for the analysis of skincare products.

Triclosan (TCS), an antimicrobial chemical with potential endocrine-disrupting properties, may pose a risk to early embryonic development and cellular homeostasis during adulthood. Here, we show that TCS induces toxicity in both the nematode C. elegans and human mesenchymal stem cells (hMSCs) by disrupting the SKN-1/Nrf2-mediated oxidative stress response. Specifically, TCS exposure affected C. elegans survival and hMSC proliferation in a dose-dependent manner. Cellular analysis showed that TCS inhibited the nuclear localization of SKN-1/Nrf2 and the expression of its target genes, which were associated with oxidative stress response. Notably, TCS-induced toxicity was significantly reduced by either antioxidant treatment or constitutive SKN-1/Nrf2 activation. As Nrf2 is strongly associated with aging and chemoresistance, these findings will provide a novel approach to the identification of therapeutic targets and disease treatment.

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The solubility of methyl, ethyl, and butyl parabens (4-hydroxybenzoate) in water was determined at (298, 373, 423, and 473) K using a homemade heating/mixing system and by high performance liquid chromatography analysis. The solubility increased for all three parabens studied when water temperature was raised from 298 K to 423 K. However, the solubility decreased with a further temperature increase from 423 K to 473 K. This was due to the degradation of parabens at 473 K as revealed by a separate study. A new model was developed to guide the estimation of paraben solubility in subcritical water. The solubility values predicted using this new model compare reasonably well with our experimental values. ■ INTRODUCTIONSubcritical water has been used as a green separation fluid for both extraction 1−5 and chromatography. 6−9 Recently, chromatographic separations of preservatives, sunscreens, and niacinamide in skincare products using subcritical water as the mobile phase have been reported. 10−12 However, organic solubility in subcritical water is largely unknown. To promote and develop green subcritical water extraction and chromatography technologies, fundamental data such as the solubility of analytes in water at elevated temperatures are critically needed.In this work, we studied the solubility of methyl, ethyl, and butyl parabens (4-hydroxybenzoate) in water at temperatures ranging from 298 K to 473 K. A homemade system was used to carry out the solubility experiments. The experimental solubility data of this work was then compared with values predicated using existing solubility models. 13−15 Unfortunately, none of these models 13−15 yields favorable predictions for solubility of all three paraben studied. Thus, we developed a new model that can reasonably predict the solubility of parabens in hightemperature water.

In this study, high-temperature liquid chromatographic (HTLC) and subcritical water chromatographic (SBWC) separations of sunscreens contained in skincare creams were achieved at temperatures ranging from 90 to 250°C. The columns employed in this work include a ZirChrom-DiamondBond-C18, a XTerra MS C18 and a XBridge C18 column. The quantity of methanol consumed by the greener HTLC sunscreen methods developed in this project is significantly reduced although the HTLC separation at this stage is not as efficient as that achieved by traditional HPLC. SBWC separation of sunscreens was also achieved on the XTerra MS C18 and the XBridge C18 columns using pure water at 230-250°C. Methanol was eliminated in the SBWC methods developed in this study.