*4.2. HRW Production*

As shown in Figure 5, the control water (control group) was filtered from tap water (Taitung, Taiwan) by passage through a calcined ceramic filter, an activated carbon filter, and a magnetized rod (purchased from Japin biotech company, Taitung, Taiwan). The whole water devices are certified by the National Sanitation Foundation (NSF)/American National Standards Institute (ANSI) standards No. 42 (Filters are certified to reduce aesthetic impurities such as chlorine and taste/odor.), No. 53 (Filters are certified to reduce a contaminant with a health effect, which are set in this standard as regulated by the U.S. Environmental Protection Agency (EPA) and Health Canada.), and No. 401 (Treatment systems that have been verified to reduce one or more of 15 emerging contaminants, which can be pharmaceuticals or chemicals not yet regulated by the EPA or Health Canada, from drinking water (http://www.nsf.org/consumer-resources/water-quality/water-filters-testing-treatment/ standards-water-treatment-systems)). The HRW was obtained from the same water apparatus except that the tap water was passed through the first two filters and then reacted with the magnesium–carbon hydrogen storage hybrid materials (Kuraray Co., Ltd., Japan) in the third device. The resulting HRW was then passed through an activated carbon filter and magnetized rod at a flow rate of 2 L/min.

**Figure 5.** Schemes of the manufacturing process for control water and HRW from tap water: 1. Calcined ceramic filter; 2. activated carbon filter; and 3. magnesium–carbon hydrogen storage hybrid materials. Water reacted with this material and then release stable H2 gas; 4. activated carbon filter; 5. magnetized rod.

#### *4.3. Determinations of the Quality of HRW*

The dissolved H2 in fresh HRW was measured with an ENH-1000 electrode (TRUSTLEX Inc, Osaka, Japan), and the oxidation-reduction potential (ORP) value was determined by use of an MP-103 electrode (Gondo Electronic Co., Ltd. Taipei, Taiwan). The stability of dissolved H2 and ORP values in HRW was determined at various time points, including initial (0 h), 1, 2, 4, 8, 12, and 24 h, and at 4 ◦C and 25 ◦C, respectively (Figure 1).

The other water quality parameters, including pH, total dissolved solids (TDS), electrolytic conductivity (EC), and dissolved oxygen (DO), in the experimental drinking water were determined by use of electrode equipment with a bench-top water quality meter (Chi Jui Instrument Enterprise Co., Ltd., Taiwan) (Table 1). The concentrations of cations (Na+, K+, Ca2<sup>+</sup>, and Mg2<sup>+</sup>) and anions (Cl<sup>−</sup> and SO42<sup>−</sup>) in the water samples were determined by inductively coupled plasma-optical emission spectroscopy (ICP-OES) (HORIBA Jobin Yvon Longjumeau, France). It is known that water quality can be influenced by ions (e.g., Na+, K+, Ca2+, Mg2+, Cl−, NO3−, and SO42<sup>−</sup> are commonly found in natural water), pH, and TDS in water and that these variables have an important influence on human health. The above water parameters can affect water clusters by the interaction of water molecules and ions or the formation of clusters of ion–water and water–water, which can change the physical properties of water (e.g., melting point) [14]. To estimate the water clustering of control water and HRW, 17O nuclear magnetic resonance (NMR) line-width was measured to estimate median water cluster size [14]. The wider the 17O NMR line-width, the larger the water cluster size. In this study, water samples were characterized by 17O NMR spectroscopy (Bruker 500 MHz NMR, Varian Inova, Canada). The sample (700 μL) was mixed in a 5-mm NMR spectroscopy tube and analyzed under the following conditions: 67.80 MHz, 0.202-s sampling time, 10162.6-Hz bandwidth, 4096 scans, 90◦ flip angle, 0.2-s relaxation delay, and room temperature (25 ◦C).
