Sodium dihydrogen phosphate dihydrate

The brown seaweed Undaria pinnatifida stem was collected from Kesennuma, Miyagi prefecture, Japan, and the harvest time is the middle of April.
High-purity carbon dioxide gas (99%) was supplied by Showa Denko Gas Products Co., Ltd. (Kawasaki, Japan). The amylose B and α-amylase from Bacillus sp. and glucoamylase for Rhizopus sp. were purchased from Nacalal Tesque, Inc. (Kyoto, Japan). Fucoxanthin standard (≥ 98% purity), sodium dihydrogen phosphate dihydrate (≥ 99% purity), disodium hydrogen phosphate 12-water (99% purity), 1 mol/L sodium hydroxide solution, iodine (99.8% purity), and potassium iodide (99.5% purity) were purchased from Wako Pure Chemical Industries, Ltd. (Osaka, Japan). Milli-Q water was used in these experiments. All reagents used in this study were analytical or high-performance liquid chromatography (HPLC) grade.

PA21 (Vifor Pharma, Glattbrugg, Switzerland), lanthanum carbonate hydrate (Alfa Aesar, Lancashire, UK), sevelamer hydrochloride (AK Scientific, Inc., Union City, CA, USA), calcium carbonate (FUJIFILM Wako Pure Chemical Corporation, Osaka, Japan), and ferric citrate hydrate (Nacalai Tesque, Inc., Kyoto, Japan) were used for the experiments. For the in vivo studies, each investigational drug was dissolved or suspended in 0.5% (w/v) methylcellulose (MC) solution (FUJIFILM Wako Pure Chemical Corporation). After phosphate (FUJIFILM Wako Pure Chemical Corporation), disodium hydrogen phosphate dodecahydrate (FUJIFILM Wako Pure Chemical Corporation), and sodium dihydrogen phosphate dihydrate (FUJIFILM Wako Pure Chemical Corporation) were diluted or dissolved in distilled water, the resulting phosphate solution was mixed and adjusted to pH 2, 3, 4, 5, 6, 7, or 8 [16 (link)], simulating the conditions in the digestive tract.

The device performance, including the transfer curves (drain–source current I_DSversus gate-source voltage V_GS), was characterized using a semiconductor device parameter analyzer (B1500A, Keysight). The transfer curves were recorded at a fixed drain-source voltage (V_DS = 0.1 V) and by varying the gate-source voltage (V_GS = 0–1 V) at a sweeping rate of 0.01 V s⁻¹. Solutions of free chlorine were freshly prepared by diluting sodium hypochlorite pentahydrate, NaClO·5H₂O (Tokyo Chemical Industry Co. Ltd, Japan), in DI water and their NaClO concentrations were standardized using a photometric free chlorine meter (AQUAB AQ-202P, SIBATA Scientific Technology Ltd, Japan). Phosphate buffer solution (PBS) was prepared with sodium dihydrogen phosphate dihydrate and disodium hydrogen phosphate (FUJIFILM Wako Pure Chemical Corp., Japan). The electrochemical properties were evaluated by cyclic voltammetry and electrochemical impedance spectroscopy measurements using an Autolab PGSTAT204 potentiostat/galvanostat system equipped with an impedance analyzer FRA32M (Metrohm, Utrecht, The Netherlands).

Norfloxacin (NFLX), ofloxacin (OFLX), tosufloxacin tosylate monohydrate (TFLX), calcium dichloride, magnesium dichloride, iron(II) dichloride tetrahydrate, iron(III) chloride hexahydrate, aluminum(III) chloride hexahydrate, zinc chloride, lanthanum chloride heptahydrate, 1-octanol, sodium dihydrogen phosphate dihydrate, sodium chloride, sodium hydroxide, decane, 8 M NaOH, and 0.1 vol% trifluoroacetic acid-acetonitrile were purchased from Wako Pure Chemical Industries, Ltd (Osaka, Japan). Ciprofloxacin hydrochloride monohydrate (CPFX), levofloxacin (LVFX), enoxacin sesquihydrate (ENX), fleroxacin (FLRX), and prulifloxacin (PUFX) were purchased from TCI (Tokyo, Japan). Gatifloxacin (GFLX) and sparfloxacin (SPFX) were purchased from Funakoshi Co., Ltd (Tokyo, Japan). Moxifloxacin (MFLX) was purchased from Combi-Blocks Inc. (San Diego, USA). 2-Morpholinoethanesulfonic acid (MES) was purchased from Dojindo laboratories (Tokyo, Japan). 0.1 vol% trifluoroacetic acid-distilled water was purchased from Kanto chemical co., inc (Tokyo, Japan). Soybean lecithin was provided by Tsuji Oil Mills co., Ltd (Mie, Japan) (SLP-White, phosphatidylcholine (24-32 %), phosphatidylethanolamine (20-28 %), phosphatidylinositol (12-20 %), phosphatidic acid (8-15 %), and lysophosphatidylcholines (1-5 %) (based on the product information provided by the manufacturer)).