Sodium phosphate monobasic

Dopamine and 2-aminophenol were purchased from Alfa Aesar (Ward Hill, MA, USA). Sodium phosphate monobasic was received from Fisher Scientific (Waltham, MA, USA) and catechol was obtained from Acros (Geel, Belgium). All chemicals were used as received. The background electrolyte (10 mM phosphate buffer) was prepared weekly by dissolving the desired amount of solid NaH₂PO₄. The pH of the solutions was adjusted, when necessary, using either 1 mol·L⁻¹ NaOH or 1 mol·L⁻¹ HCl (Fisher Scientific) and measured using a glass electrode and a digital pHmeter (Orion 420A+, Thermo; Waltham, MA). Stock solutions of Dopamine, 2-aminophenol and catechol (10 mM each) were prepared by dissolving the desired amount of each compound in ultrapure water (≥ 18 MΩ·cm, NANOpure Diamond, Barnstead; Dubuque, Iowa). Working solutions were prepared by diluting the stock solutions in 10 mM phosphate buffer. Standard-grade PMMA plates (150 × 70 × 1.5 mm) were purchased from Gravograph (Duluth, GA, USA) and used to produce the microdevices herein described. Sylgard 184 silicone elastomer and curing agent were obtained from Dow Corning. Sugar, used for the formation of the PDMS sponge (decoupler), was food-grade and acquired in a local grocery store.

The primary reference materials for fentanyl, norfentanyl, acetyl fentanyl, acetyl norfentanyl, and their respective internal standards (ISTD) fentanyl-d₅, norfentanyl-d₅, acetyl fentanyl-¹³C₆, and acetyl norfentanyl-¹³C₆ were purchased from Cerilliant (Round Rock, Texas). Ammonium formate, ammonium hydroxide, glacial acetic acid, isopropanol, methylene chloride, methanol, sodium phosphate monobasic, sodium phosphate dibasic and deionized (DI) water were purchased from Fisher Scientific (Hanover Park, Illinois). All reagents were ACS grade or better. SPEC® MP3 solid phase extraction (SPE) columns were purchased from Agilent Technologies, Inc, (Santa Clara, California). Medical grade nitrogen was purchased from National Welders Supply Company (Richmond, Virginia). Drug-free expired whole blood was obtained from Transfusion Medicine Laboratory at Virginia Commonwealth University Health System. The blood was certified drug free by screening for alkaline extractable drugs by GC/MS and UPLC/MS/MS prior to use.

Ketoconazole (lot # BS1203355108, 98% purity) was purchased from Bosche Scientific (New Brunswick, NJ) and used as received. Adipic acid (lot # 06807BE, 99% purity), succinic acid (lot # 037K0021, 99% purity), fumaric acid (lot # 09426EE, 99+% purity), acetic acid (lot # 074K3658, 99%), sodium acetate anhydrous (lot # 100K0272), dipotassium hydrogen phosphate (lot # 103H0287, ACS reagent), and sodium chloride (lot # 094K0183, ACS reagent) were purchased from Sigma-Aldrich (St. Louis, MO) and used as received.
HPLC grade methanol, HPLC grade 2-propanol, sodium phosphate monobasic (lot # 017316), and hydrochloric acid (lot # 2AJK15038, ACS grade) were purchased from Fisher Scientific (Fair Lawn, NJ). Acetone (ACS reagent 99.5%) and phosphoric acid (lot # B0506524, 85+%) were purchased from Acros Organics (NJ) and used as received. Trifluoroacetic acid (spectrophometric grade, 99%) was purchased from Aldrich Company (Milwaukee, WI). NaOH (pellets) was purchased from J.T. Baker (Philipsburg, NJ). Water used in this study was filtered through a double deionized purification system (Milli Q Plus Water System) from Millipore Co. (Bedford, MA).

Dextrose, sodium phosphate monobasic, sodium tetraborate, and HEPES were from Fisher Scientific (Pittsburgh, PA). Cosmic Calf Serum was from HyClone Laboratories (South Logan, Utah). Sodium hydroxide (NaOH) was purchased from EMD Chemicals (San Diego, CA). ACN was from Avantor Performance Materials (Center Valley, PA). Collagenase P was obtained from Roche Diagnostics (Indianapolis, IN). RPMI 1640 was from Mediatech (Manassas, VA). Gentamicin was from Lonza (Walkersville, MD). All other chemicals were from Sigma-Aldrich (St. Louis, MO) unless otherwise noted. All solutions were made with ultrapure DI water (NANOpure® Diamond system, Barnstead International, Dubuque, IA).

The reagents used to synthesize the various cationic nanogels have thoroughly been described [25 (link),26 (link)]. In addition, tetrahydrofuran, acetone, hydrochloric acid, sodium hydroxide, sodium phosphate monobasic, and sodium phosphate dibasic heptahydrate were purchased from Fisher Scientific.