Dpd total chlorine reagent powder pillows

All solutions were prepared using >18 MΩ-cm deionized water from an Evoqua water purification system. PAA solution (32% w/w of PAA, 40–45% w/w of acetic acid, and <6% w/w of H₂O₂), HP solution (30.9% w/w), and Tygon tubing were supplied by Sigma Aldrich (St. Louis, MO). A V-2000 photometer and PAA and HP Vacu-vials instrumental test kits (K-7913, K-5543) were purchased from Chemetrics (Midland, VA). A DR1900 portable spectrophotometer and DPD total chlorine reagent powder pillows were purchased from HACH (Loveland, CO). 50-mL glass impingers were purchased from Ace Glass (Vineland, NJ). Plastic impingers were purchased from SKC Inc. (Eighty Four, PA). 25 mm Acrodisc syringe filters with 0.45 μm PTFE membranes were purchased from Pall Corporation (Port Washington, NY). The 3D printed nozzle was printed using an Objet Eden 260vs 3D printer with Veroclear and SUP 705 was used as support material. The support material was washed away before experimental use. Flow-limiting critical orifices (1 L/min) and Aerosol Adapter connectors were purchased from Millipore (St. Louis, MO). A Bios DryCal Defender flowmeter from Mesa Labs (Lakewood, CO) was used to measure the orifice flow rate.