K2so4

Adult I. scapularis were acquired from BEI Resources (American Type Culture Collection) and the National Tick Research and Education Resource (Oklahoma State University). Groups of 10–12 ticks were housed in 20 ml glass scintillation vials (VWR International, PA, USA) fitted with strips of paper towel as refuge and substrate for climbing, and with a mesh-covered hole (approx. 1 cm) in the lid to enable air exchange. As ticks are prone to desiccation, vials were kept at high relative humidity (85–95%) in a vessel (d = 26 cm, h = 30 cm) containing a saturated solution of K₂SO₄ (99% purity; Alfa Aesar, ON, Canada). To minimize the risk of tick escape, the vessel was retained in a plexiglass box (50 × 35 × 35 cm) which was kept at 22°C and a 14 : 10 light/dark cycle. To prevent mould/fungal growth, vials were washed weekly with Sparkleen (Thermo Fisher Scientific, MA, USA) and dried at 100°C for more than 1 h. Monthly, the vessel was washed and sterilized with Sparkleen and 70% ethanol, respectively, and the K₂SO₄ solution was replaced.

Unless noted otherwise, the following chemicals were used as received: NiSO₄·5H₂O (Sigma Aldrich, 99–102.0%), L-ascorbic acid (Sigma Aldrich, 99%), CuSO₄·5H₂O (Fisher Scientific, technical grade), AgNO₃ (Sigma Aldrich, 99.0%), FeSO₄·7H₂O (Sigma Aldrich, 98%), Fe₂(SO₄)₃·5H₂O (Sigma Aldrich, 97%), K₂SO₄ (Alfa Aesar, 98.0%), concentrated HNO₃ (Fisher Scientific, certified ACS plus), and concentrated H-₂SO₄ (Mallinckrodt Chemicals, 95–98%). All aqueous electrolytes were prepared with high purity deionized (DI) water.

The electrolytes were prepared by either dissolving redox-reactive or electrochemically inert salts in 18.2 MΩ water. The salts were obtained as follows: KI (99%, Alfa Aesar), KBr (99.999%, Alfa Aesar), MVCl₂ hydrate, MVCl₂ (98%, Sigma Aldrich), HV dibromide, HVBr₂ (98%, TCI AMERICA), K₂SO₄ (99.99%, Alfa Aesar), K₄[Fe(CN)₆·3H₂O] (Mallinckrodt) and Ru(NH₃)₆Cl₃ (99%, Strem Chemicals). Co(bpy)₃Cl₂ was prepared by literature methods66 (link).