Elix10 water purification system

Agilent’s Inorganic Anion Test Mixture stock (1000 ppm fluoride, chloride, bromide, nitrite, nitrate, sulfate, and 2000 ppm phosphate) was diluted 1:10 with deionized (DI) water obtained from EMD Millipore Elix10 Water Purification System (Darmstadt, Germany) and used as a standard. Stocks of the following inorganic anions (from their sodium or potassium salts) and organic acids (i.e., lactic acid) were made at 1000 ppm: acetate, arsenate, azide, bicarbonate/carbonate, bromide, chloride, fluoride, lactate, nitrate, nitrite, phosphate, silicate, sulfate, and thiosulfate. Each anion and organic acid was diluted from its stock solution to make a 20 ppm standard mixture and was filtered using a 0.22 μm PES syringe filter (Argos Technologies, Elgin, IL, USA). The running buffer/BGE was Agilent’s proprietary Basic Anion Buffer (pH 12.0) obtained from their Forensic Anion Solution Kit. The BGE was degassed for 10 min in a TA Instruments degassing station (New Castle, DE, USA) using 2 mL glass CE vials from Agilent Technologies prior to runs.

Agilent’s Cation Test Mixture stock (100 ppm each of ammonium, potassium, calcium, sodium, magnesium) was diluted to 25 ppm with DI water and 250 ppm lead from 1000 ppm stock of lead (chloride salt) dissolved in DI water obtained from EMD Millipore Elix10 Water Purification System (Darmstadt, Ger-many). The standard mixture was filtered using a 0.22 μm PES syringe filter (Argos Technologies, Elgin, IL, USA). The running buffer or BGE (background electrolyte) consisted of 15 mM imidazole, 8 mM malonic acid, 2 mM 18-crown-6 ether, 10% v/v MeOH with pH adjusted to 4.35 using 50% v/v acetic acid. All chemicals were dissolved in DI water. Buffer was filtered using 0.22 μm PES membrane syringe filter and degassed for 10 min using TA Instruments degassing station (New Castle, DE, USA) in 2 mL glass CE vials (Agilent Technologies) prior to runs.