Magnesium sulphate

Acetonitrile (ACN, analytical grade), methanol (MeOH, LC-MS grade), acetic acid and C18 bulk sorbent were purchased from J.T. Baker of Avantor Performance Materials (Netherlands). Formic acid and ammonium acetate (LC/MS grade) were supplied by Sigma-Aldrich (Germany). Magnesium sulphate was obtained from Chempur (Poland). Water was purified by a Milli-Q apparatus (USA).

Pure standards of tributyltin chloride TBT (96%), triphenyltin chloride TPhT (95%) and internal standard deuterated tributyltin chloride–d27 TBT-d27 (96%) were purchased from Sigma Aldrich (St. Louis, MO, USA). HPLC gradient–grade methanol, acetonitrile and formic acid 98% were purchased from Merck (Darmstadt, Germany). Quechers salts: Magnesium sulphate, sodium chloride, sodium acetate, ammonium acetate were purchased from Chempur (Piekary Śląskie, Poland), trisodium citrate was purchased from Avantor (Gliwice, Poland) and disodium citrate was purchased from Acros Organics (Morris Plains, NJ, US). Sorbents, silica functionalized with primary–secondary amine (PSA) and octadecyl groups were purchased from Agilent Technologies (Santa Clara, CA, USA). Certificated Reference Material BCR^® 646 was purchased from Merck (Darmstadt Germany). Ultrapure water was obtained from a Millipore water purification system (MiliQ, Billerica, MA, US) equipped with UV-lamp (resistivity of 18.2 MΩ.cm (at 25 °C) and a TOC value below 5 ppb).