1 chlorobutane

Polysulfone (PSU, Mw 35,000 Da in transparent pellet form, Sigma Aldrich, St. Louis, MO, USA), N,N-Dimethylformamide (DMF, 99% Fisher, Loughborough, UK), and 1-Methyl-2-pyrrolidone (NMP, 99% Acros Organics, New Jersey, NY, USA) were used for membrane preparation.
For the synthesis of 1-butyl-3-methylimidazolium chloride, 1-chlorobutane (99% Acros Organics, Geel, Belgium), 1-methylimidazole (99% Sigma-Aldrich, St. Louis, MO, USA), acetonitrile (CAN, 99.8% Fisher, Loughborough, UK), and ethyl acetate (99.9% VWR, Fontenay-Sous-Bois, France) were used. The task-specific ILs were prepared by the ion exchange process using Amberlite IRA-402(Cl) ion exchange resin (Alfa-Aesar, Kandel, Germany), Sodium hydroxide (NaOH, 97% Fisher, Geel, Belgium), and acidic compounds: benzoic acid (99% Acros Organics, New Jersey, USA), pivalic acid (99% Sigma-Aldrich, Steinheim, Germany), DL-proline (99% Sigma-Aldrich, St. Louis, USA), formic acid (99% Merck, Darmstadt, Germany), and malonic acid (99% Alfa-Aesar, Kandel, Germany)
The membrane gas solubility was evaluated with CO₂ (99.995%) and N₂ (99.999%) gases purchased from Linde (Barcelona, Spain).

Rotiphorese Gel B (MBAA) (2% w/w N,N′-methylenebis(acrylamide), Carl Roth, Karlsruhe, Germany), N,N,N′,N′-tetramethylethylenediamine (TEMED) (≥99.5%; Sigma Aldrich, St. Louis, MO, USA), ammonium persulfate (APS) (98%; Acros Organics, Fair Lawn, NJ, USA), 1-vinylimidazole (≥99%; Alfa Aesar, Haverhill, MA, USA), bromoethane (98%; Alfa Aesar), 1-chlorobutane (≥99%; Acros Organics), 1 bromobutane (99%; Sigma Aldrich), ethanol (EtOH) (≥99.8%), n-heptane (n-Hep) (≥99.5%), and tetrahydrofuran (THF) (≥99.8%) were used in this study. Additionally, ultrapure water was used throughout the study.

Reference standards, including 4-ethylmethcathinone (4-EMC), MDPV, 4-CEC, α-PVP, methylone, N-ethylpentylone, methedrone, ethylone, N-ethylhexedrone, butylone, dibutylone and mephedrone, were obtained as hydrochloride salts from Chiron (Surrey, UK). Deuterated IS MDPV-d₈ (hydrochloride) was obtained from Sigma-Aldrich (Dorset, UK). 4-MPD, 4-F-PHP, 4-chloro-α-pyrrolidinopropiophenone (4-Cl-α-PPP) and 4-Cl-α-PVP were kindly donated by TicTaC communications (London, UK) and test-purchased online and analyzed via high-resolution mass spectrometry (HRMS) for their identity. All reference and deuterated standards were obtained as methanolic solutions at 1.0 or 0.1 mg/mL, except for mephedrone, 4-MPD, 4-F-PHP, 4-Cl-α-PPP and 4-Cl-α-PVP (available as powder).
Ultra-pure water (18.2 MΩ cm) was generated in house using a Millipore water purification system. All solvents were HPLC grade unless otherwise stated. Methanol (MeOH) and acetonitrile (ACN) were obtained from Sigma-Aldrich (Dorset, UK). 1-Chlorobutane and sulfuric acid (≥95%) were both obtained from Thermo Fisher Scientific (Loughborough, UK).

Reference standards of 4-CEC, 4-EMC, butylone, dibutylone, ethylone, MDPV, mephedrone, methedrone, methylone, N-ethylhexedrone, N-ethylpentylone, and α-PVP were purchased from Chiron (Surrey, UK). 4-MPD, 4-F-PHP, 4-Cl-α-PPP, and 4-Cl-α-PVP were kindly donated by TicTaC communications (London, UK) and their structures were confirmed via high-resolution mass spectrometry (HRMS). Internal standard (IS) solution of MDPV-d₈ (0.1 mg/mL) was purchased from Sigma-Aldrich (Dorset, UK). All reference standards were obtained as methanolic solutions at 1.0 mg/mL, except for mephedrone, 4-MPD, 4-F-PHP, 4-Cl-α-PPP, and 4-Cl-α-PVP (1 mg of powder). Drug-free human whole blood (in 10 mL tubes) (containing K₂EDTA) was purchased from Cambridge Bioscience (Cambridge, UK).
Water was purified on a Milli-Q system (Burlington, MA, USA). All solvents were analytical or high-performance liquid chromatography (HPLC) grade. Methanol (MeOH) and acetonitrile (ACN) were obtained from Sigma-Aldrich (Dorset, UK). 1-Chlorobutane and sulphuric acid (≥ 95%) both were obtained from Thermo Fisher Scientific (Loughborough, UK).