Florisil

Acetone and diethyl ether were of p.a. grade, ACS+ISO+Ph. Eur (Honeywell Specialty Chemicals Seelze GmbH, Germany). Dichloromethane and petroleum ether were of per analysis grade, ACS+ISO (Honeywell Specialty Chemicals Seelze GmbH, Germany). Sodium sulphate (POCH, Gliwice, Poland) was baked at 550 °C for 7 h. Florisil (Sigma–Aldrich Sp. z o.o., Poznań, Poland) was activated by a bake-out at 130–135 °C for 7 h and then stored in a desiccator before use. A high-purity certified standards of insecticides were purchased from Ehrenstorfer (Augsburg, Germany). Stock solutions of approximately 1000 μg/mL in acetone were prepared. Intermediate standards (10 μg/mL) were prepared by dilution with acetone. The stock and the intermediate standards were stored at −16 °C. Working standards were prepared by diluting the intermediate standard with appropriate volumes of acetone (for spiking experiments) or with an extract of blank apple matrix (for GC calibration), and then stored at 4 °C.

The captan standard was purchased from Dr. Ehrenstorfer (Augsburg, Germany). All reagents were of sufficiently high purity for GC analysis. Acetonitrile, acetone, and petroleum ether were purchased from Honeywell Specialty Chemicals Seelze GmbH (Seelze, Germany). Anhydrous magnesium sulphate, sodium chloride, and tri-sodium citrate dihydrate were from Chempur (Piekary Slaskie, Poland). Sodium citrate dibasic sesquihydrate was purchased from Sigma-Aldrich (Steinheim, Germany). As for the sorbents, PSA was purchased from Supelco (Bellefonte, PA, USA), Al₂O₃, ZrO₂, SiO₂ were from POCH (Gliwice, Poland) and Florisil^® was from Sigma-Aldrich (St. Louis, MO, USA).

High-purity (> 97.0) etofenprox, flubendiamide, and tebufenozide standards were supplied by Dr. Ehrenstorfer GmbH (Ausgburg, Germany). Stock solutions (1000 mg/L) of these standards were prepared by dissolving them in HPLC-grade acetonitrile (J.T. Baker, Center Valley, PA, USA). HPLC-grade acetonitrile, acetone, and n-hexane (all from J.T. Baker) were used for residue extraction and cleanup. Anhydrous sodium sulfate was purchased from Junsei Chemical (Tokyo, Japan). Florisil was purchased from Sigma-Aldrich (St. Louis, MI, USA) and used as an adsorbent for open column chromatography.

Optical rotations were determined on a PerkinElmer 343 polarimeter (Waltham, MA, USA). IR spectra were recorded using an Equinox 55 spectrophotometer (Bruker, Bremen, Germany). ¹H and ¹³C NMR spectra were recorded on a Bruker Avance III 700 spectrometer (Bruker BioSpin, Bremen, Germany) at 700.13 and 176.04 MHz, respectively, with chemical shifts referenced to the respective residual solvent signal (δ_H 7.21/δ_C 123.5 for C₅D₅N). The HRESIMS spectra were recorded on a Bruker Impact II Q-TOF mass spectrometer (Bruker, Bremen, Germany); the samples were dissolved in MeOH (at 0.001 mg/mL). HPLC separations were carried out on an Agilent 1100 Series chromatograph (Agilent Technologies, Santa Clara, CA, USA) equipped with a differential refractometer; the columns used were as follows: Diasfer-110-C18 (10 µm, 250 × 15 mm, Biochemmack, Moscow, Russia), Discovery C₁₈ (5 µm, 250 × 4 mm, Supelco, North Harrison, PA, USA), and YMC-Pack Pro C18 (5 μm, 250 × 4.6 mm, YMC Co., Ltd., Kyoto, Japan). Low-pressure liquid column chromatography was carried out on Polychrome 1 (powdered Teflon, 0.25−0.50 mm; Biolar, Olaine, Latvia), Florisil (60–100 µm, Sigma-Aldrich Co., St. Louis, MO, USA), and Si gel KSK (50–160 µm, Sorbpolimer, Krasnodar, Russia) columns. Sorbfil Si gel plates (4.5 × 6.0 cm, 5–17 µm, Sorbpolimer, Krasnodar, Russia) were used for thin-layer chromatography (TLC).

Optical rotations, Perkin-Elmer 343 polarimeter (PerkinElmer, Waltham, MA, USA). NMR spectra, Bruker Avance III 700 spectrometer (Bruker BioSpin, Bremen, Germany) at 700.13 MHz (¹H)/176.04 MHz (¹³C), internal standard CD₃OD at δ_H 3.30/δ_C 49.0. HRESIMS spectra, Bruker Impact II Q-TOF mass spectrometer (Bruker, Bremen, Germany); sample concentration in MeOH 0.001 mg/mL. HPLC, Agilent 1100 Series chromatograph (Agilent Technologies, Santa Clara, CA USA) with a differential refractometer; columns Discovery C18 (5 µm, 10.0 × 250 mm, Supelco, Bellefonte, PA, USA) and YMC-Pack Pro C18 (5 µm, 10.0 × 250 mm and 4.6 × 250 mm, YMC Co., Ltd., Kyoto, Japan). LPLC, column sorbents Polychrom 1 (powdered Teflon, 0.25–0.50 mm, Biolar, Olaine, Latvia), Si gel KSK (50–160 µm, Sorbpolimer, Krasnodar, Russia), and Florisil (60–100 µm, Sigma-Aldrich, Co., St. Louis, MO, USA).