Agilent 6540 q tof ms

The purity of each peak fraction obtained by HSCCC was determined by NMR using internal standard method. The internal standard solution was prepared by dissolving a certain amount of hydroquinone with deuterated methanol (MeOD) giving a concentration of 0.02 mol/L. The fraction of about 1 mg was accurately weighed and dissolved in the hydroquinone internal standard solution. NMR spectra was recorded, the peak area ratio between the selected proton peak of the hydroquinone and that of the fraction was measured to calculate the purity of the fraction. Structural identification of each peak fraction was carried out by analyzing their MS and nuclear magnetic resonance (NMR) spectra. High resolution electrospray ionization MS (HR-ESI-MS) analyses were recorded with Agilent 6540 Q-TOF MS (Santa Clara, CA, USA). NMR spectra were recorded on Bruker Ascend 600 spectrometer equipped with cryogenic probe (Karlsruhe, Germany).

The Agilent 1290 UPLC (Agilent Technologies, Santa Clara, CA, USA) was used to perform the chromatographic separation. The UV spectrum was recorded between 190–380 nm; the UV detector was set at 254 nm. An Agilent ZORBAX SB-C18 (4.6 × 150 mm; i.d. 5.0 mm) column using a gradient elution (methanol (A)/water (0.5% HCOOH) (B)) was chosen. All of the MS experiments were conducted on an Agilent 6540 Q-TOF-MS equipped with electrospray ionization (ESI) interface (Agilent Technologies, USA).
The gradient condition was 0–80 min at 5–100% A. The column temperature was set at 25 °C, the flow rate was kept at 1 mL/min, and the injection volume was 2 μL. The MS analysis was performed in negative scan modes under the following operation parameters: the voltage was set at 160 V. Full scan data acquisition and dependent scan event data acquisition were performed from m/z 100–1200.

Standards of imidacloprid, acetamiprid, clothianidin, thiamethoxam and dinotefuran were prepared at a concentration of 10 mg L^-1 in methanol. Solutions were photo-treated under UV irradiation, and a darkness control was established. Samples were then filtered using a membrane filter with a pore size of 0.22 μm and analyzed using LC-Q-TOF-MS equipped with diode array detection.
LC separations were carried out in an Agilent 6540 Infinity II series LC system (Agilent Technologies, Santa Clara, CA) equipped with an Agilent Eclipse Plus C₁₈ column (2.1 mm × 150 mm, 1.8 μm). Mobile phase A was acetonitrile, mobile phase B was ultra-pure water; the elution gradient was as follows: 0–4 min, 25% A; 4–7 min, 25–80% A; and 7–10 min, 80–25% A. The flow rate, column temperature and injection volume were 250 μL min⁻¹, 25°C and 2 μL, respectively. An Agilent 6540 Q-TOF-MS (Agilent Technologies, Santa Clara, CA) equipped with an automatic jet stream electrospray ionization (AJS-ESI) interface was employed for assay development. The typical ion source parameters were as follows: capillary voltage, +4000/-3500 V; nozzle voltage, +500/-500 V; gas temperature, 300°C; gas flow rate, 5 L min⁻¹; sheath gas temperature, 250°C; sheath gas flow rate, 11 L min⁻¹; and nebulizer pressure, 45 psi.