Accucore rp ms c18 column

Lipids were extracted from the extensor digitorum longus muscle (EDL) of young and aged mice. The mice were same as used in CE-TOFMS. LC-MS analysis was performed as described before^{7 (link)}, with slight modification. Namely, phospholipid fractions were analyzed using an LCMS-8040 triple–quadrupole mass spectrometer (Shimadzu, Kyoto, Japan) equipped with an electrospray source ionization probe. For high-performance liquid chromatography (HPLC) analysis, an Accucore RP-MS C18 column (2.6 μm, 2.1 × 50 mm, Thermo Fisher Scientific) was used. To quantify phosphatidylcholine (PC) and phosphatidylethanolamine (PE), multiple reaction monitoring was performed with the transitions [M + HCOO]− to [RCOO]− for PC, [M − H]− to [RCOO]− for PE. Peak areas of each individual species were normalized against the sum of all peak areas within each phospholipid class to determine the relative abundances (expressed as % of total). After applying autoscaling, mean-centering, and scaling by standard deviation on a per-peak basis as pretreatment, a principal component analysis (PCA) was conducted using JMP ver. 11 (SAS Institute, Cary, NC, USA).

A Dionex Ultimate 3000 RS UHPLC + focused system coupled with a TSQ Altis triple quadrupole mass spectrometer (MS/MS, Thermo Fisher Scientific, Austin, TX, USA) was used to detect residues of the seven neonicotinoids. Trace Finder software (version 4.1) was used for analysis, data acquisition, and reporting. An Accucore RP-MS C18 column (150 × 2.1 mm, 2.6 μm film thickness, Thermo Fisher Scientific) was used for separation at 40 °C. Mobile phase A was water, and mobile phase B was methanol; the flow rate was 0.30 mL/min. The gradient program of the mobile phase was 0–2 min 10% B, 2–6 min from 10% B to 90% B, 6–8 min 90% B, 8–8.1 min from 90% B to 10% B, and 8.1–16 min 10% B. The injection volume was 2 μL. To optimize the MS/MS parameters of the tested analytes (Table S1), a Harvard infusion pump (Harvard Apparatus, South Natick, MA, USA) was used. The precursor ions [M + H]⁺ were identified in the multiple reaction monitoring (MRM) mode using an electrospray ionization interface in the positive ion mode (H-ESI+). The MS conditions were as follows: the ion source temperature was set at 325 °C, the ion spray voltage was set at 3800 V, and the sheath and auxiliary gasses were 40 and 10 arb, respectively. Trace Finder (version 4.2) software was used for data acquisition.