Liquid chromatography mass spectrometry lc ms grade water

The sample labelling procedure for CE-SDS LIF analysis was based on the protocol described by SCIEX (Framingham, MA, USA) [25 ]. For the purity evaluation analysis, 10 µL of each virus sample was mixed with 2 µL of an aqueous solution with 4% SDS (Life-Technologies) and 150 mM N-Ethylmaleimide (NEM) (Sigma-Aldrich, Burlington, MA, USA) and incubated at 70 °C for 5 min, for denaturation. After that, the ATTO-TAG™ FQ Amine-Derivatization Kit (Life Technologies, Carlsbad, CA, USA) was used to label the samples. A volume of 2.5 µL of FQ dye at a concentration of 2.5 µM and 1 µL of the nucleophile KCN solution (30 mM) were added. After incubation at 70 °C for 10 min, 28 µL of an aqueous solution of 1% SDS was added to quench the labelling reaction, followed by another incubation for 5 min. Before injecting the sample into the CE LIF instrument, a dilution was performed with 40 µL of Liquid Chromatography-Mass Spectrometry (LC-MS) grade water (Fisher Scientific). To achieve higher resolution and sensitivity, the sample was desalted before being loaded into the analysis vials. This desalting step employed a 10 kDa cut-off filtration membrane (Amicon^® Ultra—10 kDa 0.5 mL centrifugal filters). The buffer exchange solution was composed of an aqueous solution of 0.1% SDS and 1.875 mM NEM. For this, two consecutive centrifugations of 10 min at 20,817× g were performed.

CAB, 3TC, and ABC were purchased from tert-Butoxycarbonyl (BOC) Sciences. RPV was purchased from Hangzhou Bingo Chemical Co., Ltd. Poloxamer 407 (P407), N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) buffer, ciprofloxacin, paraformaldehyde (PFA), and 3,3′-diaminobenzidine (DAB) were purchased from Sigma-Aldrich. Diethyl ether, endotoxin-free water, gentamicin, acetonitrile, methanol, KH₂PO₄, bovine serum albumin, Triton X-100, Liquid Chromatography Mass Spectrometry (LC-MS)-grade water, and TRIzol reagent were purchased from Fisher Scientific.