All chemicals and solvents used for synthesis were purchased from commercial suppliers and applied directly in the experiments without further purification. The progress of the reaction was monitored by TLC on pre-coated silica plates (Merck 60F-254, 250 μm in thickness), and spots were visualized by UV light (254 nm). Merck silica gel (100–200 mesh) was used for general column chromatography purification. 1H NMR and 13C NMR spectra were recorded on a Bruker 400 spectrometer. Chemical shifts are reported in parts per million relative to internal standard tetramethylsilane (Si(CH3)4 = 0.00 ppm) or residual solvent peaks (DMSO-d6 = 2.50 ppm, 1H; 39.52 ppm, 13C). 1H NMR coupling constants (J) are reported in hertz (Hz), and multiplicity is indicated as the following: s (singlet), d (doublet), t (triplet), q (quartet), td (triplet doublet), dd (doublet of doublets), m (multiple). High-resolution mass spectra (HRMS) were obtained on an Agilent 6540 UHD Accurate-Mass Q-TOFLC/MS. The UV-Visible spectra were recorded on a UV-6000 UV-VIS-NIR-spectrophotometer (METASH, China).
6540 uhd accurate mass q tof lc ms
Manufactured by Agilent Technologies
Sourced in United States
The Agilent 6540 UHD Accurate-Mass Q-TOF LC/MS is a high-resolution, accurate-mass quadrupole time-of-flight liquid chromatography-mass spectrometry system. It provides precise mass measurement and data-dependent acquisition capabilities for the analysis of complex samples.
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Lab products found in correlation
C18 column, by Agilent Technologies (2 mentions)
Flash silica gel, by Merck Group (2 mentions)
400 spectrometer, by Bruker (1 mentions)
1290 uhplc, by Agilent Technologies (1 mentions)
Masshunter software, by Agilent Technologies (1 mentions)
Lc ms grade water, by ITW Reagents (1 mentions)
Ammonium acetate, by Merck Group (1 mentions)
Lc ms grade methanol, by Honeywell (1 mentions)
Ft nmr spectrometer, by Bruker (1 mentions)
Ftir 8300, by Shimadzu (1 mentions)
Avance 300, by Bruker (1 mentions)
Drx 500 nmr instrument, by Bruker (1 mentions)
Na2atp, by Merck Group (1 mentions)
Avance iiitm 400, by Bruker (1 mentions)
Spectrum two ftir, by PerkinElmer (1 mentions)
Micro cube elemental analyzer, by Elementar (1 mentions)
1290 infinity lc system, by Agilent Technologies (1 mentions)
Triglyceride determination kit, by Merck Group (1 mentions)
C18 reverse phase column, by Agilent Technologies (1 mentions)
16 protocols using 6540 uhd accurate mass q tof lc ms
1
Synthetic Characterization of Organic Compounds
2
Accurate-Mass QTOF LC-MS Profiling
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The LC–MS/MS was performed on an Agilent 6540 UHD Accurate-Mass QTOF LC–MS using an Agilent 1290 UHPLC as an inlet with UV detection at 210 nm prior to the mass spectrometer. Data acquisition and analysis were performed using Agilent MassHunter software. ESI was used in positive ion mode. Except for the injection volume (2 μL), LC conditions were the same as those used for UHPLC–UV analysis in Section 2.2.1 . The mass spectrometer was tuned in 2 GHz extended dynamic range mode (24,350 FWHM resolution at m/z 1521.9715) for accurate mass analyses. Mass accuracy was less than 0.2 ppm for reference masses across the mass range of m/z 100–1700. The mass range analyzed was m/z 100 –1200.
3
PFOA Extraction and Quantification Protocol
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LC–MS-grade methanol (from Honeywell) was used for extractions (including SPE cartridges preconditioning) and analyses. LC–MS-grade water (from PanReac Applichem) was used for HPLC–MS analyses and SPE cartridges preconditioning or washing. Ammonium acetate (from Aldrich) was used as an additive for HPLC eluents. Perfluorooctanoic acid analytical standard (> 98% from Aldrich) was used for LC–MS calibration curves and to obtain spiking solutions which were freshly prepared and checked for their PFOA content before each batch of analyses. SPE cartridges Strata TM-X-AW (33-µm polymeric weak anion 200 mg/6 mL tubes) were purchased from Phenomenex and used for PFOA extraction from seawater samples. PFOA-free polypropylene micropipette tips were used for quantitative small volume withdrawals. In order to prevent any type of PFOA contamination, the equipment used for sampling and extraction procedures was washed with the same methanol used for extraction and analysis. LC–MS analyses were performed using a 6540 UHD Accurate-Mass Q-TOF LC/MS (Agilent Technologies) equipped with a Dual AJS ESI source. Histograms, tabs, and statistical analysis have been realised using Excel 2016 (Microsoft) and PAST3 (Hammer et al. 2001 ).
4
Synthesis and Characterization of Peptide Compounds
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Nva-FMDP (F2) and Lys-Nva-FMDP (F3) were synthesized as described previously (Andruszkiewicz et al., 1987 (link), 1990 (link)). Lys-Leu-Pro-Val-Met (P5), Lys-Leu-Pro-Val-Met-FMDP (F6), Arg-Lys-Lys-Trp-Phe-Trp (P6), FMDP-Arg-Lys-Lys-Trp-Phe-Trp (F7), Lys-Lys-Val-Val-Phe-Trp-Val-Lys-Phe-Lys (P10), and FMDP-Lys-Lys-Val-Val-Phe-Trp-Val-Lys-Phe-Lys (F11) were synthesized by the solid phase method using the Fmoc/Butt strategy. The crude peptides were purified by HPLC using the Agilent 1290 Infinity system, on Kromasil C8 or Cosmosil C18 column, developed with a linear acetonitrile gradient. Purity of the peptides was determined using analytical HPLC and mass spectrometry with Agilent Technologies 6540 UHD Accurate—Mass Q-TOF LC/MS.
5
Nematicidal Compounds Analysis by LC-MS
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The three compounds with intense nematicidal activity were analyzed through liquid chromatography time-of-flight mass spectrometry (Agilent Technologies 6540UHD Accurate-Mass Q-TOF LC-MS). Next, 1 μL samples were analyzed via reverse-phase HPLC (C18 column, particle size 3.5 μm, 2.1 mm × 150 mm, Agilent Technologies) with a gradient of acetonitrile:water (20:80, v/v) at a flow rate of 0.3 mL/min. The HPLC eluate was introduced into a mass spectrometer via an ESI interface at a spray voltage of 4.0 kV. The mass spectrometer was operated in positive-ion mode with a capillary temperature of 325 °C and a capillary voltage of 130 V. Mass spectra were acquired by scanning the mass range from m/z 100 to m/z 1700.
6
Targeted LC-MS/MS Analysis of Antibiotics
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Analyses were performed on Agilent Technologies 6540 UHD Accurate-Mass Q-TOF LC/MS equipped with a reversed-phase Zorbax Eclipse C18 (Agilent, 50 × 4.6 mm, 2.7 μm particle size). Mobile phases were 95% water (A) and 5% acetonitrile (B). Antibiotics were separated following gradient program: initial conditions were 95% A, then gradient was from 100% B to 5% B in 5 min and finally, solvents were maintained to 95% A and 5% B for 4 min. The total run time was of 14 min. Column temperature was 60 °C; flow rate was 0.15 mL/min. The sample injection volume was set at 5 μL. The mass spectrometer used was a Q-TOF system equipped with a Dual ESI ion source operated in positive ionization mode. The operating parameters were ion spray voltage 5300 V, drying gas, 7 L/min, nebulizer gas 21 psig and probe temperature 300 °C. For each compound, acquisition rate 1.1 spectra/s, 909.1 ms/spectrum.
7
Synthesis of Quinoxalin-2(1H)-ones and Potassium Difluoroacetates
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The 1H NMR, 13C NMR and 19F NMR spectra were recorded on a 400 MHz or a 600 MHz Bruker FT-NMR spectrometer (400/100/376 MHz or 600/150/564 MHz, respectively). All chemical shifts are given as δ value (ppm) with reference to tetramethylsilane (TMS) as an internal standard. The peak patterns are indicated as follows: s, singlet; d, doublet; t, triplet; m, multiplet; q, quartet. The coupling constants, J, are reported in hertz (Hz). High resolution mass spectroscopy data of the product were collected on an Agilent Technologies 6540 UHD Accurate-Mass Q-TOF LC/MS (ESI). Melting points (uncorrected) were obtained on WRS-1B digital melting point apparatus. The quinoxalin-2(1H)-ones and potassium 2,2-difluoro-2-(4-methoxyphenyl)acetates were prepared according to the reported literature.8,19a (link) All the solvents and commercially available reagents were purchased from commercial suppliers. Products were purified by flash chromatography on 200–300 mesh silica gels, SiO2.
8
Melting Point and NMR Characterization
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The melting points of the products were determined on an XT-4 binocular microscope (Beijing Tech Instrument Co., China) and were not corrected. 1H and 13C NMR (solvent DMSO-d6) spectra were recorded on a Bruker AVANCE HD 600 MHz Digital NMR Spectrometer (Bruker Company, Billerica, MA, United States) at room temperature using TMS as an internal standard. High-resolution mass spectrometry (HRMS) was carried out on an Agilent Technologies 6540 UHD Accurate-Mass Q-TOF LC/MS (Agilent Technologies, Palo Alto, CA, United States). All anhydrous solvents were dried and purified according to standard techniques before use. Unless otherwise noted, all common reagents and solvents were used as obtained from commercial supplies without further purifications.
9
Synthetic Methodology for Purified Compounds
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All reagents and solvents were purchased from commercial sources. All synthesized compounds were first purified by silica flash chromatography and analyzed by IR, NMR, and HPLC/MS, assessing a purity grade (>95%). Melting points were determined by Kofler. 1H NMR and 13C NMR spectra were registered on a Bruker 300 Avance (300 MHz) spectrometer, with TMS as an internal standard. IR spectra were recorded by a Shimadzu FTIR-8300 instrument (Shimadzu Corporation, Kyoto, Japan). Chromatography for purification of the samples was realized by flash silica gel (Merck, 0.040–0.063 mm) and mixtures of petroleum ether (fraction boiling at 40–60 °C) and ethyl acetate as eluents. HRMS spectra were recorded by analyzing a 10 ppm solution of each sample in a 6540 UHD Accurate-Mass Q-TOF LC/MS (Agilent Technologies, Inc., Santa Clara, CA, USA) equipped with a Dual AJS ESI source.
10
Structural Elucidation of Purified Compounds
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The chemical structures of isolated compounds were determined by electrospray ionization mass spectrometry (ESI) and 1H and 13C NMR. Chromatographic separation was performed on an Agilent 6540 UHD Accurate-Mass Q-TOF LC/MS, and chromatographic analysis was achieved on a C18 column (particle size 5 mm, 100 × 2.1 mm, Agilent Technology) with an injection volume of 1 μL. The mobile phase was acetonitrile/SDW (2:8, v/v) at a flow rate of 0.3 mL/min. Approximately 5 mg of the purified compound was dissolved in methanol-d4 (CD3OD) and subjected to a spectral analysis. NMR spectra were recorded on a Bruker DRX 500 NMR instrument, operated at 500 MHz for 1H NMR, and 125 MHz for 13C NMR, both at room temperature. 1H and 13C NMR assignments were supported by 1H-1H correlation spectroscopy (COSY), heteronuclear multiple-quantum coherence (HMQC), nuclear Overhauser effect spectrometry (NOESY), and heteronuclear multiple-bond correlation (HMBC) experiments.
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