Hp 5ms capillary column

The chemical constituents of the Cameroonian essential oils were analyzed on an Agilent 6890 N gas chromatograph coupled to a 5973 N mass spectrometer (Santa Clara, CA, USA) and equipped with a HP-5 MS capillary column (5% phenylmethylpolysiloxane, 30 m, 0.25 mm i.d., 0.1 μm film thickness; J & W Scientific, Folsom, CA, USA). For the separation of the volatile constituents, the following temperature program was used: 5 min at 60 °C then 4 °C/min up to 220 °C, then 11 °C/min up to 280 °C held for 15 min. The injector and detector temperatures were: 280 °C; carrier gas: Helium; flow rate: 1 mL/min; split ratio: 1:50; acquisition mass range: 29–400 m/z; and mode: electron-impact (EI, 70 eV). The essential oil was diluted 1:100 in n-hexane, and then 2 µL of the solution was injected into the GC-MS system. For the identification of essential oil components, co-injection with the authentic standards available in our laboratory (purchased from Sigma-Aldrich) was performed, together with a comparison of the retention indices and the mass spectra of those occurring in the ADAMS, NIST 08, and FFNSC2 libraries [41 ,42 ,43 ]. The percentage values of the volatile components were the means of three chromatographic analyses and were determined from the peak areas without the use of correction factors.

A solution 1:100 v/v in ethyl acetate of each EO was prepared and filtered, then 1 μL of each solution was injected into the GC/MS. Analyses of EOs were carried out on an Agilent 6890 N gas chromatograph hyphenated with a 5973 N mass spectrometer provided with HP-5 MS capillary column (J & W Scientific, Folsom), using the conditions reported in our previous work [28 (link)].

For the GC-MS analysis, the Agilent 5860 gas chromatograph was used under the control of AgilentChemStation software E.02.02.1431. Sampling was performed using the autosampler Agilent 7893 in the “splitless” mode, 1 µL volume was injected. Separation was performed on a J&W HP-5MS capillary column (30 m in length, 0.25 mm in diameter, fixed phase film thickness (5% biphenyl, 95% dimethyl polyoxane) 0.1 μm). The carrier gas was helium, with a constant flow of 1.3 mL/min, and the evaporator temperature was 250 °C. Column thermostat temperature: base temperature was 70 °C increased at a speed of 4 °/min to 320 °C and then sustained for 10 min. The chromatogram was recorded by a Agilent 5975C mass-selective detector with m/z range 50–850. The source temperature was 230 °C.

A GC-MS/MS system of Agilent (model 7890B-7000C, Santa Clara, CA, USA) was operated in multiple reaction monitoring mode (MRM) with two ion transitions to obtain the maximum sensitivity for the detection of the target molecules, the mass transitions used are presented in Table 1. A HP-5MS capillary column (30 m × 250 µm × 0.25 µm) from J&W Scientific (Forson, CA, USA) was used for pesticide residue analysis, using the multi-mode inlet at 280 °C in splitless mode. The oven was programmed at 150 °C for two min, ramped at 3 °C/min⁻¹ to 200 °C, then ramped to 280 °C at 8 °C/min⁻¹ and then held for 10 min., the carrier gas was Helium (He) at a flow rate of 1 mL/min⁻¹, with a retention time (Rt) as shown in Table 1. MS was operated in electron impact ionization mode (EI). The transfer line, MS source, quad1, and quad2 temperatures were 280, 300, 180, and 180 °C, respectively. Helium (He) quenching gas and N2 collision gas were used at 2.25 and 1.5 mL/min⁻¹, respectively. The system was back flushed at 300 °C at 50 psi for five min., and the method retention time was locked to chlorpyrifos-methyl at 13.093 min. The Rt of the TTP used as IS was 24.162 min.

The major chemical molecules and ions in soil mentioned above were measured following previously described methods (Xu et al., 2015 (link)). Briefly, Fe(II) concentration was measured based on 1,10-phenanthroline spectrophotometer colorimetric method after 0.5 mol L^-1 HCl extraction for 24 h. Concentrations of anions (SO₄^2- and NO₃^-) and DOC/DON concentrations were determined through Milli-Q water extraction at ratio of 1:10 (w/v) before analysis by ion chromatography and TOC analyzer, respectively. The concentrations of PCP and its intermediate products (2,3,4,5-TeCP, 3,4,5-TCP, and 3,5-DCP) in soils were extracted by ultrasonic extraction and subsequent derivatization by mixing with K₂CO₃ (10 mL, 0.2 M) and acetic anhydride (0.5 mL) (Lin et al., 2014 (link)). A gas chromatograph (Agilent 6890N, Agilent, Santa Clara, CA, United States) equipped with a ⁶³Ni electric capture detector (Hewlett-Packard 6890, Hewlett-Packard, Palo Alto, CA, United States) and a HP-5 MS capillary column (30 m by 0.32 mm diameter by 0.25 μm) (J&W Scientific, Inc., Folsom, CA, United States) was used to determine the quantity and the species of chlorophenols. The concentration of released CO₂ and CH₄ were monitored by gas chromatography (GC) equipped with a flame ionization detector (FID) combined with a methane converter (TECHCOMP, China).