5975c mass selective detector

Sediment samples were dried at 40 °C for 24 h, ground, and sieved at 2 mm. The sieved samples (10–25 g), spiked with internal standards, were extracted by a Soxhlet system for 24 h by 300 mL of n-hexane for PCB analysis. The extracts were concentrated and purified by liquid chromatography on a silica gel column. PCBs were recovered by elution with 30 mL of a diethyl ether/hexane mixture (1:10, v/v). The fractions were concentrated using a rotary evaporator followed by a flow of nitrogen. Internal standards were added before quantification by instrumental analysis [58 ].
The separation, identification, and quantification of PCBs in water and sediments were performed using gas chromatography coupled with mass spectrometry (7890 gas chromatograph (GC) coupled with a 5975C mass selective detector (MSD), Agilent Technologies Inc., Palo Alto, CA, USA). The system is based on a chromatographic separation based on retention time and peak intensity, coupled with compound identification based on molecule ionization, which breaks them into fragments. The mass of the resulting fragments is specific for each molecule and can be used to identify the chemical. The MS was operated in the selected ion-monitoring (SIM) mode. The mass spectra were compared to the reference libraries of known compounds to be identified.

GC-MS analysis was performed to determine the molecular composition of AME. The filtered AME was analysed using Agilent 6890 Gas Chromatograph with a 5975C Mass-selective Detector (Agilent, Palo Alto, CA, USA). The column used was ZB-5 MSI (30 m × 0.25 mm × 0.25 μm) and the mobile phase was 5% phenyl/95% dimethylpolysiloxane. Helium was used as the carrier gas at a constant flow rate of 1 mL/min. The initial oven temperature was 40°C and it was maintained at this temperature for 1.5 min; the temperature was gradually increased to 230°C at a rate of 4°C/min and was maintained for 8 min. The temperature of the injection port was 250°C and the flow rate of helium was 1 mL/min. The compounds discharged from the column were detected by a quadrupole mass detector. The ions were generated by electron ionization method. The temperatures of the MS quadrupole and source were 150 and 230°C, respectively, electron energy was 70 eV, temperature of the detector was 230°C, the emission current multiplier voltage was 1624 V, the interface temperature was 280°C, and the mass range was from 20 to 460 u. The relative mass fraction of each chemical component was determined by peak area normalization method. The National Institute Standard and Technology Library was used to analyse the spectrum and identify the compounds detected.

Fatty acid methyl esters (FAMEs) were analyzed by GC/MS on a 7890A gas chromatograph (Agilent Technologies, Inc., Santa Clara, CA, USA) linked to a 5975 C mass selective detector (Agilent Technologies, Inc., Santa Clara, CA, USA) by using the following conditions: inlet temperature 270°C, transfer line temperature of 280°C, and column oven temperature programmed from 35 to 285°C with the initial temperature maintained for 5 min then 10°Cmin⁻¹ to 280°C, held at this temperature for 20.4 min. The GC was fitted with a HP-5 MS low bleed capillary column (30 m × 0.25 mm i.d., 0.25 μm) (J&W, Folsom, CA, USA). Helium at a flow rate of 1.25 ml min⁻¹ served as the carrier gas. The mass selective detector was maintained at ion source temperature of 230°C and a quadrapole temperature of 180°C. Electron impact (EI) mass spectra were obtained at the acceleration energy of 70 eV. A 1.0 μl aliquot of sample was injected in the splitless mode using an auto sampler 7683 (Agilent Technologies, Inc., Beijing, China). Fragment ions were analyzed over 40–550 m/z mass range in the full scan mode. The filament delay time was set at 3.3 min.