2.3 Sample analysis
After the reaction was quenched, a 1 mL sample was collected in a 10 mL
centrifuge tube. The internal standard method was used to quantify the
composition of the products. A known quantity of nitrobenzene was added
to the centrifuge tube as the internal standard, and then methanol was
added to dilute the mixture. After the sample was evenly mixed, a small
amount of the sample was extracted and analyzed by ultra-performance
liquid chromatography (UPLC) using an ACQUITY UPLC I-Class system
(Waters, USA) equipped with an ACQUITY UPLC BEH C18 column (2.1 × 100
mm, 1.7 μm). The injection volume was 1 μL. The mobile phase consisted
of methanol (50%) and water (50%), and its flow rate was 0.2 mL/min.
The column temperature was 30 °C. The detection wavelength of the UV
detector was 200-300 nm. For the peaks observed for each substance by
UPLC, please refer to the Supporting Information (Figure S1 ).
In the internal standard method, standard curves were obtained by
varying the proportions of each substance and the internal standard can
be found in the Supporting Information (Figure S2 ). The
correction factor for each substance was calculated with Equation (1),
and the mass of the various substances in the sample was calculated with
Equation (2). The goodness of fit (R2) for each
standard reached 0.999.
The subscript i represents CB, o -NCB, p -NCB, m -NCB
or DNCB. The subscript s represents nitrobenzene, f is the
correction factor obtained from the standard curve, A is the
liquid chromatographic peak area, and m is the mass of the
substance in the sample.
The CB conversion can be calculated with the following equations:
where c is the molar concentration of the substance in the
sample, M is the molar mass of the substance, andX CB is the CB conversion.
The selectivity of each product can be calculated with the following
equations:
where S NCB is the selectivity of
mononitrochlorobenzene and S DNCB is the
selectivity of DNCB.
The residence time in the capillary is calculated with the following
equation:
where V is the volume of the capillary andQ or and Q ac are the
volumetric flow rates of the two solutions, respectively.