Chlorination Experiments on Organic Compounds

Chlorination experiments were conducted in 10 mM phosphate buffer
(pH 7) in amber glass bottles at room temperature (23 ± 2 °C)
for 5–48 h. The commercial solution of sodium hypochlorite
was standardized by measuring the absorbance of the hypochlorite anion
at 292 nm (ε = 362 M^–1 cm^–1).^{23 (link)} The chlorination of cysteine, glutathione,
and p-phenolsulfonic acid was conducted individually
by applying 250 μM each compound and 0.5–2.5 mM initial
chlorine. The chlorination of the SRFA extract (5 mg/L dissolved organic
carbon, DOC) was performed by applying 5 mg/L as Cl₂ of
initial chlorine. The residual chlorine was measured using the DPD
colorimetric method²⁴ and quenched using
a 2-fold molar excess of Na₂S₂O₃.
The chlorinated solutions of cysteine and glutathione were directly
analyzed on SFC-QTOF without further enrichment, while the chlorinated p-phenolsulfonic acid and SRFA were analyzed after freeze-drying
enrichment.