Simultaneous Determination of Pyridine and Its Derivatives in Surface Water and Wastewater by Gas Chromatography with Headspace

A method for simultaneous determination of pyridine and its derivatives including 2-methylpyridine, 3-methylpyridine, and 4-methylpyridine in surface water and wastewater, was proposed by gas chromatography with headspace. 40 mL of water sample was taken and its acidity was adjusted to about pH 10 with 0.5 mol·L⁻¹ sodium hydroxide solution and 10% (volume fraction) phosphoric acid solution. The amounts of acid and alkali were recorded. Acid or alkali was added in the sample bottle, and had an equal amount that recorded. The sample was placed in the sample bottle without leaving any space above the liquid. 10.0 mL of the above sample was taken and placed into a headspace vial that had pre-filled with 3.0 g of sodium chloride. The mixture was covered immediately and equilibrated at 80 ℃ for 30 min. The obtained gas was introduced into the gas chromatograph, separated by heating program on the HP-INNOWAX column, and determined by the nitrogen phosphorus detector, with the external standard method for quantification. As shown by the results, linear relationships between the corresponding peak heights and mass concentrations of compounds were found in definite ranges, with detection limits (3.143s) in the range of 0.88-5.3 μg·L⁻¹. Test for recovery was made by the standard addition method, giving results in the range of 95.0%-105%, with RSDs (n=6) of the determined values less than 5.0%. This method was used for the analysis of surface water and wastewater samples, and none of 4 compounds was detected in the surface water sample, while all 4 compounds were detected in the wastewater sample, with detection amounts in the range of 0.009-7.48 mg·L⁻¹ ,and the spiked recoveries were in the range of 87.5%-112%.