ABSTRACT
Gas chromatography with mass spectrum detector ( GC-MSD) coupled with purge-and-trap system was set up to analyze the concentration of isoprene in natural waters. The best experimental conditions were established, including purge gas flow rate ( 50 mL/min ) , purge time ( 15 min ) , the optimum capillary column ( Rt-Alumina BOND/KCl) and the appropriate condition of temperature programming. When analyzing isoprene in natural waters, the precision was <4% (n=6), the detection limit was 0. 5 pmol/L and the recovery was 91%-102%. The preservative experiment showed that there was no obvious variation in sample concentrations of isoprene within 60 days. The concentrations of isoprene measured with the method ranged from 60 . 8 to 278 . 7 pmol/L in the Jiaozhou Bay and its adjacent river estuaries and from 44 . 7 to 77 . 2 pmol/L in Yellow River estuary, which was in good accord with those results reported in literatures in other coastal waters. In conclusion, the analytical method could meet the requirements of the analysis of concentration of isoprene in natural waters.
ABSTRACT
Oceanic carbon monoxide(CO) has been of biogeochemical interest due to its significant role in global carbon cycle and the greenhouse effect. A headspace method coupled with ta3000 trace gas analyzer system for the determination of CO in seawater was developed. The effects of temperature, equilibrium time and water/gas volume ratio on the sensitivity of headspace analysis were studied in detail. The results showed that CO concentrations in seawater were measured successfully by the 50-mL glass-only syringes with a water/gas volume ratio of 44∶ 6 and an equilibrium time of 5 min at 20 ℃ room temperature. Under the optimized conditions, the linear range of concentrations of CO was 0-2.7×10~(-6), r=0.999,p<0.0001. The relative standard deviation of the analysis method was <4.4%, with a detection limit of 0.02 nmol/L. The average recovery of CO was 90.5%. The concentrations of CO in surface waters of the North Yellow Sea were measured using this method and ranged from 0.20 nmol/L to 3.13 nmol/L, indicating that this method can be successfully applied to the detection of the in situ CO concentrations in seawater.