顶空气相色谱法测定水中挥发性有机物的精密度控制

摘要

It was found that the precision of the results of determination of volatile organic compounds（VOC′s） in water samples by GC using the HP 7694E head space automatic sampler was poor and unsatisfactory,and that the cause was the designing defect of its heating device.Measure for improvement was proposed by preheating the water samples to a temperature close to the temperature of the detection chamber（25±2） ℃ in water bath,and setting the conditions of head-space sampling at 55 ℃ and 15 min.Four VOC′s（i.e.CHCl3,BrCHCl2,Br2CHCl and CHBr3） were determined under the prescribed conditions.Values of RSD′s（n=5） found were in the range of 2.2% to 3.3%.%试验证明在顶空采样-气相色谱法测定水中挥发性有机物时出现的分析结果重现性差的原因在于所采用HP 7694E型顶空自动进样器加热方法的设计缺陷,对此提出了改进措施。通过用水浴预加热使整批样品温度达到与检测室温度（25±2）℃接近,并选择顶空采样条件为55℃及15min。按此条件对三氯甲烷、一溴二氯甲烷、二溴一氯甲烷及三溴甲烷等4种组分进行了测定,得到结果的相对标准偏差（n=5）在2.2%～3.3%之间。