挥发性有机污染物标准物质使用的短期稳定性评价

摘要

为对挥发性有机物标准物质的短期稳定性进行评价,选取美国ChemService公司生产的LVOC-1RPM(甲醇中54种挥发性有机污染物混合标准物质)和SS-524RPM(甲醇中4-溴氟苯和1,2-二氯苯-d4混合标准物质),将其开封后转移至2mL带聚四氟乙烯衬盖的棕色螺口样品瓶中再密封,于-18℃避光贮存,采用气相色谱-质谱法测试各组分量值随贮存时间的变化.结果表明,在65d内,两种标准物质各组分量值测量的标准偏差在12～60mg/L范围内,最大相对标准偏差为2.97％(n=5),测量结果的相对不确定度小于5.39％.在置信度为95％时,X2-检验和不确定度评定结果表明,评价方法满足标准物质稳定性检验的精密度和准确度要求；标准物质各组分量值在(2000±128)mg/L范围内时,测量的偏差不显著.在不超过标准物质的有效期内,开封后再密封的LVOC-IRPM标准物质至多可保存65d,而SS-524RPM标准物质至少可保存65d.%In order to evaluate short-term stability of opened stocks of certified reference materials (CRMs) in the analysis of volatile organic compounds (VOCs), CRMs LVOC-1RPM and SS-524RPM (including 54 VOCs and 2 surrogates in methanol, respectively, manufactured by ChemService Inc. , USA) the stocks were transferred into 2 mL brown bottles equipped with Teflon-lined screw-caps, stored at - 18℃ and protected from light. The variation of the CRMs' compounds with storage time was tested by Gas Chromatography-Mass Spectrometry (GC-MS). The results showed that the standard deviations of all the compounds of the 2 CRMs ranged from 12-60 mg/L, the maximum relative standard deviation is 2.97 % (n = 5 ) and the maximum relative uncertainty is below 5.39%. In the 95% confidence interval, the chi-squared test (X2 -test) and uncertainty estimation show that precision and accuracy of the measurements is acceptable. In addition, the measurement deviation is not significant when the range of compounds of the CRMs are within (2000 ± 128) mg/L. The experimental data also shows that the preservation period of the opened stocks of LVOC-1RPM CRMs is not more than 65 days and that of the opened stocks of SS-524RPM CRMs is not less than 65 days within the period of validity of the CRMs.