Preparation Of A Mixed Reference Material With 29 Kinds Of VOCs And Its Application As Quality Control For Environmental Water Analysis

VOCs, short for volatile organic compounds, is one of indexes to evaluate water quality and lots of environmental standards limit its exist in water. However in the water, the trace and great variety of VOCs bring difficulties to ensure measuring accuracy and reliability in quality control during environmental water analysis. The reference material (RM) is used as a mean of environmental monitoring quality control. Recently, developing of environmental protection issue and analysis methods make more demands of VOCs RM for water analysis. Commercially available VOCs RMs are imports, and the compounds included and concentration can not fit the demand of actual monitor in our country. Therefore, this paper studies a mixed RM VOCs which covers 29 kinds of VOCs in our country's water environmental standards, solves the technical difficulties during the process of development, and tests the homogeneity and study of RM. The main studies as followed:1. Vinyl chloride was gas state at room temperature, while other 28 kinds of VOCs were liquid. So we pre-prepared vinyl chloride solution in methanol by gastight syringer, then standardly weighted the rest of VOCs and mixed all compounds in methanol, finally according to direction for the reference materials, poured the solution into ampouls by racking machine and labeled. Test homogeneity of the developed RM, Statistic results for homogeneity indicated the batch RM was qualified during production.2. We tested stability of the VOCs RM. Results for long-term stablities demonstrated the RM were stable in 18 months at -18? preservation condition; because epoxy chloropropane was active, the RM was not stable at room temperature and 4?. We made further study about the short-term stability. The results showed the concentration of epoxy chloropropane was large effected by environmental temperature. Therefore, we regulated the transport condition about the RM:during transporting the RM, it was necessary to control low temperature; after arriving the labs, the RM could be store at 4? or temperature in the short time, and it would be the best that accomplished the measurements as soon as fast to ensure RM accuracy.3. We optimized purge and trap gas chromatography mass in monitoring the VOCs in water, the best parameters as followed:11 min purge time at the speed of 40 mL/min,1 min dry purge time,180? pre-desorption temperature,30? purge temperature for 11 min,190? desorb temperature for 2 min, baked 8 min at 230?.The developed VOCs RM was tested by 7 labs for the interlaboratory comparison by this optimized conditions, and the test data were analysed by statistic methods-Dixon, Grubbs, and Cochran in turn. Reject the abnormal and calculate the standard value of the RM, Consolidate uncertainty from preparation, homogeneity test, stability study and characterization, and evaluate the expand uncertainty of RM.4. Detecting the VOCs in environmental water by using the developed RM as quality control under the optimized methods, the results for linear is well correlation, and the recoveries of all water samples ranged over 60%?130%, and the limit of determination ranged over 0.04-2.82 ?g·L-1, and the RSD of precision ranged over 0.7%?7.5%.The developed RM with 29 kinds of VOCs as quality control can be used to water analysis, fufill the system of mixed VOCs RMs in our country, control the quality in environmental water analysis.