Orange County Water District（OCWD）实验室已开发出一种成本效益高的 以及非常灵敏的NDMA和1,4-二恶烷检测方法 GC/MS/MS/CI和GC/MS/MS/吹扫捕集器。由于 这些方法每年处理2000多个样本的成本非常高。实验室 启动了多残留分析方法，将1,4-二恶烷与 亚硝胺的现有分析方法。固相萃取（SPE） 对于80至100目颗粒碳，使用10毫升二氯甲烷 从吸收性材料中提取感兴趣的分析物。10毫升提取物 浓缩至1ml的最终体积，用GC/MS/MS进行分析 甲醇试剂溶液正化学电离。 所开发的分析方法产生了可接受的回收率和精密度 适用于亚硝胺和1,4-二恶烷，适用于不同基质的水样 如地下水、地表水和再生水。可报告的 吹扫捕集器关闭时，1,4-二恶烷的检测限为0.05 ppm 方法为十亿分之一。 最近，美国环境保护署（US Environmental Protection Agency）将1,4-二氧六环（1,4-dioxane）归类为可能的人类 在特定的地下水和地表水中检测到致癌物质。这个 水系统中1,4-二恶烷的发现促使需要进行广泛的研究 监测饮用水中的化合物。但目前 方法的检测限高达10至50 ug/L。高可报告性 检测限是萃取效率低和挥发性物质的结果 化合物。奥兰治县水区（OCWD）实验室进行了检测 提取和分析技术，以建立更灵敏和可靠的方法 分析饮用水样中小于1 ug/L的1,4-二恶烷。 OCWD实验室已经开发出一种非常可靠的方法来测定亚硝酸盐 使用气相色谱/质谱法测定每万亿次N-亚硝二甲胺（NDMA）含量 与甲醇或乙腈正化学电离。 因为1,4-二恶烷和 亚硝胺具有相似的性质，非常水溶性、挥发性和极性，1,4- 二氧六环已成功纳入亚硝胺的现有方法中。到 将1,4-二氧六环纳入现有分析方法，1,4-二氧六环-d8和 NDPA-d14均用作内标。测定500ml样品的pH值 在4到11之间调节，并用60毫升亚甲基萃取三次 氯化物。在35摄氏度下使用氮气将提取物蒸发至1毫升 水浴中的温度。测定了1,4-二氧六环和NDMA的保留时间 在60m毛细管柱上分别为11.43和11.86分钟。 保留期 0.43分钟的时间差足以改变化学电离 从1,4-二氧六环到NDMA的设置，需要进行多种设置 同时测定这些化合物，而不减少 仪器灵敏度。改进的提取和仪器技术 生成的方法检测限，作为1L样本量的基础，范围为 1,4-二氧六环为0.1至0.2微克/升，NDMA为0.2至0.3微克/升。 对于正化学电离，甲醇或乙腈有几种 在安全性和系统维护方面优于氨气。还有 采用分液漏斗改进液-液萃取技术可以节约成本 液-液连续萃取时间与80%液萃取时间相比 技巧1,4-二氧六环和NDMA分析的最新工作结果 包括地下水、地表水和再生水样本。这 这项研究清楚地证明了使用甲醇化学电离的GC/MS 对1,4的同时分析非常敏感、可靠且具有成本效益- 水样本中的二恶烷和NDMA。包括12个参考文献，表1。

Orange County Water District (OCWD) Laboratory has developed a cost-effective and very sensitive detection method for NDMA and 1,4-dioxane using GC/MS/MS/CI and GC/MS/MS/Purge-Trap, respectively. Since the demand of these methods is very high to process over 2,000 samples each year. The lab initiated the multi-residual analytical method to incorporate 1,4-dioxane with the existing analytical method for nitrosamines. The solid phase extraction (SPE) with 80 to 100 meshes of granular carbon uses 10 ml of methylene chloride for extracting the interested analytes from the absorbent materials. The 10 ml extract was concentrated to final volume of 1ml to be analyzed by GC/MS/MS with positive chemical ionization with methanol reagent solution. The developed analytical method generated the acceptable recovery and precision for both nitrosamines and 1,4-dioxane for different matrix of aqueous samples such as groundwater, surface water and reclaimed water. The reportable detection limit of 1,4-dioxane was 0.05 parts per billion while the purge-trap method was 1.0 part per billion. Recently, 1,4-dioxane, which the US Environmental Protection Agency classifies as a B2 probable human carcinogen, has been detected in the specific ground and surface waters. The findings of 1,4-dioxane in the water systems prompted the need of extensive monitoring of the compound in the drinking water. But the currently available methods have high detection limits of 10 to 50 ug/L. The high reportable detection limits are the results of poor extraction efficiency and volatile nature of the compound. Orange County Water District (OCWD) Laboratory has examined extraction and analysis techniques to establish a more sensitive and reliable method to analyze for 1,4-dioxane to less than 1 ug/L in drinking water samples. OCWD Laboratory has been developed a very reliable method to determine sub part per trillion levels of N-nitrosodimethylamine (NDMA) by GC/MS using positive chemical ionization with methanol or acetonitrile. Since 1,4-dioxane and nitrosamines have similar properties, very water soluble, volatile and polar, 1,4- dioxane was successfully included in the existing method for nitrosamines. To accommodate 1,4-dioxane into the existing analytical method, 1,4-dioxane-d8 and NDPA-d14 were both used as internal standards. The pH of 500 mL sample was adjusted between 4 and 11 and extracted three times with 60 ml of methylene chloride. The extract was evaporated to 1 ml using nitrogen gas at 35 celsius degrees in a water bath. The retention times of 1,4-dioxane and NDMA were 11.43 and 11.86 minutes with 60 m capillary column, respectively. The retention time differences of 0.43 minutes was far enough to change chemical ionization settings from 1,4-dioxane to NDMA, which multiple settings are necessary to perform simultaneous determination of these compounds without decreasing instrument sensitivity. The modified extraction and instrument techniques generated method detection limits, as the basis of a 1 L sample size, range from 0.1 to 0.2 ug/L for 1,4-dioxane and 0.2 to 0.3 ng/L for NDMA. For the positive chemical ionization, methanol or acetonitrile have several advantages over ammonia gas for safety and system maintenance. Also, the modified liquid-liquid extraction technique using separatory funnel could save 80% of extraction time compared to the continuous liquid-liquid extraction technique. The results of recent work on the analysis of 1,4-dioxane and NDMA from groundwater, surface water and reclaimed water samples are included. This study clearly demonstrated the GC/MS using chemical ionization with methanol was very sensitive, reliable and cost effective for the simultaneous analysis of 1,4- dioxane and NDMA from aqueous samples. Includes 12 references, table.