茶叶及茶汤中有机磷农残检测的研究

【作者】 蔡向阳；

【导师】 吴祖建；

【作者基本信息】 福建农林大学 ， 植物保护， 2008， 硕士

【摘要】 大部分有机氯杀虫剂的禁用,使得具有易降解、残留期短等特点有机磷杀虫剂在茶叶种植业中得到了广泛的应用。另一方面,残留在茶叶中的有机磷农药会毒害人类健康,农残问题日益受到关注。因此,对茶叶中的有机磷类农药的残留进行分析具有十分重要的实际意义。本论文的研究工作主要分为四部分:第一部分对目前农药残留的现状及分析研究的进展进行了综述,指出了对茶叶中的农药残留检测进行前处理的必要性,提出本论文所要开展的研究工作的设想。第二部分探讨了自制的固相萃取柱在有机磷农药残留分析中进行浓缩净化的可行性,并通过色谱方法对其进行验证。其预处理条件如下:茶叶样品以丙酮为提取剂,采用采用PSA—活性炭混合固相萃取柱净化方法,用乙酸乙酯淋洗,经色谱分析,结果令人满意。第三部分建立了马拉硫磷等15种有机磷农药的GC—FPD分离检测分析方法。在最优化实验条件下,15种有机磷农药在25 min内实现基线分离。在对第二部分样品前处理的基础上,将该法应用于茶叶中有机磷农药残留的分析,添加回收率在61.1±7.0%～112.5±5.5%之间,RSD≤7.0%,最小检出浓度在0.0025～0.040 mg/L之间。第四部分建立了漏斗辅助单滴液相微萃取和气相色谱结合的方法,用于茶叶样品中有机磷农药的测定。选用茶汤作为茶叶样品的分析对象来测定样品中两种有机磷类农药残留,具有现实可靠性。微萃取过程中漏斗内角度、萃取溶剂种类、微液滴体积、搅拌速率、萃取温度、萃取时间、盐析作用对分析对象的富集有重要的影响。实验表明,最佳萃取条件为漏斗内角90°、二氯甲烷:甲苯(1:3,V/V)为萃取溶剂、样品溶液搅拌速率900rpm、萃取温度40℃、微液滴体积4uL、萃取时间15min。本方法的检出限为63～110ug/kg,远低于欧盟制定的茶叶中农药最大残留限量标准,在茶叶的进出口检验上具有应用价值。本论文主要是通过对茶叶中有机磷农药残留的前处理条件进行了摸索,并且结合GC方法对前处理条件进行验证。实验表明自制的PSA-活性炭混合固相萃取小柱能对茶叶中的有机磷农药残留进行有效的浓缩净化,该方法能够减少复杂样品基质的背景干扰,达到节省溶剂、低成本和高回收率的样品提取净化效果。论文的第四部分是讨论液相微萃取技术应用于茶汤中有机磷农药残留的检测,该方法具有省时、省力、减少有机溶剂的特点。更多还原

【Abstract】 Due to the banning of bulk organochlorine pesticides, organophosphorus pesticides (OPs) have widely used for its relatively low persistence in tea plant. At the same time, organophosphorus pesticides’s residues in tea threated human health and cause environmental pollution. At present the problems has become more and more obvious. The analysis of OPs residue in the tea is of great significance.This paper is consisted of four parts.The progress of the determination methods for pesticides were described in the first part. The techniques preparation and determination were summaried and the method about the chromatography with solid phase extraction was studied in this part.In the second part, the technique of solid-phase extraction was researched. The preparation method of tea was studied as follows:using actone as extract solvent with ultrasonic, OPs can be enriched by solid phase extraction with PSA and active carbon, the analytes were eluted by ethyl-acetate. Good recoveries and RSD were obtained.In the third part, a GC-FPD method was developed and applied for determination of fifteen OPs. Under the optimized conditions, fifteen analytes were separated baseline within 25 minutes. On the base of the pioneering work in the second part, the method has been exploited to detect the fifteen OPs in the tea samples. The average recovery was in the range of 61.1%～112.5%, and RSD was no more than 7.0%.The maximum residue limits (MRLS) were between 0.0025 mg/L and 0.040 mg/L.In the forth part, A funnelform single-drop microextraction was developed for GC-FPD detection. Tea were analyzed by the proposed method. Tea soup was used as the analytical during the determination of the pesticide residues in tea samples. A solvent microdrop of 4uL was formed at the tip of a microsyringe needle assembled with a small brass funnel in the microextraction with a stirring speed of 900rpm. Two organophosphorus pesticides were used as the model compounds for evaluating the microextraction. The parameters the enrichment factor of the microextraction were investigated. Under the selected conditions, including the funnel inner angle of 90°, the mixed solvent of 1:3 (V/V) dichloromethane and phenylmethane as extracting solvent , the extracting temperature of 40℃, the enrichment factors of organophosphorus and were higher than that obtained by the conventional single-drop method. The detection limit was in the range from 63 to 110ug/kg(S/N=3).In this paper, the study of preparation about OPs in tea was described and GC was used to separate and determinate the OPs. It is proved that the PSA-CARB can be used to concentrate and clean up the OPs in tea. The interference by complicated matrixes can be declined. The good recovery, fewer solvent and lower cost can be obtained. In the last part of paper, LPME-GC-FPD was used to separate and detect two Ops in tea soup. This proposed technique is simple, convenient and effieient.更多还原