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水体富营养化导致水体异味(off-flavor)是一个严重且普遍存在的环境问题. 异味将直接对饮用水和水产品的质量造成影响,并最终危害到饮用水和水产品的品质,造成消费者不安全感和渔业经济损失,因此水体中的异味物质研究受到越来越多的关注. 水体中最常见的两种异味物质是土臭素(geosmin)和 2-甲基异莰醇(2-methylisoborneol,2-MIB),这两种物质已经得到了较多的研究,在生活饮用水卫生标准[1]当中也规定了限量值. 但随着工业的发展和各种环境问题的爆发,仅仅关注这两种异味物质是不够的. 其他的水体异味,如土霉味、氯味、草木味、沼气味、芳香味、鱼腥味、药水味及化学品味等也需要引起我们的关注. 了解水体中异味物质的种类、分布和浓度水平是判断异味物质来源、采取针对性控制措施的基础,因此建立准确可靠并且可同时分析多种异味物质的方法十分必要.
由于异味物质的嗅觉阈值极低,例如,土臭素和2-甲基异莰醇的嗅觉阈值分别为5—10 ng·L−1和1—10 ng·L−1,因此需要高效的样品前处理和高灵敏度的检测方法. 样品富集方法目前用的比较多的有吹扫捕集法[2-3]、分散固相萃取法[4]、闭环捕集[5-6]、液液萃取[7-8]、固相萃取[9-10]、搅拌棒吸附萃取[11-12]等. 这些方法大多费时费力,需要用到有机溶剂,前处理设备如果管路多,容易存在样品残留,引起交叉污染的状况. 而20世纪80年代发展起来的固相微萃取技术由于其富集能力强,无需使用有机溶剂而深受广大科研工作者的青睐,越来越多的应用于水中异味物质的分析检测[13-17]. 2016 年,我国颁布了国家标准检测方法《GB/T 32470—2016 生活饮用水臭味物质 土臭素和 2-甲基异莰醇检验方法》[18]. 该方法采用固相微萃取技术吸附样品中的土臭素和2-甲基异莰醇,顶空富集后用气质联用仪进行分离、测定. 但是手动固相微萃取,耗时长,每天能够检测的样品数量非常少,特别不利于大批量样品的检测,并且萃取头寿命较短.
本研究中采用新的箭型固相微萃取(SPME Arrow)技术对水中的异味物质进行在线富集,涂层体积更大,加大了吸附容量,从而大大提高了富集倍数,进而提高了方法的灵敏度. 异味物质的检测技术方面,目前大多采用气相色谱-单四极杆质谱进行检测,检测的目标物种类比较少,不能满足当前水中异味物质多样化的检测需求,并且对复杂基质中的目标物检测存在基质干扰的情况. 本方法采用气相色谱-三重四极杆质谱对异味物质进行检测,提高了方法对复杂基质的抗干扰能力. 选取了57种常见的异味物质作为目标物,优化了萃取过程中对萃取效率有显著影响的关键参数,建立水体中多种异味物质的高效、稳定、全自动的SPME Arrow -气相色谱/三重四极杆质谱联用分析方法.
箭型固相微萃取技术与GCMSMS联用方法用于水中异味化合物的检测
SPME Arrow combined with GCMSMS for determination of odor compounds in water
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摘要: 箭型固相微萃取技术是近几年发展起来的一项新型样品前处理技术,灵敏度高,机械性能好,无需使用有机溶剂,利用该技术对生活饮用水中的异味物质进行富集,然后通过三重四极杆气质联用系统进行高通量筛查和定量分析. 对萃取过程中的萃取温度、萃取时间、进样口解吸的深度等影响因素进行了优化. 发现萃取头在进样口进行解吸时插入的深度对解吸速度和效率有显著的影响. 采用优化的参数建立了57种异味物质的定量测定方法. 方法验证结果显示,该方法灵敏度高,相比于传统的固相微萃取方法,检测限下降1个数量级;方法准确度高,所有化合物的线性良好,线性相关系数能达到0.99以上;方法重复性很好,实际水样加标水平10 ng·L−1,重复测定10次,所有化合物的RSD值均小于20%,90%以上的化合物RSD小于10%. 该方法各项性能均满足生活饮用水异味物质的检测要求,并且用于实际水样加标检测,无基质干扰的情况.Abstract: A novel solid-phase microextraction (SPME Arrow) system has been recently employed for sample pretreatment. It is a solvent-free microextraction technique with high sensitivity and reliable mechanical properties. In this study, the odor substances in drinking water were enriched by SPME-Arrow, followed by high-throughput screening and quantitative analysis through gas chromatography-triple quadrupole mass spectrometry (GCMSMS). Parameters influencing the extraction process, such as desorption depth of injection port, extraction time and temperature were carefully optimized. It was found that the insertion depth of SPME-Arrow at the injection port had a significant impact on the desorption speed and efficiency. A quantitative method for the determination of 57 odor substances was established based on the optimized parameters. Results showed that, compared to the conventional SPME method, this method had better sensitivity and improved the detection limit by one order of magnitude. This method also showed high accuracy and good linearity for each analyte with the values of linear correlation coefficient higher than 0.99. Ten replicate analyses of actual drinking water samples with a final internal standard concentration of 10 ng·L−1 provided reproducible results on the basis of average relative standard deviation (RSD) values. The RSD values for 90% of the analytes were lower than 10%, meanwhile those of the rest were all lower than 20%. There exhibited no matrix interference in the detection of spiked actual water samples. In general, the novel method meets the requirements for the enrichment and detection of odor substances in drinking water.
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表 1 57种化合物保留时间、名称、CAS、定量离子对
Table 1. Retention time, name, CAS, quantitative ion pair of 57 compounds
序号
No.保留时间/min
RT英文名称
Name中文名称
NameCAS 定量离子对
Quantitative ion pair1 2.94 1-Propanethiol 1-丙硫醇 107-03-9 76.0 -> 42.0 2 3.16 1-Bromopropane 1-溴丙烷 106-94-5 122.0 -> 43.0 3 4.87 n-Valeric aldehyde 正戊醛 110-62-3 44.0 -> 43.0 4 4.47 2,3-Butandione 2,3-丁二酮 431-03-8 86.0 -> 43.0 5 6.20 Dimethyl disulfide 二甲基二硫 624-92-0 94.0 -> 79.0 6 6.63 β-Pinene β-蒎烯 127-91-3 93.0 -> 93.0 7 6.79 Diethyl carbonate 碳酸二乙酯 105-58-8 91.0 -> 63.0 8 6.81 n-Amylformate 甲酸正戊酯 638-49-3 70.0 -> 42.0 9 7.20 Isoamyl methyl ketone 甲基异戊酮 110-12-3 43.0 -> 43.0 10 7.91 Cumene 异丙苯 98-82-8 105.0 -> 77.0 11 8.52 Cineole 桉叶素 470-82-6 139.0 -> 43.0 12 8.25 Pyridine 吡啶 110-86-1 79.0 -> 52.0 13 8.63 Pyrazine 吡嗪 290-37-9 80.0 -> 53.0 14 9.43 p-Cymene 对伞花烃 99-87-6 119.0 -> 119.0 15 9.62 Terpinolene 萜烯 586-62-9 136.0 -> 121.0 16 9.59 pyrimidine 嘧啶 289-95-2 80.0 -> 53.0 17 9.82 Cyclohexanone 环己酮 108-94-1 98.0 -> 55.0 18 9.90 1,3-Diethylbenzene 1,3-二乙苯 141-93-5 105.0 -> 77.0 19 10.29 2,5-Dimethylpyrazine 2,5-二甲基吡嗪 123-32-0 108.0 -> 108.0 20 10.37 4-tert-Butyltoluene 4-叔丁基甲苯 98-51-1 133.0 -> 105.0 21 10.42 1,2,3-Trimethyl benzene 1,2,3-三甲基苯 526-73-8 105.0 -> 105.0 22 10.42 tert-Amylbenzene 叔戊苯 2049-95-8 91.0 -> 91.0 23 10.51 Anisole 苯甲醚 100-66-3 108.0 -> 108.0 24 10.53 n-Butyl glycidyl ether 正丁基缩水甘油醚 2426-08-6 57.0 -> 57.0 25 11.48 Pentyl valerate 戊酸戊酯 2173-56-0 85.0 -> 57.0 26 12.61 Acetonylacetone 丙酮基丙酮 110-13-4 99.0 -> 99.0 27 13.02 2-Isobutyl-3-methoxypyrazine 2-异丁基-3-甲氧基吡嗪 24683-00-9 124.0 -> 94.0 28 13.04 N,N-Dimethylacrylamide N,N-二甲基丙烯酰胺 2680-03-7 98.0 -> 42.0 29 13.23 Linalool 芳樟醇 78-70-6 93.0 -> 93.0 30 13.83 Isoborneol acetate 乙酸异冰片 125-12-2 136.0 -> 121.0 31 13.93 2-Methylisoborneol 2-甲基异莰醇 2371-42-8 108.0 -> 93.0 32 14.44 L-Menthol L-薄荷醇 2216-51-5 81.0 -> 81.0 33 14.44 Dicyclohexylamine 二环己基胺 101-83-7 138.0 -> 55.0 34 14.45 trans-2-Decenal 反-2-癸烯醛 3913-81-3 55.0 -> 55.0 35 15.64 4-Ethylbenzaldehyde 4-乙基苯甲醛 4748-78-1 134.0 -> 105.0 36 15.67 Naphthalene 萘 91-20-3 128.0 -> 128.0 37 16.31 Perillaldehyde 紫苏醛 18031-40-8 122.0 -> 79.0 38 16.44 Ethyl salicylate 水杨酸乙酯 118-61-6 120.0 -> 92.0 39 16.65 Anethole 茴香脑 104-46-1 148.0 -> 105.0 40 16.69 Geosmin 土臭素 16423-19-1 112.0 -> 97.0 41 16.79 2-Chlorophenol 2-氯酚 95-57-8 128.0 -> 64.0 42 16.87 α-Ionone 2-紫罗兰酮 127-41-3 121.0 -> 77.0 43 16.91 2-Methylnaphthalene 2-甲基萘 91-57-6 142.0 -> 142.0 44 16.93 Guaiacol 愈创木酚 90-05-1 109.0 -> 81.0 45 17.42 2,6-Dimethylphenol 2,6-二甲基苯酚 576-26-1 107.0 -> 77.0 46 17.53 p-Ethylaniline 对乙基苯胺 589-16-2 106.0 -> 106.0 47 19.19 Methyl cinnamate 肉桂酸甲酯 103-26-4 131.0 -> 103.0 48 19.51 2,6-Dichlorophenol 2,6-二氯苯酚 87-65-0 164.0 -> 63.0 49 20.07 2,4-Dichlorophenol 2,4-二氯苯酚 120-83-2 162.0 -> 162.0 50 21.12 Dihydrojasmonic acid methyl ester 二氢茉莉酸甲酯 24851-98-7 153.0 -> 97.0 51 21.81 2,4,6-Trichlorophenol 2,4,6-三氯酚 88-06-2 196.0 -> 97.0 52 22.41 4-Chlorophenol 4-氯酚 106-48-9 128.0 -> 65.0 53 22.97 4-Chloro-m-cresol 4-氯-3-甲酚 59-50-7 142.0 -> 107.0 54 23.16 Ethyl vanillin 乙基香兰素 121-32-4 166.0 -> 137.0 55 23.53 Vanillin 香兰素 121-33-5 152.0 -> 151.0 56 23.83 p-Bromophenol 对溴苯酚 106-41-2 172.0 -> 65.0 57 24.09 Benzyl benzoate 苯甲酸苄酯 120-51-4 212.0 -> 105.0 表 2 57种化合物线性范围、相关系数、重复性、检出限
Table 2. Linear range, correlation coefficient, repeatability, MDL of 57 compounds
序号
No.保留时间/min
RT中文名称
Name线性范围/
(ng·L−1)线性相关系数
R2相对标准偏差
RSD方法检出限/(ng·L−1)
MDL1 2.94 1-丙硫醇 10—500 0.9936 7.21 1.20 2 3.16 1-溴丙烷 10—500 0.9956 7.26 1.24 3 4.87 正戊醛 10—500 0.9991 3.15 2.90 4 4.47 2,3-丁二酮 10—500 0.9973 8.72 2.96 5 6.20 二甲基二硫 1—500 0.9888 1.18 0.49 6 6.63 β-蒎烯 1—500 0.9993 2.72 0.35 7 6.79 碳酸二乙酯 10—500 0.9958 8.12 1.02 8 6.81 甲酸正戊酯 10—500 0.9973 6.99 1.43 9 7.20 甲基异戊酮 10—500 0.9975 5.56 0.81 10 7.91 异丙苯 10—500 0.9997 6.02 0.46 11 8.52 桉叶素 10—500 0.9999 7.00 1.47 12 8.25 吡啶 10—500 0.9933 7.25 5.75 13 8.63 吡嗪 10—500 0.9920 6.79 2.90 14 9.43 对伞花烃 10—500 0.9903 2.13 0.73 15 9.62 萜烯 10—500 0.9006 3.10 1.02 16 9.59 嘧啶 50—500 0.9986 17.35 18.03 17 9.82 环己酮 10—500 0.9902 9.50 3.34 18 9.90 1,3-二乙苯 10—500 0.9993 8.19 1.07 19 10.29 2,5-二甲基吡嗪 10—500 0.9993 7.15 1.10 20 10.37 4-叔丁基甲苯 10—500 0.9994 6.05 1.96 21 10.42 1,2,3-三甲基苯 10—500 0.9989 6.63 1.30 22 10.42 叔戊苯 10—500 0.9990 3.61 1.48 23 10.51 苯甲醚 10—500 0.9978 6.75 0.77 24 10.53 正丁基缩水甘油醚 10—500 0.9960 8.28 1.29 25 11.48 戊酸戊酯 10—500 0.9967 2.15 0.82 26 12.61 丙酮基丙酮 10—500 0.9930 1.21 1.69 27 13.02 2-异丁基-3-甲氧基吡嗪 10—500 0.9975 4.42 1.18 28 13.04 N,N-二甲基丙烯酰胺 200—1000 0.9998 — 204.80 29 13.23 芳樟醇 1—500 1.0000 4.78 0.92 30 13.83 乙酸异冰片 1—500 0.9983 7.65 0.65 31 13.93 2-甲基异莰醇 1—500 1.0000 2.92 0.89 32 14.44 L-薄荷醇 10—500 0.9980 8.71 3.22 33 14.44 二环己基胺 10—500 0.9986 9.37 3.26 34 14.45 反-2-癸烯醛 10—500 0.9989 8.66 1.57 35 15.64 4-乙基苯甲醛 10—500 0.9989 5.74 2.02 36 15.67 萘 10—500 0.9998 9.85 2.98 37 16.31 紫苏醛 1—500 0.9998 4.60 0.65 38 16.44 水杨酸乙酯 1—500 0.9955 1.45 0.93 39 16.65 茴香脑 1—500 0.9991 2.91 0.91 40 16.69 土臭素 1—500 1.0000 1.09 0.22 41 16.79 2-氯酚 1—500 0.9984 5.14 0.77 42 16.87 2-紫罗兰酮 1—500 0.9958 1.97 0.81 43 16.91 2-甲基萘 10—500 0.9990 9.18 2.46 44 16.93 愈创木酚 10—500 0.9996 5.99 1.41 45 17.42 2,6-二甲基苯酚 10—500 0.9998 7.38 1.88 46 17.53 对乙基苯胺 10—500 0.9951 3.13 9.54 47 19.19 肉桂酸甲酯 10—500 0.9971 3.16 1.41 48 19.51 2,6-二氯苯酚 10—500 0.9864 13.83 3.44 49 20.07 2,4-二氯苯酚 10—500 0.9991 4.24 1.43 50 21.12 二氢茉莉酸甲酯 10—500 0.9952 7.96 3.53 51 21.81 2,4,6-三氯酚 10—500 0.9864 12.40 2.87 52 22.41 4-氯酚 10—500 0.9990 6.77 2.40 53 22.97 4-氯-3-甲酚 10—500 0.9992 3.15 1.09 54 23.16 乙基香兰素 100—500 0.9983 — 76.41 55 23.53 香兰素 50—500 0.9972 7.67 15.70 56 23.83 对溴苯酚 10—500 0.9992 5.86 1.85 57 24.09 苯甲酸苄酯 1—500 0.9988 1.77 0.48 -
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