顶空气相色谱/质谱法测定水中四乙基铅的关键因素研究

采用顶空气相色谱/质谱法联用技术测定水中的四乙基铅,对涉及的关键操作环节及重点技术问题进行了研究。结果表明,在避光条件下于4℃低温冷藏并密封保存,添加甲醇作为保护剂,保存时间不应超过3 d。实验选择进样口温度为220℃,顶空瓶压力为96.52 kPa,调节载气流量设置实际分流比为51,可以有效改善顶空进样测定样品时存在的不出峰、不稳定或灵敏度降低的问题。对地表水、自来水及生活污水实际样品进行四乙基铅测定和加标回收分析,加标回收率为81.0%~110%,相对标准偏差(RSD)为2.5%~7.4%,能够满足《水质四乙基铅的测定顶空/气相色谱质谱法》(HJ 959—2018)的测定要求。将顶空进样法与吹扫捕集法进行比较,结果表明顶空进样法稳定性更好,适合大批量四乙基铅样品的连续测定。     

土壤中挥发性芳香烃的顶空前处理方法研究

本方法针对土壤中挥发性芳香烃顶空前处理条件进行了研究,优化了顶空密封垫的选择、顶空平衡温度、加热平衡时间、进样时间和顶空瓶压力等顶空前处理条件,测定条件科学、准确,完全能够满足土壤中挥发性芳香烃监测分析的灵敏度和准确度相关的技术要求。该方法精密度为1.7%~9.8%,准确度为34.3%~83.7%,检出限为2.0~4.2μg/kg。为制订土壤中挥发性芳香烃监测分析方法提供了技术支持。     

自动顶空毛细柱气相色谱法测定废水中甲醇

采用自动顶空气相色谱法,以顶空瓶80℃,30 min平衡时间,4 g氯化钠的条件下,用气相色谱法测定其含量。结果表明,ρ(甲醇)在1.0~12 mg/L范围内线性良好,加标回收率为102%~105%,检出限为0.11 mg/L,RSD为3.6%。此法可在30 min之内完成废水中甲醇的测定,缩短样品的前处理时间。     

顶空-气相色谱法测定地表水中松节油

采用顶空-气相色谱法测定地表水中松节油,并对顶空瓶的平衡温度、平衡时间,盐析效应和取样量等顶空条件进行优化,使方法在0.200 mg/L~4.00 mg/L范围内线性良好,方法检出限为0.037 mg/L。实际样品2个质量浓度水平的加标回收率为89.3%~108%,RSD分别为5.8%和4.8%。     

顶空气相色谱法测定高湿度废气中丙酮

建立了高湿度废气中丙酮的测定方法,直接用顶空瓶采集高湿度废气,然后向顶空瓶中加入超纯水,使顶空瓶中的水量恒定,最后用顶空气相色谱法测定顶空瓶中气体浓度,并研究了水份对丙酮测定的影响。方法具有良好的线性和平行性,相关系数在0.999以上,样品测定的相对标准偏差在5%左右。     

手工静态顶空法测定水中挥发性卤代烃的操作关键

测定水中挥发性卤代烃,国家标准推荐使用的方法是手工静态顶空法,但在实际操作时,精密度和准确度不易得到保证,操作关键除了《水和废水监测分析方法》（第四版）提到的平衡温度、平衡时间和顶空瓶的密闭性外,取样注射器表面对样品有吸附,对测定结果有影响。将注射器进行脱活处理后,即能解决玻璃表面的吸附问题。     

正交法优化顶空—毛细管气相色谱法测定水中甲醇的实验条件

用顶空进样-毛细管气相色谱法测定水中甲醇，实验结果受到顶空条件影响因素较多。本文使用正交试验方法对顶空进样的加盐量、炉温、恒温时间等5个因素进行了优化，确定了顶空进样气相色谱法测定水中甲醇的最佳操作条件，配合DB-624石英毛细管柱和氢火焰离子化检测器，检出限可达到0．33mg/L。用本方法选择实验条件更加科学合理，测定结果更加可靠。     

顶空-气相色谱法测定地表水中6种乙酸酯类化合物

采用顶空-气相色谱法测定地表水中乙酸酯类化合物,并对顶空瓶的加热温度、平衡时间进行优化。优化后,方法在6种乙酸酯类化合物质量浓度0.05~1.00 mg/L范围内线性良好,检出限为4.49~58.5μg/L,RSD为0.61%~2.51%,加标回收率为96.5%~104%,方法便捷、环保、经济,适用于地表水中乙酸酯类的检测。     

顶空气相色谱法测定土壤中有机溶剂残留量

以HP-INNOWAX色谱柱(30 m×0.32 mm×0.25μm)为分离柱,火焰离子化检验,外标法定量,考察顶空平衡温度、平衡时间对土壤中有机溶剂残留量测定结果的影响。建立了土壤中正己烷、乙酸乙酯、丙酮、甲醇等有机溶剂残留量的顶空气相色谱分析方法。实验结果表明,在顶空平衡温度为90℃,平衡时间为30 min条件下获得较好的定量结果。正己烷的线性方程为Y=11.49X-4.806、乙酸乙酯为Y=4.997X-2.873、丙酮为Y=9.710X-1.556、甲醇为Y=9.316X-5.956;平均回收率范围为78%~97%,精密度(以相对标准偏差计,n=6)为2.8%~9.4%,检出限分别为0.9、0.2、0.6 mg/L和0.4 mg/L。利用该方法对实际样品土壤中有机溶剂残留量进行了检测。结果表明,该样品中含有正己烷和甲醇,其含量分别为1.9 mg/L和1.1 mg/L。本方法快速、灵敏、准确,适用于土壤中残留溶剂的检测。     

水和废水中甲醇的测定方法探讨

甲醇作为溶剂在化工工业和实验室中广泛使用,但我国现阶段尚未明确规定甲醇的监测分析方法。本方法采用顶空/气相色谱法测定水和废水中甲醇的浓度,方法最低检出浓度为0.030 mg/L,无溶剂污染,不受乙醇、异丙醇等物质的干扰,结果准确,操作快捷方便,在日常监测任务中有很好的适用性。     

Evaluation of septum-capped vials for storage of gas samples during air transport

In order to provide information on the suitability of commonly used gas storage vials for air transport, we tested two vial types on their ability to preserve defined nitrous oxide concentrations and excess pressure when exposed to low pressure, low temperature and puncture by needles. Unlike in Crimp Cap vials, in Exetainers no nitrous oxide loss following low pressure storage was detectable. Tightness of Exetainers following multiple puncture was best using a small needle diameter. Pressure loss following 5, 10, or 25 punctures was lowest in the Exetainers. We conclude that Exetainers are suitable for storing gas samples for an extended period of time during aircraft transport.     

Predictive model for chloroform during disinfection of water for consumption,city of Montevideo

The objective of this study was to predict chloroform formation resulting from the process of disinfecting water, particularly trihalomethane which is most frequently produced. A statistical model was used which included repeated measurements of water parameters used for monitoring water quality at 51 sites covering the municipal water system of Montevideo. Samples were taken considering different seasons from June 2009 to July 2011 in Montevideo. Total samples (n?=?330) were analytically studied using the headspace-gas chromatography method coupled with mass spectrometry. Chloroform was the dependent variable and the covariables were pH, temperature, free chlorine, and total chlorine. A Tobit analysis with an unstructured correlation matrix was performed, and a significant interaction was found between pH and free chlorine for the prediction of chloroform formation. We concluded that parameters for the continuous control of water quality for consumption can be used to predict the levels of chloroform that may be present. Given the large measurement to variability found in the repeated measurements, the use of averages that include more than one season is not recommended to determine the degree of compliance with acceptable levels established by norms.     

重点行业企业用地地下水中挥发性有机物分析方法探究

通过优化顶空条件(氯化钠加入量、顶空平衡温度、顶空平衡时间),对采用顶空-气相色谱-质谱联用法测定地下水中55种挥发性有机物的方法进行探究。结果表明:该方法检出限为0.24~2.30μg/L,相对标准偏差为0.76%~13.2%,实际样品加标回收率为82.7%~119%。该方法具有较高的灵敏度、精密度和准确度,操作简便,可用于企业用地地下水中挥发性有机物的检测。     

The determination of carbonyl compounds in air using a robotic sampling preparation system integrated to a gas chromatograph with a nitrogen-phosphorus detector

A totally automated solid phase extraction gas chromatography procedure was developed for the sampling and analysis of carbonyl compounds in air. In this system, two PrepStation modules were used, one for the preparation and elution of 2,4-dinitrophenylhydrazine silica cartridges, and the other for air sampling. The sample collected by the sampling module was eluted to an autosampler vial in the PrepStation module and then transferred to the gas chromatograph for analysis via a robotic arm. The sampling module was modified to enable air sampling via an external pump. A typical run by this technique required 142 min, 100 min for air sampling and 42 min for the other operations, including a GC analysis time of 25 min. Recoveries of at least 85% were obtained for all compounds studied. The detection limits for formaldehyde, acetaldehyde and acetone were 2.2, 2.7 and 2.2 ppbv, respectively. All operations, including the conditioning of the cartridges, were performed without any intervention from the analyst.     

Application of portable gas chromatography-photo ionization detector combined with headspace sampling for field analysis of benzene, toluene, ethylbenzene, and xylene in soils

A method based on headspace (HS) sampling coupling with portable gas chromatography (GC) with photo ionization detector (PID) was developed for rapid determination of benzene, toluene, ethylbenzene, and xylenes (BTEX) in soils. Optimal conditions for HS gas sampling procedure were determined, and the influence of soil organic matter on the recovery of BTEX from soil was investigated using five representative Chinese soils. The results showed that the HS-portable-GC-PID method could be effectively operated at ambient temperature, and the addition of 15 ml of saturated NaCl solution in a 40-ml sampling vial and 60 s of shaking time for sample solution were optimum for the HS gas sampling procedure. The recoveries of each BTEX in soils ranged from 87.2 to 105.1 %, with relative standard deviations varying from 5.3 to 7.8 %. Good linearity was obtained for all BTEX compounds, and the detection limits were in the 0.1 to 0.8 μg kg^?1 range. Soil organic matter was identified as one of the principal elements that affect the HS gas sampling of BTEX in soils. The HS-portable-GC-PID method was successfully applied for field determination of benzene and toluene in soils of a former chemical plant in Jilin City, northeast China. Considering its satisfactory repeatability and reproducibility and particular suitability to be operated in ambient environment, HS sampling coupling with portable GC-PID is, therefore, recommended to be a suitable screening tool for rapid on-site determination of BTEX in soils.     

高效液相色谱法测定环境水样中嘧磺隆

环境水体中的嘧磺隆在ｐＨ＝２－３的Ｈ２ＳＯ４介质中用二氯甲烷萃取富集，然后用高压液相色谱法分离和紫外光（２５４ｎｍ）检测器检测，外标法定量。用此方法测定了井水和生产单位排放的综合污水中的嘧磺隆，结果满意，最大相对标准偏差为５％，样品加标回收率在９３～１０７％之间，最低检测限量为２ｎｇ，最低检出浓度为０．００４ｍｇ／Ｌ。     

Monitoring the Trihalomethanes Present in Water After Treatment with Chlorine Under Laboratory Condition

In this work assays involving chlorinated water samples, which were previous spiked with humic substances or algae blue green and following the production of the THMs for 30 days is described. To implement the assays, five portions of 1,000 ml of water were stored in glass bottles. The water samples were treated with solutions containing 2, 3, 4 and 5 mg l⁻¹ chlorine. The samples aliquots (60 ml) were transferred into the glass vials, 10 ml were removed to have a headspace and 100 μl of the 10 mg l⁻¹ pentafluortoluene bromide solution was added to each vial. The extraction step was performed by adding 10 g of Na₂SO₄ followed by 5 ml of n-pentane. The vials were stopped with a TFE-faced septum and sealed with aluminum caps. The generated THMs were determined by gas chromatography with electron capture detector using reference solutions with concentration ranging from 8 to 120 μg l⁻¹ THMs. Three assays were monitored during 30 days and chloroform was the predominant compound found in the water samples, while other species of THMs were not detected. The results showed that when the chlorine concentration was increased in water samples containing algae the concentration of THM varied randomly. Nevertheless, in water samples containing humic substances the increase of the THM concentration presented a relationship with the chlorine concentration. It was also observed that chloroform concentration increased with the elapsed time up to one and six days to water samples spiked with humic substances and algae blue green, respectively and decreased along 30 days. By other hand, assays performed using water samples containing decanted algae material showed that THM was not generated by the chlorine addition.     

高效液相色谱法测定地表水中四乙基铅

系统研究了地表水中四乙基铅的液相色谱分析方法,水中四乙基铅经二氯甲烷萃取浓缩后,用高压液相色谱柱分离,在280 nm波长处检测,根据保留时间定性,外标法定量,检出限及测定下限分别为0.02μg/L和0.06μg/L,低于地表水限值0.1μg/L,地表水平行测定的相对标准偏差均小于5%,地表水和废水样品加标回收率分别为79.4%～82.0%和62.5%～106.6%。     

Remediation of a nonachloro biphenyl congener with zero-valent iron in subcritical water

Dechlorination of a nonachloro biphenyl congener with zero-valent iron in water under high temperature and pressure was investigated over time. Temperature has the main influence on the speed of dechlorination. Determination of polychlorinated biphenyls (PCBs) according to the grade of chlorination was performed by gas chromatography with mass selective detection in single ion monitoring mode. Dechlorination results in a variety of lower chlorinated biphenyls. The level of chlorination decreases with time. The amount of PCB molecules decreases to one-third within 90 min at 250 degrees C and 100 atm. However, no increase of biphenyl could be detected over time. A first-order kinetic model fitted the data obtained.