降水中甲酸、乙酸和草酸的离子色谱法测定及样品保存研究

甲酸、乙酸和草酸是降水中有机酸的主要成分。研究选用离子色谱法同时测定降水中的甲酸、乙酸和草酸,并对降水样品中3种有机酸的保存条件进行了研究。优化后的色谱条件为4. 0 mmol/L Na_2CO_3和1. 2 mmol/L NaHCO_3混合淋洗液,淋洗液流速为1. 0 m L/min,进样体积为200μL,电导池温度为30℃,柱温为室温。甲酸、乙酸和草酸的检出限分别为0. 002、0. 005、0. 005 mg/L,实际降水样品测定时平行样的相对标准偏差为1. 4%～12%,加标回收率为95%～118%。样品采集后需尽快用0. 45μm聚醚砜微孔滤膜过滤,4℃以下冷藏密封保存,2 d内测定。若用氢氧化钠溶液调节p H至8～10,样品可保存7 d。     

Development of heat transfer and evaporation model of LNG covered by Hi-Ex foam

Natural gas is a kind of clean, efficient green energy source, which is used widely. Liquefied natural gas (LNG) is produced by cooling natural gas to −161 °C, at which it becomes the liquid. Once LNG was released, fire or explosion would happen when ignition source existed nearby. The high expansion foam (Hi-Ex foam) is believed to quickly blanket on the top of LNG spillage pool and warm the LNG vapor to lower the vapor cloud density at the ground level and raising vapor buoyancy. To identify the physical structure after it contacted with LN₂ and to develop heat transfer model, the small-scale field test with liquid nitrogen (LN₂) was designed. In experiment, three layers including frozen ice layer, frozen Hi-Ex layer and soft layer of Hi-Ex foam were observed at the steady state. By characterizing physical structure of the foam, formulas for calculating the surface of single foam bubble and counting foam film thickness were deduced. The micro heat transfer and evaporation model between cryogenic liquid and Hi-Ex foam was established. Indicating the physical structure of the frozen ice layer, there were a certain number of icicles below it. The heat transfer and evaporation mathematical model between the frozen ice layer and LNG was derived. Combining models above with the heat transfer between LNG, ground and cofferdam, the heat transfer and evaporation mathematical model of LNG covered by Hi-Ex foam was developed eventually. Finally, LN₂ evaporation rate calculated by this model was compared with the measured evaporation rate. The calculated results are 1.2–2.1 times of experimental results, which were acceptable in engineering and proved the model was reliable.     

高效液相色谱-二极管阵列检测器测定邻苯二甲酸酯色谱条件优化

采用高效液相色谱-二极管阵列检测器对6种PAEs类物质进行测定,并对梯度洗脱条件、流速、检测波长等影响化合物色谱响应的关键参数进行优化。综合考虑样品测试效率、分析精度、实际样品中存在杂质干扰等因素,确定以乙腈-水为流动相进行梯度洗脱,洗脱0~11 min流动相乙腈-水梯度比例为50∶50,11 min后流动相调整为100%乙腈,各化合物均能完全分离;色谱分析流速为0.8 m L/min;PAEs的最佳吸收波长为225 nm。在优化的色谱条件下,6种PAEs的线性良好,相关系数均大于0.999 8,仪器检出限为0.08~0.12 mg/L,保留时间、峰面积的相对标准偏差分别为0.02%~0.60%、0.13%~0.86%。方法灵敏度较高,适合土壤等邻苯二甲酸酯含量较高基质样品的快速分析。     

全二维气相色谱-飞行时间质谱法分离复杂体系中7种指示剂 多氯联苯

采用全二维气相色谱-飞行时间质谱法(GC×GC TOF-MS)分析了混标样品Aroclor 1260、Aroclor 1254、Aroclor 1242中的多氯联苯(PCBs)单体,考察了在复杂体系下对7种PCBs指示剂的分离能力。结果表明,与优化柱系统的分离效果相比,136种单体的混标样品中共分离出121种单体,7种指示剂经一维和二维的保留时间及质谱定性,在121种单体的2D斑点图中清晰可辨。全二维对于复杂体系的PCBs和指示剂的分离表明其强大的分离能力和对于检测复杂体系中指示剂的分辨能力,对该类物质的定性和定量检测具有重要意义。     

气相色谱-质谱法测定沉积物中的有机氯和多氯联苯

采用加速溶剂萃取法提取沉积物中的有机氯和多氯联苯,提取液用凝胶色谱法净化后用气相色谱-质谱法测定。方法在5.00μg/L~200μg/L范围内线性良好,当取样量为10.0 g时,方法检出限为0.03μg/kg~0.37μg/kg,空白样品2个质量比水平的加标回收率为70.8%~121%,测定结果的RSD为2.7%~11.5%。用该方法测定实际样品,结果 12个抽检的沉积物样品中多氯联苯均未检出,9个样品中有机氯检出。     

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。     

高效液相色谱-串联质谱法同时检测地表水中13种药物及个人护理品

采用高效液相色谱-串联质谱(HPLC-MS/MS)检测,建立了地表水中13种药物及个人护理品的测定方法。水样用盐酸与氢氧化钠溶液调p H值至7.0左右,过固相萃取小柱进行富集,用14 m L甲醇洗脱。以C18柱为分离柱,0.01%甲酸的甲醇-0.01%甲酸水溶液为流动相,目标物在10 min内分离,在0.50~250μg/L范围内,13种化合物峰面积与内标物质峰面积之比与质量浓度的线性关系良好(0.99),检出限在0.05~0.5 ng/L范围内。基质加标实验结果表明,13种化合物在水中的回收率分别在56.2%~123.2%之间(加标水平5 ng/m L)和58.0%~107.8%(加标水平50 ng/m L),相对标准偏差在1.60%~19.9%(n=6)之间。应用该方法测定了从2条纳污河流采集的10份水样,结果表明,除美托诺尔和普洛萘尔未被检出外,其余11药物的检出频率在30%~100%之间。在13种目标物质中,咖啡因的检测浓度最高达287.5ng/L,舒必利次之,为277.5 ng/L。本方法快速、准确,适用于地表水中PPCPs类的快速测定。     

苦味酸测定中关键问题的研究

目前测定苦味酸的国标方法为《生活饮用水标准检验方法有机物指标》(GB/T 5750.8—2006)中的衍生物-液液萃取-气相色谱法,在实际测试过程中,发现水样pH值和基质效应会影响苦味酸测定。当pH值为8~12时,生成的氯化苦响应强度变化不大;在pH约为13时,响应强度最大。水质中除腐殖酸、硝基甲烷及2,4,6-三硝基甲苯会影响苦味酸测定外,硝基酚类和甲基酚类同样起到正干扰作用,因此,国标方法不能全面和准确地测定水中的苦味酸含量。     

Pesticide residue removal in classic domestic processing of tomato and its effects on product quality

This study was undertaken to evaluate the effectiveness of several household practices (washing with water or acidic, alkaline, and oxidizing solutions, and peeling) in minimizing pesticide residue contamination of tomatoes, as well as the impact on the quality of the treated fruit. Tests were performed using two systemic fungicides (azoxystrobin and difenoconazole) and one contact fungicide (chlorothalonil). Solid-liquid extraction with low temperature partition (SLE/LTP) and liquid-liquid extraction with low temperature partition (LLE/LTP) were used to prepare the samples for pesticides determination by gas chromatography. Washing the tomatoes with water removed approximately 44% of chlorothalonil, 26% of difenoconazole, and 17% of azoxystrobin. Sodium bicarbonate (5%) and acetic acid (5%) solutions were more efficient, removing between 32 and 83% of the residues, while peeling removed from 68 to 88% of the pesticides. The washing solutions altered some fruit quality parameters, including acidity and chroma, and also caused weight loss. Acetic acid (0.15 and 5%) and hypochlorite (1%) solutions had the greatest effect on these parameters.     

顶空固相微萃取-气相色谱法测定水中氯苯类化合物

采用顶空固相微萃取（HS －SPME）技术萃取水中6种氯苯类化合物，全面分析对目标物萃取效率的影响因素，并确定萃取试验的最佳条件。用顶空固相微萃取联合气相色谱法（HS －SPME －GC）测定水中6种氯苯类化合物，方法在0.500 ng／L～2.00×10^5 ng／L范围内线性良好，检出限为0.05 ng／L ～2000 ng／L，空白样品加标回收率为69.8％～121％， RSD为4.8％～18.3％。用该方法测定实际水样，平行双样的相对偏差低于20％。