浅谈光度法中进行信量稀释的几个问题

《水与废水监测分析方法》(以下简称《方法》)中,关于酚二磺酸光度法测定硝酸盐氮介绍:“如吸光度值超出校准曲线范围,可将显色溶液用水进行信量稀释,然后再测量吸光度,计算时乘以稀释倍数”. 对于应用信量稀释法,本文浅谈如下几个问题: 1.被信量稀释之显色溶液,必须是被测组分完全反应后所生成的全溶显色溶液.如若被测组分含量太高,不能完全参加反应,即尚有部分被测组分没有参加反应,其经信量稀释后测定的结果将会比实     

比色法测定水中微量三氯杀螨醇

使用比色法测定水中微量三氯杀螨醇的浓度。首先用正己烷萃取浓缩水中的三氯杀螨醇,比较了加入不同量的去离子水,不同浓度、不同量的NaOH,不同的反应显色温度和反应时间以及吡啶用量等对体系吸光度的影响。得出最佳的显色条件:0.2ml去离子水,0.1ml质量浓度为45%的NaOH溶液,与2.0ml吡啶混合,于100℃水浴中反应3.0min,反应液在4000r/min离心2.0min,取出反应液在530nm处测定吸光度值。此方法的标准工作曲线相关系数为0.9914,方法的绝对检出限为0.2μg三氯杀螨醇。样品加标回收率为83.7%~114.1%,相对标准偏差小于10%。     

水质硫化物直接吸收显色法中前置气体分离管存在的缺点和替换方法

介绍了直接吸收显色法分析水质硫化物中，气体分离管在实际操作中存在的缺点和氢氧化钾溶液替换气体分离管的优点，并通过实验来论证替换的可行性。     

主动采样法采集博物馆空气中微量污染气体

根据博物馆污染气体的种类,对气体主动采样法进行了采样器种类、吸收液种类和浓度、吸收液体积的选择。验证了气体采样流量、采样时间与气体采样浓度的线性关系,确定了酸性和碱性污染气体的主动采样方法,为监测文物保存环境污染气体提供了可行方法。     

U型多孔玻板吸收管快速充液法

U型多孔玻板吸收管以其吸收效率高,广泛应用于气体监测采样中,但该器皿在使用中不易充液,而有些气体如SO_2、NO_x等对吸收液的体积有着精确的要求.一般充液采用的方法不外乎以下两种:     

用酶免疫法测定二噁

1　前言近年来 ,由于酶免疫测定法 (ＥＬＩＳＡ)具有选择性好、灵敏度高和分析速度快等优点 ,在水、土壤和固体废弃物等环境监测方面得到广泛的应用 ,现被正式批准为法定分析方法。2　原理一般是利用试样特性结合生成两种抗原抗体 ,即试样和具有相似化学物质的认记部位使酶标记复合物发生竞争反应。在酶免疫测定法 (ＥＬＩＳＡ)的竞争反应时 ,因对于各自存在量都按一定比例参加反应 ,加入酶基质等会出现显色反应 ,所以酶复合物的结合量通过测定吸光度求出。在测定试样少时 ,酶复合物结合的酶多 ,显色反应的颜色深 ,表示吸光度值高 ,相反 ,测…     

硫化物测定中吹气装置的改进

以氮气为载气,硫化物在酸性介质中生成H_2S被赶出,再被乙酸钠-乙酸锌溶液吸收,然后显色测定的亚甲兰光度法是废水硫化物测定中被广泛应用的标准测定方法。该法在实际应用中发现,某些细节问题和操作技术掌握不当及吹气装置本身的缺陷,会道成方法的回收率严重偏低。前两个问题讨论得较多,如硫化钠标准溶液可用硫化锌悬浊液代替,以提高标准溶液的稳定性;加酸前进行预吹气;吸收导管与吸收液一并进行显色处理,单管吸收和两管串联吸收的回收率相差不大等,这些问题的解决都有利于回收率的提高。可是,吹气装置本身的问题却很少见提出。我们在实践中对装置中吹气和吸收两部分进行了改进,用市售的大口瓶代替反应瓶,用带筛板的导管代替吹气管和吸收管,经试验该装置可使方法的回收率大大提高,结果令人满意。     

甲醛吸收液用量对测定空气中二氧化硫的影响

在相同采样方法条件下，用不同量的甲醛吸收液测定空气中二氧化硫，吸收液量大，测定结果低，适当减少采样时的吸收液量，能提高监测数据的准确性。     

采样条件对固定排放源废气中氯化氢测定的影响

研究了采样条件对固定排放源废气中氯化氢测定的影响。结果发现,采样条件对测定的准确度影响极大,过低的吸收液浓度会导致测定结果严重偏低,进入吸收装置的气体温度过低时也会导致测定结果偏低。目前常用的采样条件(包括有些标准中规定的采样条件)都不合适。推荐合适的Na OH吸收液浓度为2.0 mol/L,合适的进入吸收装置的气体温度为110℃以上。     

离子色谱法测定二氧化硫

目前测定空气中的二氧化硫普遍使用监酸付玫瑰苯胺比色法,以毒性较大的四氯汞钾作吸收液,有报导使用甲醛为吸收液.文献报导空气中二氧化硫采样时在吸收管前加上一根内贮银粉,硫酸亚铁的洗气管以消除干扰,结果与真实情况较符合.但比色法存在的问题是测量范围较狭,当二氧化硫含量超出标准曲线范围时一经显色就无法弥补.     

化学吸收法采集固定污染源氨气的影响因素探究

固定污染源氨气的手工监测，干扰因素较多，其中采样环节尤为关键。实验通过催化氧化-化学发光法考察不同采样管线材质对氨气的吸附效果，离子色谱法考察化学吸收法采集氨气的吸收瓶类型、采样流量、吸收液种类、吸收液浓度及体积等采样条件对氨气吸收效率的影响。实验表明，316 L不锈钢与聚四氟乙烯对氨气的吸附较小，氨气的采样流量不宜超过1.0 L/min,棕色气泡式吸收瓶更适用于氨气样品的采集，磷酸溶液作吸收液对氨气的吸收效率较好，对于低浓度的氨气样品，应采用低流量长时间采集。     

高效液相色谱法测定地表水中硝基苯类化合物

建立了液相色谱法直接测定水中的10种硝基苯类化合物的方法,C18色谱柱为分离柱,检测波长为254 nm,以甲醇和水为流动相,前处理过程水和甲醇以9∶1的体积比混合,水样过微孔滤膜后直接进液相色谱分析。该法分析10种硝基苯类化合物的检出限为4.3~5.5μg/L,加标回收率为79%~136%,精密度为6.8%~13%,符合监测要求。     

超高效液相色谱三重四极杆质谱联用法测定水中的丙烯酰胺

将含有丙烯酰胺的水样过滤后加入甲酸酸化,然后直接进样,使用超高效液相色谱三重四极杆质谱联用法测定,通过选择离子反应监测,可实现定性和外标法定量分析.该方法测定生活饮用水及其水源水中丙烯酰胺的最低检测浓度为0.15 g/L,对实际样品的加标回收率在92％ ～ 123％,该方法绿色环保、简单方便,且具有较高的灵敏度和较低的检出限.     

大气硝基苯标准曲线绘制方法的改进

标准曲线绘制时,各浓度点都要取过滤液2.0ml,此操作繁琐、费时。现改成取过滤液5.0ml,用10ml比色管进行分析,得到操作简便和省时的效果。另外,对调pH值方法、显色反应水温的操作也作了改进。     

支撑离子液体膜微萃取-气相色谱法测定水中有机氯农药

摘要：将l-丁基-3-甲基咪唑六氟磷酸离子液体固定于无纺布上形成支撑离子液体膜，结合液相微翠取技术对水样中的有机氯农药进行分离与富集，并用气相色谱法测定。通过试验对影响萃取效率的有关条件进行优化，使该方法在0．500μg／L～10．0μg／L范围内线性良好。方法检出限为0．02μg／L～0．08μg／L，测定0．04μg／L的混合标准溶液平均回收率为75．0％～87．3％，RSD〈7％。     

气相色谱法中液体样品的进样技术

阐述了气相色谱中液体样品的4种进样技术。     

气相色谱法测定环境空气中乙醇和异丙醇

采用蒸馏水吸收空气中的乙醇和异丙醇，气相色谱法测定，该方法在3．14 mg/L ～15．8 mg/L 范围内线性良好，乙醇标准曲线的相关系数为0．9994，异丙醇标准曲线的相关系数为0．9996。测定低浓度标准溶液，得到乙醇和异丙醇的检出限分别为0．418 mg/L 和0．399 mg/L；采样体积为0．04 m3时，乙醇和异丙醇最低检出质量浓度均为0．05 mg/m3。乙醇和异丙醇标准溶液的回收率为95．4％～104％，RSD＜5％。样品稳定性试验表明，采集的乙醇和异丙醇样品保存时间越长损失率越大，一般保存7 d为宜。     

Contaminant exposure in outmigrant juvenile salmon from Pacific Northwest estuaries of the United States

To better understand the dynamics of contaminant uptake in outmigrant juvenile salmon in the Pacific Northwest, concentrations of polychlorinated biphenyls (PCBs), DDTs, polycylic aromatic hydrocarbons (PAHs) and organochlorine pesticides were measured in tissues and prey of juvenile chinook and coho salmon from several estuaries and hatcheries in the US Pacific Northwest. PCBs, DDTs, and PAHs were found in tissues (whole bodies or bile) and stomach contents of chinook and coho salmon sampled from all estuaries, as well as in chinook salmon from hatcheries. Organochlorine pesticides were detected less frequently. Of the two species sampled, chinook salmon had the highest whole body contaminant concentrations, typically 2--5 times higher than coho salmon from the same sites. In comparison to estuarine chinook salmon, body burdens of PCBs and DDTs in hatchery chinook were relatively high, in part because of the high lipid content of the hatchery fish. Concentrations of PCBs were highest in chinook salmon from the Duwamish Estuary, the Columbia River and Yaquina Bay, exceeding the NOAA Fisheries' estimated threshold for adverse health effects of 2400 ng/g lipid. Concentrations of DDTs were especially high in juvenile chinook salmon from the Columbia River and Nisqually Estuary; concentrations of PAH metabolites in bile were highest in chinook salmon from the Duwamish Estuary and Grays Harbor. Juvenile chinook salmon are likely absorbing some contaminants during estuarine residence through their prey, as PCBs, PAHs, and DDTs were consistently present in stomach contents, at concentrations significantly correlated with contaminant body burdens in fish from the same sites.     

Mobile monitoring along a street canyon and stationary forest air monitoring of formaldehyde by means of a micro-gas analysis system

A micro-gas analysis system (μGAS) was developed for mobile monitoring and continuous measurements of atmospheric HCHO. HCHO gas was trapped into an absorbing/reaction solution continuously using a microchannel scrubber in which the microchannels were patterned in a honeycomb structure to form a wide absorbing area with a thin absorbing solution layer. Fluorescence was monitored after reaction of the collected HCHO with 2,4-pentanedione (PD) in the presence of acetic acid/ammonium acetate. The system was portable, battery-driven, highly sensitive (limit of detection = 0.01 ppbv) and had good time resolution (response time 50 s). The results revealed that the PD chemistry was subject to interference from O(3). The mechanism of this interference was investigated and the problem was addressed by incorporating a wet denuder. Mobile monitoring was performed along traffic roads, and elevated HCHO levels in a street canyon were evident upon mapping of the obtained data. The system was also applied to stationary monitoring in a forest in which HCHO formed naturally via reaction of biogenic compounds with oxidants. Concentrations of a few ppbv-HCHO and several-tens of ppbv of O(3) were then simultaneously monitored with the μGAS in forest air monitoring campaigns. The obtained 1 h average data were compared with those obtained by 1 h impinger collection and offsite GC-MS analysis after derivatization with o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBOA). From the obtained data in the forest, daily variations of chemical HCHO production and loss are discussed.