1 / 20

磷， NOx

磷， NOx. 安 排. 预习时： 清洗实验 2.11 磷测定 ( 快速消解法 ) 所需器皿。 采集实验 3.2 大气 NOx 样品，清洗 3.2 所需器皿。 考虑 2 周后的自主实验。 实验： 上午，磷的测定，考试实验。 下午，测定大气 NOx 。. 2.11. Determination of Orthophosphates. Purpose:

buzz
Download Presentation

磷， NOx

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 磷， NOx

  2. 安 排 预习时： • 清洗实验2.11磷测定(快速消解法)所需器皿。 • 采集实验3.2大气NOx样品，清洗3.2所需器皿。 • 考虑2周后的自主实验。 实验： • 上午，磷的测定，考试实验。 • 下午，测定大气NOx。

  3. 2.11. Determination of Orthophosphates Purpose: • To understand the principles of determination of orthophosphate, and to master one of the sample pretreatment methods, oxidative digestion. • To get familiar with the operation of UV-Vis spectrophotometer.

  4. Sample Filter (through 0.45μm membrane) Digestion Total phosphorus Residue Solution Digestion • Dissolved Orthophosphate Dissolved Total Phosphorus

  5. Samples: • Diluted organophosphorous pesticide waste water • One blank and one sample for each student.

  6. Method principle • Phosphoantimonylmolybdenum blue method • Maximum absorbance wavelength at 700-900 nm. • Calibration curve for quantification. • Digestion to get total phosphates.

  7. Procedure 1. Digestion diluted waste water + oxidizing reagent 160℃ for 15min 2. Color development transferring, adding reagents, preparing calibration curve 3. Detection 700 nm, water as the reference

  8. Questions • Should the solutions of the calibration curve be digested as the samples? And why? • Yes. • Do we need to add the color developing reagents accurately? • Yes.

  9. 3.2. Determination of Nitrogen Oxides (NOx) Purpose: • To understand the principle of determination of NOx, • and to grasp the method of NOx determination and the use of spectrophotometer; • as well as to master one of the air sampling methods, solution absorption.

  10. Method principle • NO2 in the air is dissolved in the absorbing solution and forms nitrous acid. • Nitrous acid reacts with sulfanilic acid, then couples with N-(1-naphthyl)-ethylenediamine dihydrochloride and forms rose-colored azo dye. • The determination of azo dye is carried out at 540 nm.

  11. Air CrO3 Drying Pump Waste Bottle Soln NOx = NO + NO2 + N2O

  12. Production of NOx in the lab 3 Cu + 8 HNO3(diluted) = 3 Cu(NO3)2 + 2 NO + 4 H2O Cu + HNO3 = Cu(NO3)2 + 2 NO2 + 2 H2O 4 HNO3 + (heat) = 4 NO2 + 2 H2O + O2

  13. Procedure • Collect the sample 2. Prepare the calibration curve 3. Detection at 540 nm

  14. Additional Questions • What are the possible factors to cause the method blank? • Is the NOx level you determined within the normal range?

  15. calculation • NOx (μg/m3) = Calibration curve: Y = bX + a Here, Bs = 1/b; A0 = a

  16. 什么是空白 包括现场空白、仪器空白和方法空白。以水样为例。 • 现场空白：在采样现场带上纯水。经历与其他样品相同的采集、储存、运输、分析全过程。 • 仪器空白(溶剂空白)：不含目标物的水或溶剂为样品，经历仪器分析的全过程。 • 方法空白(样品制备空白) ：不含目标物的水或溶剂为样品，经历样品预处理和仪器分析的全过程。

  17. 空白值只能说明是否玷污，不能说明玷污有多少。空白值只能说明是否玷污，不能说明玷污有多少。 测定结果能不能扣除空白？ • 如果用的是工作曲线法，分光光度测定中可以扣除空白。 • 如果是单点测定，一般不宜扣除空白。除非测定20次，且偏差在允许范围内。 • Excel“趋势线格式”中选择截距不为零。

  18. 空白 • 空白值指试剂经过同样的样品处理后的吸光值，即被测物浓度为零的样品吸光值。 • 空白有化学意义，用于检验试剂的纯度和样品处理过程的玷污程度。 • 报告数据时必须报告空白值。 * 偏差 * * * * * * * * *

  19. 工作曲线是否可以过原点？ • 试剂在工作曲线的其他点的溶液中同样存在，量也一样，处理过程一样，因此空白应当成为工作曲线上的一个点。空白所在的点不等于原点。没有理由要求工作曲线通过每一个点。 * 偏差 * * * * * * * * *

  20. 可以在样品测值中扣除空白的吸光值，即使工作曲线平移。但工作曲线不应强求过原点。可以在样品测值中扣除空白的吸光值，即使工作曲线平移。但工作曲线不应强求过原点。 • 如果以空白做参比，则无法得知试剂的污染程度。即使以空白做参比，工作曲线仍然不应强求过原点。 * * * * * * * * * *

More Related