问题 单项选择题

水中有机氯农药测定方法有比色法、薄层法和气相色谱法等,其中灵敏度最高,且被广泛应用的方法是()

A.比色法

B.薄层法

C.气相色谱法-氢火焰离子化检测器

D.气相色谱法-电子捕获检测器

E.气相色谱法-火焰光度检测器

答案

参考答案:D

解析:一般水中有机氯农药含量很低,通常用气相色谱-电子捕获法测定。采用的富集方法是环己烷或石油醚萃取,但有时溶剂峰变宽,干扰六六六出峰,需重蒸馏至无干扰峰出现。

阅读理解

阅读理解。

     This is a great truth, one of the greatest truths. It is a great truth because once we truly see this truth,

we transcend (超越) it. Once we truly know that life is difficult-once we truly understand and accept it-then

life is no longer difficult. Because once it is accepted, the fact that life is difficult no longer matters.

     Most do not fully see this truth. Instead they complain about their problems and difficulties as if life should

be easy. It seems to them that difficulties represent a special kind of suffering especially forced upon them or

else upon their families, their class, or even their nation.

     What makes life difficult is that the process of facing and solving problems is a painful one. Problems,

depending on their nature, cause us sadness, or loneliness or regret or anger or fear. These are uncomfortable

feelings, often as painful as any kind of physical pain. And since life causes an endless series of problems, life

is always difficult and is full of pain as well as joy.

     Yet, it is in this whole process of solving problems that life has its meaning. Problems are the serious test

that tells us success from failure. When we desire to encourage the growth of human spirit, we encourage the

human ability to solve problems, just as in school we set problems for our children to solve. It is through the

pain of meeting and working out problems that we learn. As Benjamin Franklin said, those things that hurt,

instruct. It is for this reason that wise people learn not to fear but to welcome the pain of problems.

1. From the passage, it can be inferred that ______.

A. everybody has problems

B. we become stronger by meeting and solving the problems of life

C. life is difficult because our problems bring us pain

D. people like to complain about their problems

2. The writer probably used just one short sentence in the first paragraph to ______.

A. save space

B. persuade readers

C. make readers laugh

D. get readers' attention

3. The main idea of Paragraph 3 is that ______.

A. most people feel life is easy

B. the writer feels life is easy

C. the writer likes to complain about his problems

D. most people complain about how hard their lives are

4. According to the passage, we give school children difficult problems to solve in order to______.

A. encourage them to learn

B. teach them to fear the pain of solving the problem

C. help them learn to deal with pain

D. teach them how to respect from problems

5. The saying from Benjamin Franklin "Those things that hurt, instruct" suggests that ______.

A. we do not learn from experience

B. we do not learn when we are in pain

C. pain teaches us important lessons

D. pain cannot be avoided

填空题