The measurement process

The purpose of an analytical study is to obtain information about some object or substance. The substance could be a solid, a liquid, a gas, or a biological material. The information to be obtainedcan be varied.1__________________. Despite the sophisticated arsenal of analytical techniques available, it is not possible to find every bit of information of even a very small number of samples. For the most part, the state of current instrumentation has not evolved to the point where we can take an instrument to an object and get all the necessary information. Although there is much interest in such noninvasive devices, most analysis is still done by taking a part of the object under study and analyzing it in the laboratory or at the site. Some common steps involved in the process are shown below.

1. Sampling		2. Sampling preservation		3. Sample preparation		4. Analysis

The first step is sampling, where the sample is obtained from the object to be analyzed. This is collected such that it represents the original object. Sampling is done with variability within the object in mind. For example, while collecting samples for determination of Ca ²⁺in a lake, it should be kept in mind that its concentrations can vary depending on the location, the depth, and the time of year. 2.___________This is an important step, because there is usually a delay between sample collection and analysis. Sample preservation ensures that the sample retains its physical and chemical characteristics so that the analysis truly represents the object under study. Once the sample is ready for analysis, sample preparation is the next step. Most samples are not ready for direct introduction into instruments. For example, in the analysis of pesticides in fish liver, it is not possible to analyze the liver directly. 3._____________There might be several processes within sample preparation itself. Some steps commonly encountered are shown below.

1. Homogenization		2. Extraction		3. Concentration		4. Clean-up		5. Analysis

However, they depend on the sample, the matrix, and the concentration level at which the analysis needs to be carried out. For instance, trace analysis requires more stringent sample preparation than major component analysis.4.________________ A variety of instruments are used for different types of analysis, depending on the information to be acquired: for example, chromatography for organic analysis, atomic spectroscopy for metal analysis, capillary electrophoresis for DNA sequencing, and electron microscopy for small structures. The sample preparation depends on the analytical techniques to be employed and their capabilities. 5.______________ .So the importance of the prior steps, in particular the sample preparation, cannot be under stressed.

1.-c, 2-d, 3-a, 4-b,5-e

b. Complete the definitions below with the words from the box.

Available liver To obtain Noninvasive Capability Variability Stringent Encounter Prior Employ

1. To……………..means to get something.

2. If something is…………..it is easy of access.

3. ……………….is a large organ in the body which cleans blood.

4. ……………………means without any contact, hands free.

5. …….................is diversity or a range to choose from.

6. If you ………………..it means you come across or meet something.

7. ………………..means to be accurate or precise.

8. …………….means to apply or to use.

9. ……….is the quality of having the power or skills needed.

10. ………………….is located before.

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