**1. Introduction**

Most samples are not ready to introduce directly into the column of gas chromatography (GC) instrument [1–7]. So, the sample preparation is the most important step prior to GC determination of an analyte. There might be several processes within sample preparation which depend on the complexity of the sample; the analyte concentration level in the sample and its level need to be analyzed by the GC instrument. On the other hand, sample preparation is often a severe process that accounts for the complexity of the analyte analysis. Instance for organics and volatile organics, the sample preparation procedures can be mentioned such as extraction, cleanup, derivatization, transfer to vapor phase, and concentration.

Before analyzing a sample by GC, the sample preparation procedure should be reviewed to some important constraints such as accuracy, precision, cost, the amount of available laboratories, the analysis time consumption, and the possibility of method automation. Since analytical instruments, like GC, have become quite sophisticated and then provide high levels of accuracy and precision, sample preparation step has been accounted for the majority of the variability. For instance, the sample preparation might involve several discrete steps and also manual handling and take some days, whereas the GC analysis can be performed in a matter of minutes. Therefore, typically two-thirds of the time in GC analysis can be spent on sample preparation. It is worth noting that better improvement in the GC analysis can be brought by significantly simpler sample preparation processes. Some suitable approaches to reducing uncertainty during sample preparation are minimizing the number of steps and using appropriate techniques. On the other hand, the greater the number of steps, the more error there are. So, if it is possible, one or more sample preparation steps should be eliminated. Also, the choice of an appropriate method for sample preparation can improve precision.

The goal should be to choose a combination of sample preparation and GC instrumentation to reduce both of the number of sample preparative steps and relative standard deviation (RSD) and/or increasing precision. Sample preparation step can affect some other quantitative statistical parameters such as limit of detection (LOD), limit of quantitation (LOQ ), limit of linearity (LOL), and linear dynamic range (*LDR*). Limit of detection (LOD) is defined as the lowest concentration or weight of analyte which can be determined at a specific confidence level. The lowest concentration level at which a measurement is quantitatively meaningful is called limit of quantitation (LOQ ). For all practical purposes,

**47**

*Sample Preparation Techniques for Gas Chromatography DOI: http://dx.doi.org/10.5772/intechopen.84259*

the upper limit of quantitation is the point where the calibration curve becomes nonlinear. This point is called the limit of linearity (LOL). The range of analyte concentration which possesses linearity toward instrumental signal is called linear dynamic range (LDR). Considering all these, the recovery in sample preparation method is an essential parameter which affects quantitative issues such as detection limit, sensitivity, LOQ, and LOL. The sample preparation methods which enhance performance result in larger recovery, higher sensitivity, and lower detection limits. Also, other important parameters in choosing an appropriate sample preparation method include higher speed procedures or use of online methods, low cost, and

less reagent consumption or use of greener sample preparation methods.

2.Determination of the detection limit for each analyte in the sample.

typical validation process includes the following steps:

techniques that have a common list of aims such as [3]:

selectivity of the both separation and detection stages.

1.Using smaller initial sample sizes even for trace analyses.

2.The increase of analyte concentration and sensitivity.

the GC method is used.

existing methods [2].

separate.

of the sample matrix.

online techniques.

trends in recent years have been toward to [3]:

2.Achieving higher specificity and selectivity.

Before a new sample preparation procedure is used, it must be validated. The different figures of merit should be determined during the validation process. A

1.Determination of the random and systematic errors in terms of precision and bias.

3.Determination of the accuracy and precision at the concentration range where

4.Measurement of the linear dynamic range and the calibration sensitivity.

Generally, method validation provides not only a comprehensive picture of merits of a new sample preparation method but also a useful comparison with other

As mentioned above, the main concept of a sample preparation method is to convert a real matrix into a sample format which is suitable for analysis by a separation or other analytical methods. This can be approached by using a wide range of

1.The removal of serious interferences from the sample in order to increase the

3.To convert the analyte into a more suitable form to detect, determine, and/or

4.To apply more reproducible techniques which do not depend on the variations

Although some traditional sample preparation techniques are still in use, the

3.To reduce manual operations and to improve potential for automation or

with less or no use of organic solvents and less waste production.

4.To approach to a more environmentally friendly methods (green chemistry)

## *Sample Preparation Techniques for Gas Chromatography DOI: http://dx.doi.org/10.5772/intechopen.84259*

*Gas Chromatography - Derivatization, Sample Preparation, Application*

ways to treat and convert matrix into a suitable sample to inject GC.

**Keywords:** sample treatment, green chemistry, extraction methods,

method for sample preparation can improve precision.

The goal should be to choose a combination of sample preparation and GC instrumentation to reduce both of the number of sample preparative steps and relative standard deviation (RSD) and/or increasing precision. Sample preparation step can affect some other quantitative statistical parameters such as limit of detection (LOD), limit of quantitation (LOQ ), limit of linearity (LOL), and linear dynamic range (*LDR*). Limit of detection (LOD) is defined as the lowest concentration or weight of analyte which can be determined at a specific confidence level. The lowest concentration level at which a measurement is quantitatively meaningful is called limit of quantitation (LOQ ). For all practical purposes,

solid-phase extraction, cleanup

**1. Introduction**

different samples possess a variety of sample treatment methods, for example: (1) In order to treat solid samples and separate a purpose analyte, some enhanced solvent extraction methods include pressurized liquid extraction, microwave- and sonic wave-assisted extraction, supercritical fluid extraction, and superheated water extraction. (2) For analytes in solution, the sample preparation can be attributed to the analyte trapping methods such as -phase extraction, solid-phase microextraction, and stir bar extractions. (3) Also, the extraction of the analytes into a liquid phase can be achieved by other methods like membrane extraction, single-drop microextraction (SDME), and purge and trap. (4) For separation of analytes in the gas phase, trapping analytes from vapor samples and headspace analysis are used. As a result, sample preparation is not only a critical step but also possesses different

Most samples are not ready to introduce directly into the column of gas chromatography (GC) instrument [1–7]. So, the sample preparation is the most important step prior to GC determination of an analyte. There might be several processes within sample preparation which depend on the complexity of the sample; the analyte concentration level in the sample and its level need to be analyzed by the GC instrument. On the other hand, sample preparation is often a severe process that accounts for the complexity of the analyte analysis. Instance for organics and volatile organics, the sample preparation procedures can be mentioned such as extraction, cleanup, derivatization, transfer to vapor phase, and concentration. Before analyzing a sample by GC, the sample preparation procedure should be reviewed to some important constraints such as accuracy, precision, cost, the amount of available laboratories, the analysis time consumption, and the possibility of method automation. Since analytical instruments, like GC, have become quite sophisticated and then provide high levels of accuracy and precision, sample preparation step has been accounted for the majority of the variability. For instance, the sample preparation might involve several discrete steps and also manual handling and take some days, whereas the GC analysis can be performed in a matter of minutes. Therefore, typically two-thirds of the time in GC analysis can be spent on sample preparation. It is worth noting that better improvement in the GC analysis can be brought by significantly simpler sample preparation processes. Some suitable approaches to reducing uncertainty during sample preparation are minimizing the number of steps and using appropriate techniques. On the other hand, the greater the number of steps, the more error there are. So, if it is possible, one or more sample preparation steps should be eliminated. Also, the choice of an appropriate

**46**

the upper limit of quantitation is the point where the calibration curve becomes nonlinear. This point is called the limit of linearity (LOL). The range of analyte concentration which possesses linearity toward instrumental signal is called linear dynamic range (LDR). Considering all these, the recovery in sample preparation method is an essential parameter which affects quantitative issues such as detection limit, sensitivity, LOQ, and LOL. The sample preparation methods which enhance performance result in larger recovery, higher sensitivity, and lower detection limits. Also, other important parameters in choosing an appropriate sample preparation method include higher speed procedures or use of online methods, low cost, and less reagent consumption or use of greener sample preparation methods.

Before a new sample preparation procedure is used, it must be validated. The different figures of merit should be determined during the validation process. A typical validation process includes the following steps:


Generally, method validation provides not only a comprehensive picture of merits of a new sample preparation method but also a useful comparison with other existing methods [2].

As mentioned above, the main concept of a sample preparation method is to convert a real matrix into a sample format which is suitable for analysis by a separation or other analytical methods. This can be approached by using a wide range of techniques that have a common list of aims such as [3]:


Although some traditional sample preparation techniques are still in use, the trends in recent years have been toward to [3]:

1.Using smaller initial sample sizes even for trace analyses.


On the other hand, different samples possess a variety of sample treatment methods. Therefore, in this chapter, by paying attention to the type of sample matrix, information required (quantitative or qualitative), and sensitivity required, the sample preparation methods used before GC analyses are discussed.
