Table 3.

Summary table showing advantage and limitation of common method of sample preparation before quantification.

Type	Methods	Merits	Limitation	Practicality	References
Direct injection	This method introduces the sample directly into an analytical instrument without any prior sample preparation.	Fast, convenient, and inexpensive. No training is special training or equipment needed. No solvent needed.	Lower sensitivity and accuracy due to the presence of matrix components and contaminants. Cannot be used with less sensitive analytical instruments. Cannot be used when the target concentration is very low. Recovery is always low compared to other methods.	Can be used with caution.	Thai et al. (2019); Xie et al. (2022).
aDilute and shoot	In the dilute and shoot method, a sample is first diluted to reduce matrix interference and then introduced into an analytical instrument.	Improve the sensitivity and accuracy of the analysis. Avoid matrix effect observable with traditional direct injection.	Require dilution with water. Requires careful optimization of the dilution factor to avoid loss of target analytes. Compounds need to show sufficient ionization to be successfully determined by the dilute and shoot method.	It can be used with caution.	Rico et al. (2017).
aLarge Volume Injection	A large volume of sample is introduced into an analytical instrument	The number of target analytes present in the sample can be increased. It is a valuable method for trace analysis and the detection of low-concentration analytes.	It can result in interference from matrix components and contaminants.	It can be used with caution.	Cantwell et al., 2019.
Liquid-Liquid	In liquid-liquid extraction, target analytes are separated from a sample matrix by partitioning them between two immiscible liquids	Simple and cost-effective method. No special instrument needed. Avoid matrix effect observable with traditional direct injection. Faster than the SPE method.	Needs extraction solvents. Requires careful optimization of solvent and extraction time to achieve optimal yield and selectivity.	It can be used with the proper selection of extraction solvent.	Chen et al. (2014).
Solid phase	a sample is passed through a solid sorbent material, where the target analytes are selectively adsorbed onto the sorbent based on their physicochemical properties. The sorbent can be made of different materials, such as silica, polymer, or resin	Solid phase extraction method is a selective and efficient method for sample preparation. Reduce the effect of the matrix effect. It can be used with both sensitive and less sensitive analytical instruments. Different adsorbents can be used, which provides flexibility.	Needs extraction solvents. Needs clean up. High operational cost. It requires more time and resources than other methods. The sorbents could poorly or strongly retain analyte due to their polarity.	It can be used with a proper selection of adsorbent.	Esperanza et al. (2004); Chen et al. (2014); Pandopulos et al. (2021).

^aTypes of direct injection.