Separation and Extraction Techniques

  • separation techniques
  • sample preparation
  • treatment of data


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Precipitation  works by obtaining a chemical interaction between two chemicals as selective as possible and with a solubility constant as low as possible, which will make the product of the reaction unstable in solution.


L-L extraction is a method to separate compounds based on their relative solubility  in two different immiscible liquids, usually water and an organic solvent

It can be performed without chemical  changing or can be assisted with different  reactions to enhance selectivity,  by  changing pH -transformation of ionic  compounds, soluble in water, into neutral  species, soluble in an organic solvent;  adding ligands to favor complexation  reactions –i.e. extraction of metals



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techniques (con't)

Distillation is a technique to separate  mixtures based on differences in their volatilities in a boiling liquid mixture. It is one of the oldest separation methods.


Lixiviation   is the process of separating soluble from insoluble substances by dissolving the former in water or some other solvent.


Solid-phase extraction (SPE) is a separation process that is used to remove compounds from a mixture of impurities based on their physical and chemical properties.

Forensic laboratories use solid phase extraction to concentrate and purify samples prior to analysis


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Sample treatment

Internal Standards are added in a constant amount to samples in order to guarantee that the analysis is performed without problems, they also help to minimise errors when used in the calibration curve    


The Internal Standard need to have similar chemical structure and properties that the analytes I want to study, but they cannot interfere with the analysis. As they have similar properties they will behave similarly during the process.


 Blanks              ensure the elimation of Contamination of the system from previous analysis i.e carry over,It also gives valuable information such as Baseline signal and Limit of detection 

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treatment of data (cont')

Control samples are any type of well-known forensic samples used to assure analyses are properly performed so that results are reliable (Certified Reference Materials or CRM)


Control samples are an important part of quality control and assurance procedures that forensic scientists use to eliminate the inaccuracy of laboratory results


Now we have some results obtained from our instrument. We know they have No carry over, because we have performed a blank. We also know that the Instrument is behaving because we have run a control sample.

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