Solid phase micro extraction

A solvent less technique used to prepare sample.

1. Presentation Topic: solid phase Microextraction Presented to: Doctor Zubair Presented by: Sania Bibi 17110807-005 MSc I chemistry Course: Basic Analytical chemistry I Theory CHEM-339

2. solid phase micro extraction

3. Introduction of SPME SPME is a simple and efficient technique, which eliminates the necessity of using solvents . The most widely used technique of sampling with solid phase micro extraction consists of exposing a small amount of extracting phase(coating ) associated with a fiber to the sample, for a predetermined amount of time. Essentially, SPME consists of two discrete steps: solute absorption from the sample matrix into a thick layer of silicone or related adsorptive material, followed by transfer of the absorbed analytes into a chromatography inlet system by thermal or liquid desorption.

4. Solid-phase micro extraction (SPME) is an adaptation of SPE in which the solid-phase column has been replaced by a microliter syringe-like device with a hollow needle and a plunger to which is attached a fused silica fiber coated with a suitable stationary phase polymer . Various SPME fibers and coatings are commercially available and can be used to target different analytes . SPME has been applied to both GC and liquid chromatography (LC) separations .

5. D iscovery Solid Phase Micro extraction was invented in 1990 by Dr. Janusz Pawliszyn and his colleagues from the University of Waterloo in Canada . He invented this technique to “address the need for a fast, solvent-free, and field compatible sample preparation method”, which faster and more efficient is the name of the game in industry .

6. What is SPME? A solvent less sample preparation method, invented in 1990, that uses a fused silica fiber which is coated with stationary phase. It is used for sample cleaning before using other analytical methods. It consists of coated fibers that are used to isolate and concentrate analytes into a range of coating materials. After extraction, the fiber is withdrawn back into the needle and directly transferred to the GC injector port, where the analyte is thermally desorbed and introduced into the GC column for separation . This syringe-like device also protects your fiber during storage .

7. Instrument of SPME Modified syringe-like instrument . A typical SPME fiber is made of fused silica coated with a thin layer (7 μm to 100 μm thick) of immobilized polymer or a solid adsorbent, or a combination. The fused silica fiber, having a small size and cylindrical shape, is connected to stainless-steel tubing that is used to provide additional mechanical strength to the fiber assembly for repeated sampling. This stainless-steel tubing is connected to a specially designed syringe-like instrument. A small volume of extraction phase (usually less than 1 μL ) coated on fused silica support is mounted in a modified syringe .

8. The key feature of this device is an extraction fiber protected inside the needle of Syringe. Movement of the plunger allows exposure of the fiber during extraction and desorption and its protection in the needle during storage and penetration of the septum .

9. How does SPME works? First, you draw the fiber into the needle. The needle is then passed through the septum that seals the vial. You then depress the plunger to expose the fiber to your sample . Organic analytes are then adsorbed to the coating on the fiber. After adsorption equilibrium is attained, which can be anywhere from 2 minutes to 1.5 hours, the fiber is drawn back into the needle and is withdrawn from the sample vial. Finally, the needle is introduced into the GC injector or SPME/HPLC interface, where adsorbed analytes are thermally desorbed and delivered to the instruments column.

10. The procedure for collecting the sample is shown in the top row of this figure . Similar to a syringe, a SPME fiber has a 1 cm length of fused silica attached to a stainless steel plunger. The tip is coated with a polymer and is shielded inside a hollow needle. When the plunger is depressed, the fiber extends, the polymer is exposed, and the sample is collected onto it by absorption or adsorption, depending on the type of coating. After a suitable exposure time, the fiber is retracted. The bottom row of figure 1 illustrates the process for transferring the sample for analysis. The fiber is inserted into the GC-MS, and the plunger is depressed to expose the polymer. The heated injector port drives off the collected compounds, which then flow into the instrument for qualitative or quantitative analysis. Since the fiber has been “cleaned” by heating in the injector, it is ready to be reused .

11. Reaching equilibrium The extraction is considered to be complete when it reaches equilibrium and the conditions can be described by the following equation : This equation shows the relationship between the analyte concentration in the sample and the amount extracted by the coated fiber.

12. Advantage of SPME One of the principal advantages of SPME is its simplicity . In many cases, the detection limits with SPME are also lower than with other methods . Absence of solvent makes SPME environmentally friendly separation is faster throughput increases and allows for use of simpler instruments All extracted analytes are transferred to the analytical instrument Can sample directly into a sample or the headspace above sample. During desorbtion of the analyte , the polymeric phase is cleaned and ready for reuse.

13. Disadvantage of SPME Can get relatively expensive if one is not careful with fibers due to the cost being roughly $108 per fiber. Polymer coating is fragile, easily broken, and have limited life time Its main limitation is its reduced concentration capability due to the small volume of polymer coating on the fiber, which is being addressed and researched further by Dr. Pawliszyn .

14. Factors affecting SPME Fiber coating Selection Micro extraction temperature Micro extraction time Desorption temperature and time Sample agitation Salting out effect

15. Applications of SPME Application of solid-phase micro extraction to the recovery of explosives and ignitable liquid residues from forensic specimens. Application of solid phase micro extraction in food analysis is very important. To effectively use SPME to study the variety of plasticizers and other additives in lamination films. Sample preparation in biomedical analysis is mainly performed by liquid–liquid extraction and solid-phase micro extraction. SPME has very applications in Flavor analysis.