SOLID –PHASE EXTRACTION TECHNIQUE FOR THE PRECONCENTRATION OF HEAVY METAL IONS (COPPER AND LEAD)
Solid–phase extraction (SPE) is an extraction method that uses a solid phase and a liquid phase to isolate one, or is type of analyte from a solution. It is usually used to clean up a sample before using a chromatographic or other analytical method to quantify the amount of analyst in the sample. The general procedure is to load a solution onto the SPE phase, wash away undesired components and then wash off the desired analyst with another solvent into a collection tube. Solid phase extraction, use the same type of stationary phases used in liquid –chromatography columns. The stationary phase is contained in a glass or plastic column above a frit or glass wool. Solid phase extraction are used not only to extract traces of organic compound from environmental sample but also to remove interfering components of the complex matrices in order to obtain a clear extract containing the analyte of interest. Solid –phase extraction has replaced other sample preparation technique such as precipitation, co-precipitation, solvent extraction because of its simplicity, low cost, rapidity, ease of automation and instrumentation. The preconcentretion of metal ion such as Cu2+ and pb2+ has been discussed in the work. TABLE OF CONTENT
Tithe page i
Table of content iii
1.0 Introduction 1
2.0 The mechanism, and procedure for solid phase Extraction 6
2.1 The mechanism of solid phase Extraction 6
2.1.1 Sorbent used in solid phase Extraction 12
2.2 Procedure for solid phase extraction 14
3.0 Preconcentration of metal ions and applications of solid phase extraction 18
3.1 Preconcentration of metal ions using solid phase extraction Technique. 18
3.2 Application of solid phase extraction 20
4.0 Conclusion and recommendation 21 4.1 Conclusion 21
4.2 Recommendation 22
Solid phase extraction (SPE) is a sample preparation process by which compounds that are dissolved or suspended in a liquid mixture are separated from other compounds in the mixture according to their physical and chemical properties. Analytical laboratories use solid phase extraction to concentrate and purify samples for analysis.
Solid phase extraction can be used to isolate analytes of Interest from wide variety of matrices, including urine, blood, water, beverage, solid and animal tissue (Hennion, 1999).
Solid phase extraction process used the affinity of solute dissolved or suspended in a liquid (known as the mobile phase) for a solid through which the sample is passed (known as the stationary phase) to separate a mixture into desired and undesired analytes of interest or undesired impurities in the sample are retained on the stationary phase. The portion that passes through the stationary phase is collected or discarded, depending on whether it contains the desired analytes or undesired impurities, in an additional step, in which the stationary phase is rinsed with an appropriate eluent, (Biziuk, 2001). A typical solid phase extraction involves five basic steps. First the cartridge is equilibrated with the non –polar or slightly polar solvent, which wet the surface and penetrates the bonded phase. Then water or buffer of the same composition as the sample is typically washed through the column to wet the silica surface. The sample is then added to the cartridge. As the sample passes through the stationary phase, the polar analyte in the sample will interact and retain on the polar sorbent while the solvent and other non-polar importees passes through the cartridge. After the sample is loaded, the cartridge is washed with a polar solvent to remove further impurities. Then the analyte is eluted with a polar solvent or a buffer of the appropriate PH (Rawa, and Wolska 2003).
Solid phase extraction is the very popular technique currently available for rapid and selective sample preparation.
The versatility of solid phase extraction (SPE) allows use of this technique for many purposes, such as purification of sample, trace enrichment, desalting, derivatsation and class fractionation of sample (Fritz, 1999).
The last few years have been characterized by a wide interest in this technique and many publications describing SPE methods have been published (Sabik et al., 2000). This period is connected with the intensive development of research procedure for novel types of sorptive materials and lasted from the base 1960s until the beginning of the 1980s.
The introduction of a wide spectrum of sorptive material into analytical procedures gave a new stimulus for the development of SPE methodology (Font et al., 1993). The principles of SPE are similar to that of liquid –liquid extraction (LLE), involving a partitioning of solute between two phases as in LLE, SPE involves partitioning between a liquid (Sample matrix or solvent with analytes) and a solid (Sorbent) phase. This sample treatment technique enables the concentration and purification of analyte from solution by sorption on a solid sorbent and action. The general procedure is to load a solution on the solid phase extraction (SPE) solid phase, wash away undesirable component, and then wash off the desires analytes with another solvent into a collection tube (Camel, 2003).