Steroid Extraction

Experiment #4: Solid Phase Extraction Gas Chromatography

Steroid Extraction from Water

Introduction

Through the use of solid phase extraction (SPE) and quantitative analysis, the concentration of progesterone in a synthetic wastewater sample will be determined. Progesterone is a steroid hormone that is naturally produced in humans. It enters the environment through human excretion and this is where problems may arise. In past research, progesterone has exhibited harmful effects on aquatic organisms, so being able to quantify the concentration in a sample will allow for a better understanding of the steroid's toxicity levels. In the SPE method being used, the analytes are retained in the sorbent bed and the matrix is washed away. The sorbent bed is hydrophobic and made of octadecylsiloxane, which is preferred for the extraction of hydrophobic steroids. Once the sample has made its way through the sorbent bed the analytes can be collected by using various washing solutions and eluting the solution. Solid phase extraction is an extremely useful sample preparation technique because it limits many problems that arise from the use of liquid-liquid extraction. It does not require large amounts of solvent, involves less use of expensive glassware, have better quantitative recoveries and are easy to perform. Higher percent recoveries can be directly correlated with accuracy, which is extremely important in analytical experimentation. The more accurate the method is--the more significant the results are. The use of an internal standard is also employed. It can help counteract random and systematic errors. After the extraction the internal standard--testosterone--is added to the sample tube and allows for a better determination for the recovery of the analyte. Testosterone is used because it exhibits similar properties to progesterone, in that any loss of progesterone in the solution would result in a comparable loss in testosterone. Once the sample is extracted it is ready for gas chromatography.

The samples will be chemically analyzed using a gas chromatograph. When injected into the chromatograph the constituents of the sample will pass through a gas stream at varying rates--this if often referred to as the mobile phase. Once through the mobile phase the constituents will enter the stationary phase--where the constituents are separated. After this phase is completed the chemicals are analyzed electronically and computer print outs can be obtained. In chromatography separation, it is crucial to separate the components in a short amount of time without causing any variance in the chromatographic resolution. This can also be referred to the optimization of the separation.

Methods & Observations

Data & Elaboration

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