Solid phase sampling device and methods for point-source sampling of polar organic analytes
Sampling devices for sampling an aqueous source (e.g., field testing of ground water) for multiple different analytes are described. Devices include a solid phase extraction component for retention of a wide variety of targeted analytes. Devices include analyte derivatization capability for improved extraction of targeted analytes. Thus, a single device can be utilized to examine a sample source for a wide variety of analytes. Devices also include an isotope dilution capability that can prevent error introduction to the sample analysis and can correct for sample loss and degradation from the point of sampling until analysis as well as correction for incomplete or poor derivatization reactions. The devices can be field-deployable and rechargeable.
1. A method for analyzing an aqueous sample comprising:
introducing the aqueous sample into a sampling device, the aqueous sample contacting a first layer in the sampling device, the first layer comprising a first solid phase extraction medium and a first derivatizing agent for a first targeted analyte of the aqueous sample, reaction between the first derivatizing agent and the first targeted analyte forming a first derivatized analyte, the first derivatized analyte being less polar than the first targeted analyte, the aqueous sample subsequently contacting a second layer in the sampling device, the second layer comprising a second solid phase extraction medium and an isotopically labeled analogue of the first derivatized analyte;
allowing a first portion of the aqueous sample to exit the sampling device, a second portion of the aqueous sample being retained on the first solid phase extraction medium and the second solid phase extraction medium;
following a period of time, eluting the second portion of the aqueous sample from the sampling device; and
analyzing an eluent thus obtained to determine a concentration of the first targeted analyte in the aqueous sample.
2. The method of claim 1 , the first layer further comprising a second derivatizing agent for a second targeted analyte of the aqueous sample, reaction between the second derivatizing agent and the second targeted analyte forming a second derivatized analyte, the second derivatized analyte being less polar than the second targeted analyte, the second layer further comprising an isotopically labeled analogue of the second derivatized analyte, the method further comprising analyzing the eluent to determine a concentration of the second targeted analyte in the aqueous sample.
3. The method of claim 1 , the second layer further comprising an isotopically labeled analogue of a third targeted analyte, the method further comprising analyzing the eluent to determine a concentration of the third targeted analyte in the aqueous sample.
4. The method of claim 1 , further comprising removing the first and second layers from the sampling device and replacing the first and second layers with a replacement first layer and a replacement second layer.
5. The method of claim 1 , further comprising drying the second portion of the aqueous sample.
6. The method of claim 1 , wherein the aqueous sample is obtained from a natural source, the method further comprising returning the first portion of the aqueous sample to the natural source.
7. The method of claim 6 , wherein the aqueous sample is introduced into the sampling device at the natural source.
8. The method of claim 1 , wherein the first solid phase extraction medium and/or the second solid phase extraction medium comprises a carbon-based medium.
9. The method of claim 1 , wherein the reaction between the first derivatizing agent and the first targeted analyte silylizes, acylates, or alkylates the first targeted analyte.
10. The method of claim 1 , wherein the isotopically labeled analogue of the first derivatized analyte is a carbon-13 labeled analogue.