solid-phase microextraction

[subhrakanti]

Hi
Please suggest me which SPME cartidge will be best suitable for Pyridines and what condition should I use? If possible please give some literature reference.

subhrakanti

[zokitano]

Dear Subhrakanti

For your aim I suppose that the most suitable SPME coatings will be either PA (polyacrylate) or less polar PDMS/DVB (polydimethylsiloxane/divinylbenzene). The choice of the SPME fiber coating chemitry is mainly dictated by the chemistry and polarity of your target analytes. I suppose you're trying to analyze pyridine analogs (pyridine ring containing compounds).

Do you roughly know the compounds molecular weights?
What is the matrix of the sample that contains your analytes?
Are you planning to couple SPME with GC or HPLC?
At what concentrations would you like to analyze those compounds?

One interesting article from the google search:

Residual solvents determination in pharmaceutical products by GC-HS and GC-MS–SPME
Costin C. Camarasu, Mária Mezei-Szuts, Gábor Bertók Varga
Journal of Pharmaceutical and Biomedical Analysis
Volume 18, Issues 4-5, 1 December 1998, Pages 623-638

Best regards

[subhrakanti]

Thank you Zokitano for your suggestion.
The compounds are pyridine analogues and MW is 80-150. The matrix is environmental waste water and SPME will be coupled with HPLC. Concentration will be ppb to ppm levels.

Further suggestions will be highly appreciated.

[zokitano]

One of the manufacturers of SPME fibers and SPME accessories is Supelco (I don't work for them )

At the following link you can find a variety of published material for SPME and its applications (on Supelco's site):

http://www.sigmaaldrich.com/analytical- ... ction.html

For general introduction of SPME, its applications, method development and quantitation you could read in some of the published books by Janusz Pawliszyn (the inventor of SPME)

What helped me a lot when I started with SPME were some "available" web-published literature from the manufacturers. For example:

Choosing appropriate SPME fiber: http://www.sigmaaldrich.com/etc/mediali ... p/6727.pdf

Interfacing SPME with HPLC: http://www.sigmaaldrich.com/etc/mediali ... p/4760.pdf and

http://www.sigmaaldrich.com/etc/mediali ... p/4642.pdf

SPME theory and optimization of conditions: http://www.sigmaaldrich.com/etc/mediali ... p/4547.pdf

References for SPME applications: http://www.sigmaaldrich.com/etc/mediali ... p/8652.pdf

So generally you can find useful information on SPME on the web.

Regarding your present application, you have to think about obtaining:

1. Suitable SPME fiber (PDMS/DVB or PA for less polar and mid polar analytes, Carbowax-CW for very polar analytes; if your pyridine analogs are fairly nonpolar, then PDMS 100 or 30um is suitable choice for you). Remember when purchasing SPME fibers, ask for SPME fiber that are suitable for SPME-HPLC interface. Note that you'll have to choose suitable solvent for desorption of your analytes from the fiber. And for these questions consult the (information from the) manufacturer about the solvents suitable for SPME fiber desorption. Some solvents could cause swelling of the polymer fiber coating and shorten its lifetime.

2. Choose suitable extraction conditions: vial size, septa type (i prefer Teflon-PTFE coated silicone septa), agitation and temperature of sample, pH and ionic strength (salting out effect) of the sample

3. You'll have to choose whether you'll use special SPME desorption chamber connected with your LC injector or you'll desorb your fibers in to a clean vials filled with the desorption solvent. The SPME desorption chamber is better solution for better reproducibility and minimal loss of analytes

Just for information, isn't is more suitable to do SPME-GC analysis of your analytes? Are they (semi)volatile? Do they decompose with increasing of the temperature?

Hope this helps

[zokitano]

Found some interesting articles for your questions:

Trace analysis of hetero aromatic compounds (NSO) in water and polluted groundwater by solid phase micro-extraction (SPME)
JOHANSEN S. S.; PAWLISZYN J.
Journal of high resolution chromatography, 1996, vol. 19, no11, pp. 627-632

A study of the behavior of polar and nonpolar solid-phase microextraction fibers for the extraction of Maillard reaction products
COLEMAN W. M.
Journal of chromatographic science, 1997, vol. 35, no6, pp. 245-258

You can find in the articles comparison of extraction efficiency of different fiber coatings for NSO (like PDMS, PA and CW), among which PA gave the highest efficiency.
When developing SPME of pyridines from water samples, you should consider direct immersion SPME and adjusting the pH of the sample matrix between 7-10, to boost the extraction of the basic pyridines.
But you must also know that putting the SPME fiber into the waste water sample you'll also get other highmolecular matrix compounds on the fiber, which may cause subsequent deterioration of the fiber's extraction efficiency.
Also precautions should be made when adjusting the pH of the sample at low or high values. During direct immersion (DI) SPME, acidic or basic samples can quickly destroy the fiber coating and make the fiber useless. So stay away from low or high pH values when planning to do DI-SPME.

Regards