Chris Peery

12/2/14

Chem 230

SPME-HPLC Homework Answers

1. What SPME technique adsorbs analytes from the air? From water?

Headspace SPME. Direct immersion SPME.

2. Name three advantages and one disadvantage SPME has compared to other HPLC techniques.

Possible advantages: setup simplicity, low cost, ease of use, fast preconcentration step, fast extraction, requires little sample, requires little solvent, hyphenation with HPLC, portability, semi-volatile/nonvolatile organic compound analysis.

Possible disadvantages: Fibers unstable/undurable with strong organic solvents, careful control of plunger movement required, possible loss of analyte in field sampling. [instructor’s comment: requires special injection valve]

3. If the coating on an SPME microfiber is 7 µm and it takes 5 minutes for an analyte to desorb, what is the diffusion coefficient of the analyte (in µm²/min)?

time = L²/2D or D = L²/2(time) = 4.9 µm²/min

4. Name one difficulty inherent in the analysis of pesticides and how the SPME technique addresses this issue.

Possible answers:

Pesticides need to be analyzed at low concentrations; SPME can analyze at these concentrations.

Standards need to have levels of analyte comparable to real samples; SPME is portable and can be done on-site.

Sample preparation for analysis should not add to environmental pollution; SPME is a relatively “green” technology, requiring way less sample to analyze.

Traditional techniques are time and solvent-consuming. SPME is fast and required either no or little solvent.