Experiment VII

Analysis of Fragrance Compounds in Water and Soil

Purpose

To demonstrate the procedures for separation of organic contaminants from environmental matrices and to illustrate some of the steps necessary for their preparation for chromatographic analysis.

References

  1. Sawyer, C. N., McCarty, P. L., and Parkin, G.F. Chemistry for Environmental Engineering, 5th ed., McGraw Hill, 2003.
  2. Simonich, S. L.; Begley, W. M.; Debaere, G.; Eckhoff, W. S. Environ. Sci. Technol. 2000, 34, 959-965.
  3. A.M. DiFrancesco, P.C. Chiu, L.J. Standley, H.E. Allen, and D.T. Salvito. Environ. Sci. Technol. (in press).

Background

Fragrance materials (FMs) are a group of over 3,000 structurally diverse compounds that are widely used in consumer products, such as laundry detergent, soap, and shampoo. Most FMs are used at low concentrations and have global industry volumes less than 1 metric tons per year (mT/y), while a small number of FMs have production volume exceeding 3,000 mT/y. Through down-the-drain disposal of consumer products, FMs are discharged into sewage and enter municipal wastewater treatment plants (WWTPs).

In recent years, there has been growing concerns about the potential impact of organic micro-pollutants, such as pharmaceuticals and personal care products, in the environment, and WWTPs effluent is considered the primary source of input. Several FMs, particularly polycyclic and nitro musks and their metabolites, have been detected in surface waters downstream of WWTP discharge points as well as in aquatic environments and aquatic organisms. The polycyclic musks AHTN (7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydro-naphthalene) and HHCB (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-gamma-2-benzopyran) have been used as molecular tracers to track the transport of WWTP organic matter in surface waters.

The fragrance compounds that have been studied at the University of Delaware are the following:

Procedure

Spiking cocktails have been prepared by dissolving weighed amounts of a subgroup of the FMs in methanol (99.5% Aldrich). The cocktails have been stored at 5°C in borosilicate vials capped with Teflon®-lined closures and sealed with low-permeability vinyl tape (3M). FM standard solutions for gas chromatography-mass spectrometry (GC/MS) calibration were prepared by dissolving a pre-weighed amount of each chemical in methanol. The standard stock solution was then transferred to a bottle sealed with Teflon® tape and stored at -30°C. Calibration standards were made through dilution of the stock solution using methanol and were stored in a similar fashion.

Calibration Standards

  1. Calibration standards will be prepared and the calibration data will be provided. This will, for each calibration standard, consist of the concentration and instrument response for each of the compounds that it contains.
  2. You will be provided a chromatogram of a standard solution containing a number of FMs. These will be identified so that you can compare the retention time for your compound(s) to those of the standard.

Samples

Take one set of samples consisting of a FM spiking solution and 3 soil samples. Each of the 5 g air dried soil samples has been previously spiked with an equivalent of 1 mL of your FM solution. Be sure you note the letter designation of your FM on all samples you turn in for analysis.

Analysis of FM spiking solution

  1. Transfer a portionof your FM spiking solution to a 4-mL borosilicate vial for analysis by GC-MS. This is sample 1.

Extraction of water sample

  1. Place 100 mL tap water into your separatory funnel.
  2. Add 1 mL of your FM spiking solution to the water in the separatory funnel.
  3. Add 5 mL DCM.
  4. Stopper funnel and shake once.
  5. Being careful to have the stopper pressed tightly into the palm of your hand, tip the funnel so the stem is nearly vertical.
  6. Slowly open the stopcock so that the vapor inside the flask will equilibrate in pressure with that of the atmosphere.
  7. Close the stopcock.
  8. Shake 15 – 20 times to ensure good mixing of the DCM with the water and thus transfer of the FMs from the water to the DCM. Check for pressure equalization several times during this process (steps 5 – 7). This is a good place to ensure that each person gets some experience.
  9. With the separatory funnel in its conventional orientation with the stem down, remove the stopper. Allow the DCM to settle. If some water is commingled or droplets appear stuck, gentle tap.
  10. Carefully drain the DCM into a vial or test tube leaving the water in the separatory funnel.
  11. Run the DCM phase into a test tube or vial and add approximately 1 g anhydrous sodium sulfate to remove water. (If you have visible droplets of water, it may be necessary to transfer a portion of the DCM to another tube before adding the sodium sulfate.)
  12. Transfer a portion to a 4-mL vial for analysis by GC-MS. This is sample 2.

Extraction of soil sample

  1. Two of the three soil samples will be extracted with DCM in an ultrasonic shaking bath. The third sample is an extra to be used only if you have a problem. Add 10 mL DCM to each of the 3 soil samples. Place 2 of the samples into the ultrasonic shaker. Remove one after 5 min and the other after 45 min.
  2. Transfer the DCM phase into a test tube or vial and add approximately 1 g anhydrous sodium sulfate to remove water. (If you have visible droplets of water, it may be necessary to transfer a portion of the DCM to another tube before adding the sodium sulfate.)
  3. Transfer a portion to a 4-mL vial for analysis by GC-MS. These are samples 3 and 4.

Analysis

Analyze the samples for FMs using GC-MS. Data will include the retention time and response. For your sample 1, a mass spectrum will also be provided.

Data Analysis

  1. Prepare calibration curves for your FMs and plot the regression line with the best fit linear equation for the data obtained.
  2. Determine the concentration (g/L for all samples and also g/g for the soils that were extracted) of your FMs for all samples using best fit equations determined in “Data Analysis No. 1 and present in a neat, easy to read table. Be careful that you have correctly accounted for the volumes of solvent used.
  3. Compute, and include in your table, the recovery of your FMs from the water and soil samples, based on the analysis of the FM spiking solution.

Questions

  1. How would you propose that the recovery of the FMs in your sample might be improved?
  2. For your FMs show on your mass spectrum the molecular ion. What is its MW? How does that compare to the calculated MW?
  3. Extra Credit. Indicate the MW for each of the 3 most abundant peaks that are not the parent. Propose the moiety that has been lost and the formula for the resulting ion.

Apparatus

4 mL sample vials

Separatory funnel

Ultrasonic shaker

Pipettes (volumetric and Pasteur)

Gas Chromatograph-Mass Spectrometer (GC-MS)

Reagents

FM standards in methanol

Sodium sulfate

Dichloromethane