Determination of organophosphorous pesticides in municipal and industrial wastewater using Atlantic® C18 disks for EPA method 1657

Scope

This application note will outline optimized methods for the extraction of organophosphorus pesticides as outlined in EPA method 1657 using the Atlantic® C18 SPE disk processed using Biotage automated or manual SPE solutions, and the DryVap® Concentrator System. The first section will highlight the use of the Biotage® Horizon 5000 fully automated extraction system and the method used for this application. Additionally, there will be an Application Modification section that will highlight the use of the Biotage® VacMaster™ Disk vacuum manifold for this application.

Introduction

US EPA Method 1657 describes the procedure to determine low ppb levels of organophosphorus pesticides in municipal and industrial wastewater. This method is a consolidation of several EPA wastewater methods that are used to determine organophosphorus pesticides associated with the Clean Water Act, the Resource Conservation and Recovery Act, and the Comprehensive Environmental Response, Compensation, and Liability Act; and other compounds amenable to extraction and analysis by wide–bore capillary cartridge gas chromatography with a flame photometric detector (FPD).

Automated SPE for the analysis of organophosphorous pesticides by EPA Method 1657 uses the Atlantic® C18 solid phase extraction disk. Acetone, methanol and ultra-pure water are used to condition the Atlantic® C18 disk prior to the extraction step. The extraction solvents are acetone and hexane. Extracts are then analysed by GC/FPD using a splitless injection technique.

The Biotage® Horizon 5000 provides automatic extraction of liquid samples by solid phase extraction methods, and can handle samples from ranging from 20 mL to 4 L. The DryVap® Concentrator System provides automatic sample drying with a patented membrane technology and automatically concentrates each dried extract by applying heat, vacuum, and sparge flow for up to six samples at once.

Instrumentation

• Biotage Instruments
  »  Biotage® Horizon 5000 Automated Extraction System
  » DryVap® Concentrator System
  » DryDisk® Separation Membranes
  » Atlantic® C18 Disks (47 mm)
• Agilent 6890 GC with dual FPDs
• J&W Cartridges
  »  Cartridge A: DB-1701, 30 m x 0.320 mm x 0.25 um
  »  Cartridge B: DB-5ms, 30 m x 0.250 mm x 0.5 um
• Merlin MicroSeal High Pressure Septum
  
  

Method summary

1. Obtain 100 mL aliquot samples and confirm pH is between 5–10

2. Spike the surrogate compounds into samples.

3. Spike the analyte standards into any laboratory control or matrix spike samples.

4. Place the sample bottle on the Biotage® Horizon 5000 Extraction System and place the Atlantic® C18 disk in the standard 47mm disk holder.

5. Start the extraction method from table 1 and collect extract (approx. 20 mL).

6. Add the extract to the DryDisk® holder and start the concentration process on the DryVap® using the settings in table 2.

7. Concentrate the extract to less than 1.0 mL and quantitatively bring the extract volume to 1.0 mL.

8. Transfer a portion of the extract to a GC vial.

9. Analyze by GC/FPD.

Acknowledgements

Biotage would like to thank Dr. Johnny Skelton, PhD, from the City of Fort Worth, Water Department, Centralized Laboratory Services for his help with developing this method.

Application modifications

Biotage® VacMaster™ Disk method summary

1. Repeat the following steps for each active Biotage® VacMaster™ Disk station.

2. Setup the VacMaster™ Disk manifolds ensuring all waste lines and vacuum lines are attached. Set the vacuum pump to -24”Hg.

3. Prepare the disk holder assembly (47 mm): ensure the support screen is flat in the centre of the disk holder. Place the Atlantic® C18 Disk on top of the support screen with the ripples of the disk on top and add any prefilters on top of the disk. Place the disk holder assembly on the VacMaster™ Disk manifold ensuring there is a tight seal with the luer fitting.

4. If using the multifunnel, place onto the disk holder assembly. If not using the multifunnel, omit those directions throughout the method.

5. Condition the SPE Disk:
                   a. Guide for each conditioning step in the table below:
I. Measure the appropriate VOLUME of SOLVENT into a graduated cylinder and pour into the disk holder assembly.
II. Using a Nalgene Wash Bottle (phthalate free), rinse the multifunnel and disk holder in a circle for about 3 seconds using the same SOLVENT (approximately 5 additional mL).
III. SATURATE the disk for the indicated time (in SECONDS). (Saturate means: quickly turn the knob to the appropriate waste destination and back to the “OFF” position. This brings the solvent into the disk media bed).
IV. SOAK the disk for the indicated time (in SECONDS).
V. DRAIN to the appropriate waste destination for the indicated time (in SECONDS). Switch to the “OFF” position.

6. Load the Sample:
a. For multifunnel: quickly and efficiently angle the bottle to rest on the                         multifunnel upside-down.
b. For no multifunnel: pour a portion of the sample into the disk holder.
c. Adjust the vacuum between -10”Hg and -15”Hg for sample load (please note, if the sample is flowing too slowly, the vacuum can be increased). Drain the sample to “AQUEOUS” waste. Continue to pour the sample into the disk holder ensuring the disk does not go dry or overflow for the duration of sample load.

7. Air Dry the SPE Disk:
a. Return the vacuum to -24”Hg and continue to air dry the SPE disk to                            “AQUEOUS” waste for an additional 360 SECONDS. Switch to the “OFF” position.
b. Remove the sample bottle from the multifunnel if it was used.

Biotage® VacMaster™ Disk Method Summary

1. Repeat the following steps for each active Biotage® VacMaster™ Disk station.

2. Setup the VacMaster™ Disk manifolds ensuring all waste lines and vacuum lines are attached. Set the vacuum pump to -24”Hg.

3. Prepare the disk holder assembly (47 mm): ensure the support screen is flat in the centre of the disk holder. Place the Atlantic® C18 Disk on top of the support screen with the ripples of the disk on top and add any prefilters on top of the disk. Place the disk holder assembly on the VacMaster™ Disk manifold ensuring there is a tight seal with the luer fitting.

4. If using the multifunnel, place onto the disk holder assembly. If not using the multifunnel, omit those directions throughout the method.

5. Condition the SPE Disk:
               c. Guide for each conditioning step in the table below:
I. Measure the appropriate VOLUME of SOLVENT into a graduated cylinder and pour into the disk holder assembly.
II. Using a Nalgene Wash Bottle (phthalate free), rinse the multifunnel and disk holder in a circle for about 3 seconds using the same SOLVENT (approximately 5 additional mL).
III. SATURATE the disk for the indicated time (in SECONDS). (Saturate means: quickly turn the knob to the appropriate waste destination and back to the

Literature number: AN021