Determination of Haloacetic Acids and Dalapon in Drinking Water by Solid-Phase Extraction and GC-ECD Detection

Method 552.1 is a GC method for determination of haloacetic acid and Dalapon in drinking, ground, raw, and other waters at any stage of treatment. This application uses a silica-based quaternary amine anion exchange cartridge, with exceptional recoveries.

Figure 1: Analyte Recoveries

Materials and Instruments

1) Cartridge Conditioning

a) Assemble a glass block vacuum manifold system

b) Place CLEAN-THRU® tips CLTT050 and SPE cartridges EUQAX156 (500 mg quaternary amine) in the bulkhead fittings of the vacuum manifold

c) Attach adapters and reservoirs to the cartridge(s)

d) Add a 10 mL aliquot of MeOH to the cartridge(s)

e) Draw through at 2 mL/min

f) Add 10 mL of reagent water then slowly draw through

Do not allow the sorbent to dry prior to the addition of sample

2) Sample Extraction

a) Check pH of the preserved sample with a pH meter to be 5 ± 0.5

b) Add 250 µL of the surrogate primary dilution standard to water sample

c) Add 100 mL sample to the cartridge while drawing through under vacuum at 2 mL/min

d) After sample extraction, dry the cartridge by drawing through 10 mL of MeOH

3) Cartridge Elution

a) Dissemble the vacuum manifold and insert screw cap culture tubes

b) Add 2 mL of 10% H₂SO₄/MeOH to the cartridges

c) Elute at a rate of 1.5 mL/min (slow drip)

d) Repeat with a second aliquot of 2 mL of 10% H₂SO₄/MeOH

4) Derivatization and Solvent Partition

a) To each of the extracts from 3) d) add 2.5 mL of MTBE.

b) Agitate in a vortex mixer for 5 s

c) Place the culture tubes in a heating block at 50 °C for 1 h

d) Remove and cool down the culture tubes, transfer the extract to a large vial and add 10 mL of 10% solution of Na₂SO₄

e) Agitate for 10 s on a vortex mixer

f) Allow the phases to separate for 5 min

g) Transfer the upper MTBE layer to a 5 mL graduated conical centrifuge tube

h) Add another 1 mL portion of MTBE

i) Agitate, allow to settle, then transfer with a Pasteur pipette to the MTBE collected in step g

j) Add 200 µL IS to each extract then additional MTBE to bring final volume to 5 mL

k) Transfer a portion of the extract to GC vials

l) Sample is ready for analysis by GC–ECD

GC–ECD Conditions

Agilent 6890N coupled with ECD, equipped with 7683 auto sampler and Chemstation software GC capillary column: Restek Rtx® -1701, 30 m × 0.25 mm × 0.25 µm Injector: 2 µL splitless inj. @ 200 °C, split delay 0.5 min. Inj. 2 µL Liner: 4 mm splitless gooseneck, 4 mm ID × 6.5 mm OD × 78.5 mm (UCT GCLGN4MM).

Conclusion

High recoveries of haloacetic acids and Dalapon can be achieved using the UCT EUQAX156 silica-based anion exchange cartridge.