National Survey Of Chlorinated Disinfection By-Products In Canadian Drinking Water

Appendix 2- Sampling Protocol And Analytical Methodology

Experimental

Reagents

Silica gel (chromatography grade, 100-200 mesh) was washed with diethyl ether (DEE) and dried at 110°C; sodium sulphate was heated at 400°C for 4 hours, washed with DEE and dried at 110°C and glass wool was acidified with sulphuric acid, washed with DEE and oven dried at 110°C. Diazomethane was prepared as required according to the Aldrich Diazald method. Groundwater, free of DBPs, obtained from a local well was used for blanks and the preparation of fortified standards.

Sample Collection and Extraction

During two periods, February-March 1993 and August-September 1993, replicate water samples were collected at fifty-three water treatment plants across Canada. Samples requested were raw water, treatment plant water (after final disinfection but before distribution) and treated water from a well-flushed tap at a point near the middle of the distribution system.

Water samples for the analysis of THMs, HANs, chloro-propanones, chloral hydrate and chloropicrin were collected in 62 mL amber bottles containing ammonium chloride (62 mg per bottle). The water sample was adjusted to pH 4.5 at the time of collection; the volume of acid (0.1N HCl) needed to adjust the pH was determined using a 62 mL water sample which was then discarded. The determined amount of acid was added to each sampling bottle and, using a gentle stream of water, the bottles were filled just to overflow to prevent any headspace and dilution of the added preservatives. The bottles were capped with Teflon-lined seals, returned to the laboratory in a cooler and stored in a cold room until analyzed (usually within 1-4 days). For the analyses, a 12 mL aliquot was withdrawn and discarded, 16 g NaCl was added to the remaining sample (ca 50 mL; the accurate volume of the sample bottle was determined later using a volumetric cylinder), and the solution was shaken for 3 minutes with 3 mL of methyl t-butyl ether (MTBE) containing dibromomethane (IS-1) and 1,2-dibromopropane (IS-2) (50 and 250 pg/µL respectively) as internal standards. After transfer to a precalibrated (3.0 mL) vial, any residual water was removed with a pasteur pipet and the volume adjusted to 3 mL. Sodium sulphate was then added to the extract and the MTBE solution fortified with 1,3-dibromopropane (IS-3) (15 µL of 50 ng/µL in MTBE) and analyzed by GC-ECD. Quantification was based on response factors relative to IS-2 (IS-1 was added in case there were interferences with IS-2, however this did not occur). IS-3 was used to determine the percent recovery of IS-2 (95 ± 4%). Data from the first replicate sample was evaluated before analysis of other replicates and if the chloroform concentration in the sample exceeded the ECD linear range (0.2-50 µg/L), only an aliquot of the other replicate samples was used for analysis.

For the HAAs, the sampling vials used for water collection, field blanks and fortified samples were prepared by adding sodium thiosulphate solution (100 µL of 125 µg/µL) to each vial, which was then oven dried at 110°C for 2 hours. The vials were filled just to overflow with samples, sealed with Teflon-lined caps, returned to the laboratory in a cooler and stored in a cold room until analyzed (usually within 1-4 days). For analysis of HAAs the 30 mL water sample was transferred to a 60 mL separatory funnel containing NaCl (8 g) and the recovery standard (5.0 µl of 100 ng/µL 2-bromo-n-butyric acid (MBBA) in acetone) was added. The accurate volume of the sample vial was then determined using a volumetric cylinder. The solution was made basic (pH = 11.5) by adding 1 N sodium hydroxide (100 µL or as determined on representative replicates), shaken and left to stand for 5 minutes. The sample vial was rinsed with 6 mL DEE, the rinsing transferred to the separatory funnel and the sample extracted. After phase separation (ca 5 minutes) the aqueous layer was transferred from the separatory funnel into a 50 mL disposable centrifuge tube. The organic phase was discarded and, after washing the separatory funnel with a small amount of DEE (also discarded), the aqueous phase was returned to the separatory funnel. The solution was acidified to pH 0.5 by adding sulphuric acid (1.2 mL, 1:1) and left to stand for 5 minutes. The 50 mL tube was washed with 6 mL of DEE which was transferred to the separatory funnel and used to extract the aqueous solution. This process was repeated with a second 6 mL of DEE; the separatory funnel was washed with 2 mL DEE after each extraction and the combined DEE extracts were passed through a drying tube containing 2.8 grams of sodium sulphate (washed with 20 mL DEE prior to use). The eluent was collected in disposable centrifuge tubes (15 mL; pre-calibrated at the 2 mL mark) and the volume reduced to 1.8 mL using a nitrogen gas evaporator. The GC/MS quantification standard (5.0 µL of 200 ng/µLpara bromochlorobenzene in DEE), methanol (10 µL, dried), diazomethane (60 µL) were added and the volume adjusted to 2 mL with DEE. After 30 minutes with minimal exposure to light, silica gel (50 mg) was added and the samples allowed to stand for at least 30 minutes before they were analyzed by GC/MS.

Water samples were collected for the analysis of total organic carbon (300 mL samples collected in prewashed poly-carbonate bottles containing 1 mL of 10% ^H2^SO4^{) and total} organic halogen (500 mL samples collected in prewashed amber glass bottles containing sodium thiosulfate). Water samples (60 mL in prewashed polypropylene bottles) were collected for the determination of bromide ion.

Gas chromatography

GC/ECD analysis was conducted using a Varian Vista 6000 GC with an on-column injector and a J&W DB-5 30 m × 0.32 mm id (1 µ film) column. The GC was interfaced to a Vista 402 chromatography data system. The operating parameters were: oven temperature program; 50°C (3 min), 1.5°C/min to 65°C (1 min), 5°C/min to 120°C, 20°C/min to 180°C (10 min); on-column injector program: 100°C, 140°C/min to 240°C (15 min); detector 290°C. The helium carrier gas was set at 1 mL/min (ambient) with nitrogen make-up gas set at 25 mL/min.

The confirmation analyses were conducted on a DB-17 column (J&W DB-17 30 m × 0.32 mm id (0.25 µ film). The oven temperature program was: 35°C (3 min), 0.5°C/min to 40°C (1 min), 6°C/min to 100°C (1 min), 15°C/min to 160°C (1 min). All other GC/ECD settings remained unchanged.

Response factors, obtained by analyses of multi-level fortified water samples, were used to calculate DBP concentrations in the samples.

Gas chromatography - mass spectrometry

GC/MS analysis for HAAs was carried out by selected ion monitoring using a Finnigan MAT 90 GC/MS fitted with a DB-1701 30m × 0.32 mmid (0.25 µ film) column by injection of 3 µL aliquots (Varian SPI injector). The GC operating parameters were: injector - 100°C increased to 240°C at 100°/min, hold 24 min; oven - 40°C held for 3 min, increased to 140°C at 3.3°/min, then to 180°C at 23°/min. The ions monitored (mass resolution 1000) for each target HAA were: monochloroacetic acid - 49,77,79; dichloroacetic acid - 83,85; trichloroacetic acid - 117,119,121; monobromoacetic acid - 93,95; dibro-moacetic acid - 171,173,175; tribromoacetic acid - 251,253; bromochloroacetic acid - 127,129; bromodichloroacetic acid - 141,161,163; chlorodibromoacetic acid - 207,209. DBP quantification was carried out by using rela ti ve response factors derived from the analysis of fortified water samples.

Auxiliary parameters

Auxiliary chemical parameters were determined by NOVAMANN (Ontario) Inc. Bromide ion concentration was determined by chromatography using a DIONEX 2000i ion chromatograph; for the summer samples, the detection limit was improved by a 10:1 preconcentration.

Total organic carbon (TOC) was determined using a SKALAR SK 12 organic carbon analyzer. After sparging with nitrogen to remove inorganic carbon or volatile organics, the organic carbon of the sample was converted to ^CO2 ^{by UV/per-}sulfate oxidation followed by catalytic conversion ^(H2^{; Ni/} 400°C) to methane. The methane was then detected by flame ionization detector (FID) and quantified by reference to a standards calibration curve.

The total organic halogen (TOX) was determined using a Mitsubishi TOX-10 analyzer using coulometric/activated charcoal techniques. The samples were passed through TOX adsorbing activated charcoal (AC) tubes and washed with a nitrate solution to remove any adsorbed inorganic halide ions. The TOX adsorbing AC tube was then transferred to a combustion chamber where the TOX was converted ^(O2 ^{/ (800-900°C)} to halogenated hydrogen. The generated halogenated hydrogen was then titrated automatically with silver ions generated coulometrically.

Quality Control

All samples were collected at least in duplicate and control samples were included for all groups of target analytes (usually one field blank per two sites). All DBP analytical methods incorporated surrogate internal standards and quantification was based on response factors established by multi-level calibration with fortified samples analyzed under identical conditions.

For the THMs, HANs, chloropropanones, chloral hydrate and chloropicrin analyses, the response factors were initially set by triplicate analyses of DBP-free groundwater fortified at 0, 0.2, 1, 2, 5 and 10 µg/L [chloroform = 5×]. Additional fortified samples were also analyzed at scheduled intervals. A total of 12 replicates (four sets of triplicate samples spiked at each fortification levels) were analyzed during each season. The response factors were not changed if variation was less than 10%. In addition, several raw water samples (unused raw replicates from all regions) from different water sources (matrix spikes; n=14) were analyzed at a fortification level of 5 µg/L (chloroform = 25 µg/L). The overall percent recovery was 99.4% (range 87.4 - 107.2) with standard deviation of 3.5. The results are shown in Table 7.

The accuracies of the analytical methods were estimated (TTHMs ± 5%, HAAs ± 20%) from the periodic analysis, throughout the study, of water samples fortified with known levels of target analytes. The mean recovery of HAAs was typically 96% as estimated from the recovery of the added MBBA internal standard.

Samples with a chloroform concentration exceeding the ECD linear range (0.2-50 µg/L) were reanalyzed using an aliquot from a replicate sample. DBPs identified by GC-ECD were confirmed by GC-MS or by GC-ECD analysis on a second GC column (DB-17). Each week during the analytical period, duplicate 30 mL groundwater samples were spiked with a HAA standard mixture of known concentration (6 µL of 80 ng/µL), stored in a refrigerator until the following week and analyzed as described above.

Table 7 - Recoveries (%) from fortified raw water (n=14)

Compounds	Spking Level (µg/L)	RT	RF	Mean % Recovery	SD
Chloroform	25	5.80	0.73	98.4	3.1
Bromodichloromethane	5	8.97	4.82	99.9	1.8
Chlorodibromomethane	5	14.20	4.16	100.1	1.8
Bromoform	5	19.77	1.53	92.3	2.3
Trichloroacetonitrile	5	7.71	8.63	104.7	3.1
Dichloroacetonitrile	5	9.13	4.74	96.5	1.9
Bromochloroacetonitrile	5	15.05	3.88	102.7	1.7
Dibromoacetonitrile	5	20.83	3.10	107.0	2.3
1,1-dichloro-2-propanone	5	10.24	2.78	92.3	1.9
1,1,1-trichloro-2-propanone	5	17.27	4.09	107.2	1.9
Chloral Hydrate	5	9.30	4.88	104.5	4.1
Chloropicrin	5	13.20	9.20	87.4	16.4

• RT - retention time in minutes
• RF - response factor based on IS-2
• SD - standard deviation