ADV01-05_1-298

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www.restekcorp.com

The US EPA recently developed GC/MS methodology

for screening finished drinking water for selected

semivolatile organic compounds not addressed by

the Safe Drinking Water Act (SDWA). These

Unregulated Contaminant Monitoring Rule (UCMR)

List 2 contaminants are part of a screening survey

established to determine whether in the future these

contaminants should be regulated by standard drink-

ing water methods. Method 526 is applicable for 11

of the 15 contaminants on List 2.* Compounds mon-

itored by Method 526 are effectively extracted from

water, using 47mm polystyrene divinylbenzene

(SDVB) solid phase sorbent, and are sufficiently

volatile and thermally stable for GC. The minimum

reporting level (MRL) concentration for UCMR List

2 is 0.5µg/L—the value of the lowest concentrations

at which precision and accuracy determinations

were made during method development.

After careful review of the method we have pre-

pared a new Restek calibration standard, as recom-

mended in Method 526, that includes all 11 semi-

volatile organic compounds at 200µg/mL each in

ethyl acetate. We also developed internal and surro-

gate standards, and we offer a GC/MS tuning solu-

tion at a convenient 2500µg/mL concentration in

methylene chloride (SV Tuning Compound, cat.#

31001; see page 7 of this newsletter). This set of

Restek reference materials will meet all chemical

standards needs for Method 526.

The majority of the target compounds analyzed

through EPA Method 526 are pesticides. Low-level

injections reduce sensitivity for many of these com-

pounds, due to degradation or irreversible adsorp-

tion in the injection port. Cyanazine, 2,4,6-

trichlorophenol, and prometon, for example, are

susceptible to adsorption or thermal degradation in

the GC inlet. To circumvent inlet problems, we use

a deactivated, Drilled Uniliner

liner in the inlet, to

significantly reduce sample exposure to the hot

metal surfaces of the injection port.**

In addition, when analyzing pesticides there are

demands on the capillary GC column for higher

inertness and lower GC/MS bleed: active sites in the

inlet liner or column can cause complete loss of

prometon and excessive tailing of 2,4-dichlorophe-

nol and 2,4,6-trichlorophenol peaks. Our silarylene

polymer-based Rtx

-5Sil MS column provides opti-

mal separation of the new reference materials and

exhibits very low column bleed, compared to tradi-

tional phenyl/methyl phases. The 30m, 0.25mm ID,

0.25µm column (cat.# 12723) used to obtain Figure

1 is an optimal combination of internal diameter

and film thickness, making it the choice for analyz-

ing many semivolatile compounds. It also is an

excellent choice for EPA Method 8270. The thin

phase film reduces analysis time, and high tempera-

ture stability (330/350ºC) enables an analyst to use

a rapid temperature program during the analysis,

and to bake high boiling contaminants out of the

column after each analysis, without significant

bleed.

We highly recommend these new reference materi-

als, a Drilled Uniliner

inlet liner, and an Rtx

-5Sil

MS column to anyone conducting analyses accord-

ing to Method 526.

See product listing on the next page.

by Katia May, Ph.D., R&D Chemist, and Christopher English, Environmental Innovations Chemist

GC/MS Screening of Semivolatile

Organic Compounds in Drinking Water

Using New Restek Reference Materials and a

Capillary Column with Optimized Dimensions

✔

Full complement of new reference materials for EPA Method 526: calibration standard,

internal standard, surrogate standard.

✔

Rtx

-5Sil MS column offers low GC/MS bleed and excellent inertness.

✔

Styrene/divinylbenzene extraction disks for sample preparation.

Figure 1

An inert, low-bleed Rtx

-5Sil MS column is an effective analytical tool for unregulated drinking water contaminants.

*For information about UCMR limits, see

http://www.epa.gov/safewater/methods/unregtbl.html

**For more information about Drilled Uniliner

inlet liners, see page 13.

8 7

GC_EV00656

Rtx

-5Sil MS, 30m, 0.25mm ID, 0.25µm (cat# 12723)

US EPA Method 526 analytes, 1µL, 10ppm (20ppm IS)

Semivolatile Calibration Mix, EPA 526

cat.# 31691

Surrogate Standard Mix, EPA 526

cat.# 31693

Internal Standard Mix, EPA 526

cat.# 31692

Inj.:

1.0µL splitless (hold 0.3 min.), 4mm Drilled

Uniliner

(cat.# 21055)

GC:

Agilent 6890

Inj. temp.:

300°C

Carrier gas:

helium, constant flow

Flow rate:

0.8 mL/min.

Oven temp.:

50°C (hold 1 min.) to 200°C @ 20°C/min.

(hold 5 min.) to 310°C @ 30°C/min.

(hold 3 min.)

Det:

Agilent 5973 GC/MS

Transfer line temp.:

280°C

Scan range:

35-550 amu

Solvent delay:

5.5 min.

Tune:

DFTPP

Ionization:

1. nitrobenzene

2. 2,4-dichlorophenol

3. 1,3-dimethyl-2-nitrobenzene (ss)

4. 2,4,6-trichlorophenol

5. acenaphthene-d10 (IS#1)

6. 1,2-diphenylhydrazine

†

7. prometon

8. terbufos

9. diazinon

10. fonofos

11. phenanthrene-d10 (IS#2)

12. disulfoton

13. acetochlor

14. cyanazine

15. triphenylphosphate (ss)

16. chrysene-d12

†

Mix component 1,2-diphenylhydrazine is oxidized to

azobenzene, the analyte in the figure, on injection onto

the heated column.