New ISO Standard 17943 for Determination of VOCs in Water by HS-SPME and GC-MS

Introduction

Contamination of water resources by Volatile Organic Compounds (VOCs) is a concern to humanhealth as many of these compounds are toxic and are known or suspected to be carcinogenic. Consequently VOCs have to be monitored according to regulative laws on water pollution such as European Council Directive 98/83/EC or the Safe Drinking Water Act (SDWA) in the US. Existing official methods for VOC determination in water are either not state-of-the-art any more (ISO 10301: Liquid-Liquid extraction, GC/FID or GC/ECD), lacking sensitivity and selectivity (ISO 11423: Headspace-GC/FID or GC/ECD) or prone to contamination and difficult to automate (ISO 15680: Purge and Trap, GC/MS).

The new ISO Standard 17943 describes an improved and fully automated method for the determination of more than 60 VOCs in different water matrices. After extraction of the compounds from the headspace of the samples by SPME the analysis is conducted by GC-MS. The ISO 17943 describes the scope and principle, the reagents and apparatus, the sampling, sample pretreatment and analytical procedure, the calibration as well as the calculation and expression of the results in detail. This is complemented by a section on practical tips for using SPME and GC/MS.

 

Experimental

The Supelco Application Lab participated at an interlaboratory trial that was set up to validate the method. In this trial the method was applied on different real samples such as surface water and waste water. The following conditions for SPME have been used in the Supelco lab: (Table 1).

Table 1: SPME conditions for extraction of VOCs according to ISO 17943

Sample volume: 10 mL
HS-Vial: 20 mL, addition of 3 g salt
SPME fiber: DVB/CAR/PDMS, 24 gauge
Incubation time: 10 min @ 40 °C
Extraction time: 10 min @ 40 °C
Autosampler: CTC Combi PAL (agitated by circular motion of the vial, velocity: 250 rpm)
Desorption/Injector: 10 min @ 270 °C

The GC/MS analysis was conducted on a Varian CP-3800 equipped with a VOCOL column: (Table 2, Figure 1)

Table 2: GC conditions for VOCs determination according to ISO 17943

Column: VOCOL, 60m x 1,5µm x 0,25mm
Carrier gas: Helium
Flow: 1 mL/min
Injection: Splitless, SPME liner w/ 0,75 mm ID
Oven program: 35 C, 1 min; 10 C/min to 150 C; 20 C/min to 250, 20 min
Sample: 61 VOCs, 1 ppm, in water plus three internal standards
(toluene-d8, benzene-d6 and fluorobenzene) 

 

iso17943-fig-1

Figure 1: Chromatogram of an SPME extract of 61 VOCs (1 ppm) plus three internal standards (toluene-d8, benzene-d6 and fluorobenzene) in water on VOCOL Capillary GC Column. p-Xylene was left out as it is considered as an explosive precursor and was not available as reference standard at the time of the interlaboratory trial.

Results

The interlaboratory trial demonstrated that for most of the compounds the recovery rate was in the range of 80-120 % for both surface and waste water (Table 3). The reproducibility (standard deviation of all participating labs) was for most of the compounds less than 31 % (surface water) respectively less than 35 % (waste water).
 

Table 3: Results from interlaboratory trial for recovery rate and relative standard deviation in surface water

Name CAS Number Recovery Rate Relative Standard Deviation
tert-amyl methyl ether (TAME) 994–05–8 99% 17%
benzene 71–43–2 99% 20%
bromobenzene 108–86–1 106% 31%
bromochloromethane 74–97–5 95% 13%
bromodichloromethane 75–27–4 99% 15%
n ‐butylbenzene 104–51–8 86% 24%
sec‐butylbenzene 135–98–8 105% 35%
tert‐butylbenzene 98–06–6 88% 22%
chlorobenzene 108–90–7 98% 21%
2‐chlorotoluene 95–49–8 96% 23%
4‐chlorotoluene 106–43–4 95% 25%
dibromochloromethane 124–48–1 96% 20%
1,2‐dibromo‐3‐chloropropane (DBCP) 96–12–8 102% 21%
1,2‐dibromoethane 106–93–4 100% 14%
dibromomethane 74–95–3 95% 18%
1,2‐dichlorobenzene 95–50–1 97% 20%
1,3‐dichlorobenzene 541–73–1 95% 25%
1,4‐dichlorobenzene 106–46–7 98% 25%
1,1‐dichloroethane 75–34–3 93% 17%
1,2-dichloroethane 107–06–2 96% 20%
1,1-dichloroethene 75–35–4 89% 29%
cis-1,2-dichloroethene 156–59–2 89% 15%
trans-1,2-dichloroethene 156–60–5 87% 23%
dichloromethane 75–09–2 100% 49%
1,2‐dichloropropane 78–87–5 98% 15%
1,3‐dichloropropane 142–28–9 99% 18%
2,2‐dichloropropane 594–20–7 47% 52%
1,1‐dichloropropene 563–58–6 90% 22%
cis ‐1,3‐dichloropropene 10061–01–5 50% 39%
trans ‐1,3‐dichloropropene 10061–02–6 56% 33%
ethylbenzene 100–41–4 88% 23%
ethyl tert-butyl ether (ETBE) 637–92–3 122% 21%
2-ethyl-4-methyl-1,3-dioxolane 4359–46–0 101% 18%
2-ethyl-5,5-dimethyl-1,3-dioxane 768–58–1 102% 17%
geosmin 16423–19–1 106% 18%
hexachlorobutadiene 87–68–3 92% 28%
isopropylbenzene (cumene) 98–82–8 98% 27%
4‐isopropyltoluene (p‐cymene) 99–87–6 95% 35%
2-methylisoborneol 2371–42–8 103% 18%
methyl tert-butyl ether (MTBE) 1634–04–4 117% 24%
naphthalene 91–20–3 112% 25%
n‐propylbenzene 103–65–1 93% 28%
styrene 100–42–5 84% 19%
1,1,1,2‐tetrachloroethane 630–20–6 97% 16%
1,1,2,2‐tetrachloroethane 79–34–5 98% 16%
tetrachloroethene 127–18–4 99% 27%
tetrachloromethane 56–23–5 100% 24%
toluene 108–88–3 94% 30%
tribromomethane (bromoform) 75–25–2 106% 12%
1,2,3‐trichlorobenzene 87–61–6 95% 22%
1,2,4‐trichlorobenzene 120–82–1 98% 27%
1,3,5‐trichlorobenzene 108–70–3 -a  
1,1,1-trichloroethane 71–55–6 99% 20%
1,1,2‐trichloroethane 79–00–5 99% 13%
trichloroethene 79–01–6 133% 21%
trichloromethane (chloroform) 67–66–3 92% 21%
1,2,3‐trichloropropane 96–18–4 102% 18%
1,2,4‐trimethylbenzene (pseudocumene) 95–63–6 110% 27%
1,3,5‐trimethylbenzene (mesitylene) 108–67–8 99% 21%
vinyl chloride 75–01–4 88% 22%
m-xylene 108–38–3 -b  
o-xylene 95–47–6 102% 28%
p-xylene 106–42–3 122% 28%


a
1,3,5- Trichlorobenzene is considered as an explosive precursor and was left out in the interlaboratory trial.

b As m-xylene and p-xylene may coelute in GC analysis, only p-xylene was investigated within the scope of the interlaboratory trial. m-Xylene and p-xylene can be determined as sum parameter according to ISO 17943.

Summary

The new ISO Standard 17943 provides tremendous improvements compared to the existing methods for VOC determination in water. The method is very sensitive (limit of determination is for most compounds 0,01 μg/L or lower) and can be fully automated. The outstanding performance in terms of accuracy, reliability and reproducibility of this method was confirmed by a global interlaboratory trial with 42 participating labs from 16 countries.

Certified Reference Materials have been developed specifically for ISO Standard 17943. These are split into one mixture containing 57 VOCs, one mixture containing four odor compounds and two single compound solutions: Vinyl chloride (due to its high volatility) and 1,3,5-trichlorobenzene (due to compliance reasons).

Materials

     
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