GB5750.8-2023 Analysis of 27 volatile halocarbons in drinking water Headspace&GC

Abstract

27 kinds of halogenated hydrocarbons were analyzed based on the self-developed automatic headspace samplers HS-25 of Panyu and the 1949 gas chromatoscope. The linear, detection limit and standard recovery rate were all in line with the relevant requirements.The following describes in detail the establishment of the standard curve and the verification of the method.

Introduction

Drinking water is closely related to each of us. The new revised version of drinking water standard "GB 5749-2022 Hygienic Standard for drinking Water" was officially released on March 15, 2022, and the standard will be officially implemented on April 1, 2023.The inspection standard GB/T 5750, which is compatible with GB 5749 standard, is also being revised.The newly revised "GB/T 5750.8 -2023 standard test method for drinking water Part 8: Organic Indicators" includes 5 conventional indicators, 21 extended indicators and 4 appendix indicators related to VOC in GB 5749-2022 standard.

According to comparison, 27 kinds of halogenated hydrocarbons were determined by Headspace Sampler + capillary column (DB-1701) +ECD, and 11 kinds of volatile organic compounds were determined by Headspace Sampler+ capillary column (DB-WAX) +FID. The combination of these two solutions can cover the analysis of organic matter in conventional projects and most organic matter in extended projects.

In this paper, the use of Panyu headspace samplers HS-25, as well as Panna GC model 1949(configuration of split/splitless inlet and FID detector), according to the "GB/T 5750.8-2023 drinking water standard test method Part 8: organic indicators", a one-time analysis of 26 halogenated hydrocarbons in drinking water.(27 kinds of standard, purchased in the standard material cis, trans -1, 2-dibromoethylene).

Method Principle

The sample is placed in a closed headspace vial. Under a certain temperature and pressure, the volatile components of the sample in the headspace vial volatiliize to the liquid space, resulting in vapor pressure, and the gas-liquid phase reaches thermodynamic dynamic equilibrium. Within a certain concentration range, the concentration of the substance to be measured in the gas phase is proportional to the concentration in the water phase.Quantitative extraction of the gas phase part with GC separation, hydrogen flame ionization detector detection, according to the retention time qualitative, standard curve external standard method quantitative.

Instruments and reagents

GC: PANNA Model 1949 GC with ECD detector

Chromatographic column: -624 capillary column 30 ×0.25mm×0.25µm

Headspace device: Automatic headspace sampler HS-25 (Changzhou Panyu Instrument Co., LTD.)

26 kinds of halogenated hydrocarbons were purchased from Ampou Experimental Technology Co., LTD.

General laboratory commonly used equipment, reagents

Analysis steps

1. Analysis conditions:

Headspace sampler method

Heating balance temperature 90℃, valve/quantitative ring temperature 120℃, transmission line 200℃, heating balance time 30min, injection time 1min, pressure pressure 15psi, quantitative pressure 1psi, small flow purge 50ml/min before injection, large flow purge 200ml/min after injection, purge time 2min, Sample plate oscillation grade 0.

GCy method

Column RTX-624 30m*0.25mm*0.25μm;The injection port was 250℃, and the procedure was raised to 1ml/min for 14min, and then increased to 2ml/min at the rate of 1ml/min until the end of sampling.The initial temperature of the column box was 40℃ for 2min, 5℃/min for 100℃ for 0min, 10℃/min for 180℃ for 0min, 20℃/min for 230℃ for 10min.Shunt sampling, shunt ratio 5:1.ECD detector 300℃, constant column flow + tail blow flow 60ml/min.

Headspace conditions:

Heating furnace: 90℃, six way valve: 120℃, transmission line: 200℃;

Balance time: 30min, sampling time: 1min;Purge time: 2min, purge flow: 200ml/min

Pressure: 15psi, quantitative pressure: 1psi;

Chromatographic conditions:

The chromatographic column was 624 column specifications 30m*0.25mm*0.25μm;

Inlet 250℃, shunt injection, shunt ratio 5:1, constant flow 1ml/min;

The initial temperature of column oven is 40℃, keep for 2min, 5℃/min rises to 100℃, keep for 0min, 10℃/min rises to 180℃, keep for 0min, 20℃/min rises to 230℃, keep for 10min;

Maintain the flow rate of 1ml/min for 14 minutes and increase it to 2ml/min at a rate of 1ml/min until the end of sample preparation.

ECD detector 300℃, constant column flow & make up gas :60ml/min.

2. Calibration curve drawing:

Dilute the stock solution step by step to the 6 concentrations in the table below.

Take 6 20ml headspace vials and fill them with 3.7g NaCl respectively, then take 10ml from each of the 6 different concentrations and put them into headspace vials, seal them with a gland, and gently shake them well to be measured.

The specific concentrations of the six configured concentrations are shown in the table below:

Note: Cis-1, 2-dibromoethylene and trans-1, 2-dibromoethylene are isomer mixtures. Since the peak areas are similar, the treatment method in this paper is to divide the nominal original concentration in the standard by 2 to give the respective concentration.

The samples of 6 concentrations were put into the instrument and measured according to the above analysis conditions. The typical spectra of 27 halogenated hydrocarbons are shown in Figure 1:

FIG. 1 Typical spectra of 27 halogenated hydrocarbons

Repetitive spectra:

Repeatability spectrum of concentration 3 (n=8), each substance repeatability within 0.8%~6%.

FIG. 2 Repeatability spectrum of 8 needles at concentration 3

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