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Top Air Phase Chromatography Series Lecture (7)

Headspace Chromatographic Analysis of Five Low Carbon Halogenated Hydrocarbons

Low-carbon halogenated hydrocarbons play a crucial role in the chemical industry as raw materials for industrial production and common reagents in laboratories. However, incidents of poisoning due to these compounds have occurred frequently. For instance, untreated wastewater from manufacturers has been discharged into rivers, leading to the death of fishermen and fish eagles. Additionally, air pollution in workshops has caused workers to suffer from poisoning. This article presents a headspace chromatographic analysis method developed through animal experiments and real-world case studies.

1. Instruments and Reagents

SIGMA 2B Gas Chromatograph

HS-6 Headspace Sampling Device (manufactured by US PE company)

CR-3A Microprocessor (product of Shimadzu Corporation, Japan)

All reagents are of analytical grade (produced by Tianjin Chemical Reagent II)

2. Headspace Chromatographic Conditions

Inlet temperature: 100°C, FID temperature: 150°C, capillary column SE-54 (25 m × 0.25 mm), column temperature: 70°C, sample temperature: 80°C, sample holding time: 20–25 minutes, injection pressurization time: 5 seconds, split ratio: 10:1, N₂: 124 kPa, H₂: 138 kPa, Air: 207 kPa.

3. Sample Preparation

1. Standard Sample (V/V)

Concentrated mixed standard solution: CH₂Cl₂ : CCl₄ : CHCl₃ : C₂H₄Cl₂ : C₂HCl₃ = 0.5 : 1.5 : 1 : 0.5 : 1.5

Internal standard solution: C₂H₄Cl₂ : CH₃OH = 0.4 : 100

Dilute standard solution: concentrated standard solution : methanol = 1 : 25

2. Control Samples

Negative control: 0.5 g blank organ (liver) + 25 ml methanol + 0.5 ml normal saline

Positive control: 0.5 g blank organ (liver) + 25 ml diluted standard solution + 0.5 ml physiological saline

3. Sample to be Tested

Accurately weigh 0.500g (mL) of poisoned rabbit organs (including body fluids), add 25 ml internal standard solution, then add 0.5 ml physiological saline.

4. Determination of Recovery Rate

Weigh 0.5g of blank liver, add 0.5ml of normal saline, add 25ml of diluted standard solution, mix well. The recovery rate in the liver (n=4) is shown in Figure 1 and the data is presented in the following table: