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Top Air Phase Chromatography Series Lecture (7)

Headspace Chromatographic Analysis of Five Low Carbon Halogenated Hydrocarbons

Low-carbon halogenated hydrocarbons are widely used in the chemical industry as raw materials and reagents in laboratories. However, their improper handling can lead to serious health hazards. There have been several cases where workers were poisoned due to air pollution in workshops, and environmental contamination from industrial waste has caused harm to wildlife and local communities. This article presents a headspace chromatographic method developed through animal experiments and real-world case studies to detect these compounds effectively.

1. Instruments and Reagents

SIGMA 2B Gas Chromatograph

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

CR-3A Microprocessor (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 0.5 g of blank liver, add 0.5 ml normal saline, add 25 ml of diluted standard solution, mix well. The recovery rate was measured in the liver (n=4), with results shown in Figure 1 and the following table.