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D6505-00 – Standard Test Method Technical Guide
🔬 Scope and Significance of the Test Method
This test method provides a basis for the determination of the normal-propyl bromide (weight %) in the presence of stabilizers and impurities, in virgin or reclaimed normal-propyl bromide (nPB). The application range is from 50 wt % to 100 wt %. The analytical procedure describes the determination of the assay of n-propyl bromide by gas chromatography using an internal standard, with results reported in weight percent.
This test method is significant as it provides an accurate analysis of normal-propyl bromide concentration for virgin, formulated, or reclaimed material. However, compounds that co-elute with normal-propyl bromide or with the internal standard (n-heptane) may interfere with this test method and must be considered when interpreting results.
⚠️ Warning: Compounds that co-elute with normal-propyl bromide or n-heptane (internal standard) can interfere with the assay. Verify the absence of interfering substances before analysis.
⚙️ Apparatus and Required Chemicals
The apparatus specified includes a gas chromatograph (Hewlett Packard 5890 Series II or equivalent) equipped with a split/splitless injector, a flame ionization detector, and an autosampler. A 30 m by 0.25 mm capillary column with a 1.0 µm film thickness (AllTech AT-5 or equivalent) is required. Additional equipment includes a 5 µL or 10 µL GC autosampler syringe, a data acquisition and analysis device (VAX MULTICHROM or equivalent), 2 mL glass crimp top vials with TFE-fluorocarbon-lined silicone septa, a 25 mL volumetric pipet, 32 mL glass vials with TFE-fluorocarbon-lined screw caps, borosilicate glass transfer pipets, and a precision balance accurate to 0.1 mg.
| 🛠️ Apparatus Component | 📏 Specification |
|---|---|
| Gas Chromatograph | HP 5890 Series II or equivalent; split/splitless injector, FID, autosampler |
| Column | 30 m × 0.25 mm, 1.0 µm film thickness, AllTech AT-5 or equivalent capillary column |
| Syringe | 5 µL or 10 µL GC autosampler syringe |
| Data System | VAX MULTICHROM or equivalent chromatography data system |
| Balance | Precision balance accurate to 0.1 mg |
Required chemicals include n-propyl bromide (1-bromopropane, 99+ %), n-heptane (internal standard, reagent grade 99.5+ %), and methylene chloride (99+ %). All chemicals should be stored and handled in accordance with standard laboratory safety practices.
💡 Tip: Use a precision balance accurate to 0.1 mg when weighing the internal standard and n-propyl bromide for the calibration mixture. Record all actual weights precisely, as the accuracy of the final assay depends on the accuracy of these initial measurements.
📊 Chromatographic Conditions and Calibration Procedure
The analysis is performed using the following gas chromatographic conditions. The injector temperature is set to 150 °C and the detector temperature to 250 °C. The temperature program begins at 30 °C for 10 minutes, then ramps from 30 °C to 250 °C at 15 °C/min, and holds at 250 °C for 10 minutes. Helium or nitrogen is used as the carrier gas at 1 mL/min with a split flow of 25 mL/min and a column head pressure of 7.5 psi. The injection volume is 0.5 µL.
| 📐 Parameter | 🎯 Setting |
|---|---|
| Injector Temperature | 150 °C |
| Detector Temperature | 250 °C |
| FID Detector Range | Most sensitive setting |
| Temperature Program | 30 °C for 10 min → 30 °C to 250 °C at 15 °C/min → hold at 250 °C for 10 min |
| Carrier Gas | He or N₂ at 1 mL/min |
| Split Flow | 25 mL/min |
| Column Head Pressure | 7.5 psi |
| Make-up Gas | He or N₂ at 30 mL/min |
| Injection Volume | 0.5 µL |
To prepare the internal standard calibration mixture, carefully weigh about 0.25 g of n-heptane and about 0.5 g of n-propyl bromide into a 32 mL glass vial. Record the actual weights. Pipet 25 mL of methylene chloride into the vial, cap immediately, and mix well. Transfer approximately 1 mL of this solution into an autosampler vial, cap, and analyze using the specified chromatographic conditions.
❓ Frequently Asked Questions
🔍 What is the application range of the test method?
The test method covers the assay of normal-propyl bromide from 50 wt % to 100 wt % in virgin or reclaimed nPB.
The test method covers the assay of normal-propyl bromide from 50 wt % to 100 wt % in virgin or reclaimed nPB.
💡 What internal standard is specified and what purity is required?
n-Heptane is used as the internal standard. The required purity is reagent grade, 99.5+ %.
n-Heptane is used as the internal standard. The required purity is reagent grade, 99.5+ %.
⚡ What are the key gas chromatographic conditions?
The injector is set to 150 °C, detector to 250 °C, carrier gas at 1 mL/min, injection volume 0.5 µL, with a temperature program starting at 30 °C for 10 minutes then ramping at 15 °C/min to 250 °C.
The injector is set to 150 °C, detector to 250 °C, carrier gas at 1 mL/min, injection volume 0.5 µL, with a temperature program starting at 30 °C for 10 minutes then ramping at 15 °C/min to 250 °C.
📌 What balance accuracy is required for this procedure?
A precision balance accurate to 0.1 mg is required for weighing the calibration mixture components.
A precision balance accurate to 0.1 mg is required for weighing the calibration mixture components.