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D4657-92 – Standard Test Method Technical Guide
📖 Scope and Applicability
ASTM D4657-92 is a standard test method for the determination of polynuclear aromatic hydrocarbons (PAHs) in water and wastewater. It has been successfully applied to distilled water, tap water, surface water, and wastewaters such as effluent from an oil refinery, blast furnace, and combined coke oven and blast furnace. The method is intended for analysts experienced with high-performance liquid chromatography (HPLC).
The following compounds are within the scope of this method:
| 🟦 Compound | 🔬 Detection Mode |
|---|---|
| Acenaphthene | UV/Fluorescence |
| Acenaphthylene | UV/Fluorescence |
| Anthracene | UV/Fluorescence |
| Benzo(a)anthracene | UV/Fluorescence |
| Benzo(a)pyrene | UV/Fluorescence |
| Benzo(b)fluoranthene | UV/Fluorescence |
| Benzo(ghi)perylene | UV/Fluorescence |
| Benzo(k)fluoranthene | UV/Fluorescence |
| Chrysene | UV/Fluorescence |
| Dibenzo(ah)anthracene | UV/Fluorescence |
| Fluoranthene | UV/Fluorescence |
| Fluorene | UV/Fluorescence |
| Indeno(1,2,3-cd)pyrene | UV/Fluorescence |
| Naphthalene | UV/Fluorescence |
| Phenanthrene | UV/Fluorescence |
| Pyrene | UV/Fluorescence |
⚙️ Test Procedure and Method Summary
The analytical procedure begins with the extraction of 1 L of water sample using methylene chloride. The extract is concentrated via Kuderna-Danish (K-D) evaporation and subjected to cleanup on a silica gel column. The PAH fraction is collected, further concentrated, and solvent-exchanged with acetonitrile to precisely 1 mL. Final analysis is performed using reverse-phase HPLC with a Perkin Elmer PAH/10 or equivalent C-18 column, employing a combination of isocratic and gradient elution with acetonitrile and water as the mobile phase. Detection is achieved using both ultraviolet and fluorescence detectors.
⚠️ Important Note: This method is limited to use by analysts familiar with HPLC or under close supervision. It is the user’s responsibility to ensure the validity of this test method for waters of untested matrices. Specific safety precautions are detailed in Section 9 of the standard.
📊 Key Analytical Parameters
| 📐 Parameter | 🎯 Specification |
|---|---|
| Column | Perkin Elmer PAH/10 or equivalent C-18 reverse phase |
| Mobile Phase | Acetonitrile and water (isocratic/gradient elution) |
| Detection | Ultraviolet and fluorescence detectors |
| Sample Volume | 1 L |
| Extraction Solvent | Methylene chloride |
| Final Extract Volume | 1 mL in acetonitrile |
💡 Tip: For confirming compound identities, the standard recommends using two different types of reverse phase HPLC columns, both ultraviolet and fluorescence detection, or gas chromatography/mass spectrometry screening procedures.
❓ Frequently Asked Questions
🔍 Question: What is the scope of ASTM D4657-92?
Answer: This test method covers the determination of certain polynuclear aromatic hydrocarbons (PAHs) in water and wastewater, including surface water and industrial effluents such as those from oil refineries and blast furnaces.
💡 Question: Which PAHs can be analyzed using this method?
Answer: The method can determine 16 PAHs including acenaphthene, anthracene, benzo(a)pyrene, chrysene, naphthalene, pyrene, and others as listed in the compounds table.
⚡ Question: What extraction solvent is used in this method?
Answer: Methylene chloride is used for the initial extraction, and the final extract is solvent-exchanged with acetonitrile to a volume of 1 mL.
📌 Question: What are the key analytical techniques involved?
Answer: The method involves Kuderna-Danish evaporation, silica gel column chromatography, and high-performance liquid chromatography with reverse phase column and UV/fluorescence detection.