Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D4638-16 – Standard Test Method Technical Guide
📐 Sample Types and Collection Requirements
This guide, designated ASTM D4638-16 (Reapproved 2023), specifies standardized procedures for preparing biological samples from aquatic environments—including streams, rivers, ponds, lakes, estuaries, and oceans—for inorganic chemical analysis. It covers diverse organisms such as plankton, mollusks, fish, and plants (Section 1.1). The standard is applicable to the determination of volatile, semivolatile, and nonvolatile inorganic constituents (Section 1.2).
To prevent contamination, Section 4.1 mandates that sampling equipment be nonmetallic or TFE-fluorocarbon-coated. All samples must be stored in plastic containers and kept at 4 °C or frozen until returned to the analysis facility.
| 🟦 Organism Type | 📏 Initial Preparation | 🎯 Required Tool / Method |
|---|---|---|
| Plankton (small) | Mix and allow to settle (4.3) | Remove supernatant/occluded water |
| Fish, Mollusks (large) | Pat dry with paper towels (4.3) | Paper towels |
| Tissue Excision (any) | Dissection (4.4) | Plastic knife or TFE-fluorocarbon-coated scalpel |
| Foreign Objects | Mechanical removal (4.2) | Visual examination / Low-power microscope |
💡 Key Workflow Step: Always allow frozen samples to return to room temperature before processing. Moisture determinations must be performed on a separate sample aliquot from that used for volatile or semivolatile constituent analysis (Section 4.5).
⚙️ Preparation Procedures for Target Analytes
The specific preparation pathway depends on whether the target analytes are volatile, semivolatile, or nonvolatile. Sections 4.6 through 4.8 provide distinct instructions to ensure the integrity of the constituents during preparation.
Values stated in SI units are regarded as standard (Section 1.3). The user is responsible for establishing safety and health practices, referencing specific hazard statements (Section 9.3.3) where applicable.
| ⚡ Constituent Type | 🔬 Sample Format for Analysis | 📐 Reporting / Drying Basis |
|---|---|---|
| Volatile | Wet (supernatant removed per 4.3) | Dry, original-sample basis (using separate moisture test per 4.6) |
| Semivolatile | Wet OR Dried at adequate temperature | As specified in the corresponding analytical procedure (4.7) |
| Nonvolatile | Dried at adequate temperature | As specified in the corresponding analytical procedure (4.8) |
📌 Regulatory Note (Section 1.4): This standard does not purport to address all safety concerns. It is the responsibility of the user to determine the applicability of regulatory limitations and implement appropriate environmental practices prior to use. For a specific hazard statement related to this procedure, see Section 9.3.3.
📊 Supporting Standards and Terminology
Proper application of D4638 relies on specific terminology and supporting standards. Section 3.1 directs users to Terminology D1129 for formal definitions of terms used throughout the guide. Furthermore, Section 2.1 references Specification D1193 for Reagent Water, ensuring that water purity does not compromise the integrity of the