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D3920-18 – Standard Test Method Technical Guide
📐 Scope and Test Method Summary
This test method covers the determination of dissolved and total recoverable strontium in water and wastewater by atomic absorption spectroscopy. The method is applicable in the range from 0.1 to 1 mg/L of strontium. The range may be extended by dilution of the original sample. Round-robin data were obtained in natural and reagent water matrices, and it is the user’s responsibility to ensure validity for untested matrices.
The values stated in SI units are regarded as standard, with inch-pound conversions provided for information only. This standard does not address all safety concerns, and it is the user’s responsibility to establish appropriate safety, health, and environmental practices.
⚙️ Test Procedure and Sample Preparation
Strontium is determined by atomic absorption spectrophotometry. The sample is aspirated into an air-acetylene flame following the addition of lanthanum chloride/potassium chloride solution. Samples containing particulate matter that may clog the aspirator capillary or burner are filtered through a 0.45-µm membrane filter prior to testing. Total recoverable strontium is determined using a digestion procedure.
| 🟦 Parameter | 📏 Specification |
|---|---|
| Method | Atomic Absorption Spectrophotometry |
| Flame Type | Air-acetylene |
| Reagent Addition | Lanthanum chloride/Potassium chloride |
| Concentration Range | 0.1 to 1 mg/L |
| Sample Filtration | 0.45-µm membrane filter |
Always add the lanthanum chloride/potassium chloride solution to both samples and standards to ensure consistent results and minimize interferences.
📊 Quality Control and Significance
This test method is significant for determining strontium levels in water, particularly in well waters from the midwestern United States where strontium levels can reach up to 39 mg/L. The method provides reliable results for strontium and helps correct calcium results obtained by other methods.
Quality control includes the use of a laboratory control sample with a certified concentration of strontium. Referenced documents include practices for sampling, precision, and holding time, such as D3370, D2777, and D4841.
❓ Frequently Asked Questions
🔍 What is the concentration range for strontium in this test method?
The test method is applicable in the range from 0.1 to 1 mg/L of strontium. This range can be extended by diluting the original sample.
💡 How should samples with particulate matter be prepared?
Samples containing particulate matter that may clog the aspirator should be filtered through a 0.45-µm membrane filter prior to analysis.
⚡ What safety precautions are associated with this test method?
Specific precautionary statements are provided in sections 8.4 and 8.9 of the standard. Users must establish appropriate safety protocols based on the sample matrices.
📌 Why is the lanthanum chloride/potassium chloride solution added?
The solution is added to the sample before aspiration to minimize interferences from other elements, ensuring accurate determination of strontium.