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D3352-15 – Standard Test Method Technical Guide
📋 Overview and Applicability of D3352-15
ASTM D3352-15 provides a standard atomic absorption spectrophotometry (AAS) method for the determination of soluble strontium ion in brackish water, seawater, and brines. This test method is applicable for samples containing strontium concentrations ranging from 5 to 2100 mg/L. Strontium is measured in its ground state by aspirating the specimen into an oxidant-fuel flame and measuring the attenuation of radiation from a strontium hollow cathode lamp.
Values stated in SI units are regarded as the standard. This method is significant for environmental monitoring and industrial process control where strontium ion concentration is a critical parameter.
⚠️ Important Note: The values stated in SI units are regarded as standard. The user of this standard must establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Always refer to Terminology D1129 for definition of terms.
⚙️ Test Procedure – Method of Additions
The test method is dependent on the fact that metallic elements, in the ground state, absorb light of the same wavelength they emit when excited. To analyze strontium, a hollow cathode lamp provides the characteristic radiation. The sample is aspirated into a flame, and a monochromator isolates the radiation. A photosensitive device measures the attenuated transmitted radiation.
Since the variable and sometimes high concentrations of matrix materials in waters and brines affect absorption differently, it is difficult to prepare standards sufficiently similar to the samples. To overcome this difficulty, the method of additions is used. In this procedure, three identical sample aliquots are prepared. Varying amounts of a standard strontium solution are added to two of the aliquots. The concentration readings are recorded, and the original sample concentration is calculated mathematically.
| 📏 Parameter | 🎯 Specification / Requirement |
|---|---|
| Analyte | Soluble Strontium Ion (Sr²⁺) |
| Matrix | Brackish Water, Seawater, Brines |
| Detection Range | 5 – 2100 mg/L |
| Methodology | Atomic Absorption Spectrophotometry (AAS) |
| Calibration Technique | Method of Additions (Standard Addition) |
💡 Technical Tip: Because of the variable matrix in seawater and brines, standard calibration curves are insufficient. Always employ the method of additions as prescribed in Section 4.2 of D3352-15 for accurate results.
🔬 Interferences and Apparatus
The analysis requires an atomic absorption spectrophotometer consisting of an atomizer and burner, pressure-regulating devices for the oxidant and fuel, a hollow cathode lamp of the element to be determined (Strontium), a monochromator, and a photosensitive detector.
Interferences: Chemical suppression caused by silicon (Si), aluminum (Al), and phosphate (PO₄³⁻) is controlled by the addition of lanthanum. The lanthanum also acts to control ionization interference, which is common in high-temperature flames used for refractory elements.
| 🟦 Interference | ⚡ Suppression Mechanism | 🧪 Control Agent |
|---|---|---|
| Silicon (Si) | Chemical / Refractory formation | Lanthanum (La) |
| Aluminum (Al) | Chemical / Refractory formation | Lanthanum (La) |
| Phosphate (PO₄³⁻) | Chemical / Refractory formation | Lanthanum (La) |
| Ionization | Ionization suppression | Lanthanum (La) |
Referenced documents for the complete procedure include Practices D3370 (sampling closed conduits), Guide D5810 (spiking), and Specification D1193 for reagent water.
❓ Frequently Asked Questions
🔍 What types of water samples can be analyzed using D3352-15?
This test method is specifically designed for the determination of soluble strontium ion in brackish water, seawater, and brines.
💡 Why is the “method of additions” specifically required?
The variable and often high concentrations of matrix materials in waters and brines affect absorption differently. It is difficult to prepare calibration standards sufficiently similar to the samples without this technique.
⚡ What is the concentration range for strontium in this test?
Samples containing from 5 to 2100 mg/L of strontium may be analyzed by this test method.
📌 What role does Lanthanum play in this method?
Lanthanum is added to control chemical suppression caused by silicon, aluminum, and phosphate. It also controls ionization interference.