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D5808-23 – Standard Test Method Technical Guide
📐 Scope and Application of D5808-23
This standard test method, designated D5808-23, specifically covers the determination of organic chloride in aromatic hydrocarbons, their derivatives, and related chemicals using the technique of microcoulometry. It is the preferred method over Test Method D5194 for products like styrene that are prone to polymerization by the sodium biphenyl reagent.
The method is validated for chloride concentrations up to 25 mg/kg. The limit of detection (LOD) has been calculated from Performance Testing Program (PTP) data as 0.2 mg/kg, and the limit of quantitation (LOQ) as 0.7 mg/kg. With careful analytical technique and the measurement of replicates, this method can be used to successfully analyze samples below the LOD. Values are reported strictly in SI units (mg/kg).
⚙️ Principle of Test and Procedure
The analytical procedure relies on the principle of oxidative pyrolysis. A precisely measured sample is injected into a high-temperature combustion furnace in an oxygen-rich atmosphere. The organic components are broken down into elemental oxides, and the liberated chloride is carried into a microcoulometric titration cell where it is quantitatively measured.
A vital component of the apparatus is the dehydration tube, which contains concentrated sulfuric acid. This chamber scrubs the effluent combustion gases to remove water vapor that would otherwise interfere with the coulometric titration. The method strictly adheres to standard practices for sampling and handling, as defined by Practice D3437. The standard also mandates adherence to OSHA Regulations 29 CFR 1910.1000 and 1910.1200 for safety.
⚠️ Critical Interference Note (Section 1.5): Organic chloride values of samples containing inorganic chlorides will be biased high due to partial recovery of inorganic species during combustion. Interference from inorganic species can be significantly reduced by water washing the sample before analysis. This does not apply to water-soluble samples.
📊 Key Performance Characteristics and Statistical Data
The following table summarizes the critical performance metrics established by the D5808-23 interlaboratory study and PTP data. Results must be rounded in accordance with Practice E29 when determining conformance to specifications.
| 📏 Performance Metric | ⚡ Specified Value | 📐 Source / Note |
|---|---|---|
| 🟦 Applicable Range | up to 25 mg/kg | Highest concentration from the interlaboratory study |
| 🟦 Limit of Detection (LOD) | 0.2 mg/kg | Calculated from PTP data |
| 🟦 Limit of Quantitation (LOQ) | 0.7 mg/kg | Calculated from PTP data |
| 🟦 Preferred Application | Over D5194 | For styrene and polymerizable products |
| 🟦 Unit System | SI (mg/kg) | Mass-based concentration |
| 🟦 Rounding Method | Practice E29 | For conformance determination |
💡 Expert Tip for Low-Level Analysis: According to Section 1.2, this method can successfully analyze concentrations below the 0.2 mg/kg LOD. This requires careful analytical technique and the measurement of replicates. Ensure your Quality Control procedures align with Guide D6809 for optimal performance.
❓ Frequently Asked Questions
🔍 What is the upper concentration limit for the D5808-23 method?
The standard test method is applicable to samples with chloride concentrations up to 25 mg/kg, which represents the highest concentration evaluated in the interlaboratory study.
💡 What are the LOD and LOQ according to the standard?
The Limit of Detection (LOD) is 0.2 mg/kg, and the Limit of Quantitation (LOQ) is 0.7 mg/kg. These were calculated from Performance Testing Program (PTP) data, as referenced in Section 1.2 and Note 1.
⚡ Why is D5808 preferred over D5194 for styrene analysis?
D5808-23 is explicitly preferred for products like styrene because the sodium biphenyl reagent used in Test Method D5194 can cause polymerization of the sample, leading to erroneous results or dangerous reactions.
📌 How can interference from inorganic chlorides be handled in this test?
Interference from inorganic chlorides, which cause a positive bias in the organic chloride result, can be reduced by water washing the sample prior to analysis. This mitigation technique does not apply to water-soluble samples, as stated explicitly in Section 1.5.