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D2703-95 – Standard Test Method Technical Guide
🧪 Purpose and Scope of UV Absorbance Testing
This standard practice (D 2703 – 95) provides a standardized method for measuring the ultraviolet (UV) absorption spectrum of rubber chemicals soluble in spectroscopic solvents. The recommended spectral range for analysis lies between 200 and 400 nm.
The core value of this practice lies in its ability to differentiate between rubber chemicals based on the spectral position of their absorption bands and their absorptivities at selected wavelengths. This approach is critical for material identification, routine quality control, and comparative research and development studies.
⚠️ User Responsibility: This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user to establish appropriate safety, health, and regulatory practices prior to performing the test.
⚙️ Standard Apparatus and Instrument Configuration
Correct instrumentation is essential for compliance with this practice. A manual or recording spectrophotometer (single or double beam) equipped to handle liquid samples is required. The instrument must be capable of covering the 200 to 400 nm spectral region. A micro balance with a 0 to 25 mg capacity is desirable for precise sample preparation, and low actinic (red or brown) glass volumetric flasks should be used to minimize light degradation of samples.
| 🟦 Component | 📏 Specification from Standard |
|---|---|
| Spectrophotometer | Manual or Recording, 200–400 nm range |
| Sample Cell Path Length | 1 cm (desirable, longer/shorter allowed) |
| Micro Balance Capacity | 0 – 25 mg (tare for 50 mg capacity) |
| Sample Cells | Fused silica |
| Volumetric Glassware | Low actinic (red or brown glass) |
💡 Performance Check: If the performance of the spectrophotometer must be evaluated, refer to Practice E 275 for describing and measuring its performance.
📊 Reagents and Measurement Protocol
All reagents used must be reagent grade chemicals conforming to the specifications of the American Chemical Society. The test itself determines the UV absorbance spectrum by measuring the absorbance of a solution with a known concentration in a cell of known sample path length.
Thorough reporting is mandatory; the conditions of measurement and sample preparation must be recorded for the rubber chemical under examination (as noted in Section 13.2 of the standard).
| 🔍 Parameter | ⚡ Requirement / Note |
|---|---|
| Reagent Grade | ACS Reagent Grade chemicals required |
| Solution Preparation | Must be a solution of known concentration |
| Measurement Wavelength | Between 200 and 400 nm |
| Essential Reporting | Conditions of measurement and sample preparation (per 13.2) |
❓ Frequently Asked Questions
🔍 What is the standard wavelength range for UV absorbance measurement in this practice?
The standard specifically addresses the measurement of the ultraviolet absorption spectrum in the region between 200 and 400 nm.
💡 What type of glassware is required for preparing sample solutions?
Low actinic (red or brown) glass volumetric flasks should be used to minimize the harmful effects of light on the rubber chemical solutions during preparation and storage.
⚡ What is the recommended sample cell path length?
A cell with a sample path length of 1 cm is considered desirable. However, cells with longer or shorter sample path lengths may be employed to accommodate solutions of varying concentrations.
📌 Which ASTM standards are referenced for general technique and terminology?
Practices E 169 are referenced for general techniques of UV-Visible quantitative analysis. Terminology E 131 defines the terms and symbols used in the standard, providing a crucial framework for interpretation.