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D3598-89 – Standard Test Method Technical Guide
🧪 Overview and Scope of D3598-89
The Standard Test Method D3598-89 (Reapproved 2024) specifies the enzymatic determination of citrate in both liquid and solid synthetic detergents. This method relies on the high specificity of the citrate lyase enzyme system. The test method is particularly applicable to most detergents where the citrate content is at a minimum concentration of approximately 5% by weight. Values stated in SI units are regarded as the standard.
| 🟦 Parameter | 🎯 Specification / Detail |
|---|---|
| Analyte | Citrate |
| Methodology | Enzymatic (Citrate Lyase / Malic Dehydrogenase / NADH) |
| Detection Wavelength | 340 nm |
| Minimum Concentration | ~5% in synthetic detergents |
| Interference Resistance | Highly specific; other organic acids do not interfere |
⚙️ Test Procedure and Instrumentation
The enzymatic reaction is monitored spectrophotometrically. The decrease in absorbance at 340 nm, caused by the formation of β-nicotinamide adenine dinucleotide in its oxidized form