The main ingredients of DTPMPA can be described from two perspectives: the active pharmaceutical ingredient itself and the components of its typical commercial product form.
1. The Active Ingredient: DTPMPA Molecule
The primary and active ingredient is the Diethylenetriamine Penta(Methylene Phosphonic Acid) molecule itself. Its chemical structure is the key to its performance.
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Chemical Name: Diethylenetriamine Penta(Methylene Phosphonic Acid)
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Abbreviation: DTPMPA or DTPMP
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CAS No.: 15827-60-8
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Molecular Formula: C<sub>9</sub>H<sub>28</sub>N<sub>3</sub>O<sub>15</sub>P<sub>5</sub> (Acid Form)
Structural Features:
The molecule consists of a central diethylenetriamine backbone (a nitrogen chain with three amine groups) to which five methylene phosphonic acid groups (–CH<sub>2</sub>–PO<sub>3</sub>H<sub>2</sub>) are attached.
This structure provides:
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Multiple Chelating Sites: The five phosphonate groups, rich in oxygen atoms, are powerful chelating agents for metal ions like Calcium (Ca²⁺), Magnesium (Mg²⁺), and especially Iron (Fe³⁺).
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High Stability: The C-P bonds are very stable, making the molecule resistant to hydrolysis and thermal degradation.
2. Ingredients in a Commercial DTPMPA Product
In commerce, you do not buy 100% pure DTPMPA acid. It is typically sold as an aqueous solution with specific characteristics. The main ingredients in a standard commercial product (e.g., DTPMPA·Na<sub>7</sub>, the hepta-sodium salt) are:
| Ingredient | Typical Concentration | Purpose and Description |
|---|---|---|
| DTPMPA (as active acid) | ~ 50% by weight | The active ingredient responsible for scale inhibition, corrosion inhibition, and chelation. The product’s strength is often expressed as the content of this active acid. |
| Water (H₂O) | ~ 45 – 50% | The solvent. It creates a liquid solution that is easy to transport, handle, and dose accurately into water systems. |
| Sodium Hydroxide (NaOH) | (Used in manufacturing) | Used to neutralize the acidic phosphonic groups, converting the product into a soluble sodium salt. This adjusts the pH and prevents the product from being highly corrosive. |
| Minor Impurities | < 5% | These are typical by-products from the manufacturing process and may include: • Inorganic Salts (e.g., sodium chloride, sodium sulfate). • Other Phosphonates (e.g., lower homologs with fewer phosphonate groups). • Orthophosphite/Phosphonate from potential decomposition. |
Typical Specification of a Commercial DTPMPA Solution:
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Active Acid Content: 50% ± 2%
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pH (1% aqueous solution): 2.0 – 3.0 (for the acid form) or ~7-9 (for the neutralized salt form)
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Density (20°C): ~1.3 – 1.4 g/cm³
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Appearance: Colorless to pale yellow transparent liquid
In summary: When you purchase “DTPMPA,” you are primarily buying a ~50% aqueous solution of the active DTPMPA molecule, typically neutralized to a sodium salt for stability and ease of use. The other main ingredient is water, with small amounts of process-related impurities.