| HS Code | 880927 |
| Chemical Name | DL-Aspartic Acid |
| Molecular Formula | C4H7NO4 |
| Cas Number | 617-45-8 |
| Appearance | White crystalline powder |
| Solubility | Slightly soluble in water; insoluble in ethanol and ether |
| Melting Point | 278-280 °C (decomposition) |
| Pka | 1.99 (carboxyl), 3.90 (side chain), 9.90 (amino) |
| Optical Activity | Racemic (no net optical rotation) |
| Density | 1.66 g/cm³ |
| Storage Conditions | Store in a cool, dry, well-ventiated area, away from moisture and strong oxidizing agents |
As an accredited DL-aspartic Acid factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | DL-aspartic Acid is supplied in 25 kg sealed fiber drums with inner polyethylene liners for safe handling and stability. |
| Container Loading (20′ FCL) | DL-aspartic acid is loaded into a 20′ FCL container, with palletized bags or drums securely fastened for safe transport. |
| Shipping | DL-Aspartic acid (CAS 617-45-8), a white crystalline powder, is classified as non-hazardous for transport. Pack in airtight, moisture-resistant containers with proper labeling. Avoid high temperatures and humidity. Not subject to IATA/IMDG/ADR restrictions. Use clean, dry transport to maintain product integrity. |
| Storage | Store DL-aspartic acid in a tightly sealed container in a cool, dry, well-ventilated area, away from direct sunlight and moisture. Maintain room temperature, avoiding extreme heat. Keep separate from oxidizing agents, strong acids, and bases. Ensure the area is clean and free from ignition sources to preserve stability and prevent degradation. |
| Shelf Life | DL-aspartic acid has a shelf life of typically 2–3 years when stored tightly sealed in a cool, dry place. |
DL-aspartic acid in powder form is converted to sodium polyaspartate for cooling-water scale inhibition through a two-stage thermal imide formation and alkaline ring-opening sequence. The monomer is pre-dried in a jacketed conical dryer at 105 ± 5°C under vacuum until free moisture is ≤0.3 wt%, because residual water shifts the imide equilibrium backward and produces sticky reactor wall deposits. The dried charge is transferred to an oil-heated 316L stainless steel kneader reactor fitted with a reflux splitter and nitrogen sweep, where phosphoric acid catalyst is incorporated at 0.5–3.0 wt% relative to monomer. The melt temperature is ramped from 180°C to 230°C over 2–4 h and held for 3–8 h. The critical process window lies between 190°C and 240°C: below 190°C imide cyclization is incomplete, leaving free carboxylate-rich oligomers that depress molecular weight, while above 245°C decarboxylation and chromophore formation raise color and reduce scale-inhibiting carboxylate density. Torque control on the kneader is used as an indirect gelation indicator; a rapid torque increase at constant temperature signals terminal melt branching and requires immediate discharge.
The molten polysuccinimide is quenched with deionized water and hydrolyzed with sodium hydroxide at 40–60°C, maintained at pH 9.0–10.5, to a final solids content of 35–45 wt%. The resulting sodium polyaspartate typically exhibits a weight-average molecular weight of 4,000–10,000 Da by aqueous gel permeation chromatography with polyacrylate calibration, with dispersity generally between 1.5 and 2.5. In finished water-treatment formulations, sodium polyaspartate is supplied at 25–45 wt% active content and applied to recirculating cooling water at 2–15 mg/L as active. Performance is screened according to NACE TM0374-2016; products intended for potable-water contact require certification under NSF/ANSI/CAN 60, and European supply falls under registration obligations of REACH EC 1907/2006. Terminal product types include cooling-tower antiscalants, boiler condensate treatments, and seawater reverse-osmosis antiscalant packages. Batch-to-batch variation in this route is dominated by raw monomer particle size and catalyst dispersion; sieved monomer below 150 µm accelerates imide formation but increases dust explosion exposure, so closed transfer is required.
Agricultural water-retention granules derived from DL-aspartic acid exploit the same polysuccinimide intermediate but introduce lysine or 1,6-diaminohexane during ring opening to create a lightly crosslinked polyaspartate network. The polysuccinimide is cooled to 25–40°C, milled, and suspended in deionized water. A crosslinker is added at 1.0–10 mol% relative to aspartic acid repeat units, followed by sodium hydroxide to achieve 60–90 mol% neutralization. Hydrolysis and crosslinking proceed simultaneously in a twin-screw mixer with an L/D ratio of 48:1 at 40–70°C for 0.5–2.0 h. The gel is extruded through a perforated die plate, dried in a through-circulation belt dryer at 80–95°C to residual moisture ≤10 wt%, then milled and sieved to 150–850 µm. Terminal products include biodegradable water-retention granules for horticultural substrates, cable water-blocking tapes, and absorbent pads for fresh produce packaging. Increasing crosslinker above 10 mol% reduces centrifuge retention capacity below practical utility, while loading below 1.0 mol% produces soluble polymer rather than a discrete gel. Evaluation is benchmarked with EDANA NWSP 230.0.R2 and ISO 11948-1:1996; published data for this specific polyaspartate configuration is limited, and users must verify free swell capacity and saline absorption under load against acrylic superabsorbent controls before substitution.
Neutralized polyaspartic acid produced from DL-aspartic acid functions as a biodegradable polymeric dispersant and crystal growth inhibitor in phosphate-free automatic dishwashing and laundry detergents. The downstream formulation process consists of blending sodium polyaspartate with a molecular weight of 4,000–8,000 Da into heavy-duty liquid laundry products at 0.5–4.0 wt% active and into dishwasher tablet granulate at 1.0–8.0 wt% active. The polymer is added after neutralization under low-shear mixing at 25–35°C to avoid viscosity stratification. In machine dishwashing cycles, the polyaspartate inhibits calcium carbonate and calcium sulfate deposition on glassware and heating elements; in laundry formulations it suspends clay and carbonaceous soil, reducing fabric graying. Compatibility is restricted with cationic surfactants, which precipitate the anionic polymer above 2.0 wt% active; nonionic or anionic surfactant systems are therefore preferred. Compliance is assessed under OECD 301B ready biodegradability and the EU Ecolabel criteria in Commission Decision (EU) 2017/1217. Terminal product types include machine dishwashing gels, phosphate-free laundry liquids, and enzyme-containing multi-compartment detergent packs. Because polyaspartate is sensitive to high-temperature storage above 45°C at alkaline pH 10.5, warehouse stability trials must track viscosity drift and color development over 90 days.
In foliar micronutrient concentrate production, DL-aspartic acid serves as a complexing ligand that maintains zinc, manganese, and iron solubility at alkaline leaf-surface pH. In a 1,000 L jacketed batch vessel, water is charged at 25–40°C, and zinc sulfate, manganese sulfate, and ferrous sulfate are dissolved to target elemental concentrations of 3–12 wt%. DL-aspartic acid is added at 1.5–8.0 wt% of total formulation; the molar ligand-to-metal ratio is held between 1.2:1 and 2.5:1 for divalent cations. The pH is adjusted to 3.5–5.5 with citric acid or potassium hydroxide, and the solution is held at 50–70°C for 60–120 min to complete complexation. After cooling, the product is filtered through a 10 µm bag filter before filling. Terminal product types include water-soluble foliar fertilizers, drip-irrigation micronutrient solutions, and seed treatment liquids. Compliance with Regulation (EU) 2019/1009 requires documented chelated micronutrient content and stability under PFC 1(C)(II); terminology follows ISO 8157:2022. Phosphate-containing formulations are incompatible above pH 4.5 because zinc and iron phosphate precipitates form and the complexed metal fraction collapses, leaving visible sediment in the storage tank.
Oilfield scale squeeze formulations based on sodium polyaspartate derived from DL-aspartic acid are injected downhole to protect production tubing from barium sulfate and calcium carbonate scale during produced-water reinjection. The concentrate is diluted to 5–15 wt% active in filtered seawater or 2–7 wt% potassium chloride brine, followed by a mutual-solvent pad and a displacement volume of 0.5–1.5 times tubing volume. Injection is performed with a high-pressure positive-displacement pump through an in-line static mixer and coiled tubing, with turbulent flow maintained to prevent polymer shear. The polyaspartate adsorbs onto sandstone or carbonate formation surfaces during shut-in; subsequent production releases the inhibitor at concentrations above the minimum effective concentration. High dissolved iron above 25 mg/L in mix water shortens squeeze life through ferric complexation, so oxygen scavenger or citric acid preflush is required. Compliance is screened under NACE TM0374-2016 and biodegradability is benchmarked with OECD 306. Terminal product types include oilfield scale squeeze inhibitors, topside antiscalants, and produced-water re-injection packages. The adsorption-desorption profile is formation-specific; published data for polyaspartate retention on iron-poor sandstone is limited, and core flood testing is required before field deployment.
Concentrated descaling agents for dairy and food-contact stainless steel use DL-aspartic acid as a chelating acid component that reduces re-deposition of calcium sulfate during circulation cleaning. The formulation contains DL-aspartic acid at 2–10 wt%, citric or gluconic acid at 5–20 wt%, low-foam surfactant at 0.1–0.5 wt%, and water. The cleaning bath is heated to 50–70°C and circulated through plate heat exchangers or CIP spray balls at 1.5–3.0 m/s for 30–90 min. The carboxyl groups exchange with calcium ions at pH 2.0–3.5, disrupting existing scale and preventing calcium sulfate film formation on hot surfaces. Terminal product types include CIP descalers for milk processing, reverse-osmosis membrane cleaners, and brewery heat-exchanger acid cleaners. Compliance is grounded in ASTM A380/A380M-17 for stainless steel cleaning and descaling, and where potable-water contact is incidental, FDA 21 CFR 178.1010 may apply. The operating boundary includes avoidance of strong oxidizers: sodium hypochlorite above 200 ppm free chlorine causes oxidative polymer degradation and chlorine gas evolution, so hypochlorite sanitation must be separated from the acid descaling cycle by an intermediate rinse.
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DL-aspartic acid (CAS 617-45-8, C4H7NO4, molecular weight 133.10 g/mol) is the racemic mixture of D- and L-aspartic acid enantiomers. It is supplied as a white crystalline or granular powder with a decomposition point above approximately 270°C. Commercial product models generally encode purity grade, particle-size ceiling, and application class: for example, a designation such as DL-Asp-99-100 identifies an assay specification of 99.0% minimum on the dried basis and a nominal particle size passing a 100-mesh sieve, while DL-Asp-TECH-200 indicates a technical-grade material with a 200-mesh particle-size ceiling for high-dispersion processes. The substance is manufactured by pressure ammoniation of fumaric acid, producing the unresolved racemate; residual fumaric acid, ammonium salts, and maleic acid isomers therefore constitute the principal process impurities monitored during release testing. Crystal morphology varies with crystallisation solvent and cooling rate. Production-scale crystallisers using controlled cooling from 60°C to 15°C at 5°C/h typically yield a free-flowing powder with bulk density in the range 0.60–0.75 g/cm³.
Specification selection depends on downstream regulatory exposure. Food-grade material is commonly tested against Food Chemicals Codex (FCC) monographs and USP-NF general chapters; pharmaceutical intermediates may require additional control of residual fumarate and ammonium ion content. Table 1 lists typical release parameters and test method designations drawn from commercial certificates of analysis. A specific manufacturer’s model may tighten the assay to 99.0–101.0% on the dried basis if the material is intended for pharmaceutical conjugation or peptide synthesis.
| Parameter | Test method | Typical acceptance range |
|---|---|---|
| Appearance | Visual inspection | White crystalline powder |
| Identification | Infrared absorption | Conforms to reference spectrum |
| Assay, dried basis | Non-aqueous titration | 98.5–101.5% |
| Loss on drying | USP <731> | ≤0.50% |
| Residue on ignition | USP <281> | ≤0.10% |
| Chloride | USP <221> | ≤0.020% |
| Sulfate | USP <221> | ≤0.020% |
| Iron | ICP-OES, USP <233> | ≤10 ppm |
| Heavy metals, as Pb | USP <231> where referenced | ≤10 ppm |
| Specific optical rotation | USP <781> | -0.10° to +0.10° |
| Particle size through 200 mesh | Sieving | ≥95.0% |
Batch-to-batch consistency on a 1,500 kg production lot is typically monitored by Karl Fischer titration for moisture and by ion chromatography for residual fumarate. When relative humidity during packaging exceeds 60%, moisture uptake can shift loss-on-drying results by 0.2–0.4%; production sites therefore use dry-air purging in the packaging hopper and sealed aluminium-laminated bags to maintain the release specification.
Chelation of polyvalent metal ions is among the primary technical functions of DL-aspartic acid. The molecule contains two carboxyl groups and one secondary amine; potentiometric titration gives pKa1 1.88, pKa2 3.65, and pKa3 9.60 at 25°C and 0.1 M ionic strength. These values place the β-carboxyl binding window within the pH range typical of circulating cooling water and alkaline cleaner formulations. In high-hardness water containing 250–400 mg/L calcium carbonate equivalent, DL-aspartic acid at 5–20 mg/L active concentration reduces calcium carbonate nucleation by complexing surface Ca²⁺ ions; the effect is measured by the NACE TM0374 dynamic scale-loop test and by conductivity-based induction-time monitoring.
Thermal polycondensation of DL-aspartic acid to polyaspartic acid is sensitive to residual moisture and reactor temperature profile. Laboratory rotary evaporator studies at 190–220°C and 20–50 mbar produce sodium salts with weight-average molecular weight of 1,000–5,000 Da. Production-scale twin-screw reactor systems with controlled residence time and venting are used when molecular weight distribution must be narrow. The screw configuration typically employs an L/D ratio of 40:1 or greater, with vacuum venting in the final third of the barrel to remove condensation water. If the DL-aspartic acid charge contains more than 0.5% moisture, the melt phase becomes adhesive, torque increases, and molecular weight variability broadens; pre-drying in a vacuum dryer at 60–80°C for 4–6 h is therefore required before extrusion. The resulting polyaspartic acid is used as a biodegradable antiscalant and dispersant, with performance evaluated against static scale-inhibition test protocols rather than single-point chelation measurements.
The replacement of L-aspartic acid by racemic DL-aspartic acid is evaluated only when chiral purity is not critical to the target molecule. L-aspartic acid is the proteinogenic enantiomer and is preferentially metabolised in cell culture and clinical nutrition; D-aspartic acid has specialised neuroendocrine research applications but is not incorporated into normal protein synthesis. DL-aspartic acid therefore differs from L-aspartic acid by its zero net optical rotation, lower production cost, and unsuitability for stereospecific solid-phase peptide synthesis unless a racemic diastereomer or achiral derivative is acceptable. Table 2 summarises key comparative properties among the three enantiomeric forms and the related dicarboxylic amino acid glutamic acid.
| Property | DL-aspartic acid | L-aspartic acid | D-aspartic acid | L-glutamic acid |
|---|---|---|---|---|
| CAS number | 617-45-8 | 56-84-8 | 1783-96-6 | 56-86-0 |
| Molecular weight | 133.10 g/mol | 133.10 g/mol | 133.10 g/mol | 147.13 g/mol |
| Optical rotation | 0° racemate | +24.5° to +26.0° in HCl | -24.5° to -26.0° in HCl | +31.5° to +32.5° in HCl |
| Biological utilisation | Limited; D-isomer not proteinogenic | Direct proteinogenic amino acid | Research model, limited | Direct proteinogenic amino acid |
| Primary industrial role | Polyaspartic acid precursor, chelating agent | Nutritional, pharmaceutical, cell culture | Analytical standard, research | Flavour enhancer, nutrition |
In route scouting, DL-aspartic acid may serve as an intermediate for racemic pharmaceutical building blocks or for manufacture of the biodegradable polymer polyaspartic acid, while L-aspartic acid is retained for chiral peptide coupling with active pharmaceutical intermediates. The presence of D-aspartic acid in the racemate does not alter the primary amine-carboxyl stoichiometry, but it does reduce the optical rotation to near zero and changes crystallisation behaviour. Formulators seeking stereospecific metal chelation in asymmetric catalysis should not substitute the racemate without confirming that the D-enantiomer does not compete for binding sites.
During storage and handling, DL-aspartic acid is classified as a non-volatile organic acid. It is incompatible with strong oxidising agents, and under acidic aqueous conditions its secondary amine can react with nitrosating agents to form N-nitrosamines. Formulations containing nitrite-based corrosion inhibitors should therefore maintain pH above 8.0 or avoid direct blending. Before thermal polymerisation, the product should be re-dried if moisture exceeds 0.5%. Storage in sealed aluminium-laminated bags at relative humidity below 60% and temperature below 30°C limits caking and microbiological growth. These handling boundaries derive from standard amino acid stability data rather than product-specific accelerated ageing studies, and published data for shelf-life beyond 24 months under tropical warehouse conditions is limited. End-use compliance must be confirmed against the applicable REACH registration dossier, FDA 21 CFR status, and regional pharmacopoeial monographs because DL-aspartic acid is not automatically interchangeable with L-aspartic acid in food, feed, or injectable pharmaceutical applications.
