| HS Code | 591342 |
| Chemical Name | DL-Lysine Hydrochloride |
| Molecular Formula | C6H15ClN2O2 |
| Molecular Weight | 182.65 g/mol |
| Cas Number | 70-53-1 |
| Appearance | White crystalline powder |
| Melting Point | 263-265 °C (decomposes) |
| Specific Rotation | 0° (optically inactive) |
| Solubility In Water | Freely soluble |
| Solubility In Ethanol | Practically insoluble |
| Ph 1 Aqueous Solution | 5.0-6.0 |
| Pka | 2.18, 8.95, 10.53 |
As an accredited DL-lysine Hydrochloride factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | DL-lysine Hydrochloride is packaged in 25 kg fiber drums with double polyethylene liners, tightly sealed and clearly labeled. |
| Container Loading (20′ FCL) | 20′ FCL container loading of DL-lysine Hydrochloride: packed in 25 kg bags on pallets, securely stowed for safe transport. |
| Shipping | DL-lysine Hydrochloride ships as a stable, non-hazardous powder. It should be packed in sealed, moisture-resistant containers, protected from humidity and direct sunlight. Use labeled packaging with proper documentation. No special hazard declaration is required, but standard handling and transportation protocols apply to ensure product purity and safety. |
| Storage | Store DL-lysine Hydrochloride in a tightly sealed, original or equivalent container in a cool, dry, well-ventilated area. Protect from moisture, direct sunlight, and excessive heat. Keep away from strong oxidizing agents and incompatible chemicals. Maintain consistent room temperature, avoid humidity exposure, and ensure proper labeling. Under these conditions, stability is preserved for the stated shelf life. |
| Shelf Life | Shelf life: typically 3 years when stored in a cool, dry, airtight container away from light and moisture. |
In microbial bioprocess development where lysine auxotrophy is employed as a selectable marker, DL-lysine hydrochloride enters chemically defined minimal media as a racemic nitrogen source. The L-enantiomer is metabolized through the diaminopimelate pathway, while the D-enantiomer remains largely inert in E. coli K-12 derivatives; the resulting osmolality contribution must be accounted for in feed rate calculations. Media used for non-clinical industrial strain screening are prepared and released under ISO 11133:2014, with batch documentation covering sterilization at 121°C for 30 min and final pH 7.0±0.2. The addition ratio in chemically defined formulations is bracketed at 0.05 g/L, 0.25 g/L, and 0.50 g/L; concentrations above 0.80 g/L raise osmolality by approximately 5 mOsm/kg without improving specific growth rate, though published data for this specific racemic configuration are limited. Downstream production uses a 100 L stainless steel dissolution vessel with bottom-mounted magnetic impeller; the powder is dissolved in water at 40°C, sterile-filtered through a 0.2 μm polyethersulfone capsule, and transferred aseptically into a 1 m³ seed fermenter. Autoclaving at pH above 8.0 is avoided because lysine degradation accelerates and Maillard-type browning can occur if reducing sugars are present. Terminal finished product types include ready-to-rehydrate auxotrophic screening kits, restriction endonuclease production seed cultures, diagnostic DNA polymerase biomass, and defined minimal media powders for industrial microbiology laboratories.
Poly-DL-lysine coating for neural cell culture and diagnostic surface preparation is produced through Nε-protection, N-carboxyanhydride cyclisation, and amine-initiated ring-opening polymerisation. DL-lysine hydrochloride is first Nε-benzyloxycarbonylated at 5°C and pH 10.5 using benzyl chloroformate at 1.05 molar equivalents; after filtration, the protected monomer is cyclised with triphosgene in anhydrous tetrahydrofuran under nitrogen. Moisture content during cyclisation must remain below 50 ppm because water attacks the NCA carbonyl, releasing carbon dioxide and terminating propagation. Polymerisation is initiated with n-hexylamine at monomer:initiator ratios from 50:1 to 200:1; deprotection with hydrogen bromide in trifluoroacetic acid yields poly-DL-lysine hydrobromide. For tissue culture surfaces, the batch is dissolved in phosphate-buffered saline at 0.01–0.10 mg/mL; a 1.0 mL aliquot per 9.6 cm² is incubated at 37°C for 60 min, then aspirated and air-dried in a sterile laminar flow environment. Finished articles are tested under ISO 10993-5:2009 for cytotoxicity and USP <87> for biological reactivity; manufacturing is maintained under ISO 13485:2016. The operational boundary is strict: pre-drying of glassware is mandatory when relative humidity exceeds 60%, and contact with primary amine impurities must be avoided because they act as competing initiators. Batch rejection occurs when amine density variation across a 12-well plate exceeds 15% by acid orange II assay. Terminal finished product types include 12-well and 96-well tissue culture plates, glass coverslips, microcarrier beads for stirred-tank cell expansion, and electrochemical biosensor chips.
| Monomer:initiator ratio | Target number-average molecular weight (g/mol) | Maximum polydispersity index | Typical coating concentration (mg/mL) |
|---|---|---|---|
| 50:1 | 30,000–50,000 | 1.25 | 0.10 |
| 100:1 | 80,000–120,000 | 1.35 | 0.05 |
| 200:1 | 180,000–250,000 | 1.45 | 0.01 |
When lauroyl chloride is fed to an aqueous solution of DL-lysine hydrochloride at pH 10.5±0.2, the reaction produces a mixture of Nα- and Nε-acyl products; selective crystallisation at pH 2.5 enriches the desired Nε-lauroyl lysine, while the Nα-acylated by-product remains below 3.0 mol% as confirmed by 13C-NMR. The Schotten–Baumann reaction is executed in a 500 L glass-lined jacketed reactor equipped with pH-stat and torque-sensing anchor stirrer at 60 rpm; fatty acid chloride is fed at 1.05 molar equivalents relative to the lysine feed while 1.0 M sodium hydroxide holds pH. The addition ratio in the final cosmetic powder is 1.0–5.0 wt% for Nε-lauroyl lysine, and in pigment surface treatment the coating load is 10–20 wt% relative to pigment mass. After acylation, the batch is acidified to pH 2.5, filtered, washed with deionised water until chloride content is below 0.1%, and vacuum-dried at 45°C for 12 h. Finished ingredient compliance follows EC 1223/2009 for cosmetic products, Regulation (EC) No 1907/2006 for registration, and ISO 16128-2:2017 for natural origin index reporting; residual lauric acid is controlled to 0.5%. The process constraint is pH: above 11.0 acyl chloride hydrolysis produces soap that increases filtration resistance, while below 9.8 reaction rate drops below the target space-time yield. Terminal finished product types include loose mineral powders, pressed powder eyeshadows, cream-to-powder blushes, water-in-oil sunscreen sticks, and dry shampoo formulations.
DL-lysine hydrochloride is converted into N-acetyl-DL-lysine before entering an immobilised acylase fixed-bed reactor that selectively hydrolyses the L-acetyl derivative. N-acetylation is carried out in a 50 L jacketed glass reactor with acetic anhydride at 2.2–2.5 molar equivalents, pH maintained below 1.5, and temperature held at 15–20°C to limit racemisation; the substrate is then loaded at 10–15% w/v into the enzyme reactor at 37°C and pH 7.5±0.2. The fixed-bed column is run with a pressure bound of 1.5 bar and linear flow rate of 0.5–1.0 cm/min; backpressure above this value indicates enzyme support compaction and requires unloading. The unhydrolysed N-acetyl-D-lysine is separated from free L-lysine by cation-exchange chromatography, acid-hydrolysed, and crystallised from water/ethanol to furnish D-lysine hydrochloride with enantiomeric excess above 99.0% measured by chiral HPLC at 210 nm using a chiral crown ether column. Process compliance for pharmaceutical intermediates follows ICH Q7 and ICH Q11; analytical release uses Ph. Eur. 2.2.31 for chromatographic separation and Ph. Eur. 2.4.24 for residual solvents, with residual acetic acid controlled below 0.5%. Operational boundaries include the exclusion of Cu²⁺ and Zn²⁺ above 10 ppm because aminopeptidase activity is metal-sensitive, and the avoidance of amine-based buffers during the acylation step. Published data for this specific racemic feedstock configuration are limited, but batch-to-batch variance is dominated by fixed-bed pressure drop across the immobilised enzyme support. Terminal finished product types include D-lysine hydrochloride for solid-phase peptide synthesis, L-lysine acetate for parenteral amino acid admixtures, and protected lysine building blocks for desmopressin-related peptide analogues.
In analytical laboratories, DL-lysine hydrochloride is employed as a basic amino acid retention marker because ninhydrin post-column derivatisation responds to the primary α-amino group regardless of enantiomeric configuration. Calibration solutions are prepared gravimetrically in lithium citrate buffer pH 2.20 at 0.5–2.0 μmol/mL using a five-place balance; 10 μL injections are made onto a cation-exchange column with sodium citrate step gradients and post-column ninhydrin detection at 570 nm for primary amines and 440 nm for proline. The material is sonicated for 10 min and filtered through 0.45 μm PTFE to prevent column frit blockage. Production of the reference mixture follows ISO 17034:2016 for reference material producers and testing under ISO/IEC 17025:2017; certificates of analysis report lot-specific purity by HPLC area percent and loss on drying not exceeding 0.5%. The addition ratio in system suitability kits is fixed at 1.0 μmol/mL for DL-lysine hydrochloride against histidine and arginine at the same concentration to bracket the basic amino acid retention window. Terminal finished product types include amino acid analyser system suitability kits, post-column derivatisation reagent sets, pharmacopoeial basic amino acid standard mixtures, and custom retention-time marker vials.
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Commercial product sold as DL-lysine hydrochloride (CAS 23335-24-0, C6H14N2O2·HCl, molar mass 182.65 g/mol) is the racemic monohydrochloride salt of 2,6-diaminohexanoic acid. Typical product designations include DL-Lys HCl 98% and DL-lysine monohydrochloride, technical grade. The material appears as a white to off-white crystalline powder with tapped bulk density commonly in the range 0.55–0.75 g/cm³ after fluidized-bed drying. Unlike L-lysine monohydrochloride (CAS 657-27-2), which is produced by fermentation and is optically active, DL-lysine hydrochloride contains an approximately equimolar mixture of D- and L-enantiomers; the specific optical rotation therefore remains close to zero under standard polarimetric conditions. The chloride counterion accounts for approximately 19.9% of molecular mass, while total lysine free base equivalence is approximately 80.0% by mass. Only the L-enantiomer fraction—about 40% of the salt mass—is generally recognized as metabolically equivalent to L-lysine in monogastric animal nutrition. This distinction changes effective dietary lysine loading when the racemate is evaluated against fermentation-derived L-lysine HCl.
In aqueous solution, the ionization behavior of DL-lysine hydrochloride is governed by three acid dissociation constants: the α-carboxyl pKa near 2.16, the α-amino pKa near 9.20, and the ε-amino pKa near 10.80. The hydrochloride salt therefore exists predominantly as a dicationic species below pH 2.0 and as a monocationic zwitterionic species between pH 4.0 and 8.0. This speciation affects buffer capacity and chloride release in liquid feed supplements and in electrolyte formulations. At a 10% aqueous concentration, the pH typically falls between 5.0 and 6.0, which is compatible with non-enzymatic browning controls in glucose-containing media but may require pH adjustment before autoclaving if residual carbohydrate content is high.
Direct kilogram-for-kilogram replacement is not valid in broiler or swine rations formulated on digestible lysine intake. A 98.5% L-lysine monohydrochloride feed grade delivers approximately 78.8% L-lysine free base by mass. A 98.5% DL-lysine hydrochloride at a theoretical 50:50 D:L ratio delivers approximately 39.4–40.0% L-lysine free base by mass, assuming the D-isomer does not contribute to net protein synthesis in monogastric species. In poultry and pig diets, the D-isomer has not been demonstrated to replace L-lysine on a digestible basis, and published data for the racemic hydrochloride salt at production-scale inclusion rates is limited. Formulation adjustment should therefore use the L-lysine mass fraction of the salt rather than the total lysine hydrochloride mass fraction. Verification by amino acid analysis should follow ISO 13903:2005 or AOAC Official Method 994.12, with an enantioselective method added where chiral composition is release-critical. For a broiler finisher diet formulated to 1.05% digestible lysine, replacing 10 kg of L-lysine HCl per tonne with approximately 20 kg of DL-lysine HCl may be required to maintain the same bioavailable L-lysine supply, but only if dietary electrolyte balance and chloride load allow. The additional chloride from 20 kg of racemic HCl is not negligible and should be included in dietary cation-anion difference calculations.
For dry-powder processing, moisture sensitivity and particle-size distribution impose measurable constraints. DL-lysine hydrochloride is hygroscopic and should be stored in closed containers at relative humidity below 60% to prevent caking and localized pH drift after moisture uptake. Pre-drying at 60–80°C for 4–6 hours under vacuum is used when the material is subsequently compounded into moisture-sensitive matrices, although published data for this specific configuration is limited. During twin-screw extrusion of feed pellets, addition rates above 5% by mass of racemic lysine salt may alter melt viscosity and expansion because chloride ions interact with starch-gluten networks. Pilot-scale runs should include torque and die-pressure monitoring on a corotating twin-screw extruder with an L/D ratio of at least 25:1, specific energy input in the range 0.10–0.20 kWh/kg, and a screw configuration containing two kneading blocks downstream of the feed port before production scale-up.
The limits below are representative commercial release boundaries for bulk DL-lysine hydrochloride. They are not pharmacopeial acceptance values for L-lysine hydrochloride, because the racemate is not the same substance described in the L-lysine monohydrochloride monograph.
| Parameter | Acceptance limit | Method basis |
|---|---|---|
| Assay (dry basis) | 98.0–101.0% | Titrimetric or HPLC |
| L-enantiomer fraction of total lysine | 49.0–51.0% | Chiral HPLC |
| Loss on drying | ≤0.5% | 105°C to constant weight; USP <731> |
| Residue on ignition | ≤0.3% | 550°C; USP <281> |
| pH (10% aqueous) | 5.0–6.0 | Potentiometric |
| Chloride | 19.4–20.1% | Argentometric |
| Lead | ≤5 mg/kg | ICP-MS after acid digestion |
| Arsenic | ≤1 mg/kg | Hydride atomic absorption |
| Bulk density | 0.55–0.75 g/cm³ | Tapped method |
| Residual solvents | ICH Q3C class-specific | GC headspace |
Quantitative assay by HPLC often employs pre-column derivatization with o-phthalaldehyde or 9-fluorenylmethyl chloroformate, followed by reversed-phase separation. Non-chiral derivatization reports total lysine; chiral derivatization with N-(5-fluoro-2,4-dinitrophenyl)-L-alaninamide or a similar enantioselective reagent can distinguish D and L peaks. The chiral method is necessary only if the application requires enantiomeric ratio control. When titration is used, a non-aqueous titration with perchloric acid in glacial acetic acid is common, but it cannot distinguish D and L forms.
Because DL-lysine hydrochloride is not identical to the L-lysine monohydrochloride described in current USP-NF or Ph. Eur. monographs, substitution in pharmaceutical formulations is not automatically acceptable. If a drug product or parenteral nutrition formulation requires L-lysine hydrochloride, the presence of D-lysine in racemic material is an identity failure, not a substitution parameter. Any pharmaceutical use must be supported by a dedicated specification or drug master file. In cell culture media, some certified lines and primary cells are sensitive to D-amino acid content; media manufacturers frequently require fermentation-derived L-lysine. The D-isomer may not support growth of L-lysine auxotrophic cells, although published data for the racemic hydrochloride salt at media-relevant concentrations is limited. When non-chiral use is claimed, standard ion-exchange chromatography with ninhydrin detection cannot distinguish DL-lysine from L-lysine; an enantioselective HPLC or GC-MS method should appear on the certificate of analysis.
For feed use, the regulatory status is not automatically inherited from L-lysine HCl. In the European Union, feed additives are registered under Regulation (EC) No 1831/2003; fermentation-derived L-lysine monohydrochloride appears in the feed additive register, while a synthetic racemic DL-lysine hydrochloride may require a separate safety and efficacy dossier before feed use. In the United States, a food additive petition or GRAS determination would be required for feed use unless the substance is already listed. The manufacturer’s batch documentation should therefore include the production route and chiral purity to allow regulatory review. In ruminant nutrition, the substitution calculus is different because rumen microbial protein can utilize non-protein nitrogen and D-amino acids to some extent, but published data for DL-lysine hydrochloride in protected-amino acid formulations is limited.
At the production scale, the salt is typically crystallized from an aqueous or aqueous-alcohol mother liquor, filtered, washed, and dried in a fluidized-bed dryer. Residual solvent levels are therefore a relevant release criterion in pharmaceutical-grade applications, with benzene, methanol, and isopropanol controlled to ICH Q3C limits. Incompatibilities exist with strong oxidizing agents, strong bases, and hypochlorite-based disinfectants; chloramine formation and effervescence can occur in wet processing lines. Avoid compounding the dry salt with amine-based additives in epoxy or polyurethane systems because the free amino groups can participate in premature crosslinking and exothermic reactions. Under sealed conditions with relative humidity kept below 60%, supplier-assigned shelf life commonly stands at 24 months; above 70% RH, surface caking can appear within 48–72 hours. These are operational boundaries, not regulatory guarantees, and actual stability should be confirmed with retain-sample testing.
For compound-feed purchasing, the economic comparison should be based on cost per kilogram of bioavailable L-lysine free base delivered to the mixer, not on delivered price per tonne of salt. Using the mass fractions above, 1.00 kg of 98.5% L-lysine HCl supplies approximately 0.79 kg L-lysine base, while 1.00 kg of 98.5% DL-lysine HCl supplies approximately 0.40 kg L-lysine base. The DL material must therefore be discounted by at least 50% on an equal-purity basis to match the bioavailable lysine economics of L-lysine HCl, before additional quality-control and reformulation costs are considered.
| Parameter | DL-lysine HCl | L-lysine HCl |
|---|---|---|
| CAS number | 23335-24-0 | 657-27-2 |
| Chiral composition | Racemic D:L 50:50 | L-enantiomer only |
| L-lysine free base fraction | ≈40% by mass | ≈78.8% by mass at 98.5% purity |
| Chloride counterion | ≈19.9% by mass | ≈19.9% by mass |
| Typical production route | Chemical synthesis | Fermentation |
| Monogastric bioavailable lysine | ≈40% L-lysine equivalent | ≈78.8% L-lysine equivalent |
| Feed authorization context | Verify against Regulation (EC) No 1831/2003 | Fermentation-derived L-lysine HCl generally registered |
Outside of animal nutrition, DL-lysine hydrochloride is used as a synthetic intermediate for racemic lysine derivatives, model polylysine substrates, and calibration solutions for total amino acid analysis. In these applications, chirality is not a critical functional property, and racemic composition can simplify method development because the detector response represents total lysine rather than an enantiomeric excess. For HPLC calibrators, the material should be dried before weighing to avoid moisture-induced assay drift. Working solutions prepared in 0.1 M hydrochloric acid should be prepared daily for quantitative work because published stability data for dilute aqueous DL-lysine hydrochloride is limited.
