What Is Distillation Grade?
Distillation grade reagents generally refer to products that, during manufacturing, undergo one or more stages of distillation or redistillation (fractional distillation / redistillation) to remove low-boiling and high-boiling impurities, moisture, and certain reactive impurities. The result is a reagent grade with higher purity, a more stable boiling range, and lower residual content.
The most common examples are organic solvent reagents (such as n-hexane, petroleum ether, dichloromethane, acetonitrile, etc.), although the term may also appear in the descriptions of certain organic intermediates or specialty monomers.
Distillation itself is a unit operation that separates mixture components based on differences in boiling point or relative volatility. By repeated vaporization and condensation in a distillation column, components can be enriched. For more complex systems, fractional distillation, extractive distillation, or vacuum distillation may be used to further enhance purity.
In systems such as water and phenols, the term redistilled is common. For example, redistilled water is obtained by distilling water twice, sometimes with additional treatment using oxidizing agents or bases to further remove volatile impurities and organic contaminants, thereby producing high-purity water.
In essence, distillation grade can be understood as a grade of high-purity solvents/reagents prepared via distillation or redistillation processes.
Origin of the Grade: Who Defines “Distillation Grade”?
Unlike AR/GR, which are standardized at the national level or by organizations such as the ACS, distillation grade is not a universally defined national or association grade. Instead, it mainly appears in:
1. Corporate standards, industrial standards, or internal quality standards;
2. Specific product lines, as a process-oriented grade used to highlight “high-quality solvents obtained through distillation.”
Why Do We Need Distillation Grade?
1. For Applications Sensitive to Solvent Impurities
(a) Industrial-grade or general CP solvents often contain relatively high levels of moisture, low-boiling impurities, high-boiling residues, and acidic/basic impurities.
(b) Precise organic synthesis, pharmaceutical intermediate production, fine chemicals, and certain analytical pretreatment steps are sensitive to these impurities, which can affect yield, selectivity, and the formation of side products.
2. Distillation Is a Mature and Scalable Purification Method
(a) Literature shows that the growing demand for high-purity solvents has led to widespread use of distillation-based purification in the chemical and pharmaceutical industries to improve solvent purity and optimize processes. Multistage distillation and vacuum distillation can significantly increase solvent purity.
3. Balancing “Cost vs. Quality”
(a) HPLC grade, LC-MS grade, pesticide-residue grade and other chromatography-dedicated solvents typically undergo more stringent processing such as glass distillation and 0.2 µm filtration, and are tightly controlled for UV absorbance, water content, non-volatile residue, fluorescent impurities, etc., which drives up cost.
(b) For many applications such as synthesis, extraction, cleaning, and crystallization, such stringent control over spectral background and trace impurities is not always necessary. High purity, a stable boiling range, and generally low impurity levels are often sufficient.
(c) Distillation grade therefore serves as an intermediate option between “general-purpose reagents” and “chromatography / mass spectrometry grades.”
Typical Test Items and Specifications for Distillation Grade Products
Based on an internal corporate quality standard and solvent quality specifications from various manufacturers, the following test items are commonly applied to distillation grade solvents:
1. Appearance and Color
(a) Appearance: Colorless or nearly colorless, clear liquid, free from visible mechanical/particulate impurities.
(b) Color: Typically measured using the APHA/Hazen (Pt–Co) color scale, e.g., ≤10 or ≤20.
2. Content / Assay
(a) Usually determined by gas chromatography (GC), titration, or other dedicated analytical methods.
3. Moisture
(a) Typically measured by Karl Fischer titration, with water content controlled to around 0.05–0.1% or lower.
4. Residue on Evaporation (Non-volatile Residue)
(a) For solvents used in coatings, films, electroplating, or analytical sample pretreatment, non-volatile residue is usually limited (for example, <0.001–0.01%). In HPLC grade solvent specifications, this parameter is directly related to column contamination and baseline interference.
5. Acidity/Alkalinity, Halides, Metal Ions, etc.
(a) Limits for acidity/alkalinity, halides (e.g., total chlorine), and metal ion content (e.g., heavy metals) may be defined according to the intended application of the product.
6. Physical Properties: Density, Refractive Index, Boiling Range, Viscosity, etc.
(a) Used to confirm the identity of the main component and to monitor batch-to-batch consistency; often included as supplementary items in quality inspection.
Typical Application Scenarios for Distillation Grade Products
1. Organic Synthesis and Fine Chemicals
(a) Used as reaction solvents or reactants, especially in reactions where selectivity and yield are sensitive to impurities (such as metal-catalyzed or stereoselective reactions).
(b) For example, distillation grade n-hexane can be used for extraction and organic synthesis, cleaning in the electronics industry, and as an extractant in pharmaceutical manufacturing.
2. Pharmaceuticals and Intermediate Production
(a) In scenarios involving extensive solvent recovery and reuse, processes are often combined with redistillation, or bulk distillation grade solvents are purchased directly to ensure consistent quality across batches.
3. Electronics, Coatings, and Adhesives Industries
(a) In formulations that are sensitive to metal ions or non-volatile residue, choosing distillation grade solvents helps reduce residue levels and the risk of ionic contamination.
4. Biology and Molecular Biology
(a) Redistilled phenol, redistilled water, etc., are used for nucleic acid extraction and buffer preparation, where systems are particularly sensitive to organic impurities and metal ions.
Representative Aladdin Distillation Grade Products and Application Examples
Aladdin offers distillation grade products in several categories, including organic ligands/catalytic reagents, organic bases and alkanolamines, aldehydes and oxygen-containing functional reagents, and high-purity metals. These products support applications ranging from synthesis and catalysis to materials science and microelectronics processing.
Product Category | Subcategory | Name | Aladdin Catalog No. | Specification / Purity | CAS No. | Distillation Grade Features |
Organic ligands / catalysis-related & specialty reagents | Diene ligands / monomeric organic ligands | 1,5-Cyclooctadiene | C485377 | Distillation grade, ≥99%, contains 50–150 ppm TBC stabilizer | 111-78-4 | A diene ligand prone to self-polymerization. The distillation grade product combines high purity with TBC stabilization to reduce polymerization and side reactions, making it suitable for metal complex preparation and fine organic synthesis. |
Organic ligands / catalysis-related & specialty reagents | ALD resist remover / specialty cleaner | ALD-374506 Resist Remover | Distillation grade, ≥99% (Total Diesters), low particle level | 95481-62-2 (ALD) | A dedicated resist remover for ALD/thin-film processes. The distillation grade ensures high total diester content and low particle counts, meeting stringent requirements for particulate and metal impurity control in microelectronics and wafer processing. | |
Organic ligands / catalysis-related & specialty reagents | Lewis acid complex | Boron Trifluoride Diethyl Etherate | Distillation grade, ≥46.5% BF₃ basis | 109-63-7 | A complex of the strong Lewis acid BF₃. The distillation grade product controls BF₃ content, moisture, and polymeric impurities, suitable for fine organic synthesis and acid-catalyzed reactions where precise reaction control is required. | |
Organic ligands / catalysis-related & specialty reagents | Superacid / catalyst | Fluoroantimonic Acid | F478475 | Distillation grade, triple-distillation | 16950-06-4 | Triple distillation reduces moisture and metallic/anionic impurities. Suitable for superacid catalysis, protonation studies, and specialized mechanistic experiments, showcasing Aladdin’s expertise in distillation control of highly corrosive reagents. |
Organic ligands / catalysis-related & specialty reagents | High-purity metal / trace-analysis metal | Barium | PrimorTrace™, distillation grade, ≥99.99% metals basis, dendritic pieces | 7440-39-3 | PrimorTrace™ high-purity barium metal with ≥99.99% metals basis and dendritic morphology offers low impurity background and high surface area, ideal for trace metal analysis, vacuum metallurgy, getter materials, and advanced materials research. | |
Organic bases, amines and alkanolamines/diamines | Heterocyclic organic base | 2,6-Lutidine | Distillation grade, ≥99% | 108-48-5 | A sterically hindered, weakly nucleophilic organic base. The distillation grade effectively reduces moisture and low-boiling amine impurities, suitable for impurity-sensitive selective deprotonation reactions and metal-catalyzed systems. | |
Organic bases, amines and alkanolamines/diamines | Tertiary amine base | N,N-Diisopropylethylamine (DIPEA) | Distillation grade, ≥99.5% | 7087-68-5 | A commonly used organic base for condensation, acylation, and coupling reactions. The distillation grade (≥99.5%) significantly reduces moisture and secondary amine by-components, improving reaction yields and batch-to-batch reproducibility. | |
Organic bases, amines and alkanolamines/diamines | Alkanolamine | N,N-Dimethylethanolamine (DMEA) | Distillation grade, ≥99.5% | 108-01-0 | An alkanolamine bearing both amine and hydroxyl groups, widely used for resin neutralization and as a wetting agent. The distillation grade increases main component content and reduces high-boiling residues and fusel alcohols, benefiting coatings, electrophoretic paints, and electronic chemical formulations. | |
Organic bases, amines and alkanolamines/diamines | Aromatic tertiary amine | N,N-Dimethylaniline | Distillation grade, ≥99.5% | 121-69-7 | An aromatic tertiary amine commonly used as an intermediate and accelerator. The distillation grade controls color and oxidative by-products on top of high purity, suitable for fine chemicals and photosensitive systems that are sensitive to color and side reactions. | |
Organic bases, amines and alkanolamines/diamines | Heterocyclic tertiary amine | N-Methylmorpholine | Distillation grade, ≥99.5% | 109-02-4 | A heterocyclic tertiary amine used as a basic catalyst and solvent. The distillation grade reduces water and low-boiling amine impurities, enhancing catalytic efficiency and process stability. | |
Organic bases, amines and alkanolamines/diamines | Diamine / chelating agent | Ethylenediamine (controlled explosive precursor) | E112643 | Distillation grade, ≥99.5% | 107-15-3 | A strongly basic diamine used as a chelating agent, crosslinker, and intermediate. The distillation grade lowers secondary amines and moisture, aiding in the preparation of stable complexes and high-purity intermediates while enabling controlled use under safety and regulatory requirements. |
Organic bases, amines and alkanolamines/diamines | Alkanolamine | Ethanolamine | Distillation grade, ≥99.5% | 141-43-5 | Used for gas absorption, corrosion inhibitors, and as a surfactant precursor. The distillation grade ensures high purity and low color, improving stability in gas purification and fine chemical formulations. | |
Organic bases, amines and alkanolamines/diamines | Secondary amine base | Diethylamine | Distillation grade, ≥99.5% | 109-89-7 | An important organic base and intermediate. The distillation grade controls low-boiling impurities and residual solvents, improving control over selectivity and yield in fine organic synthesis. | |
Organic bases, amines and alkanolamines/diamines | Tertiary amine | tert-Butylamine | Distillation grade, ≥99.5% | 75-64-9 | A sterically hindered tertiary amine widely used in the synthesis of quaternary ammonium salts and pharmaceutical intermediates. The distillation grade reduces moisture and amine by-products, helping to improve reaction yields and final product color. | |
Organic bases, amines and alkanolamines/diamines | Heterocyclic amine | Morpholine | Distillation grade, ≥99.5% | 110-91-8 | A heterocyclic amine used as a solvent, rubber accelerator, and agrochemical intermediate. The distillation grade increases purity and controls corrosive impurities, providing a milder profile for downstream synthesis and formulation systems. | |
Organic bases, amines and alkanolamines/diamines | Diamine / polymerization catalyst | N,N,N′,N′-Tetramethylethylenediamine (TEMED) | Distillation grade, ≥99.5% (GC) | 110-18-9 | Commonly used for acrylamide gel polymerization (e.g., PAGE). The distillation grade (≥99.5% GC) minimizes inhibitors, moisture, and by-products, enhancing gel polymerization rate and reproducibility. | |
Aldehydes and oxygen-containing functional reagents | Low-carbon aliphatic aldehyde | Isobutyraldehyde | Distillation grade, ≥99.5% | 78-84-2 | A low-carbon aliphatic aldehyde prone to oxidation and condensation. The distillation grade reduces acidity and high-boiling condensation products, making it suitable for the synthesis of high-end fragrances, pharmaceuticals, and agrochemical intermediates. | |
Aldehydes and oxygen-containing functional reagents | Low-carbon aliphatic aldehyde | n-Butyraldehyde | Distillation grade, ≥99.5% | 123-72-8 | Used in the preparation of butanol, resins, and fine chemical intermediates. The distillation grade ensures high purity and a stable boiling range, reducing color and impurity issues caused by resinification by-products. | |
Aldehydes and oxygen-containing functional reagents | Aromatic aldehyde / ligand precursor | Salicylaldehyde | Distillation grade | 90-02-8 | A hydroxy aromatic aldehyde used in Schiff base ligands and fragrances. The distillation grade helps control carboxylic oxidation products and color, improving the purity and appearance of Schiff bases and metal complexes. | |
Aldehydes and oxygen-containing functional reagents | Borate ester reagent | Trimethyl Borate | Distillation grade, ≥99.5% (GC) | 121-43-7 | An important boron source and organic synthesis reagent prone to hydrolysis. The distillation grade (≥99.5% GC) reduces free methanol and moisture, making it suitable for moisture-sensitive organoboron reactions and cross-coupling processes. | |
Aldehydes and oxygen-containing functional reagents | Aromatic aldehyde | Benzaldehyde | B110464 | Distillation grade, ≥99.5% | 100-52-7 | An aromatic aldehyde that readily oxidizes to benzoic acid and undergoes resinification. The distillation grade reduces acidity and polymeric by-products, supporting high-quality production of fragrances, pharmaceutical intermediates, and aromatic ligands. |
Note: Some distillation grade products (such as ethylenediamine, fluoroantimonic acid, and barium metal) exhibit high-hazard characteristics such as flammability, strong corrosivity, or inclusion in regulatory lists of explosive precursor hazardous chemicals. They must be used strictly in accordance with applicable laws, regulations, and laboratory safety guidelines, and only by properly trained personnel under compliant conditions.
Comparison Between Common Reagent Grades and Distillation Grade
Grade | Primary Control Focus | Typical Applications | Relationship to Distillation Grade and Trade-offs |
Industrial / Technical Grade | Cost and bulk physical properties; purity and impurity limits are relatively loose | Bulk chemicals, cleaning, rough or preliminary processing | Clearly lower than distillation grade: not recommended for fine synthesis or demanding experiments unless the user performs their own additional distillation. |
CP (Chemically Pure) | Basic assay requirement; limited limits set on a small number of impurities | Teaching labs, general organic synthesis | Generally regarded as “basic laboratory grade.” Distillation grade is overall superior to CP in terms of moisture control, boiling range, residue, and batch consistency, and is better suited to processes with moderate sensitivity. |
AR / GR (Analytical Reagent / Guaranteed Reagent) | Emphasis on assay and limits for acidity and metallic impurities to support analytical reliability | Titration, routine analysis, high-precision research | More oriented toward analytical requirements; distillation grade is more oriented toward reaction/process requirements. For analytical work choose AR/GR; for synthesis, extraction, and process stability, distillation grade is often preferable. |
Distillation Grade | One or more distillation steps; targeted control of moisture, low-/high-boiling impurities, boiling range, and residue; purity can range from ≥97% to ≥99.9% | Organic synthesis, extraction, crystallization, pretreatment, electronics and coating formulations, certain catalytic systems | A balanced option between “general-purpose reagents” and “specialized high-end grades (e.g., HPLC).” Within a manageable cost, it focuses on reducing key impurities that impact reactions and processes. |
In addition to high purity, strict control of UV absorbance, fluorescent impurities, and non-volatile residue; typically also subjected to fine filtration | Chromatographic mobile phases, trace analysis | When the solvent is used directly as a mobile phase or injected onto instruments, chromatography grade should be preferred. For synthesis, pretreatment, or bulk processes, distillation grade is usually the more economical choice. | |
Control of RNase/DNase, endotoxins, organic solvent residues, etc. | Nucleic acid/protein workflows, cell-based experiments | Distillation grade solvents/reagents cannot directly replace molecular biology grade; they are suitable only as precursors or for pretreatment. For actual molecular biology experiments, dedicated biological grades are still required. |
Notes:
1. Distillation grade is not a “universal highest grade,” but an optimized grade that focuses on distillation processes and control of key impurities.
2. For users primarily “running reactions or processes,” distillation grade is often more aligned with real-world needs than AR/GR.
3. For users doing “chromatographic analysis,” HPLC/GC grade solvents should be given priority.
Frequently Asked Questions
Q1: Which is “better,” distillation grade or analytical reagent (AR)?
(a) AR is a grade designed for analytical use, with relatively systematic specifications for assay and impurity limits.
(b) Distillation grade is a grade designed around process and application, emphasizing “high purity and stable physical properties achieved through distillation.”
(c) For some solvents, the assay of a distillation grade product may be higher than that of certain AR solvents, or slightly lower. Which one is “better” depends on whether you prioritize analytical background levels or process compatibility and cost.
Q2: Can distillation grade be used directly as HPLC solvent?
It is not recommended to assume so by default.
(a) Distillation grade focuses on purity and general impurity control.
(b) HPLC grade, on the other hand, imposes stricter limits on UV absorbance, fluorescent impurities, and non-volatile residue, and many such solvents are produced by glass distillation combined with sub-micron filtration.
If the solvent is used only for crude sample preparation or pre-column processing, distillation grade is usually acceptable. However, for use as the chromatographic mobile phase, dedicated HPLC/GC/LC-MS grade solvents are strongly recommended.
Q3: What is the difference between distillation grade and “redistilled”?
(a) “Redistilled” refers primarily to the process step, as in “redistilled water” or “redistilled phenol,” meaning the material has undergone two or more distillations.
(b) “Distillation grade” is a product grade concept, usually implying that the production process includes at least one distillation/redistillation step and is accompanied by defined specifications for assay and impurity control.
In many cases, products labeled as redistilled can broadly be regarded as “distillation-type products,” but whether they are explicitly labeled “distillation grade” depends on how the manufacturer defines its grades.
Q4: Is distillation grade purity always ≥99.9%?
No.
(a) Some high-demand distillation grade solvents do reach ≥99.9%.
(b) Other distillation grade products may have purity of only ≥97%; their advantages lie more in control of boiling range, impurity profile, and batch consistency than in a single “percent assay” figure.
Distillation grade does not equate to a uniform 99.9%; the actual specification should be confirmed from each product’s COA.
Q5: In industrial practice, does “petroleum distillate / distillate” mean the same as distillation grade?
Not exactly.
(a) In the petroleum industry, “distillates” are often fractions categorized by boiling range and physical properties rather than high-purity reagents. They are commonly used as base oils or solvent oils and focus on properties such as flash point, density, and boiling range, rather than chemical purity.
(b) Distillation grade reagents, in contrast, place greater emphasis on chemical purity and impurity content control.