What Grade Is Purum? From Grade Meaning and Specification Interpretation to Reagent Selection

Introduction

Labels such as “purum,” “puriss.,” and “p.a.” are frequently seen on chemical reagent labels and in product catalogs. Purum is commonly translated as “pure” or “pure grade,” but it is not a standardized grade that is uniformly applied across suppliers or associated with a fixed purity percentage.

Actual products may be labeled as “bilirubin, purum, ≥95.0%,” “dihydrocarvone, purum, ≥98.0%,” “zinc powder, purum, ≥99%,” or “sodium hydroxide solution, purum, ≥32%.” The values of 95%, 98%, 99%, and 32% in these examples refer to different product forms, analytical methods, and assay bases. Therefore, a uniform purity level cannot be inferred from the Purum designation alone.

The key to understanding Purum is to answer three questions:

What information does Purum provide? Which parameters are controlled for the specific product? Do those parameters meet the experimental requirements?

1 What Grade Is Purum?

1.1 Basic Meaning of Purum

Purum is a traditional Latin quality designation for chemical reagents, with the basic meaning of “pure.” In chemical reagent catalogs, it generally indicates that a product has undergone a certain degree of purification and quality control and has a principal-component assay, concentration, or other quality parameters specified by the supplier.

Purum describes the quality positioning of a product rather than a category of chemical structure. It may be used for organic synthesis reagents, inorganic salts, acid and base solutions, metal powders, reducing agents, oxidizing agents, coupling reagents, and other laboratory chemicals.

In some traditional nomenclature systems, techn. or technical, purum, and puriss. are used to indicate technical grade, pure grade, and a higher-purity grade, respectively. The abbreviation p.a. is derived from the Latin term “pro analysi,” meaning “for analysis.” These general grade designations do not have universally mandatory definitions, and manufacturers may establish specific specifications according to the product and its intended use. Therefore, products from different suppliers should not be compared solely on the basis of grade names.

1.2 Why Does Purum Not Correspond to a Fixed Purity Percentage?

Because products differ in composition, analytical method, and controllable impurities, assay specifications for Purum products vary from one product to another.

For example:

① Bilirubin may be labeled as purum, ≥95.0%, with the assay determined by ultraviolet spectrophotometry;

② Dihydrocarvone may be labeled as purum, ≥98.0%, with the total isomer content determined by gas chromatography;

③ Zinc powder may be labeled as purum, ≥99%, with additional limits specified for impurities such as arsenic, cadmium, iron, lead, and tin;

④ Sodium hydroxide solution may be labeled as purum, ≥32%, where 32% refers to the effective sodium hydroxide content in the solution rather than the purity of solid sodium hydroxide.

These examples demonstrate that Purum is not a fixed synonym for “≥95%,” “≥97%,” or “≥99%.” After identifying a product as Purum, it is still necessary to examine the assay value, analytical method, calculation basis, and impurity limits.

1.3 What Information Can Purum Provide?

Purum Can Generally Provide a Preliminary Indication That	Purum Alone Cannot Be Used to Determine That
The product has been classified by the supplier within a “pure-grade” quality category	All Purum products have the same minimum purity
The product has a specified principal-component assay, concentration, or activity value	The product necessarily complies with American Chemical Society, pharmacopoeial, or other external standards
The product has undergone quality testing corresponding to the specifications of that catalog number	The product is necessarily anhydrous, metal-free, stabilizer-free, or free of specific ions
Product specifications or batch analysis documents are generally available	The product is necessarily suitable for chromatography, mass spectrometry, trace analysis, or biological experiments
The product may be suitable for general synthesis, preparation, or routine experiments	The product can be used as a quantitative analytical standard or certified reference material

1.4 Can Purum Be Directly Equated with Chemically Pure Grade?

In linguistic terms, Purum is relatively close to “pure” or chemically pure (CP), and some reagent-grade references list purum alongside chemically pure.

However, the two should not be treated as directly equivalent without first reviewing the specifications. The reasons include:

1. Different countries, suppliers, and product lines may use different grade definitions;

2. The lower limit for the principal-component assay may differ;

3. The test items for water, heavy metals, anions, and related substances may differ;

4. The analytical methods and assay calculation bases may differ.

Therefore, when replacing a product across brands, comparing the names “purum” and “chemically pure” has limited value. A more reliable approach is to compare the product specifications item by item.

2 How Should the Quality Specifications of a Purum Product Be Interpreted?

2.1 Examine the Principal-Component Assay First, Followed by the Analytical Method and Calculation Basis

The principal-component assay of a Purum product may be expressed using different methods. Common forms include:

· ≥98.0%, gas chromatography (GC);

· ≥98.0%, high-performance liquid chromatography (HPLC);

· ≥98.0%, titration;

· ≥98.0%, calculated on a dried basis;

· ≥99.0%, calculated on a metal basis;

· Approximately 30% or 32% active ingredient in solution;

· Approximately 1.0 mol/L solution concentration.

An assay value provides complete quality information only when interpreted together with the analytical method and calculation basis.

For example, “≥98% (GC)” mainly reflects the relative composition of the components detectable by the chromatographic method; “≥98% (titration)” reflects the effective component capable of participating in titration according to the specified stoichiometric relationship; and “≥98% (dry basis)” indicates that the content is calculated after deducting water or volatile matter.

If a product is labeled “total isomer content ≥98%,” the value may represent the sum of several isomers and does not mean that any individual isomer, enantiomer, or diastereomer reaches 98%. A Purum-grade dihydrocarvone product labeled “total isomer content, GC” is a typical example of this situation.

2.2 What Test Parameters Are Commonly Included for Purum Products?

The testing priorities differ among product categories. The following table lists typical parameters that may be included; it is not a uniform checklist applied to all Purum products.

Product Type	Common Methods for Principal-Component Testing	Possible Additional Test Parameters	Main Quality Significance
Organic liquids	GC, HPLC, titration	Water, density, refractive index, color, nonvolatile residue, stabilizer	Evaluation of principal-component composition, volatile impurities, and storage stability
Organic solids	HPLC, titration, elemental content	Water, loss on drying, melting point, residue on ignition, related substances	Evaluation of principal component, residual inorganic matter, and solid-state condition
Inorganic salts	Titration, gravimetric analysis, elemental analysis	Insoluble matter, chloride, sulfate, iron, heavy metals, pH	Evaluation of effective component and ionic impurity background
Acids, bases, and their solutions	Acid–base titration, redox titration	Density, carbonate, chloride, sulfate, metal impurities	Evaluation of effective concentration and impurities that may affect reactions or analyses
Metals and reactive solids	Elemental content, metal-basis assay	Other metal impurities, particle size, powder or granular form	Evaluation of chemical composition, surface reactivity, and reaction reproducibility

For example, in addition to a zinc content of ≥99%, a Purum-grade zinc powder product may also specify limits for arsenic, cadmium, iron, lead, and tin. A Purum-grade sodium hydroxide solution may specify not only an effective content of ≥32%, but also limits for iron, chloride, total sulfur expressed as sulfate, and heavy metals.

These examples show that Purum products may include control of multiple impurities, but the scope of control is still determined by the specific catalog number.

2.3 Why Is Principal-Component Assay Not the Only Criterion?

The effect of a reagent on an experimental result often depends on one or more critical impurities rather than solely on the total assay.

1. Water

Water may affect organometallic reagents, strong bases, acid chlorides, silylation reagents, polymerization reactions, and moisture-sensitive catalytic systems. A product with a high principal-component assay but no specified water limit may not be suitable for strictly anhydrous reactions.

2. Metal Impurities

Metals such as iron, copper, nickel, and lead may participate in redox reactions, catalyze side reactions, or affect the optical, electrical, and polymerization properties of materials. For metal-sensitive reactions, specific metal limits are more informative than the overall purity value.

3. Anionic and Acidic or Basic Impurities

Chloride, sulfate, phosphate, carbonate, and free acids or bases may affect precipitation reactions, coordination reactions, catalyst stability, and analytical background.

4. Isomers and Related Substances

A product with a high total assay may still contain positional isomers, geometric isomers, enantiomers, unreacted starting materials, or structurally similar by-products. For stereoselective reactions and quantitative analyses, the specifications for related substances or individual isomers should be examined.

5. Stabilizers and Inhibitors

Antioxidants or polymerization inhibitors may be added to ethers, alkenes, monomers, and readily polymerizable reagents. Stabilizers support storage stability and safety, but they may also affect free-radical polymerization, metal catalysis, photochemical reactions, or highly sensitive analyses.

Therefore, reagent selection should not be based solely on comparing “98%” with “99%.” If an experiment is sensitive to water or metals, a specialized product with clearly controlled critical impurities may be more suitable than a product with a nominally higher total assay but no corresponding impurity limits.

2.4 What Information Is Provided by a Product Specification, CoA, and SDS?

Product specifications, Certificates of Analysis, and Safety Data Sheets serve different functions and cannot substitute for one another.

Document	English Name and Abbreviation	Main Content	Use in Product Selection
Product specification	Product Specification	Specifies the test parameters, limits, and release requirements for the catalog number	Determines which parameters are theoretically controlled for the product
Batch analysis certificate	Certificate of Analysis, CoA	Provides measured results or compliance status for a specific batch	Determines whether the batch in hand meets the requirements
Safety data sheet	Safety Data Sheet, SDS	Hazard classification, protective measures, storage, spill response, and disposal	Determines safe handling conditions; not a complete proof of purity

Supplier CoA searches generally require a product number and batch number, indicating that the CoA is associated with a specific production batch. The primary role of the SDS is to support safe handling and hazard management.

When reading a CoA, it should also be noted that some parameters are reported as measured batch values, whereas others are listed only as “complies” or “passes.” If a particular impurity directly affects the experiment, products that provide explicit limits and batch-specific data should be prioritized.

3 How Is Purum Related to Other Reagent Grades?

Designations within the same traditional quality nomenclature system as Purum mainly include technical or techn. and puriss. The designation p.a. is closer to an analytical-use designation and may be combined with purum or puriss.

Grade or Designation	Core Meaning	Relationship to Purum
technical, techn.	Technical-grade or industrial-use quality	Traditionally considered lower than purum, although the actual quality is still determined by the supplier’s specifications
purum	Pure grade	Indicates the basic purity and quality category established by the supplier
puriss., purissimum	Higher-purity grade	Traditionally subject to stricter control than purum, but without a fixed content requirement uniformly applied across suppliers
p.a., pro analysi	For analysis	An analytical-use designation that may appear in combinations such as purum p.a. or puriss. p.a.
ACS Reagent	Complies with American Chemical Society reagent specifications	Assay, impurity limits, and analytical methods are specified in the monograph for the individual chemical
HPLC grade	For high-performance liquid chromatography	Emphasizes control of ultraviolet absorbance, particles, gradient background, and nonvolatile residue
LC–MS grade	For liquid chromatography–mass spectrometry	Emphasizes low ionic background, low nonvolatile residue, low adduct formation, and impurities associated with ion suppression
Anhydrous or low-water grade	Controls water content	Intended for moisture-sensitive reactions; does not imply that all other impurities are low
Trace-metal analysis grade	Controls elemental impurities	Used for low-concentration elemental analysis and sample preparation
Biology-specific grade	Controls specific biological contamination or functional parameters	May address nucleases, proteases, endotoxins, sterility, or suitability for cell-based applications
Analytical standards and reference materials	Used for identification, quantitation, or calibration	Have dedicated value assignment, identification, or traceability information and cannot be directly replaced by ordinary Purum reagents

The American Chemical Society (ACS) establishes purity specifications and analytical methods through reagent-specific monographs. Therefore, ACS Reagent does not represent a uniform percentage and should not be understood simply as “one grade higher than Purum.”

Liquid chromatography–mass spectrometry (LC–MS)-grade solvents emphasize low ionic background, low nonvolatile residue, baseline stability, and suitability for mass spectrometry. These use-specific parameters cannot be inferred automatically from a Purum label.

Analytical standards, certified reference materials (CRMs), and ordinary research reagents also belong to different quality categories. Research-grade chemicals may be supplied with a CoA, but they may not have been fully characterized for use as reference materials and cannot be used directly as calibration standards solely on the basis of the CoA.

4 When Is It Appropriate to Select Purum-Grade Reagents?

4.1 For Which Typical Experiments Is Purum Suitable?

Provided that the specific specifications meet the experimental requirements, Purum may generally be considered for the following applications:

Experimental Scenario	Suitability of Purum	Parameters Requiring Particular Attention
General organic synthesis	Generally suitable as a candidate grade	Principal-component assay, water, stabilizers, isomers, metal impurities
General inorganic reactions	Generally suitable as a candidate grade	Effective content, insoluble matter, chloride, sulfate, and metals
Preliminary screening of reaction conditions	May be considered when the experiment is not sensitive to trace impurities	Batch consistency and critical impurities
Teaching experiments and routine preparation	Generally suitable when precise quantitation is not involved	Effective content, appearance, and storage condition
Excess acids, bases, or work-up reagents	May be considered when the specifications are sufficient for the reaction and subsequent purification	Actual concentration, carbonate, metals, and insoluble matter
Synthesis followed by recrystallization or column chromatography	May be considered when starting impurities can be removed during work-up	Whether difficult-to-separate by-products or catalyst poisons are introduced
General materials preparation	May be considered when material properties are not sensitive to trace impurities	Metals, ions, water, and particle size

It should be noted that “suitable for general synthesis” does not mean that all Purum products are suitable for the same reaction. For example, moisture-sensitive reactions still require confirmation of water content; noble-metal-catalyzed reactions still require attention to sulfur, phosphorus, halide ions, and other impurities that may deactivate the catalyst; and free-radical polymerization requires confirmation of the type and content of polymerization inhibitors.

4.2 For Which Experiments Is Purum Alone Insufficient for Product Selection?

The following experiments generally require products with clearly defined application-specific specifications. The Purum label alone is insufficient for making a selection.

1. Quantitative Instrumental Analysis

High-performance liquid chromatography, LC–MS, and other highly sensitive instrumental analyses require control of baseline quality, particles, nonvolatile residue, ultraviolet absorbance, and ionization interference. Solvents and reagents that have been tested for suitability with the corresponding instrument should be selected for these applications.

2. Trace Element Analysis

Trace-analysis techniques such as inductively coupled plasma mass spectrometry (ICP–MS) are highly sensitive to elemental backgrounds in acids, bases, and sample-preparation reagents. In such cases, the actual limits for individual elements must be examined rather than relying only on total purity or the Purum designation. Specialized high-purity acids and bases control impurity backgrounds for low-concentration elemental analysis.

3. Quantitative Standards and Instrument Calibration

Materials used for calibration curves, content assignment, method validation, and instrument calibration should be analytical standards, reference materials, or certified reference materials appropriate for the analytical purpose. Even when a Purum reagent has a high principal-component assay, it is not equivalent to a reference material with specified traceability and uncertainty information.

4. Strictly Anhydrous or Impurity-Sensitive Reactions

Organolithium reagents, Grignard reagents, low-valent metal catalysis, certain polymerization processes, and battery-material experiments may be highly sensitive to water, oxygen, metals, halide ions, or peroxides. Products with clearly specified limits for these parameters, such as anhydrous, low-oxygen, or specialized reaction grades, should be selected.

5. Biological Experiments and Regulated Uses

Cell culture, enzymology, protein, nucleic acid, and microbiological experiments may require control of endotoxins, nucleases, proteases, sterility, or cytotoxicity. Pharmaceutical, food, and other regulated applications must also comply with the corresponding pharmacopoeial, regulatory, or quality-document requirements. Purum itself does not provide such assurances.

5 How Can You Determine Whether Purum Meets the Requirements of Your Experiment?

The determination can be made by answering the following four questions.

1. What Role Does the Reagent Play in the Experiment?

Reaction substrates, catalysts, solvents, acid–base reagents, work-up reagents, and quantitative standards have different quality requirements.

Structurally similar impurities in a substrate may enter the final product; water and ligand impurities in a catalyst may alter catalytic activity; small amounts of impurities in work-up reagents may be removed during washing or purification.

2. Which Impurities Could Alter the Experimental Results?

Critical impurities should be identified according to the reaction mechanism and analytical method. For example:

① Will water consume the active reagent?

② Will metals catalyze side reactions?

③ Will chloride ions or sulfur deactivate the catalyst?

④ Will stabilizers inhibit polymerization?

⑤ Will isomers enter the target product?

⑥ Will nonvolatile residues contaminate the chromatography or mass spectrometry system?

3. Do the Product Specifications Cover These Impurities?

If an experiment is sensitive to water but the product specification contains no water parameter, suitability cannot be confirmed solely from a high principal-component assay. If the experiment is sensitive to iron or copper, the corresponding elemental limits should be examined rather than relying only on “purum” or “99%.”

4. Does the Specific Batch Meet the Requirements?

For experiments with high reproducibility requirements, the CoA may be reviewed further, and the supplier, catalog number, batch number, date of opening, and key measured values may be recorded. For sensitive reactions or products obtained from a new supplier, small-scale verification can help determine whether changes in batch or specification affect the results.

6 What Else Should Be Considered When Selecting and Using Purum Products?

1. Quality May Change After Opening

A CoA reflects the condition of a specific batch at the time of testing or release. Hygroscopic products may absorb water, strong bases may absorb carbon dioxide, readily oxidized products may form peroxides or oxidation by-products, and volatile solutions may change concentration because of solvent loss.

2. Distinguish Pure-Substance Assay from Solution Concentration

“Sodium hydroxide solution, purum, ≥32%” means that the solution contains at least 32% effective sodium hydroxide; it does not mean that the product has a quality grade of only 32%.

Similarly, “20% aqueous solution,” “1.0 mol/L solution,” and “anhydrous solid” describe product composition in terms of mass fraction, amount-of-substance concentration, and solid chemical form, respectively. Because the actual active-component content differs among products, replacement quantities should be recalculated according to the mass or amount of substance of the active component required by the experiment.

3. Pay Attention to Anhydrous Forms, Hydrates, and Calculation Bases

The same inorganic salt may exist as an anhydrous compound, monohydrate, dihydrate, or other hydrate. Hydrates contain a defined amount of water of crystallization and therefore have different chemical formulas and molar masses from the corresponding anhydrous compounds.

When preparing a solution, first confirm whether the product is an anhydrous compound or a hydrate, and then calculate the required mass according to its actual chemical formula and molar mass. If an anhydrous compound is replaced with a hydrate, or a hydrate with an anhydrous compound, the quantity must be recalculated rather than using the original weighed mass.

Product specifications may also state assay calculation bases such as “on a dried basis,” “on an anhydrous basis,” “on a metal basis,” or “on an active-component basis.” If the product assay is below 100%, the quantity weighed should also be corrected according to the labeled assay or batch analysis result so that the actual amount of active component added meets the experimental requirement.

4. Do Not Ignore Stabilizers

If a product contains polymerization inhibitors, antioxidants, or other stabilizers, their possible effects on the reaction should be evaluated. Removing a stabilizer may reduce storage stability or increase operational risks and should therefore be handled in accordance with the experimental method and safety requirements.

5. Purum Is Not a Safety Grade

Purum describes the quality and purity positioning of a product. It does not indicate lower toxicity, reduced corrosiveness, or reduced need for personal protection. Before use, the SDS should still be consulted to determine requirements for ventilation, protective equipment, storage, spill response, and waste disposal.

7 Summary

Purum generally indicates a “pure-grade” quality category for chemical reagents, but it is not a standard uniformly applied across suppliers and does not correspond to a fixed purity percentage.

To determine whether a Purum product is suitable, the following information should be considered together:

1. Principal-component assay or effective concentration;

2. Analytical method and assay calculation basis;

3. Critical parameters such as water, metals, ions, isomers, and stabilizers;

4. Product specifications and the CoA for the specific batch;

5. Experimental requirements relating to specific impurities and application performance.

Purum may be considered as a candidate grade for general synthesis, preparation, and routine experiments, but it cannot automatically replace analytical grade, chromatography grade, mass spectrometry grade, trace-analysis grade, biology-specific grade, or reference materials.

When selecting a Purum product, the key question is not how high the grade name appears to be, but whether the parameters controlled for the product cover the impurities that may affect the experimental results.

Representative Purum and Purum p.a. Products and Their Research Applications

Note: The following products are classified according to their typical experimental roles and include both Purum and purum p.a. products. The products differ in assay, analytical method, product form, and additional use-related designations. Product selection should therefore be based on the specific specifications, batch Certificate of Analysis, and experimental requirements for water, metals, ions, and other critical impurities.

Table 1 Purum Organic Synthesis Building Blocks, Protected Derivatives, and Specialized Reaction Reagents

Classification	CAS No.	Aladdin Catalog No.	Name	Specification or Purity	Product Features and Research Applications
Phosphazene base-related salt	—	T475731	2-tert-Butylamino-1-methyl-2-[tris(dimethylamino)phosphoranylidenamino]-perhydro-1,3,2-diazaphosphorinium iodide	purum, ≥97.0% (CHN)	Used in the preparation of strong phosphazene bases and in studies of strong-base-mediated deprotonation, nucleophilic reactions, and base-catalyzed reaction conditions.
Protected thienyl amino acid building block	331730-13-3	B475726	Boc-β-(3-thienyl)-Ala-OH dicyclohexylammonium salt	purum, ≥98% (TLC)	Used for introducing thienyl-containing non-natural amino acids, peptide-chain elongation, amide coupling, and structure–activity relationship studies.
Hydroxyanthraquinone intermediate	81-64-1	D475743	1,4-Dihydroxyanthraquinone	purum, ≥98% (HPLC), powder, red-brown	Used in studies of anthraquinone dyes, coordination compounds, redox systems, and photophysical properties.
Protected arginine derivative	1217450-12-8	N475722	Nω-(4-Methoxy-2,3,6-trimethylbenzenesulfonyl)-L-arginine 4-methoxybenzylamide hydrochloride	purum, ≥98% (HPLC)	Used in studies of arginine side-chain protection, peptide-fragment synthesis, deprotection conditions, and argininamide derivatives.
Fmoc-protected cyclic amino acid	194471-85-7	C475723	cis-2-(Fmoc-amino)cyclohexanecarboxylic acid	purum, ≥98% (HPLC)	Used for introducing cyclic non-natural amino acids and in solid-phase peptide synthesis, amide coupling, and conformationally constrained peptide studies.
Allyl sulfone synthesis building block	16212-05-8	A475742	Allyl phenyl sulfone	purum, ≥98% (GC)	Used in sulfone carbanion reactions, allylic functionalization, carbon–carbon bond formation, and the synthesis of sulfone-containing intermediates.
Chiral bornylamine building block	32511-34-5	R475718	(R)-(+)-Bornylamine	purum, ≥97% (NT)	Used in studies of chiral amine derivatives, asymmetric synthesis auxiliaries, chiral ligands, and resolving agents.
Boc-protected piperazine carboxylic acid	868151-70-6	B475715	2-(4-Boc-piperazinyl)-2-(4-fluorophenyl)acetic acid	purum, ≥97% (HPLC)	Used in the construction of p-fluorophenylpiperazine scaffolds, amide coupling, deprotection, and the synthesis of medicinal chemistry intermediates.
Hydroxamate-based amination reagent precursor	38202-27-6	E475716	Ethyl O-(2-mesitylenesulfonyl)acetohydroxamate	purum, ≥97% (HPLC)	Used in the preparation of electrophilic amination reagents and in studies of nitrogen-containing bond formation and amination reaction conditions.
Morpholinyl alkylating reagent	3647-69-6	C475733	4-(2-Chloroethyl)morpholine hydrochloride	purum, ≥97% (AT)	Used for introducing morpholinoethyl side chains and in nucleophilic substitution, quaternary ammonium derivative, and medicinal chemistry intermediate synthesis.
Boc-protected piperazine carboxylic acid	444892-80-2	B475714	2-(4-Boc-piperazinyl)-2-(2-fluorophenyl)acetic acid	purum, ≥97%	Used in the construction of o-fluorophenylpiperazine scaffolds, amide coupling, deprotection, and the synthesis of medicinal chemistry intermediates.
Boc-protected piperazine ester building block	890090-44-5	M475711	Methyl 2-(4-Boc-piperazinyl)-2-(2-pyridyl)acetate	purum, ≥95% (HPLC)	Used in the construction of pyridylpiperazine scaffolds and in ester hydrolysis, amide coupling, deprotection, and medicinal chemistry intermediate synthesis.
Chlorophenol synthesis intermediate	95-95-4	T434610	2,4,5-Trichlorophenol	purum, ≥95% (GC)	Used in the synthesis of chlorinated aromatic compounds and in studies of phenolic hydroxyl derivatization, chlorophenol reactivity, and environmental degradation.

Table 2 Purum Functional Organic Compounds, Metals, Alloys, and Inorganic Materials

Classification	CAS No.	Aladdin Catalog No.	Name	Specification or Purity	Product Features and Research Applications
Photographic developing agent	55-55-0	M432902	Metol	photographic grade, purum, ≥98% (HPLC)	Used in silver-halide photographic development and in studies of redox reactions, developer formulations, and development kinetics.
Metallic zinc reducing agent	7440-66-6	Z433466	Zinc (explosives precursor)	purum, powder	Used in metal reduction, organozinc reagent preparation, displacement reactions, and studies of zinc surface reactions.
Aluminum–nickel alloy catalyst-material precursor	12635-27-7	A431664	Aluminum–nickel alloy	purum, 50% Al basis, 50% Ni basis	Used in the preparation of porous nickel catalytic materials and in studies of hydrogenation, dehydrogenation, alloy leaching, and catalytic performance.
Ferric salt solution	7705-08-0	I433834	Iron(III) chloride solution	purum, 45% FeCl₃ basis	Used in Lewis acid catalysis and oxidation reactions under aqueous conditions, iron-salt material preparation, metal etching, and studies of hydrolysis behavior.
Hindered phenolic antioxidant	128-37-0	D431699	2,6-Di-tert-butyl-p-cresol (BHT)	purum, ≥99% (GC)	Used in studies of free-radical inhibition, oxidative stability of oils and polymers, thermo-oxidative aging, and antioxidant formulations.
Long-chain alkyl aromatic model compound	29136-19-4	P475735	1-Phenylnonadecane	purum, ≥97% (GC)	Used in studies of the hydrophobicity, phase behavior, thermal properties, molecular assembly, and organic-material applications of long-chain alkyl aromatic compounds.
Functional zinc sulfide material	1314-98-3	Z431850	Zinc sulfide	purum, ≥97%	Used in luminescent materials, optical materials, semiconductors, photocatalysis, and studies of zinc sulfide structure–property relationships.

Table 3 Purum p.a. Inorganic Salts, Buffer Systems, and Ionic-Environment Modifiers

Classification	CAS No.	Aladdin Catalog No.	Name	Specification or Purity	Product Features and Research Applications
Anhydrous phosphate buffer component	7558-80-7	S755544	Sodium dihydrogen phosphate	anhydrous grade, purum p.a., ≥99% (T)	Used in phosphate-buffer preparation and in studies of acid–base equilibria, ionic-strength adjustment, and phosphate systems.
Anhydrous phosphate buffer component	7558-79-4	S755529	Disodium hydrogen phosphate	anhydrous grade, purum p.a., ≥98% (T)	Used in phosphate-buffer preparation and in studies of acid–base equilibria, ionic-strength adjustment, and inorganic-salt compatibility.
Hydrated phosphate buffer component	13472-35-0	S431964	Sodium dihydrogen phosphate dihydrate	purum p.a., ≥99% (T), crystallized	Used in phosphate-buffer preparation, hydrate conversion calculations, acid–base equilibrium studies, and crystallization-behavior studies.
Alkali-metal chloride	7791-11-9	R475704	Rubidium chloride	purum p.a., ≥99% (AT)	Used in studies of rubidium-ion effects, electrolyte solutions, ion migration, crystal growth, and spectroscopy.
Chromium–potassium double salt	7788-99-0	C434114	Potassium chromium(III) sulfate dodecahydrate	purum p.a., ≥98.5% (RT)	Used in studies of chromium coordination chemistry, double-salt crystallization, metal-ion hydrolysis, crystal structures, and inorganic materials.
Polyphosphate complexing agent	7758-29-4	S475703	Sodium tripolyphosphate	purum p.a., ≥98% (T)	Used in studies of metal-ion complexation, water-hardness adjustment, phosphate speciation, dispersing performance, and detergent-builder systems.
Lithium-salt electrolyte	10377-48-7	L431301	Lithium sulfate	purum p.a., ≥98% (T)	Used in studies of lithium-ion electrolytes, solubility, ionic conduction, salting-out effects, and lithium-salt materials.
Cesium inorganic base	534-17-8	C432848	Cesium carbonate	purum p.a., ≥98% (T)	Used in deprotonation, nucleophilic substitution, coupling reactions, oxygen- and nitrogen-atom alkylation, and screening of basic reaction conditions.
Rare-earth cerium salt precursor	18618-55-8	C432245	Cerium(III) chloride heptahydrate	purum p.a., ≥98% (AT)	Used in cerium coordination chemistry, Lewis acid catalysis, redox systems, cerium-based materials, and nanomaterial preparation.
Cesium fluoride reagent	13400-13-0	C431924	Cesium fluoride	purum p.a., ≥98%	Used in fluoride-ion reactions, cleavage of silicon-based protecting groups, nucleophilic substitution, condensation reactions, and studies of cesium-salt effects.
Hydrated nickel-salt precursor	10101-98-1	N475706	Nickel(II) sulfate heptahydrate	≥99% (KT), crystallized, purum p.a.	Used in nickel coordination chemistry, electrochemistry, electroplating-solution models, nickel-based catalysts, and inorganic-material preparation.

Table 4 Purum p.a. Reagents for Redox Reactions, Derivatization, Separation, and Analysis

Classification	CAS No.	Aladdin Catalog No.	Name	Specification or Purity	Product Features and Research Applications
Thiosulfate reducing agent	7772-98-7	S433977	Sodium thiosulfate	anhydrous grade, purum p.a., ≥98% (RT)	Used in iodometric titration, oxidant quantitation, residual-chlorine removal, silver-halide complexation, and studies of thiosulfate reactions.
High-density mineral separation medium	79-27-6	T475707	1,1,2,2-Tetrabromoethane	purum p.a., ≥98% (GC), for separation (of mineral compounds)	Used for heavy-liquid separation of mineral particles, density fractionation, sedimentation-behavior studies, and mineral-composition analysis.
Amine derivatization reagent	70-34-8	F475701	1-Fluoro-2,4-dinitrobenzene (DNFB)	purum p.a., ≥98% (GC)	Used for the derivatization of amino acids, peptides, and primary amines, as well as for amino-terminal identification, chromatographic separation, and reactivity studies.
Borohydride reducing agent	16940-66-2	S432207	Sodium borohydride (explosives precursor)	purum p.a., ≥96%	Used in the reduction of aldehydes, ketones, and imines, as well as in metal-ion reduction, nanometal preparation, and screening of reduction conditions.
Chloride-ion colorimetric reagent	592-85-8	M475699	Mercury(II) thiocyanate	purum p.a., ≥95.5% (complexometric)	Used in the colorimetric determination of chloride ions and in studies of thiocyanate coordination, mercury complexes, and color-development reaction conditions.
Calcium phosphate inorganic salt	10031-30-8	C431148	Calcium dihydrogen phosphate monohydrate	purum p.a., ≥85% (KT)	Used in studies of calcium–phosphate dissolution equilibria, phosphate composition, mineral nutrition, crystallization behavior, and calcium phosphate materials.
Basic zinc carbonate precursor	5263-02-5	Z432827	Basic zinc carbonate	purum p.a., ≥58% Zn basis (KT)	Used in zinc oxide preparation, thermal decomposition, zinc-based catalytic materials, pigment models, and studies of carbonate structures.
Peroxide oxidizing agent	7722-84-1	H433852	Hydrogen peroxide solution (explosives precursor)	Moligand™, purum p.a., 35% (RT)	Used in organic oxidation, bleaching reactions, free-radical generation, and catalytic decomposition studies, as well as in the construction of oxidative-stress models after appropriate dilution.
Metallic copper material	7440-50-8	C434793	Copper	≥99%, purum p.a.	Used in metal catalysis, electrochemistry, displacement reactions, conductive materials, and the preparation of copper-based materials.

For more related articles, see below:

From EL to UPSSS: Cleanliness Grades, Key Specifications, and Selection Logic for Electronic-Grade Reagents

High-Purity Reagents: Overview and Aladdin Product Selection Guide

What Are Ultra Pure Reagents? – Grade Interpretation, Typical Applications, and Representative Aladdin Products

Distillation Grade Reagents: Definition, Quality Control and Representative Aladdin Products

How to Choose Reagents for Inorganic Trace Analysis — Grade Definitions & Aladdin Product List

UPLC ≈ UHPLC? How Are They Different from HPLC-plus and UHPLC-MS? One Article to Understand Grades and Applications

For Preparative Chromatography — A Detailed Guide

ULC-MS Grade Reagents — A Complete Guide: Definition, Specifications, Selection & FAQs

Understanding for HPLC Plus-Grade Reagents: Key Features, Uses, and Comparisons

The Role of Chromatography Standard Grade Reagents in HPLC, GC, and Beyond

NF Grade Explained: Standards, Tests, and Uses

HPLC-Grade Solvents for High-Performance Liquid Chromatography: From Concept to Practice

A Lab Guide to Photographic Grade Reagents: Standards, QC, and Selection Tips

Electrochemical Grade Reagents: What It Means and When to Use It

Choosing Reagents for GC Derivatization: What the Grade Means

Puriss. p.a.: what it means, when to use it, and how it compares

Benchmark Reagents (PT): A Practical Guide

AR（Analytical Reagent）grade — a practitioner’s guide

What Are Analytical Standards? A Practical Guide