Do you know that solvents like ethanol and acetone, which you often use, actually have more than 50 specification? In this article, we outline the specifications of reagents including general-purpose solvents and introduce general-purpose solvents upgraded for various purposes.

What Are the Specifications of Reagent?

Today's society is filled with different types of chemical substances (compounds). For example, there are more than 170 million CAS-registered chemical substances¹⁾ that support our rich lives in all situations. Among such chemical substances, the "chemical substances used for measurement criteria, detection/identification of substances, quantification, separation/purification, organic synthesis, physical property measurement, etc. in testing/research such as inspection, testing, research, experiment, etc., whose quality is assured according to the intended use and which are suitable for use in a small quantity"²⁾ are called reagents.

Table 1 shows 4 categories of reagents (reagents for general use/reagents for specific use/reference materials and standard solutions/high-purity reagents) and intended use example.^2-4)

Table 1. Classification of Reagents

Classification by intended use		Intended use
For general use (Guaranteed Reagent/Wako Special Grade/Wako 1st Grade)		Generally used without limiting the use. There are many JIS standards (example: Guaranteed Reagent) and in-house standards conforming to JIS (example: Wako Special Grade... Equivalent to JIS special class, Wako 1st Grade... Equivalent to old JIS class) for general-purpose products.
Specific use	For instrumental analysis	For instrumental analysis (for HPLC, for GC, for Atomic Absorption Spectrochemical Analysis, for ICP, for Spectrochemical Analysis, for Fluorometric Analysis, for Electron Microscopy, for NMR, for Spin Trapping)
	For measurement of hazardous substances and environmental contaminants	For measurement of hazardous substances and environmental contaminants (for Analysis of Poisonous Metals, for Pesticide Residue Analysis, for PCB Determination, for Oxidant Analysis, for Nitrogen Oxides Analysis)
	For organic synthesis	Reagents for organic synthesis (reagents used in discovery research of new compounds such as pesticides, drugs, polymers, and functional materials, research on their synthesis processes, or research on elucidation of the properties and functions of various organic compounds; starting materials for synthesis, intermediates, reactants, catalysts, solvents, separation/purification agents, etc.)
	For biochemistry	for Amino Acid Automated Analysis, for Amino Acid Sequence Analysis, for Fluorescent Labeling, for Electrophoresis, for Peptide Synthesis, for Immunochemistry (antigens, antibodies, for Immunocytochemistry, complements, adjuvants, and immunoassay-related reagents), for Genetic Research (gene recombination, for Nucleic Acid Synthesis, Gene Mutation Detection Kit), for Cellbiology, for Cell Culture [for animal tissue (cell) culture, for microbial culture, for vegetable tissue (cell) culture], Glycobiology.
	For laboratory tests	General-purpose reagents, reagent kits, and prepared reagents; Reference material, control serum, staining solution
	Other	pH standard solution, for Thin Layer Chromatography
Reference standards (analytical standards) and standard solutions		Analytical standard for volumetric analysis, metal standard solution, ion standard solution, pH standard solution, analytical standard for environmental/food analysis
High-purity reagent		High-purity reagents for advanced fields such as electronics and biotechnology

Due to the reagent characteristics of small amount and large variety, manufacturing is performed not by continuous mass production using dedicated production facilities as is the case with general chemical industries but by a small batch method using common facilities, and it is said that setting of reaction conditions to provide uniform quality is difficult³⁾. Therefore, the quality of the reagent must be kept constant for stable and reproducible manufacturing and analysis using the reagent. In this way, the specification of the reagent ensures that the quality of the reagent is always maintained under a stable condition.

Type of Reagent Specification

There are different types of reagent specifications as shown below.

National/International Standards

Depending on which organization, establishes the specifications for reagents, there are 2 types of specifications: domestic specifications (U.S. ... ACS, Japan ...JIS, etc.) established by public organizations in each country and international specifications by the International Organization for Standardization (ISO).

[1] JIS standard

The typical Japanese standard is the Japanese industrial standard (JIS). This is a public specification set by the Council of the Ministry of Economy, Trade and Industry, "Japanese Industrial Standards Committee (JISC)"⁵⁾ based on the Industrial Standardization Act, and as of February 2021, there have been a total of 10,899 specifications, of which 1,784 have been set by Division K (Chemical Engineering) regarding chemical substances. It includes specifications for individual chemical substances (including the scope, common items, types (special class), properties, quality, test methods, containers, storage methods, and labeling) and special chemical substances (JIS K 8008: biochemical reagents, JIS K 8007: highly purified reagents) in addition to specifications (KIS K 0050: general rules for chemical analysis, JIS K 8001: General rules for test methods of reagents) that specify chemical analysis methods, and reference materials for analysis. For example, 3 specifications have been established for acetone (JIS K 1503: 1st grade, JIS K 8034: special grade, JIS K 8040: for pesticide residue and PCB tests).

[2] Standards of various laws and regulations

In addition, it may be required to meet the standards of various laws and regulations such as the Law Concerning the Examination and Regulation of Manufacture, etc. of Chemical Substances, the Pharmaceuticals and Medical Devices Low, and the Poisonous and Deleterious Substances Control Low.

[3] In-house specifications

In addition, there are in-house specifications independently established by reagent manufacturers in each country (example. Wako Special Grade/Wako 1st Grade). Each manufacturer has established specifications for reagents with various quality assurance, including chemical substances not registered in the above standards of public institutions, etc.

Specifications of General-purpose Solvents

Next, let's look at the specifications of general-purpose solvents.

Table 2 summarizes the specification of FUJIFILM Wako reagents by intended use, the presence or absence of official specifications such as JIS and laws/regulations, and the presence or absence of corresponding specifications of representative general-purpose solvents (Methanol, Ethanol, Acetone, Acetonitrile, Tetrahydrofuran). Although there are as many as 34 specifications, it can be seen that only 7 specifications correspond to JIS standards, legal regulations, etc., and the other specifications are optimized for individual use.

Table 2. Classification of FUJIFILM Wako Reagents by Intended Use for Representative Solvents

For biochemistry

Classification by intended use		Name of FUJIFILM Wako specification	official specification	General-purpose Solvent
				Methanol	Ethanol	Acetone	Acetonitrile	Tetrahydrofuran
for general use		Wako 1st Grade		〇	〇	〇	〇	〇
		Guaranteed Reagent	〇	〇	〇	〇	〇	〇
		Wako Special Grade			〇			〇
Specific use	for Instrumental Analysis	for HPLC		〇	〇	〇	〇	〇
		for LC/MS		〇	〇		〇
		for GPC						〇
		for QTofMS		〇			〇
		for the Japanese Pharmacopoeia General Tests (for Liquid Chromatography)	〇	〇			〇	〇
		for Spectrochemical Analysis		〇	〇	〇	〇	〇
		for NMR		〇	〇	〇	〇	〇
		for Preparative Chromatography		〇			〇
		Concentration 5000/300	〇	〇	〇	〇	〇
	for Measurement of Hazardous Substances and Environmental Contaminants	for Boron Determination		〇
		for Dioxin Analysis		〇	〇	〇
		for Trihalomethane Analysis		〇
		for Tiuram Analysis					〇
		for PFOS-PFOA Analysis		〇			〇
		for Aldehyde Analysis					〇
		for Environmental Analysis		〇	〇	〇	〇
		for Vinyl Chloride Monomer Analysis						〇
		for RoHSⅡ	〇		〇	〇
	for Organic Synthesis	for Organic Synthesis		〇	〇	〇	〇	〇
		for Nucleic Acid Synthesis					〇
	for Biochemistry	Super Special Grade		〇	〇
		for Proteomics				〇
		for Cell Culture			〇
		for Molecular Biology		〇	〇
	for Drug Testing	Japanese Pharmacopoeia	〇		〇
		for Medicine Test		〇	〇	〇
	High-purity reagent	Infinity Pure		〇	〇	〇	〇	〇
		for Electronics Industry		〇	〇	〇
	Other	for Chromatography		〇		〇
		for Determination of Wetting Tension	〇	〇

For Acetonitrile

As shown in Table 3, the specifications of acetonitrile of Guaranteed Reagent were compared with that of 3 specifications for instrumental analysis, including that for HPLC, for LC/MS, for QTofMS.

Table 3. Each Specification Value of Acetonitrile

Specification item		Guaranteed Reagent	for HPLC	for LC/MS	for QTofMS
Assay (capillary GC) (%)		min. 99.5	min. 99.8	min. 99.8	min. 99.8
Density (20℃) (g/mL)		0.780 ~ 0.784	0.780 ~ 0.783	0.780 ~ 0.783	0.780 ~ 0.783
Refractive index nD20		1.343 ~ 1.346	1.343 ~ 1.346	1.343 ~ 1.346	1.343 ~ 1.346
Water (%)		max. 0.1	max. 0.05	max. 0.05	max. 0.05
Residue after evaporation (ppm)		max. 0.005	max. 0.001	max. 0.001	max. 0.001
Acidity (as CH3COOH) (ppm)		max. 0.01	max. 0.001	max. 0.001	max. 0.001
Ammonium (NH4) (ppm)		－	max. 0.3	max. 0.3	max. 0.3
Peroxides (as H2O2) (ppm)		－	max. 5	max. 5	max. 5
Hydrogen cyanide		to pass test	－	－	－
Substances reducing permanganate		to pass test	to pass test	to pass test	to pass test
Gradient test		－	to pass test	to pass test	－ (Suitability for QTofMS analysis: to pass test )
Particles (0.5 μm or more) (particles/mL)		－	－	max. 100	max. 100
Absorbance	200 nm	－	max. 0.05	max. 0.05	max. 0.05
	210 nm	－	max. 0.03	max. 0.03	max. 0.03
	220 nm	－	max. 0.02	max. 0.02	max. 0.02
	230 nm	－	max. 0.01	max. 0.01	max. 0.01
	240 nm	－	max. 0.005	max. 0.005	max. 0.005
Fluorescence test		－	to pass test	to pass test	to pass test
Suitability for LC/MS analysis		－	－	to pass test	－
Suitability for QTofMS analysis		－	－	－	to pass test

There are 20 specifications of acetonitrile for each intended use, but in chromatographic analysis such as HPLC, it is used for mobile phase and dissolution of samples. The contents of these 3 specifications are higher than that of the Guaranteed Reagent by 99.8% or more, and impurities such as residual moisture and nonvolatile matter are reduced. In addition, special tests ensure appropriate performance for analysis, such as:

• Absorbance/gradient test: Stability of background when detecting ultraviolet-visible absorbance, suppression of baseline variation
• Fluorescence test: Reduction of background noise of fluorescence detector
• Number of particles: Reduction of the effect on column life
• Suitability for LC/MS analysis: Reduction of background noise of mass spectrometer
• Suitability for QTofMS analysis: Connect the column to UHPLC, perform gradient measurement using QTofMS, and the baseline variation is not more than the standard. Quality control using multivariate analysis

The solvent is treated by the original technology to meet the performance suitable for each analysis, and the packaging form (removal of contamination from the cap, dedicated resin or aluminum cap, brown glass bottle with reduced elution, etc.) to minimize the contamination from the reagent container is adopted.

For Acetone

In Table 4, the specifications of acetone of Guaranteed Reagent were compared with that of 4 specifications, for Environmental Analysis, for Organic Synthesis, and for Electronics Industry. Acetone is frequently used for cleaning, but it has characteristics in the specification items depending on the intended use.

Table 4. Each specification value of acetone

Specification item	Guaranteed Reagent	for Environmental Analysis	for Organic Synthesis	for Electronics Industry
Assay (capillary GC) (%)	min. 99.5	min. 99.8	min. 99.5	min. 99.7
Density (20℃) (g/mL)	0.789 ~ 0.792	0.789 ~ 0.792	0.789 ~ 0.792	0.789 ~ 0.792
Refractive index nD20	1.358 ~ 1.360	－	1.358 ~ 1.360	1.358 ~ 1.360
Water (%)	max. 0.3	max. 0.3	max. 0.001	max. 0.25
Residue after evaporation (ppm)	max. 5	max. 2	max. 5	max. 1
Acidity (as CH3COOH) (ppm)	max. 20	－	max. 15	max. 10
Ammonium (NH4) (ppm)	max. 10	－	max. 10	max. 1
Aldehydes (as HCHO) (ppm)	max. 20	－	max. 20	max. 10
Methanol (CH3OH) (ppm)	max. 500	－	max. 500	max. 500
Substances reducing permanganate	max. 2	－	max. 2	－
Other special specifications				Residual elements Ag, As, Ba, Ca, Cd, Co, Li, Mg etc....max. 0.5 ppb Fe, K, Sn etc....max. 1 ppb

• for Environmental Analysis: Confirm that there are no endocrine disruptors and halogenated organic substances using high-resolution GC/MS or GC-ECD. Assure that the content is not less than 99.8% and the content of non-volatile matter is not more than 2 ppm.
• for Organic Synthesis: Reduce the amount of water that inhibits the reaction to 0.001% or less.
• for Electronics Industry: Impurities are removed to the limit for semiconductor industry. Assure that the content is not less than 99.7%, water content is not more than 0.25%, non-volatile matter is not more than 1 ppm, various elemental impurities are not more than ppb, particle control, etc.

Abbreviation

• ACS＝American Chemical Society
• CAS＝Chemical Abstracts Service
• ESR＝Electron Spin Resonance spectroscopy
• GC＝Gas Chromatography　
• GC-ECD＝Gas Chromatograph‐Electron Capture Detector　
• UHPLC＝Ultra High Performance Liquid Chromatography
• HPLC＝High Performance Liquid Chromatography
• ISO＝International Organization for Standardization
• JIS＝Japanese Industrial Standards　
• JISC＝Japanese Industrial Standards Committee
• LC/MS＝Liquid Chromatography - Mass Spectrometry
• NMR＝Nuclear Magnetic Resonance spectroscopy
• PCB＝PolyChlorinated Biphenyl　
• PFOS=PerFluoroOctaneSulfonic acid, PFOA=PerFluoroOctanoic Acid
• ppm＝parts per million　1ppm = 0.0001%
• ppb＝parts-per-billion　1ppb = 0.001ppm = 0.0000001%
• QTofMS＝Quadrupole Time-of-flight Mass Spectrometer　

Reference

1. American Chemical Society：CAS REGISTRY - The gold standard for chemical substance information
   http://www.cas.org/content/chemical-substances
2. Japan Reagent Association web site
   https://www.j-shiyaku.or.jp/
3. Nishiyama, S.: Chapter 4 Specifications of Reagents: Japan Standards Association Group, Development Teaching Materials for Standardized Education Program, Individual Technology Area Edition, Chemistry
   https://www.jsa.or.jp/datas/media/10000/md_2506.pdf
4. National Institute of Advanced Industrial Science and Technology, Metrology and Standards Institute, Japan Reagent Association: Revised 4th edition, Guidebook for Reagents: The Chemical Daily (2020)
5. Japanese Industrial Standards Committee web site
   https://www.jisc.go.jp/eng/index.html

Reference Information

• HPLC Solvents
• LC/MS Solvents
• GPC Solvents
• Solvents for Three Pharmacopoeias
• Q-Tof/MS Solvents
• Solvent for Residual Pesticide and PCB Analysis
• Reagents for RoHSⅡ
• Dioxin Analysis Solvents
• Anhydrous Solvents
• Anhydrous and Air-Sensitive Solvent
• High-purity Solvent and Acid