Frequently Asked Questions about solvents in hematology & histology research by Sigma-Aldrich.

General Information
Tax-Paid Ethanol
Physical Properties
Application Notes
Returnable Containers

How do I get specific lot information or CofA for a solvent?

A Certificate of Analysis is available by lot for each of our solvents and can be accessed through our Advanced Search Option.
Online Certificate of Analysis

Who do I contact about larger solvent volume needs?

Email us at labessentials@sial.com or visit Sigma-Aldrich Fine Chemicals for development and manufacturing-scale inquiries.

How do I know what packaging options are available for a solvent?

The Solvent Center gives you the ability to review all the specifications associated with our solvent packaging. This includes physical dimensions, closure types, dispensing methods, UN/DOT Rating as well as solvent compatibility.

Who do I contact if I need a solvent blend, which you do not carry?

Email us at labessentials@sial.com. For a complete listing of all our Solvent blends, visit the Solvent Center .

The dispensing of solvents provides some challenges due to the number of container options available. What dispensing options are available for each container?

The Sigma-Aldrich Solvent Center provides numerous dispensing options for each container type.

Why on occasion does my Methanol have an unusual odor? Does it affect the product purity or performance?

Industry research has indicated that unusual odors in methanol are a common problem and stem from low - level mercaptans and / or amines found in the natural gas raw materials used in production. Odors from these types of compounds can be noticeable at low part per million (ppm) levels and have not been shown to have any negative impact on product performance at these concentrations.
GC Analysis of Methanol with Off - Odors

What are some of the preservatives used in the most common ethers and chlorinated solvents and why are they added?

Certain solvents will degrade over time requiring special handling and storage considerations. In addition, the products of certain degradation processes pose a potential safety risk if present at sufficiently high levels. For these types of materials, small amounts of stabilizing chemicals are added to slow down or stop material degradation.

It is important to understand the stability of materials in use and if unclear, consult the Sigma-Aldrich Technical Support and Product Safety Center & MSDS Search. Summary of Stabilizer Systems

Why do peroxides form in certain solvents and how do I test for it?

A significant number of laboratory solvents can undergo autoxidation under normal storage conditions to form unstable and potentially dangerous peroxide by-products. Molecular structure is the primary factor relating to a material’s potential for hazardous peroxide formation.

It is important to understand the stability of materials in use and if unclear, consult Sigma-Aldrich Technical Support. Peroxide–Forming Solvents

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What is 190 proof and 200 proof ethanol?

All ethanol products have a proof associated with the product description. The proof is a measure of the water content of the ethanol portion of the product. The proof is calculated as two times (2 x) the actual ethanol concentration by volume.
Sigma-Aldrich Tax-Paid Ethanol Listings

How can I get help with the ATF paperwork for 190 and 200 proof ethanol?

Because these ethanols are federally regulated, an ATF permit is required to purchase 190 and 200 proof ethanol. Sigma-Aldrich takes the hassle out of this process for you! There is no ATF paperwork needed or records to be kept on your part. Sigma-Aldrich immediately pays the federal excise tax (200-proof pure alcohol = $27.00/gallon).
For more regulatory information regard the tax on ethanol, visit the

Can you recommend a Solvent Extractor for organics from aqueous solution?

For the quantitative extraction of organics from aqueous solutions and separations in immunoassays. The MIXXOR system has been applied successfully in many laboratory solvent extraction operations and is ideal for the rapid screening of alternative solvents for specific extraction problems.

How do I effectively clean the inside and outside of my NMR tubes?

The Sigma-Aldrich Dual-Action NMR Tube Cleaner simultaneously cleans tubes inside and out.

What Vacuum Pumps are solvent resistant?

KNF Laboport vacuum pumps solid PTFE heads, molded PTFE diaphragm and Kalrez® parts which eliminates chemical attack to the pump.

What is a useful Solvent for Recrystallization?

"1-Chlorobutane - A Useful Solvent for Recrystallizations"
David G. Morris, Ph.D., Department of Chemistry, University of Glasgow
ACTA 34, NO. 2, 2001

What is a good method for crystallization solvents?

"Aldrich Rotary Evaporator Antisplash Adapters as Solvent Traps in Recrystallization"
Mahesh K. Lakshman, Department of Chemistry, University of North Dakota
ACTA 33, NO. 1, 2000
Antisplash Adapters

How can solvents be removed from low melting crystals?

"Moving Disc Filtration: Low-Temperature, Inert Atmosphere Removal of Solvent from Low-Melting Crystals in an Ordinary, One-Neck Flask"
Roger C. Hahn, Associate Professor, Department of Chemistry, Syracuse University
ACTA 31, NO. 3, 1998

How can I prevent cross-contamination in my solvent still?

"Preventing Cross-Contamination in Solvent Stills Connected in Series to the Same Inert Gas Manifold" Maravanji S. Balakrishna, Department of Chemistry, Indian Institute of Technology
ACTA 33, NO.2, 2000

When running HPLC, what is an easy means to protect your instrument and columns?

Supelco Mobile Phase Filtration Apparatus removes particles and gases from solvents and other mobile phase components.
Reporter, January 2004 (74 K PDF)

Analysis of Solvents in Industrial Atmospheres by Capillary GC
Application Note 2 (142 K PDF)

Organic Volatile Impurities in Pharmaceutical, Products: Selectivity of Capillary GC Columns
Application Note 70 (151 K PDF)

Analyzing Trace Amounts of Solvents in Water Using Packed Column GC
Bulletin 816 (246 K PDF)

Petroleum/Chemicals Application Guide
Bulletin 858 (813 K PDF)

ASSET-32 Air Sampling Solid Extraction Tubes: Specifications - Performance - Validation Data - Round Robin Evaluation
Bulletin 924 (138 K PDF)

SPME Application Guide
Bulletin 925 (2.6 M PDF)

Our Technical Service Team will be happy to help you with product specific questions!

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What solvents are available in returnable containers?
For a complete list of solvents available in returnable containers, click here.

How many types of returnable containers are available?
Sigma-Aldrich offers solvents in three different types of containers. The container type is determined by what solvent is required and the grade of the material.

• Pure-Pac I
• Pure-Pac II
• Kilo-Lab

What is the difference between the Pure-Pac I and Pure-Pac II?

The Pure-Pac I container has a tube fitting connection for the solvent transfer line and nitrogen inlet. The Pure-Pac I also has a pressure gauge.

The Pure-Pac II container is equipped with a central extractor valve. The extractor valve requires a Micromatic MacroValve coupler for dispensing solvent from the container. The MacroValve is a quick-connect style coupler that has the nitrogen inlet and pressure relief device built into the unit. The Micromatic MacroValve coupler is sold separately. We offer dispensing head kits that include the Micromatic MacroValve for the Pure-Pac II. The kit contain a 3/8? tube fitting or a 1/2? tube fitting for connecting to a transfer line.

Z566020 3/8? tube fitting dispensing kit
Z566039 1/2? tube fitting dispensing kit

Valve configuration for Pure-Pac I
Configuration for Pure-Pac II

Do I return the Micromatic MacroValve coupler when the Pure-Pac II is empty?

No. The coupler stays with the customer and can be used on the next full Pure-Pac II.

What is the difference between Pure-Pacs and Kilo-Labs?

The Pure-Pac containers are constructed of 304 stainless steel. The Kilo-Lab containers are constructed of carbon steel.

What is the construction of the containers?

Pure-Pac I — 304 stainless steel
Pure-Pac II — 304 stainless steel with Simriz gaskets and seals
Kilo-Lab — Carbon steel with stainless steel valves

What sizes of containers are available?

What are the dimensions for the various sizes of returnable containers?

Pure-Pac I (inches)

Pure-Pac II (inches)

Kilo-Lab (inches)

What are the tare weights for the different types and sizes of returnable containers?

What are the connections for the solvent outlet and nitrogen inlet for the different types of containers?

Are the returnable containers shipped under positive pressure?

Yes. The containers ship with 3–5 psig of nitrogen pressure. This is to ensure that the solvent is not exposed to the atmosphere.

Do the containers have a pressure relief device?

Each returnable container is equipped with a pressure relief device. This device will relieve the excess pressure once the container reaches the relief cracking pressure. The device will reseat itself once the excess pressure is relieved.

What is the pressure relief set at?

What is the maximum recommended working pressure?

Should the returnable containers be grounded before dispensing solvent?

Yes. A proper grounding wire should be connected to the returnable container and an appropriate ground. This will prevent sparking of static electricity generated by transferring flammable liquids. Sigma-Aldrich offers proper grounding wires.

Are the Returnable Containers ASME certified?

The Pure-Pac I container is ASME certified.

Are the Returnable Containers FM Approved?

The Pure-Pac I container is FM Approved.

How do I dispense solvents from the returnable containers?

There are Technical Bulletins that describes the transferring procedures for each type of returnable container. Please visit sigma-aldrich.com/techbulletins.

Are level sensors available?

Level Sensors are available for the 200 and 400L Pure-Pac I and the 50L and 200L Pure-Pac II.

Are the containers dedicated to one customer?

Containers are dedicated if a fleet has been set up for your contract. Since containers are dedicated, it is important that the containers are returned as soon as they are empty. This will ensure that service will not be interrupted due to containers not being available for filling. A return procedure and plan will be defined for contract customers.

Are the containers dedicated to one solvent?

In most cases, containers are dedicated to one solvent. If a different solvent is packaged in the returnable container, Sigma-Aldrich has strict guidelines on cleaning and preparing the container for the new solvent. Sigma-Aldrich runs QC analysis on the containers before the new solvent is filled into the container. This ensures that there isn’t any cross contamination.

How is the fleet size determined?

The size of the returnable container fleet is based on which size of container, the annual solvent usage, the number of dispensing sites and your location. Your local Sigma-Aldrich Representative will collect this information and we will determine the recommended fleet size.

Do you have local warehousing?

Yes. In some instances local warehousing is available for servicing returnable containers. Contact your local Sigma-Aldrich Representative to see if this option is available in your area.

What should be done with the containers when they are empty?

Empty containers should be sent back as soon as they are empty. Contact your local Sigma-Aldrich Representative or Technical Service for more details. A return procedure and plan will be defined for contract customers.

How do I return the containers once they are empty?

Customers are responsible for returning the containers if a return procedure has not been defined. If a procedure has not been set-up, please visit sigma-aldrich.com/cylinderreturn for an easy and convenient method for returning containers. Customers with a contract will have a return procedure and plan defined.

What is Unishippers?

Unishippers is a third party that partners with shipping companies to handle customers' shipments. They partner with major carriers to handle nearly one million shipments a month. Based on the combined volume of over 80,000 Unishippers customers, they can offer you deep discounts typically reserved for much larger volume shippers. Please visit sigma-aldrich.com/cylinderreturn.

How do I get the returnable container process started?

The first step is to contact your local Sigma-Aldrich Representative. They will discuss the basics of the program and collect the necessary information to help use determine which type of container will met you application. This information will also help us determine how many containers will be required in your fleet.

What is the lead-time for receiving the first containers?

Usually, it takes 3-4 weeks to build the inventory for your solvent usage. After the initial build-up, full containers will be available when you need to place your next order.

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