The Proper Storage and Handling of Volatile Analytical Standards

Volatile analytical standards are a necessary component in several analytical chemistry applications such as calibration, quality control, and method validation. These standards are used in gas chromatography (GC), mass spectrometry (MS), and headspace analyses, where concentrations and integrity of analytes are essential. These standards are highly volatile, so they must be handled and stored carefully to ensure their precision, stability and efficiency. The guidelines in this article include the best practices for the storage and handling of volatile analytical standards to prolong their usefulness, maintain their consistency, and remain safe for scientific investigations and analyses.

Storage and Handling of Volatile Analytical Standards

Understanding Volatile Analytical Standards

Volatile analytical standards are compounds that readily evaporate at room temperature and can be a gas or liquid. These chemicals are essential to instruments' calibration and measuring accuracy. Common examples include:

Alcohols: Methanol, ethanol
Ketones: Acetone, methyl ethyl ketone (MEK)
Hydrocarbons: Methane, toluene
Halogenated compounds: Chloroform, dichloromethane

These compounds can be pure or mixed with other chemicals to form calibration standards based on actual samples.

Storage Guidelines for Volatile Analytical Standards

Storing volatile standards in the right conditions can ensure the stability of the standard as its concentration varies with time through evaporation or degradation. Here are the key considerations:

a. Use of Proper Containers

Sealed Containers: For volatile standards, keep them in sealed containers to avoid evaporation. The glass vials that are sealed (eg, with crimp seals) are very typical. Amber glass bottles or aluminium-sealed vials are preferred for small quantities as they do not receive much light and are less likely to evaporate.
Avoid Plastic Containers: Plastic may bind or react with some volatiles which can contaminate or leak analyte. They like glass because it's chemically inert.
Screw-Cap Vials: Screw-cap vials with PTFE septa to minimize leakage. These are commonly used for gaseous and liquid volatile standards.

b. Temperature Control

Cool, Dry Environment: Standard gases should be kept dry, in a refrigerator (2 °C to 8 °C) or freezer (under 0 °C) to prevent evaporation and oxidation.
Avoid Freezing Certain Compounds: Some volatile compounds, such as acetone or methanol, can freeze at low temperatures. Check the compound's freezing point before storing in the freezer.
Temperature Stability: Volatile standards should be stored in a place where temperature variations are low so condensation or vapor pressure changes cannot affect concentrations.

c. Protection from Light

Amber Glass Vials: Volatile substances such as alcohols and hydrocarbons can be damaged or react with light. The amber glass vials or opaque bottles are ideal to shield these standards from UV and reflected light.
Avoid Direct Sunlight: Store standards in a cool room away from the sun to avoid UV degradation.

d. Avoid Contaminants

Clean Storage Area: Maintain volatile standards in a place where there is no dust, chemical or solvent that could react with the standards.
Check for Contamination: If there is reason to believe that the container has been breached, simply throw out the standard and prepare a new one so results are not inaccurate.

Handling Volatile Analytical Standards

When handling volatile standards, great care must be taken to prevent contamination, loss of analyte, and degradation. Follow these best practices:

a. Use of Proper Equipment

Syringes and Pipettes: Use professional syringes and pipettes for volatile standards. To obtain gas phase standards, small quantities of volatiles are often measured with a gas-tight syringe.
Avoid Exposure to Air: Reduce air and humidity exposure during the opening of volatile standards. Air exposure can lead to evaporation or contamination.
Use Gloves: Always wear gloves to prevent skin contamination, as direct contact can lead to loss of analyte or contamination of the standard.

b. Minimize Open Time

Limit Exposure: When using volatile standards, minimize the time that containers are opened. Exposure to air will evaporate, changing the concentrations and causing misrepresentation.
Work Quickly: Take aliquots quickly and re-cap the containers immediately following use to prevent evaporate or contamination.

c. Calibration and Dilution

Use of Secondary Standards: For precise calibration, use secondary standards prepared from primary standards. Secondary standards should be fresh, and store the same way as primary standards.
Proper Dilution: When diluting volatile standards, do it very carefully to get proper concentrations. Use appropriate solvents and ensure that the volatile compound is thoroughly mixed.

Stability and Shelf Life

Volatile standards vary according to many parameters, such as the volatility of the compound, storage and container. There will be molecules that will deteriorate, bind to the vessel material or evaporate, changing the concentrations over time.

a. Expiry Dates

Check Expiry: Volatile standards generally have an expiration date, which should be followed to ensure their accuracy. This date should be clearly marked on the container.
Re-evaluation of Standards: If the volatile standard is approaching its expiration date or has been stored improperly, it may be necessary to re-evaluate its concentration using appropriate analytical techniques.

b. Stability Testing

Regular Monitoring: Check volatile standards' stability frequently by measuring the concentration by trained analytical techniques such as GC or MS. This makes sure that degradation or loss of analyte is caught in time.
Recalibration: Recalibrate instruments and standards regularly to be uniform and reliable.

Disposal of Volatile Analytical Standards

Disposal of volatile standards must be done under safety regulations pertaining to toxic chemicals. Proper disposal procedures should include:

Waste Containers: Store used standards in appropriate waste containers (e.g., chemical waste drums) that are clearly labeled and compatible with the volatile compounds.
Compliance with Regulations: Follow local regulations for hazardous chemical disposal, including proper transportation and treatment processes for volatile substances.
Avoid Spills: Handle containers carefully to avoid spills, which can lead to contamination or health hazards.

Case Studies

Case 1: Incorrect Storage Leading to Concentration Loss (Acetone Standard)
Background	As a volatile analytical reference, for a study on air contaminants, acetone was employed with the intention of quantitative analysis by Gas Chromatography (GC). But since the storage bottle had not been sealed correctly, the acetone evaporated, which caused the sample concentration to fall.
Incorrect Practice	Acetone standard was stored in an unsealed plastic bottle. The concentration of the standard was not regularly monitored, and it was exposed to air for an extended period.
Impact	The concentration of acetone decreased by approximately 20% over the course of one week, leading to inaccurate GC analysis results and affecting the final research conclusions. The significant error could distort pollution source analysis and affect the reliability of environmental monitoring data.
Correct Practice	Use a sealed glass bottle with PTFE-lined aluminum closure to reduce evaporation. Store in a refrigerated environment at 4 °C to slow evaporation and maintain concentration stability. Regularly monitor the concentration of the standard to ensure its accuracy.
Case 2: Photodegradation Leading to Errors (Ethanol Standard)
Background	In a pharmaceutical analysis study, scientists calibrated the instrument with ethanol. The ethanol standard became photodegraded as a result of lab light exposure.
Incorrect Practice	The standard was kept in a clear glass bottle and laid on the workbench under bright light. The ethanol standard was not checked for degradation over time.
Impact	The ethanol standard degraded due to light exposure, causing its concentration to decrease, and it could no longer provide accurate calibration. The instrument's response was inaccurate, ultimately affecting the drug analysis results.
Correct Practice	Use amber glass bottles or opaque containers to store the ethanol standard. Store the standard in a cool, dark place to prevent light degradation and ensure stability.
Case 3: Excessively Low Temperature Storage Leading to Freezing of the Standard (Methanol Standard)
Background	When using methanol as a solvent in gas chromatography analysis, the methanol standard was placed in too low a temperature, so it would freeze, and the results would suffer.
Incorrect Practice	The methanol standard was stored at -20 °C. The standard was not checked to see if it had frozen.
Impact	When methanol froze, it became difficult to extract from the bottle, preventing proper use of the standard. Once dissolved, the standard could not recover its original concentration, resulting in inaccurate instrument calibration and affecting experimental results.
Correct Practice	Store methanol standards in a refrigerated environment between 2 °C and 8 °C to avoid freezing. Regularly check the condition of the standard to ensure it can dissolve properly and be used for analysis.

Conclusion

Stored and handled volatile analytical standards are critical to preserving integrity and the integrity of analyses. If the container is designed properly, the temperature controlled, the light and the exposure to air can be kept to a minimum, the possibility of degradation or contamination can be minimized. Monitoring and adhering to shelf life criteria will ensure that these parameters are up-to-date for consistent analysis results. Disposal makes volatile materials safe for both workers and the environment.

These measures ensure that volatile standards are stable, effective and inert enough to be applied to analytical chemistry.

Resources

Send Us a Request

What is your specific need? We will do everything we can to meet your expectations.

Online Inquiry