Abstract No:
1444
Abstract Type:
Professional Poster
Authors:
T Popov1
Institutions:
1University of Central Missouri, Warrensburg, MO
Presenter:
Tsvetan Popov, PhD, CIH, CSP
University of Central Missouri
Description:
This project focuses on developing a method for air sampling and analysis of methylene chloride using solid sorbent tubes, followed by thermal desorption and analysis by gas chromatography with flame ionization detection.
Methylene chloride, or dichloromethane, is an organochlorine compound used in various applications, including automotive products, paint and coating removers, organic synthesis, and sample preparation in analytical chemistry.
In April 2024, the EPA issued a final rule regulating methylene chloride under the Toxic Substances Control Act (TSCA) to protect human health from health risks.
Situation / Problem:
The Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH) have developed multiple methods for sampling and analysis of methylene chloride. The methods are based on sampling with sorbent tubes containing one or two sorbent layers. After sampling, the sorbent is transferred to vials, separately extracted with solvent, and analyzed using gas chromatography with a flame ionization detector (GC-FID). Although this approach has been successfully used for decades and has certain advantages, e.g., reliability, high recovery, and accuracy, it also has some disadvantages. The sample preparation requires separating sorbent layers, using a toxic solvent for extraction (e.g., carbon disulfide, selected due to low affinity to FID), the dilution of samples, and decreased method sensitivity. With the introduction of synthetic sorbent materials and thermal desorption, followed by gas chromatography, volatile organic compounds can be sampled and directly analyzed without diluting the samples with FID, improving sensitivity during the analysis.
Methods:
A certified mixture of methylene chloride with a concentration of 2,000 μg/mL in methanol was obtained from Restek (Bellefonte, PA) to prepare calibration standards in step dilutions.
Analytical grade methanol (99.9%) was purchased from Sigma-Aldrich (St. Louis, MO) and ultrapure water (MilliporeSigma, Rockville, Maryland) was used for sample preparation.
Sorbents, including Tenax TA, Tenax GR, and deactivated wool, were used to pack GC liners. Six-Tube Conditioner, Model 9600 from CDS Analytical (Oxford, PA) was used to purge the prepared tubes with nitrogen (99.999%) and spike with target compounds using a dedicated spiking port. The samples were analyzed using an SRI Instruments (Torrance, CA) gas chromatograph, model 8610C, equipped with a FID. The carrier gas was hydrogen with purity above 99.999% generated onsite with hydrogen generator and the column, obtained from Restek was MXT-Wax (30 m x 0.53 mm ID, 1.0 um).
Results / Conclusions:
During the method development, different parameters, including carrier gas flow rate and column temperature run, were optimized to improve the resolution of the target compound and reduce the time of analysis. Methylene chloride was well separated without interference from the sorbent matrix. The selected sorbents had recovery rates above 90%. The calibration curves for all target compounds showed correlation, R2 above 0.995, with relative standard deviation, RSD below 10%, demonstrating very good linearity and precision.
The reported limits of detection (LODs) and limits of quantitation (LOQs) for methylene chloride were at the nanogram level, corresponding to airborne concentration in the low parts per billion (ppb) and high parts per trillion (ppt) range. Therefore, compared to the methods based on sorbent extraction, the LODs and LOQs improved the sensitivity of analysis by two to three orders of magnitude.
Core Competencies:
Chemical Sampling and Instrumental Analysis
Secondary Core Competencies:
Chemical Hazards
Exposure Assessment
Choose at least one (1), and up to five, (5) keywords from the following list. These selections will optimize your presentation's search results for attendees.
Exposure Assessment
Gas and vapor detection
Labs – Health & Safety, Testing
Based on the selected primary competency area of your proposal, select one group below that would be best suited to serve as a subject matter expert for peer review:
(Select one)
Sampling and Laboratory Analysis Committee
Based on the information that will be presented during your proposed session, please indicate the targeted audience practice level: (select one)
Practitioner: Practitioner is a job title given to persons in various occupational fields who are trained to assist professionals but are not themselves licensed or certified at a professional level by a certification body recognized by the National Accreditation Recognition (NAR) Committee of IOHA. The IH/OH practitioner performs tasks requiring significant knowledge and skill in the IH/OH field, such as conducting worker exposure monitoring and, in some cases, may even function independently of a professional IH/OH but may not be involved in the breadth of IH/OH practice nor have the level of responsibility of a professional IH/OH certified by examination.
The IH/OH practitioner requires a certain level of education that can be obtained from an accredited university or equivalent. Additional training in specific skill sets that provide additional career paths to the IH/OH practitioner can also be obtained. IH/OH practitioners may also serve as team leaders or project managers.
Was this session organized by an AIHA Technical Committee, Special Interest Group, Working Group, Advisory Group or other AIHA project Team?
No
Are worker exposure data and/or results of worker exposure data analysis presented?
No
How will this help advance the science of IH/OH?
Improve detection limits of methylene chloride, simplify and reduce the cost of sample preparation, and reduce environmental waste.
What level would you consider your presentation content geared towards?
Intermediate: Specific topics within a subject. The participant would have two (2) to ten (10) years experience in industrial hygiene or OEHS and a good understanding of the subject area, but not of the specific topic presented. Prerequisites required: another course, skill, or working knowledge of the general subject.
Have you presented this information before?
No
I have read and agree to these guidelines.
Yes