As regulations addressing target semi-volatile organics in soil matrices continue to push for increasingly lower action levels, laboratories are required to examine preparation workflows to optimize the rate-limiting steps in sample preparation. This need, combined with a focus on safety, health, and cost reduction, drives the adoption of the Milestone Total Workflow solution for sample preparation.
Image Credit: William Edge/Shutterstock.com
Extraction methods, including sonication (prohibited for PCB as of Feb 2024), Soxhlet, and pressurized fluid extraction (PFE) pose various challenges related to safety, quality, productivity, reliability, and cost. Milestone’s Total Workflow solution integrates solvent handling, sample extraction, and sample filtration, while also preventing cross-contamination, all with a small footprint that frees up valuable hood space.
Samples are weighed and dried using a drying agent, transferred to disposable glass inserts, and treated with surrogates and spikes where appropriate. The solvent system is automatically added to each vessel, which is then transferred to a microwave vessel for extraction following EPA SW-846 method 3546.
The components of the Milestone Total Workflow Approach for Organics extractions of soils for Semi-Volatile Organics (BNA, pesticides, PCBs, TPH-DRO, etc.) include three primary components:
1. Automated solvent addition
- Reduces solvent exposure
- Frees up hood space
- Ensures consistent volume (+1% accuracy)
- Adaptable to any vessel size
- Inert design prevents cross-contamination
- Accommodates up to six solvents
- Software-driven for ease of use
2. Microwave extraction
- 30-gram sample size enhances RLs
- 40 minutes to process 24 samples from start to finish
- Disposable glass inserts eliminate the need for cleaning and prevent cross-contamination
- Documents each sample extraction
3. Extract filtration
- Simultaneous filtration of 24 extracts
- Filters through sodium sulfate and a 0.45 u filter
Discussion
Most laboratories dedicate substantial time and resources to optimizing analysis techniques, such as GC/MS and GC/ECD. Greater emphasis is needed on the preparation processes to alleviate bottlenecks in sample preparation, such as extractions.
Prioritizing employee health and safety is crucial to any workflow for organic extractions. Reducing exposure to methylene chloride and other solvents is gaining importance as EPA and OSHA focus more on methylene chloride use limitations.
Image Credit: Milestone S.r.l.
OSHA enforces stringent protocols for methylene chloride users, including detailed plans and monitoring requirements. When combined with state regulations targeting methylene chloride emissions from laboratory fume hoods, this necessitates a reduction in laboratories’ methylene chloride footprint.
The Milestone Total Workflow approach helps laboratories reduce solvent consumption and associated risks, improve productivity, and process samples more cost-effectively and timely.
This workflow approach is illustrated below:
Figure 1. Sample workflow. Image Credit: Milestone S.r.l.
Experimental - Solvent addition
The easyFILL system automates solvent addition to vessels, safely and accurately (+1%). The Microwave Extraction system ensures efficient and secure sample extraction, while the Sample Filtration System efficiently filters extracts. When handling solvent systems for organic extractions, most labs utilize 1:1 methylene chloride:acetone or 1:1 hexane:acetone. The handling of these solvents poses a challenge due to the volumes required to add to any solvent extraction protocol.
The Milestone easyFILL system delivers solvents with safety and precision (+1%) either individually or as mixtures (0.5 to 50 mL) to any standard extraction vessel. The racks provided come in various configurations and can accommodate all manufacturers' most common extraction vessels. Solvent fumes are vented through a 4” OD exhaust hose into a fume hood.
Proven advantages include:
- Reduced handling time
- Increased safety
- Enhanced laboratory efficiency
Figure 2. easyFILL automatic reagent dosing station. Image Credit: Milestone S.r.l.
Experimental - Microwave extraction
Microwave technology offers a cost-effective, safe, and reliable method for soil extractions of extractable organics by EPA SW-846 method 3546.
Milestone systems are utilized in over 500 laboratories worldwide for organic extractions. By enabling temperature and pressure monitoring in each sample vessel throughout the extraction process, recoveries of BNA compounds, PCBs, and pesticides, among others, meet or exceed EPA method requirements (EPA 8000d and EPA 3546) and comply with TNI/NELC and state assessments.
These studies were conducted using a Milestone ETHOS X equipped with a fastEX-24 rotor benchtop microwave extraction system, fully compliant with US EPA 3546. The fastEX-24 rotor uses 145 mL vessels with 100 mL disposable glass vial inserts. These vessels allow 30 grams of sample to be extracted, meeting reporting limit requirements.
Figure 3. ETHOS X with fastEX-24 rotor. Image Credit: Milestone S.r.l.
With Milestone’s patented Weflon technology and contactless temperature control in all positions, the fastEX-24 rotor enables the extraction of 24 samples simultaneously, ensuring uniform temperature across all samples and exceptional analyte recovery.
Built-in methods and application notes provide unparalleled ease of use and low operating costs compared to all currently approved extraction techniques.
All application notes detailing the recoveries of BNA, PCBs, pesticides, and other extractables are available. The following table summarizes these recoveries.
Table 1. Recovery ranges by Analysis Group-reflects all typical compounds reported by Environmental Labs. Source: Milestone S.r.l.
| TYPE OF ORGANIC |
RECOVERY RANGE |
PRECISION-% RSD |
| BNA -8270 list |
69 - 118% R |
4.0 - 14.9 |
| Pesticides- 8081 list |
79 - 120% R |
1.3 – 10.6 |
| PCBs -8082 list |
75 – 115% R |
0.2 – 8.3 |
| TPH-DRO (C10-C28) |
89 – 105% R |
2.4 – 5.2 |
This data demonstrates outstanding recoveries and precision from both CRMs and Blank Spikes in soil matrices due to the design and workflow of the Milestone systems.
Figure 4. Contactless temperature control in each vessel and documentation of each vessel extraction profile downloadable as .xls, .cvs and .pdf for Batch back-up. Image Credit: Milestone S.r.l.
Greater return on investment
The competitive nature of the environmental analysis market requires today’s laboratories to adopt innovative solutions for faster turnaround times. With the capacity to process 24 samples in just 40 minutes, the ETHOS X, equipped with the fastEX-24eT, reduces overall analysis costs by boosting productivity.
Lower solvent volumes, reduced maintenance needs, and the use of cost-effective disposable glass vials further reduce the cost per sample, improving laboratory competitiveness and profitability.
Table 2. Comparison of extraction techniques. Source: Milestone S.r.l.
*Including: solvent - handling - time - productivity - maintenance
Experimental - Extract filtration
The final stage prior to extract concentration involves filtering and rinsing the contents of the extract disposable vial into an evaporation vessel (50 mL or 200 mL, or another size suitable for the system). Some laboratories use N-EVAP™ systems, while others prefer TurboVap™ systems.
Only a few laboratories continue to rely on Kuderna-Danish concentration techniques. In all instances, the total solvent volume from microwave extraction and rinsing remains under 50 mL. This accelerates the concentration process considerably and improves recoveries, as the concentration cannot proceed for a prolonged period.
In cases where solvent exchange is required (e.g., from methylene chloride to hexane), lower-volume microwave extraction saves time because the smaller amount of solvent is exchanged.
The Milestone SFS-24 automated filtration system simultaneously filters 24 extracts through anhydrous sodium sulfate and a 0.45 u filter (or another size, as needed) into the concentration vessel. This process, conducted within a hood using vacuum assistance, completes filtration and rinsing in just a few minutes. The reservoirs and filters serve as low-cost consumables.
Figure 5. SFA-24 automated filtration system. Image Credit: Milestone S.r.l.
Conclusion
The Milestone Total Workflow approach to extractions offers laboratories substantial benefits ranging from cost savings, performance metrics, risk management, and other KPIs.
Image Credit: Milestone S.r.l.
Total workflow solution: Why does it matter?
- Ability to do more with less
- Increased sample capacity for varying workloads
- Ability to improve and predict turnaround times, with the flexibility to handle rush work
- Enhanced data quality
- Ease of use and workflow implementation ensures seamless onboarding for new staff
- Risk reduction for laboratory personnel through the easyFILL Reagent dosing station and the use of reduced solvent volumes
About Milestone S.r.l.
Milestone was established in 1988 as the first specialized laboratory instrument manufacturer focusing on advanced microwave technology for sample preparation. Today we hold over 50 patents and have over 20,000 global users spanning across government, academic, contract, and manufacturing industries. Milestone’s headquartered is in Italy with offices in the Unites States, China, Japan, and Korea. The R&D and manufacturing sites are in Germany (MLS) and Switzerland (MWS), along with the offices for Austrian, German and Swiss markets. We have grown as advanced microwave technology manufacturer operating worldwide through a network of over 100 exclusive distributors, all providing our customers premium application and service support.
The key to Milestone’s technological leadership lies in bringing together individuals from diverse scientific and engineering disciplines to solve real world problems with innovative microwave instrumentation. The excellent support of the Application Team through all these years has highly contributed to the success of our laboratory instruments and our company. All our products are manufactured, assembled and checked by Milestone Production Department according to ISO procedures, to ensure they fully satisfy the needs of our customers.
Milestone has UNI EN ISO 9001:2015 certification representing international standards for quality management in TÜV Rheinland - a global, multi-accredited organization accepted by the majority of the world.
This information has been sourced, reviewed and adapted from materials provided by Milestone S.r.l..
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