Soils associated with industrial operations such as landfills, manufacturing facilities, and the intensive use of agricultural chemicals can be prone to heavy metal accumulation.
Toxic heavy metals such as lead, arsenic, cadmium, and mercury can accumulate in soil, where they are absorbed by crops and plants. As a result, consumption of these crops inevitably leads to heavy metal exposure1.
Determining soil health and compatibility for plant growth and animal grazing is an important step to ensure heavy metals do not bioaccumulate. Two ways to determine heavy metal contents in soil are the use of analytical spectroscopy techniques such as Atomic Absorption Spectroscopy (AAS) and Inductively Coupled Plasma (ICP). These techniques analyze heavy metals suspended in aqueous solution and have very sensitive detection limits.
To ensure separation of heavy metals in complicated matrices such as soil and other soil constituents, a digestion step is required before spectroscopy. Soil samples are subjected to boiling temperature of 95 °C ± 5 °C using strong oxidizers such as Nitric Acid, Hydrochloric Acid and 30% Hydrogen Peroxide (US EPA Method 3050 B)2. Volatilization of oxidizing agents can corrode metallic surfaces; thus, acid and peroxide digestions require caution when using metallic or ceramic heating blocks with metal components.
The Mars 320 Graphite Hotplate is a laboratory heating device specifically designed for acid digestion in environmental testing. Its graphite heating block provides uniform heat distribution and excellent chemical resistance, making it ideal for harsh digestion conditions. Due to the precise temperature control, it allows users to set and maintain the exact temperature required for digestion protocols, over digestion and sample loss from effervescence and overboiling is prevented. Stable heating ensures each sample is subjected to the same temperature conditions. This is crucial for consistent results and accuracy when doing batch analysis.
Compatibility with Digestion Vessels: The design incorporates a graphite block capable of holding multiple sample tubes or vessels, enabling laboratories to increase throughput by digesting several samples simultaneously. The graphite block is typically removable and interchangeable to accommodate different tube sizes and capacities
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Robust Construction and Safety Features: Built with corrosion-resistant materials (graphite and coated housing), the Mars 320 Graphite Hotplate withstands acidic fumes and spills. It includes safety measures such as over-temperature protection and thermal insulation to protect users and maintain safe operation.
Streamlining heavy metal analysis with consistent digestion and resistance to corrosive chemicals, the Mars 320 Graphite Hotplate is ideal for soil testing and regulatory compliance in drinking water. It boosts throughput, ensures reliable results, and promotes a safer lab environment, making it a trusted choice for demanding screening program.
References:
- Witkowska D, Słowik J, Chilicka K. Heavy Metals and Human Health: Possible Exposure Pathways and the Competition for Protein Binding Sites. Molecules. 2021 Oct 7;26(19):6060. doi: 10.3390/molecules26196060. PMID: 34641604; PMCID: PMC8511997.
- EPA Method 3050B – Acid Digestion of Sediments, Sludges, and Soils. U.S. Environmental Protection Agency
Accurate membrane testing starts with a clean, properly conditioned membrane.
Whether working with ceramic membranes or flat sheet membranes, pre-conditioning is a critical first step. It removes residual particulates and surface residues that can interfere with initial performance measurements, ensuring that test results reflect the true capabilities of the membrane rather than artifacts from contamination.
Sterlitech emphasizes preconditioning as a best practice, particularly when addressing unexpected behavior in permeability or flow rates during testing. Skipping this step may result in inaccurate baseline readings, impaired performance, and misdiagnosis of membrane behavior.
Unexpected Permeability Outcomes
Membrane systems are typically expected to demonstrate predictable relationships between their structural properties and filtration performance. When observed results deviate from these expectations, a common underlying cause is fouling or obstruction by particulates that accumulate on the surface or within the membrane structure.Ceramic membranes are susceptible to this issue due to residual particulates left over from the sintering or machining process. Flat sheet membranes may carry handling residues, process additives, or surface-bound particles that also interfere with initial wettability and performance.
Standard Pre-Condition Protocol for Membranes
Prior to any performance testing, membranes should undergo a system rinse to remove surface and internal contaminants. This is critical for achieving reproducible flux data and accurate characterization.
Recommended Procedure:
- Fill the system with clean water (preferably DI or high-purity feed).
- Activate the permeate circulation or feed pump to initiate full flow through both permeate and retentate channels.
- Discharge all flow to waste until the effluent is visibly clear and free from debris.
This flushing step conditions the membrane, stabilizes its pore structure for testing, and helps avoid misleading permeability readings due to obstruction or uneven wetting.
Implementing a pre-condition protocol is a simple but highly effective quality control measure that eliminates variables before they enter your data set. It ensures membranes are clean, conditioned, and ready to provide reliable performance data from the outset.
Still have questions? Ask an Expert for additional support and guidance.
Membrane flat sheet test cells and housings are essential tools in research and development laboratories.
They allow researchers to quickly gather data on rejection, flux, and fouling behavior, helping accelerate membrane development and application testing.
In Sterlitech’s test cells, the permeate tube plays an important role in directing permeate into collection vessels such as beakers or graduated cylinders. Proper handling is essential not only for consistent system performance and accurate test results, but also for preserving the integrity of high-value permeation processes where precision and reliability are critical.
Here are three best practices to make permeate tube handling easier and more reliable:
- Secure the Tubing with a Clamp: Using a lab-grade or heavy-duty clamp—such as a trigger clamp—helps hold the permeate tube against a rigid frame. This ensures the outlet stays directed into the beaker, minimizing the risk of spills or misalignment. Pro tip: A handheld heater can be used to reshape the tubing for better positioning into the collection vessel.
- Use a 90-Degree Elbow Fitting: When test cells are mounted high on a skid system, routing the permeate line straight down can be tricky. A 90-degree elbow fitting diverts the flow sideways, making tube management simpler and reducing stress on the tubing.
- Consider Flexible Tubing Alternatives: Rigid polypropylene tubing (¼" OD in flat sheet cells, ⅜" OD in 1812 housings) is standard and chemically resistant—but it can be hard to maneuver. For greater flexibility, consider swapping it with Tygon or other lab-grade tubing. Reminder: Always verify chemical compatibility before replacing tubing.
Strengthening Your Workflow
Though minor, the permeate tube plays a critical role in the successful operation of membrane test cells. Taking a few minutes to secure or adapt tubing improves efficiency, prevents contamination, and ensures accurate test results.
