Metal Emissions Testing with US EPA Method 29
US EPA Method 29 ensures metal emissions from industrial smokestacks meet state-specific limits to protect the environment. As the limits for specific elements decrease over time, achieving decreased instrument detection limits becomes crucial for a laboratory’s success.
There are seventeen US EPA scope elements: Antimony, Arsenic, Barium, Beryllium, Cadmium, Chromium, Cobalt, Copper, Lead, Manganese, Mercury, Nickel, Phosphorus, Selenium, Silver, Thallium, and Zinc.
The method allows for the analysis of all metals (excluding mercury) through either inductively coupled plasma optical emission spectroscopy (ICP-OES) or inductively coupled plasma–mass spectroscopy (ICP-MS) testing.
Though labs aim for the lowest detection limits, some opt for ICP-MS due to its low sensitivity. However, modern ICP-OES instrumentation advancements allow equal or lower detection limits for certain elements. ICP-OES facilitates direct analysis of both front and back half fractions with its concentrated acid preparation, while ICP-MS requires a diluted solution, which increases the instrument detection limit.
Choosing the best analytical method: ICP-OES vs. ICP-MS
The most frequent inquiry received in our lab pertains to the optimal methodology for sample analysis, for which there is no definitive answer. For samples with heavy particulate matter, starting with ICP-OES analysis is recommended. If lower detection limits are needed, follow up with ICP-MS analysis. Conversely, for cleaner samples, begin with ICP-MS analysis, and if any element shows higher values, perform further analysis using ICP-OES.
Continuous evaluation of ICP-OES and ICP-MS conditions is essential. Updating the plasma conditions can enhance the efficiency of running more acidic solutions through the plasma and minimize background interferences. Regularly assessing plasma conditions allows laboratories to make simple adjustments over time, leading to a lower detection limit.
How Mercury is analyzed differently: CVAA
Mercury analysis employs cold vapor atomic absorption (CVAA) as the method. In this process, samples are introduced to a reductant, which converts the inorganic mercury into a gas. The gas is then passed through a cell and compared to a reference cell containing no mercury, allowing for the determination of the total mercury content in the solution.
CVAA is a highly sensitive instrument, with a method detection limit of 50 parts per trillion, far surpassing the capabilities of ICP-OES and ICP-MS, which can evaluate solutions in low parts per billion. Due to its toxic nature and the strict requirements for mercury analysis make CVAA the ideal choice for Method 29 runs.
This instrument exhibits robustness, and its sensitivity remains unaffected by acid content. As a result, it can handle a wide range of samples, from clean to those with high particulate matter. The only exception is samples containing elevated copper concentrations, which need to be at the percentage level to impact the analysis—a scenario not typically encountered in routine testing.
Our experienced professionals, who possess a deep passion and expertise in metals analysis, can confidently help you navigate the complexities of US EPA Method 29 analysis, contributing to a cleaner and safer environment for all. For more information, connect with one of our experts.