Special Issues
The US EPA monitors a variety of chemicals in water that may cause harm to humans or wildlife to minimize exposure.
Zoe Grosser*, Alicia Cannon*, Michael Ebitson*, Melissa Lever*, Nic Rasnake†, Jessica Bowker†, Allen Fuller†, and Chris Johnson†, *Horizon Technology, and †ESC Lab Sciences
The US EPA monitors a variety of chemicals in water that may cause harm to humans or wildlife to minimize exposure. Method 625 was developed by the Office of Science and Technology in the Clean Water program to allow the monitoring of a large suite of semivolatile chemicals in wastewater for compliance with the National Pollution Discharge Elimination System (NPDES). NPDES is a system of permitting that defines the characteristics of water that is released into a waterway, defined by industrial category. The permitting levels are set depending on the waterway’s use. If the waterway is used for recreation or is an important wildlife habitat, the limit may be set lower.
The original method was developed in the early 1980s and has been updated several times since then to allow the use of more modern technology. The latest update has taken place over the last few years and was proposed in a Method Update Rule (MUR) in 2015 (1). The latest version of the method includes a larger suite of analytes (up to 364) and an extensive set of labeled surrogates to better monitor the method performance throughout the sample preparation and analysis step.
This application note will present the data collected as part of the demonstration of disk solid phase extraction validation for US EPA Method 625.1. Nine different wastewater matrices were evaluated and tested against the criteria listed in Table 6 of Method 625.1. Sample preparation was performed using the Atlantic® One-pass system, where the water sample is passed through a solid phase extraction (SPE) disk and carbon cartridge once, rather than twice with a pH change between loadings. Automation of the process was achieved using the SPE-DEX® 4790 system (superseded by SPE-DEX 5000). Table I shows method detection limits obtained in this work for selected compounds, compared with detection limits listed in the method. In most cases, the method detection limits are significantly better than those obtained using liquid-liquid extraction and older technology. Results for complex samples were also excellent and are detailed in the full application note (2).
References
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Getting accurate IR spectra on monolayer of molecules
April 18th 2024Creating uniform and repeatable monolayers is incredibly important for both scientific pursuits as well as the manufacturing of products in semiconductor, biotechnology, and. other industries. However, measuring monolayers and functionalized surfaces directly is. difficult, and many rely on a variety of characterization techniques that when used together can provide some degree of confidence. By combining non-contact atomic force microscopy (AFM) and IR spectroscopy, IR PiFM provides sensitive and accurate analysis of sub-monolayer of molecules without the concern of tip-sample cross contamination. Dr. Sung Park, Molecular Vista, joined Spectroscopy to provide insights on how IR PiFM can acquire IR signature of monolayer films due to its unique implementation.