Colorimetric Chemodosimeter for Palladium
Rigorous and iterative purification and analytical processes are necessary to ensure the absence of toxic metals such as palladium in active pharmaceutical ingredients to comply with federal regulations. Palladium catalysis is also used to synthesize organic polymers, including photovoltaic materials, which causes metal contamination that can negatively impact the materials’ performance. Traditionally, trace palladium is quantified using either inductively coupled-plasma mass spectrometry (ICP-MS) or inductively coupled-plasma optical emission spectroscopy (ICP-OES), which are sensitive and robust but expensive, slow, and usually unavailable at production sites. A significant drawback of these methods is a multi-week delay, including sample shipping times, to quantify trace metals. Presented is a method of measuring metals on-site with simple procedures and instruments using a colorimetric method that makes use of a chemosensor that rapidly, reversibly, and autonomously stalls, allowing the user to stop, start, and reverse the reaction, with the ability to detect palladium in concentrations as low as 0.1 ppb.
Description
The colorimetric method for palladium detection employs resorufin allyl ether (RAE) that cleaves to release resorufin in the presence of palladium, shifting the solution color from yellow to purple. Sequential additions of sodium borohydride (NaBH4 ) can quantify palladium concentrations ranging over five orders of magnitude (0.1 ppb-10 ppm), a range rivaling spectroscopic and spectrometric methods. Unlike other methods that continue to deallylate over time, preventing the user from leaving the reaction unattended, the conversion of RAE to resorufin halts autonomously after a period of time dependent on the initial concentration of NaBH4. The reaction can be restarted, allowing users to leave the reaction unattended and collect the same data at any time. While providing similar precision and dynamic range compared to spectroscopic and spectrometric methods, this colorimetric method is comparatively low-cost and can be performed quickly and on-site.Applications
· Quantifying trace palladium in pharmaceuticals, ores, and organic polymers· Compliance with federal regulations to minimize toxic metals in active pharmaceutical ingredients
· Other catalysis-based assays
Advantages
· Less costly than ICP-MS or ICP-OES· Easy to perform on-site
· Reduces sample shipping and processing time
· Does not require constant monitoring
· Autonomously halts in 10-30s, allowing users to inspect the sample at any time, and can be reversed and restarted
· Similar sensitivity compared to other leading methods