LC-MS-MS and GC-MS for Water Quality Monitoring
Saptashati “Tania” Biswas is a postdoctoral research scientist at the National Center for Water Quality Research, which is based at Heidelberg University in Tiffin, Ohio
Saptashati “Tania” Biswas is a postdoctoral research scientist at the National Center for Water Quality Research, which is based at Heidelberg University in Tiffin, Ohio. She received her BSc at the University of Calcutta, MSc at the University of Kalyani, and PhD at the University of Maryland, College Park. Her primary research focus is on analytical method development of environmental contaminants such as pesticides, insecticides, antimicrobials, and other chemicals of emerging concern.
Q: What does your laboratory do?
A: Our lab has two major goals, which are monitoring and researching chemicals in the Lake Erie watershed and beyond. We are a leader in surface and groundwater research and monitoring, and our mission is to promote the sustainable use of water and soil resources while striving to protect ecosystem integrity. Whatever we do is basically surrounding this whole mission of sustainability, and understanding the use and changes in the management practices of these chemicals.
Q: What do you use mass spectrometry for in your work?
A: Mass spectrometry (MS) is used in inductively coupled plasma (ICP-MS) for doing metal analysis in groundwater and well water. Our gas chromatography-mass spectrometer (GC-MS) is a Varian [now Agilent] and is used for our pesticide monitoring program, which started in the 1980s and now monitors more than 20 pesticides. Our suite of pesticides includes triazines, acetanilides, organophosphates, dinitroanilines, and carbamates. We are using our liquid chromatography-triple quadrupole mass spectrometer (LC-MS-MS) to develop new techniques for measuring glyphosate and acid herbicides. These are the newer pesticides that are of great interest and have not been extensively monitored in the Great Lakes watershed.
Q: Can you tell me a bit more about that LC-MS-MS work?
A: The major focus is developing research projects around the new glyphosate and acid herbicide methods. We don’t just measure these compounds like other analytical labs would do, we do research based on the data. So, we develop hypotheses and objectives, and write proposals to get grant money to do research. For example, for the glyphosate method that we are developing right now, we are trying to analyze trends based on the precipitation patterns in this area and compare different types of watersheds. So, there’s an environmental and watershed management aspect to whatever chemical analysis we do. Similarly, we are doing comparisons with acid herbicides, which are also present in this area. Our research projects are focused on developing these methods on the LC-MS-MS, and then answering questions related to water management and water-related issues and understanding concentration and loading. Glyphosate is a tricky compound to measure; it’s a very polar compound so there is no specific column that has worked for everyone. For us, we have to have a very high-throughput method because we analyze hundreds of samples per year. We produce a lot of data, so we are not interested in derivatization and doing complicated methods with complicated workflows. At this point, we are trying to figure out the shortest method we can use for QA/QC. We’re working on improving the workflow and making it faster.
Q: How do you go about developing methods for your work?
A: When developing a method, first we decide which compounds we are going to target. How important are they and what research projects can be developed around the method development? After selecting our analyte(s) of interest, we study its chemical properties and research suitable LC-MS conditions. In a multiresidue method, we can analyze different chemicals simultaneously and that saves a lot of time. We initially wanted to make the glyphosate method a multiresidue method, but unfortunately glyphosate has its own chemistry. So, we first figured out what kind of MS conditions it would need, then did the MS optimization and went to the LC. We test out different kinds of columns and select the best column that will give us good separation and resolution. We also optimize other important LC parameters, such as mobile phases, internal standards, flow rates, and injection and wash volumes—all the usual LC-MS parameters.
Q: What is most important in developing those methods?
A: Because we are producing a lot of data, the most important thing is how to minimize the time and have a high-throughput method. For example, for glyphosate we already have a method that will work, but it requires several extra steps and we don’t want to spend that much time for every sample because we have a large volume of samples coming through. So, there are always challenges—how do we reduce these steps, is there a column that will help us extract or separate these chemicals without having them go through all these steps? We always try to see how we can save on time and chemicals.
Q: What recent trends in mass spectrometry have you seen?
A: I see many labs having diverse needs of instruments as they are analyzing different suites of chemicals. So, we have a front-end that is the chromatography part—LC, GC, or IC—and then we have the back end that is the mass spectrometry part, which is a triple quad, time-of-flight, or an ion trap mass spectrometer. Scientists are experimenting with switching around the front-end and the back end, depending on which compound they are analyzing. For example, if they have an LC front-end, they will try to switch that with IC, so they can analyze a different class of compound or do a different kind of experiment. Not every instrument can be switched around, but this kind of capability is increasing to give MS a more versatile application. And there are also newer columns that are always being developed, especially for polar compounds. Ten years ago, we had to derivatize almost every compound and now we can do a straightforward analysis without going through all these derivatizations because [of the] newer columns and compatible extraction cartridges.
Q: What are the key challenges you face in your work?
A: There are always maintenance problems. Unlike simple instruments [such as] spectrophotometers, [mass specs] need a lot of maintenance because they are very sensitive, in that we are analyzing compounds that are at partsper- billion or parts-per-trillion levels. The room has to be really clean, and if there is some kind of an incompatible buffer that is introduced by error, then it’s a problem. There are certain ions we don’t ever want to introduce into the mass spec, because you cannot clean out the inside of the mass spec very easily. It requires technical help. Therefore, when we are developing a method, we are very conservative in using the mobile phases.
Q: What are some of the plans for your lab’s future?
A: One of the things we did recently is purchase our LC-MS-MS to analyze new classes of compounds that we weren’t measuring before. After completing the glyphosate and acid herbicide projects, we plan to develop methods for microcystins. A microcystin is an active toxin in harmful algal blooms. We are in the Great Lakes watershed, and the Western Lake Erie Basin has a lot of algal bloom problems during the summer. Being in this region, we are always requested to analyze microcystins and that’s not compatible with the current methods. We have one machine, and we have all these different classes of compounds that we want to analyze, so once these projects are done, we would like to analyze microcystins. Apart from that, we also want to buy an accelerated solvent extractor that will improve our sample preparation. Right now, we have cartridges and disks that have to be manually treated and eluted, so there has to be a technician dedicated to both the separation and preparation of compounds.
Q: What advice do you have for those who are just starting in environmental labs?
A: To those who are in the process of setting up a new lab, I would first recommend choosing the companies you are buying your instruments from very wisely, especially the expensive instruments like the GC-MS and LC-MS, because the relationship doesn’t end after buying the instrument. It’s a long-term relationship because these instruments require a lot of maintenance and troubleshooting—especially if someone is new to environmental sample analysis. Having reliable customer support from the company is very, very important. Some companies are very bad with customer service and you will not get any help, and some companies will be so helpful that they will almost act as your partner in the process and help you with the troubleshooting. I would suggest attending relevant scientific meetings, for example, ASMS, where you meet many vendors. Have a good discussion and clear expectation as to how much of their involvement you will need, especially if you don’t have any experience. Not many people consider that—they go with the cheapest instrument, but cheapest is not always the best. You want to use these instruments long-term—at least for five to 10 years—so be wise in choosing which brand you want. I’ve learned my lesson. Now, when I’m buying an instrument, I have so much discussion with customer support and technicians. There are so many companies and it’s a competitive market—the customer has a lot of power; it’s just that we have to realize that it’s in our hands to choose the right brand.