How Chromatography is Helping Address Pollution in the Colorado River


An examination of how chromatography could be used to solve the water crisis in the American southwest.

The American southwest is home to some of the United States most beautiful natural wonders. From Monument Valley to the Grand Canyon, the geographical landscape of the American southwest has amazed locals and visitors for centuries.

One of the most important natural resources is the Colorado River. Originating in the Rocky Mountains, the river is responsible for helping to form the Grand Canyon a millennia ago and serves as a valuable resource to living organisms, providing water for drinking and irrigation, and sustaining ecosystems.

Colorado River Arizona | Image Credit: © Paul Moore -

Colorado River Arizona | Image Credit: © Paul Moore -

But right now, the Colorado River is facing numerous challenges, including pollution, climate change, and a declining water table. Although the region did encounter a wet year in 2023, the Colorado River basin reservoirs remain very low (1). The Colorado River flow has decreased approximately 20% compared to the early 20th century (2). As a result, seven Western states (Colorado, New Mexico, Utah, Wyoming, Arizona, Nevada, and California) that rely heavily on the Colorado River have prioritized coming up with a solution to the water supply problem.

“We must plan for the river we have – not the river we dream for,” Becky Mitchell, Colorado’s commissioner to the Upper Colorado River Commission, said in a statement to CNN (2).

Analytical techniques like liquid chromatography (LC) have played an important role in helping to address some of these challenges over the years (3–6). For example, ultrahigh-pressure liquid chromatography (UHPLC) was used to analyze organic contaminants in water sources (6).

Solving the drought crisis in the American southwest is a multifaceted issue. However, with water resources being limited, it is important that the available water supply is used efficiently with minimal to no waste. As a result, the monitoring of the water quality and identifying contaminants is important in this effort, and that is where chromatography can play a key role.

Lee Blaney, a professor at University of Maryland – Baltimore County, explained that resource recovery is one way scientists can help mitigate this growing problem.

“Once we send our wastewater effluent back into the river and send it downstream, we lose it,” Blaney said.

A Declining Water Table

The Colorado River is lower than it ever has been. This reality has significant ramifications for the southwest United States to flourish. With reservoirs being nearly empty, even large runoffs would not replenish capacity levels (7). The long-term solution for replenishment of the Colorado River basin would require significant reduction in the average consumption of water.

To tackle the drought crisis in the American Southwest, a multifaceted approach is required, including but not limited to:

  1. Implementing water conservation measures such as efficient irrigation techniques, fixing leaks in water distribution systems, and promoting water-saving technologies.
  2. Exploring alternative water sources such as desalination, rainwater harvesting, wastewater recycling, and groundwater recharge.
  3. Developing sustainable water management policies, fostering collaboration among stakeholders, and addressing water rights issues.
  4. Taking steps to mitigate climate change through reducing greenhouse gas emissions and adapting to the changing climate by implementing resilient infrastructure and land use planning.
  5. Educating the public about the importance of water conservation, sustainable water use practices, and the impacts of climate change on water resources (6).

Although chromatography may not directly solve the drought crisis, it can play a role in monitoring water quality and identifying contaminants, which is essential for ensuring the sustainability and safety of water resources in the region.

“LC–MS methods are going to be key to making sure that we can properly quantify CECs in wastewater, so that when we're going through all of our treatment for water reuse purposes, we're shortening that kind of pipeline (from wastewater to drinking water), so that we can really make sure that we're safeguarding our consumers downstream that are actually drinking the water,” Blaney said.

Below are a sampling of some studies using chromatography that have helped address pollutants, and other issues, in the Colorado River.

Limiting Industry Impact on the Colorado River

Many environmental contaminants originate from industry plants, which produce copious amounts of toxic waste. Bioactive chemicals have adverse effects on the water supply, threatening the ecosystem and contaminating the water supply. In one study conducted near, Moab, Utah, researchers analyzed wastewater treatment plant (WWTP) outflow and found the presence of pharmaceuticals, hormones, and biological activities associated with estrogen-receptor (ER), glucocorticoid receptor (GR), and peroxisome proliferator activated receptor-gamma (PPARγ) using high performance liquid chromatography (HPLC) and LC–tandem mass spectrometry (LC–MS/MS) (3). The aim was to evaluate the effects of replacing the WWTP on the concentrations of these bioactive chemicals (BCs) (3). Overall, the results of the study indicated that replacing the Moab WWTP led to a significant reduction in bioactive chemical concentrations in the Colorado River, suggesting a positive impact on water quality (3).

Arches National Park, right by Moab Utah, the location of this study. | Image Credit: © Josemaria Toscano -

Arches National Park, right by Moab Utah, the location of this study. | Image Credit: © Josemaria Toscano -

Using LC–ESI–ITMS to Analyze Contaminants Along the Colorado River Basin

In another study, scientists collected water samples from the Colorado River Basin across five western states and analyzed them using liquid chromatography-electrospray-ion trap mass spectrometry (LC-ESI-ITMS). The goal of this study was to assess the presence of emerging contaminants in the Colorado River, which included drugs and personal care products (4).

The researchers used both grab sampling and polar organic chemical integrative samplers (POCIS) to collect water samples from waste stream tributaries and receiving surface waters. Samples were analyzed using LC-ESI-ITMS. Estrogenic chemicals were screened using the yeast estrogen screen (YES) assay on POCIS extracts from the Las Vegas Wash. Azithromycin, methamphetamine, and pseudoephedrine were among the detected ECs, with concentrations varying temporally (4). Most ECs detected in main surface water channels were near or below detection limits, with azithromycin being the most found contaminant in urban waste streams (4).

Detecting AEOs and APEOs in the Colorado River Using SPE and LC–MS/MS

In a study published in the Journal of Chromatography A, researchers from the United States Environmental Protection Agency (EPA) developed a method for detecting alcohol ethoxylates (AEOs) and alkylphenol ethoxylates (APEOs) in water samples using solid-phase extraction (SPE) and LC–MS/MS (5).

The methodology the researchers used allowed them to analyze 152 analytes in approximately 11 min, detecting ethoxymers with 2–20 ethoxy units (5). Detection limits were as low as 0.1 pg injected but increased with higher ethoxy units. Ethoxymers with 3–5 units were most sensitive, while those with over 15 units had the least response. Recovery rates varied (37–69%) with alkyl chain length. C14–18 ethoxylates showed significant degradation. Analysis of Colorado River water revealed predominant APEOs, mainly octylphenol and nonylphenol ethoxylates, with concentrations over 100 ng/L in some samples. Other AEO homologues were also found but at lower levels (<50 ng/L).

UHPLC–MS/MS Analysis of Organic Compounds in the Colorado River

Another study discusses the contamination of water sources by organic compounds and the development of a method to analyze them. These compounds, found in products like pharmaceuticals, pesticides, and personal care items, often end up in wastewater and can impact aquatic life. Since many of these compounds aren't regulated in water treatment processes, monitoring them is important until more data on their human health effects is available.

A new method was developed using solid phase extraction and ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) to analyze 36 trace organic contaminants (6). This method, which employs both positive and negative electrospray ionization, offers high sensitivity and reduces analysis time to less than 20 minutes (6).

The method's detection limits are very low, and it was successfully tested on various water matrices, including wastewater, groundwater, surface water, and drinking water. Sucralose and TCPP were among the compounds found in wastewater at the highest concentrations (6). Overall, the proposed method is sensitive, fast, and reliable, making it suitable for analyzing a wide range of trace organic compounds in different water sources.


(1) Gilbert, L. Crisis on the Colorado: New Analysis Charts Hard Choices for a Drying River. Utah State University. Available at: (accessed 03-09-2024).

(2) Nilsen, E. With New Plans, Colorado River States Draw Battle Lines Over Who Should Bear the Brunt of Future Water Cuts. Available at: (accessed 2024-04-11).

(3) Cavallin, J. E.; Battaglin, W. A.; Beihoffer, J.; et al. Effects-Based Monitoring of Bioactive Chemicals Discharged to the Colorado River Before and After a Municipal Wastewater Treatment Plant Replacement. Environ. Sci. Technol. 2021, 55 (2), 974–984. DOI: 10.1021/acs.est.0c05269

(4) Jones-Lepp, T. L.; Sanchez, C.; Alvarez, D. A. Point Sources of Emerging Contaminants Along the Colorado River Basin: Source Water for the Arid Southwestern United States. Sci. Total Environ. 2012, 15 (430), 237–245. DOI: 10.1016/j.scitotenv.2012.04.053

(5) DeArmond, P. D.; DiGoregorio, A. L. Rapid Liquid Chromatography–Tandem Mass Spectrometry-based Method for the Analysis of Alcohol Ethoxylates and Alkylphenol Ethoxylates in Environmental Samples. J. Chromatogr. A. 2013, 1305, 154–163. DOI: 10.1016/j.chroma.2013.07.017

(6) Anumol, T.; Merel, S.; O Clarke, B.; Snyder, S. A. Ultra High Performance Liquid Chromatography Tandem Mass Spectrometry for Rapid Analysis of Trace Organic Contaminants in Water. Chem. Central J. 2013, 7, 104. DOI: 10.1186/1752-153X-7-104

(7) Schmidt, J. C.; Yackulic, C. B.; Kuhn, E. The Colorado River Water Crisis: Its Origin and the Future. WIREs Water 2023, 10 (6), e1672. DOI: 10.1002/wat2.1672

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