The Future of Ion Chromatography | PFAS Testing, EPA 1621 & AOF Explained

How are PFAS regulations changing, and what role will ion chromatography play in the future of environmental testing?

In this episode,  David interviews Jay Gandhi, PhD, Vertical Markets Manager at Metrohm USA, for an in-depth discussion on PFAS analysis, the rise of AOF (Adsorbable Organic Fluorine) testing, and the development of EPA 1621 and ISO 18127 standards.

With more than 30 years of experience in ion chromatography, Jay shares valuable perspective on how the field has evolved—from early applications and NASA water recovery projects to today’s challenges involving PFAS, TFA, and emerging contaminants.

Topics covered in this episode include:

• What PFAS are and why they matter
• The difference between targeted PFAS methods and AOF analysis
• How combustion ion chromatography works
• Behind the scenes of EPA 1621 and ISO 18127 method development
• Regulatory trends in water, textiles, and food packaging
• TFA analysis using IC-MS and IC-MS/MS
• The future of ion chromatography in environmental labs

Video Transcription

For more than three decades, Jay Gandhi has worked with ion chromatography (IC), watching the technique expand from a specialized tool for water analysis into an analytical platform used across environmental testing, food and beverage analysis, semiconductor manufacturing, battery applications, and, increasingly, PFAS analysis.

In an interview for Concentrating on Chromatography, Gandhi discusses his introduction to IC during his work on a NASA Mars exploration project, the emergence of PFAS as a major analytical challenge, and why techniques such as adsorbable organic fluorine (AOF) determination and combustion ion chromatography (CIC) can provide information that targeted LC-MS analysis alone cannot deliver. He also examines the development of standardized methods, sample preparation challenges, and the future role of IC-MS and total fluorine approaches in PFAS monitoring.

From NASA to ion chromatography

Gandhi's introduction to ion chromatography came through his work as a principal scientist on a NASA Mars exploration project focused on water recovery under zero-gravity conditions. IC played an important role because it enabled researchers to establish the ionic balance of anions and cations in water.

The technology was used both to investigate micronutrients relevant to agricultural applications and to evaluate water purity for potential astronaut consumption. During approximately three years of this work, Gandhi gained extensive experience with ion chromatography. This ultimately led him deeper into IC instrumentation and, 24 years ago, to joining Metrohm.

At the beginning of his career, IC was strongly associated with relatively straightforward anion and cation analysis in water. The technique itself had been used for water analysis since the 1970s, but Gandhi has seen its application range expand dramatically.

Food and beverage testing and environmental analysis became important fields, supported by both direct and indirect detection strategies. More recently, IC has also found applications in areas such as the semiconductor industry and battery recycling.

In Gandhi's words, ion chromatography has effectively "bloomed" into numerous application areas.

PFAS changes the analytical challenge

PFAS represent a particularly important chapter in this development. These chemicals have been used for decades in numerous consumer and industrial products, including non-stick materials, firefighting foams, water-resistant textiles and other applications.

Gandhi recalls work on PFOA and PFOS using ion chromatography with conductivity detection as early as 2008. However, the achievable detection limits were insufficient for the extremely low concentrations that later became important in PFAS analysis.

A major turning point for him came in 2015, when he encountered research from Sweden using combustion ion chromatography to investigate total fluorine. Subsequent collaboration with researchers at Clarkson University and Harvard University, particularly on aqueous film-forming foam (AFFF), further demonstrated the importance of looking beyond individual targeted PFAS compounds.

Why targeted LC-MS does not tell the whole story

Targeted LC-MS is highly sensitive and selective and can provide detailed information about individual PFAS compounds. However, according to Gandhi, the number of possible PFAS structures in the environment is vastly greater than the number routinely included in targeted methods.

A targeted method may monitor dozens or perhaps around one hundred compounds, while the overall PFAS universe can include thousands of chemical structures. Consequently, targeted analysis may characterize only a small fraction of the total PFAS burden.

There are other practical considerations. LC-MS measurements can be affected by matrix-dependent ion suppression, while accurate quantification frequently relies on isotope-labelled internal standards. Such standards are available for only a limited number of compounds and can be expensive.

This is where measurements of total or adsorbable organic fluorine can provide complementary information. Rather than asking which specific PFAS compounds are present?, these approaches can help answer a broader question: how much fluorine associated with this chemical space is present in the sample?

AOF as a complementary approach

Adsorbable organic fluorine analysis provides a different perspective from targeted LC-MS. In the workflow discussed by Gandhi, organic fluorine compounds are captured during sample preparation and subsequently measured using combustion ion chromatography.

The principle of CIC builds upon older total organic halogen analysis. The sample is combusted at temperatures above approximately 1,000 °C, breaking carbon-halogen bonds. In PFAS-related analysis, carbon-fluorine bonds are broken and the resulting fluoride is collected in an absorption solution.

Ion chromatography is then used to separate and quantify the fluoride.

Replacing older detection approaches with IC provides both sensitivity and selectivity for the halogens being measured. Effective combustion is critical: oxygen supports the combustion process, while a carrier gas transports the products into the absorption solution for subsequent IC analysis.

The challenge of inorganic fluoride

The broad response of CIC is simultaneously one of its strengths and one of its analytical challenges. Combustion does not distinguish fluorine originating from PFAS from fluorine present in inorganic compounds such as fluoride salts.

This becomes particularly important when analyzing water containing relatively high concentrations of inorganic fluoride while attempting to quantify organic fluorine at very low levels.

Sample preparation therefore has a critical role. Inorganic fluoride must be effectively separated from the fraction of interest, while materials used during sample preparation must themselves have sufficiently low fluoride backgrounds.

Contamination can come from unexpected sources. Gandhi points out that background fluoride may originate not only from reagents and sample preparation materials but potentially from the laboratory environment. Careful blank control, appropriate materials and rigorous evaluation of interferences are therefore essential when moving toward increasingly low detection limits.

From research method to international standardization

The development of standardized AOF methods illustrates the importance of collaboration between academia, industry, regulatory organizations and analytical laboratories.

Gandhi describes work that began in Europe around 2015 and subsequently progressed through German standardization activities, ISO development, ASTM-related collaboration and the U.S. EPA. The process eventually contributed to methods such as EPA Method 1621.

He emphasizes that this was not the work of a single scientist or organization. Developing a robust method required years of experiments, discussions and sometimes difficult technical debates among numerous stakeholders.

For Gandhi, the essential principle was that experimental evidence ultimately had to determine the outcome. Collaboration becomes possible when scientists focus on the data rather than the organizations they represent.

PFAS monitoring is moving beyond drinking water

Regulatory attention to PFAS is also expanding beyond drinking water. Gandhi describes a broader strategy that begins with reducing the manufacture and use of PFAS-containing materials and continues with removing existing contamination from the environment.

Wastewater represents an important part of this picture because PFAS can enter it from numerous sources. Historical contamination from landfills and contaminated sites can also migrate into groundwater and ultimately affect drinking-water supplies.

Consumer products are another area of increasing attention. Food packaging, disposable containers, automotive fabrics, outdoor clothing and water-repellent textiles have historically used fluorinated substances to provide properties such as grease, water or stain resistance.

Reducing PFAS use in such products could therefore gradually decrease the amount entering waste streams and the wider environment.

Screening first, regulation later?

Gandhi expects AOF to be particularly valuable as a screening tool, providing an estimate of broader fluorine contamination before laboratories proceed to more specific analyses.

Its importance becomes clear when AOF results are compared with targeted PFAS measurements. Gandhi reports that laboratories working with EPA Method 1621 have observed differences between targeted PFAS results and broader AOF measurements ranging from approximately 300- to 4,000-fold in the total fluorine mass balance.

Such discrepancies suggest that targeted methods can leave a substantial portion of fluorine unexplained.

Rather than competing with LC-MS, AOF and CIC therefore provide complementary information. A broad screening method can reveal the magnitude of total contamination, while targeted mass spectrometry identifies and quantifies specific compounds of interest.

Where IC-MS fits into the PFAS toolbox

No single technique can cover the entire PFAS problem. Gandhi highlights very short-chain, highly polar fluorinated compounds as another analytical challenge.

Compounds such as trifluoroacetic acid (TFA) are highly water-soluble and may not be quantitatively retained by the carbon materials used for AOF sample preparation. Direct ion chromatography can provide an alternative route for separating such compounds from common inorganic anions.

Coupling IC with mass spectrometry adds another level of sensitivity and selectivity. Gandhi therefore sees IC-MS and IC-MS/MS as increasingly important tools for highly polar fluorinated compounds. Similar approaches can also be useful beyond PFAS, including the determination of polar pesticides such as glyphosate and glufosinate.

Toward lower detection limits and more complete PFAS analysis

For Gandhi, current standardized methods represent a beginning rather than an endpoint. Improvements in instrumentation and particularly sample preparation could push total fluorine analysis to substantially lower concentrations.

He notes that current combustion IC configurations can reach approximately 0.5 ppb, or 500 parts per trillion, and believes that improvements in sample volume, preparation procedures and mitigation of inorganic fluoride backgrounds could eventually move detection below 100 ppt and potentially toward 50 ppt.

Extractable organic fluorine workflows could provide another bridge between broad fluorine screening and targeted LC-MS methods. Combining improved extraction with CIC could allow samples to be screened for organic fluorine before more detailed compound-specific characterization.

The broader message from Gandhi's career is that PFAS analysis is unlikely to be solved by a single analytical technique. Targeted LC-MS provides compound-specific sensitivity and selectivity; AOF and combustion IC reveal a broader fluorine picture; and IC-MS can address highly polar compounds that are difficult to capture using conventional workflows. Used together, these techniques can provide laboratories with a much more complete understanding of PFAS contamination than any one approach alone.

This text has been automatically transcribed from a video presentation using AI technology. It may contain inaccuracies and is not guaranteed to be 100% correct.

Concentrating on Chromatography Podcast

Dive into the frontiers of chromatography, mass spectrometry, and sample preparation with host David Oliva. Each episode features candid conversations with leading researchers, industry innovators, and passionate scientists who are shaping the future of analytical chemistry. From decoding PFAS detection challenges to exploring the latest in AI-assisted liquid chromatography, this show uncovers practical workflows, sustainability breakthroughs, and the real-world impact of separation science. Whether you’re a chromatographer, lab professional, or researcher you'll discover inspiring content!

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