Benefits of Agilent Altura Ultra Inert HPLC Column Hardware

Significance of the topic

Ultrashort-chain (USC) and polyfunctional PFAS are small, highly polar, and strongly acidic analytes increasingly detected in environmental waters. Their physicochemical properties cause poor retention on conventional reversed-phase columns and a high propensity for adsorption to metal surfaces, which degrades signal, reproducibility, and peak shape at trace concentrations. Reliable analytical methods for these compounds are essential for environmental monitoring, regulatory compliance, and fluorinated-chemistry process control.

Study objectives and overview

This application study compared the performance of Agilent Altura Ultra Inert HPLC hardware versus conventional stainless-steel hardware when both columns were packed with the same Poroshell 120 PFAS stationary phase. Primary goals were to quantify the impact of inert hardware on retention time (RT) stability, peak area (abundance), signal-to-noise, and robustness across sample matrices and injection volumes. The study evaluated nine conventional USC PFAS plus two challenging polyfunctional difluorinated acids—difluoromalonic acid (MMF) and difluorosulfoacetic acid (DFSA)—across three matrices (RO water, a high-anion synthetic water, and methanol) and two injection volumes (5 and 20 µL). Statistical modeling was used to isolate hardware effects while accounting for interactions with matrix and injection volume.

Methodology

Key experimental design points:

• Analytes: nine standard USC PFAS (including TFA surrogate 13C2-TFA, PFPrA, PFBA, PFMOAA, etc.) plus MMF and DFSA to stress-test chromatographic behavior.
• Matrices: reverse osmosis (RO) water, synthetic high-anion water (nitrate, bicarbonate, chloride, sulfate) prepared per an EPA-based formulation, and LC/MS-grade methanol.
• Injection volumes: 5 µL and 20 µL to probe volume-dependent hardware effects.
• Columns: commercially available Altura Poroshell PFAS column (2.1 × 50 mm, 2.7 µm) and a stainless-steel (SS) column custom-packed with the identical PFAS stationary phase from the same batch—this isolates hardware as the variable.
• Mobile phases and gradient were optimized for retention and ionization of small polar acids; methanol was added to improve ionization for DFSA, and ammonium acetate and acetonitrile proportions were adjusted to balance gradient performance.
• Data handling: peak areas were normalized to concentration, log10-transformed, and analyzed in linear models with categorical predictors (injection volume, column type, matrix) including interaction terms; ANOVA was used to evaluate predictor significance.

Used instrumentation

Instrumentation and system configuration summarized:

• LC: Agilent 1290 Infinity II high-performance liquid chromatograph.
• MS: Agilent 6475 triple-quadrupole LC/MS operated in negative electrospray ionization with MRM transitions tailored to each analyte.
• PFAS contamination control: Agilent InfinityLab PFAS analysis HPLC conversion kit was installed; the supplied PFC delay column (C18) was replaced with an Agilent Poroshell 120 PFAS delay column to better retain and delay highly polar PFAS such as TFA.
• Key LC settings (representative): column temperature 40 °C, flow 0.5 mL/min, injection volumes 5/20 µL, mobile phase A = 0.1% acetic acid in water; mobile phase B = ACN/MeOH/water with 20 mM ammonium acetate (adjusted for optimal retention/ionization).

Main results and discussion

Retention time stability and reproducibility:

• Altura Ultra Inert hardware provided more consistent RT behavior across matrices and injection volumes, evidenced by lower RT RSDs averaged across conditions.
• Both hardware types produced acceptable Gaussian peak shapes for most analytes at lower injection volumes, but Altura was less sensitive to method perturbations.

Peak area and sensitivity:

• After statistical correction for matrix and injection volume, column hardware had a statistically significant effect on peak area for seven of nine standard USC PFAS. Factor increases for Altura relative to SS ranged approximately from 1.007× to 1.23×, with the largest gains observed for 13C2-TFA and PFMOAA.
• PFBA and DFA did not show significant hardware dependence; DFA was strongly influenced by matrix effects (signal suppression in synthetic water).
• Altura hardware reduced MS transition background for some compounds (example: PFPrA), improving S/N (e.g., PFPrA S/N increased from 17 to 22 at a representative condition).

Behavior of polyfunctional, highly polar analytes (MMF, DFSA):

• MMF and DFSA displayed pronounced sensitivity to interaction effects among hardware, injection volume, and matrix. At 5 µL injections Altura and SS differed only modestly, but at 20 µL and in the high-anion synthetic matrix, SS hardware showed forward RT shifts, peak tailing, and loss of Gaussian peak shape.
• For MMF the labeled surrogate showed that, under SW conditions with SS hardware and large injection volume, the peak smeared rather than forming a discrete peak; Altura hardware preserved definable peaks and more reproducible retention.
• DFSA under 20 µL in SW exhibited marked RT shift and enhanced/tailing response on SS hardware, making identification ambiguous in the absence of a labeled standard; Altura mitigated this instability.

Interpretation:

• Observed benefits are consistent with reduced adsorption and altered ionization behavior when analyte interaction with metal surfaces is minimized by an inert flow path coating.
• Advantages are most pronounced for the smallest, most acidic, and most polar compounds and exacerbate with larger injection volumes and challenging matrices.

Benefits and practical applications

The Altura Ultra Inert hardware provides measurable advantages for trace-level analysis of USC and polyfunctional PFAS:

• Improved reproducibility of retention times and peak areas across matrices and injection volumes, increasing method robustness.
• Enhanced sensitivity (reduced background, improved S/N) for several target analytes, aiding low-concentration detection and quantitation.
• More reliable chromatography for polyfunctional and highly polar species (e.g., MMF, DFSA) that are prone to adsorption or matrix-induced behavior changes.
• Reduced risk of false negatives or misidentification caused by peak distortion or RT shifts—important when labeled surrogates are unavailable.

Practical use cases include routine environmental monitoring, laboratory workflows handling diverse water matrices, method development for challenging PFAS, and forensic or process-control analyses where confidence in low-level signals is required.

Future trends and potential applications

Anticipated directions and recommendations:

• Inert column hardware is likely to be increasingly adopted for trace analysis of small polar acids beyond PFAS (e.g., haloacetic acids, phosphorylated small molecules) where metal-surface interactions degrade performance.
• Standardization of PFAS methods may incorporate inert flow-path components as best practice, particularly for ultrashort-chain analytes and matrices with high ionic strength.
• Expanded availability of isotopically labeled analogues will improve identification and quantitation; until then, inert hardware mitigates some uncertainty.
• Further work could optimize injection volume and solvent composition to balance sensitivity against matrix-induced artifacts, and cross-laboratory studies should evaluate reproducibility of inert-hardware benefits.
• Method miniaturization and UHPLC adaptation may further reduce matrix effects, but hardware inertness will remain critical for highly adsorptive analytes.

Conclusion

Using Altura Ultra Inert HPLC hardware with the Poroshell 120 PFAS stationary phase improves chromatographic robustness for ultrashort-chain and polyfunctional PFAS compared with identical stationary phase packed into stainless-steel hardware. The inert hardware reduces RT variability, increases peak areas for most evaluated USC PFAS, lowers background for some transitions, and preserves usable peak shape for highly polar compounds (MMF, DFSA) under challenging matrix and injection conditions. These improvements support greater analytical confidence for trace PFAS workflows, particularly in environmental monitoring where matrices and analyte properties exacerbate adsorption and ionization variability.

References

1. Arp, H. P. H.; Gredelj, A.; Glüge, J.; Scheringer, M.; Cousins, I. T. The Global Threat from the Irreversible Accumulation of Trifluoroacetic Acid (TFA). Environmental Science & Technology 2024, 58(45), 19925–19935.
2. Parry, E.; Huang, I. Reliable Ultra Short Chain PFAS Analysis in Water and Landfill Groundwater Using the Agilent Altura Poroshell PFAS Column and LC/MS/MS. Agilent Technologies application note, publication number 5994-9019EN, 2026.
3. Hsiao, J.; Masigol, M.; Closser, R.; Serge, L.; Hu, L.-C.; vonDoehren, N.; Tripodi, A. A. P.; Blackwell, A. Pushing the Boundaries of Chromatographic Separation with Inert HPLC Column Hardware: A Comprehensive Evaluation of Inertness, Stability, and Analytical Sensitivity. Agilent Technologies white paper, publication number 5994‑8618EN, 2025.
4. U.S. Environmental Protection Agency. Method 557: Determination of Haloacetic Acids, Bromate, and Dalapon in Drinking Water by Ion Chromatography Electrospray Ionization Tandem Mass Spectrometry (ICESI–MS/MS), Version 1.0; EPA Document No. 815B09012; Office of Water, U.S. Environmental Protection Agency: Washington, DC, 2009.