Enhanced Screening of PFAS Compounds by SDXNS200H Combustion Ion Chromatography System (CIC)
Abstract
This application note presents a total fluorine screening method using the SDXNS200H Combustion Furnace coupled with Ion Chromatography. The method demonstrates excellent quantitative accuracy and consistency for PFAS compounds with different structures and concentration levels.
The system accommodates various sample forms and provides an accurate and efficient approach to total fluorine determination, making it a valuable complementary screening tool for identifying potential PFAS contamination.
Application Note: SD-XNS-001-01002
Introduction
Per- and polyfluoroalkyl substances, commonly known as PFAS, are organic compounds containing at least one fully fluorinated carbon atom, typically present as a –CF₃ or –CF₂– structural unit. In these compounds, hydrogen atoms are replaced by fluorine atoms, forming highly stable carbon–fluorine bonds.
Due to their exceptional chemical stability, thermal resistance and surface-active properties, PFAS have been widely used in numerous industrial and consumer applications, including:
- Oil-resistant coatings for food-contact packaging
- Water-repellent treatments for textiles
- Firefighting foams
- Electronic coatings
- Other specialty surface-treatment applications
However, PFAS are extremely resistant to environmental degradation. Many PFAS compounds exhibit persistence, bioaccumulation potential, long-range environmental transport and various toxic effects, including neurotoxicity, genotoxicity, reproductive toxicity and developmental toxicity. As a result, they may pose long-term risks to ecosystems and human health.
The predominant analytical technique for PFAS determination is liquid chromatography–tandem mass spectrometry, or LC–MS/MS. This technique can identify and quantify specific PFAS compounds with detection limits reaching the ppb level.
Nevertheless, more than 14,000 PFAS substances have been registered, while commercially available reference standards cover only a limited proportion of these compounds. Because LC–MS/MS identification generally relies on reference standards and database matching, PFAS compounds outside the available target list may remain unidentified and unquantified.
To address this analytical coverage gap, high-temperature combustion followed by ion chromatography provides a complementary approach for total fluorine-based PFAS screening.
Method Advantages
Extended High-Temperature Isothermal Zone for Complete Decomposition
Through an optimized combustion furnace design, the SDXNS200H provides a high-temperature isothermal zone longer than 14 cm, with a temperature uniformity of ±20°C.
The extended high-temperature zone increases the residence time of fully fluorinated compounds in the combustion region, improving decomposition and combustion efficiency.
Ultra-Low System Blank for Trace-Level Analysis
The SDXNS200H uses components selected for low or negligible fluorine release and features an optimized liquid-flow-path design.
These measures reduce the system blank to below 100 ppb, calculated using a 10 mL collection volume and a 50 mg sample, thereby supporting reliable trace-level fluorine determination.
Real-Time Combustion Monitoring
The system displays the sample position, combustion temperature and combustion status in real time.
Operators can monitor the complete decomposition process, which facilitates method development, operating-condition optimization and troubleshooting.
Flexible System Configuration
The combustion furnace is designed as an independent module and can be connected directly to most mainstream ion chromatographs already installed in the laboratory.
A complete system with the manufacturer’s ion chromatograph is also available. An optional automatic dilution module can dilute high-concentration samples into the instrument’s linear calibration range without manual intervention.
Experimental Conditions
General Combustion Conditions
| Parameter | Setting |
|---|---|
| Combustion Temperature | 1100°C |
| Oxygen Flow Rate | 400 mL/min |
| Argon Flow Rate | 200 mL/min |
| Steam Purge Argon Flow Rate | 100 mL/min |
| Water Flow Rate for Steam Generation | 0.1 mL/min |
Blank-Test Sample Introduction Program
| Step | Insertion Distance | Insertion Time | Dwell Time |
|---|---|---|---|
| Step 1 | 200 mm | 100 s | 100 s |
| Step 2 | 30 mm | 15 s | 100 s |
| Step 3 | 30 mm | 15 s | 100 s |
| Step 4 | 50 mm | 30 s | 160 s |
Final Collection Volume: 10 mL
Sample-Test Introduction Program
| Step | Insertion Distance | Insertion Time | Dwell Time |
|---|---|---|---|
| Step 1 | 170 mm | 85 s | 100 s |
| Step 2 | 20 mm | 150 s | 100 s |
| Step 3 | 15 mm | 100 s | 100 s |
| Step 4 | 75 mm | 150 s | 150 s |
Final Collection Volume: 22.16 mL
Results and Discussion
1. Blank Test
Fluoride Concentration
Seven consecutive blank measurements were performed.
The average fluoride concentration was 0.32 μg/L, calculated using 10 mL of absorption solution and a 50 mg sample basis. The relative standard deviation was 3.06%, which was below 5%.
These results demonstrate that the system blank is extremely low and stable. A low blank level minimizes interference from the analytical system and supports reliable quantification of low-concentration fluorine samples.
Table 1. Blank-Test Results
| Measurement | F⁻ Concentration (μg/L) | F⁻ Peak Area | Cl⁻ Concentration (μg/L) | Cl⁻ Peak Area | Br⁻ Concentration (μg/L) | Br⁻ Peak Area | SO₄²⁻ Concentration (μg/L) |
|---|---|---|---|---|---|---|---|
| 1 | 0.33 | 0.0094 | 0.49 | 0.00351 | 0 | 0 | 0.0081 |
| 2 | 0.32 | 0.0092 | 0.49 | 0.00341 | 0 | 0 | 0.0082 |
| 3 | 0.32 | 0.0092 | 0.48 | 0.00333 | 0 | 0 | 0.0090 |
| 4 | 0.32 | 0.0092 | 0.48 | 0.00321 | 0 | 0 | 0.0082 |
| 5 | 0.30 | 0.0087 | 0.47 | 0.00315 | 0 | 0 | 0.0085 |
| 6 | 0.31 | 0.0088 | 0.47 | 0.00312 | 0 | 0 | 0.0079 |
| 7 | 0.31 | 0.0089 | 0.47 | 0.00311 | 0 | 0 | 0.0079 |
| Average | 0.32 | 0.0091 | 0.48 | 0.00326 | 0 | 0 | 0.0083 |
| RSD (%) | 3.06 | 1.88 | — | — | — | — | — |
System-Blank Ion Chromatogram
The system-blank chromatogram shows that the SDXNS200H combustion–ion chromatography system provides a very low background signal and a stable baseline.
The background does not cause significant interference during trace-level fluoride determination, supporting reliable quantitative results for low-concentration samples.
Figure 1. Ion chromatogram of the system blank
2. Sample Test
PFBS Spike-Recovery Test
The SDXNS200H combustion–ion chromatography system was evaluated using a PFBS standard, or perfluorobutanesulfonic acid, representing a C4 short-chain sulfonic PFAS.
Spike-recovery tests were performed at five concentration levels.
The average recoveries ranged from 96.70% to 107.25%, while the RSD values calculated from the table ranged from 0.21% to 1.86%.
Accurate recovery was achieved across all tested concentration levels. Even when the PFBS standard concentration covered more than two orders of magnitude, from approximately 7.8 to 782 mg/L, the system maintained a highly consistent fluoride response.
The results demonstrate excellent quantitative accuracy for short-chain sulfonic PFAS compounds.
Table 2. PFBS Spike-Recovery Results
| PFBS (mg/L) | Aliquot Volume (mL) | Blank (mg/L) | Fluorine Mass Fraction (%) | Theoretical Concentration (mg/L) | Measured Concentration (mg/L) | Recovery (%) | Mean Recovery (%) | RSD (%) |
|---|---|---|---|---|---|---|---|---|
| 7.821 | 0.20 | 0.005 | 57.17 | 0.0403 | 0.0456 | 100.61 | 99.50 | 1.58 |
| 7.821 | 0.20 | 0.005 | 57.17 | 0.0403 | 0.0447 | 98.38 | 99.50 | 1.58 |
| 39.105 | 0.05 | 0.005 | 57.17 | 0.0504 | 0.0593 | 107.25 | 107.25 | 0.56 |
| 39.105 | 0.05 | 0.005 | 57.17 | 0.0504 | 0.0589 | 106.86 | 107.25 | 0.56 |
| 78.21 | 0.20 | 0.005 | 57.17 | 0.4035 | 0.3918 | 95.85 | 96.70 | 1.23 |
| 78.21 | 0.20 | 0.005 | 57.17 | 0.4035 | 0.3988 | 97.59 | 96.70 | 1.23 |
| 391.05 | 0.20 | 0.005 | 57.17 | 2.0176 | 1.9980 | 98.78 | 98.63 | 0.21 |
| 391.05 | 0.20 | 0.005 | 57.17 | 2.0176 | 1.9920 | 98.48 | 98.63 | 0.21 |
| 782.1 | 0.05 | 0.005 | 57.17 | 1.0088 | 1.0513 | 104.21 | 102.90 | 1.86 |
| 782.1 | 0.05 | 0.005 | 57.17 | 1.0088 | 1.0298 | 101.58 | 102.90 | 1.86 |
PFHxS Spike-Recovery Test
A second recovery study was performed using PFHxS, or perfluorohexanesulfonic acid, representing a C6 medium-chain sulfonic PFAS.
Five concentration levels were evaluated. The mean recoveries ranged from 97.12% to 107.95%, with RSD values ranging from 0.06% to 2.90%.
The results show that the SDXNS200H provides stable and accurate recovery across different PFHxS concentration levels, demonstrating reliable quantitative performance for medium-chain sulfonic PFAS compounds.
Table 3. PFHxS Spike-Recovery Results
| PFHxS (mg/L) | Aliquot Volume (mL) | Blank (mg/L) | Fluorine Mass Fraction (%) | Theoretical Concentration (mg/L) | Measured Concentration (mg/L) | Recovery (%) | Mean Recovery (%) | RSD (%) |
|---|---|---|---|---|---|---|---|---|
| 8.296 | 0.20 | 0.005 | 61.88 | 0.0463 | 0.0510 | 99.28 | 101.33 | 2.90 |
| 8.296 | 0.20 | 0.005 | 61.88 | 0.0463 | 0.0529 | 103.38 | 101.33 | 2.90 |
| 41.48 | 0.10 | 0.005 | 61.88 | 0.1158 | 0.1178 | 97.38 | 97.12 | 0.37 |
| 41.48 | 0.10 | 0.005 | 61.88 | 0.1158 | 0.1172 | 96.86 | 97.12 | 0.37 |
| 82.96 | 0.20 | 0.005 | 61.88 | 0.4633 | 0.4522 | 97.60 | 98.32 | 1.02 |
| 82.96 | 0.20 | 0.005 | 61.88 | 0.4633 | 0.4589 | 99.04 | 98.32 | 1.02 |
| 414.8 | 0.10 | 0.005 | 61.88 | 1.1583 | 1.1828 | 101.68 | 102.21 | 0.57 |
| 414.8 | 0.10 | 0.005 | 61.88 | 1.1583 | 1.1901 | 102.74 | 102.21 | 0.57 |
| 829.6 | 0.05 | 0.005 | 61.88 | 1.1583 | 1.2499 | 107.90 | 107.95 | 0.06 |
| 829.6 | 0.05 | 0.005 | 61.88 | 1.1583 | 1.2509 | 107.99 | 107.95 | 0.06 |
Ion Chromatogram
The sample chromatogram shows a clearly defined fluoride peak at approximately 5.990 min. The chloride peak appears at approximately 7.480 min.
The fluoride peak is well separated from adjacent components at the baseline. Its peak area can therefore be used for accurate quantification without significant interference from other anions in the sample matrix.
Figure 2. Ion chromatogram of a PFAS sample test
Conclusion
A total fluorine-based PFAS screening method was established using the SDXNS200H High-Temperature Combustion Furnace coupled with Ion Chromatography.
The study produced the following key findings:
- The average system-blank fluoride concentration was 0.32 μg/L, with an RSD of 3.06%, demonstrating an extremely low and stable analytical background.
- Spike-recovery tests using PFBS and PFHxS produced individual recoveries of 95.85%–107.25% and 96.86%–107.99%, respectively, confirming reliable performance across different PFAS chain lengths and concentration levels.
- The SDXNS200H combustion–ion chromatography system provides an effective complementary screening method for addressing the potential detection gaps of targeted LC–MS/MS analysis caused by limited reference-standard coverage.
The system offers food-contact packaging, textiles and other consumer-product industries a reliable total fluorine screening tool for PFAS compliance assessment under increasingly stringent regulatory requirements.
