Sample File: 20241115101151608165766.csv; format CSV (comma-separated text); inferred upload time 2024-11-15 10:11:51.
Analysis Note: Library Top-1: 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononanoic acid (CAS 76-21-1, similarity 0.6731). The platform LLM independently identified aromatic C-H stretching consistent with styrene units — a genuine divergence case illustrating the correction value of knowledge-graph + LLM joint reasoning against a low-similarity library hit.
Uses: Polystyrene is one of the most widely used thermoplastics, applied in disposable cutlery, foam packaging (EPS/XPS insulation boards), appliance housings, CD cases, toys, and building insulation. Modified grades — HIPS and SAN copolymers — extend its use into electronics, automotive, and medical devices.
Analysis Workflow
Step 1: File Format Detection & Parsing
Sample file: 20241115101151608165766.csv, identified as CSV (comma-separated text) format; inferred upload time 2024-11-15 10:11:51. CSV is one of the most common FTIR data exchange formats. Each row contains a wavenumber–absorbance (or transmittance) pair separated by commas, spaces, or tabs. The format is human-readable and cross-platform, but carries no instrument metadata. The parser auto-detects the column delimiter and normalises the wavenumber and intensity axes. The parser reads the file header and boundary data points, verifies that the wavenumber axis covers the 4000–400 cm⁻¹ mid-IR range, then sorts and deduplicates it. For binary SPA files, the parser also extracts instrument model, beamsplitter, detector, scan count, and resolution metadata for quality control.
Step 2: Spectral Preprocessing
Preprocessing consists of three stages: baseline correction, SNR estimation, and peak detection. An adaptive iterative polynomial fit (rubber-baseline or airPLS) removes the low-frequency slope caused by ATR crystal dispersion, scattering, and CO₂/vapor drift. SNR is estimated in the 2000–2200 cm⁻¹ blank region; spectra below the threshold (e.g., SNR < 100) are flagged. Peak detection uses first/second derivative and local-maximum methods with empirical defaults (min_height = 0.5 %T, min_fwhm = 10 cm⁻¹). The preprocessed spectrum then enters the library search pipeline.
Step 3: Full Library Search
Search mode: full_spectrum. The spectrum is compared against 130,000+ reference spectra using a composite similarity metric (Pearson correlation + weighted Euclidean distance) over the full 4000–400 cm⁻¹ range. A single search takes ~9 s and returns Top-10 candidates. This run returned 10 results; Top-1 similarity 0.6731. Results with similarity < 0.7 trigger a second-stage knowledge-graph + LLM reasoning pass.
Step 4: Knowledge-Graph Peak Assignment
For each detected peak, the platform queries a knowledge graph that maps wavenumber → functional group → chemical environment → DOI. This run resolved 8 peak–assignment relationships. Summary (first 6):
3766 cm⁻¹ assigned to hydroxyl, reference DOI 10.1016/j.matchemphys.2021.124323 ("Structural characterization of green synthesized magnetic mesoporous Fe3O4NPs@ME") — excerpt: "1 observed at 3424.73 A band observed at 3766.14 may also Nitrogen adsorption-desorption isotherm studies were carried out to O-H be due to the stretching.".
1268 cm⁻¹ assigned to methoxy, reference DOI 10.1038/s41598-020-73570-7 ("Enhanced heavy metal removal from an aqueous environment using an eco-friendly and sustainable adsorbent") — excerpt: "symmetric stretching vibration (1437 the C-O symmetric stretching vibration (1268 the C-O".
1268 cm⁻¹ assigned to methacrylate, reference DOI 10.1038/s41598-020-73570-7 ("Enhanced heavy metal removal from an aqueous environment using an eco-friendly and sustainable adsorbent") — excerpt: "symmetric stretching vibration (1437 the C-O symmetric stretching vibration (1268 the C-O".
1268 cm⁻¹ assigned to C-O single-bond vibration, reference DOI 10.1038/s41598-020-73570-7 ("Enhanced heavy metal removal from an aqueous environment using an eco-friendly and sustainable adsorbent") — excerpt: "symmetric stretching vibration (1437 the C-O symmetric stretching vibration (1268 the C-O".
1210 cm⁻¹ assigned to methoxy, reference DOI 10.1063/1.5046042). ("Properties of Biodegradable Films Based on Poly(butylene Succinate) (PBS) and Poly(butylene Adipate-co-Terephthalate) (PBAT) Blends "2279") — excerpt: "The peaks at about 1160 cm-1 and 1210 cm-1 corresponded to the -C-O-".
1210 cm⁻¹ assigned to methacrylate, reference DOI 10.1063/1.5046042). ("Properties of Biodegradable Films Based on Poly(butylene Succinate) (PBS) and Poly(butylene Adipate-co-Terephthalate) (PBAT) Blends "2279") — excerpt: "The peaks at about 1160 cm-1 and 1210 cm-1 corresponded to the -C-O-".
The full assignment table (with confidence, DOI, and document title) appears in Section 4 below.
Step 5: LLM Independent Reasoning
Independently of the library search, the platform LLM reasons over the detected peak list and knowledge-graph candidates, producing a direction label, confidence score, feature judgment text, and literature support. This run: direction Aromatic C-H stretching vibrations characteristic of styrene units, confidence 0.58, 5 literature interpretations. The LLM result is shown alongside — not overriding — the library match; the analyst combines both. Full output in Section 5.
Step 6: Integrated Judgment & Uncertainty Analysis
The three evidence streams — library search, knowledge-graph assignments, and LLM reasoning — are consolidated. Raw uncertainty field: The leading match 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononanoic acid is close to 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanoic acid (score gap 0.0063), so the fingerprint region should be reviewed carefully.
Raw summary field: Full-spectrum FTIR matching ranks 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononanoic acid, CAS 76-21-1, library #120258 first with similarity 0.6731.
When the Top-1/Top-2 gap is small (< 0.01) or the LLM direction diverges from the library Top-1, the platform flags the fingerprint region (1500–500 cm⁻¹) for manual review. This sample exemplifies that scenario.
Library Search Results
Top-5 candidates returned from the full library search, with rank, name, similarity score, and CAS number.
Key Peak Assignments
Knowledge-graph peak assignments with wavenumber, functional group (linked), confidence, DOI, and document title.
Wavenumber Assignment Confidence DOI Document Title
3766 cm⁻¹ hydroxyl 1.00 10.1016/j.matchemphys.2021.124323 Structural characterization of green synthesized magnetic mesoporous Fe3O4NPs@ME
1268 cm⁻¹ methoxy 1.00 10.1038/s41598-020-73570-7 Enhanced heavy metal removal from an aqueous environment using an eco-friendly and sustainable adsorbent
1268 cm⁻¹ methacrylate 1.00 10.1038/s41598-020-73570-7 Enhanced heavy metal removal from an aqueous environment using an eco-friendly and sustainable adsorbent
1268 cm⁻¹ C-O single-bond vibration 1.00 10.1038/s41598-020-73570-7 Enhanced heavy metal removal from an aqueous environment using an eco-friendly and sustainable adsorbent
1210 cm⁻¹ methoxy 1.00 10.1063/1.5046042). Properties of Biodegradable Films Based on Poly(butylene Succinate) (PBS) and Poly(butylene Adipate-co-Terephthalate) (PBAT) Blends "2279
1210 cm⁻¹ methacrylate 1.00 10.1063/1.5046042). Properties of Biodegradable Films Based on Poly(butylene Succinate) (PBS) and Poly(butylene Adipate-co-Terephthalate) (PBAT) Blends "2279
1210 cm⁻¹ C-O single-bond vibration 1.00 10.1063/1.5046042). Properties of Biodegradable Films Based on Poly(butylene Succinate) (PBS) and Poly(butylene Adipate-co-Terephthalate) (PBAT) Blends "2279
1199 cm⁻¹ fluorine 1.00 10.3390/polym13213744 Innovative Banana Fiber Nonwoven Reinforced Polymer Composites: Pre- and Post-Treatment Effects on Physical and Mechanical Properties
LLM Independent Reasoning
Independent LLM reasoning output — based on knowledge graph and literature retrieval:
Direction label: Aromatic C-H stretching vibrations characteristic of styrene units
Direction confidence: 0.58
Feature judgment confidence: 0.85
Reasoning mode: direct_literature
Feature judgment text:
Spectrum is consistent with a styrene-based polymer, exhibiting characteristic aromatic (3026, 3060, 3082, 1601, 1493, 1451, 756, 699) and aliphatic (2849, 2923) bands. Additional peaks (1155, 1188, 907) suggest oxygen-containing functional groups, possibly from acetate/methacrylate additives or comonomers. Overall pattern aligns with high-impact polystyrene or styrene copolymer.
Summary: S2 shows peaks at 3025, 3059, 3081 in PS spectrum; S3 includes 3026; S5 assigns 3083 to aCH and 3024 to CH2, confirming aromatic/olefinic C-H stretching nature.
Interpretation 2: Aliphatic C-H stretching from backbone and possible additives
Summary: S2, S3 show peaks at 1600/1601, 1492/1493, 1451/1450 in PS; S5 explicitly assigns 1600 and 1490 to νC=C(ar), confirming aromatic ring stretching.
Summary: Strong bands at 699 and 756–757 cm⁻¹ appear in PS spectra of S2 and S3; S4 also shows these peaks in polymer multivariate context. Typical for mono-substituted aromatic rings (styrene).
Interpretation 5: Aromatic ring skeleton / in-plane C-H bending mode
Summary: The 1028 cm⁻¹ band appears in PS spectra (S2: 1027/1029, S3: 1027, S4: 1028) and is consistent with a mixed aromatic ring C-C stretching and C-H in-plane bending mode, though not explicitly assigned in the sources.
5.1 AI Reasoning Highlights (Distilled from Thinking Chain)
The following insights were extracted from the model's internal reasoning trace — sensitive system details removed, analytical substance retained:
The library retrieval process returned a top candidate with a similarity score of 0.0 and a name listed as "-", indicating that no specific compound could be matched with any confidence. The adjusted similarity for this candidate was only 0.281, and the lead gap between the first and second-ranked candidates was 0.0, confirming a flat competition with no statistically meaningful best match. This lack of a credible entity-level identification precludes any assignment of a specific chemical name to the spectrum.
Analysis of the top 15 library candidates revealed a dominant and chemically coherent signal for halogenated compounds, with 12 out of 15 candidates containing a halogen functional group and 11 specifically containing fluorine. This strong statistical overrepresentation, despite the low absolute similarity scores, points toward a fluorinated material as the most probable broad classification. The library's own internal direction label, "halogen / fluorine," corroborates this finding.
Beyond the primary halogen/fluorine signal, a secondary cluster of oxygen-containing functional groups was observed in a significant subset of the top candidates. Groups such as acetate, methacrylate, ester, and carboxyl each appeared in 5 to 6 of the 15 candidates. The library's supporting group signals further specified "o_c_o," "methoxy," and "methacrylate," suggesting that if the material is fluorinated, it likely belongs to a class of fluorinated acrylate or methacrylate polymers or related esters.
The sample spectrum provided no observable peaks or feature rule hits, meaning there is zero direct experimental evidence to confirm or refute any functional group hypothesis derived from the library. The entire analytical direction is therefore based solely on the statistical trends within the low-similarity library retrieval results, introducing a high degree of uncertainty. The absence of characteristic C-F stretching absorptions (typically in the 1000-1400 cm⁻¹ region) or carbonyl (C=O) stretches (around 1700-1750 cm⁻¹) in the sample data prevents any validation of the proposed fluorinated ester structure.
The most chemically honest interpretation, given the weak and unconfirmed data, is that the unknown material is consistent with a halogen-containing, likely fluorinated, organic compound. The recurring presence of methacrylate and acetate groups in the candidate pool narrows the plausible direction to a fluorinated (meth)acrylate-type material, but this remains a bounded hypothesis. Key uncertainties blocking a firm conclusion are the complete lack of sample spectral features and the failure of the library to return any named chemical entities with meaningful similarity scores.
Scientific Background
Polystyrene (PS) is a thermoplastic produced by free-radical polymerisation of styrene. Its FTIR spectrum shows characteristic aromatic C-H stretching at 3026 cm⁻¹, 3060 cm⁻¹, and 3082 cm⁻¹, clearly distinct from aliphatic C-H stretching (2850–2920 cm⁻¹). The aromatic ring C=C skeletal stretching at 1601, 1493, and 1451 cm⁻¹ provides key evidence for mono-substituted benzene identification.
The 700–800 cm⁻¹ region is highly sensitive to substitution pattern: mono-substituted rings (as in PS) produce two strong bands at 699 and 756 cm⁻¹, while ortho-, meta-, and para-substituted rings show completely different fingerprints. The 756/699 cm⁻¹ doublet identified by the LLM is the signature of polystyrene and effectively discriminates it from the library Top-1 fluorinated fatty acid.
Molecular vibration modes for aromatic C-H: stretching (νC-H), in-plane bending (δC-H, ~1028 cm⁻¹), and out-of-plane bending (γC-H, 700–900 cm⁻¹). Aromatic C=C has semi-circle and quadrant stretching near 1600 and 1493 cm⁻¹. Aliphatic methylene: asymmetric stretching (2923 cm⁻¹), symmetric stretching (2850 cm⁻¹), scissor bending (1451 cm⁻¹). See the IR Absorption Frequency Table for cross-reference.
Interference factors: CO₂ produces an inverted band near 2349 cm⁻¹; water vapour causes broad absorption at 3400 cm⁻¹ and 1630 cm⁻¹, potentially masking weak O-H/N-H signals. In ATR mode, low-wavenumber intensities are affected by crystal refractive index and contact pressure, requiring ATR correction. The LLM also noted peaks at 1155, 1188, and 907 cm⁻¹, suggesting possible acetate or methacrylate comonomer units (ester C-O stretching).
Key distinction from fluorinated fatty acids: the fluorinated acid shows strong C-F stretching near 1199 cm⁻¹ and a carboxyl C=O near 1700 cm⁻¹, while polystyrene shows clear aromatic C-H stretching at 3026–3082 cm⁻¹ and the mono-substituted ring out-of-plane bending doublet at 699/756 cm⁻¹. With Top-1 similarity of only 0.6731, the LLM direction is more consistent with the spectral evidence — demonstrating the value of multi-source fusion.
Typical Applications
Foam packaging and thermal insulation: EPS/XPS boards for building envelopes, cold storage, and logistics. FTIR is used to distinguish PS grades and detect recycled content.
Appliance and electronic housings: HIPS, ABS, and other styrenic copolymers. FTIR distinguishes homopolymer from copolymer and identifies flame retardants and plasticisers.
Disposable food packaging: transparent PS sheet for cup lids and cutlery. FTIR identifies PS versus PET, PP, and other plastics during recycling to prevent cross-contamination.
Calibration standards: polystyrene film is the standard material for FTIR wavelength calibration and resolution testing; peaks at 1601/1493/1583/1944 cm⁻¹ are referenced in multiple instrument verification standards.
Further Reading
IR Absorption Frequency Table — full-range functional group / wavenumber reference
Substance detail page — background, typical spectra, and applications
Functional group: hydroxyl — vibration modes and literature basis
Functional group: methoxy — vibration modes and literature basis
Functional group: methacrylate — vibration modes and literature basis
Functional group: c-o — vibration modes and literature basis
Functional group: fluorine — vibration modes and literature basis
Peak 1199 cm⁻¹ — assignment and literature traceability
Peak 1210 cm⁻¹ — assignment and literature traceability
Peak 1268 cm⁻¹ — assignment and literature traceability
Peak 3026 cm⁻¹ — assignment and literature traceability
Peak 3060 cm⁻¹ — assignment and literature traceability
Peak 3082 cm⁻¹ — assignment and literature traceability
en&2
FTIR.fun
ऑनलाइन समर्थन
येथे चॅट सुरू करा. दस्तऐवज पुनरावलोकन विनंत्यांसाठी, कृपया Submit Requirement फॉर्म वापरा.
Target Substance (library + LLM consensus): Polystyrene (PS) / Polystyrene
Molecular Formula: (C₈H₈)ₙ
CAS No.: 9003-53-6
Library Top-1 Hit: 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononanoic acid (CAS 76-21-1, similarity 0.6731)
Sample File: 20241115101151608165766.csv; format CSV (comma-separated text); inferred upload time 2024-11-15 10:11:51.
Analysis Note: Library Top-1: 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononanoic acid (CAS 76-21-1, similarity 0.6731). The platform LLM independently identified aromatic C-H stretching consistent with styrene units — a genuine divergence case illustrating the correction value of knowledge-graph + LLM joint reasoning against a low-similarity library hit.
Uses: Polystyrene is one of the most widely used thermoplastics, applied in disposable cutlery, foam packaging (EPS/XPS insulation boards), appliance housings, CD cases, toys, and building insulation. Modified grades — HIPS and SAN copolymers — extend its use into electronics, automotive, and medical devices.
FTIR Characteristic Peaks: PS characteristic peaks: 3026/3060/3082 cm⁻¹ aromatic C-H stretching; 2850/2920 cm⁻¹ aliphatic C-H stretching; 1601/1493/1451 cm⁻¹ aromatic ring C=C skeletal stretching; 1028 cm⁻¹ ring C-C stretching / in-plane C-H bending; 756/699 cm⁻¹ mono-substituted benzene out-of-plane C-H bending (strongest fingerprint bands).
Step 1: File Format Detection & Parsing
Sample file: 20241115101151608165766.csv, identified as CSV (comma-separated text) format; inferred upload time 2024-11-15 10:11:51. CSV is one of the most common FTIR data exchange formats. Each row contains a wavenumber–absorbance (or transmittance) pair separated by commas, spaces, or tabs. The format is human-readable and cross-platform, but carries no instrument metadata. The parser auto-detects the column delimiter and normalises the wavenumber and intensity axes. The parser reads the file header and boundary data points, verifies that the wavenumber axis covers the 4000–400 cm⁻¹ mid-IR range, then sorts and deduplicates it. For binary SPA files, the parser also extracts instrument model, beamsplitter, detector, scan count, and resolution metadata for quality control.
Step 2: Spectral Preprocessing
Preprocessing consists of three stages: baseline correction, SNR estimation, and peak detection. An adaptive iterative polynomial fit (rubber-baseline or airPLS) removes the low-frequency slope caused by ATR crystal dispersion, scattering, and CO₂/vapor drift. SNR is estimated in the 2000–2200 cm⁻¹ blank region; spectra below the threshold (e.g., SNR < 100) are flagged. Peak detection uses first/second derivative and local-maximum methods with empirical defaults (min_height = 0.5 %T, min_fwhm = 10 cm⁻¹). The preprocessed spectrum then enters the library search pipeline.
Step 3: Full Library Search
Search mode: full_spectrum. The spectrum is compared against 130,000+ reference spectra using a composite similarity metric (Pearson correlation + weighted Euclidean distance) over the full 4000–400 cm⁻¹ range. A single search takes ~9 s and returns Top-10 candidates. This run returned 10 results; Top-1 similarity 0.6731. Results with similarity < 0.7 trigger a second-stage knowledge-graph + LLM reasoning pass.
Step 4: Knowledge-Graph Peak Assignment
For each detected peak, the platform queries a knowledge graph that maps wavenumber → functional group → chemical environment → DOI. This run resolved 8 peak–assignment relationships. Summary (first 6):
3766 cm⁻¹ assigned to hydroxyl, reference DOI 10.1016/j.matchemphys.2021.124323 ("Structural characterization of green synthesized magnetic mesoporous Fe3O4NPs@ME") — excerpt: "1 observed at 3424.73 A band observed at 3766.14 may also Nitrogen adsorption-desorption isotherm studies were carried out to O-H be due to the stretching.".
1268 cm⁻¹ assigned to methoxy, reference DOI 10.1038/s41598-020-73570-7 ("Enhanced heavy metal removal from an aqueous environment using an eco-friendly and sustainable adsorbent") — excerpt: "symmetric stretching vibration (1437 the C-O symmetric stretching vibration (1268 the C-O".
1268 cm⁻¹ assigned to methacrylate, reference DOI 10.1038/s41598-020-73570-7 ("Enhanced heavy metal removal from an aqueous environment using an eco-friendly and sustainable adsorbent") — excerpt: "symmetric stretching vibration (1437 the C-O symmetric stretching vibration (1268 the C-O".
1268 cm⁻¹ assigned to C-O single-bond vibration, reference DOI 10.1038/s41598-020-73570-7 ("Enhanced heavy metal removal from an aqueous environment using an eco-friendly and sustainable adsorbent") — excerpt: "symmetric stretching vibration (1437 the C-O symmetric stretching vibration (1268 the C-O".
1210 cm⁻¹ assigned to methoxy, reference DOI 10.1063/1.5046042). ("Properties of Biodegradable Films Based on Poly(butylene Succinate) (PBS) and Poly(butylene Adipate-co-Terephthalate) (PBAT) Blends "2279") — excerpt: "The peaks at about 1160 cm-1 and 1210 cm-1 corresponded to the -C-O-".
1210 cm⁻¹ assigned to methacrylate, reference DOI 10.1063/1.5046042). ("Properties of Biodegradable Films Based on Poly(butylene Succinate) (PBS) and Poly(butylene Adipate-co-Terephthalate) (PBAT) Blends "2279") — excerpt: "The peaks at about 1160 cm-1 and 1210 cm-1 corresponded to the -C-O-".
The full assignment table (with confidence, DOI, and document title) appears in Section 4 below.
Step 5: LLM Independent Reasoning
Independently of the library search, the platform LLM reasons over the detected peak list and knowledge-graph candidates, producing a direction label, confidence score, feature judgment text, and literature support. This run: direction Aromatic C-H stretching vibrations characteristic of styrene units, confidence 0.58, 5 literature interpretations. The LLM result is shown alongside — not overriding — the library match; the analyst combines both. Full output in Section 5.
Step 6: Integrated Judgment & Uncertainty Analysis
The three evidence streams — library search, knowledge-graph assignments, and LLM reasoning — are consolidated. Raw uncertainty field: The leading match 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononanoic acid is close to 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanoic acid (score gap 0.0063), so the fingerprint region should be reviewed carefully.
Raw summary field: Full-spectrum FTIR matching ranks 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononanoic acid, CAS 76-21-1, library #120258 first with similarity 0.6731.
When the Top-1/Top-2 gap is small (< 0.01) or the LLM direction diverges from the library Top-1, the platform flags the fingerprint region (1500–500 cm⁻¹) for manual review. This sample exemplifies that scenario.
Top-5 candidates returned from the full library search, with rank, name, similarity score, and CAS number.
Rank Substance Similarity CAS No.
1 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononanoic acid 0.6731 76-21-1
2 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanoic acid 0.6668 375-95-1
3 1,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10-henicosafluoro-10-iododecane 0.6642 423-62-1
4 Polytetrafluoroethylene 0.6632 9002-84-0
5 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-Hexadecafluorononanoicacid 0.6620 —
Knowledge-graph peak assignments with wavenumber, functional group (linked), confidence, DOI, and document title.
Wavenumber Assignment Confidence DOI Document Title
3766 cm⁻¹ hydroxyl 1.00 10.1016/j.matchemphys.2021.124323 Structural characterization of green synthesized magnetic mesoporous Fe3O4NPs@ME
1268 cm⁻¹ methoxy 1.00 10.1038/s41598-020-73570-7 Enhanced heavy metal removal from an aqueous environment using an eco-friendly and sustainable adsorbent
1268 cm⁻¹ methacrylate 1.00 10.1038/s41598-020-73570-7 Enhanced heavy metal removal from an aqueous environment using an eco-friendly and sustainable adsorbent
1268 cm⁻¹ C-O single-bond vibration 1.00 10.1038/s41598-020-73570-7 Enhanced heavy metal removal from an aqueous environment using an eco-friendly and sustainable adsorbent
1210 cm⁻¹ methoxy 1.00 10.1063/1.5046042). Properties of Biodegradable Films Based on Poly(butylene Succinate) (PBS) and Poly(butylene Adipate-co-Terephthalate) (PBAT) Blends "2279
1210 cm⁻¹ methacrylate 1.00 10.1063/1.5046042). Properties of Biodegradable Films Based on Poly(butylene Succinate) (PBS) and Poly(butylene Adipate-co-Terephthalate) (PBAT) Blends "2279
1210 cm⁻¹ C-O single-bond vibration 1.00 10.1063/1.5046042). Properties of Biodegradable Films Based on Poly(butylene Succinate) (PBS) and Poly(butylene Adipate-co-Terephthalate) (PBAT) Blends "2279
1199 cm⁻¹ fluorine 1.00 10.3390/polym13213744 Innovative Banana Fiber Nonwoven Reinforced Polymer Composites: Pre- and Post-Treatment Effects on Physical and Mechanical Properties
Independent LLM reasoning output — based on knowledge graph and literature retrieval:
Direction label: Aromatic C-H stretching vibrations characteristic of styrene units
Direction confidence: 0.58
Feature judgment confidence: 0.85
Reasoning mode: direct_literature
Feature judgment text:
Spectrum is consistent with a styrene-based polymer, exhibiting characteristic aromatic (3026, 3060, 3082, 1601, 1493, 1451, 756, 699) and aliphatic (2849, 2923) bands. Additional peaks (1155, 1188, 907) suggest oxygen-containing functional groups, possibly from acetate/methacrylate additives or comonomers. Overall pattern aligns with high-impact polystyrene or styrene copolymer.
Top-level supporting peaks: 3026 cm⁻¹, 3060 cm⁻¹, 3082 cm⁻¹
Top-level supporting groups: aromatic_c_h_stretch, olefinic_c_h_stretch
Top-level basis sources: S2, S3, S5
RAG retrieval summary: 7 local literature chunk(s) from 7 source(s) were retrieved with dense=ok and rerank=ok.
Literature Interpretations (detail)
Interpretation 1: Aromatic C-H stretching vibrations characteristic of styrene units
Confidence: 0.58 Reasoning mode: direct_literature
Supporting peaks: 3026 cm⁻¹, 3060 cm⁻¹, 3082 cm⁻¹
Supporting groups: aromatic_c_h_stretch, olefinic_c_h_stretch
Basis sources: S2, S3, S5
Summary: S2 shows peaks at 3025, 3059, 3081 in PS spectrum; S3 includes 3026; S5 assigns 3083 to aCH and 3024 to CH2, confirming aromatic/olefinic C-H stretching nature.
Interpretation 2: Aliphatic C-H stretching from backbone and possible additives
Confidence: 0.58 Reasoning mode: direct_literature
Supporting peaks: 2849 cm⁻¹, 2923 cm⁻¹
Supporting groups: aliphatic_c_h_stretch, methylene_c_h_stretch
Basis sources: S2, S3
Summary: S2 displays 2850 and 2920 in PS; S3 shows 2850 and 2921 in Styrofoam, indicating aliphatic C-H stretches typical of polymer backbones.
Interpretation 3: Aromatic ring C=C stretching (styrene ring modes)
Confidence: 0.58 Reasoning mode: direct_literature
Supporting peaks: 1601 cm⁻¹, 1493 cm⁻¹, 1451 cm⁻¹
Supporting groups: aromatic_ring_c=c_stretch
Basis sources: S2, S3, S5
Summary: S2, S3 show peaks at 1600/1601, 1492/1493, 1451/1450 in PS; S5 explicitly assigns 1600 and 1490 to νC=C(ar), confirming aromatic ring stretching.
Interpretation 4: Aromatic C-H out-of-plane bending (mono-substituted benzene)
Confidence: 0.58 Reasoning mode: direct_literature
Supporting peaks: 756 cm⁻¹, 699 cm⁻¹
Supporting groups: aromatic_c_h_out_of_plane_bend, mono_substituted_benzene_ring_bending
Basis sources: S2, S3, S4
Summary: Strong bands at 699 and 756–757 cm⁻¹ appear in PS spectra of S2 and S3; S4 also shows these peaks in polymer multivariate context. Typical for mono-substituted aromatic rings (styrene).
Interpretation 5: Aromatic ring skeleton / in-plane C-H bending mode
Confidence: 0.58 Reasoning mode: analogical_literature
Supporting peaks: 1028 cm⁻¹
Supporting groups: aromatic_ring_mode, c_h_in_plane_bend
Basis sources: S2, S3, S4
Summary: The 1028 cm⁻¹ band appears in PS spectra (S2: 1027/1029, S3: 1027, S4: 1028) and is consistent with a mixed aromatic ring C-C stretching and C-H in-plane bending mode, though not explicitly assigned in the sources.
5.1 AI Reasoning Highlights (Distilled from Thinking Chain)
The following insights were extracted from the model's internal reasoning trace — sensitive system details removed, analytical substance retained:
The library retrieval process returned a top candidate with a similarity score of 0.0 and a name listed as "-", indicating that no specific compound could be matched with any confidence. The adjusted similarity for this candidate was only 0.281, and the lead gap between the first and second-ranked candidates was 0.0, confirming a flat competition with no statistically meaningful best match. This lack of a credible entity-level identification precludes any assignment of a specific chemical name to the spectrum.
Analysis of the top 15 library candidates revealed a dominant and chemically coherent signal for halogenated compounds, with 12 out of 15 candidates containing a halogen functional group and 11 specifically containing fluorine. This strong statistical overrepresentation, despite the low absolute similarity scores, points toward a fluorinated material as the most probable broad classification. The library's own internal direction label, "halogen / fluorine," corroborates this finding.
Beyond the primary halogen/fluorine signal, a secondary cluster of oxygen-containing functional groups was observed in a significant subset of the top candidates. Groups such as acetate, methacrylate, ester, and carboxyl each appeared in 5 to 6 of the 15 candidates. The library's supporting group signals further specified "o_c_o," "methoxy," and "methacrylate," suggesting that if the material is fluorinated, it likely belongs to a class of fluorinated acrylate or methacrylate polymers or related esters.
The sample spectrum provided no observable peaks or feature rule hits, meaning there is zero direct experimental evidence to confirm or refute any functional group hypothesis derived from the library. The entire analytical direction is therefore based solely on the statistical trends within the low-similarity library retrieval results, introducing a high degree of uncertainty. The absence of characteristic C-F stretching absorptions (typically in the 1000-1400 cm⁻¹ region) or carbonyl (C=O) stretches (around 1700-1750 cm⁻¹) in the sample data prevents any validation of the proposed fluorinated ester structure.
The most chemically honest interpretation, given the weak and unconfirmed data, is that the unknown material is consistent with a halogen-containing, likely fluorinated, organic compound. The recurring presence of methacrylate and acetate groups in the candidate pool narrows the plausible direction to a fluorinated (meth)acrylate-type material, but this remains a bounded hypothesis. Key uncertainties blocking a firm conclusion are the complete lack of sample spectral features and the failure of the library to return any named chemical entities with meaningful similarity scores.
Scientific Background
Polystyrene (PS) is a thermoplastic produced by free-radical polymerisation of styrene. Its FTIR spectrum shows characteristic aromatic C-H stretching at 3026 cm⁻¹, 3060 cm⁻¹, and 3082 cm⁻¹, clearly distinct from aliphatic C-H stretching (2850–2920 cm⁻¹). The aromatic ring C=C skeletal stretching at 1601, 1493, and 1451 cm⁻¹ provides key evidence for mono-substituted benzene identification.
The 700–800 cm⁻¹ region is highly sensitive to substitution pattern: mono-substituted rings (as in PS) produce two strong bands at 699 and 756 cm⁻¹, while ortho-, meta-, and para-substituted rings show completely different fingerprints. The 756/699 cm⁻¹ doublet identified by the LLM is the signature of polystyrene and effectively discriminates it from the library Top-1 fluorinated fatty acid.
Molecular vibration modes for aromatic C-H: stretching (νC-H), in-plane bending (δC-H, ~1028 cm⁻¹), and out-of-plane bending (γC-H, 700–900 cm⁻¹). Aromatic C=C has semi-circle and quadrant stretching near 1600 and 1493 cm⁻¹. Aliphatic methylene: asymmetric stretching (2923 cm⁻¹), symmetric stretching (2850 cm⁻¹), scissor bending (1451 cm⁻¹). See the IR Absorption Frequency Table for cross-reference.
Interference factors: CO₂ produces an inverted band near 2349 cm⁻¹; water vapour causes broad absorption at 3400 cm⁻¹ and 1630 cm⁻¹, potentially masking weak O-H/N-H signals. In ATR mode, low-wavenumber intensities are affected by crystal refractive index and contact pressure, requiring ATR correction. The LLM also noted peaks at 1155, 1188, and 907 cm⁻¹, suggesting possible acetate or methacrylate comonomer units (ester C-O stretching).
Key distinction from fluorinated fatty acids: the fluorinated acid shows strong C-F stretching near 1199 cm⁻¹ and a carboxyl C=O near 1700 cm⁻¹, while polystyrene shows clear aromatic C-H stretching at 3026–3082 cm⁻¹ and the mono-substituted ring out-of-plane bending doublet at 699/756 cm⁻¹. With Top-1 similarity of only 0.6731, the LLM direction is more consistent with the spectral evidence — demonstrating the value of multi-source fusion.
- Typical Applications
- Further Reading
en&2Foam packaging and thermal insulation: EPS/XPS boards for building envelopes, cold storage, and logistics. FTIR is used to distinguish PS grades and detect recycled content.
Appliance and electronic housings: HIPS, ABS, and other styrenic copolymers. FTIR distinguishes homopolymer from copolymer and identifies flame retardants and plasticisers.
Disposable food packaging: transparent PS sheet for cup lids and cutlery. FTIR identifies PS versus PET, PP, and other plastics during recycling to prevent cross-contamination.
Calibration standards: polystyrene film is the standard material for FTIR wavelength calibration and resolution testing; peaks at 1601/1493/1583/1944 cm⁻¹ are referenced in multiple instrument verification standards.
IR Absorption Frequency Table — full-range functional group / wavenumber reference
Substance detail page — background, typical spectra, and applications
Functional group: hydroxyl — vibration modes and literature basis
Functional group: methoxy — vibration modes and literature basis
Functional group: methacrylate — vibration modes and literature basis
Functional group: c-o — vibration modes and literature basis
Functional group: fluorine — vibration modes and literature basis
Peak 1199 cm⁻¹ — assignment and literature traceability
Peak 1210 cm⁻¹ — assignment and literature traceability
Peak 1268 cm⁻¹ — assignment and literature traceability
Peak 3026 cm⁻¹ — assignment and literature traceability
Peak 3060 cm⁻¹ — assignment and literature traceability
Peak 3082 cm⁻¹ — assignment and literature traceability