Description:
This invention introduces a simple, selective colorimetric sensor for sulfite detection, offering rapid, on-site, and reagent-free monitoring across food, pharmaceuticals, beverages, and water systems with high sensitivity and accuracy.
Background:
Sulfites are widely used as preservatives in food, beverages, and pharmaceuticals, but they can trigger allergic reactions and must be tightly regulated. Current detection methods often require specialized instrumentation, harsh reagents, or lengthy analysis times, making them impractical for routine or field testing. The absence of a rapid, safe, and reliable sulfite detection tool hampers compliance monitoring and consumer protection. A portable and selective solution is urgently needed to support food safety, pharmaceutical quality control, and environmental monitoring.
Technology Overview:
This invention utilizes 4-pyrrolylpyridine, a water-soluble colorimetric sensor compound, to selectively detect sulfite ions in aqueous solutions. The compound has a strong absorbance at 463 nm, which decreases upon reacting with free sulfites via an acid-catalyzed nucleophilic addition at the pyrrole ring. This reaction creates a visible bleaching effect, measurable by spectrometer or microplate reader. Sulfite concentration is determined volumetrically using the relationship [Sulfites] = 2520 / V (V in µL). The sensor shows excellent selectivity, unaffected by halides, phosphates, sulfates, or other common ions, and functions across a broad pH range, making it adaptable for diverse testing environments.
Advantages:
• Detects sulfites from 0.84 ppm to >10,000 ppm with high precision (±0.01 ppm)
• Selective response to free sulfites without interference from common ions
• Rapid visual analysis with simple bleaching effect—no hazardous reagents required
• Water-soluble and safe for direct use in food, beverage, and water testing
• Compatible with portable spectrometers for field-ready applications
• Low-cost and simple workflow using standard cuvettes or microplate readers
• Reduces false positives by detecting only free sulfites
Applications:
• Food and beverage testing (wine, beer, dried fruit, canned goods)
• Pharmaceutical quality assurance for sulfite content
• Consumer-use testing strips for sulfite allergy safety
• Environmental monitoring of water contamination by sulfites
• Industrial wastewater sulfite analysis and compliance monitoring
Intellectual Property Summary:
• US Provisional Application 62/569,193 – Filed October 6, 2017
• PCT Application PCT/US18/54770 – Filed October 5, 2018
• US Patent 11,953,479 – Application 16/753,906, Issued April 9, 2024
• US Utility Application 18/629,129 – Filed April 8, 2024, Pending
• European Patent Application EP18799905.7 – Nationalized from PCT/US17/65637
• Australian Patent 2018345841 – Status: Abandoned
Stage of Development:
Patented and validated – Demonstrated sulfite quantification via UV–Vis absorbance across a broad concentration range; compatible with portable devices for field deployment. TRL ~6.
Licensing Status:
This technology is available for licensing.
Licensing Potential:
Attractive to food safety testing companies, pharmaceutical QA firms, and environmental monitoring providers seeking rapid, user-friendly, and accurate sulfite detection technologies.
Additional Information:
Validation data, calibration curves, and selectivity studies available upon request.
Inventors:
Alistair Lees, Lynn Schmitt