Schuetz SILAREX-TOC Total Organic Carbon (TOC) Infrared Gas Sensor Module

Overview

The Schuetz SILAREX-TOC is a high-precision, dual-beam non-dispersive infrared (NDIR) gas sensor module engineered for the quantitative detection of carbon dioxide (CO₂) as a direct proxy for total organic carbon (TOC) in liquid-phase sample streams—particularly in ultrapure water systems used in power generation, pharmaceutical manufacturing, and semiconductor fabrication. Unlike conductivity-based TOC analyzers, the SILAREX-TOC employs a physical absorption measurement at the fundamental vibrational band of CO₂ (4.26 µm, 2350 cm⁻¹), eliminating reliance on secondary calibration artifacts or empirical correction factors. The sensor operates in flow-through mode, where post-oxidation effluent gases—generated by UV/persulfate or high-temperature catalytic oxidation of organic carbon in aqueous samples—are continuously swept through a thermally stabilized optical chamber. Its dual-beam architecture compensates for source drift, dust accumulation, and window fouling in real time, ensuring long-term baseline stability without routine zero/span recalibration.

Key Features

• Triple-range CO₂ detection (0–100 ppm, 0–1,000 ppm, 0–10,000 ppm), each with dedicated accuracy specifications and full-scale linearity compliance per ISO 14064-3 and ASTM D5905
• Sub-ppm limit of detection (0.15 ppm) achieved via optimized pathlength, high-emissivity pulsed IR source, and low-noise pyroelectric detector
• Integrated temperature-controlled optical chamber (42 °C setpoint), minimizing thermal gradient-induced refractive index shifts and reducing warm-up time to under 2 minutes
• Pressure-compensated signal processing using co-located absolute pressure and RTD sensors, correcting for barometric and flow-induced density variations
• Fluorinated glass optical windows resist chemical adsorption and particulate deposition, extending maintenance intervals in aggressive process environments
• Electropolished aluminum gas chamber ensures minimal surface reactivity and low memory effect for trace-level TOC monitoring
• Modbus ASCII/RTU digital interface supports seamless integration into SCADA, DCS, and LIMS platforms compliant with ISA-88 and ISA-95 frameworks
• Compact form factor (≤120 × 85 × 55 mm) enables OEM embedding in benchtop TOC analyzers, inline water quality monitors, or mobile emission testing units

Sample Compatibility & Compliance

The SILAREX-TOC module is designed exclusively for gaseous CO₂ detection downstream of validated oxidation reactors. It does not measure liquid-phase TOC directly but serves as the core transduction element in certified TOC analyzers meeting USP , EP 2.2.44, and JP 17 standards. Its performance aligns with IEC 61508 SIL 2 functional safety requirements when deployed in safety-critical boiler feedwater monitoring loops. For regulatory traceability, the sensor supports GLP-compliant audit trails when interfaced with software platforms compliant with FDA 21 CFR Part 11 (electronic records/signatures). It meets EMC Directive 2014/30/EU and RoHS 2011/65/EU, and its mechanical housing conforms to IP65 ingress protection when mounted with appropriate gland fittings.

Software & Data Management

Raw NDIR absorbance data is digitized onboard via a 24-bit sigma-delta ADC and processed by an embedded ARM Cortex-M4 microcontroller. Firmware implements real-time compensation algorithms for temperature, pressure, and spectral baseline drift. Modbus registers expose calibrated CO₂ concentration (ppm), raw detector voltage, heater status, diagnostic flags (e.g., flow fault, window contamination alert), and internal sensor health metrics. Optional firmware upgrades support configurable averaging windows (1–60 s), alarm hysteresis, and linearization tables for custom gas matrix corrections. When integrated into validated TOC analyzer systems, the module contributes to full electronic record retention—including method parameters, calibration history, and raw spectral snapshots—for GMP and ISO 17025 accreditation.

Applications

• Real-time TOC monitoring in fossil-fueled and nuclear power plant boiler feedwater circuits per GB/T 12145–2008 and VGB S006
• In-line verification of cleaning-in-place (CIP) efficacy in biopharmaceutical skids, supporting Annex 1 and EU GMP Chapter 3 compliance
• Ultrapure water (UPW) quality assurance in semiconductor fab fabs, where TOC < 1 ppb is required for 300 mm wafer processing
• Environmental compliance reporting for wastewater treatment plants transitioning from COD/BOD to TOC-based discharge permits
• OEM integration into portable TOC analyzers for field-deployable environmental site assessments

FAQ

Does the SILAREX-TOC sensor measure TOC directly in water samples?

No. It measures CO₂ concentration in the gas phase following complete oxidation of organic carbon in aqueous samples. TOC quantification requires integration with a certified oxidation subsystem and stoichiometric conversion logic.

Is this sensor compatible with high-purity steam applications?

Yes—when paired with a condensate sampling interface and cooled gas conditioning system (e.g., Peltier chiller + membrane dryer), it supports TOC monitoring in turbine steam cycle condensate per ASME PTC 19.11.

Can the sensor be calibrated without external gas standards?

Zero calibration may be performed using nitrogen or instrument air; span calibration requires certified CO₂-in-N₂ standard gases traceable to NIST SRM 1605 or equivalent national metrology institutes.

What is the expected service life under continuous operation?

Rated for ≥5 years MTBF under nominal conditions (24/7 operation at 25 °C ambient, 0.5 L/min flow, no exposure to halogenated solvents or H₂S).

Does the module support hazardous area installation?

Not intrinsically safe by default. For Zone 1/2 deployment, it must be housed in an ATEX/IECEx-certified explosion-proof enclosure or purged cabinet meeting EN 60079-13.