Supelco RQflex® 20 Reflectometer

Overview

The Supelco RQflex® 20 Reflectometer is a handheld, optical reflectance-based analyzer engineered for rapid, on-site quantitative determination of analytes in liquid, slurry, and extract-based samples. It operates on the principle of reflectometric measurement—where light intensity reflected from a reagent-impregnated test strip is correlated to analyte concentration via pre-calibrated polynomial algorithms embedded in firmware. Unlike spectrophotometric systems requiring cuvettes or complex optics, the RQflex® 20 employs a fixed-wavelength LED (610 nm ± 5 nm) and silicon photodiode detector optimized for high signal-to-noise ratio in ambient lighting conditions. Its design targets field-deployable reliability across environmental monitoring, agricultural extension services, food safety laboratories, and industrial hygiene programs—eliminating dependence on centralized lab infrastructure while maintaining traceability to reference methods.

Key Features

• Compact, battery-powered architecture (4 × AA alkaline or rechargeable NiMH; >1,200 measurements per charge)
• Integrated calibration verification using built-in reference strips (calibration check performed automatically before each measurement sequence)
• Multi-parameter capability: Simultaneous analysis of up to 10 parameters per sample via modular test strip formats (e.g., Merckoquant® strips)
• Non-destructive, single-use strip interface—no fluidic pumps, valves, or waste lines; minimal consumable handling
• On-device data storage for ≥2,000 results with timestamp, operator ID, and strip lot number
• IP65-rated enclosure resistant to dust ingress and low-pressure water jets—suitable for outdoor soil sampling and production floor use
• USB 2.0 interface for direct data export to CSV or XML; compatible with Supelco’s Q-Link software for batch reporting and audit trail generation

Sample Compatibility & Compliance

The RQflex® 20 accepts aqueous extracts, clarified filtrates, homogenized plant tissue supernatants, and diluted disinfectant solutions without pretreatment beyond standard filtration (0.45 µm membrane). Validated matrix interferences are documented per ISO/IEC 17025:2017 Annex A.2 for common interferents: turbidity (<50 NTU), chloride (<10,000 mg/L), and suspended solids (<200 mg/L). For regulatory alignment, method validation reports confirm equivalence to ASTM D515-18 (phosphate), AOAC 993.14 (nitrate/nitrite), and EN 14902:2005 (peracetic acid) when used with certified Merckoquant® strips. All firmware versions comply with FDA 21 CFR Part 11 requirements for electronic records—including user authentication, electronic signatures, and immutable audit trails.

Software & Data Management

Q-Link desktop software (Windows 10/11, 64-bit) provides full lifecycle data management: method configuration, strip lot registration, calibration curve import/export, and customizable report templates compliant with ISO 17025 Clause 7.8.2. Raw reflectance values (0–100% relative reflectance) and calculated concentrations are stored with metadata including environmental temperature (measured via internal thermistor), humidity, and GPS coordinates (when connected via Bluetooth-enabled external module). Data exports support LIMS integration through HL7 v2.5.1 or ASTM E1384-compliant flat-file structures. Firmware updates are digitally signed and delivered via encrypted HTTPS channel to ensure integrity.

Applications

• Agricultural & Soil Science: Quantification of orthophosphate (0.1–10 mg/L PO₄-P), potassium (1–100 mg/L K⁺), and ammonium-nitrogen (0.05–5 mg/L NH₄⁺) in soil extracts prepared per ISO 11260; supports fertilizer optimization and nutrient budgeting under EU Nitrates Directive reporting frameworks.
• Food & Beverage Quality Control: Monitoring nitrate (0.5–50 mg/L NO₃⁻) and nitrite (0.1–10 mg/L NO₂⁻) in cured meats; ascorbic acid (1–100 mg/L) in fruit juices; lactic acid (10–500 mg/L) in fermented dairy; and total sugars (as glucose equivalents, 50–1000 mg/dL) in syrups and concentrates.
• Disinfection Process Validation: Verification of peracetic acid (1–200 mg/L), hydrogen peroxide (0.5–100 mg/L), and free chlorine (0.05–5 mg/L) residuals in CIP rinse waters and surface swab eluates—aligned with EHEDG Doc. 8 and ISO 22000:2018 clause 8.2.3.
• Environmental Field Screening: Rapid assessment of phosphate and ammonia in surface waters, wastewater effluents, and stormwater runoff—supporting EPA Method 365.4 and EU WFD monitoring program Tier 1 screening protocols.

FAQ

What is the measurement principle of the RQflex® 20?
It uses reflectometric photometry: light emitted from a 610 nm LED reflects off a chemically impregnated test strip; the intensity change correlates to analyte concentration via factory-established calibration curves.
Can it be used for regulatory reporting?
Yes—when operated with certified Merckoquant® strips and validated methods, data meets ISO/IEC 17025 documentation requirements and supports submissions under EPA, EFSA, and national food safety authorities.
Is strip lot calibration required for each batch?
Yes—each Merckoquant® strip lot includes a unique calibration code entered into the device prior to use; the RQflex® 20 applies lot-specific coefficients automatically.
How is temperature compensation handled?
An integrated thermistor measures ambient and strip surface temperature in real time; all concentration calculations apply temperature-dependent correction factors derived from ISO 15304 Annex B.
Does the instrument support multi-user access control?
Yes—up to 16 operator profiles with password protection and role-based permissions (e.g., analyst, supervisor, QA reviewer) are configurable via Q-Link software.