Selecta Bloc Digest Electric Heating Digestion System
| Brand | Selecta |
|---|---|
| Country of Origin | Spain |
| Model | Bloc Digest |
| Instrument Type | Electric Heating Digestion Instrument |
| Automation Level | Semi-Automatic |
| Temperature Range | 45–450 °C |
| Programmable Steps per Method | Up to 4 |
| Stored Methods | 20 |
| Digestion Tube Capacity Options | 6, 12, 20, 24, or 40 positions |
| Tube Sizes | 100 mL and 250 mL |
| Interface | RS-232 |
| Exhaust Treatment System | Integrated chemical scrubbing with recirculating water vacuum pump |
| Noise Level | <65 dBA |
| Construction Materials | Chemically resistant polymers and stainless steel components |
Overview
The Selecta Bloc Digest Electric Heating Digestion System is a precision-engineered semi-automatic digestion instrument designed for controlled thermal decomposition of organic samples prior to quantitative nitrogen analysis via Kjeldahl methodology. It operates on the principle of acid-catalyzed wet digestion—typically using concentrated sulfuric acid and catalysts—at elevated temperatures to mineralize organic matter into ammonium sulfate. The system delivers uniform, reproducible heating across all digestion tube positions through a solid-state metal heating block, ensuring consistent reaction kinetics and minimizing inter-sample variability. Its operational temperature range (45–450 °C) accommodates both low-temperature pre-digestion steps and high-temperature final charring, enabling full method flexibility in compliance with standard protocols such as ISO 5983, AOAC 984.13, and USP <467>. The Bloc Digest is not a standalone analytical device but a critical sample preparation module intended for integration into complete Kjeldahl workflows—including distillation and titration units—within QC laboratories, agricultural testing facilities, food safety centers, and environmental monitoring labs.
Key Features
- Programmable digital controller supporting up to 20 user-defined digestion methods, each configurable with up to four sequential temperature/time segments for precise thermal ramping and hold profiles.
- High-uniformity aluminum heating block with embedded Pt100 sensor feedback loop, delivering ±2 °C temperature accuracy and spatial homogeneity across all tube positions.
- Modular platform architecture: available in six configurations (Bloc Digest 6, 12, 20, m12, m24, m40) to match throughput requirements—from research-scale validation to routine high-volume testing.
- RS-232 serial interface enables bidirectional communication with laboratory information management systems (LIMS) or custom PC-based control software for audit-trail generation and remote parameter monitoring.
- Integrated exhaust treatment system comprising a chemically resistant recirculating water vacuum pump (<65 dBA) and dual-stage scrubber bottles filled with alkaline absorbent solution (e.g., NaOH or Na₂CO₃), eliminating need for continuous tap water supply while complying with local occupational health and safety regulations for acid fume containment.
Sample Compatibility & Compliance
The Bloc Digest accommodates standard Kjeldahl digestion tubes (100 mL and 250 mL capacities), compatible with borosilicate glass or quartz variants. It supports a wide range of sample matrices including cereals, dairy products, meat, feedstuffs, soil extracts, and wastewater sludge. All models conform to IEC 61010-1:2010 safety standards for electrical equipment used in laboratory environments. The exhaust system meets EN 14175-3:2004 requirements for fume cupboard performance equivalence when operated under recommended ventilation conditions. For regulated environments (e.g., GLP, GMP, or ISO/IEC 17025-accredited labs), the RS-232 interface facilitates electronic record retention aligned with FDA 21 CFR Part 11 principles—provided the connected host system implements appropriate user authentication, audit trail logging, and data integrity controls.
Software & Data Management
While the Bloc Digest does not include proprietary PC software, its RS-232 interface supports ASCII-based command-response protocol documented in the technical manual. Laboratories may integrate it into existing LIMS or custom SCADA platforms using standard serial communication libraries (e.g., Python’s pySerial, LabVIEW VISA). Each digestion run logs timestamped temperature setpoints and actual readings (where enabled via optional firmware upgrade), allowing correlation with downstream distillation/titration results. Method storage is retained during power loss via non-volatile memory. Firmware updates are delivered via USB-to-serial adapter and require authorized service technician access—ensuring configuration stability in validated environments.
Applications
- Determination of total nitrogen content in food and feed according to AOAC Official Methods of Analysis.
- Protein quantification in dairy products, plant-based alternatives, and infant formula under ISO 8968 and IDF 20B standards.
- Soil fertility assessment and fertilizer efficiency studies requiring digestion of organic-rich sediment or compost samples.
- Environmental monitoring of nitrogen load in municipal wastewater influents and effluents per EPA Method 351.2.
- Pharmaceutical excipient characterization where residual protein or amine content must be verified prior to formulation.
FAQ
What digestion tube sizes are supported by the Bloc Digest system?
The system accepts standard Kjeldahl tubes of 100 mL and 250 mL volume. Tube holders are configured to match the selected model’s capacity (e.g., Bloc Digest 12 accommodates twelve 100 mL tubes or six 250 mL tubes, depending on bracket configuration).
Is the exhaust treatment system compatible with hydrochloric or nitric acid digestion protocols?
Yes—the scrubber bottle contents can be adjusted based on expected acid composition. For HCl fumes, sodium hydroxide solution is recommended; for NOx gases generated during nitric acid digestion, a mixture of hydrogen peroxide and sodium hydroxide provides effective oxidation and neutralization.
Can the Bloc Digest be validated for use in GLP-compliant laboratories?
Yes—its programmable method storage, temperature traceability via RS-232, and stable thermal performance support IQ/OQ/PQ documentation. Full validation requires site-specific risk assessment, calibration against NIST-traceable references, and integration testing with associated distillation units.
Does the water recirculation pump require periodic maintenance?
The pump includes a replaceable filter cartridge and sealed impeller assembly. Maintenance intervals are specified at 500 operating hours or annually—whichever occurs first—and are detailed in the service manual.
Are spare parts and technical support available outside Spain?
Selecta maintains an international distributor network with certified service partners in over 40 countries. Spare heating blocks, controllers, and exhaust components carry globally harmonized part numbers and are stocked regionally for ≤5-business-day delivery.
