>>Application
This method is applicable to wastewater with cadmium concentrations within the range of 0-5 mg/L.
>>Technical parameters
1. Measurement Method: Dithizone spectrophotometric method
2. Measurement Range: 0-2 mg/L, OEM 0-5mg/L
3. Accuracy: ≤±10%
4. Repeatability: ≤±5%
5. Measurement Cycle: Minimum cycle is 30 minutes; color development time can be adjusted flexibly between 5-30 min based on environmental conditions.
6. Sampling Cycle: Adjustable time interval (10-9999 min) or on-the-hour measurement mode.
7. Calibration Cycle: Adjustable at any interval from 1-99 days.
8. Maintenance Cycle: ≥168 hours, with each maintenance lasting ~1 hour.
9. Reagent Consumption: <0.50 CNY per sample.
10. Outputs: RS-232, 4mA-20mA, RS-485.
11. Environmental Requirements: Temperature-controlled indoor environment (recommended: 5-40°C); humidity 45%-85%.
12. Power Supply: AC 220±10% V, 50±1% Hz, 5A.
13. Dimensions: Height 1500 × Width 500 × Depth 450 mm.
14. Additional Features:
- Data retention during abnormal alarms or power outages.
- Touchscreen display and command input.
- Automatic discharge of residual reactants and resumption of operation after power restoration or system reset.
>>Feature
Unique Design: This product features a distinctive design that ensures lower failure rates, reduced maintenance requirements, minimal reagent consumption, and higher cost-effectiveness compared to similar products.
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Selector Valve Assembly:
- Enables flexible reagent sampling timing and diverse channel configurations.
- Minimizes dead volume for easy maintenance and extended service life.
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Micro-Dosing Unit:
- Utilizes a visual photoelectric system for precise reagent measurement, eliminating quantitative errors caused by peristaltic pump tube wear.
- Achieves accurate micro-dosing with 0.7 mL per dose, significantly reducing reagent usage.
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Sample Introduction Unit:
- Employs a peristaltic pump with negative pressure suction, creating an air buffer zone between reagents and the pump tube to prevent corrosion.
- Simplifies and enhances flexibility in reagent mixing.
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Sealed Digestion Unit:
- Operates under high-temperature and high-pressure conditions to accelerate reactions.
- Eliminates corrosion risks from volatile gases in open systems.
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Reagent Tubing:
- Uses imported modified PTFE (polytetrafluoroethylene) transparent tubing with an inner diameter >1.5 mm to minimize clogging by particulate matter in water samples.
>>Analytical Principle
The aqueous sample undergoes hot-block digestion (150°C ±5°C) with concentrated HNO<sub>3</sub> (1:1 v/v) followed by pH adjustment using ammonium citrate buffer. In alkaline medium (pH 10.0 ±0.1 maintained by NH<sub>4</sub>OH/NH<sub>4</sub>Cl buffer) with dithizone as the chromogenic agent, cadmium ions form a crimson-red Cd-dithizonate complex exhibiting maximum absorbance at 518 nm (ε = 8.5×10<sup>4</sup> L·mol<sup>-1</sup>·cm<sup>-1</sup>). A microprocessor-controlled portable photometer (e.g., Hach DR1900) quantifies cadmium concentration through dual-wavelength measurement (518 nm sample vs 650 nm reference), with calibration curves validated per EPA Method 200.7 requirements (linear range: 5-200 μg/L, LOD 1.5 μg/L).
