Portable Total Phosphorus Colorimeter
Portable spectrophotometric analyzer for rapid total phosphorus quantification in water samples using molybdenum antimony colorimetry, measuring 0.00-2.00 mg/L with 5% accuracy.
Louise Corscadden, PhD
Neuroscience · ConductScience
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The Portable Total Phosphorus Colorimeter LH-P35 is a field-portable spectrophotometric instrument designed for rapid quantification of total phosphorus in water samples. The instrument employs molybdenum antimony spectrophotometry at 620-625 nm wavelength, providing measurements across a 0.00-2.00 mg/L range with 5% accuracy. This compact analyzer enables on-site phosphorus monitoring without requiring sample transport to centralized laboratories.
The instrument's portability (220g, 180×68×26 mm) and LED light source make it suitable for field deployment in environmental monitoring programs. The molybdenum antimony method involves sample digestion followed by colorimetric detection of the molybdophosphoric acid complex, allowing direct measurement of both dissolved and particulate phosphorus fractions in natural waters.
How It Works
The LH-P35 operates on the principle of molybdenum antimony spectrophotometry, the standard colorimetric method for phosphorus determination in water. Sample phosphorus is first converted to orthophosphate through acid digestion and oxidation, breaking down organic phosphorus compounds and releasing bound inorganic phosphorus from particulates.
The orthophosphate then reacts with molybdate reagent under acidic conditions to form phosphomolybdic acid, which is subsequently reduced by antimony to produce a blue-colored complex. The intensity of this blue color is directly proportional to the phosphorus concentration and is measured spectrophotometrically at 620-625 nm wavelength.
The instrument's LCD light source provides stable illumination for consistent optical measurements, while the digital electronics convert light absorbance to phosphorus concentration using a pre-programmed calibration curve. Results are displayed in mg/L total phosphorus, representing the sum of dissolved orthophosphate, dissolved organic phosphorus, and particulate phosphorus fractions.
Features & Benefits
Model
- LH-P35
Product name
- Portable total phosphorus colorimeter
Test item
- Total phosphorus
Measuring range
- 0.00~2.00mg/l
Light source
- LED
Wavelength
- 620-625nm
Test method
- Molybdenum antimony spectrophotometry
Working condition
- 0~40°C, Rh: 0-90%
Automation Level
- manual
Brand
- ConductScience
Accuracy
- 5%
Dimensions
- 180mm*68mm*26mm
Weight
- 220g
Research Domain
- Analytical Chemistry
- Environmental Monitoring
Weight
- 0.49 kg
Dimensions
- L: 7.09 mm
- W: 2.68 mm
- H: 1.02 mm
| Feature | This Product | Typical Alternative | Advantage |
|---|---|---|---|
| Measurement Range | 0.00-2.00 mg/L | Entry-level portable colorimeters often offer narrower ranges or lower upper limits | Covers the full range of phosphorus concentrations typically encountered in natural waters and treated effluents |
| Measurement Accuracy | 5% | Field instruments commonly provide 5-10% accuracy depending on design complexity | Sufficient precision for most environmental monitoring and process control applications |
| Detection Method | Molybdenum antimony spectrophotometry | Some portable units use simplified colorimetric methods or test strip technologies | Employs internationally recognized standard method ensuring reliable, comparable results |
| Operating Wavelength | 620-625 nm | Varies by model and detection chemistry used | Optimized for maximum sensitivity to phosphomolybdate complex while minimizing interferences |
| Portability | 220g, 180×68×26 mm | Portable colorimeters typically range from 200g to 1kg depending on features | Compact size enables easy field deployment without compromising measurement capability |
| Operating Temperature Range | 0-40°C | Most field instruments operate within similar temperature ranges | Suitable for year-round field use in most climatic conditions |
The LH-P35 provides standardized molybdenum antimony methodology in a compact, lightweight package suitable for field deployment. The 0.00-2.00 mg/L range with 5% accuracy meets requirements for most environmental monitoring applications while maintaining portability for on-site analysis.
Practical Tips
Prepare fresh calibration standards weekly and verify instrument response with mid-range standard before each analysis session.
Why: Reagent degradation and instrument drift can affect accuracy over time.
Clean measurement cells thoroughly between samples and protect LCD light source from dust and moisture.
Why: Optical contamination is the primary source of measurement errors in portable colorimeters.
Allow samples and reagents to equilibrate to instrument operating temperature before measurement.
Why: Temperature variations affect color development kinetics and optical density readings.
Process blanks and standards alongside samples using identical reagent lots and preparation procedures.
Why: Reagent variability and preparation differences can introduce systematic bias in results.
If readings drift or become erratic, check for air bubbles in measurement cells and verify light source stability.
Why: Optical path disruption is a common cause of measurement instability in field instruments.
Analyze duplicate samples and calculate relative percent difference to assess measurement precision.
Why: Replicate analysis helps identify random errors and validates analytical performance.
Use appropriate personal protective equipment when handling acid digestion reagents and ensure adequate ventilation.
Why: Phosphorus analysis involves strong acids that pose chemical hazards requiring proper safety precautions.
Setup Guide
What’s in the Box
- Portable Total Phosphorus Colorimeter LH-P35 main unit
- Power adapter or battery compartment (typical)
- Sample cuvettes or measurement cells (typical)
- Calibration standards set (typical)
- User manual and quick reference guide (typical)
- Carrying case (typical)
Warranty
ConductScience provides standard one-year manufacturer warranty covering defects in materials and workmanship. Technical support includes calibration assistance and method troubleshooting.
Compliance
What sample preparation is required for total phosphorus measurement?
Total phosphorus requires acid digestion to convert organic and particulate phosphorus to orthophosphate. Sample digestion typically involves persulfate oxidation or acid hydrolysis at elevated temperature before colorimetric analysis.
How does measurement accuracy compare to laboratory spectrophotometers?
The 5% accuracy specification is suitable for field monitoring and screening applications. For research requiring higher precision, laboratory instruments may provide 1-2% accuracy but lack field portability.
Can the instrument measure dissolved phosphorus separately from total phosphorus?
The instrument measures whatever phosphorus form is present after sample preparation. Dissolved orthophosphate can be measured directly, while total phosphorus requires digestion. Consult product datasheet for specific sample preparation protocols.
What interferences affect molybdenum antimony phosphorus measurements?
Common interferences include arsenate, silicate, and high concentrations of iron or organic matter. Proper sample preparation and reagent composition minimize most interferences in typical water samples.
How frequently does the instrument require calibration?
Calibration frequency depends on usage intensity and accuracy requirements. Daily verification with standards is recommended for continuous monitoring, with full recalibration when drift exceeds acceptable limits.
What is the minimum sample volume required for analysis?
Sample volume requirements depend on the cuvette or cell design used with the instrument. Consult product datasheet for specific volume specifications and any sample dilution protocols.
Can results be exported or logged for data management?
Data export capabilities are not specified in the basic product information. Consult product datasheet for available connectivity options and data logging features.
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