HIGH PRECISION NUTRIENT ANALYSIS in SEAWATER
SFA methods for high precision nutrient analysis
The high precision, robust design and low detection limit of SEAL Analyzers make them the first choice for seawater analysis. Leading seawater laboratory and research institutes world wide use AutoAnalyzer, QuAAtro and TrAAcs.
On Land and at Sea
SEAL Analyzers are designed to stand up to tough conditions on board an ocean-going research vessel, and are in routine ship-board use from the Arctic Ocean to the Weddell Sea. The latest instruments use LED light sources as they are unaffected by vibration and are extremely stable. A special bench fixing kit is available for the SEAL Analytical QuAAtro to quickly and securely mount it into a floating laboratory.
The Technology Advantage
Measuring and recording instrument performance
SEAL analyzers are the only SFA instruments which measure the precision of the bubble pattern, flowcell cleanliness, chemistry drift and other performance-critical parameters before and during a run. More than 30 hydraulic, optical, electrical and chemical parameters are quantified and written into a performance log which gives a long-term record of instrument and method performance.
Pre-run Check Quantifies System
A simple pre-run check quantifies the bubble pattern, baseline, detector, flowcell and light source in a few minutes and creates a printed record of the results. This is ideal for labs which need audit-able proof that the analyzer is working correctly, and as a valuable aid to troubleshooting.
High Precision Segmentation
On a SFA system the key factor in reproducibility, which is also critical for detection limit, is the composition of the liquid segments passing through the analyzer. Each segment must contain the same proportion of reagent and sample, and the arrival time of each segment at the reagent injection points must be very precise.
Seal Electronic Air Injection vs. Mechnical Air Injection
SEAL analyzers achieve this high precision with electronic air injection. The timing of the air injection is determined by a chopper wheel which intercepts a light beam:this triggers a solenoid valve to inject the air. In contrast, mechanical systems which use a cam and lever device are less accurate even when new, and the air timing becomes progressively less precise as the pump ages. With mechanical air injection the bubble precision on a typical nutrient manifold is around 2%. With electronic injection it is improved to less than 1%. On the QuAAtro, which generated these peaks, it was 0.2%.
Colorimeter Design
Low noise and drift
• Sample and reference detectors are installed close together in a massive aluminum housing to ensure temperature equilibrium.
• The signal is immediately digitized to prevent inductive interference.
• Same-wavelength blank correction compensates for the unavoidable spectrum changes with filament temperature when using a lamp as the light source
• Ultra low noise electronics contribute less than 3% to total measurement uncertainty.
LED light source
• Developed for trace-level on-board seawater analysis.
• Very stable, long life, completely immune to vibration.
• Available for all nutrient parameters.
• Tested in a Force 10 gale and subsequently proven in many ship laboratories around the world.
• Due to the detectors extremely low noise a short path length cell can be used. This maximizes light transmission and minimizes the refractive index blank RIB.
• Bubble-through-the-flowcell operation maintains separation between sample and wash and prevents "horns" at the start and finish of sample peaks whose salinity varies from the wash.
• Concentric sapphire light pipes in direct contact with the measured liquid lead the light into and out of the flowcell. Together with the narrow angle light source from an LED this provides a near-parallel light beam which further reduces the refractive index blank compared to conventional cells.
