24 ANALYTICAL AND LABORATORY EQUIPMENT
Fig. 2, The SEAL QuAAtro39 and XY2 sampler.
SEAL has also built an auto- dilution feature into the discrete analysers for preparing standards automatically and handling over- range samples. Tese diluted sample results are automatically bracketed by QC sets.
Te reproducibility and detection limits of SEAL discrete analysers have been optimised by ensuring that each sample is read in the same optical glass cuvette with a 10mm pathlength.
Te sample is always read in the same position in front of the detector, which eliminates any potential issues with scratching or reaction well variability that can be found with direct-read systems.
Since the liquid is moved and not the tray; fewer moving parts maximises reliability.
Most discrete analysers employ miniaturised components to
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reduce reagent consumption and waste costs. For example, both the AQ1 and AQ2 analysers use just 20 to 400µl of reagent per sample.
Segmented flow autoanalysers Based on the original tried and tested technology of the Technicon/Bran Luebbe AutoAnalyzer, today’s SFAs deliver fast, accurate analysis for enormous numbers of samples; the QuAAtro for example can run up to 600 tests per hour.
SFA’s are also highly automated and once the analyser is configured and the reagents and samples are loaded, reliable unattended operation is a major benefit.
A basic SFA system consists of an autosampler, a peristaltic pump, a chemistry manifold, a detector and AACE data acquisition software.
Sample and reagents are pumped continuously through the chemistry manifold and air bubbles are introduced at precisely defined intervals, forming unique reaction segments which are mixed using glass coils.
With SFA, even slow reactions run to completion and the ratio of sample to reagents in the detector reaches a constant maximum value; the steady-state condition.
SFAs have been developed for running a few parameters on a larger number of samples, and the SEAL SFAs are the system of choice for marine and seawater organisations and anyone running very low nutrient waters.
Sensitivity Te SEAL AutoAnalyzer 3 and QuAAtro deliver high levels of performance and reproducibility, and are also the systems of choice
for tobacco, soil and fertiliser testing around the world.
Tese analysers provide maximum sensitivity by ensuring that the reaction always goes to completion, and with a digital true dual-beam detection system with real time referencing, the highest reproducibility and very lowest detection limits are achieved.
In summary, when choosing the most appropriate analytical technique, it is important to consider both the current and likely future needs of the laboratory.
So, it is good practice to contact a technical support team at an early stage because if the question is: “Which technique is better,” the answer is: “It depends…
Lalicia Potter is Technical Sales & Support Director at SEAL Analytical, Mequon, WI, USA.
www.seal-analytical.com
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