ANALYTICAL AND LABORATORY EQUIPMENT 23
Discrete or continuous flow analysis – which is better?
A wide variety of factors affect the choice of analytical instrument. These include target workload (samples/hour), variety of chemistries, methods required, bench space, staff availability, etc. Here, Lalicia Potter examines one of the common decisions facing laboratory managers.
Le choix d’un instrument analytique est influencé par de multiples facteurs. Ces derniers comprennent la charge de travail cible (échantillons/heure), la gamme de produits chimiques, la place de travail requise par les méthodes et la disponibilité de l’équipe. Ici, Lalicia Potter examine une des décisions courantes auxquelles se voient confrontés les directeurs de laboratoire.
Verschiedene Faktoren beeinflussen die Wahl des Analysegerätes. Dazu zählen die Sollauslastung (Probe/Stunde), die Vielfalt der Stoffe, Methoden, die für die Arbeitsflächen- und Personalverfügbarkeit notwendig sind. In diesem Zusammenhang untersucht Lalicia Potter eine der üblichen Entscheidungen, mit der Laborleiter konfrontiert werden.
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n general terms, discrete analysers are ideal when automation is a priority and/ or when many and varied tests are needed on different samples. Segmented flow analysers (SFA) is suitable when a larger number of samples are to be analysed for a smaller number of chemistries. However, both techniques are
flexible, so it is important that expert advice is sought in the choice of analyser and that the instrument is configured to meet the precise needs of the laboratory.
As the manufacturer of an instrumentation range that includes both discrete analysers and continuous segmented flow analysers, SEAL Analytical’s technical support chemists are often asked which is the better technique. Both offer fast, automated, colourimetric analysis of multiple samples, however, the answer depends on the current and future analytical requirements of the laboratory.
SEAL’s discrete analysers employ sample trays and discrete reaction wells in which the colorimetric reaction takes place. In contrast, segmented flow analysers (SFA) employ a continuous flow of samples and reagent, segregated by air bubbles within tubing and mixing coils.
Discrete analysers In order to minimise operator involvement, SEAL’s discrete analysers are highly automated and simple to set up and run, even overnight.
A robotic sampling arm works in conjunction with a stepper motor-driven syringe that is responsible for aspirating, dispensing and mixing accurate and precise quantities of sample and reagent.
Te SEAL AQ1 and AQ2 discrete analysers can run seven different chemistries from each sample in the same run – and another seven in another run. Tese instruments have three separate wash stations including a unique probe washer, so cross- contamination is not a problem. Tis washing feature means that even ammonia (using Phenate), nitrate by cadmium reduction– (using ammonium chloride buffer) and low level phenol can be run together with no issues.
Fig. 1 The SEAL AQ1 and AQ2 (pictured) discrete analysers can run seven different chemistries from each sample in the same run.
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