WWEM - Abstract

Abstract Information :

Why Discrete Analysis is a valid alternative to CFA (SFA and FIA) when it comes to soil testing for sediment testing on different pollutants, / nutrients. The determination of nutrients / pollutants in sediments and soils is typically a two-step procedure in terms of extraction process and analytical process. This first extraction process can be variable in terms of the intended analyte to extract and the type of sediment / soil to study. This variability is expressed in the use of different extraction process (matrices) and intended diluents. Additionally, these samples can have different background colour and its blanks can be entirely different from one sample (or sampling location) to another (Hatton et al, 1992), posing an additional level of diversity and complexity to the analytical work in the laboratory. These two variables pose a challenge to laboratories intending using automation solutions for the analysis of these nutrients / pollutants, both in sediments, soils and waters they receive on a continuous basis. Traditionally, laboratories have been using, and many are still considering, techniques such as Segmented Flow Analysis and Flow Injection Analysis, two techniques that provide a high degree of automation, at the same time than providing adequate Limits of Quantitation for specific nutrients and pollutants that can be found in different environmental samples and matrices. The aforementioned techniques, on the other hand are heavily impacted by the two listed variables on the analytical workload of a laboratory: on one hand, they cannot run a sample blank or sample background colour colorimetric adjustment for each and every sample, as the sample is mixed with reagents prior to arriving to the detector, what will impact on the reliability of results and will impact on the laboratory having to adjust its routine to each and every occasion the sample may present difference in colour or potential coloured turbidity. Additionally, for multi matrix samples, such as samples stabilized with different types of acid or alkali, or for samples that require different extraction steps / solutions, as they do require specific diluents, hence require specific diluent based blanks, calibration solutions, control materials preparation, such multiple matrix approach poses a challenge for complete automation as this either demands a batch testing approach or a multiple sampling system on the autoloaders. Segmented Flow and Injection Flow Analysis, although still current and valid for colorimetric testing, has evolved into Automated Discrete Analysis, that is today providing a valid and robust solution to the two main analytical challenges presented above. Discrete Analysers, thanks to its automation approach, can, individually, treat each sample and run all required blanks to determine its analyte concentration reliably, as each sample is loaded in a reading cuvette, where all reactions are run; this resolves the sample blank challenge present in both Segmented Flow and Flow Injection analysis. The multimatrix challenge is also adequately addressed by this type of analysers thanks to its design and analytical workflow. This presentation will, in depth, present how Discrete Analysis, addresses the two listed challenges, as well as its potential limitations for exceptional analytical cases, in terms of Limits of Quantitation.