Automated Nutrients Analysis for Buoys in Sea-Water and Intercalibration

Abstract

The Nutrient Probe Analyser-4 (NPA-4) is an automatic chemical analyser for "in-situ" and continuous measurements, based on a new improvement of the exclusive analytical technology developed by Systea and named LFA (Loop Flow Analysis); LFA has permitted levels never reached before in analytical automation and in analyser miniaturisation. With NPA-4 probes, it is possible to analyse directly in the water up to four parameters with the same instrument, using a particular configuration of LFA technology, which allows the sequential analysis of more than one analytical method in a single analytical reactor (30 minutes for a complete 4 parameters cycle). It has been conceived to execute ammonium, nitrate-nitrite, nitrite and orthophosphate analysis at low concentration in sea water samples. The hermetic closed Loop provides full protection against background interference, a basic requirement for stable trace analysis. At the start of a cycle the loop is washed and filled with sample. The sample colour is measured for compensation. Small amounts of concentrated reagents are added and mixed with high intensity. The intensity of the colour of the reaction product is measured one or two colorimetric dual beam with silicon detector, depending on requested methods. The standard wet chemistries for nutrients analysis used in NPA-4 are the ones recommended by international standard The statistical test show that the results of automated and manual analyses agree for all the examined parameters. Precision of all four analyses is ≤ 3 % RSD. The Limit of detection of 5, 5, 2.5 and 2.5 µg/L were reported for N-NH 4 , N-NO 3 , N-NO 2 and P-PO 4 , respectively. Multiparametric on line analyzer: it is possible to connect to a data logger with analogue and digital signals, in order to have on line simultaneous analysis of the sample. A typical application is on line analysis of seawater on an oceanographic research buoy (Max-5m). It does not require any operator.

Coupling high frequency monitoring and bioassay experiments to investigate a harmful algal bloom in the Bay of Seine (French-English Channel)

“…The Wiz probe uses micro loop flow analysis (µLFA) for autonomous measurements of four nutrients (NO 3 -, PO 4 2-, NO2 -) using colourimetric methods and NH3 with a fluorimetric method (Azzaro, 2014;Moscetta et al, 2009). As the buoy has limited energy, measurements were only performed once a day.…”

Path to Impact for Autonomous Field Deployable Chemical Sensors: A Case Study of in Situ Nitrite Sensors

“…103,107 Reports documenting in-field use and instrument intercomparsions suggest the probes have been able to discriminate between low levels of nitrite (subμg/L) in oligotrophic waters and withstand exposure in coastal waters for weeks at a time. 51,103,107,108 One of SubChemSystems' (USA) current FDS, the Autonomous Profiling Nutrient Analyzer (APNA), is designed to measure submeter scale nutrient gradients in either autonomous interval or continuous data collection mode. 98 SubChemSystems' instrumentation has been reported to track nitrite and other nutrients in chemical plumes, 109 investigate thin plankton layers and the influence of stratification and turbulence, identify fine-scale structures of nitrite profiles, and investigate biogeochemical cycling at ecologically critical scales for model validation and support.…”

“…A series of in situ instrumentation from Systea S.p.A. (Italy) that includes the Nutrients Probe Analyzer (NPA), Deep-sea Probe Analyzer (DPA), and Water In Situ Analyzer (WIZ), carries out wet chemistry fluorimetric and absorbance based spectrophotometry within a micro Loop Flow Analysis (μLFA) fluidic system which effectively removes air bubbles, enables sequential batch analysis and manipulates the fluidic components for reaction, detection, wash, and calibration cycles . The Systea probes have autonomously collected and reported measurements of nitrite, nitrate, orthophosphate, and ammonia in an unmanned time series monitoring station, , at 1500 m depth, tethered to a solar and wind energy-powered platform, and in automated sensor networks spanning multiple years of operation in open natural waters. , Reports documenting in-field use and instrument intercomparsions suggest the probes have been able to discriminate between low levels of nitrite (subμg/L) in oligotrophic waters and withstand exposure in coastal waters for weeks at a time. ,,, …”

Application of the Nordtest method for “real-time” uncertainty estimation of on-line field measurement

“…Nowadays, several chemical laboratories estimate uncertainty for their measurement results according to the guides and standards available (Eurachem/CITAC 2012;Eurolab 2007; International Organization for Standardization 2012; Joint Committee for Guides in Metrology 2008; Magnusson et al 2011). At the same time, there is a global trend in which the measurements are carried out more often in situ by field measurement devices or sensors (Arola 2012;Azzaro 2013;Bourgeois et al 2001;Clinch and Worsfold 1987;Glasgow et al 2004;Tschmelak et al 2005;Valkama et al 2007;Wang et al 2004). These may function automatically or they are operated manually.…”