A high sensitivity method for the determination of nanomolar concentrations of Nitrate and Nitrite in seawater with a technicon autoanalyzer II

Feasibility of using an automated colorimetric procedure for the determination of seawater nitrate in the 0 to 100 nM range: Examples from field and culture

“…Standards were prepared in DIW or in artificial seawater (ASW, NaC1 38 g 1-1), and precautions were taken during their analysis according to the recommendations of Kerouel and Aminot (1987). Since a seawater (artificial or natural) wash is absolutely essential when working at high gains (the use of DIW would cause "schlieren", i.e., density differences between the sample and the DIW seawater), its quality must be tested according to the following procedure: establish baseline with DIW and omit Reagent 2 (optical zero); run a sample of seawater used for the wash cycle and measure the refractive effect (Froelich and Pilson 1978) -referred to as "salt effect" by Oudot and Montel (1988); replace Reagent2 and run another sample of the seawater used for the wash cycle, the signal obtained indicates the refractive effect plus the nitrate content of the seawater; then determine the nitrate concentration of the seawater from the latter signal after substracting the refractive effect and applying a calibration factor obtained from the nitrate standards. This procedure indicated that ASW contained 5 to 20 nM nitrate.…”

“…(LCD culture; 5 000 cells ml-1, particulate nitrogen=0.75/~M) and a high cell-density culture (HCD culture; 100 000 cells ml-1, particulate nitrogen= 13/~M) of Skeletonema costatum limited in nitrogen (zero nitrate in the culture medium). Samples were drawn from the medium by suction through a 10/~m-mesh net via the sampling tube; this avoids the problem of contamination during sampling and transfer, as noted by Oudot and Montel (1988). To start the experiment, the medium was spiked with a low quantity of nitrate; i.e., 17 nM for the LCD culture (Fig.…”

“…In order to overcome the latter drawbacks, Oudot and Montel (1988) modified the automated colorimetric standard procedure for the analysis of nitrate and nitrite in seawater (Strickland and Parsons 1972, Tr~guer and Le Corre •975). By only minor changes to the flow diagram of the Technicon AutoAnalyzer II, they were able to considerably extend the lower concentration-range limits of their original method.…”

The metabolic balance of the planktonic community in the North Atlantic Subtropical Gyre: The role of mesoscale instabilities

“…Inorganic nutrients were measured colorimetrically by Continuous Flow Analysis, by use of a six-channel Technicon-Bran Luebbe AA II AutoAnalizer. Nanomolar concentrations of nitrate were measured as described by Oudot and Montel (1988). After preliminary test CTD casts, incubators were set at the in situ temperature and irradiance found at four discrete depths: surface, thermocline, deep chlorophyll a maximum, and the depth receiving 1% of the surface irradiance (Table 1).…”

A submersible battery‐powered flowinjection (FI) sensor for the determinationof nitrate in estuarine and coastal waters

“…Several [27,28] or derivatization of the nitrate ion and detection in the visible region [29]. Indirect spectrophotometric methods require initial reduction of nitrate to nitrite by homogeneous [30,31] or heterogeneous [32][33][34][35][36][37][38][39][40] reduction methods using reduction columns of powdered or granular metals, e.g. zinc [32,33], amalgamated zinc [34], cadmium [35], amalgamated Cadmium [36,37] [22].…”