A fast and direct spectrophotometric method for the sequential determination of nitrate and nitrite at low concentrations in small volumes

Abstract

The use of vanadium (III) has been proposed recently as a suitable alternative to cadmium for the reduction of NO 3 to NO 2 during spectrophotometric analysis. However, the methods proposed suffer from decreased sensitivity and additional steps for the measurements of nitrite and nitrate. We have developed an improved fast and sequential protocol that permits the determination of low concentrations of nitrite and nitrate in marine and freshwater samples using small volumes. NO 2 concentration is firstly determined using the common Griess reaction. The subsequent addition of a 2% VCl 3 solution in 6N HCl in the same sample and the reaction at 60ºC for 25 minutes results in an efficient reduction of the NO 3 to NO 2-(> 95%), which is also detected by the already added Griess reagents. The method has a detection limit <0.05 µM, a high precision (ranging from 0.2 to 11%) and accuracy (0.07 µM) for the determination of NO 3-+ NO 2 concentrations lower than 30 µM. Comparison of the proposed method with the established Cd column method using samples from a variety of environments (fresh water reservoir, sediment freeze lysable pore water, estuarine water samples and samples from an acid mine drainage impacted reservoir) showed good agreement between the two methods, with a difference between methods of 0.073 ± 0.099 µM. The analysis can be performed in large batches (~60 samples) using small sample volumes (≤1 mL) for the determination of both NO 3 and NO 2 in less than one hour.

Nutrient availability limits biological production in Arctic sea ice melt ponds

“…For determination of PO 4 3− , NO 3 − and Br − concentrations, 50 mL of the filtrate was stored frozen (−18 °C). PO 4 3− and NO 3 − concentrations were measured by standard procedures as described in Grasshoff et al (1983) and García-Robledo et al (2014), respectively, while Br − concentrations were measured using ion chromatography (IC, Dionex IC S-1500; Forster et al 1999).…”

Fixed-Nitrogen Loss Associated with Sinking Zooplankton Carcasses in a Coastal Oxygen Minimum Zone (Golfo Dulce, Costa Rica)

“…The coefficients of variation of replicated 15 NO − 3 , 15 NO − 2 , and 15 NH + 4 standards (n = 7-10) amounted to 4, 5, and 6%, respectively. Total nitrate and nitrite were analyzed spectrophotometrically (Garcia-Robledo et al, 2014). Total ammonium was analyzed with the salicylate method (Bower and Holm-Hansen, 1980).…”

Nitrite contents in various masticatories prevailing in the state of assam – a pilot study

“…Standard curve was plotted by using Sodium nitrite after incubating it with Griess reagent and the concentrations of nitrite in the sample were determined at 540nm using UV-VIS spectrophotometer (Shimadzu UV-1800, Kyoto, Japan). The aforementioned procedure was followed for all the 35samples divided in six batches and the average nitrite content for each sample was calculated [21] - [23]. …”