WO2015033003A1 - Procédé de détermination séquentielle de nitrite et de nitrate - Google Patents

Procédé de détermination séquentielle de nitrite et de nitrate Download PDF

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Publication number
WO2015033003A1
WO2015033003A1 PCT/ES2014/000144 ES2014000144W WO2015033003A1 WO 2015033003 A1 WO2015033003 A1 WO 2015033003A1 ES 2014000144 W ES2014000144 W ES 2014000144W WO 2015033003 A1 WO2015033003 A1 WO 2015033003A1
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nitrate
determination
nitrite
sample
abs
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PCT/ES2014/000144
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English (en)
Spanish (es)
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Alfonso CORZO RODRÍGUEZ
Emilio Guillermo GARCÍA ROBLEDO
Sokratis PAPASPYROU
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Universidad De Cádiz (Otri)
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
    • G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
    • G01N21/78—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator producing a change of colour
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/18—Water
    • G01N33/182—Specific anions in water
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
    • G01N31/22—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators
    • G01N31/227—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators for nitrates or nitrites

Definitions

  • Nitrate is a key compound of the nitrogen cycle of natural ecosystems (oceans, estuaries, lakes, etc.) and in artificial environments (sewage treatment plants, reservoirs, drinking water supply networks, etc.), being a substrate and product of several microbial, vegetable and animal metabolic processes.
  • nitrate is produced by nitrification in a two-step reaction: oxidation of ammonium to nitrite and oxidation of nitrite to nitrate.
  • Nitrate can be assimilated by photosynthetic organisms, thus being an important nutrient in primary production studies.
  • Nitrate is also consumed in a variety of bacterial processes such as denitrification or dissimilatory reduction of nitrate to ammonium (DNRA).
  • DNRA dissimilatory reduction of nitrate to ammonium
  • Denitrification reduces nitrate to nitrous oxide, a potent greenhouse gas (Lashof & Ahuja 1990) or molecular nitrogen, another gas, reducing the nitrogen load of the system, while DNRA reduces nitrate to ammonium, biologically available that remains in the system (Megonigal et al. 2003). Therefore, the measurement of nitrite and nitrate concentration in aquatic systems is an important aspect of most studies related to the nitrogen cycle to determine its production and consumption levels.
  • Nitrates are also used in human activities, especially as fertilizers and food preservatives. When used as fertilizers, the concentration of nitrate in certain types of plant crops may increase. In addition, excess nitrate is washed and enters groundwater systems, lakes, or swamps, thereby contaminating drinking water supplies. In addition, nitrate in combination with nitrite is often used as a food preservative, particularly in sausages, and meats in general. We know that exposure to nitrate above certain levels has adverse effects on humans (eg increases adult cancer risk, blue baby syndrome, and childhood methemoglobinemia) (Greer al. 2005, Bryan et al. 2012, Bryan et al. 2013, Chan et al. 2013, Mart ⁇ nez et al. 2013), by measuring its level accurately and quickly is essential.
  • nitrate Numerous methods for the determination of nitrate are available in the scientific literature. Highly sensitive methods are based on the reduction of nitrate to nitric oxide, which is determined by chemical luminescence (Aoki et al. 1997, Braman and Hendrix 1989), or nitrous oxide and can be quantified by gas chromatography (Christensen and Tiedje 1988) . However, both techniques require specialized and expensive equipment. Other methods involve the use of strong acids frequently at elevated temperatures (Mir 2008, Zhang and Fischer 2006), which complicates the handling and analysis of the samples. On the contrary, the simplest and most commonly applied method involves the reduction of nitrate to nitrite and its consequent measurement by colorimetry using the Griess reaction (Grasshoff et al. 1983, Marzinzig et al. 1 97). The Griess reaction based method has the advantage of allowing a low detection limit, high precision and high specificity, without using expensive instruments or complex procedures.
  • the critical step of this method for the precise determination of nitrate is its efficient reduction to nitrite.
  • the reduction of nitrate to nitrite can be achieved with specific nitrate reductases (Guevara et al. 1998, Marzinzig et al. 1997) or by the use of different reducing metals, with cadmium being the most commonly used (Grasshoff et al. 1 83, Wood et al. 1967).
  • the average reaction efficiency was not improved.
  • the precision of the method was lower than using the classic Cd column for nitrate reduction.
  • FIG. 1 (A) Effect of the variation in temperature and concentration of the VC1 3 reagent in ION HCl on the reduction and measurement of the maximum absorbance for a solution of 15 ⁇ N0 3 " (2.5 mL standard + 250 ⁇ L reagent Griess + 250 reagent of VC1 3 ); (B) Effect of temperature variation and concentration of HCl (using 2% VC1 3 ) on the reduction and measurement of maximum absorbance for a solution of 15 ⁇ N0 3 ⁇ (2.5 Standard mL + 125 i Griess reagent +250 L VC1 reagent 3 ); (C) and (D) represent the reaction time required to reach maximum absorbance for (A) and (B) respectively.
  • FIG. 5 (A). Calibration curves obtained in the sequential measurement of N0 2 " and N0 3 " for N0 2 ' after step 1 (standard + Griess reagent) and separately for N0 2 " and N0 3 " after step 2 (sample + reagent Griess- + VC1 3 " reagent, reaction 25 minutes at 60 ° C); (B) calibration curves of N0 3 " (0 to 20 ⁇ ) measured in the presence of different concentrations N (3 ⁇ 4 " (0 to 20 ⁇ ). The measured absorbance is represented by points. The lines represent the values calculated using the calibration curves shown in (A) and in equation 4 of the text.
  • FIG. 6 (A) Linear regression comparing the cadmium and vanadium column methods.
  • B Vertical nitrate profile at the water sediment interface of the internal sac of the Bay of Cádiz (Spain) determined with the two methods.
  • C Horizontal transect of nitrate concentrations measured with the two methods along the Nicoya Gulf estuary (Costa Rica). Error bars in graphs (B) and (C) represent 95% confidence intervals.
  • the reagents are of analytical purity grade.
  • the Vanadium Chloride (III) reagent (VC1 3 ) at 2% w / v is prepared in a 6N hydrochloric acid solution (hereinafter VC1 3 reagent).
  • VC1 3 reagent 6N hydrochloric acid solution
  • the time needed for Complete dissolution is approximately 1 hour.
  • the complete dissolution is evident by the change from a cloudy to a transparent solution.
  • the solution is then filtered through a glass fiber filter of 0.7 ⁇ pore size to remove impurities from the reagent.
  • the starting solution for the preparation of the nitrate standards (Stock Solution) (10 mM) is prepared by dissolving 1,011 g KN0 3 dried in an oven (100 ° C, 1 h) in 1 L of pure water.
  • Stock solution of nitrite (10 mM) is prepared by dissolving 0.690 g NaN0 2 oven dried (100 0 C, 1 h) at 1 L of pure water.
  • Standard solutions were prepared in artificial seawater of the appropriate salinity for the salinity effect experiment.
  • Step 2 Determination of nitrite plus nitrate
  • VCI3 reagent equivalent to 0.1 times the volume of the sample and the Griess reagent remaining in the bottle is added in the same vial used previously and mixed.
  • the vial is closed to prevent evaporation and incubated at 60 0 C for 25 minutes.
  • the vial is cooled to room temperature, stirred and the absorbance at 540 nm is measured.
  • a spectrophotometer or microplate reader can be used to measure absorbance.
  • a temperature controlled water bath a heating block or a microplate reader with heating function can be used.
  • a temperature controlled water bath, a cooling block or a microplate reader with a cooling function can be used to cool the vials.
  • agitators or a microplate reader with a stirring function can be used to mix the samples.
  • Example 1 Using 1.5 mL eppendorf vials and a microplate spectrophotometric reader.
  • Step 1 Determination of nitrite
  • a sample volume of 1 mL was transferred to an eppendorf vial of 1.5 mL, followed by the addition of Griess reagent (50 ⁇ L) and mixed. Vials were incubated at room temperature ( ⁇ 25 0 C) for 20 minutes. Then, 350 of the solution (sample + Griess reagent) is transferred to 96-well flat bottom polystyrene microplates and the absorbance at 540 nm is measured.
  • the concentrations of N0 2 " are determined by parallel analysis of a set of N0 2 " standards of known concentrations.
  • Step 2 Determination of nitrite plus nitrate
  • a volume of 70 ⁇ L of VC1 3 reagent is added to the sample + Griess reagent remaining in the eppendorf vials used in step 1 (i.e. 700 ⁇ L) and mixed.
  • the vials were closed to avoid evaporation and incubated in a bath temperature controlled at 60 0 C for 25 minutes.
  • Once the vials are cooled to room temperature in a water bath, they are agitated and 350 ⁇ L of each is transferred vial a well of a flat bottom 96-well polystyrene microplate, and the absorbance at 540 nm is measured.
  • the determination of N0 3 " is carried out by means of the parallel analysis of a set of standards of N0 2 ⁇ and N0 3 " as described below in the calibration curves section, within this same section.
  • Example 2 Using a 1 cm spectrophotometer and cuvettes
  • Step 1 Determination of nitrite
  • volumes of 1 mL samples are transferred to 1.5 mL cuvettes, followed by the addition of 50 Griess reagent and agitated conveniently.
  • the cuvettes are incubated at room temperature ( ⁇ 25 ° C) for 20 minutes and the absorbance at 540 nm is measured.
  • the concentrations of N0 2 " are determined by parallel analyzes of a set of N0 2 ' standards of known concentrations.
  • Step 2 Determination of nitrite and nitrate
  • step 1 a volume of 100 iL of VC1 3 reagent is added thereto and stirred well.
  • the cuvettes are closed with a lid to prevent evaporation and incubated in a temperature controlled bath at 60 ° C for 25 minutes. After this time, the cuvettes are cooled to room temperature in a water bath and the absorbance at 540 nm is measured.
  • the determination of N0 3 " is carried out by means of the parallel analysis of a set of standards of N0 2 " and N0 3 " as described below in the calibration curves section, within this same section.
  • Example 3 Using microplates and a spectrophotometric microplate reader
  • Step 1 Determination of nitrite
  • a sample volume (for example 300 ⁇ ) is transferred to a well of a polystyrene microplate, followed by the addition of 0.05 volumes of Griess reagent (eg 15 uL) and mixed well.
  • the microplates were incubated at room temperature ( ⁇ 25 0 C) for 20 minutes and the absorbance of the sample at 540 nm is measured.
  • the concentrations of N0 2 " are determined by parallel analyzes of a set of N0 2 " standards of known concentrations.
  • step 1 a set of standards of different known concentrations of N0 2 ⁇ are used to determine the concentrations of N0 2 ⁇ in the sample using the equation:
  • ABS'N02 S ' N 02 X [O2] + ABS'reactive (1)
  • ABS ' N o2 is the absorbance of the standards of N ( 3 ⁇ 4 ⁇ ; S' N o2 is the slope of the calibration curve (ABS ⁇ "1 ) for N0 2 " ; [N0 2 " ] is the concentration of N0 2 " , and ABS'reactive is the absorbance of the reagents, that is, the intersection of the calibration curve
  • the measured absorbance (ABS v N ox) is a combination of the individual contribution of each compound (N0 2 " and N0 3 ) in addition to the absorbance of the reagents, ie:
  • ABS V NOX ABS V NO2 + ABS V NO3 + ABS v react i V os (2)
  • ABS V NO2 S V N02 [N0 2 ] + ABS V re reactive ( 3)
  • ABS V N0 3 S V N03 x [NOj-] + ABS v reagents (4)
  • ABS V N0 2 and ABS V N0 3 are the absorbance of the standards of N0 2 ⁇ and N0 3 ⁇ respectively;
  • S v N o2 and S V N O3 are the slopes of the calibration curves (ABS ⁇ " ') for N0 2 ⁇ and N0 3 ⁇ , respectively;
  • [N0 2 ⁇ ] and [N0 3 ] are the concentrations of the standards of N0 2 " and N0 3 " respectively and
  • ABS v rea ct ⁇ vos is the absorbance of the reagents without N0 2 " or N0 3 ⁇ ie the intersection of the calibration curve.
  • the measured absorbance is a combination of the individual contribution of each compound and the absorption of the reagents, that is, the combination of equations 3 and 4:
  • ABS v NO x S V N03 x [N0 3 ] + S V NQ2 x [N0 2 ] + ABS v reagents (5)
  • the concentration of N0 3 " of the sample is calculated as:
  • [N0 2 ] is the concentration of N0 2 " determined in step 1 and [N0 3 ] is the concentration of N0 3 " of the sample.
  • the detection limit (LOD) was calculated as 3 times the standard error of the interception, divided by the slope of the calibration line (Konieczka and Namiesnik 2009), resulting in a value as low as 0.04 ⁇ N0 3 ⁇
  • N0 3 " is often found in the sample along with N0 2 " , although generally the latter in much less concentration.
  • the N0 2 " interferes with the measurements using the Griess reagent. All protocols published to date require the reduction of N0 3 " to N0 2 " , followed by the determination of the sum of N0 2 " and N0 3 " (NO x ). Then N0 2 " is determined separately in another sample and the concentration of N0 3 " of the analyzed sample is determined by difference.
  • the protocol of Miranda et al. (2001) describes a spectrophotometric protocol using VC1 3 for the reduction of N0 3 " . However, they described a high interference of N0 2 " , the error in the determination of N0 3 "being proportional to the concentration of N0 2 " . As a result, the error in a sample with higher concentrations of N0 2 " than N0 3 " could be higher than the actual concentration of N0 3 " (Beda and Nedospasov 2005).
  • both the N0 2 " initially present in the sample and the N0 2 " produced in the reduction of N0 3 " contribute to the measured absorbance.
  • the molar absorptivity of N0 2 " in the absence of N0 3 " , decreases from a value of 0.042 to 0.036 ABS ⁇ " 1 after the addition of the VC1 3 reagent (Fig. 5A).
  • the method developed by Miranda et al. achieves lower molar absorptivities for N0 3 ⁇ than those observed with the present method due to 1) the greater volume of reagents used by these authors, resulting in a 1: 2 dilution of the sample and 2) a lower conversion efficiency
  • the molar absorptivities obtained were 0.0089 ABS ⁇ ⁇ 'which, after considering the molar absorptivities obtained for N0 2 " with the Griess reaction (about 0.038 ABS ⁇ " 1 ) and the dilution due to the addition of reagents as described in Your protocol would translate as a conversion efficiency of ⁇ 40%.
  • the absorbance obtained per mole of N0 2 ⁇ with the method of Miranda et al. (2001) is more than twice as large as for the N0 3 ⁇ .
  • the individual signal obtained for N0 3 ⁇ and N0 2 ' was not taken into account, resulting in lower precision and greater interference of N0 2 " .
  • the procedure proposed here achieves a similar absorbance signal for both compounds, resulting in minimal interference of N0 2 " and high accuracy.
  • the signal for N0 3 " and N0 2 " are obtained separately during calibration and is constant during each analysis regardless of the ratio N0 2 " : N0 3 " present in the sample. This was confirmed by the low error ( ⁇ 0.5 ⁇ ) measured in the determination of N0 3 " in standards with a range of concentrations of N0 2 " (Fig. 5B).
  • the concentration of N0 3 ' was, however, underestimated when the sum of the concentrations N0 2 " and N0 3 " (NO x ) exceeds 30 ⁇ , which is higher than the upper limit for the measurement of N0 2 " (Grasshoff et al. 1983).
  • a colorimetric kit could be produced using a portable heating system and a spectrophotometer for the determination of nitrate and nitrite in the same sample volume.
  • a flow injection analysis system can also be designed that will allow nitrite and nitrate to be measured in the same sample, using different channels or using the same channel, thus using half the amount of Griess sample and reagent.
  • the line used for nitrite determination could be recirculated after absorbance measurement for the determination of this compound.
  • the Vanadium reagent is added to the mixture consisting of the sample and the Griesss reagent and the nitrate + nitrite concentration is measured in the same or a different channel.

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Abstract

Le procédé selon la présente invention comprend une étape de détection initiale de NO2 - avec un réactif de Griess, suivie d'une réduction du NO3 - en NO2 - avec VCl3 et une détection ultérieure du NO2 - produit avec l'excès de réactif de Griess présent. Sa limite de détection est < 0,05 μΜ et offre une grande précision pour la détermination de NO2 - et de NO3 - dans des échantillons où la concentration cumulée des deux composés est inférieure à 30 μΜ. Il permet une analyse rapide de grandes séries d'échantillons, au moyen de petits volumes, en réduisant de moitié la quantité d'échantillon et de réactif de Griess utilisée. De plus, il permet de concevoir un système d'analyse par injection de flux pour mesurer le nitrite et le nitrate dans le même échantillon et le même canal, en utilisant la moitié de la quantité d'échantillon et de réactif de Griess qui est utilisée avec les méthodes traditionnellement employées.
PCT/ES2014/000144 2013-09-09 2014-09-08 Procédé de détermination séquentielle de nitrite et de nitrate WO2015033003A1 (fr)

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ES201300841A ES2533782B2 (es) 2013-09-09 2013-09-09 Procedimiento para la determinación secuencial de nitrito y nitrato.
ESP201300841 2013-09-09

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105954214A (zh) * 2016-04-27 2016-09-21 华南农业大学 一种三氯化钒混合粉剂及其在快速测定食品中硝酸盐含量方面的应用
WO2024023318A1 (fr) * 2022-07-29 2024-02-01 Hemera Procédé d'analyse chimique en phase gazeuse

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
BEDA, N. ET AL.: "A spectrophotometric assay for nitrate in an excess of nitrite.", BIOLOGY AND CHEMISTRY, vol. 13, pages 93 - 97 *
CECCHINI, S. ET AL.: "A Direct Spectrophotometric Assay for Evaluating Nitrate-Nitrogen in Intensive Aquaculture Systems.", THE ISRAELI JOURNAL OF AQUACULTURE -BAMIDGEH, vol. 64, 2012, pages 1 - 6 *
GARCIA-ROBLEDO, E. ET AL.: "A fast and direct spectrophotometric method for the sequential determination of nitrate and nitrite at low concentrations in small volumes.", MARINE CHEMISTRY, vol. 162, May 2014 (2014-05-01), pages 30 - 36 *
MIRANDA, K.M. ET AL.: "A Rapid, Simple Spectrophotometric Method for Simultaneous Detection of Nitrate and Nitrite.", NITRIC OXIDE: BIOLOGY AND CHEMISTRY, vol. 5, no. 1, 2001, pages 62 - 71 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105954214A (zh) * 2016-04-27 2016-09-21 华南农业大学 一种三氯化钒混合粉剂及其在快速测定食品中硝酸盐含量方面的应用
WO2024023318A1 (fr) * 2022-07-29 2024-02-01 Hemera Procédé d'analyse chimique en phase gazeuse
FR3138524A1 (fr) * 2022-07-29 2024-02-02 Hemera procédé d’analyse chimique en phase gazeuse

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ES2533782B2 (es) 2015-11-19

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