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Resources/Ion Guides/Nitrite

Nitrite

NO₂⁻

The ELIT nitrite electrode requires careful attention to oxidation and temperature. The special citrate/phosphate ISAB is essential for maintaining pH and measurement accuracy.

Anion (−)ELIT 8071Valence: Monovalent
Safety Warnings
  • Nitrite standard solutions oxidise rapidly in air — store in refrigerator and prepare fresh daily.
  • Measuring at temperatures above ~30°C is not recommended.
  • Electrode may need extended soaking (overnight or several days if new or unused for months) before reliable use.
Electrode Specifications
Model
ELIT 8071
Membrane Type
Solid-state PVC polymer matrix membrane
Ion Type
Monovalent anion
Molar Mass
46.006 g/mol — 1000 ppm = 0.022 M
Physical Size
130 mm body (excl. contact) × 8 mm diameter. DC resistance < 2.5 MΩ at 25°C. Min. sample volume: 5 ml.
Operational Specifications
Concentration Range
0.5 to 500 ppm (1×10⁻⁵ to 0.01 Molar)
Electrode Slope at 25°C
54 mV/decade
pH Range
pH 4.5 to 8
Temperature Range
0 to 50°C (do not measure above ~30°C)
Response Time
< 10 seconds (90% response)
Potential Drift
< 3 mV/day in 1000 ppm (8 hours)
Reagents
Reference Electrode
Single junction (ELIT 001).
ISAB / Buffer
Special buffer BS-2 (for water samples): dissolve 14.32g disodium phosphate and 15.37g citric acid in 1000 ml water. Mix all standards and samples with ISAB in a 1:1 ratio. For meat extracts use BS-1 (pH 3.8): 3.26g sodium acetate + 10 ml glacial acetic acid in 1000 ml water.
Standard Preparation
Dissolve 1.500g anhydrous sodium nitrite (NaNO₂) in 1 litre deionised water. Note relatively short shelf-life due to oxidation — make fresh before each analytical session and refrigerate.
Typical Applications
Food & Beverage AnalysisWater Quality MonitoringEnvironmental MonitoringIndustrial Process Control
Interference

The Selectivity Coefficient (SC) represents the approximate apparent increase in the measured concentration caused by 1 unit of the interferent. Effect (% error) = (interferent concentration × SC / analyte concentration) × 100.

Interfering IonSelectivity CoefficientNotes
Cyanide (CN⁻)very highMust be completely absent.
Acetate (CH₃COO⁻)0.001—
Fluoride (F⁻)0.0008—
Chloride (Cl⁻)0.00005Would need to be 1000× more concentrated than nitrite to cause a 5% error.
Nitrate (NO₃⁻)0.00001—
Sulphate (SO₄²⁻)0.00001—
Standard Analytical Method

Apparatus Required

  • Ion-Selective Electrode: ELIT 8071
  • Reference electrode: Single junction (ELIT 001)
  • Dual electrode head (ELIT 201)
  • ELIT Computer Interface/Ion Analyser, or Ion/pH/mV meter
  • 150 ml polypropylene beakers, 100 ml volumetric flask, 1, 2, 5, 10 ml pipettes

Calibration

Calibrate with 200, 20, 2, 0.2 ppm NO₂ solutions. Mix all standards 1:1 with ISAB before measurement.

Sample Preparation & Measurement

Mix 25 ml sample with 25 ml ISAB before analysis. Keep standards and electrode in refrigerator when not in use; allow time to equilibrate to room temperature before use.

Results

Results are displayed as ppm and mol/l. If buffer solution has been added equally to standards and samples, figures will not need adjusting as all are affected by the same dilution factor. Allow 2–3 minutes stabilisation after electrode immersion. Wash and dry electrodes between samples to avoid cross-contamination.

Analytical Notes
  • Nitrite is prone to oxidation — refrigerate all solutions when not in use.
  • Note limited concentration range (0.5 to 500 ppm) compared to most other ELIT ISEs.
  • ISAB addition (1:1) is mandatory for all standards and samples.
  • Electrode reconditioning time after prolonged storage may be several days.