ISO 7158:2024
Meat and meat products — Determination of nitrite and nitrate content — Ion chromatography method

Standard No.

ISO 7158:2024

Release Date

2024

Published By

International Organization for Standardization (ISO)  IX  /  ISO

Latest

ISO 7158:2024

Introduction

Technical interpretation of the standard

ISO 7158:2024 adopts ion chromatography as the standard method for the determination of nitrite (NO₂^-) and nitrate (NO₃^-) in meat products for the first time. Compared with the traditional spectrophotometric method, this method has the advantages of good separation effect of ion chromatograph and strong anti-interference ability.

Method principle

After the sample is extracted with water, a protein precipitant combination (106g/L potassium ferrocyanide + 220g/L zinc sulfate) is used to remove matrix interference. After treatment with a C18/Ag/Na composite purification column, an anion exchange separation is performed using a hydroxide selective chromatographic column (4mm×250mm).

Parameters	Nitrite	Nitrate
Limit of Detection (LOD)	1 mg/kg	2 mg/kg
Limit of Quantitation (LOQ)	4 mg/kg	6 mg/kg
Repeatability RSD	≤3.0%	≤4.6%

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Key Operation Points

Sample Preparation

• The homogenization temperature should be controlled below 25℃
• Ultrasonic extraction frequency of 40kHz is recommended
• The purification column should be activated with 5mL methanol and 10mL water in sequence

Optimization of chromatographic conditions

The standard recommends a gradient elution program:

1. 6mmol/L KOH for 30min
2. 70mmol/L KOH for 5min
3. 6mmol/L KOH for 5min

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Implementation recommendations

Key points for quality control

1. The standard solution should be prepared on the same day (nitrite standard solution should be stored at 4℃ for no more than 2 weeks)
2. It is recommended to use an automatic sampler with cooling function
3. Each batch of samples should include a spike recovery experiment (the recovery rate is recommended to be controlled at 90-110%)

Method validation requirements

The laboratory needs to verify the following parameters:
- Linear range: NO₂^- 0.02-0.20mg/L, NO₃^- 0.2-2.0mg/L
- System suitability: adjacent peak separation ≥1.5

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Technology evolution analysis

Compared with the traditional Griess reagent method, the innovations of this standard are:
1. Simultaneous determination of nitrite and nitrate
2. Use of conductivity detector or UV detector (226nm)
3. The precision of the method was improved by about 40% (nitrite reproducibility RSD ≤ 7.6%)

ISO 7158:2024 Referenced Document

• ISO 3696 Water for analytical laboratory use; Specification and test methods

ISO 7158:2024 history

• 2024 ISO 7158:2024 Meat and meat products — Determination of nitrite and nitrate content — Ion chromatography method

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