Preventing Moisture Retention Agents from Becoming Ineffective with Ion Chromatography

The 2025 CCTV "March 15" Consumer Rights Gala has once again highlighted the severity of food safety issues in China, this time exposing the "water-retaining shrimp" scandal.

 

The 2025 CCTV "March 15" Consumer Rights Gala has once again highlighted the severity of food safety issues in China, this time exposing the "water-retaining shrimp" scandal. Water-retaining agents, commonly composed of compound phosphates, are typically used to preserve moisture in shrimp, enhance texture, and extend shelf life. This practice, referred to in the industry as "water retention" or "soaking treatment," has been exploited by some companies to increase shrimp weight through excessive use of these agents.

 

Despite strict national regulations on the amount of phosphates permitted in frozen seafood, some companies have ignored these limits and customized shrimp products based on customer demand. For instance, one company was found to have added phosphates at levels as high as 30‰, with soaking times exceeding ten hours and a moisture retention rate reaching 20%. This led to dangerously excessive phosphate levels in the shrimp, yet the company’s management showed complete disregard for the consequences.

 

Health Risks of Excessive Phosphate Consumption

Studies indicate that long-term excessive intake of phosphates can pose serious health risks, including digestive disorders, calcium-phosphorus imbalance, calcium deficiency, and even an increased risk of cardiovascular diseases.

 

This scandal not only exposed the rampant abuse of food additives but also brought ion chromatography technology into the spotlight. As the "gold standard" for detecting phosphates, how can ion chromatography serve as a powerful tool in tackling food safety challenges?

 

 

Sample Testing Plan I. Introduction

In recent years, phosphates have been widely used as water-retaining agents in the frozen seafood industry. However, the overuse of these additives has raised significant food safety concerns. On March 15, 2025, CCTV's "March 15" Gala exposed multiple cases of excessive phosphate use in shrimp products, posing severe health risks to consumers. Overconsumption of phosphates can disrupt calcium-phosphorus metabolism, increase cardiovascular disease risks, and even have toxic effects on individuals with chronic kidney disease. Moreover, Chinese seafood exports have repeatedly been flagged by the EU RASFF (Rapid Alert System for Food and Feed) due to excessive phosphate levels, highlighting mounting international regulatory pressure.

 

Currently, phosphate testing faces two major challenges:

 

1. Complexity of phosphate compounds – including orthophosphate, tripolyphosphate, and hexametaphosphate, which traditional colorimetric methods struggle to distinguish.

2. Interference from food matrices – proteins and lipids in shrimp may affect detection accuracy, necessitating optimized sample preparation to improve specificity.

 

This study establishes a high-efficiency, precise multi-phosphate detection system based on ion chromatography, providing robust technical support for food safety monitoring. By optimizing sample preparation and chromatographic conditions, we aim to eliminate interference from complex matrices and achieve simultaneous quantification of multiple phosphate species. This method supports the crackdown on illegal additive use, safeguarding consumer rights and ensuring compliance with international trade regulations.

 

II. Sample Preparation

1. Weigh 2.5g (accurate to 0.0001g) of homogenized shrimp.

2. Wash the sample into a 100mL volumetric flask using 50mmol/L sodium hydroxide solution, mix thoroughly, and dilute to volume.

3. Perform ultrasonic extraction at 80°C for 30 minutes, shaking every 5 minutes to ensure complete dispersion of the solid phase.

4. Cool to room temperature, then filter the solution and centrifuge at 8000 rpm for 10 minutes at 4°C.

5. Dilute the sample solution as necessary and pass it through a 0.45μm aqueous filter membrane and a RP-Ag-Na pretreatment column. Discard the first 3mL of eluate and collect the remainder for analysis.

 

III. Chromatographic Conditions

● Ion Chromatography System: M1

● Column: IonPac AS-11HC

● Guard Column: OR-AG

● Suppressor: OES-100+ Anion Suppressor

● Conductivity Detector: ORDZ-2

● Flow Rate: 1.0 mL/min

● Column Temperature: 30.0°C

● Detector Temperature: 30.0°C

● Injection Volume: 100 μL

● Suppressor Current: 240mA

 

Eluent: KOH gradient elution (see Table 1 for conditions).

Table 1: Ion Chromatography Gradient Elution Conditions

Sequence	Time (min)	OH⁻ Concentration (mmol/L)	Duration (min)
1	0.0	25	7.0
2	7.0	50	8.0
3	8.0	80	30.0
4	30.1	25	35.0

 

IV. Results and Discussion 1. Standard Calibration Curve

A series of standard phosphate solutions were prepared using orthophosphate, pyrophosphate, trimetaphosphate, and tripolyphosphate at different concentrations (see Table 2).

 

Table 2: Standard Phosphate Solution Concentrations (mg/L)

Compound Name	Level 1	Level 2	Level 3	Level 4	Level 5
Orthophosphate	0.00	0.30	1.00	5.00	10.00
Pyrophosphate	0.00	0.30	1.00	5.00	10.00
Trimetaphosphate	0.00	0.30	1.00	5.00	10.00
Tripolyphosphate	0.00	0.30	1.00	5.00	10.00

 

2. Chromatographic Separation of Four Phosphate Compounds

The chromatographic separation results are shown in Figure 1, with peak retention times and resolution values listed in Table 3.

 

Table 3: Retention Time and Peak Separation Data

Compound Name	Retention Time (min)	Peak Area (mV*s)	Resolution (EP)
Orthophosphate	10.024	691.166	9.2
Pyrophosphate	12.426	1598.916	5.1
Trimetaphosphate	13.818	1119.674	5.2
Tripolyphosphate	15.774	2189.455	--

 

3. Conclusion

Using ion chromatography, we successfully analyzed orthophosphate, pyrophosphate, tripolyphosphate, and trimetaphosphate in shrimp samples, following the GB 5009.256-2016 national food safety standard. The results demonstrated excellent separation, strong linear relationships, high accuracy, and sensitivity, meeting the requirements for phosphate detection in shrimp and other meat products.

 

Final Thoughts: Technology as a Shield for Food Safety

As unethical food processing practices continue to challenge public trust, ion chromatography technology stands as a scientifically rigorous defense against food safety violations. The "water-retaining shrimp" scandal reminds us that stricter regulation alone is not enough—we must also leverage technological advancements. Every precise detection is a firm commitment to consumer health, reinforcing our responsibility to uphold food safety.