The Path of Advancement for China’s Standards on Analytical Methods for Pesticide Quality Control and an Analysis of the Gaps Compared with International Standards

As an essential input in agricultural production, the quality of pesticides directly affects food safety, environmental protection, and the efficacy of pesticide use. According to the “FAO/WHO Pesticide Codex—Pesticide Standards” (hereinafter referred to as the FAO Manual) and the “Requirements for Pesticide Registration Data,” the quality specifications for pesticide products should cover six aspects: appearance, active ingredient content, relevant impurities, other restricted components, additional control parameters, and storage stability. Among these, the additional control parameters are primarily used to assess the product’s physical properties, including density, surface characteristics, particle (fragment) size and adhesion, volatility, dispersibility, flowability, and solubility—indicators closely related to the pesticide formulation. Storage stability, on the other hand, encompasses three categories: thermal storage stability, low‑temperature stability, and freeze–thaw stability.

Other control parameters and storage stability are core elements for assessing the suitability and stability of pesticide products. In accordance with the relevant provisions of the “Requirements for Pesticide Registration Data,” currently registered technical-grade materials, parent compounds, and formulated products in China encompass a total of 48 other control parameters (excluding suspension seed‑coating agents) and three storage‑stability parameters. For the convenience of subsequent analysis and discussion, this paper uses the term “quality control parameters” to specifically refer to the two major categories—“other control parameters” and “storage stability”—as defined in pesticide product specifications, excluding such indicators as appearance, active ingredient content, related impurities, and other restricted components.

Establishing scientific and accurate analytical methods for quality‑control parameters is a crucial foundation for ensuring the quality of pesticide products. This paper systematically reviews the current status of the development and revision of national standards for analytical methods used in pesticide quality control in China, with a particular focus on those control parameters for which no corresponding analytical method standards have yet been established. It also compares the technical content of selected national standards with that of CIPAC methods, aiming to provide guidance for refining China’s pesticide quality‑standard system and to promote the ongoing enhancement of regulatory capacity for pesticide product quality.

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Current Status of the Development and Revision of National Standards for Analytical Methods in Pesticide Quality Control Projects in China

In terms of the number of standards, a total of 24 national standards for analytical methods used in quality control have been either published or are currently under development. These standards primarily cover active ingredients, technical-grade materials, and the three major formulation types. Specifically, for solid formulations, 15 quality‑control parameters have been standardized or are in the process of being standardized, achieving a coverage rate of 79%; for liquid formulations, 12 parameters are covered, with a coverage rate of 75%; and for seed‑treatment formulations, 12 parameters are covered, at a rate of 92% (Figure 1). Among these three major formulation types, several quality‑control parameters still lack corresponding national analytical method standards, including: four items for solid formulations—tablet integrity, disintegration time, abrasion rate, and dissolution of water‑soluble pouches; four items for liquid formulations—dilution stability, active‑ingredient release rate, miscibility with hydrocarbon oils, and viscosity—of which the latter two, though not yet codified in national standards, are already addressed by relevant industry standards; and one item for seed‑treatment formulations—dilution stability.

From the perspective of timing, the period from 2013 to 2024 marked the peak for the development of analytical method standards for pesticide product quality control, during which 12 new standards were issued, accounting for 50% of all such standards. At the same time, relevant authorities accelerated the revision of existing standards. Among the standards currently in force, four have been revised twice and four have been revised once, with an average revision interval of approximately 19 years.

From the perspective of standard content, the development and revision of national standards for analytical methods used in quality control of domestic pesticide products are primarily based on the methods of the Collaborative International Pesticides Analytical Council (CIPAC). As an internationally recognized gold standard for pesticide analysis, CIPAC methods are developed through a global, multi‑laboratory collaborative validation process, ensuring robust scientific rigor and excellent reproducibility. The technical content, development procedures, and validation frameworks of relevant domestic method standards draw upon CIPAC methodologies, thereby significantly enhancing the scientific soundness and practical applicability of these standards and accelerating their formulation and implementation. Below, we will conduct a detailed analysis of the development and revision of national standards for analytical methods used in quality control of domestic pesticide products, benchmarked against CIPAC methods.

In addition, it should be noted that the “Requirements for Pesticide Registration Data” categorize “other formulations” into 11 formulation types, covering 25 quality‑control parameters. Among these, several quality‑control parameters currently lack dedicated national analytical methods and corresponding CIPAC methods. For quality control of the relevant products, reference may be made to the methods listed in the FAO Manual, or to existing industry standards (Table 1). This paper does not elaborate on this aspect in detail.

Table 1: Summary of Reference Methods for Quality Control Parameters of Selected Preparations

Figure 1 Quality control items for formulation products for which national standard analytical methods have been established.

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Correspondence between National Standards for Analytical Methods in Quality Control and CIPAC Methods

By comparing the correspondence between China’s national standards for analytical methods used in pesticide quality control and the CIPAC methods (Table 2), three scenarios can be identified. First, CIPAC has established a method, whereas China lacks a corresponding standard; this category covers five control parameters. Second, China has developed a methodological standard, while CIPAC has not yet formulated an equivalent method; this involves two control parameters. Third, both China and CIPAC have established relevant methods; this scenario encompasses 22 control parameters. This paper focuses on comparing cases where CIPAC methods have been updated, but the corresponding domestic methods have not yet been revised. The following sections will elaborate on each of these three categories.

Table 2: Correspondence Between National Standards and CIPAC Methods for Analytical Procedures of Quality Control Items

2.1 Quality control items for which China has not yet established methodological standards

2.1.1 Tablet Disintegration

For effervescent dispersible and soluble tablets, the disintegration time must be determined in accordance with Annex 13 of the “Requirements for Pesticide Registration Data.” At present, China has not yet established a corresponding national standard analytical method; the drafting of some product standards often refers to the “Specification for the Preparation of Pesticide Dispersible Tablet Product Standards” (HG/T 2467.14–2003) or the “Specification for the Preparation of Pesticide Soluble Tablet Product Standards” (HG/T 2467.17–2003), with the disintegration time criterion stipulating that the time required for complete disintegration of the sample shall be ≤… min. The FAO Manual, recognizing that determining the endpoint of tablet disintegration in suspension solutions can be rather subjective and challenging, recommends evaluating disintegration performance by measuring the residual mass after a fixed disintegration time, with the acceptance criterion being: within the specified disintegration period, the weight of the residue shall not exceed …%. CIPAC has specifically developed Method MT 197 for assessing the disintegration of effervescent tablets, which involves adding the product to standard hard water, gently stirring until the prescribed disintegration time is reached, and then passing the mixture through a 2,000 μm test sieve to check for any residue; if residue is present, the weight of the material retained on the sieve must be measured.

2.1.2 Wear Rate

At present, China has not yet established a dedicated national standard for determining the abrasion rate of tablets. For certain tablet products with smaller diameters, the methods used to assess the abrasion resistance of granular formulations may be referenced. In 2023, the standards‑development authority, in accordance with the latest revision of MT 178.3, revised the original national standard “Method for Determining the Abrasion Resistance of Pesticide Water‑Dispersible Granules” (GB/T 33031), changing its title to “Method for Determining the Abrasion Resistance of Pesticides.” Following this revision, the scope of the standard has been expanded from water‑dispersible granules to include granular formulations, water‑dispersible granules, emulsion granules, soluble granules, as well as tablets with diameters less than 1 cm, water‑dispersible tablets, and soluble tablets.

In addition to MT 178.3, MT 193 also provides a method for determining the tablet abrasion performance. This method is based on the testing principle used in the pharmaceutical industry to assess tablet friability: tablets are placed in an abrasion‑resistance tester and subjected to cyclic rolling, after which they are passed through a 2 mm test sieve. The mass of the residue retained on the sieve is recorded, and the abrasion rate is calculated, thereby evaluating surface wear in uncoated tablets caused by vibration, friction, and other factors.

2.1.3 Dissolvability of Water-Soluble Bags

For water‑soluble formulations such as soluble powders, soluble granules, wettable powders, and water‑dispersible granules, it is necessary to control the solubility of the packaging bag to ensure that the sample does not clog the nozzles or filters of application equipment during dispersion or dissolution. At present, China has not yet established a specific national standard for determining the solubility of water‑soluble bags; in practice, analysts may refer to the CIPAC method MT 176.

2.1.4 Dilution Stability

China has not yet established a national standard for assessing dilution stability. At present, the determination of dilution stability for liquid formulations, soluble‑gel formulations, and seed‑treatment solutions in China primarily follows the “Specification for Preparation of Pesticide Liquid Formulations” (HG/T 2467.7‑2003): the sample is diluted 20‑fold with standard hard water, then incubated in a constant‑temperature water bath—typically for 1 hour—and the homogeneity of the diluted solution and the presence of any precipitates are observed. In 2010, CIPAC updated the method for determining dilution stability to MT 41.1. Compared with the aforementioned domestic procedure, MT 41.1 requires that the sample be diluted 20‑fold with standard hard water and held at a specified temperature for 24 hours; if precipitates form upon standing, the mass of the residue must be determined using the wet‑sieve test method described in MT 185. The FAO Manual adopts requirements for assessing dilution stability that are consistent with MT 41.1, while also specifying principles for selecting the test concentration: if the maximum recommended use concentration on the product label falls within the test concentration range of MT 41.1 (i.e., a dilution factor of ≥20), the test solution should be prepared at the recommended concentration; if the recommended concentration exceeds the upper limit stipulated in MT 41.1, the test should be conducted at the concentration prescribed in MT 41.1.

2.1.5 Release Rate of Active Ingredients

For formulations with sustained-release properties—such as microcapsule suspensions, microcapsule suspension–emulsion-in-water systems, microcapsule suspension–suspension systems, and microcapsule suspension–suspension‑emulsion systems—quality control requires monitoring the release rate of the active ingredient. CIPAC Method MT 190 specifies an analytical procedure for assessing the release performance of lambda‑cyhalothrin in microcapsule suspensions: a n‑hexane–ethanol solution containing an internal standard is added to a glass vial containing the sample; the vial is then rotated on a horizontal shaker for 15, 30, or 180 minutes, after which the n‑hexane layer is collected for gas chromatographic analysis to evaluate the release behavior of the active ingredient. At present, China has not yet established a unified national standard for determining release rates. In practice, an appropriate release medium can be selected based on the capsule wall material, and sampling and analysis should be conducted at three predefined time points. It is particularly important to ensure that, when setting product quality specifications, the release‑rate criteria for different time points are not redundant, so as to avoid compromising the accuracy of product‑quality evaluation.

2.2 Quality Control Items for Method Standards Developed Independently in China

In addition to “keeping pace” with CIPAC methods by referencing them in the development of domestic method standards, in recent years China’s standard‑setting authorities, in response to the practical needs of product quality control, have taken the lead in proposing and establishing two method standards, the details of which are set out below.

2.2.1 Freeze–Thaw Stability of Pesticides

For microcapsule formulations such as microcapsule suspensions, microcapsule suspension–emulsion-in-water, microcapsule suspension–suspension, and microcapsule suspension–suspension‑emulsion, exposure to freezing conditions during storage and transportation may cause rupture of the microcapsule wall material containing the active ingredient, thereby compromising formulation stability. At present, CIPAC has not established a standardized method for assessing freeze–thaw stability of pesticides; accordingly, China has developed the national standard “Method for Determining Freeze–Thaw Stability of Pesticides” (GB/T 43273-2023), drawing on relevant procedures from the FAO Manual. This method requires placing the sample in a freeze–thaw test vessel and subjecting it to alternating cycles between 20 ± 2 °C and −10 ± 2 °C (18 h at freezing temperature and 6 h at thawing temperature), repeating four cycles, after which the appropriate parameters are determined based on the product’s characteristics.

2.2.2 Determination of Insoluble Matter in Pesticide N,N-Dimethylformamide

Considering the special characteristics of acetone as a precursor chemical subject to strict control and limited procurement, as well as the practical needs of determining insoluble matter in technical‑grade pesticide products, China has, on the basis of the “Method for Determination of Insoluble Matter in Pesticides—Acetone” (GB/T 19138‑2003), additionally established the “Method for Determination of Insoluble Matter in Pesticides—N,N‑Dimethylformamide” (GB/T 43179‑2023). Compared with the acetone‑based method, GB/T 43179‑2023, taking into account the varying room‑temperature solubility of active ingredients in N,N‑dimethylformamide, retains the heating‑reflux method while also introducing a room‑temperature procedure. Specifically, the heating‑reflux method is suitable for samples that are poorly soluble in N,N‑dimethylformamide at room temperature but can be completely dissolved upon heating; given that the boiling point of N,N‑dimethylformamide is higher than that of acetone, the drying temperature in this method has been adjusted to 160°C. The room‑temperature method, on the other hand, is applicable to samples that dissolve directly in N,N‑dimethylformamide; after dissolution, the insoluble matter is determined by filtration through a glass sand‑core crucible funnel.

2.3 Control items for which the CIPAC methods have been updated but China has not yet adopted them

CIPAC methods exhibit a high degree of sophistication. With the continuous emergence of new technologies and products, CIPAC continually updates and refines its analytical methodologies to meet the evolving demands of pesticide quality control. The revision of domestic method standards is largely contingent upon the progress of CIPAC method updates. This paper compiles recent CIPAC methods that have been updated but have not yet been adopted or are currently being revised in China, and by comparing the technical differences between current national standards and the latest CIPAC methods, it offers guidance for the next phase of standard revision in China.

2.3.1 Persistent Foaming Property

In 2011, China developed the “Method for Determining the Persistent Foaming Properties of Pesticides” (GB/T 28137-2011), referencing MT 47.2. In 2012, CIPAC published MT 47.3, which superseded MT 47.2. Compared with MT 47.3, GB/T 28137-2011 differs significantly in several methodological details, including the sample size, graduated cylinder specifications, volume‑adjustment procedure, and standing time, as follows.

2.3.1.1 Differences in Sample Weighing Amounts MT 47.3 stipulates that samples should be weighed according to the product’s recommended concentration; if multiple concentrations are specified, the highest concentration shall be used. It should be noted that, following the publication of this method, CIPAC issued an erratum to MT 47.3, with revisions primarily addressing two points: first, the scope of application was amended to specify that the method applies to products with a recommended concentration ≥ 0.1% w/v; second, an additional note was added stating that for products with a recommended concentration < 0.1% w/v, the sample solution must be prepared using a concentration of 0.1% w/v; and when the recommended concentration exceeds 10% w/v, the volume of standard hard water D initially added to the graduated cylinder should be appropriately reduced so that the combined volume of the sample and the formulation is approximately 180 mL.

GB/T 28137-2011 specifies a sample size of 1 g for determining persistent foaming properties. For most pesticide products, this sample quantity adequately reflects the actual application concentration (with 1 g of sample typically diluted approximately 200-fold). However, for certain products with low active‑ingredient content and high application concentrations, this amount may not be sufficient to represent real‑world usage conditions. For example, the S‑abscisic acid soluble concentrate (PD20190126) is recommended for grapevine applications at dilutions of 170–250 times; the resulting field‑application concentration may exceed the dilution levels assumed in this method. This issue should be given due consideration in future revisions of the standard.

2.3.1.2 Requirements for graduated cylinders and methods of volume adjustment: GB/T 28137-2011 retained the specifications from MT 47.2, specifying a 250 mL stoppered graduated cylinder with a scale division of 2 mL, a distance of 20–21.5 cm between the 0 and 250 mL marks, and a gap of 4–6 cm between the bottom of the stopper and the 250 mL mark; during volume adjustment, the liquid surface was required to be 9 ± 0.1 cm below the bottom of the stopper. The newly issued MT 47.3, however, stipulates a 250 mL graduated cylinder (scale division of 2 mL, with the 0–250 mL marks spaced 20–26 cm apart and the stopper bottom positioned 3–7 cm below the 250 mL mark), and specifies a fixed adjusted volume of 200 mL. Compared with maintaining a fixed liquid‑surface height, directly setting a specific adjusted volume is more practical in routine operations.

2.3.1.3 Different standing times: GB/T 28137-2011 specifies that the foam volume is observed after a standing time of 1 min ± 10 s, whereas MT 47.3 requires measurements to be taken at both 1 min ± 10 s and 12 min ± 10 s. Nevertheless, in China today, as well as in the FAO Manual, the assessment of a product’s persistent foaming performance continues to be based on the criterion that “foam volume after 1 min ≤ 60 mL.”

2.3.2 Degree of Dissolution and Solution Stability

In 2016, China, drawing on the CIPAC method MT 179, established the national standard “Methods for Determining the Solubility and Solution Stability of Pesticides” (GB/T 32777-2016). In 2017, CIPAC published a newly revised version of the method, MT 179.1. Compared with MT 179.1, GB/T 32777-2016 exhibits the following key differences in specific test requirements and procedural details:

First, the specifications for the graduated cylinder differ (as do those for the persistent foaming‑test method). Second, the temperature setting for the standard hard water varies: GB/T 32777‑2016 specifies a test‑water temperature of 30°C, whereas MT 179.1 broadens the allowable range to 25±5°C, thereby enhancing the method’s practicality and ease of operation. Third, the procedural steps differ: GB/T 32777‑2016 requires that, after standing for 5 minutes, the solution be transferred to the test sieve with five rinses of 20 mL distilled water; after standing for 18 hours, the residue is washed with 100 mL distilled water prior to transfer to the sieve; and the insoluble material is then dried directly on the sieve. In contrast, MT 179.1 does not specify the volume of distilled water to be used when rinsing during solution transfer, instead requiring that the insoluble material on the sieve be transferred to a glass vessel before drying. Fourth, the observed parameters differ: GB/T 32777‑2016 mandates recording the weight of the residue on the sieve at both 5 minutes and 18 hours after standing, while MT 179.1 shifts the second observation time point to 24 hours, aligning with the FAO Manual’s requirements for assessing the degree of dissolution and solution stability of relevant formulations.

2.3.3 Pourability

In 2015, China issued the national standard “Method for Determining Pour‑out Residue of Pesticides” (GB/T 31737‑2015), which draws on MT 148 and specifies separate procedures for determining both the residue remaining after pouring and the residue remaining after washing. When establishing relevant product quality‑control criteria, the FAO recognized that the determination of pour‑out residue after washing is susceptible to factors such as container type and lacks a unified, widely applicable analytical method; accordingly, it did not include “pour‑out residue after washing” as a control parameter in product specifications. Instead, it stipulated that when the pour‑out residue is relatively high, it is necessary to demonstrate that the residue can be readily removed from the container, recommending MT 148.1 as the preferred evaluation method.

In 2024, CIPAC revised and merged MT 148 and MT 148.1 into a single method, MT 148.2. Currently, MT 148.2 has been accepted as the official method, replacing both MT 148 and MT 148.1, with results from MT 148.2 being equivalent to those obtained using MT 148 and MT 148.1. Compared with MT 148.1, the pre‑published version of MT 148.2 introduces an additional procedure for evaluating residues after washing: if the residue remaining in the graduated cylinder after decanting exceeds 5%, further analysis of the washed residue is required. The washing step may be repeated up to three times, with residual amounts determined after each wash. Recognizing that the standing time prior to decanting has only a minor impact on the determination of pourability, MT 148.2 reduces this standing period from the original 24 hours to 30 minutes, making the revised method more aligned with the actual field use of samples. Furthermore, MT 148.2 explicitly specifies that the volume of sample added to the graduated cylinder should correspond to the nominal capacity of 500 mL—approximately 80% of the cylinder’s total volume—thus reflecting the real‑world conditions of sample filling in commercial packaging.

2.3.4 Dust

In 2013, China revised and adopted MT 171 to establish the national standard “Method for Determining Dust in Granular Pesticides” (GB/T 30360-2013). For practical reasons, GB/T 30360-2013 only incorporated the arbitration gravimetric method from MT 171, without referencing the optical method. In 2019, CIPAC published an updated version of the method, MT 171.1. Regarding instrumentation, MT 171.1 introduces more specific requirements for the materials used in the test apparatus: the equipment employed in gravimetric measurements must be constructed from corrosion‑resistant metal plates; if plastic materials are used, they must be free of electrostatic effects to prevent interference with the determination of dust mass. Furthermore, compared with MT 171.1, GB/T 30360-2013 replaced the sintered glass filter positioned upstream of the 75 μm stainless steel mesh in the apparatus with degreased cotton. In terms of experimental procedures, MT 171.1 refined the sample weighing range, revising the original specification of 30 g to 30 ± 0.5 g, thereby enhancing the flexibility and reproducibility of the analytical process. With respect to result reporting, MT 171.1 adjusted the critical thresholds for interpreting the results (Table 3).

Table 3 Comparison of Results Determination for Dust Measurement by Gravimetric Method

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Summary

In summary, this paper, after systematically reviewing the current status of the development and revision of national standards for analytical methods used in pesticide product quality control, further examines the differences between selected standards and the latest CIPAC methods in terms of technical content and applicability. It identifies key gaps in the existing standard system that require refinement and updating. Overall, the current national standards for analytical methods in pesticide quality control cover a broad range of applications and generally meet the quality‑control needs of mainstream products, including solid formulations, liquid formulations, and seed‑treatment preparations. Moving forward, the standard‑setting process should remain closely aligned with advances in industry technology and evolving product trends, guided by actual quality‑control requirements. Efforts should focus on filling the existing gaps where no analytical methods yet exist for certain formulation‑specific quality‑control parameters, with particular attention to research and standardization of quality‑control parameters and testing methods for emerging product categories such as nano‑pesticides. By advancing the updating and improvement of relevant standards, we can further enhance the scientific rigor, practical applicability, and forward‑looking orientation of China’s pesticide standards system.

Source: Pesticide Science and Management, Issue 9, 2025