Determination Method of Moisture Content in Pesticides

Determination Method of Moisture Content in Pesticides

Pesticides refer to mixtures and preparations composed of one or several chemically synthesized substances, biological sources or other natural substances, which are used to prevent and control diseases, insects, weeds, rodents and other harmful organisms endangering agriculture and forestry, as well as to purposefully regulate the growth of plants and insects.

As defined in the Regulations on Pesticide Administration, pesticides include not only traditional insecticides, fungicides and herbicides, but also non-lethal products such as plant growth regulators. The modern pesticide concept has shifted from the early focus on eliminating pests to emphasizing regulation and ecological environmental harmony.

Experimental Purpose

This experiment aims to learn the determination method of moisture content in pesticides, master its influence on product quality, stability and efficacy, and ensure pesticides comply with national standards through scientific testing.

Guarantee product quality: Excessively high moisture content will cause caking, decomposition or stratification of pesticides, and affect the stability and efficacy of active ingredients.

Optimize production processes: Guide enterprises to adjust drying, formula and packaging processes via test data to improve product uniformity.

Avoid storage deterioration: High moisture easily leads to mildew, hydrolysis and package corrosion, shortening shelf life. Testing effectively avoids such storage risks.

Distinguish formulation standards: Different formulations such as emulsifiable concentrates and wettable powders have different moisture limit requirements. This test accurately judges product qualification.

Test Samples and Instruments

Test Sample: Pesticide

Test Instrument: STNY-102 Automatic Pesticide Moisture Tester, compliant with GB/T 1600

Test Procedures

1. Reagent Calibration

Add an appropriate amount of anhydrous methanol into the titration cell, start the tester and titrate to the end point with Karl Fischer reagent to remove trace moisture in methanol.

Accurately inject 10μL pure water (about 0.0100g) into the titration cell with a dry syringe, record the consumed volume (V_1) of Karl Fischer reagent. Repeat calibration for 3 times and calculate the average titer T (mg/mL), formula: (T = m_1/V_1) ((m_1) stands for pure water mass).

2.Sample Determination

Solid sample: Accurately weigh 0.5-5g sample (adjust weight according to moisture content to ensure reagent consumption within 1-10mL), quickly add into the titration cell, stir to dissolve and titrate to the end point, record the consumed reagent volume (V_2).

Liquid sample: Draw proper amount of sample with dry syringe, inject into the titration cell and perform titration following the same steps above, record (V_2).

Blank test: Use the same volume of anhydrous methanol to replace the sample for blank titration, record the consumed reagent volume (V_0).

Test Result

The average moisture content of emulsifiable concentrate samples is 0.81%, which meets the requirements specified in GB/T 1600.