Analytical Method Validation For Assay Of Azamethiphos And Stability Study Of Azamethiphos

Azamethiphos is a kind of acaricide and also is a broad spectrum organophosphorus insecticide.It has the properties of high efficiency,low toxicity and low residue.It is a contact toxicity and stomach poisonness agent,but it is low in toxicity to mammals,and is listed as the recommended organophosphate insecticide by World Health Organization.It can kill pests that are resistant to Pyrethrin pesticides,and has a significant efficacy against multiple resistant fly strains.It is widely used in public health and family control of various mites,cockroach and flies.Azamethiphos is also used as an ideal agent for the comprehensive management of sea lice in salmon farms.Azamethiphos has been received into the first volume of the National Standard for Veterinary Drugs(Chemicals medicine,Chinese traditional medicine).The analytical method for assay described in the standard is a high performance liquid chromatography,using external standard method.This method requires high performance of the instrument,and is complicated to prepare sample solutions,and takes a long time to analyze,which is not conducive to the process control in actual production.Domestic and foreign reports on the determination of Azamethiphos assay are mostly about qualitative or quantitative analysis of organophosphorus pesticide residues in agricultural products by liquid chromatography-mass spectrometry or gas chromatography-mass spectrometry.These methods have high requirements on the instrument,resulting in high analysis costs.In view of the above situation,the thesis first established a new analytical method for the assay of Azamethiphos.The new method uses Dibutyl phthalate as the internal standard,and uses a C18 column with a column length of 150 mm,with acetonitrile: water(40:60)as the mobile phase,a flow rate of 1.2 mL/min,and a wavelength of 235 nm.The method is simple in preparation of sample solutions,fast in analysis,and the solutions are stable.So it can greatly shorten the detection time.The new method was validated by evaluating its specificity,linearity,precision,accuracy,robustness and stability of solution in the thesis.The results showed that this method has good specificity,good repeatability,accurate and reliable results.The recoveries were in the ranged of 99.81%~100.08%,and the recovery RSD was 0.09%.The linearity was satisfactory with a correlation coefficient of 0.9999 at the concentration range of 0.056 mg/mL~0.104 mg/mL.The sample solution was stable in 12 h.Then,stability studies were carried out on Azamethiphos,including stress testing,accelerated testing and long term stability studies.Both of the stress testing and accelerated testing results showed that Azamethiphos was stable,and under the condition of high relative humidity(93%),the hygroscopic rate of the sample was only 0.2% during the investigation period.The results of long term stability studies on three batches of Azamethiphos showed that there were no significant changes in appearance,moisture and melting point during 24 months stored at a temperature of 25 °C±2 °C and a relative humidity of 60%±10%.The content was slowly falling,with a decline range of 0.4%~0.6%.