technical alphacypermethrin - who | world … with related manufacturing impurities and shall be in...

ALPHACYPERMETHRIN WHO/SIT/32TECHNICAL

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TECHNICAL ALPHACYPERMETHRINFull specification: WHO/SIT/32

Adopted 10 December 1999

1. Specification

1.1 Description

The material shall consist of a homogeneous mixture of technical alphacypermethrintogether with related manufacturing impurities and shall be in the form of a white tocream crystalline powder, free from visible extraneous matter and added modifyingagents.

1.2 Chemical and physical requirements

The material sampled from any part of the consignment (see method WHO/M/1.R1),shall comply with the requirements of section 1.1 and with the followingrequirements.

1.2.1 Identity test

Where the identity of the active ingredient is in doubt, then it shall comply with at leastone additional test. (CIPAC method 454/TC/(M)/2, CIPAC Handbook H, p.15).

1.2.2 Alphacypermethrin cis 2 ([IR cis] S and [IS cis] R isomers) content (g/kgbasis)

The alphacypermethrin cis 2 ([IR cis] S and [IS cis] R isomers) content shall bedeclared (not less than 910 g/kg), and when determined by the method described insection 2.1 the mean measured content obtained shall not be lower than the declaredcontent.

1.2.3 Total pyrethroid content

The combined content of the cis and trans isomers of alpha-cyano-3-phenoxybenzyl-2,2-dimethyl-3-(2,2-dichlorovinyl-)cyclopropanecarboxylate, when determined by themethod described in section 2.2, shall not be less than 975 g/kg.

.1.2.4 Volatile hydrocarbon solvent content

The maximum volatile hydrocarbon solvent content of the material, when determinedby the method described in section 2.3 shall not be higher than 1g/kg.


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1.2.5 Triethylamine content

The maximum triethylamine content of the material, when determined by the methoddescribed in section 2.4 shall not be higher than 1 g/kg.

1.3 Packing and marking of packages

The technical alphacypermethrin shall be packed in suitable clean containers, asspecified in the order:

All packages shall bear, durably and legibly marked on the container, the following:

Manufacturer’s nameTechnical alphacypermethrinBatch or reference number, and date of testNet weight of contentsDate of manufacture

and the following cautionary notice:

Alphacypermethrin is a pyrethroid that acts predominantly on the central nervous system; high dosageshave been found to cause tonic seizures in experimental animals. A high concentration in air may be anirritant and contact with the concentrated product may induce a temporary tingling sensation, particularlyon the face. It may be hazardous if swallowed. Do not inhale spray mist. Avoid skin contact; wearprotective gloves, clean protective clothing, and a face mask (surgical type) when handling the product.Wash hands and exposed skin thoroughly after using.

Keep containers out of reach of children and well away from foodstuffs and animal feed and theircontainers.

Alphacypermethrin is toxic to aquatic wildlife. Avoid accidental contamination of water.

If poisoning occurs, call a physician. Treatment is symptomatic.

2. Methods of determining chemical and physical properties

2.1 Alphacypermethrin content

2.1.1 Outline of method

The sample is dissolved in tetrahydrofuran with di-octyl phthalate used as the internalstandard. Separation is carried out in the split injection mode using a dimethylpolysiloxane WCOT fused silica capillary column with automatic injection and flameionisation detector. The alphacypermethrin is determined by comparison withcalibration solutions.

2.1.2 Apparatus

Gas chromatograph. Capable of operating over the range 100 to 300°C with a flameionisation detector, split/splitless injector and autosampler.


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Column. 30 m WCOT fused silica 0.25 mm id and 0.25 µm film thickness coatedwith dimethyl polysiloxane (chemically bonded), or equivalent.

Injector system. Injector split/splitless with fused silica liner containing a 1 cm plugof glass wool. An automatic injector is strongly recommended to ensure the bestanalytical results.

It is important to ensure that the split liner is acid treated, thoroughly deactivated andconditioned before use, to ensure that alphacypermethrin does not epimerise duringanalysis.

Split ratio 75-100:1 (split vent at 75 mL/min) Injection Volume 1.0 µL using a autosampler

Detector system. Type FID, with no special requirements.

Automatic digital integrator or chromatography data system. Compatible with thegas chromatograph.

100 mL volumetric flasks.

2.1.3 Reagents

Tetrahydrofuran, analytical grade.

Citric acid. 5% citric acid solution.Dissolve citric acid (25 g) in water (500 mL).

Di-octyl phthalate, di-(2-ethylhexyl)phthalate, Internal standard. Select for use a batchwhich, when chromatographed under the conditions below for thedetermination of alphacypermethrin gives no peak with a similar retentiontime to the alphacypermethrin isomers.

Cypermethrin analytical standard of known purity (containing a mixture of trans 3,trans 4, cis 1 and cis 2 cypermethrin).

Alphacypermethrin working standard, of known alphacypermethrin content .

2.1.4 Preparation of standard solutions

Internal standard solution

Dissolve di-octyl phthalate (5.0 g) in tetrahydrofuran (500 mL) (solution I). Ensuresufficient quantity of this solution is prepared for all samples and calibration standardsbeing analysed. The same internal standard solution must be used for standards andsamples in the same analytical run.

Citric acid. 5% citric acid solution.


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Dissolve citric acid (25 g) in water (500 mL).

Alphacypermethrin calibration solution

Weigh in duplicate (to the nearest 0.1 mg) about 0.1 g of alphacypermethrin (CA andCB, g) into 100 mL volumetric flasks. Add to each, 70 mL of tetrahydrofuran andagitate the flask gently to dissolve. Add by pipette 10.0 mL of internal standardsolution (solution I) and 10 mL of 5% citric acid solution from a measuring cylinder.Make to volume with tetrahydrofuran and mix well. (Solutions CA and CB).

Note: Citric acid is added to stop epimerisation of alphacypermethrin in solution.

Prepare a solution without internal standard, by dissolving about 0.1 g ofalphacypermethrin standard into a 100 mL volumetric flask. Add approximately 70mL of tetrahydrofuran and swirl to dissolve. Add by pipette 10 mL of 5% citric acidsolution from a measuring cylinder. Make to volume with tetrahydrofuran and mixwell. (Solution CO).

Cypermethrin calibration check solution

Prepare a solution of cypermethrin, by dissolving about 0.1 g of cypermethrinstandard into a 100 mL volumetric flask. Add approximately 70 mL oftetrahydrofuran and swirl to dissolve. Add by pipette 10mL of the internal standardsolution to volume with tetrahydrofuran and mix well (Solution CC).

2.1.5 Operating conditions

The conditions given below are typical values and may have to be adjusted to obtainoptimum results from a given apparatus.

Temperatures

Column oven 230°CInjector 260°CDetector 300°C

Adjust the column oven temperature if required to obtain retention time windows fordi-octyl (approximately 13.5 minutes), alphacypermethrin cis 2 isomer(approximately 27.0 minutes) and alphacypermethrin cis 1 isomer (approximately25.2 minutes). The trans 3 and trans 4 isomers elute at approximately 26.1 and 27.5minutes respectively.

Gas flow rates

Helium carrier approximately 0.8 mL min-1

Helium make up gas 60 mL min-1 or optimum for instrument


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Septum purge 2 mL min-1

Hydrogen as recommended for the instrumentAir as recommended for the instrument

All gases should be purified through molecular sieves. The carrier gas should befurther purified through an oxygen trap.

2.1.6 Sample preparation

Sampling

Homogenize the bulk material before taking the sample. Take at least 25 g. Re-homogenize the bulk before taking a sub-sample for analysis.

Preparation of the sample solutions.

Weigh in duplicate (to the nearest 0.1 mg) into 100 mL volumetric flasks sufficientsample (w, g) to contain 0.1 g of alphacypermethrin. Add approximately 70 mL oftetrahydrofuran and agitate the flask gently to dissolve.

Add by pipette to each flask 10 mL of di-octyl phthalate solution I and by measuringcylinder, 10 mL of 5% citric acid solution. Make to volume with tetrahydrofuran andmix well (Solutions SA and SB).

Prepare a solution without internal standard, by dissolving about 0.1 g ofalphacypermethrin standard into a 100 mL volumetric flask. Add approximately 70mL of tetrahydrofuran and swirl to dissolve. Add by pipette 10 mL of 5% citric acidsolution from a measuring cylinder. Make to volume with tetrahydrofuran and mixwell. (Solution SO).

2.1.7 Equilibration of the system.

Carry out alternate 1.0 µL injections of solutions I, Co and So and check whether thereare any interfering peaks from impurities. If there are make any necessary correctionsbut do not use external calibration.

Inject calibration solutions CA and CB to equilibrate the system and use the data fromthese chromatograms to set the integration parameters. Calculate the response factorsfor these injections to check the stability of the instrument. Response factors shouldnot differ by more than ± 1% of the mean.

Inject the solution of cypermethrin in tetrahydrofuran to ensure complete separationof the alphacypermethrin isomers.

2.1.8 Analysis of sample


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Carry out 1.0 µL injections of calibration solutions CA and CB and sample solutionsSA and SB in the following sequence and record the integrated areas of the peaks.

Injection sequence CA1, SA1, SA2, CB1, CA2, SB1, SB2, CB2.

2.1.9. Calculation

Calculate the relative response factors (f1, f2 etc) for the pair of calibration injectionswhich bracket the sample injections eg use CA1 and CB1 for sample injections SA1, SA2etc and obtain the mean response factor, f. Sample analysis should be repeated ifcalibration response factors f1 and f2 differ by more than ± 2% of the mean f.

Relative response factor = HsIr x s x P

Where:Hs = area of alphacypermethrin cis 2 peak in the calibration solution.Ir = area of di-octyl phthalate peak in the calibration solution.s = mass of alphacypermethrin analytical standard in calibration

solution (g).P = purity of the alphacypermethrin standard (g/kg).

For each sample injection eg SA1, calculate the alphacypermethrin cis 2 content.

Alphacypermethrin content = Hw f x Iq x w

Where:f = mean relative response factorHw = mean area of alphacypermethrin cis 2 peak in the sample solutionIq = area of di-octyl phthalate peak in the sample solutionw = mass of sample (g)

Calculate the alphacypermethrin cis 2 content of the sample as the mean of the fourdeterminations as follows:

Sample injection Use relative response factorfrom

Alphacypermethrin cis 2(g/kg)

SA1 CA1 and CB1 Q )) X

SA2 CA1 and CB1 R )

SB1 CA2 and CB2 S ) ) Y

SB2 CA2 and CB2 T )


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Q and R, S and T should agree to within ± 0.5% of their mean values (X and Y). Xand Y should agree within ± 1% of their mean values.

Take the mean of the two values x and y as the alphacypermethrin content.

2.2 Total pyrethroid content


The sample is dissolved in a chloroform/heptane mixture containing 0.2%tetrahydrofuran. Separation is carried out by normal phase high performance liquidchromatography with ultra violet detection. The total pyrethroid content isdetermined by comparison with calibration solutions.

2.2.2 Apparatus

Liquid chromatograph equipped with a 10 µL loop injector. UV detector capable ofoperating at 278 nm.

Column stainless steel, 250 x 4.6 mm (i.d.) Zorbax SIL normal phase column, orequivalent.

Guard column 15 x 3.2 mm (i.d.) 7 µm silica cartridge or equivalent.

Injector system capable of reproducible 10 µL injections.

Detector system UV, with no special requirements.

Automatic digital integrator or chromatography data system compatible with theliquid chromatograph

50 mL, 100 mL volumetric flasks.

2.2.3 Reagents

Cis and trans cypermethrin Analytical standard of known purityHeptane HPLC gradeChloroform HPLC grade (containing 1% ethanol as a preservative)Tetrahydrofuran (THF) ACS reagent (contains butylated hydroxytoluene, BHT, as apreservative)Mobile phase Heptane and chloroform (9 to 1 volume ratio) with 0.2% (v/v)tetrahydrofuran. Measure heptane (2250 mL) and chloroform (250 mL) using agraduated cylinder and add by pipette THF (5 mL).


Cis and trans cypermethrin calibration solution


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Weigh in duplicate (to the nearest 0.1 mg) about 0.05 g each of cis and transcypermethrin (CC and CD, g) into 100 mL volumetric flasks. Add to each, 5 mL ofchloroform to dissolve and dilute to volume with heptane and mix well. (SolutionsCC and CD).

2.2.5 Operating Conditions


Eluting solvent flow rate 2 mL/minTemperature 35°CInjection volume 10 µLWavelength 278 nmRetention times Cis 1 cypermethrin 15-18 minutes

Cis 2 cypermethrin 16-20 minutesTrans 3 cypermethrin 17-25 minutesTrans 4 cypermethrin 22-27 minutes

2.2.6 Sample preparation

Sampling

Homogenise the bulk material before taking the sample. Take at least 25 g. Re-homogenise the bulk before taking a sub-sample for analysis.


Weigh in duplicate (to the nearest 0.1 mg) into 50 mL volumetric flasks sufficientsample (w, g) to contain 0.1 g of technical grade cypermethrin. Add approximately 5mL of chloroform to dissolve the sample and dilute with heptane. (Solutions SC andSD).

2.2.7 Equilibration of the system

Inject calibration solutions CC and CD to equilibrate the system and use the data fromthese chromatograms to set the integration parameters. Calculate the response factorsfor these injections to check the stability of the instrument. Response factors shouldnot differ by more than ± 1% of the mean.


Carry out 10 µL injections of calibration solutions CC and CD and sample solutions SCand SD in the following sequence and record the integrated areas of the peaks.

Injection sequence CC1, SC1, SC2, CD1, CC2, SD1, SD2, CD2


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2.2.9 Calculation

Calculate the relative response factors (f1, f2 etc.) for the pair of calibration injectionswhich bracket the sample injections e.g. use CC1 and CD1 for sample injections SC1,SC2 etc. and obtain the mean response factor, f. Sample analysis should be repeated ifcalibration response factors f3 and f4 differ by more than ± 2% of the mean f.

HsRelative response factor f =

s x P

Where:Hs = area of the four cypermethrin peaks in the calibration solutions = mass of the cypermethrin analytical standard in calibration

solution (g)P = purity of the cypermethrin standard (g/kg)

For each sample injection eg SC1, calculate the cypermethrin isomer content

HwCypermethrin isomer content=

f x w

Where:f = mean relative response factorHw = mean area of the four cypermethrin isomer peaks in the sample

solutionw = mass of sample (g)

2.3 Volatile hydrocarbon solvent content


The volatile hydrocarbon solvent content is determined by measuring the difference inthe weight of the sample before and after drying in a vacuum oven.

2.3.2 Apparatus

Vacuum oven capable of maintaining a temperature of 35-45°C with a vacuum ofabout 2430" Hg.

Desiccator: Note it is recommended to allow the sample to reach room temperaturein a desiccator, after removal from the drying oven, to minimise adsorption ofatmospheric moisture.

Petri Dishes Pyrex, 100 x 15 mm


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2.3.3 Reagents

Desiccant e.g. Indicating Drierite Absorbent, or equivalent.

2.3.4 Procedure

In duplicate, accurately weigh Petri dishes (x g). Accurately weigh 5-10 g of thetechnical material into the Petri dish. (y g). Place the sample in the oven set at atemperature of about 40°C and adjust the vacuum to about 2430" Hg. Dry the samplefor about 2.5 hours. Remove the sample from the oven and allow it cool in thedesiccator and reweigh (z g). Dry the sample for an additional 30 minutes and re-determine the weight. If the weight is constant, i.e., the relative change between twoweighings is less than 0.5%, calculate the percentage volatile hydrocarbon content.Otherwise, continue drying the sample to constant weight.

100 (y-z)Percentage ( w/w ) volatile hydrocarbon content =

y-x

2.4 Triethylamine content


This method is used to determine the content of triethylamine ( TEA ) inalphacypermethrin technical material. The sample is dissolved in a mixture of glacialacetic acid and chlorobenzene and potentiometrically titrated with standard acetousperchloric acid. The amount of TEA is calculated from the equivalence point of thetitration curve.

2.4.2 Apparatus

Potentiometric Titrator e.g. Mettler DL25 titrator equipped with a combination glasselectrode ( Mettler DG 112), or equivalent. An Epson FX-85 or other printer to recordthe results.

Titrator cups 100 mL to fit the titrator.

5 mL, 100 mL Volumetric pipettes (Class A)

1L and 100 mL Volumetric flasks (Class A)

2.4.3 Reagents

Acetous perchloric acid. 1 M solution of standard perchloric acid in glacial aceticacidGlacial acetic acid. Reagent gradePotassium hydrogen phthalate A.C.S. Primary standard (99.95-100.05%)Chlorobenzene HPLC Grade


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Acetous perchloric acid 0.01 M. Pipette 100 mL of the 0.1M acetous perchloric acidinto a 1L volumetric flask. Dilute to mark with glacial acetic acid.Solution Accurately weigh 204 mg of potassium hydrogen phthalate into a 100 mLvolumetric flask. Record the weight to the nearest 0.01 mg. Dissolve in glacial aceticacid.

2.4.4 Procedure

Blank determination (Repeat in triplicate)

Add 10mL of chlorobenzene to a titrator and fill to 100 mL with glacial acetic acid.Determine the equivalence point and record the volume at this point. Average therecorded volumes together and use this as the blank value.

Standardization of 0.01M Perchloric (Repeat in triplicate)

Pipette 5 mL of the potassium hydrogen phthalate solution into a titrator cup. Add 10mL of chlorobenzene and fill to 100 mL with glacial acetic acid. Attach vessel totitrator, and determine the equivalence point and record the volume at this point.Determine the concentration of the perchloric solution using the calculation found insection 2.4.7. Average the results.

Analysis of samples

All weighings should be accurate to within 0.1 mg.

Accurately weigh 3 to 4 g of technical material into the titrator vessel. Record theweight to the nearest 0.1 mg. Add 10 mL of chlorobenzene and fill to 100 mL withglacial acetic acid. Attach the vessel to titrator, and turn on stirrer to dissolve sample.Determine the equivalence point and record the volume at this point.

2.4.5 Calculation

The concentration of the potassium hydrogen phthalate standard solution is calculatedby the following equation:

m1C1 =

204.22 x V1where:

C1 = concentration of potassium hydrogen phthalate (mmoles/mL)m1 = mass of potassium hydrogen phthalate (mg)V1 = volume of potassium hydrogen phthalate solution (mL)


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The concentration of the perchloric solution is determined with the followingequation:

C1V1C2 =

V3 - V4

where:

C2 = concentration of standard perchloric solution (mmoles/mL)C1 = concentration of potassium hydrogen phthalate solution

(mmoles/mL)V2 = volume of standard potassium hydrogen phthalate solution (mL)V3 = volume of perchloric to reach equivalence point (mL)V4 = volume average blank value (mL)

The weight percent of triethylamine is determined with the following equation:

(V5-V4) x C2 x 101.2 x 100weight % triethylamine =

m2where:

V5 = volume of perchloric used to reach equivalence point (mL)V4 = volume of average blank value (mL)C2 = concentration of perchloric solution (mmol/mL)m2 = mass of alphacypermethrin in sample (mg)

ALPHACYPERMETHRIN WHO/SIF/61AQUEOUS SUSPENSION CONCENTRATE

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ALPHACYPERMETHRINAQUEOUS SUSPENSION CONCENTRATE

Full specification: WHO/SIF/61Adopted 10 December 1999

1. Specification

1.1 Description

The material consists of a suspension of fine particles of technical alphacypermethrin,complying with the requirements of the WHO specification WHO/SIT/32, in anaqueous phase together with suitable formulants; After gentle agitation the materialshall be homogeneous and suitable for further dilution in water.

1.2 Chemical and physical requirements

The material sampled from any part of the consignment (see method WHO/M/1.R1),shall comply with the requirements of section 1.1 and with the followingrequirements.

1.2.1 Alphacypermethrin cis 2 ([IR cis] S and [IS cis] R isomers) content (g/kgbasis)

The content of alphacypermethrin cis 2 ([IR cis] S and [IS cis] R isomers) content(g/kg basis), determined by the method described in section 2.1 shall not differ fromthe declared content by more than the following amount:

Declared content Tolerance permitted

Up to 25 g/kg ± 15% of the declared contentAbove 25 up to 100g/kg

± 10% of the declared content

Higher declared contents are not currently available.The average content of all samples taken shall not be lower than the declared content.

1.2.2 Alphacypermethrin cis 1 ([IR cis] R and [IS cis] S isomer) content

The alphacypermethrin cis 1:cis 2 isomer ratio determined by the method described insection 2.1.10, shall not be higher than 5:95.

1.2.3 pH range

The pH of the concentrate, determined by the CIPAC method MT 75 (CIPACHandbook F, p.205), shall be between 7.0 and 8.7.


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1.2.4 Rinsability

The maximum non volatile rinsed residue as determined by CIPAC MT 148.1 (inpress)1 shall not exceed 0.05%.

1.2.5 Spontaneity of dispersion at 30°C

A minimum of 60% of the alphacypermethrin content found under 1.2.1 shall be insuspension after 5 min in WHO standard hard water C at 30 ± 2°C as determined byCIPAC method MT 160 (CIPAC Handbook F, p.391).

1.2.6 Suspensibility after heat stability treatment

In WHO standard hard water. When tested by the method described in section 2.2, aminimum of 70% of the alphacypermethrin content (0.63 g/L) shall be in suspension30 minutes after agitating a suspension containing (0.9 g/L) of alphacypermethrinprepared in standard hard water at 30 ± 2°C from the suspension concentrate subjectedto the heat stability treatment described in section 2.3.

1.2.7 Wet sieve test

Not less than 98% of the concentrate shall pass through a 75 µm sieve when tested bythe CIPAC method MT 59 (CIPAC Handbook F, p.177).

1.2.8 Persistent foam

The persistent foam at the top of a 100 mL of suspension prepared in WHO standardsoft water, shall not exceed 20 mL after 12 minutes when tested by the CIPAC methoddescribed MT 47.2 (CIPAC Handbook F, p.152)

1.2.9 Heat stability

The suspension after treatment as described in section 2.3 must comply with therequirements of sections 1.2.1, 1.2.2, 1.2.3, 1.2.4, 1.2.5, and 1.2.7 of this specification.

1.2.10 Cold stability

After storage testing at 0 ± 1°C for 7 days, according to the CIPAC method MT 39.1(CIPAC Handbook F, p.128), the product shall continue to comply with 1.2.5, 1.2.6and 1.2.7.

1.3 Packing and marking of packages

The alphacypermethrin suspension concentrate shall be packed in suitable clean drumsas specified in the order. The shall be made of high density polyethylene or anysuitable materials compatible with the product..

1 Method can be obtained on request from CIPAC secretariat, ‘t Gotink 7, 7261 VE Ruurlo,Netherlands.


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All packages shall bear, durably and legibly marked on the container, the following:

Manufacturer’s nameAlphacypermethrin suspension concentrateAlphacypermethrin.......g/lBatch or reference number, and date of testNet weight of contentsDate of manufactureInstruction for use

and the following minimum cautionary notice:

Alphacypermethrin is a pyrethroid that acts predominantly on the central nervous system; highdosages have been found to cause tonic seizures in experimental animals. A highconcentration in air may be an irritant and contact with the concentrated product may induce atemporary tingling sensation, particularly on the face. It may be hazardous if swallowed. Donot inhale spray mist. Avoid skin contact; wear protective gloves, clean protective clothing,and a face mask (surgical type) when handling the product. Wash hands and exposed skinthoroughly after using.

Keep containers out of reach of children and well away from foodstuffs and animal feed andtheir containers.

Alphacypermethrin is toxic to aquatic wildlife. Avoid accidental contamination of water.

If poisoning occurs, call a physician. Treatment is symptomatic.

2 Methods of determining chemical and physical properties

2.1 Alphacypermethrin content


The sample is extracted in tetrahydrofuran with di-octyl phthalate used as the internalstandard. Separation is carried out in the split injection mode using a dimethylpolysiloxane WCOT fused silica capillary column with automatic injection and flameionisation detector. The alphacypermethrin is determined by comparison withcalibration solutions.

2.1.2 Apparatus

Gas chromatograph. Capable of operating over the range 100 to 300°C with a flameionisation detector, split/splitless injector and autosampler.

Column. 30 m WCOT fused silica 0.25 mm id and 0.25 µm film thickness coatedwith dimethyl polysiloxane (chemically bonded), or equivalent.

Injector system. Injector Split/splitless with fused silica liner containing a 1 cm plugof glass wool. An automatic injector is strongly recommended to ensure the bestanalytical results.


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It is important to ensure that the split liner is acid treated, thoroughly deactivated andconditioned before use, to ensure that alphacypermethrin does not epimerise duringanalysis.

Split ratio 75-100:1 (split vent at 75 mL/min) Injection Volume 1.0 µL using a autosampler.

Detector system. Type FID, with no special requirements.

Automatic digital integrator or chromatography data system. Compatible with the gaschromatograph

100 mL volumetric flasks.

2.1.3 Reagents

Tetrahydrofuran.

Citric acid. 5% citric acid solution.Di-octyl phthalate, di-(2-ethylhexyl)phthalate, Internal standard. Select for use a batch

which, when chromatographed under the conditions below for thedetermination of alphacypermethrin gives no peak with a similar retention timeto the alphacypermethrin isomers.

Cypermethrin analytical standard (containing a mixture of trans 3, trans 4, cis 1 andcis 2 cypermethrin) of known purity

Alphacypermethrin working standard, of known alphacypermethrin content


Internal standard solution.

Dissolve di-octyl phthalate (5.0 g) in tetrahydrofuran (500 mL) (solution I). Ensuresufficient quantity of this solution is prepared for all samples and calibration standardsbeing analysed.

Citric acid. 5% citric acid solution.

Dissolve citric acid (25 g) in water (500 mL).

Alphacypermethrin calibration solution.

Weigh in duplicate (to the nearest 0.1 mg) about 0.1 g of alphacypermethrin (CA andCB, g) into 100 mL volumetric flasks. Add to each, 70 mL of tetrahydrofuran andagitate the flask gently to dissolve. Add by pipette 10.0 mL of internal standardsolution (solution I) and 10mL of 5% citric acid solution from a measuring cylinder.Make to volume with tetrahydrofuran and mix well. (Solutions CA and CB).

Note: Citric acid is added to stop epimerisation of alphacypermethrin in solution.


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Prepare a solution without internal standard, by dissolving about 0.1 g ofalphacypermethrin standard into a 100 mL volumetric flask. Add approximately 70mL of tetrahydrofuran and swirl to dissolve. Add by pipette 10 mL of 5% citric acidsolution from a measuring cylinder. Make to volume with tetrahydrofuran and mixwell. (Solution CO).

Cypermethrin calibration check solution

Prepare a solution of cypermethrin, by dissolving about 0.1 g of cypermethrin standardinto a 100 mL volumetric flask. Add approximately 70 mL of tetrahydrofuran andswirl to dissolve. Add by pipette 10 mL of the internal standard solution to volumewith tetrahydrofuran and mix well (Solution CC).

2.1.5 Operating conditions


Temperatures

Column oven 230°CInjector 260°CDetector 300°C

Adjust the column oven temperature if required to obtain retention time windows fordi-octyl (approximately 13.5 minutes), alphacypermethrin cis 2 isomer (approximately27.0 minutes) and alphacypermethrin cis 1 isomer (approximately 25.2 minutes). Thetrans 3 and trans 4 isomers elute at approximately 26.1 and 27.5 minutes respectively.

Gas flow rates

Helium carrier approximately 0.8mL min-1

Helium make up gas 60mL min-1 or optimum for instrumentSeptum purge 2mL min-1

Hydrogen as recommended for the instrumentAir as recommended for the instrument

All gases should be purified through molecular sieves. The carrier gas should befurther purified through an oxygen trap.

2.1.6 Sample Preparation

Sampling

Homogenize the bulk material before taking the sample. Take at least 250 g. Re-homogenize the bulk before taking a sub-sample for analysis.



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Weigh accurately in duplicate (to the nearest 0.1mg) into 100 mL volumetric flaskssufficient sample (w,g) to contain 0.1 g of alphacypermethrin. Add by measuringcylinder 10 mL of the 5% citric acid solution to each of the flasks and swirl to fullydisperse the formulation. Add approximately 70 mL of tetrahydrofuran inapproximately 10 to 15 mL portions, swirling in between each addition to fullydisperse the sample. Place in an ultrasonic bath for 15 minutes with occasionalswirling. Add by pipette 10 mL of the di-octyl phthalate, internal standard solution Iand make to volume with tetrahydrofuran and mix well. Filter through a suitable papereg GF/A or filter unit eg PTFE 0.45 µm to give clear solutions. (Solutions SA and SB).

Prepare a solution without internal standard, by dissolving sufficient sample to contain0.1 g of alphacypermethrin into a 100 mL volumetric flask. Add by measuringcylinder 10 mL of the 5% citric acid solution to each of the flasks and swirl to fullydisperse the formulation. Add approximately 70 mL of tetrahydrofuran inapproximately 10 to 15 mL portions, swirling in between each addition to fullydisperse the sample. Place in an ultrasonic bath for 15 minutes with occasionalswirling. Make to volume with tetrahydrofuran and mix well. Filter through a suitablepaper eg GF/A or filter unit eg PTFE 0.45 µm to give a clear solution. (Solution SO).

2.1.7 Equilibration of the system.

Carry out alternate 1.0 µL injections of solutions I, Co and So and check whether thereare any interfering peaks from impurities. If there are make any necessary correctionsbut do not use external calibration.

Inject calibration solutions CA and CB to equilibrate the system and use the data fromthese chromatograms to set the integration parameters. Calculate the response factorsfor these injections to check the stability of the instrument. Response factors shouldnot differ by more than ± 1% of the mean.

Inject the solution of cypermethrin in tetrahydrofuran (Cc) to ensure completeseparation of the alphacypermethrin isomers.


Carry out 1.0 µL injections of calibration solutions CA and CB and sample solutions SAand SB in the following sequence and record the integrated areas of the peaks.

Injection sequence CA1, SA1, SA2, CB1, CA2, SB1, SB2, CB2.

2.1.9 Calculation.

Calculate the relative response factors (f1, f2 etc) for the pair of calibration injectionswhich bracket the sample injections eg use CA1 and CB1 for sample injections SA1, SA2etc and obtain the mean response factor, f. Sample analysis should be repeated ifcalibration response factors f1 and f2 differ by more than ± 2% of the mean f.

HsRelative response factor =

Ir x s x P


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where:

Hs = area of alphacypermethrin cis 2 peak in the calibration solution.Ir = area of di-octyl phthalate peak in the calibration solution.s = mass of alphacypermethrin analytical standard in calibration

solution (g).P = purity of the alphacypermethrin standard (g/kg).

For each sample injection eg SA1, calculate the alphacypermethrin cis 2 content.

HwAlphacypermethrin content =

f x Iq x w

where:

f = mean relative response factorHw = mean area of alphacypermethrin cis 2 peak in the sample solutionIq = area of di-octyl phthalate peak in the sample solutionw = mass of sample (g)

Calculate the alphacypermethrin cis 2 content of the sample as the mean of the fourdeterminations as follows:

Sample injection Use relative response factorfrom

Alphacypermethrin cis 2(g/kg)

SA1 CA1 and CB1 Q )) X

SA2 CA1 and CB1 R )

SB1 CA2 and CB2 S ) ) Y

SB2 CA2 and CB2 T )

Q and R, S and T should agree to within ± 0.5% of their mean values (X and Y). Xand Y should agree within ± 1% of their mean values.

Take the mean of the two values x and y as the alphacypermethrin content.

2.1.10 Determination of the Cis 1 to Cis 2 ratio.To determine the cis 1 to cis 2 percentage ratio in a sample

Peak area cis 1 x 100cis 1 % =

Total peak area of cis 1 and cis 2


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Peak area cis 2 x 100cis 2 % =

Total peak area of cis 1 and cis 2

2.2 Suspensibility


A suspension of known concentration of alphacypermethrin in standard hard water isprepared, poured into a 250 mL graduated cylinder, maintained at constanttemperature and allowed to remain undisturbed for 30 minutes. The top 9/10ths aredrawn off and the content of alphacypermethrin in the bottom 1/10th is determined, soallowing to evaluate the active ingredient mass still in suspension after 30 minutes.

2.2.2 Apparatus

A 250 m1 graduated cylinder with a ground-glass stopper and a distance of 20.0-21.5cm between the bottom and the 250 mL calibration mark.

A glass tube, about 40 cm long and about 5 mm in internal diameter, pointed at oneend to an opening of 2-3 mm, the other end being connected to a suitable source ofsuction.

2.2.3 Reagents

WHO standard hard water. See method WHO/M/29

2.2.4 Procedure

Weigh (to the nearest 1 mg) into 100 mL beaker an amount of the sample to form 250m1 of a suspension containing 0.9 g/L of alphacypermethrin. Add a volume of waterat 30 ± 2°C equal to at least twice the mass of the sample taken. Allow to stand for 30seconds and then stir by hand for 30 seconds with a glass rod 4-6 mm in diameter, atnot more than four revolutions per second, making no deliberate attempt to break upany lumps. The immediately transfer the mixture quantitatively to the 250 mLgraduated cylinder, using water at 30 ± 2°C for rinsing, and again avoiding mechanicaldisintegration of lumps.

Immediately add sufficient water at 30 ± 2°C to bring the volume up to the 250 mLmark. Insert the stopper and invert the cylinder end over end 30 times at the rate ofone complete cycle every 2 seconds. This operation should be carried out as smoothlyas possible, keeping the axis of rotation fixed. Allow the graduated cylinder to standfor 30 minutes in a water-bath at 30 ± 2°C taking care that the bath is free fromvibrations.

Should excessive flocculation occur during the test, the material is unsatisfactory.

At the end of the 30 minutes settling period, insert the glass tube into the cylinder and,with a minimum of disturbance, withdraw nine-tenths, of the suspension (i.e. 225 mL)


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by means of the suction tube in a period of 10-15 seconds. This is achieved bymaintaining the tip of the glass tube just below the sinking surface of the suspension.Discard the suspension withdrawn.

2.2.5 Determination of alphacypermethrin in the retained one-tenth of thesuspension

Quantitatively transfer the bottom one-tenth of suspension (25 mL) from thesuspensibility test into a 100 mL volumetric flask with approximately 50 mL oftetrahydrofuran. Add 10 mL internal standard by pipette and 5 mL citric acid solutionby measuring cylinder. Dilute to volume with tetrahydrofuran. Place in an ultrasonicbath for 10 minutes. Filter through a suitable disc filter.

Determine the alphacypermethrin content of the filtered solution by gaschromatography as described in section 2.1.8 injecting duplicate 1 .0 µL aliquots ofsample and calibration solutions.

2.2.6 Calculation

Mass of alphacypermethrin (g) in the bottom one-tenth of suspension =

f2 x P x w

f1 x 2 x 103

where:f1 = mean response ratio for the calibration solutionf2 = mean response ratio for the sample solutionw = mass (g) of alphacypermethrin standard in the calibration solutionP = purity (g/kg) of alphacypermethrin standard

10 (b-a) x 100 = 111(b-a)Suspensibility % =

9 b b

where:

a = mass (g) of alphacypermethrin in bottom one-tenth of suspensionb = mass (g) of alphacypermethrin in the sample used in the suspensibility test(calculated from the mass of sample and its percentage alphacypermethrin content).

2.3 Heat stability treatment

54°C ± 2°C for 14 days (CIPAC method MT 46.1, CIPAC Handbook F, p.149), unlessother temperatures and times are requested (FAO Manual on the development and use ofFAO specifications for plant protection products, n° 149, p.33).


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After completion of the heat stability treatment, the samples should not be exposed toheat, bright sunshine , or atmospheric humidity.

If required the test should be conducted in commercial type pack.

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