Aminocyclopyrachlor Summary of Analytical Chemistry and Residue Data DP#: D387442

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Executive Summary

Aminocyclopyrachlor [6-amino-5-chloro-2-cyclopropyl-4-pyrimidinecarboxylic acid] is a new 

herbicide belonging to the pyrimidine carboxylic acid chemical class. The mode of action is 

dysregulation of gene products involved in auxin receptor activity, which interferes with normal 

shoot and root development to stop the growth of weeds. Aminocyclopyrachlor is currently 

registered for non-crop use for general control of broadleaf weeds and woody species on private, 

public, and military lands. Three forms of aminocyclopyrachlor are currently registered: the 

parent acid aminocyclopyrachlor (DPX-MAT28; PC code 288008), the potassium salt (PC Code 

288010), and the methyl ester (DPX-KJM44; aminocyclopyrachlor-methyl; PC code 288009). 

This petition (PP#0F7817) is the first food/feed use request for aminocyclopyrachlor.

Under PP#0F7817, DuPont Crop Protection has requested the establishment of tolerances for the 

herbicide aminocyclopyrachlor, to be determined by measuring only the sum of 

aminocyclopyrachlor and aminocyclopyrachlor methyl ester, methyl 6-amino-5-chloro-2-

cyclopropyl-4-pyrimidinecarboxylate, calculated as the stoichiometric equivalent of 

aminocyclopyrachlor in/on the following commodities:

Cattle, fat..................................................................0.07 ppm

Cattle, liver...............................................................0.06 ppm

Cattle, meat ..............................................................0.02 ppm

Cattle, meat byproducts, except liver.......................0.4 ppm

Goat, fat....................................................................0.07 ppm

Goat, liver ................................................................0.06 ppm

Goat, meat................................................................0.02 ppm

Goat, meat byproducts, except liver ........................0.4 ppm

Grass, forage...............................................65 ppm

Grass, hay.................................................125 ppm

Horse, fat..................................................................0.07 ppm

Horse, liver...............................................................0.06 ppm

Horse, meat ..............................................................0.02 ppm

Horse, meat byproducts, except liver..........................0.4 ppm

Milk..........................................................................0.03 ppm

Sheep, fat..................................................................0.07 ppm

Sheep, liver ..............................................................0.06 ppm

Sheep, meat..............................................................0.02 ppm

Sheep, meat byproducts, except liver..................0.4 ppm

In conjunction with the proposed tolerances, DuPont has submitted a request for amended 

registration of the 50% dry flowable (i.e., water dispersible granule; WG) formulation of 

aminocyclopyrachlor (EPA Reg. No. 352-787), the 2 lb a.i./gal soluble liquid (SL) formulation 

of the potassium salt (K salt; EPA Reg. No. 352-786, equivalent to 2 lb ae/gal 

aminocyclopyrachlor), and the 80% WG formulation of aminocyclopyrachlor-methyl (EPA Reg. 

No. 352-785, equivalent to 75% ae aminocyclopyrachlor) for use on pasture and rangeland 

grasses. Aminocyclopyrachlor is proposed for up to two foliar applications to pasture and 
Aminocyclopyrachlor Summary of Analytical Chemistry and Residue Data DP#: D387442

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rangeland grasses at 0.038-0.172 lb ai/A/application for a maximum seasonal rate of 0.281 lb 

ai/A, with a 0-day preharvest interval (PHI) for grass forage and hay. 

The nature of the residue in grasses is adequately based on an acceptable grass metabolism study 

reflecting application of aminocyclopyrachlor-methyl. Aminocyclopyrachlor and 

aminocyclopyrachlor-methyl were the major identified residues in grass. The data indicate that 

aminocyclopyrachlor-methyl is rapidly metabolized (demethylated) in grass to form the free acid 

aminocyclopyrachlor, which is subsequently decarboxylated to form the metabolite IN-LXT69. 

Photo-induced simultaneous elimination of hydrogen chloride and pyrimidine ring contraction 

(occurring as a minor pathway) yields the imidazole-nitrile metabolite, IN-QGC48, which 

undergoes demethylation to form IN-QFH57; IN-QFH57 may also be formed through photolysis 

of aminocyclopyrachlor. An additional minor pathway involves pyrimidine ring opening 

proceeding through the postulated intermediate IN-YY905, with subsequent oxidations to form 

the amide and carboxylic acid compounds, IN-Q3007 and IN-V0977, respectively. HED has 

concluded that the residues of concern for tolerance enforcement and risk assessment in grass are 

aminocyclopyrachlor and aminocyclopyrachlor-methyl. Additional metabolism studies may be 

needed to support future uses on additional crops.

The nature of the residue in ruminants is adequately understood based on an acceptable goat 

metabolism study reflecting dosing with aminocyclopyrachlor-methyl. Aminocyclopyrachlor

was the only identified residue in goat milk and tissues. The data indicate that 

aminocyclopyrachlor-methyl is rapidly metabolized in the goat and is eliminated as 

aminocyclopyrachlor primarily in the excreta. HED has concluded that the residues of concern 

for tolerance enforcement and risk assessment in livestock are aminocyclopyrachlor and 

aminocyclopyrachlor-methyl. Because grass is not a significant feed stuff for poultry, a hen 

metabolism study is not required at this time; however, a hen metabolism study may be needed 

to support future uses on additional crops.

The petitioner has proposed high performance liquid chromatography methods with tandem mass 

spectrometry detection (HPLC/MS/MS) for enforcement of tolerances for aminocyclopyrachlor 

on grass commodities, DuPont-22582 SU1 RV2, and livestock commodities, DuPont-27162, 

Revision No. 1. The methods adequately determine residues of aminocyclopyrachlor and 

aminocyclopyrachlor-methyl as well as the metabolites IN-LXT69 and INQFH57 and INQGC48 (grass commodities only), in/on grass forage and hay, milk, eggs, and bovine tissues. 

The validated limit of quantitation (LOQ) is 0.01 ppm for each analyte. HED has concluded that 

the plant and livestock method are adequate for enforcement purposes.HED has determined that 

laboratory tolerance method validation (TMVs) are not needed for the proposed enforcement 

methods for plant and livestock commodities. The proposed enforcement methods or earlier 

versions of the methods were used for data collection in the submitted storage stability, cattle 

feeding, and grass crop field trial studies. 

Acceptable multiresidue methods test data have been submitted for aminocyclopyrachlor and 

aminocyclopyrachlor-methyl. The data indicate that multiresidue methods may be appropriate 

for determination of aminocyclopyrachlor-methyl but are not suitable for determination of 

aminocyclopyrachlor or for determination of the two analytes together. The submitted data will 

be forwarded to the U.S. Food and Drug Administration (FDA) for further evaluation.
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Adequate storage stability data have been submitted for residues of aminocyclopyrachlor, 

aminocyclopyrachlor-methyl and metabolite IN-LXT69 in grass and livestock commodities and 

for metabolites INQFH57 and IN-QGC48 in grass commodities. No additional storage stability 

data are required to support the submitted grass crop field trial study or the cattle feeding study.

An acceptable cattle feeding study has been submitted reflecting dosing of lactating dairy cows 

with aminocyclopyrachlor-methyl at 73.3, 160, 455, and 1595 ppm in the diet. Samples of milk, 

skim milk, cream, and tissues were analyzed for residues of aminocyclopyrachlor, 

aminocyclopyrachlor-methyl, and metabolite IN-LXT69. The data indicate that tolerances are 

needed for milk and ruminant commodities. The data will support the following tolerances for 

combined residues of aminocyclopyrachlor and aminocyclopyrachlor-methyl (expressed in 

parent equivalents): of 0.02 ppm for milk, and 0.30 ppm for the meat byproducts, 0.05 ppm for 

the fat, and 0.02 ppm for the muscle of cattle, goat, horse, and sheep.

Adequate field trial data have been submitted reflecting application of products containing 

aminocyclopyrachlor-methyl and aminocyclopyrachlor to grasses. Samples of grass forage and 

hay were analyzed for residues of aminocyclopyrachlor, aminocyclopyrachlor-methyl, and 

metabolites IN-LXT69, INQFH57, and IN-QGC48. The data indicate that the proposed

tolerances are too low. Based on these data and the OECD tolerance calculator, HED concludes 

that the following tolerances for combined residues of aminocyclopyrachlor and 

aminocyclopyrachlor-methyl (expressed in parent equivalents) are appropriate: 80 ppm for grass 

forage and 200 ppm for grass hay. 

An adequate confined rotational crop study has been submitted. The data indicate that the 

metabolism of aminocyclopyrachlor in rotated crops is similar to that in primary crops. HED has 

concluded that the residues of concern for the tolerance expression in rotational crops are

aminocyclopyrachlor and aminocyclopyrachlor-methyl. Aminocyclopyrachlor, 

aminocyclopyrachlor-methyl, and IN-LXT69 were identified in rotational crop commodities. 

Because residues of aminocyclopyrachlor accumulated above 0.01 ppm in turnip tops and corn 

forage, stover, and grain at a 300-day plantback interval (PBI), limited field rotational crop data 

are now required to support the proposed use on grasses. Pending submission of the required 

limited field rotational crop trials, the labels must be revised to prohibit rotation to any crop other 

than grasses following application of aminocyclopyrachlor or aminocyclopyrachlor-methyl. 

There are no established or proposed Codex or Canadian maximum residue limits (MRLs) for 

aminocyclopyrachlor in or on any food or feed crops; therefore, there are no harmonization 

issues. 

Regulatory Recommendations and Residue Chemistry Deficiencies
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HED has examined the residue chemistry database for aminocyclopyrachlor. Pending 

submission of a revised Section B and a revised Section F (see requirements below), there are no 

residue chemistry issues that would preclude granting conditional registration for the requested 

uses of aminocyclopyrachlor on pasture and rangeland grasses or establishment of tolerances for 

residues of aminocyclopyrachlor in/on the following commodities as follow:

Tolerances are established for residues of the herbicide aminocyclopyrachlor, including its 

metabolites and degradates, in or on the commodities in the table below. Compliance with the 

tolerance levels specified below is to be determined by measuring only the sum of 

aminocyclopyrachlor, 6-amino-5-chloro-2-cyclopropyl-4-pyrimidinecarboxylic acid, and 

aminocyclopyrachlor methyl ester, methyl 6-amino-5-chloro-2-cyclopropyl-4-

pyrimidinecarboxylate, calculated as the stoichiometric equivalent of aminocyclopyrachlor.

Cattle, fat..................................................................0.05 ppm

Cattle, meat byproducts ...........................................0.30 ppm

Cattle, meat ..............................................................0.02 ppm

Goat, fat....................................................................0.05 ppm

Goat, meat byproducts.............................................0.30 ppm

Goat, meat................................................................0.02 ppm

Grass, forage ...............................................................80 ppm

Grass, hay..................................................200 ppm

Horse, fat..................................................................0.05 ppm

Horse, meat byproducts ...........................................0.30 ppm

Horse, meat ..............................................................0.02 ppm

Milk..........................................................................0.02 ppm

Sheep, fat..................................................................0.05 ppm

Sheep, meat byproducts...........................................0.30 ppm

Sheep, meat..............................................................0.02 ppm

A human health risk assessment is forthcoming.

860.1200 Directions for Use

Pending submission and review of the required limited field rotational crop trials, the 

labels must be revised to prohibit rotation to any crop other than grasses following 

application of aminocyclopyrachlor or aminocyclopyrachlor-methyl.

860.1550 Proposed Tolerances

The proposed tolerances for grass forage and hay must be increased to 80 and 200 ppm, 

respectively.

The proposed tolerance for milk must be reduced to 0.02 ppm.

The proposed tolerances for liver and the meat byproducts, except liver, for cattle, horse, 

goat, and sheep must be replaced with the recommended tolerances for meat byproducts, 

as specified in Table 9. 
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860.1650 Submittal of Analytical Reference Standards

An analytical reference standard for aminocyclopyrachlor-methyl must be supplied and 

supplies replenished as requested by the Repository. 

HED recommends that conversion to unconditional registration for the requested uses may 

be considered when the following minor deficiencies have been resolved.

860.1900 Field Accumulation in Rotational Crops

A limited field accumulation in rotational crops study needs to be submitted.

Background

The chemical structure and nomenclature of aminocyclopyrachlor, aminocyclopyrachlor-methyl, 

and the potassium salt are summarized in Tables 1.1-1.3, and the physicochemical properties of 

aminocyclopyrachlor and its methyl ester are summarized in Table 2. The chemical names and 

structures of the residues of concern are presented in Appendix I.

Table 1.1. Test Compound Nomenclature-Aminocyclopyrachlor

Chemical Structure

N

N

NH2

Cl

O

OH

Common Name Aminocyclopyrachlor (parent acid)

Company Experimental Name DPX-MAT28

IUPAC Name 6-amino-5-chloro-2-cyclopropyl-4-pyrimidinecarboxylic acid

CAS Name 6-amino-5-chloro-2-cyclopropyl-4-pyrimidinecarboxylic acid

CAS Registry Number 858956-08-8

End-use product (EP) 50% WG (DuPont MethodTM 50 SG; EPA Reg. No. 352-787)

Table 1.2 Test Compound Nomenclature-Aminocyclopyrachlor-methyl (methyl ester)

Chemical Structure

N

N

NH2

Cl

O

O

CH3

Common Name Aminocyclopyrachlor-methyl

Company experimental Name DPX-KJM44
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Table 1.2 Test Compound Nomenclature-Aminocyclopyrachlor-methyl (methyl ester)

IUPAC Name methyl 6-amino-5-chloro-2-cyclopropylpyrimidine-4-carboxylate

CAS Name methyl 6-amino-5-chloro-2-cyclopropyl-4-pyrimidinecarboxylate

CAS Registry Number 858954-83-3

End-use product (EP) 80% WG (DuPont DPX-KJM44 80XP; EPA Reg. No. 352-785; equivalent to 

75% ae aminocyclopyrachlor)

Table 1.3. Test Compound Nomenclature-Aminocyclopyrachlor (potassium salt)

Chemical Structure

N

N

NH2

Cl

O

O

– K+

Empirical Formula C8H7ClKN3O2

Common Name Aminocyclopyrachlor potassium salt

Company Experimental Name DPX-MAT28 potassium salt

IUPAC Name potassium 6-amino-5-chloro-2-cyclopropylpyrimidine-4-carboxylate

CAS Name potassium 6-amino-5-chloro-2-cyclopropyl-4-pyrimidinecarboxylate

CAS Registry Number 858956-35-1

End-use product (EP) 2 lb/gal SL (DuPont MethodTM 240 SL; EPA Reg. No. 352-786; equivalent to 

2 lb ae/gal aminocyclopyrachlor)

Table 2. Physiochemical Properties of Aminocyclopyrachlor 

Parameter Value Reference

Aminocyclopyrachlor (DPX-MAT28)

Melting point 140.8oC DP# 369057, J. Ryman et al.,

3/17/10 pH (20.1°C) 3.34

Density (20°C) 1.34 g/mL 

Water solubility (20°C) 3.13 g/L (pH 4)

4.20 g/L (pH 7)

3.87 g/L (pH 9)

Vapor pressure 6.92 x10-6Pa (20°C)

4.91 x10-6Pa (25°C)
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Table 2. Physiochemical Properties of Aminocyclopyrachlor 

Parameter Value Reference

Dissociation constant (20°C) 4.65

Octanol/water partition coefficient 

(log10) at 20°C

-1.01 (pH 4)

-2.48 (pH 7)

1.07 (mili-Q water)

UV/visible absorption spectrum pH/nm

1.8/220

7.0/285, 240, 210

10.5/280, 240, 210

Aminocyclopyrachlor-methyl (DPX-KJM44)

Melting point 148.9oC DP# 369057, J. Ryman et al.,

3/17/10 pH (20.1°C) 6.16

Density (20°C) 1.44 g/mL

Water solubility (20°C) 0.354 g/L

Vapor pressure 4.19 x10-4Pa (20°C)

4.45 x10-4Pa (25°C)

Dissociation constant (20°C) Not applicable

Octanol/water partition coefficient 

(log10) at 20°C

1.87

UV/visible absorption spectrum pH/nm

1.8/300, 220

7.0/300, 235, 205

10.5/285, 235

860.1200 Directions for Use

DuPont has submitted draft amended labels for the 50% WG formulation (EPA Reg. No. 352-

787), the 2 lb/gal SL formulation (EPA Reg. No. 352-786) of the K salt, and the 80% WG 

formulation (EPA Reg. No. 352-786) of aminocyclopyrachlor-methyl. A summary of the 

proposed use pattern is presented in Table 3. 
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Table 3. Summary of Directions for Use of Aminocyclopyrachlor.

Applic. Timing, 

Type, and 

Equip.1

Formulation

[EPA Reg. No.]

Applic. 

Rate2

(lb ai/A)

Max. No. 

Applic. per 

Season 2

Max. 

Seasonal 

Applic. 

Rate

(lb ai/A)

PHI

(days)

Use Directions and 

Limitations

Pasture (including grass grown for hay) and Rangeland Grasses

Foliar,

Broadcast,

Ground (min. 10 

gal/A) or aerial 

(min. 2 gal/A)

50% WG [352-787]

2 lb/gal SL of the K 

salt 3

[352-786]

80% WG of 

aminocyclopyrachlormethyl 4

[352-785]

0.038-

0.172 2 0.281

0

(forage 

and hay)

Apply to new plantings when 

the majority of grasses are in 

the 3- to 4-leaf stage or to 

perennial native grasses and 

pasture grasses established for 

at least one growing season. 

A 30-day treatment interval is 

specified. Use of a spray 

adjuvant (nonionic surfactant 

or crop oil concentrate) is 

specified. Minimum spray 

volume of 10 gal/A for 

ground applications and 2 

gal/A for aerial applications.

1

 Do not apply through any type of irrigation system; a 12-hour reentry interval is specified.

2

 Rates expressed in terms of the aminocyclopyrachlor ai. Based on calculations, individual maximum application 

rates are 0.166 lb ai/A for the 50% WG, 0.172 lb ai/A for the 2 lb/gal K SL, and 0.164 lb ai/A for the 80% WG 

formulation. 

3

 Equivalent to 2 lb ae/gal aminocyclopyrachlor.

4

 Equivalent to 75% ae/gal aminocyclopyrachlor.

The labels state that a nonionic surfactant (NIS) is the preferred adjuvant, to be included at 0.06-

0.50% v/v; crop oil concentrates (COCs), including petroleum or modified seed oil (MSO) may 

be used at up to 0.5% v/v for MSOs or at 1-2% v/v for all others.

The products may be tank mixed with other herbicides, insecticides, and fungicides that are 

registered for the same use sites, methods of application, and timings. When tank mixing, the 

most restrictive label limitations of the products being used are to be followed; use of a spray 

adjuvant is specified for postemergence applications.

The following rotational crop restrictions are specified: a 4-month PBI is specified for grasses 

(over-seeding or renovation); and a 1-year PBI is specified for all other crops. Forage legumes 

may be seeded after a soil bioassay has been conducted verifying that the level of 

aminocyclopyrachlor in the soil will not adversely effect the new crop. 

Conclusions. The submitted use directions are sufficient to allow for evaluation of the available 

residue data relative to the proposed use. The submitted field trial data for grass reflect the 

maximum proposed use rate and the minimum PHI and support the use of spray adjuvants for 

applications to grasses. 

The results of the confined rotational crop study indicate that limited rotational crop studies are 

required to establish PBIs and/or tolerances for rotated crops. Pending submission of the 

required limited field rotational crop trials, the labels must be revised to prohibit rotation to any 
Aminocyclopyrachlor Summary of Analytical Chemistry and Residue Data DP#: D387442

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crop other than grasses following application of aminocyclopyrachlor or aminocyclopyrachlormethyl.

860.1300 Nature of the Residue - Plants

DER Reference: 48333617.DER

E. I. du Pont de Nemours and Company has submitted a study investigating the metabolism of 

[2-pyrimidinyl14C]aminocyclopyrachlor-methyl (specific activity 1.64 MBq/mg) following a 

single foliar application to grass. Aminocyclopyrachlor-methyl (DPX-KJM44) is the methyl 

ester of aminocyclopyrachlor (DPX-MAT28). The radiolabeled test substance was formulated as 

a 25% wettable powder (WP) and applied at a nominal rate of 0.333 lb ai/A (373 g ai/ha), 

equivalent to 0.312 lb ae/A (350 g ae/ha) aminocyclopyrachlor. The application rate corresponds 

to 1.1x the maximum seasonal application rate for grass. Grass foliage samples were harvested 

immediately following application (0 days), and 3, 7, 14, 30, and 60 days after application 

(DAA), and were subjected to an acetonitrile (ACN) surface wash prior to storage. The in-life 

and analytical phases of the study were conducted by Charles River Laboratories (Tranent, 

Edinburgh, UK).

Total radioactive residues (TRR) in grass were determined by summing radioactivity in surface 

washes, extracts, and nonextractable residues. TRR were 15.6, 15.4, 12.0, 5.94, 4.08, and 2.45 

ppm in grass foliage harvested 0, 3, 7, 14, 30, and 60 DAA.

The TRR removed by the ACN surface wash declined from 13% TRR (2.03 ppm) at 0 DAA to 

1.2% TRR (0.030 ppm) at 60 DAA. Extraction with ACN:formic acid (8:2, v:v) released the 

majority of radioactivity from all but the 60-DAA grass samples: extractable residues decreased 

from 76.6% TRR (12.0 ppm) at 0 DAA to 35.4% TRR (0.866 ppm) at 60 DAA. Subsequent 

extraction with ACN:formic acid (1:1, v:v) removed 8.3-12.0% TRR (1.28- 0.715 ppm). 

Nonextractable residues remaining following extraction increased with harvest interval, from 

1.8% TRR (0.280 ppm) at 0 DAA to 51.7% TRR (1.27 ppm) at 60 DAA. The 0, 7, and 60 DAA 

nonextractable residues were subjected to enzyme, base, and acid hydrolysis. Enzyme 

hydrolysis with α-amylase (50 oC for 72 hours) followed by a mixture of amyloglucosidase and 

cellulase (50 oC for 48 hours) released, respectively, 0.7% and 0.3% TRR from the 0-DAA 

sample, 1.5% and 1.0% TRR from the 7-DAA sample, and 14.0% and 6.3% TRR from the 60-

DAA sample. Base (0.1 N NaOH; 60 oC for 6 hours) and acid (1 M HCl; 60 oC for 6 hours) 

hydrolysis each released 0.1% TRR from the 0-DAA sample and 0.4% TRR from the 7-DAA 

sample, and released 4.8% and 3.4% TRR, respectively, from 60-DAA sample. The 

nonextractable residues remaining following extraction and hydrolysis accounted for 0.6% TRR 

(0.102 ppm) in 0-DAA, 4.7% TRR (0.553 ppm) in 7-DAA, and 23.4% TRR (0.572 ppm) in 60-

DAA samples. 

These procedures adequately extracted the majority of residues from grass collected at all harvest 

intervals with the exception of 60 DAA. With respect to the 60-DAA sample, HED notes that 

20% TRR was attributed to loss during analysis associated primarily with solid-phase extraction 

(SPE) cleanup; therefore, further characterization procedures (e.g., strong acid or base 

hydrolysis) are unlikely to yield further elucidation of the metabolite profile. Extraction results 
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were normalized; therefore, accountabilities were 100%. Residues were initially identified and 

quantitated by high performance liquid chromatography (HPLC); identification of 

aminocyclopyrachlor-methyl and major metabolites was confirmed by liquid 

chromatography/mass spectroscopy (LC/MS). 

Samples were stored frozen for up to 4.5 months prior to completion of initial analysis. A 60-

DAA sample was re-extracted and analyzed at the end of the study following storage at -20 °C 

for 13 months to confirm the stability of the metabolite profile.

Aminocyclopyrachlor-methyl was identified in grass from all harvest intervals; residues declined 

from 24.7% TRR (3.86 ppm) at 0 DAA to 8.6% TRR (0.211 ppm) at 60 DAA. 

aminocyclopyrachlor was the major identified residue in grass samples at all harvest intervals, 

accounting for 32.9-67.7% TRR (0.805-10.5 ppm). Several minor metabolites were identified, 

including IN-LXT69, IN-QFH57, IN-QGC48, IN-Q3007, and IN-V0977. IN-LXT69 was 

identified at all sampling intervals, accounting for 4.2-6.1% TRR (0.138- 0.769 ppm); the 

remaining metabolites were each present at ≤ 4.1% TRR.

Radiovalidation data were submitted for the extraction procedure of the proposed residue 

analytical enforcement method, DuPont-22582 and are discussed under 860.1340 Residue 

Analytical Methods. 

Based on the results of the study, the petitioner concluded that aminocyclopyrachlor-methyl is 

rapidly metabolized (demethylated) in grass to form the free acid aminocyclopyrachlor, which is 

subsequently decarboxylated to form IN-LXT69. Photo-induced simultaneous elimination of 

hydrogen chloride and pyrimidine ring contraction (occurring as a minor pathway) yields the 

imidazole-nitrile metabolite, IN-QGC48, which undergoes demethylation to form IN-QFH57; 

IN-QFH57 may also be formed through photolysis of aminocyclopyrachlor. An additional minor 

pathway involves pyrimidine ring opening proceeding through the postulated intermediate INYY905, with subsequent oxidations to form the amide and carboxylic acid compounds, INQ3007 and IN-V0977, respectively. Chemical structures are shown in Appendix 1.

Conclusions. The submitted grass metabolism study is adequate to satisfy data requirements. 

Based on the submitted data, HED concludes that the nature of the residue in grass is adequately 

understood for purposes of this petition. The residues of concern for tolerance enforcement and 

risk assessment are aminocyclopyrachlor and aminocyclopyrachlor-methyl (expressed in parent 

equivalents). Additional metabolism studies may be needed to support future uses on additional 

crops.
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860.1300 Nature of the Residue - Livestock

DER Reference: 48333618.DER

Ruminants

E. I. du Pont de Nemours and Company has submitted a study investigating the metabolism of 

[2-pyrimidinyl14C]aminocyclopyrachlor-methyl (DPX-KJM44) in the lactating goat (specific 

activity 1.64 Bq/mg). The test substance was administered orally twice daily via gelatin capsule 

to one goat at a nominal 75 ppm in the diet for 5 consecutive days. Based on feed consumption, 

actual mean dose level was 91ppm (parent acid equivalents) (1x the dietary burden to cattle). 

Milk was collected twice daily throughout the study, before each dosing; tissues, including 

muscle (composite of loin, hind, and fore quarter), fat (omental, renal, and subcutaneous), liver, 

and kidney were collected at sacrifice, approximately 6 hours after the final dose. The in-life and 

analytical phases of the study were conducted by Charles River Laboratories (Edinburgh, UK).

Following oral dosing at 97.3 ppm for 5 consecutive days, TRR were 0.015-0.031 ppm in milk, 

0.299 ppm in liver, 1.673 ppm in kidney, 0.042 ppm in muscle, 0.01 ppm in omental fat, 0.016 

ppm in renal fat, and 0.026 ppm in subcutaneous fat. Centrifugation of milk into skim milk and 

cream demonstrated that the majority of radioactive residues were present in the cream fraction. 

Radioactive concentrations in cream and skim milk were 0.118 and 0.016 ppm, respectively. 

Radioactivity was highest in kidney and lowest in fat. Radioactivity in milk appeared to plateau 

by Day 3. Most of the administered dose was excreted (~77%), with 20.02% in the feces, 

54.07% in urine, and 3.14% in cage wash.

Extraction with 0.1% formic acid in ACN/water (tissues) or acetone (milk) released the majority 

of the radioactivity from all goat matrices, except omental fat: 86.7% TRR from liver, 98.3% 

TRR from kidney, 87.5% TRR from muscle, 80.5% TRR from milk, 83.8% TRR from renal fat, 

and 80.7% TRR from subcutaneous fat. Only 47.5% TRR was released in omental fat. Initial 

extraction of cream with hexane and acetone released 11.36% TRR in the acetone fraction and 

84.96% TRR in the hexane fraction. The liver and kidney samples required SPE clean-up prior 

to HPLC analysis to provide reproducible chromatographic profiles. Efforts to improve low 

recoveries resulting from SPE clean-up impaired the quality of the chromatography, resulting in 

a significant loss of radioactive residues in the extracts; residues in the extracts after SPE cleanup 

were 57.40% TRR in liver and 55.26% TRR in kidney. Nonextractable residues were not 

investigated further in muscle, milk, renal fat, subcutaneous fat, or omental fat; remaining 

nonextractable residues were 12.5% TRR (0.005 ppm), 19.5% TRR (0.004 ppm), 16.2% TRR 

(0.003 ppm), 19.3% TRR (0.005 ppm), and 52.6% TRR (0.005 ppm), respectively. 

Nonextractable residues of liver and kidney were subjected to sequential pepsin and protease 

enzyme hydrolysis which released 10.1% TRR and 1.5% TRR in liver, respectively, and 0.9% 

TRR and 0.12% TRR in kidney, respectively. Nonextractable residues remaining were 1.7% 

TRR (0.006 ppm) in liver and 0.68% TRR (0.011 ppm) in kidney. These procedures adequately 

extracted the majority of the residues from goat matrices. Results were normalized, thus 

accountabilities were 100% in all goat matrices.

Residues were initially identified and quantitated by HPLC. Identification of the parent acid, 

aminocyclopyrachlor, was confirmed in liver and kidney extracts prior to SPE clean-up by TLC 
Aminocyclopyrachlor Summary of Analytical Chemistry and Residue Data DP#: D387442

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co-chromatography and in kidney extracts after SPE clean-up by LC/MS/MS. Liver, kidney, 

muscle, and fat (renal and subcutaneous) were stored frozen for a maximum of 3.3 months prior 

to HPLC analysis. Omental fat and milk samples were initially extracted within 2.1 months of 

sample collection and analyzed within 8.4 months of sample collection; milk was subsequently 

re-extracted and analyzed within 10.7 months of sample collection. The petitioner demonstrated 

that the metabolic profile in liver and kidney is relatively stable for 11 months. No additional 

storage stability data are required for omental fat because the TRR level was below the threshold 

concentration requiring metabolite identification. Storage stability data for liver will be translated 

to milk.

Aminocyclopyrachlor-methyl was not detected in excreta, milk, or any tissue. The parent acid, 

aminocyclopyrachlor, was the only compound identified and was found in all matrices. It was 

the single radiolabeled component detected in liver (65.7% TRR; 0.197 ppm), kidney (55.3% 

TRR; 0.925 ppm), omental fat (47.5% TRR; 0.005 ppm), renal fat (83.8% TRR; 0.013 ppm), and 

subcutaneous fat (80.7% TRR; 0.021 ppm). Aminocyclopyrachlor was detected in muscle at 

43.3% TRR (0.018 ppm) along with two unknowns (14.4-18.3% TRR; 0.006- 0.008 ppm), and in 

milk at 15.9% TRR (0.004 ppm) along with three unknowns (7.4-29.5% TRR; 0.002-0.007 

ppm). TLC analysis of liver and kidney extracts prior to SPE clean-up (86.7% TRR and 98.3% 

TRR, respectively) confirmed that aminocyclopyrachlor was the only compound present in these 

samples.

Based on the study results, the petitioner concluded that aminocyclopyrachlor-methyl is rapidly 

metabolized in the goat and is eliminated as aminocyclopyrachlor primarily in the excreta. 

Chemical structures are shown in Appendix 1.

Conclusions. The submitted goat metabolism study is adequate to satisfy data requirements. 

Based on the submitted data, HED concludes that the nature of the residue in livestock is 

adequately understood for purposes of this petition. The residues of concern for tolerance 

enforcement and risk assessment are aminocyclopyrachlor and aminocyclopyrachlor-methyl

(expressed in parent equivalents). 

Because grass is not a significant feed stuff for poultry, a hen metabolism study is not required at 

this time; however, a hen metabolism study may be needed to support future uses on additional 

crops.
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860.1340 Residue Analytical Methods

DER References: 48333620.DER (Plant method; includes review of MRIDs 48333617, 48333621, 48333625, and 

48333626)

48333622.DER (Livestock method; includes review of MRIDs 48333623 and 48333627)

Plant Method 

Enforcement method: DuPont has submitted an LC/MS/MS method, DuPont-22582 and revision 

DuPont-22582 SU1 RV2, for the determination of aminocyclopyrachlor (DPX-MAT28), 

aminocyclopyrachlor-methyl (DPX-KJM44), and metabolites IN-LXT69, QFH57, and INQGC48 in/on grass forage and hay. DuPont is proposing the revised method as an enforcement 

method, and has submitted method descriptions, method validation data, radiovalidation data, 

and ILVs of the method. The LC/MS/MS methods were used for data collection in the storage 

stability and crop field trial studies reviewed under PP#0F7817 (this petition). 

The method submissions include: (1) a description and validation data for the original method 

(DuPont-22582; MRID 48333620), which determines residues of aminocyclopyrachlor, 

aminocyclopyrachlor-methyl, and IN-LXT69 only; (2) a description and validation data for the 

revised version of the method (Supplement No. 1, Revision Nos. 1 and 2; DuPont-22582 SU1 

RV2; MRID 48333621) which includes analysis for metabolites IN-QFH57 and IN-QGC48 and 

incorporates changes to the method resulting from the ILV studies; (3) two ILV studies (MRIDs 

48333625 and 48333626); and (4) radiovalidation conducted in conjunction with the grass 

metabolism study (MRID 48333617). Except as noted, the method addressed and described 

hereafter is DuPont-22582 SU1 RV2. 

Briefly, samples are soaked in 0.15 M ammonium acetate, then extracted with ACN and 

centrifuged. The supernatant is reserved, and the sample is extracted with ACN:0.15 M 

ammonium acetate (70:30, v:v) and centrifuged. The supernatants are combined, 0.1 N HCl is 

added, and the extract is diluted with water. For analysis of aminocyclopyrachlor, 

aminocyclopyrachlor-methyl, IN-LXT69, and IN-QGC48, the extract is concentrated, then 

diluted with 0.5% formic acid and purified through a strong anion exchange (SAX) SPE

cartridge after which it is transferred to a mixed-mode (cation exchange and reverse-phase; 

MCX) SPE cartridge. Residues are eluted with 75 mM ammonium hydroxide in methanol, and 

the eluate is combined with 0.2% formic acid, concentrated, and diluted with 0.01% formic acid, 

then filtered for analysis by LC/MS/MS. For analysis of IN-QFH57, the extract is concentrated, 

then diluted with 0.01% formic acid and purified through a SAX SPE cartridge. Residues are 

eluted with 1% formic acid in methanol, and the eluate is combined with 0.01% formic acid, 

concentrated, and diluted with 0.01% formic acid, then filtered for analysis by LC/MS/MS. Two 

transition ions are monitored for each analyte. An HPLC using a Phenomenex Phenyl-Hexyl 

analytical column and a gradient mobile phase of 0.1% formic acid in water and methanol; and 

an Applied Biosystems API-5000 Triple Quadrupole with electrospray interface (ESI) positive 

(negative for IN-QHF57) mode Multiple Reaction Monitoring (MRM).
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The transition ions monitored are:

Aminocyclopyrachlor-methyl: 228→68 m/z and 228→168 m/z

Aminocyclopyrachlor: 214→68 m/z and 214→101 m/z

IN-LXT69: 170→76 m/z and 170→103 m/z

IN-QFH57: 176→132 m/z and 176→105 m/z

IN-QGC48: 192→178 m/z and 192→132 m/z

Based on the lowest level of method validation, the LOQ is 0.01 ppm for all analytes in all 

matrices. The reported limits of detection (LODs) (based on 3X the baseline noise in a control 

extract) are 0.002 ppm for aminocyclopyrachlor, aminocyclopyrachlor-methyl, and IN-QGC48, 

0.003 ppm for IN-QFH57, and 0.0003 ppm for IN-LXT69 in/on grass forage; and 0.002 ppm for 

aminocyclopyrachlor, aminocyclopyrachlor-methyl, and IN-QGC48, 0.003 ppm for IN-QFH57, 

and 0.0005 ppm for IN-LXT69 in/on grass hay.

Acceptable method validation recoveries for DuPont-22582 and DuPont-22582 SU1 RV2 were 

obtained for all analytes from samples of grass forage and hay fortified at 0.01 and 0.10 ppm. 

Mean recoveries and coefficients of variation (CVs) were 73-95% (0-8.9%) for DuPont-22582 

and 71-93% (1.0-17%) for DuPont-22582 SU1 RV2. The validation data include results of an 

analytical laboratory method tryout (MTO) conducted by ABC Laboratories. Acceptable method 

validation recoveries were obtained for all analytes from samples of grass forage and hay. The 

fortification levels used in method validation, in conjunction with concurrent method validation, 

are adequate to bracket expected residue levels in/on grass forage and hay.

Two ILV studies were also conducted using samples of grass hay fortified at 0.010 and 0.10 ppm 

for all analytes. The first ILV study was conducted on DuPont-22582 Supplement 1 by MPI 

Research, Inc. (State College, PA), and the second ILV study was conducted on DuPont-22582 

Supplement 1 (Revision 1) by ABC Laboratories (Columbia, MO). The first ILV study was 

unsuccessful for aminocyclopyrachlor, aminocyclopyrachlor-methyl, IN-LXT69, and INQGC48; only IN-QFH57 was successfully recovered in the second of three trials, with mean 

recoveries of 97-111%. The second ILV, which reflected an alternative simplified purification 

procedure that used SAX SPE only, was successful for recovery of aminocyclopyrachlor-methyl, 

aminocyclopyrachlor, IN-LXT69, and IN-QGC48. The petitioner indicated that additional 

results from the second ILV reflecting the SPE/MCX purification procedures described above 

will be reported separately (in Study No. 65869a/D-30574, Supplement 1).

For the second ILV study to be acceptable, the petitioner must confirm that the laboratory 

personnel involved in the ILV were unfamiliar with the method. OPPTS 860.1340 requires that 

the personnel chosen to conduct the ILV trials must be unfamiliar with the method, both in its 

development and in its subsequent use in analyzing field samples. Because ABC Laboratories 

was the analytical laboratory for the storage stability and crop field trials reviewed under 

PP#0F7817, performed an analytical laboratory MTO on DuPont-22582, and was responsible for 

the development of the alternative SAX SPE cleanup procedure that was validated in the second 

ILV study, it appears there may be a potential conflict with the guideline requirements for ILV. 

The registrant has since submitted information stating the personnel involved in the ILV were 

not involved in method development (XXXXXXXX) therefore, this deficiency is resolved.
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DuPont submitted radiovalidation data with the grass metabolism study to evaluate the efficiency 

of the extraction methodology presented in DuPont-22582 for extracting aminocyclopyrachlor

and IN-QFH57 from field-grown grass. Aminocyclopyrachlor-methyl, IN-LXT69, and INQGC48 were also evaluated; however, resolution using the residue analytical method was 

inadequate to allow individual quantification using HPLC methodology. The extraction 

efficiencies were determined to be 108%, 126%, and 73%, respectively, for 

aminocyclopyrachlor, IN-QFH57, and components with a similar retention time to IN-LXT69, 

IN-QGC48, and aminocyclopyrachlor–methyl in 14C-labeled grass. 

A confirmatory method was not included; however none is required because the LC/MS/MS 

method monitors two transition ions for each analyte.

Data collection methods: The proposed enforcement method, DuPont-22582 SU1 RV2, and 

earlier versions of the method, including DuPont-22582 and DuPont-22582, Supplement No. 1, 

were used for data collection in the storage stability and crop field trial studies reviewed under 

PP#0F7817. Original method DuPont-22582 included analysis for aminocyclopyrachlor, 

aminocyclopyrachlor-methyl, and IN-LXT69, and DuPont-22582, Supplement No. 1 added 

analysis for metabolites IN-QFH57 and IN-QGC48. The methods were adequately validated 

concurrently with the storage stability and crop field trial studies. 

Livestock Method

DuPont has submitted an LC/MS/MS method, DuPont-25836 and a revised version of the 

method, DuPont-27162, Revision No. 1, for the determination of aminocyclopyrachlor (DPXMAT28), aminocyclopyrachlor-methyl (DPX-KJM44), and metabolite IN-LXT69 in bovine 

muscle, liver, kidney, fat, milk, and feces. DuPont is proposing the revised method as an 

enforcement method, and has submitted method descriptions, method validation data, and ILV of 

the method. The LC/MS/MS method was used for data collection in the cattle feeding study 

reviewed under PP#0F7817. 

The method submissions include: (1) a description and validation data for the original method 

(DuPont-25836; MRID 48333623); (2) a description and validation data for the revised version 

of the method (DuPont-27162, Revision No. 1; MRID 48333622) which includes minor 

modifications to the method and incorporates changes to the method resulting from the ILV 

study; and (3) an ILV (MRIDs 48333627) conducted on DuPont-27162. Except as noted, the 

method addressed and described hereafter is DuPont-27162, Revision No. 1. We note that, 

although the procedures of methods DuPont-25836 and DuPont-27162 are essentially identical, 

the method description for DuPont-27162 establishes separate sections for analysis of milk 

(Method No. 1474A), bovine muscle and feces (Method No. 1474B), and bovine liver, kidney, 

and fat (Method No. 1474C). In addition, the original method provides instructions for analysis 

of skim milk, cream, whole eggs, and fish, while the revised method does not include these 

matrices.

Briefly, milk samples are extracted twice with ACN:0.1% formic acid (90:10, v:v) and 

centrifuged. The combined extracts are diluted with extraction solvent, then adjusted to volume 

with 0.01% formic acid for analysis by LC/MS/MS. Liver, kidney, fat, muscle, and feces 
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samples are extracted sequentially with ACN:0.1% aqueous formic acid (at 90:10, v:v; 70:30, 

v/v; and 50:50, v/v) and centrifuged. The combined extracts are diluted with 0.1% formic acid 

and concentrated. An aliquot of the concentrated extract of liver, kidney, and fat is diluted with 

0.01% formic acid for analysis by LC/MS/MS. An aliquot of the extract of muscles and feces is 

diluted with 0.2% aqueous formic acid and purified on an MCX SPE cartridge. Residues are 

eluted with 75 mM ammonium hydroxide in methanol, and the eluate is combined with 0.2% 

formic acid, concentrated, and combined with 0.01% formic acid for analysis by LC/MS/MS. 

Two ion transitions are monitored for each analyte. An HPLC using a Phenomenex Luna 

Phenyl-Hexyl analytical column and a gradient mobile phase of 0.01 M aqueous formic acid and 

methanol; and an Applied Biosystems API-4000 Triple Quadrupole with turbo ion spray 

interface in positive mode Multiple Reaction Monitoring (MRM) was used. The method notes 

that if background levels of AMINOCYCLOPYRACHLOR-METHYL are found, this analyte 

may also be analyzed with an isocratic mobile phase of 0.01 M formic acid:methanol at 40:60 

(v:v).

The transition ions monitored are:

Aminocyclopyrachlor-methyl: 228.1→68.2 m/z and 228.1→100.9 m/z

Aminocyclopyrachlor: 214.2→68.1 m/z and 214.2→101.1 m/z

IN-LXT69: 170.1→76.1 m/z and 170.1→103.1 m/z

Based on the LLMV, the LOQ is 0.01 ppm for all analytes in all matrices. The reported LODs 

(based on 3X the baseline noise in a control extract) for aminocyclopyrachlor, 

aminocyclopyrachlor-methyl, and IN-LXT69, respectively, are 0.0065, 0.0021, and 0.0022 ppm 

in muscle; 0.0074, 0.00044, and 0.0010 ppm in liver; 0.0056, 0.0016, and 0.0014 ppm in kidney; 

0.0056, 0.00059, and 0.0010 ppm in fat; 0.0055, 0.00091, and 0.0028 ppm in milk; and 0.0039, 

0.0012, and 0.0015 ppm in feces.

Acceptable method validation recoveries for method DuPont-25836 were obtained for all 

analytes from samples of bovine muscle, liver, kidney, fat, skim milk, whole milk, heavy cream, 

whole eggs, and fish fortified at 0.01 and 0.10 ppm. The mean recoveries were 81-103% for 

aminocyclopyrachlor, 79-106% for aminocyclopyrachlor-methyl, and 74-102% for IN-LXT69,

with CVs <20% for each matrix tested. Acceptable method validation recoveries for method 

DuPont-27162, Revision No. 1 were obtained for all analytes from samples of bovine muscle, 

liver, kidney, fat, milk, and feces fortified at 0.01 and 0.10 ppm. The mean recoveries were 75-

111% for aminocyclopyrachlor, 77-104% for aminocyclopyrachlor-methyl, and 73-103% for INLXT69, with CVs <20% for each matrix tested. The fortification levels used in method 

validation in conjunction with concurrent method validation are adequate to bracket expected 

residue levels in livestock tissues and milk.

An ILV study was also conducted on DuPont-27162 using samples of bovine liver, milk, and 

eggs fortified with aminocyclopyrachlor, aminocyclopyrachlor-methyl, and IN-LXT69 at 0.010 

and 0.10 ppm. The first trial was successful for all analytes in milk and eggs, with acceptable 

mean recoveries ranging from 92%-110% (CVs <20%). The first trial was also successful for 

IN-LXT69 in bovine liver (mean recoveries 102-106%) but was unsuccessful for 

aminocyclopyrachlor and aminocyclopyrachlor-methyl. Low recoveries for 

aminocyclopyrachlor –methyl and high recoveries for aminocyclopyrachlor indicated that 
Aminocyclopyrachlor Summary of Analytical Chemistry and Residue Data DP#: D387442

Page 19 of 43

aminocyclopyrachlor –methyl was converting to aminocyclopyrachlor during the analysis. The 

second trial for liver was successful for aminocyclopyrachlor and aminocyclopyrachlor –methyl 

(mean recoveries 80-97%) when the performance validation set was separated into four smaller 

sub-sets to minimize the observed degradation of aminocyclopyrachlor-methyl.

No radiovalidation data were submitted to support the submitted livestock analytical method; 

however, no data are required because the extraction solvents used in the goat metabolism study 

are the same as those used in the residue analytical method. Acceptable extraction efficiencies

were indicated in the metabolism study; therefore, no additional data are required. 

A confirmatory method was not included; however none is required because the LC/MS/MS 

method monitors two ion transitions for each analyte.

Data collection methods: An earlier version of the proposed enforcement method, DuPont27162, was used for data collection in the storage stability and cattle feeding studies reviewed 

under PP#0F7817. The method included analysis for aminocyclopyrachlor, 

aminocyclopyrachlor, and IN-LXT69 in milk and bovine tissues. The method was adequately 

validated concurrently with the storage stability and crop field trial studies. 

Conclusions. The submitted residue analytical methods data are adequate to satisfy data 

requirements for the subject petition. HED has concluded that the livestock method is adequate 

for enforcement purposes, and that the grass method is adequate for enforcement purposes. The 

Agency has considered the submitted data and has reviewed the analytical methods against the 

TMV (Tolerance Method Validation) checklist contained in ACB (Analytical Chemistry 

Branch/BEAD)’s SOP No. 019, Revision 1.0. HED has determined that TMVs are not needed 

for the proposed enforcement methods for plant and livestock commodities. 

The analytical methods submitted under the subject action do not provide for conversion of 

residues of aminocyclopyrachlor-methyl to stoichiometric equivalents of aminocyclopyrachlor 

and the residue data presented herein do not reflect correction to stoichiometric equivalents. The 

conversion factor, based on molecular weights (MWs) of 213.6 for aminocyclopyrachlor and 

227.6 for aminocyclopyrachlor-methyl is 0.93849. 

860.1360 Multiresidue Methods

DER References: 48333624.DER

DuPont has submitted multiresidue methods testing data for aminocyclopyrachlor (DPXMAT28) and aminocyclopyrachlor-methyl (DPX-KJM44). The test substances were screened 

through multiresidue methods described in the U.S. FDA Pesticide Analytical Manual Volume I 

(PAM Vol. I). The study was conducted by Pyxant Labs Inc. (Colorado Springs, CO). 

AMINOCYCLOPYRACHLOR was tested through Protocols A, B, and C; based on the results 

of these tests, it was not further tested through Protocols D, E, or F. Aminocyclopyrachlormethyl was tested through Protocols A, B (via methylation of aminocyclopyrachlor), C, D, E and 

F. Neither aminocyclopyrachlor nor aminocyclopyrachlor-methyl was tested under Protocol G 

because the compounds are not substituted ureas. 
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The test substances were not found to be naturally fluorescent; therefore, further testing under 

Protocol A was not required.

Protocol B testing was conducted on aminocyclopyrachlor because it has an acid structure; 

methylation in Protocol B testing yielded the methyl ester, aminocyclopyrachlor-methyl. Both 

test substances were found to be chromatographable in Protocol C testing; therefore, 

aminocyclopyrachlor was methylated according to Protocol B with observed conversion of 

37.2% to the methyl ester (DPX-KJM44). Acceptable recovery was obtained through Florisil 

(93%), but recovery through gel permeation chromatography (GPC) was unacceptable (14.2%); 

therefore, no further testing was conducted under Protocol B.

In Protocol C testing aminocyclopyrachlor was chromatographable in Section 302, Level II 

testing, using module DG-5 with nitrogen-phosphorus detection (NPD). Aminocyclopyrachlormethyl was chromatographable in Section 302, Level I testing, using module DG-5 (NPD). The 

results of Protocol C testing indicated that further testing of aminocyclopyrachlor-methyl under 

Protocols D-F was required. 

Based on the results of Protocol C testing, aminocyclopyrachlor-methyl was tested through 

Protocol D without cleanup. Testing under Protocol D, Section 302, E1, yielded complete 

recovery (109%) of aminocyclopyrachlor-methyl in skim milk fortified at 0.1 ppm and partial 

recovery (53%) in skim milk fortified at 0.5 ppm. 

Testing of aminocyclopyrachlor-methyl through Protocols E and F was suspended because 

recovery through Florisil was unacceptable. 

These data indicate that Protocol D described in FDA PAM Vol. I may be applicable for 

determination of aminocyclopyrachlor-methyl; however, the FDA multiresidue methods are not 

appropriate for determining residues of aminocyclopyrachlor, or for the two compounds 

(aminocyclopyrachlor-methyl and aminocyclopyrachlor) together.

Conclusions. The submitted multiresidue methods test data for aminocyclopyrachlor and DPXKLM44 are acceptable. The data indicate that multiresidue methods are not suitable for 

determination of aminocyclopyrachlor or for determination of the two analytes together. The 

submitted data will be forwarded to the U.S. FDA for further evaluation.
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860.1380 Storage Stability

DER References: 48333628.DER (Grass; includes review of MRID 48333629)

48363401.DE2 (Milk, eggs, and bovine tissues)

Grass

DuPont has submitted the results of two storage stability studies with aminocyclopyrachlor 

(DPX-MAT28), aminocyclopyrachlor-methyl (DPX-KJM44), and the metabolites, IN-LXT69, 

IN-QFH57, and IN-QGC48 in grass forage and hay. Separate studies were submitted for 

aminocyclopyrachlor, aminocyclopyrachlor-methyl, and IN-LXT69 (MRID 48333628), and for 

IN-QFH57 and IN-QGC48 (MRID 48333629). Samples of untreated grass forage and hay were 

fortified with aminocyclopyrachlor, aminocyclopyrachlor-methyl, and IN-LXT69 at 0.50 ppm 

each for forage and 1.0 ppm each for hay, and with IN-QFH57 and IN-QGC48 at 0.30 ppm each 

for both forage and hay. The fortified samples were stored frozen (-20 °C) and analyzed at target 

intervals of 0, 7, 14, 30, 60, 90, 150, 210, 300, 360, and 400-500 days. Both studies were 

conducted by ABC Laboratories, Inc. (Columbia, MO). 

Grass forage and hay samples were analyzed for residues of aminocyclopyrachlor, 

aminocyclopyrachlor-methyl, IN-LXT69, IN-QFH57, and IN-QGC48 by LC/MS/MS using 

DuPont-22582 (for analysis of aminocyclopyrachlor, aminocyclopyrachlor-methyl, IN-LXT69) 

and DuPont-22582 Supplement No.1 (for analysis of IN-QFH57 and IN-QGC48). The methods 

are acceptable for data collection based on adequate method validation data and concurrent 

method recovery data. The validated LOQ was 0.01 ppm in grass forage and hay. 

The study results indicate that residues of aminocyclopyrachlor, aminocyclopyrachlor-methyl, 

and IN-LXT69 are stable in/on grass forage and hay stored frozen (-20 °C) for up to 499-502 

days (~16.5 months), and residues of IN-QFH57 and IN-QGC48 are stable in/on grass forage 

and hay stored frozen for up to 401-402 days (13.2 months).
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Sample storage intervals and conditions

The storage durations and conditions of samples from the crop field trials and processing studies 

submitted to support this petition are presented in Table 4. 

Table 4. Summary of Storage Conditions and Durations of Samples from Crop Field Trial Study 

Matrix Analytes Storage 

Temperature (°C)

Actual Storage 

Duration

Interval of Demonstrated 

Storage Stability

Grass forage aminocyclopyrachlo

r, 

aminocyclopyrachlo

r-methyl, INLXT69, INQFH57, 

and IN-QGC48

-20 37-400 days

(1.2-13.2 months)

499-502 days (~16.5 months) 

for aminocyclopyrachlormethyl, 

aminocyclopyrachlor and 

IN-LXT69 and 401-402 

days (13.2 months) for 

metabolites IN-QFH57 and

IN-QGC48

Grass hay 41-408 days

(1.3-13.4 months)

Conclusions. Acceptable supporting storage stability data have been submitted for grass forage 

and hay. No additional storage stability data are required to support the submitted grass crop 

field trials.

Livestock Commodities

DuPont has submitted the results of a storage stability study with aminocyclopyrachlor (DPXMAT28), aminocyclopyrachlor-methyl (DPX-KJM44), and metabolite IN-LXT69 in milk, eggs, 

and bovine tissues. The study was conducted concurrently with the cattle feeding study. 

Samples of homogenized bovine muscle, liver, kidney, fat, milk, and eggs were fortified with 

aminocyclopyrachlor, aminocyclopyrachlor-methyl, and IN-LXT69 at 0.2 ppm. The fortified 

samples were placed in frozen storage at approximately -20 °C and analyzed at target intervals of 

1 and 2 weeks, and 1, 2, 3, and 5 months; kidney was not analyzed at 5 months. In addition, 

extracts of liver and kidney were stored frozen at ~-20 °C and analyzed after storage intervals of 

7 and 14 days. The study was conducted by Charles River Laboratories (Tranent, Edinburgh, 

Scotland) 

Samples of milk, eggs, and tissues were analyzed for residues of aminocyclopyrachlor, 

aminocyclopyrachlor-methyl, and metabolite IN-LXT69 by an LC/MS/MS method, DuPont27162. Samples of liver and kidney fortified with aminocyclopyrachlor-methyl were analyzed 

for residues of both aminocyclopyrachlor-methyl and aminocyclopyrachlor to investigate 

biotransformation. We note that the method description for DuPont-27162 establishes separate 

sections for analysis of milk (Method No. 1474A), bovine muscle and feces (Method No. 

1474B), and bovine liver, kidney, and fat (Method No. 1474C). This method is acceptable for 

data collection based on adequate method validation and concurrent recovery data. Based on the 

LLMV, the LOQ for aminocyclopyrachlor, aminocyclopyrachlor-methyl, and IN-LXT69 was 

0.01 ppm in milk and tissue samples.

The study results indicate that residues of aminocyclopyrachlor, aminocyclopyrachlor-methyl, 

and IN-LXT69 are stable in milk, eggs, and bovine muscle and fat stored frozen (~-20 °C) for up 

to 5 months, and that residues of aminocyclopyrachlor and IN-LXT69 are stable in liver and 
Aminocyclopyrachlor Summary of Analytical Chemistry and Residue Data DP#: D387442

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kidney for up to 5 and 3 months, respectively. aminocyclopyrachlor-methyl was not stable in 

homogenized liver or kidney stored frozen for ≥1 week; however, the recovery of 

aminocyclopyrachlor from samples fortified with aminocyclopyrachlor-methyl demonstrated the 

biotransformation of aminocyclopyrachlor-methyl to aminocyclopyrachlor under frozen storage 

conditions. When recoveries for aminocyclopyrachlor-methyl in stored samples were adjusted 

for biotransformation to aminocyclopyrachlor, corrected recoveries at all storage intervals were 

92-98% for liver and 91-102% for kidney. All analytes were found to be stable in extracts of 

liver and kidney stored frozen for up to 14 days. 

Sample storage intervals and conditions

The storage durations and conditions of samples from the cattle feeding submitted to support this 

petition are presented in Table 5. 

Table 5. Summary of Storage Conditions and Durations of Samples from the Cattle feeding Study

Matrix Analyte Storage 

Temperature 

(°C)

Actual Storage 

Duration

Interval of Demonstrated Storage 

Stability

Milk, skim milk, 

and cream

aminocyclopyrachlor,

aminocyclopyrachlormethyl, and

IN-LXT69

-20 2-65 days

(0.1-2.1 months)

Up to 146 days (4.8 months)

Muscle 12-44 days

(0.4-1.5 months)

Up to 138 days (4.5 months)

Fat 11-36 days

(0.4-1.2 months)

Up to 147 days (4.8 months)

Kidney 0 and 16-45 days

(0 and 0.5-1.5 

months)

Up to 88 days (2.9 months) for 

aminocyclopyrachlor and INLXT69. Residues of 

aminocyclopyrachlor-methyl were 

unstable; however, 

biotransformation to 

aminocyclopyrachlor accounted for 

nearly all loss on storage.

Liver 0 and 28-29 days Up to 147 days (4.8 months) for 

aminocyclopyrachlor and INLXT69. Residues of 

aminocyclopyrachlor-methyl were 

unstable; however, 

biotransformation to 

aminocyclopyrachlor accounted for 

nearly all loss on storage.

Conclusions. Acceptable supporting storage stability data have been submitted for milk and 

bovine tissues and hay. No additional storage stability data are required to support the submitted 

cattle feeding study.
Aminocyclopyrachlor Summary of Analytical Chemistry and Residue Data DP#: D387442

Page 24 of 43

860.1400 Water, Fish, and Irrigated Crops

There are no proposed uses that are relevant to this guideline topic.

860.1460 Food Handling

There are no proposed uses that are relevant to this guideline topic.

860.1480 Meat, Milk, Poultry, and Eggs

DER Reference: 48363401.DE1

The livestock feedstuffs associated with PP#0F7817 are grass forage and hay; these commodities 

are fed to beef and dairy cattle but are not fed to poultry or swine. The dietary burdens of 

aminocyclopyrachlor to cattle, based on reasonably balanced diets, are presented in Table 6. The 

maximum reasonable dietary burden for cattle is 90 ppm. 

Table 6. Calculation of Dietary Burdens of Aminocyclopyrachlor Residues to Livestock.

Feedstuff Type1 % Dry 

Matter2 % Diet2 Highest Average Field Trial (ppm)4

Dietary Contribution 

(ppm) 3

Beef Cattle

Grass hay R 88 15 117 19.9

CC not registered CC -- 80 -- --

PC not registered PC -- 5 -- --

TOTAL BURDEN -- -- 100 -- 19.9

Dairy Cattle

Grass forage R 25 45 50 90

CC not registered R -- 45 -- --

PC not registered CC -- 10 -- --

TOTAL BURDEN -- -- 100 -- 90

1

 R: Roughage; CC: Carbohydrate concentrate; PC: Protein concentrate.

2

 OPPTS 860.1000 Table 1 Feedstuffs (June 2008). 

3

 Contribution = ([tolerance /% DM] X % diet) for beef and dairy cattle; contribution = ([tolerance] X % diet) for 

poultry and swine.

4

 calculated as parent equivalents

DuPont submitted a cattle feeding study with aminocylopyrachlor-methyl (DPX-KJM44). DPXKJM44 is the methyl ester of aminocyclopyrachlor (DPX-MAT28). In the study, four groups of 

dairy cows (3 cows/group; Groups 1-4) were dosed orally once a day with gelatin capsules 

containing aminocyclopyrachlor-methyl (DPX-KJM44) at target doses of 1.8, 3.6, 10.8, and 36 

mg/kg bw/day for 28 consecutive days. Based on the average feed consumption, the actual mean 

daily dose levels were equivalent to 73.3, 160, 455, and 1595 ppm in the diet (dry-weight basis). 

The dosing levels correspond to ~0.8x, 1.8x, 5.1x, and 17.7x the maximum reasonable dietary 

burden to cattle based on the proposed use on grass. An additional group of two cows (Group 5) 

was dosed at 1594 ppm for 28 days, to obtain depuration data. One control cow received 

capsules containing no aminocyclopyrachlor-methyl (Group 6). The study was conducted by 

Charles River Laboratories (Tranent, Edinburgh, Scotland) 
Aminocyclopyrachlor Summary of Analytical Chemistry and Residue Data DP#: D387442

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Cows were milked twice daily. For each cow, milk samples from the afternoon sampling were 

combined with milk samples from the next morning sampling to produce a daily sample. 

Samples of milk from Study Days -1, 1, 3, 5, 7, 10, 14, 17, 21, 24, and 28 from all dose groups 

were analyzed. Milk collected on Days 14 and 21 was used for preparation of skim milk and 

cream samples. Milk samples were collected from the depuration group (Group 5) on Study 

Days 24 and 28 during the dosing period and on Depuration Days 1, 3, 5, 10, 14, and 16 postdosing; only milk from Depuration Days 1, 3, 5, and 7 was analyzed. Skim milk and cream 

samples were prepared from milk collected on Depuration Days 3 and 10 post-dosing. Control 

and treated cows except those in the depuration study were sacrificed ~22-24 hours after the final 

dose on Study Day 28. Samples of liver, kidney, fat (omental, renal, and subcutaneous), and 

muscle (loin, flank, and hind leg) were collected from each cow.

Milk and tissue samples were analyzed for residues of aminocyclopyrachlor-methyl, 

aminocyclopyrachlor, and metabolite IN-LXT69 using an acceptable method, and the study is 

supported by adequate storage stability data. The method LOQ is 0.01 ppm for all analytes in 

milk and tissues.

All samples were stored frozen (approximately -20 oC) prior to extraction for analysis, except for 

samples of liver and kidney, which were generally processed fresh following sacrifice, due to 

storage stability issues for analysis of aminocyclopyrachlor-methyl. The maximum storage 

durations from collection to extraction were 65 days for milk, 30 days for skim milk, 59 days for 

cream, 44 days for muscle, and 36 days for fat. Liver and kidney samples were generally 

extracted on the day of collection with the exception of selected repeat analysis samples. 

Adequate storage stability data are available to support the storage conditions and durations of 

samples from the cattle feeding study. 

Residues of aminocyclopyrachlor-methyl and IN-LXT69 were below the LOQ in all samples of 

milk, skim milk, cream, muscle, liver, kidney, and fat at all dose levels, except that quantifiable 

residues of 0.014 ppm aminocyclopyrachlor-methyl were observed in liver from one cow at the 

73.3-ppm dose level. Quantifiable residues of aminocyclopyrachlor were observed in milk at the 

160-, 455-, and 1595-ppm dose levels, although residues at the 160-ppm dose level were 

generally near or below the LOQ on all sampling days. Quantifiable residues were observed in 

skim milk and cream beginning at the 160-ppm dose level for skim milk and the 455-ppm dose 

level for cream. In tissues, quantifiable residues of aminocyclopyrachlor were observed in liver, 

kidney, and fat at all dose levels and in muscle beginning at the 160- and 1595-ppm dose levels. 

In tissues, residues were highest in kidney, followed by fat, liver, and muscle. 

Residues of aminocyclopyrachlor in milk appeared to reach a plateau by Day 7 for the 455-ppm 

dose level but continued to increase at the 1595-ppm dose level through study Day 28. We note 

that OCSPP 860.1480 specifies that dosing should continue until residues plateau in milk if they 

have not done so in 28 days. Residues of aminocyclopyrachlor in milk (beginning from Day 7) 

were <0.01, <0.01-0.012, 0.016-0.026, and 0.040-0.10 ppm following dosing at 73.3, 16, 455,

and 1595 ppm, and combined residues of aminocyclopyrachlor and aminocyclopyrachlor-methyl 

were <0.02, <0.02-<0.022, <0.026-<0.036, and <0.05-<0.11 ppm at the respective dose levels. 

There was no evidence of preferential transfer of residues to skim milk or cream; in general, 
Aminocyclopyrachlor Summary of Analytical Chemistry and Residue Data DP#: D387442

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residues of aminocyclopyrachlor were slightly lower in cream at all dose levels with quantifiable 

residues. Residues in skim milk and cream (Study Days 14 and 21), respectively, were <0.01 

(both), <0.01-0.013 and <0.01, 0.015-0.023 and <0.01-0.015, and 0.044-0.098 and 0.017-0.046 

ppm at the 73.3-, 16-, 455-, and 1595-ppm dose levels; combined residues of 

aminocyclopyrachlor and aminocyclopyrachlor-methyl in skim milk and cream, respectively, 

were <0.02 (both), <0.02-<0.023 and <0.02, <0.025-<0.033 and <0.02-<0.025, and <0.054 and 

<0.108 and <0.027-<0.056 ppm at the respective dose levels. 

In kidney, residues of aminocyclopyrachlor were 0.092-0.17, 0.23-0.40, 0.20-0.54, and 0.68-1.4 

ppm at the 73.3-, 16-, 455-, and 1595-ppm dose levels, and combined residues of 

aminocyclopyrachlor and aminocyclopyrachlor-methyl were <0.10-<0.18, <0.24-<0.41, <0.21-

<0.55, and <0.69-<1.41 ppm. In fat, residues of aminocyclopyrachlor were <0.01-0.015, <0.01-

0.040, 0.029-0.12, and 0.025-0.74 ppm at the 73.3-, 16-, 455-, and 1595-ppm dose levels, and 

combined residues of aminocyclopyrachlor and aminocyclopyrachlor-methyl were <0.02-

<0.025, <0.02-<0.050, <0.039-<0.13, and <0.035-<0.75 ppm. In liver residues of 

aminocyclopyrachlor were <0.01-0.082, 0.020-0.064, 0.025-0.075, and 0.088-0.11 ppm at the 

73.3-, 16-, 455-, and 1595-ppm dose levels, and combined residues of aminocyclopyrachlor and 

aminocyclopyrachlor-methyl were <0.02-<0.092, <0.03-<0.074, <0.035-<0.085, and <0.098-

<0.12 ppm. In muscle, residues of aminocyclopyrachlor were <0.01, <0.01-0.012, <0.01, and 

0.021-0.10 at the 73.3-, 16-, 455-, and 1595-ppm dose levels, and combined residues of 

aminocyclopyrachlor and aminocyclopyrachlor-methyl were <0.02, <0.02-0.022, <0.02, and 

<0.031-<0.11 ppm at the respective dose levels. 

Following cessation of dosing, residues in milk and tissues rapidly declined in the depuration 

group dosed at 1594 ppm for 28 days. Residues of aminocyclopyrachlor-methyl and IN-LXT69 

were not detected above the LOQ (<0.01 ppm) in any milk, skim milk, cream, or tissue samples. 

Residues of aminocyclopyrachlor were detected above the LOQ in one milk sample (0.017 ppm) 

on Depuration Day 1 and dropped below the LOQ by Depuration Day 3. Residues of 

aminocyclopyrachlor were detected above the LOQ in the muscle (0.019 ppm) and fat (0.030 

ppm) of the cow sacrificed on Depuration day 15. For the cow sacrificed on Depuration day 17, 

the aminocyclopyrachlor residues were not detected in the muscle sample and increased to 0.056 

ppm in the fat sample.

Conclusions. The submitted cattle feeding study is acceptable for purposes of this petition. 

Residues in milk did not reach a plateau at the highest dosing level (1595 ppm; 17.7x) in the 

submitted study; however, because residues plateaued at 7 days at the 455-ppm dose level (5.1x) 

and were generally near the LOQ at the 160-ppm dose level (1.8x), HED believes the study is 

adequate to support the proposed use on grass only. Should other uses be proposed which result 

in an increase in the dietary burden for cattle, additional data may be required. 

Samples were analyzed for aminocyclopyrachlor, aminocyclopyrachlor-methyl, and IN-LXT69 

using acceptable methods, and the study is supported by adequate storage stability data. 

Based on the submitted data, HED has concluded that tolerances are needed for milk and the 

tissues of cattle, goat, horse, and sheep. Tolerances are not needed for milk fat because residues 

did not concentrate in cream.
Aminocyclopyrachlor Summary of Analytical Chemistry and Residue Data DP#: D387442

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If the residues observed at various dosing levels are adjusted to a 1x feeding level for dairy cattle 

(see Table 7), maximum expected combined residues would be 0.02 ppm in milk, 0.22 ppm in 

kidney, 0.04 ppm in fat, 0.10 ppm in liver, and 0.02 ppm in muscle. Based on these data, 

tolerances are needed for meat byproducts at 0.30 ppm, for fat at 0.05 ppm, and for muscle at 

0.02 ppm. The data indicate that a tolerance of 0.02 ppm (equivalent to the combined LOQs for 

aminocyclopyrachlor and aminocyclopyrachlor-methyl) would be appropriate for milk.

Table 7. Summary of Data from Cattle Feeding Study with Aminocyclopyrachlor-methyl.

Matrix

Maximum combined residues of 

aminocyclopyrachlor and 

aminocyclopyrachlor-methyl at each 

dosing level1

Residues adjusted to 1x feeding level for 

dairy cattle2

73.3 160 455 1595 0.8x 1.8x 5.1x 18x

Milk (Days 7-28) -- <0.022 <0.036 <0.11 -- 0.01 0.01 0.01

Skim milk -- <0.023 <0.033 <0.11 -- 0.01 0.01 0.01

Cream -- -- <0.025 <0.056 -- -- 0.01 0.01

Kidney <0.18 <0.41 <0.55 <1.41 0.23 0.23 0.11 0.08

Fat <0.025 <0.050 <0.13 <0.75 0.03 0.03 0.03 0.04

Liver <0.092 <0.074 <0.085 <0.12 0.12 0.04 0.02 0.01

Muscle -- -- -- <0.11 -- -- -- 0.01

1

 The LOQ (0.01 ppm) was used for residues reported as ND or below the LOQ. For purposes of this calculation 

only, where maximum residues were below the LOQ for both analytes, residues are indicated by --.

2

 The dose rate factors calculated above based on actual dosing levels in calculations.

Because there are no poultry feedstuffs associated with the proposed use on grasses, data 

requirements for a poultry feeding study are not relevant to this tolerance petition. 

860.1500 Crop Field Trials

DER Reference: 48333630.DER

DuPont has submitted field trial data reflecting use of the potassium salt and methyl ester 

formulations on grass forage and hay in support of the proposed use of aminocyclopyrachlor on 

pasture and rangeland grasses. The results from these field trials are discussed below and the 

residue data are summarized in Table 8.
Aminocyclopyrachlor Summary of Analytical Chemistry and Residue Data DP#: D387442

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Table 8. Summary of Residue Data from Grass Crop Field Trials with the Methyl Ester and Potassium Salt 

Formulations of Aminocyclopyrachlor.

Commodity TRT 

Plot 

#

1

EP2 Total Applic. 

Rate3,

lb ai or ae/A

(g ai or ae/ha)

PHI

(days)

Residue Levels

(ppm)

n Min. Max. HAFT4 Median Mean Std. 

Dev.

PASTURE AND RANGELAND GRASSES: proposed use = 0.281 lb ai/A total application rate, 0-day PHI

Aminocyclopyrachlor-methyl

Grass, 

forage 1

80% 

WG

0.274-0.299

(308-335) 0 44 7.7 47 47 22 23 10

2

2 lb/gal 

SL

0.275-0.285

(308-319) 0 12 0.014 0.15 0.15 0.031 0.050 0.047

3

80% 

WG

0.270-0.280

(303/314) 0 6 9.5 14 14 11 11 1.9

Grass,

hay 1

80% 

WG

0.274-0.299

(308-335) 0 44 13 108 103 35 38 20

2

2 lb/gal 

SL

0.275-0.285

(308-319) 0 12 0.061 0.89 0.73 0.15 0.24 0.25

3

80% 

WG

0.270-0.280

(303/314) 0 6 19 31 27 22 23 4.5

Aminocyclopyrachlor

Grass, 

forage 1

80% 

WG

0.274-0.299

(308-335) 0 44 0.76 14 13 2.2 3.2 2.7

2

2 lb/gal 

SL

0.275-0.285

(308-319) 0 12 12 41 39 20 23 8.9

3

80% 

WG

0.270-0.280

(303/314) 0 6 0.43 0.84 0.75 0.65 0.66 0.15

Grass,

hay 1

80% 

WG

0.274-0.299

(308-335) 0 44 2.4 80 79 16 18 16

2

2 lb/gal 

SL

0.275-0.285

(308-319) 0 12 29 58 49 41 41 8.3

3

80% 

WG

0.270-0.280

(303/314) 0 6 1.1 14 12 2.4 5.2 5.5

Combined residues of aminocyclopyrachlor + aminocyclopyrachlor-methyl

Grass, 

forage 1

80% 

WG

0.274-0.299

(308-335) 0 44 8.7 54 53 25 26 12

2

2 lb/gal 

SL

0.275-0.285

(308-319) 0 12 12 41 39 20 23 8.9

3

80% 

WG

0.270-0.280

(303/314) 0 6 10 15 14 12 12 1.9

Grass,

hay 1

80% 

WG

0.274-0.299

(308-335) 0 44 28 133 129 50 57 27

2

2 lb/gal 

SL

0.275-0.285

(308-319) 0 12 29 59 49 41 41 8.5

3

80% 

WG

0.270-0.280

(303/314) 0 6 20 45 39 25 28 9.6

1

 1= 80% WG formulation of aminocyclopyrachlor-methyl, normal application volume; 2 = 2 lb/gal SL formulation of 

aminocyclopyrachlor; and 3 = 80% WG formulation of aminocyclopyrachlor-methyl, low application volume.

2 80% WG = WG formulation of aminocyclopyrachlor-methyl and 2 lb/gal SL = SL formulation of aminocyclopyrachlor.
Aminocyclopyrachlor Summary of Analytical Chemistry and Residue Data DP#: D387442

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3

 Rates reflect lb ae or ai/A aminocyclopyrachlor; refer to the DER for 4833630 for comparison of rates with ai 

aminocyclopyrachlor-methyl.

4

 HAFT = Highest Average Field Trial result.

DuPont has submitted field trial data for aminocyclopyrachlor (DPX-MAT28), 

aminocyclopyrachlor-methyl (DPX-KJM44), and metabolites IN-LXT69, IN-QFH57, and INQGC48 in/on grass forage and hay from pastures and rangelands in the U.S. and Canada. 

Twenty-two field trials were conducted in the U.S. and Canada in Zones 1 (PA and PE, 3 trials), 

2 (NJ, 1 trial), 5 (IA, MB, MO, NE, and ON, 6 trials), 6 (OK and TX, 3 trials), 7 (ND and SD, 2 

trials), 8 (KS, 1 trial), and 14 (AB, MB, and SK, 6 trials) during the 2008 and 2009 growing 

seasons. 

Each field trial included one control plot and one treated plot. Treated plots received a single 

foliar broadcast application of an 80% WG formulation of DPX-KJM44 (methyl ester) at a target 

rate of 0.300 lb ai/A (336 g ai/ha), equivalent to 0.281 lb ae/A (315 g ae/ha) 

aminocyclopyrachlor. Actual application rates were 0.293-0.318 lb ai/A (328-357 g ai/ha), 

equivalent to 0.274-0.299 lb ae/A (308-335 g ae/ha), with spray volumes of 10-30 gal/A. 

Additional side-by-side trials were conducted at selected sites as follows. Six trials included a 

second treated plot which received a single foliar broadcast application of a 2 lb/gal (240 g/L) SL 

formulation of aminocyclopyrachlor at a target rate of 0.281 lb ai/A (315 g ai/ha). Actual 

application rates were 0.275-0.285 lb ai/A (308-319 g ai/ha) with spray volumes of 10-30 gal/A. 

Three trials included a second treated plot which received a single foliar broadcast application of 

the 80% WG formulation of aminocyclopyrachlor-methyl at a target rate of 0.300 lb ai/A (336 g 

ai/ha), equivalent to 0.281 lb ae/A (315 g ae/ha) DPX-MAT 28, in a low volume application. 

Actual application rates were 0.288-0.299 lb ai/A (323-335 g ai/ha), equivalent to 0.270-0.280 lb 

ae/A (303-314 g ae/ha), in a spray volume of 1 gal/A. The application rates used in the study 

correspond to ~1-1.1x the maximum seasonal application rate to grasses. An adjuvant 

(organosilicone, nonionic surfactant, or methylated seed oil) was added to the spray mixture for 

all of the applications.

Single control and duplicate treated samples of grass forage and hay were harvested from each 

plot at a PHI of 0 days (approximately 4 hours after application). At two of the trials, four 

additional sampling intervals were scheduled at PHIs of 3, 7, 14, and 21 days after application to 

assess residue decline. Samples of hay were allowed to dry in the field for 0-28 days after 

harvest. 

The results of the grass field trials for residues of aminocyclopyrachlor and 

aminocyclopyrachlor-methyl are summarized in Table 8. Following a single foliar broadcast 

application of the 80% WG formulation of aminocyclopyrachlor-methyl WG (at normal or low 

spray volume) or the 2 lb/gal SL formulation of aminocyclopyrachlor at target rates of ~0.281 ae 

ai/A and a PHI of 0 days, the major residues found in grass forage and hay were 

aminocyclopyrachlor-methyl and aminocyclopyrachlor. Quantifiable residues of metabolite INLXT69 were observed in/on grass forage and hay at up to 0.035 ppm in/on forage and 0.11 ppm 

in/on hay; residues of IN-QFH57 or IN-QGC48 were below the LOQ in/on all samples. 

Comparison of the results for the side-by-side trials reflecting normal and low spray volumes for 

the 80% WG formulation of aminocyclopyrachlor-methyl indicated that combined residues of 

aminocyclopyrachlor and aminocyclopyrachlor-methyl following application in normal spray 
Aminocyclopyrachlor Summary of Analytical Chemistry and Residue Data DP#: D387442

Page 30 of 43

volumes were higher in/on grass forage in two of three trials and higher in/on grass hay in all 

three trials. Comparison of the results for the side-by-side trials reflecting the 80% WG 

formulation of aminocyclopyrachlor-methyl and the 2 lb/gal SL formulation of 

aminocyclopyrachlor at a target rate of 0.281 lb ae/A indicated that combined residues of 

aminocyclopyrachlor and aminocyclopyrachlor-methyl were generally slightly higher following 

application of the aminocyclopyrachlor formulation.

In the residue decline trials combined residues of aminocyclopyrachlor-methyl and 

aminocyclopyrachlor declined with increasing PHI in grass forage and hay. Residues of INLXT69 were near or below the LOQ in most trials; where quantifiable residues were observed, 

residues declined with increasing harvest interval. 

Conclusions: The grass field trial data for aminocyclopyrachlor are adequate to fulfill data 

requirements. The number and locations of field trials are in accordance with the requirements 

of OCSPP Guideline 860.1500 for grasses, and the use pattern of the field trials adequately 

reflects the proposed use pattern.

Grass forage and hay samples were analyzed for residues of aminocyclopyrachlor, 

aminocyclopyrachlor-methyl, and metabolites IN-LXT69, IN-QFH57, and IN-QGC48 by 

LC/MS/MS using an adequate method, and the study is supported by adequate storage stability 

data. The method LOQ is 0.01 ppm for all analytes in grass forage and hay.

The available field trial data will support tolerances of 80 ppm for grass forage and 200 ppm for 

grass hay. The tolerance calculations are presented in Appendix I.

The analytical methods submitted under the subject action do not provide for conversion of 

residues of aminocyclopyrachlor-methyl to stoichiometric equivalents of aminocyclopyrachlor 

but the residue data presented herein does reflect correction to stoichiometric equivalents. The 

conversion factor, based on molecular weights (MWs) of 213.6 for aminocyclopyrachlor and 

227.6 for aminocyclopyrachlor-methyl is 0.93849. 

As noted above, comparison of the results for the side-by-side trials reflecting application of the 

80% WG formulation of aminocyclopyrachlor-methyl and the 2 lb/gal SL formulation of 

aminocyclopyrachlor indicated that combined residues of aminocyclopyrachlor and 

aminocyclopyrachlor-methyl were generally slightly higher following application of the 

aminocyclopyrachlor formulation. When the trial results for each set of trials are compared in 

terms of ppm, the results are:

For forage: 5 trials with higher residues following app of the SL (residues 1.2x higher) 

and 1 trial with higher residues following app of the WG (1.4x): 

For hay: 3 trials with higher residues following app of the SL (1.1-1.3x) and 3 trials with 

higher residues following app of the WG (1.1-1.4x). 

HED does not believe these differences are significant enough to warrant additional trials for the 

SL formulation.
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860.1520 Processed Food and Feed

HED does not require residue data for any processed commodities associated with grass. 

Therefore, data requirements for processed food and feed are not relevant to this tolerance 

petition.

860.1650 Submittal of Analytical Reference Standards

An analytical standard for aminocyclopyrachlor acid (expiration 2013) is currently available in 

the EPA National Pesticide Standards Repository (personal communication between T. Cole, 

ACB, and Versar, 5/4/11); however, a standard for aminocyclopyrachlor-methyl is not currently 

available. An analytical reference standard for aminocyclopyrachlor-methyl must be supplied 

and supplies replenished as requested by the Repository. The reference standard should be sent 

to the Analytical Chemistry Lab, which is located at Fort Meade, to the attention of either 

Theresa Cole or Thuy Nguyen at the following address:

USEPA

National Pesticide Standards Repository/Analytical Chemistry Branch/OPP

701 Mapes Road

Fort George G. Meade, MD 20755-5350

(Note that the mail will be returned if the extended zip code is not used.)

860.1850 Confined Accumulation in Rotational Crops

DER Reference: 48333619.DER

E. I. du Pont de Nemours and Company has submitted a confined rotational crop study with [2-

pyrimidinyl14C]aminocyclopyrachlor-methyl (specific activity 1.64 MBq/mg). The radiolabeled 

test substance was formulated as a 25% WP and applied to sandy loam soil as a single 

application at 0.067 lb ai/A (75 g ai/ha), equivalent to 0.063 lb ae/A (70 g ae/ha) 

aminocyclopyrachlor, or 0.329 lb ai/A (369 g ai/ha), equivalent to 0.309 lb ae/A (346 g ae/ha) 

aminocyclopyrachlor. The application rates correspond to ~0.2x and ~1.2x the maximum 

seasonal application rate for grasses. Rotational crops of cabbage, turnip, and field corn were 

planted at PBIs of 30, 60, 120, and 300 days after soil treatment (DAT) for cabbage and turnips, 

and 15, 120, and 300 DAT for corn following soil treatment at 0.067 lb ai/A, and at a PBI of 300 

DAT for all crops following application at 0.329 lb ai/A. Samples of immature and mature 

cabbage and turnips (roots and tops), and corn (forage, stover, cobs, and grain) were collected at 

appropriate harvest intervals. The in-life and analytical phases of the study were conducted by 

Charles River Laboratories (Tranent, Edinburgh, Scotland).

Following application at 0.067 lb ai/A, TRR accumulated at >0.01 ppm in: 30- and 60-DAT 

immature and mature cabbage (0.013-0.027 ppm); 30-, 60-, 120-, and 300-DAT immature turnip 

tops (0.012-0.029 ppm); 60- and 120-DAT mature turnip tops (0.010-0.011 ppm), 30-day 

immature turnip roots (0.010 ppm); and 15-, 120- and 300-DAT corn forage (0.011-0.091 ppm), 

stover (0.023-0.149 ppm), and grain (0.012-0.067 ppm); and 15-DAT corn cobs (0.024 ppm). 

Following application at 0.329 lb ai/A, TRR accumulated at >0.01 ppm in immature and mature 
Aminocyclopyrachlor Summary of Analytical Chemistry and Residue Data DP#: D387442

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cabbage (0.011-0.012 ppm), immature turnip tops (0.085 ppm), and corn forage, stover, cobs, 

and grain (0.246, 0.262, 0.012, and 0.085 ppm, respectively), planted 300 DAT. These matrices 

were subjected to further extraction and characterization procedures.

Approximately 57.3-100% TRR was extracted from rotational crop matrices using ACN:water. 

Nonextractable residues from the 15-DAT corn forage, stover, and grain and 300-DAT turnip 

tops and corn stover following application at 0.067 lb ai/A, and from 300-DAT turnip tops, and 

corn forage, stover, and grain following application at 0.329 lb ai/A were subjected to enzyme 

hydrolysis with α-amylase (50 oC for 72 hours) followed by a combination of amyloglucosidase 

and cellulase (50 oC for 48 hours) which released an additional 6.9-16.3 % TRR and 3.4-13.9% 

TRR, respectively. Subsequent hydrolysis with 0.01 N NaOH (60

oC for 6 hours) and 1 N HCl 

(60

oC for 6 hours) released an additional 1.1-3.4% TRR and 0.8-2.4% TRR, respectively. 

Remaining nonextractable residues following extraction and hydrolysis procedures were ≤0.009 

ppm in all matrices. These procedures adequately extracted the majority of the residues from 

rotational crop matrices. Extraction results were normalized; therefore, accountabilities were 

100%.

Because samples were stored frocen for ≤6 months prior to analysis, supporting storage stability 

data are not required. Extracts were stored for 7-163 days prior to analysis. Extracts of 30-DAT 

immature cabbage, 60-DAT immature turnip tops, and 15-DAT corn stover were reanalyzed 

following frozen storage for ~14 months to confirm the stability of the metabolite profile. 

Residues were identified and quantitated in the ACN/water extracts and hydrolysates by HPLC. 

Only three residue components were identified in rotational crops: aminocyclopyrachlor, 

aminocyclopyrachlor-methyl, and IN-LXT69. aminocyclopyrachlor was the major identified 

residue and was detected in all crops (40.5-96.0% TRR). Aminocyclopyrachlor-methyl was a 

major metabolite in 30- and 60-DAT turnip tops (16-18% TRR) and 15-DAT corn forage and 

stover (9-10% TRR), but was a minor residue component in remaining matrices (≤5.6% TRR). 

IN-LXT69 was identified at low levels in 15-DAT corn stover and 300-DAT corn forage (≤1.9% 

TRR).

Aminocyclopyrachlor accounted for accounted for 83.1% and 80.1% TRR (0.014 and 0.021 

ppm) in 30- and 60-DAT immature cabbage and for 60.0% and 60.6% TRR (0.014 and 0.008 

ppm) in 30- and 60-DAT mature cabbage following application at 0.067 lb ai/A, and for 54.3% 

TRR (0.006 ppm ) and 83.0% TRR (0.010 ppm) in 300-DAT immature and mature cabbage 

following application at 0.329 lb ai/A. In turnips, aminocyclopyrachlor accounted for 96.0% 

TRR (0.010 ppm) in 30-DAT immature roots, for 57.3-83.1% TRR (0.010-0.017 ppm) in 30-, 

60-, 120-, and 300-DAT immature tops following application at 0.067 lb ai/A, and for 40.5-

59.3% TRR (0.004-0.007 ppm) in 60- and 120-DAT mature turnip tops; residues of 

aminocyclopyrachlor were 85.6% TRR (0.072 ppm) in 300-DAT immature turnip tops following 

application at 0.329 lb ai/A.

In corn, aminocyclopyrachlor accounted for 62.7-71.4% TRR (0.007-0.176 ppm) in 15-, 120-, 

and 300-DAT forage following application at 0.067 and/or 0.329 lb ai/A. In stover, 

aminocyclopyrachlor accounted for 71.9% TRR (0.106 ppm) declining to 45.9% TRR (0.026 

ppm) in 15-, 120-, and 300-DAT samples following application at 0.067 lb ai/A, and for 58.0% 
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TRR (0.151 ppm) in 300-DAT samples following application at 0.329 lb ai/A. Residues of 

DPX-MAT 28 in cobs accounted for 58.9% and 43.8% TRR (0.014 and 0.005 ppm) in 15-DAT 

and 300-DAT samples harvested following application at 0.067 and 0.329 lb ai/A, respectively. 

Residues in grain were 70.9-76.0% TRR (0.009-0.064 ppm) in 15-, 120-, and 300-DAT samples 

following application at 0.067 and/or 0.329 lb ai/A. 

Aminocyclopyrachlor-methyl was identified in immature and mature 30-DAT cabbage, mature 

60-DAT cabbage, and immature 300-DAT cabbage following application at 0.329 lb ai/A, and 

immature turnip roots at 3.3-4.6% TRR. In turnip tops, residues accounted for 15.9-17.8% TRR 

(0.002-0.003 ppm) in 30- and 60-DAT immature and mature tops, and for 5.6% TRR (0.001 

ppm) in 120-DAT immature tops. In 15-DAT corn forage and stover, aminocyclopyrachlormethyl accounted for 9.1-10.0% TRR (0.009-0.013 ppm); residues were identified at ≤5.4% 

TRR in 15-DAT grain and cobs, and 300-DAT forage and/or stover and grain following 

application at 0.067 and/or 0.329 lb ai/A. Remaining residues were characterized as minor 

unknowns, including an apolar unknown and multicomponent minor unknowns, which 

accounted for 5.0-6.9% TRR (0.012-0.018 ppm) and 16.3-25.3% TRR (0.038-0.064 ppm), 

respectively, in 300-DAT corn forage and stover following application at 0.329 ppm, and 

together accounted for ≤0.014 ppm in all remaining matrices. 

Based on the results of the study, the petitioner proposed that metabolism of 

aminocyclopyrachlor-methyl in rotational crops involves the de-esterification of 

aminocyclopyrachlor-methyl to form the carboxylic acid, aminocyclopyrachlor. 

Aminocyclopyrachlor undergoes decarboxylation (to a much lesser extent) to form IN-LXT69. 

Succeeding crops grown in soils treated with aminocyclopyrachlor-methyl would be exposed 

primarily to aminocyclopyrachlor, the principal soil degradation product.

Conclusions. The confined rotational crop study is acceptable. HED concludes that the nature 

of the residue in rotational crops is adequately understood and that metabolism in rotational 

crops is similar to that in primary crops. The study results indicate that residues of 

aminocyclopyrachlor may exceed the 0.01-ppm trigger value in turnip tops and corn forage, 

stover, and grain at a 300-day PBI following application of aminocyclopyrachlor-methyl at ~1x

the maximum proposed seasonal application rate to grass. Based on the study results limited 

rotational crop field trials are required for aminocyclopyrachlor to establish PBIs and/or 

tolerances for rotational crops.

Pending submission of the required limited field rotational crop trials, the labels must be revised 

to prohibit rotation to any crop other than grasses following application of aminocyclopyrachlor 

or aminocyclopyrachlor-methyl.

860.1900 Field Accumulation in Rotational Crops

Based on the results of the confined rotational crop study, limited rotational crop field trials are 

required for aminocyclopyrachlor to establish PBIs and/or tolerances for rotational crops.
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Pending submission of the required limited field rotational crop trials, the labels must be revised 

to prohibit rotation to any crop other than grasses following application of aminocyclopyrachlor 

or aminocyclopyrachlor-methyl.

860.1550 Proposed Tolerances

DuPont has proposed that tolerances for aminocyclopyrachlor residues of concern in crop and 

livestock commodities be expressed in terms of combined residues of aminocyclopyrachlor and 

aminocyclopyrachlor-methyl. HED has determined that the proposed tolerance expression as 

stated in Section F of the petition is appropriate:

Tolerances are established for residues of the herbicide aminocyclopyrachlor, including 

its metabolites and degradates, in or on the commodities in the table below. Compliance 

with the tolerance levels specified below is to be determined by measuring only the sum 

of aminocyclopyrachlor, 6-amino-5-chloro-2-cyclopropyl-4-pyrimidinecarboxylic acid, 

and aminocyclopyrachlor methyl ester, methyl 6-amino-5-chloro-2-cyclopropyl-4-

pyrimidinecarboxylate, calculated as the stoichiometric equivalent of 

aminocyclopyrachlor.

The analytical methods submitted under the subject action do not provide for conversion of 

residues of aminocyclopyrachlor-methyl to stoichiometric equivalents of aminocyclopyrachlor

but the residue data presented herein does reflect correction to stoichiometric equivalents. The 

conversion factor, based on molecular weights (MWs) of 213.6 for aminocyclopyrachlor and 

227.6 for aminocyclopyrachlor-methyl is 0.93849. 

Adequate crop field trial data reflecting the proposed use patterns were submitted for purposes of 

establishing tolerances on grass forage and hay. The OECD MRL Calculator (March 2011 

version) was utilized in determining the appropriate tolerance levels. The proposed tolerances of 

65 and 125 ppm for grass forage and hay are too low. The tolerances should be established at 80 

and 200 ppm, respectively. 

An acceptable feeding study has been submitted in support of the proposed use on grasses. The 

data indicate that tolerances are needed for milk, and the tissues of cattle, goat, horse, and sheep. 

The proposed tolerance in milk is too high, and the proposed tolerances for liver and meat 

byproducts, except liver are not consistent with Agency policy. Livestock commodities, 

individual tolerances in cow, goat, horse, and sheep should be established for meat byproducts at 

0.30 ppm, fat at 0.05 ppm, and meat at 0.02 ppm. The tolerance for milk should be established at 

0.02 ppm. The tolerances for liver and meat byproducts, except liver should be removed. 

There are currently no established Codex, Canadian, or Mexican maximum residue limits 

(MRLs) for aminocyclopyrachlor; therefore, there are no issues of harmonization. An 

International Residue Limit Status Sheet (IRLS) follows the references in this document.

The proposed and recommended tolerances for aminocyclopyrachlor as a result of the subject 

action are presented in Table 9. The proposed tolerances should be revised to reflect the 

recommended commodities and tolerance levels specified in Table 9.
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Table 9. Tolerance Summary for Aminocyclopyrachlor.

Commodity Proposed 

Tolerance

(ppm)

Recommended 

Tolerance

(ppm)

Comments

Cattle, fat 0.07 0.05

Cattle, liver 0.06 Not required Based on current Agency policy a separate 

lower tolerance for liver is not appropriate

Cattle, meat 0.02 0.02

Cattle, meat byproducts, 

except liver 

0.4 Not required

Cattle, meat byproducts -- 0.30 Based on current Agency policy, the meat 

byproducts tolerance should be based on the 

highest residue between liver, kidney, and fat.

Goat, fat 0.07 0.05

Goat, liver 0.06 Not required See comment for cattle, liver

Goat, meat 0.02 0.02

Goat, meat byproducts, 

except liver 

0.4 Not required

Goat, meat byproducts -- 0.30 See comment for cattle, meat byproducts

Grass, forage 65 80*

Grass, hay 125 200*

Horse, fat 0.07 0.05

Horse, liver 0.06 Not required See comment for cattle, liver

Horse, meat 0.02 0.02

Horse, meat byproducts, 

except liver 

0.4 Not required

Horse, meat byproducts -- 0.30 See comment for cattle, meat byproducts

Milk 0.035 0.02

Sheep, fat 0.07 0.05

Sheep, liver 0.06 Not required See comment for cattle, liver

Sheep, meat 0.02 0.02

Sheep, meat byproducts, 

except liver 

0.4 Not required

Sheep, meat byproducts -- 0.30 See comment for cattle, meat byproducts

*Based on OECD MRL Calculator

References

DP Number: 369057

Subject: Aminocyclopyrachlor: Human Health Risk Assessment for Proposed Uses as an 

Herbicide.

From: J. Ryman, J. Miller, and T. Morton

To: J. Tompkins and M. Ondish

Dated: 3/17/10

MRID(s): None
Aminocyclopyrachlor Summary of Analytical Chemistry and Residue Data DP#: D387442

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DP Number: 393619

Subject: Aminocyclopyrachlor. Report of the Residues of Concern Knowledgebase 

Subcommittee (ROCKS). 

From: Ideliz Negrón-Encarnación

To: Aminocyclopyrachlor Risk Assessment Team

Dated: 9/22/11

MRID(s): None
Aminocyclopyrachlor Summary of Analytical Chemistry and Residue Data DP#: D387442

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International Residue Limits 

Aminocyclopyrachlor (PC Code 288008; 5/05/11)

Summary of US and International Tolerances and Maximum Residue Limits 

Residue Definition: 

US Canada Mexico2 Codex3

40 CFR 180.###:

Plant and livestock: Aminocyclopyrachlor, 6-amino5-chloro-2-cyclopropyl-4-pyrimidinecarboxylic acid, 

and aminocyclopyrachlor methyl ester, methyl 6-

amino-5-chloro-2-cyclopropyl-4-

pyrimidinecarboxylate, calculated as the 

stoichiometric equivalent of aminocyclopyrachlor

None None

Commodity1

Tolerance (ppm) /Maximum Residue Limit 

(mg/kg)

US Canada Mexico2 Codex3

Cattle, fat 0.05

Cattle, meat byproducts 0.30

Cattle, meat 0.02

Goat, fat 0.05

Goat, meat byproducts 0.30

Goat, meat 0.02

Grass, forage 80

Grass, hay 200

Horse, fat 0.05

Horse, meat byproducts 0.30

Horse, meat 0.02

Milk 0.02

Sheep, fat 0.05

Sheep, meat byproducts 0.30

Sheep, meat 0.02

Completed: M. Negussie; 05/05/2011

1

Includes only commodities of interest for this action. Tolerance values should be the HED recommendations and 

not those proposed by the applicant.

2 Mexico adopts US tolerances and/or Codex MRLs for its export purposes.

3 * = absent at the limit of quantitation; Po = postharvest treatment, such as treatment of stored grains. PoP = 

processed postharvest treated commodity, such as processing of treated stored wheat. (fat) = to be measured on the 

fat portion of the sample. MRLs indicated as proposed have not been finalized by the CCPR and the CAC.
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Attachments:

Appendix I - Chemical Names and Structures of Aminocyclopyrachlor Residues of Concern

Appendix II - Tolerance Assessment Calculations
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Appendix I. Chemical Names and Structures of Aminocyclopyrachlor Residues of 

Concern. 

Common name;

Company code(s)

Chemical name Chemical structure

Aminocyclopyrachlor; 

DPX-MAT28

6-amino-5-chloro-2-cyclopropyl-4-

pyrimidinecarboxylic acid

N

N

NH2

Cl

O

OH

Aminocyclopyrachlormethyl; 

DPX-KJM44

(methyl ester)

methyl 6-amino-5-chloro-2-

cyclopropyl-4-pyrimidinecarboxylate

N

N

NH2

Cl

O

O

CH3

IN-LXT69 5-chloro-2-cyclopropylpyrimidin4-ylamine

N N

H2N

Cl

IN-Q3007 cyclopropanecarboxamide

O

N

H

H

IN-V0977 cyclopropanecarboxylic acid

O

HO

IN-QFH57 4-cyano-2-cyclopropyl-1Himidazole-5- carboxylic acid

HN N

OH

N O
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Common name;

Company code(s)

Chemical name Chemical structure

IN-QGC48 methyl-4-cyano-2-cyclopropyl-1Himidazole-5-carboxylate
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Appendix II. Tolerance Assessment Calculations.

For each of the grass commodities listed below, the OECD MRL calculator (March 2011 

version), was used for calculating recommended tolerances. The statistical goal of the OECD 

MRL calculator is to produce an MRL proposal in the region of the 95th percentile of the 

underlying residues distribution. The average residue values used to calculate the tolerances are 

provided in Table I-1. Residue values represent total residues of aminocyclopyrachlor (DPXMAT28) and aminocyclopyrachlor-methyl (DPX-KJM44) converted to parent acid equivalents.

Table I-1. Residue data used to calculate tolerance for aminocyclopyrachlor in/on grass commodities.

Regulator: EPA

Chemical: Aminocyclopyrachlor

Crop: Grass forage Grass hay

PHI: 0 Days 0 Days

App. Rate: 0.281 lb ai/A 0.281 lb ai/A

Submitter: E.I. du Pont de Nemours and Company E.I. du Pont de Nemours and Company

MRID Citation: MRID 48333630 MRID 48333630

Total Aminocyclopyrachlor Residues

[Aminocyclopyrachlor + Aminocyclopyrachlor-methyl; ppm]

9.25 26.6

10 28.5

14.3 32.1

14.7 35.2

16.3 35.6

17.5 36.4

18.3 36.7

19.5 41.6

21.1 42.2

25.9 43.8

26.9 47.3

27.1 48.2

28.5 48.5

30.5 49

31.8 54.5

32.9 55.9

33.5 58.7

40.9 72.5

47.3 75.8

50.3 90.2

14.3 112

18.3 122
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Grass forage

The dataset used to establish a tolerance for aminocyclopyrachlor on grass forage consisted of 

field trial data representing application rates of 0.274-0.299 lb ai/A aminocyclopyrachlor with a 

0-day PHI. The field trial application rates and PHIs are within 25% of the maximum label 

application rate and minimum label PHI, respectively. The average residues values used to 

calculate the tolerance are provided in Table I-1. Residue values represent total residues of 

aminocyclopyrachlor and aminocyclopyrachlor-methyl converted to parent acid equivalents. 

Residues of both aminocyclopyrachlor and aminocyclopyrachlor-methyl were quantifiable (LOQ 

= 0.01 ppm) in/on all samples of grass forage. 

The aminocyclopyrachlor grass forage dataset was entered into the OECD MRL calculator; the 

recommended tolerance is 80 ppm for grass forage.

Aminocyclopyrachlor

Grass Forage

US and Canada

1 appl @0.281 lb ai/A 0-day PHI

Total number of data (n) 22

Percentage of censored data 0%

Number of non-censored data 22

Lowest residue 9.250

Highest residue 50.300

Median residue 23.500

Mean 24.961

Standard deviation (SD) 11.334

Correction factor for censoring (CF) 1.000

Proposed MRL estimate

- Highest residue 50.300

- Mean + 4 SD 70.298

- CF x 3 Mean 74.884

Unrounded MRL 74.884

Rounded MRL 80
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Grass hay

The dataset used to establish a tolerance for aminocyclopyrachlor on grass hay consisted of field 

trial data representing application rates of 0.274-0.299 lb ai/A aminocyclopyrachlor with a 0-day 

PHI. The field trial application rates and PHIs are within 25% of the maximum label application 

rate and minimum label PHI, respectively. The average residues values used to calculate the 

tolerance are provided in Table I-1. Residue values represent total residues of 

aminocyclopyrachlor and aminocyclopyrachlor-methyl. Residues of both aminocyclopyrachlor 

and aminocyclopyrachlor-methyl were quantifiable (LOQ = 0.01 ppm) in/on all samples of grass 

forage. 

The aminocyclopyrachlor grass hay dataset was entered into the OECD MRL calculator; the 

recommended tolerance is 200 ppm for grass hay.

Aminocyclopyrachlor

Grass Hay

US and Canada

1 appl @0.281 lb ai/A 0-day PHI

Total number of data (n) 22

Percentage of censored data 0%

Number of non-censored data 22

Lowest residue 26.600

Highest residue 122.000

Median residue 47.750

Mean 54.241

Standard deviation (SD) 25.684

Correction factor for censoring (CF) 1.000

Proposed MRL estimate

- Highest residue 122.000

- Mean + 4 SD 156.977

- CF x 3 Mean 162.723

Unrounded MRL 162.723

Rounded MRL 200