UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

MEMORANDUM 

Date: February 11, 2015 

Subject: Trinexapac-ethyl. Section 3 Registration Request to Add New Uses on Rice and 

Rye. Summary of Analytical Chemistry and Residue Data. 

PC Code: 112602 

Decision No.: 488373 

Petition No.: 4F8254 

Risk Assessment Type: NA 

TXR No.: NA 

MRID No.: 49282807 

FROM: Sumitra Bose Biswas, Chemist 

Risk Assessment Branch Vl 

DP Barcode: D424894 

Registration No.: 100-727, 100-949, 100-

1241 

Regulatory Action: Section 3 new food use 

registration 

CaseNo.: NA 

CAS No.: 95266-40-3 

~ 

40 CFR: § 180.662 

<1 · ~'WJ1P1. 

Health Effects Division (HED; 7509P) 

THROUGH: 

Donna 

Sheila Pip

Davis, 

er, Chemist 

Acting Chief 

~ 

Risk Assessment Branch VI 

Health Effects Division (7509P) 

To: Bethany Benbow, Chemical Risk Manager 

Kathryn Montague, Chemical manager 

Dan Kenny, Branch Chief 

Risk Management and Implementation Branch I 

Herbicide Branch/ Registration Division (7505P) 

Page 1 of 31 
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

Page 2 of 31

Summary of Submitted Residue Chemistry Studies

OCSPP 860 

Series 

Guideline

MRID Number Monograph 

Annex B 

Reference

Title

1000, 1500, 

1520

49282807 Nakia Smith, M.S., (2014). Trinexapac-Ethyl EC (A7725M) -

Magnitude of the Residues in or on Rice.
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

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Table of Contents

1.0 Executive Summary............................................................................................................ 5

2.0 Regulatory Recommendations............................................................................................ 6

2.1 Data Deficiencies/Data Needs.......................................................................................... 6

2.2 Tolerance Considerations................................................................................................. 6

2.2.1 Enforcement Analytical Method............................................................................... 6

2.2.2 Recommended Tolerances........................................................................................ 7

2.2.3 Revisions to Petitioned-For Tolerances.................................................................... 7

2.2.4 International Harmonization ..................................................................................... 7

3.0 Introduction......................................................................................................................... 8

3.2 Physical/Chemical Characteristics................................................................................... 9

3.3 Pesticide Use Pattern/Directions for Use (860.1200)....................................................... 9

4.0 Metabolite/Degradate Residue Profile.............................................................................. 11

4.1 Nature of the Residue..................................................................................................... 11

4.1.1 Summary of Plant Metabolism (860.1300)............................................................. 11

4.1.3 Summary of Confined/ Field Rotational Crops...................................................... 12

4.2 Comparison of Metabolic Pathways .............................................................................. 13

4.3 Residues of Concern Summary and Rationale............................................................... 13

5.0 Residue Profile.................................................................................................................. 14

5.1 Residue Analytical Methods (860.1340)........................................................................ 14

5.1.1 Data Collection Methods ........................................................................................ 14

5.1.2 Multi-Residue Methods (860.1360)........................................................................ 15

5.1.3 Tolerance Enforcement Methods............................................................................ 15

5.1.4 Submittal of Analytical Reference Standards (860.1650) ...................................... 15

5.2 Storage Stability (860.1380) .......................................................................................... 16

5.3 Residue Data .................................................................................................................. 17

5.3.1 Crop Field Trials (860.1500) .................................................................................. 17

DER Reference ..................................................................................................................... 17

5.3.2 Field Rotational Crops (860.1900) ......................................................................... 22

5.3.3 Processed Food and Feed (860.1520)..................................................................... 22

5.3.4 Meat, Milk, Poultry and Eggs................................................................................. 25

5.3.5. Food Handling (860.1460)...................................................................................... 25

5.3.6 Water, Fish, and Irrigated Crops (860.1400).......................................................... 25
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

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5.4 Food Residue Profile...................................................................................................... 25

6.0 Tolerance Derivation ........................................................................................................ 25

7.0 ChemSAC Reference ........................................................................................................ 26

Appendix A. Field Trial Geographic Distribution....................................................................... 27

Appendix B. International Residue Limits Table ........................................................................ 28

Appendix C. OECD MRL Calculator Rice Grain ........................................................................ 29

OECD MRL Calculator Rice Grain Rice Straw ........................................................................... 30

REFERENCES ............................................................................................................................. 31

 
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

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1.0 Executive Summary

Trinexapac-ethyl is a plant growth regulator currently registered to Syngenta Crop Protection for 

use on perennial rye grass grown for seeds in the Pacific Northwest; cereal grains (barley, oats, 

triticale and wheat) and sugarcane. Trinexapac-ethyl is formulated as both a 1 lb/gal emulsifiable 

concentrate (EC 12% a.i.) under the trade name PalisadeTM EC (EPA reg. No. 100-949) and 2 

lb/gal EC (25.5%, PalisadeR2EC; EPA Reg. No. 100-1241).

Syngenta has petitioned to establish a permanent tolerance for residues of trinexapac-ethyl in/on 

rice and rye. The registrant provided field trial data on the use of trinexapac-ethyl in/on rice 

commodities. 

Syngenta is proposing the establishment of permanent tolerances for residues of trinexapac-ethyl, 

and its metabolites and degradates in/on rice and rye commodities at the following levels:

Commodities Proposed tolerances, ppm

Rice, grain 0.4

Rice, straw 0.07

Rice, bran 1.5

Rice, wild, grain 0.4

Rye, bran 6.0

Rye, grain 4.0

Rye, hay 1.5

Rye, straw 0.9

The metabolic fate of trinexapac ethyl residues in plants (primary and rotational crops) and 

livestock commodities is well understood and the residues of concern (ROC) in plants (primary 

and rotational crops) for tolerance establishment and risk assessment purposes include free and 

conjugated residues of both parent and its acid metabolite, trinexapac. The nature of the residue in 

livestock (ruminant and poultry) is well understood and the residues of concern (ROC) in livestock

(ruminant and poultry) are free and conjugated parent trinexapac ethyl and its acid metabolite.

Rice field trials have been submitted which are adequate in number and geographic representation, 

generated by a validated analytical method, and supported by adequate storage stability data. The 

recommended tolerances on rye commodities are based on the November 25, 2009 ChemSAC 

decision that provides an allowance for extrapolating residue data for barley and wheat to 

additional small cereal grains. 

An acceptable processing study has been provided which shows that residues of trinexapac-ethyl 

concentrate in polished rice and bran but do not concentrate in hulls. The processing data supports 

the proposed tolerance for rice bran at 1.5 ppm.

There are no livestock feed items associated with this petition; therefore a discussion of the 

magnitude of residues in livestock commodities, as well as the need for livestock tolerances and 
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

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analytical methods is not pertinent to this discussion.

The previously submitted confined rotational crop study is adequate to address rotational crop 

considerations for this action. The current label reflects the 30-day plantback restriction for 

cereal grains and leafy vegetables based on the existing data. 

There are no established or proposed Codex, Canadian, or Mexican maximum residue limits

(MRLs) for trinexapac-ethyl in or on any food or feed crops. There are no issues with respect to 

international harmonization associated with this petition.

2.0 Regulatory Recommendations

HED has examined the residue chemistry database for trinexapac ethyl. There are no residue 

chemistry considerations that would preclude granting the requested trinexapac ethyl tolerances 

in/on rye and rice.

2.1 Data Deficiencies/Data Needs

There are no residue chemistry data deficiencies for this action. A human health risk assessment 

to support the new use is forthcoming.

2.2 Tolerance Considerations

2.2.1 Enforcement Analytical Method

Sheila Piper, Human Health Risk Assessment for Registration Review (D413570), 9/12/2013.

An adequate enforcement method is available to enforce the proposed rice and rye tolerances for

trinexapac-ethyl, Method GRM020.01A, which utilizes high performance liquid chromatography 

with triple-quadrupole mass spectrometry (LC-MS/MS). Method GRM020.01A includes a strong 

acid hydrolysis/extraction procedure to release both “free” and “conjugated” residues of trinexapac 

acid. The reported limit of quantitation (LOQ) is 0.010 ppm. 

In summary, 10-g subsamples were refluxed with 200 mL of 80/20 acetonitrile (ACN)/1N

hydrochloric acid (HCl) for 300 minutes. An aliquot is mixed well with water and passed through 

a pre-conditioned C8 SPE cartridge followed by analysis by HPLC-MS/MS for trinexapac acid. 

The limit of quantitation (LOQ) is 0.01 ppm for trinexapac acid.

HED notes that this method does not convert trinexapac acid to parent equivalents. Tolerances are 

expressed as parent equivalents; therefore the results of the enforcement analysis should include a 

molecular weight conversion to parent equivalents prior to comparison to the tolerance levels.
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

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2.2.2 Recommended Tolerances

Permanent tolerances are currently established for residues of trinexapac ethyl including its 

metabolites and degradates under 40 CFR 180.662(a)(1) in/on various plant and animal 

commodities. 

The tolerance expression listed in the 40 CFR 180.662 complies with the HED interim tolerance 

expression policy (S. Knizner, 5/27/09). Permanent tolerances for trinexapac ethyl should be 

established under 180.662(a) for the commodities listed below at the HED-recommended tolerance 

levels shown in Table 2.2.2.

Table 2.2.2. Tolerance Summary for Trinexapac ethyl.

Commodity Established/Proposed 

Tolerance (ppm)

HED-Recommended 

Tolerance (ppm)

Comments 

(correct commodity definition)

Rice, grain 0.4 0.4 NA

Rice, straw 0.07 0.07 NA

Rice, bran 1.5 1.5 NA

Rice, wild, grain 0.4 0.4 NA

Rye, bran 2.5 6.0 NA

Rye, grain 2.0 4.0 NA

Rye, hay 0.8 1.5 NA

Rye, straw 0.4 0.9 NA

2.2.3 Revisions to Petitioned-For Tolerances

The registrant has proposed tolerances for rice commodities, the proposed residue level for each 

commodity was derived using the OECD MRL calculation. For rye, the registrant proposed 

tolerances by extrapolating residue data for barley. ChemSAC determined that established 

tolerances for the cereal grains could be extrapolated to other small grains. Since different 

tolerances are set for the different cereal grain, HED believes it is more appropriate to establish 

the rye tolerances at the level of the highest cereal grain tolerance. Since tolerances for wheat 

commodities are higher than tolerances for barley commodities, HED recommends establishing 

the new rye tolerances at the level of the wheat tolerances.

2.2.4 International Harmonization

There are no established or proposed Codex, Canadian, or Mexican maximum residue limits 

(MRLs) for trinexapac-ethyl in or on any food or feed crops. However, a variety of European 

countries, as well as Argentina, Brazil, Japan, Korea, and Australia have established or proposed 

MRLs for trinexapac-ethyl on cereal grains (0.02-0.5 ppm), cereal grain forages and fodders (0.2-

3 ppm), sugarcane (0.05-0.1 ppm), sugar forage and fodder (1 ppm), meat (0.02 ppm), and/or milk 

(0.1-0.005 ppm). At this time, there are no issues with respect to international harmonization 

associated with this petition.
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

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2.3 Label Recommendations

The proposed label is adequate as submitted. No revisions are required.

3.0 Introduction

Trinexapac-ethyl is a plant growth regulator currently registered for use on grasses grown for seed,

cereal grains (barley, oats, triticale and wheat) and sugarcane. Trinexapac-ethyl inhibits internodal 

elongation and growth in cereal grains, grasses and several dicotyledonous species. It is registered 

in numerous European countries and several Asian and Latin American countries for uses on cereal 

grains and sugarcane. Tolerances are currently established for residues of trinexapac ethyl in/on 

food commodities under 40 CFR 180.662, at levels ranging from 0.02-40 ppm.

The nomenclature and physicochemical properties of trinexapac-ethyl are presented below in 

Tables 1 and 2.

Table 1.Trinexapac-ethyl Nomenclature.

Compound

Common name Trinexapac-ethyl

Company experimental name CGA163935

IUPAC name ethyl (RS)-4-cyclopropyl(hydroxy)methylene-3,5-dioxocyclohexanecarboxylate

CAS name ethyl 4-(cyclopropylhydroxymethylene)-3,5-dioxocyclohexanecarboxylate

CAS registry number 95266-40-3

End-use product (EP) 1.0 lb/gal EC (PalisadeTM EC; EPA Reg. No. 100-949)

2.0 lb/gal EC (Palisade 2EC; EPA Reg. No. 100-1241)

Regulated Metabolite

Common Name Trinexapac

Company Experimental 

Name

CGA-179500

IUPAC name (RS)-4-cyclopropyl(hydroxy)methylene-3,5-dioxocyclohexanecarboxylic acid

CAS name 4-(cyclopropylhydroxymethylene)-3,5-dioxocyclohexanecarboxylic acid

CAS registry number 104273-73-6

OH

O

O

O

O

H3C

O

O

O

HO OH
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

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3.2 Physical/Chemical Characteristics

Trinexapac-ethyl has a relatively low octanol/water partition coefficient. At pH 5.3, the log KOW

value is 2.44 (KOW = 275). Trinexapac-ethyl has a low potential to leach into groundwater and is 

not expected to be volatile because of its low vapor pressure (2.16 x 10-3 Pa at 25oC). See Table 

3.2 for a listing of trinexapac-ethyl physical and chemical properties. 

Table 3.2 Physicochemical Properties of Trinexapac-ethyl.

Parameter Value Reference

Melting point/range 36.1-36.6°C Provided in MRID 

pH 3.3 46809305

Density (20oC) 1.215 g/cm3

Water solubility (g/L at 25°C) 2.8 at pH 4.9

10.2 at pH 5.5

21.1 at pH 8.2

Solvent solubility Acetone 100% Ethanol 100%

Toluene 100% n-octanol 100%

n-hexane 5%

Vapor pressure (25oC) 1.62 x 10-5 mm Hg

Dissociation constant, pKa 4.57

Octanol/water partition coefficient, 

Log(KOW) at 25oC

2.44 at pH 5.3

UV/visible absorption spectrum Neutral: 9335 L/mol·cm @ 240.2 nm

13976 L/mol·cm @ 277.4 nm

Acidic: 11712 L/mol·cm @ 240.0 nm

12368 L/mol·cm @380.4 nm

Basic: 21320 L/mol·cm @ 270.8 nm

3.3 Pesticide Use Pattern/Directions for Use (860.1200)

Trinexapac-ethyl is marketed as an emulsifiable concentrate, wettable powder packed in watersoluble bags, and granule. Syngenta Crop Protection has registered trinexapac-ethyl for multiple 

end-use products on turf areas such as sod farms, golf courses, sport fields, cemeteries, and similar 

areas, and on grasses grown for seed, sugarcane, and cereal grains (wheat, barley, oats, and 

triticale). The label-required personal protective equipment (PPE) for occupational applicators and 

handlers is a long-sleeved shirt, long pants, shoes, and socks, chemical-resistant gloves, and 

protective eyewear. The currently proposed uses on rice and rye are summarized in Table 3.3.
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

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Table 3.3. Summary of Directions for the Proposed Uses of Trinexapac-ethyl 

Applic. Timing, 

Type, and 

Equip.

EPA Reg. 

No.

(formulation 

type)

Max.

Single 

Application 

Rate 

(lb ai/A)

Max. No. 

Application 

per year

Max. 

Annual 

App. 

Rate 

(lb ai/A) 

RTI 

(days)

PHI 

(days)

Use Directions and 

Limitations

Rice

Post-emergent 

aerial

application to 

flooded rice 

fields

1.0 lb/gal EC 

100-949 

2.0 lb/gal EC

100-1241

0.045 1 0.045 NA 50

For best performance, 

apply a single 

application to one of 

the following growth 

stages:

Fully tillered, panicle 

initiation, or panicle 

formation. Do not 

apply once internode is 

more than 1⁄2 to 3⁄4 inch 

in length. 

Rye

(same use directions as other small grains/cereals currently on the labels)

Post-emergent 

application 

(ground or aerial)

1.0 lb/gal EC 

100-949 

2.0 lb/gal EC

100-1241

0.11 1

0.11 45

Make applications from 

the Feekes growth 

stage 4 through Feekes 

growth stage 7.

Split applications may 

be made at Feekes 

growth stage 4-5 and 

then again at Feeks 7 

and 8. Apply in a min 

of 20 gal/A.

0.05 2

Conclusion

The proposed label for trinexapac-ethyl is adequate to allow evaluation of the residue data 

relative to the proposed use on rice. Label direction for rye are equivalent to the currently 

registered uses of cereal grains. 
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

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4.0 Metabolite/Degradate Residue Profile

4.1 Nature of the Residue

4.1.1 Summary of Plant Metabolism (860.1300)

DER References: 45898902.der (grass); 45898904.der (spring wheat); 46809306.der (rice); Sheila Piper, Trinexapac-ethyl 

Summary of Residue Chemistry and Analytical data (D378491), 11/23/2011.

The nature of trinexapac-ethyl residues in rice and rye commodities is understood based on the 

available rice and grass studies on [1,2,6-

14Ccyclohexyl]trinexapac-ethyl. The major metabolite in 

rice and grass is acid metabolite, CGA179500. The parent was detected at 2% of the total 

radioactive residue (TTR). In rice and grass, the metabolism of 14C-trinexapac-ethyl rapidly 

undergoes hydrolysis of the ethyl ester to form trinexapac. Also, the tricarboxylic acid metabolite, 

CGA 275537 was identified at the 4x rate in rice (3-17%TRR) at 60 DAT and in grass (9-15% 

TRR). This metabolite has the potential for inhibiting the citric acid cycle. However, given the 

levels of exposure observed in submitted studies, ROCKS does not expect this metabolite to 

contribute significantly to risk. Therefore the tricarboxylic acid metabolite does not need to be 

included as a residue of concern.

The proposed metabolic pathway of trinexapac-ethyl in plants includes hydrolysis of the ester bond 

to trinexapac. Further degradation proceeds via stepwise oxidation/decarboxylation after cleavage 

of the 6-membered ring yielding saturated and unsaturated tricarboxylated acids.

HED Conclusions:

The residues of concern in plants for tolerance establishment and risk assessment purposes include 

free and conjugated residues of both parent and its acid metabolite, trinexapac (ROCKS memo, 

D390121, 7/12/11).

4.1.2 Summary of Livestock Metabolism (860.1300)

Ruminants:

S. Piper, D402207, 5/23/2012

No new livestock metabolism study for ruminant was submitted. In previously submitted goat 

metabolism studies (MRIDs 45898905 and 48043705) total of three lactating goats were dosed 

orally via capsules once a day for 4 consecutive days with [1,2,6-14C-cyclohexyl] trinexapacethyl (97.9% radiochemical purity) at a dose of 150 mg ai/goat/day, which was equivalent to 2.92-

3.21 mg ai/kg body weight/day. 

The study shows that majority of the administered doses was excreted via feces and urine. 

Trinexapac-ethyl was not detected in any goat matrices analyzed. The major 14C-residue in milk

(84-97%) and all tissues (84-97%) was the acid metabolite, CGA 179500. The metabolite CGA 

113745 was also identified in the liver (16% Total Radioactive Residue (TRR)), kidney (6% TRR) 

and fat (11%), but was not detected in muscle or milk. However, the CGA 113745 metabolite 

had no structural alerts and has a carboxyl group that should make it readily excreted, making it 
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

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also of less toxicological concern. 

Poultry:

S.Piper, D402207, 5/23/2012

In a previously reviewed study (MRID 48043704), of 14C-trinexapac ethyl (cyclohexadione ring 

label) was administered orally via gelatin capsule to five laying hens at a nominal rate of 10 ppm 

in the diet for 10 consecutive days. The majority of the administered dose (88-91%) was found to 

have been excreted. The TRR were below 0.01 ppm for the edible tissues and egg yolks, therefore,

they were not further investigated. The major residues in poultry were identified as the parent 

compound trinexapac-ethyl (31% TRR) and its acid metabolite CGA 179500 (20% TRR).

The major metabolic pathways both in hens and ruminant are similar which involves hydrolysis 

of the ethyl ester to yield trinexapac acid (CGA 179500).

HED Conclusions:

The nature of the residue in livestock is adequately understood based on the available ruminant 

and poultry metabolism studies. Based on the available data, the residues of concern in livestock 

commodities for tolerance enforcement and risk assessment purposes are free and conjugated 

trinexapac-ethyl and the acid metabolite, trinexapac (ROCKS memo, D390121, 7/12/11). 

4.1.3 Summary of Confined/ Field Rotational Crops 

D378491, S. Piper 11/23/2011.

The previously submitted confined rotational crop study is adequate to satisfy data requirements.

In this study, sandy loam soil was treated once with 14C-Trinexapac-ethyl (66.2 μCi/mg) at a target 

rate of 0.312 lb ai/A (0.350 kg ai/ha); actual rates were 0.297-0.298 lb ai/A (0.333-0.334 kg ai/ha). 

Rotational crops (lettuce, radish and wheat) were planted at plant-back intervals (PBI) of 30, 120, 

and 270 days after treatment (DAT) (309 DAT for radish only) and samples of lettuce (immature 

and mature), radish tops (mature), radish roots (mature) and wheat (forage, hay, grain and straw) 

were collected at appropriate intervals. TRR values in all RACs were low; only 30-day PBI lettuce, 

wheat forage and wheat hay samples had TRR >0.01 ppm. The maximum TRR was 0.017 ppm 

(30-day PBI mature lettuce). No parent trinexapac-ethyl was found as a radiolabeled residue in 

any extracted RAC at any PBI. In addition, no individual extractable 14C-residue was found to be 

≥ 0.01 ppm for any RAC at any PBI. Based on the components identified, the results of the 

confined rotational crop study suggest that trinexapac-ethyl is metabolized in rotational crops via 

a route similar to that demonstrated in primary crops. 

HED Conclusions:

 The submitted confined rotational crop data are adequate to support the requested uses. 
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

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4.1.4 Summary of Metabolites and Degradates

4.2 Comparison of Metabolic Pathways

S. Piper, D377921, 11/23/2013.

The metabolism of trinexapac-ethyl in crops, livestock, and rats has been well characterized.

Metabolism appears to be similar in a variety of plant commodities. Based on the plant metabolism 

study, major residues identified include parent trinexapac-ethyl and metabolites trinexapac (CGA 

179500), aconitic acid metabolite CGA 312753, and tricarboxylic acid metabolite CGA 275537. 

The proposed metabolic pathway of trinexapac-ethyl in plants includes hydrolysis of the ester bond 

to trinexapac. Further degradation proceeds via stepwise oxidation/decarboxylation after cleavage 

of the 6-membered ring yielding saturated and unsaturated tricarboxylated acids.

The lactating goats and hen studies show that the majority of the administered doses was excreted 

via feces and urine. Radioactivity in the edible organs and tissues was readily and almost 

completely extracted, indicating that trinexapac ethyl or its metabolites were not bound in the 

organs and tissues. The major component of the extractable residue in liver, muscle and fat was 

the metabolite CGA 113745. However, the CGA 113745 metabolite had no structural alerts and 

has a carboxyl group that should make it readily excreted, making it also of less toxicological 

concern. 

 

The rat metabolism study also shows the trinexapac ethyl rapidly excreted via feces and urine. The 

major component in urine and fecal extracts was trinexapac, the free acid derivative of trinexapacethyl resulting from hydrolysis of the ester bond of the parent compound accounting for 

approximately 82.0–91.6% of the administered dose. The observed metabolic pathway of 

trinexapac-ethyl in livestock is comparable to the rat, which is the hydrolysis of ester bond.

HED Conclusions:

The proposed metabolic pathways in rats, livestock and plants are common. Trinexpac-ethyl 

involves hydrolysis of the ethyl ester to yield trinexapac (CGA 179500). Trinexapac undergoes 

cleavage of the hexane ring to yield the succinic acid metabolite, CGA 313458, which then 

undergoes stepwise oxidation/ decarboxylation to yield saturated and unsaturated tricarboxylic 

acids, such as CGA 275537 (tricarboxylic acid) and CGA 312753 (aconitic acid). 

4.3 Residues of Concern Summary and Rationale

ROCKS memo, 7/12/2011, D390121

For plants (primary and rotational crops) and livestock commodities, the ROCKS recommends 

that parent trinexapac-ethyl and the metabolite trinexapac (CGA 179500) be the residues of 

concern for both the tolerance expression and the risk assessment. For drinking water, a total 

residue approach should be used for the risk assessment. 
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

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Table 4.3. Summary of Metabolites and Degradates of Trinexapac-ethyl.

Matrix Residues included in Risk 

Assessment

Residues included in Tolerance 

Expression 

Plants Primary 

Crop

Trinexapac-ethyl parent + 

Trinexapac (CGA 179500)1

Trinexapac-ethyl parent + 

Trinexapac (CGA 179500)

Rotational 

Crop

Trinexapac-ethyl parent + 

Trinexapac (CGA 179500)

Trinexapac-ethyl parent + 

Trinexapac (CGA 179500)

Livestock Ruminant Trinexapac-ethyl parent + 

Trinexapac (CGA 179500)

Trinexapac-ethyl parent + 

Trinexapac (CGA 179500)

Poultry Trinexapac-ethyl parent + 

Trinexapac (CGA 179500)

Trinexapac-ethyl parent + 

Trinexapac (CGA 179500)

Drinking Water Total residues (parent + 

identified degradates)2

Not Applicable

1 Please see attached Appendix 1 for parent and metabolite names and structures. 

2 A total major residue approach is recommended, including parent and major environmental degradates CGA179500, CGA-313458, the open chain cyclohexane ring, and the unidentified hydroproduct M3. 

5.0 Residue Profile

5.1 Residue Analytical Methods (860.1340)

5.1.1 Data Collection Methods

D378491, S. Piper 11/23/2011.

Rice field trial samples were analyzed for residues of trinexapac-ethyl converted to the acid by 

LC/MS/MS using Syngenta Analytical Method GRM020.01A “Analytical Method for the 

Determination of Residues of trinexapac-Ethyl as trinexapac acid metabolite (CGA179500) in 

Crops by LC-MS/MS,” with minor modifications. This method was previously reviewed under 

DP# 378491 S. Piper, 11/23/2011) in conjunction with a crop field trial submission for barley grain 

(48043702.der).

Briefly, samples were refluxed with acetonitrile (ACN)/1 N HCl (80:20 v:v). An aliquot of the 

extract was applied to a C8 solid phase extraction (SPE) cartridge, and residues were eluted with 

0.5% formic acid:ACN (70:30 v:v). The eluate was adjusted to volume for LC/MS/MS analysis. 

The method does not provide for conversion of residues of CGA179500 to parent equivalents; 

therefore quantifiable residues of trinexapac were converted to parent equivalents by the study 

reviewer using a molecular weight conversion factor of 1.125 (MW trinexapac-ethyl 252.26/MW 

trinexapac acid 224.21). 

The limit of quantitation (LOQ), determined as the lowest level of method validation (LLMV) was 

0.01 ppm for trinexapac. The limit of detection (LOD) was not reported.

For concurrent recovery, samples of rice grain were fortified at 0.01 and 0.10 ppm each. The 

fortification levels bracketed the measured residues. 
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

Page 15 of 31

Individual recoveries for the fortification levels at 0.01 and 0.1 ppm are ranged from 72-123% and 

79-108% respectively. The relative standard deviations were <20% for each fortification levels.

All recoveries were generally within the acceptable range of 70-120%; therefore the method was 

considered valid for the analysis of residues of trinexapac-ethyl in rice grain. 

HED Conclusions: 

Analytical methods used to generate the residue data in support of this petition have been 

adequately validated.

5.1.2 Multi-Residue Methods (860.1360)

 DER reference: 45898908.der; (D378491), S. Piper, 11/23/2011.

Trinexapac-ethyl (CGA-163935) was evaluated using the FDA multiresidue method Protocols C 

and D, and its acid metabolite, trinexapac, was evaluated using Protocol B. Neither compound 

was tested using Protocols A and G as they do not contain an N-methylcarbamate moiety and are 

not substituted urea compounds, and trinexapac-ethyl was not evaluated through Protocol B as it 

has neither an acid nor phenol structure. 

Adequate GLC responses were obtained for trinexapac-ethyl using Modules DG1 and DG13 with 

electron capture detection, but the GLC responses for trinexapac were poor. The relative retention 

time (RRT) for trinexapac-ethyl (compared to chlorpyrifos) was 0.82 and 0.93 for DG1 and 

DG13, respectively. Following methylation, an adequate GLC response was obtained for 

methylated trinexapac using Module DG1 (RRT = 0.52). However, neither trinexapac-ethyl nor 

methylated trinexapac were recovered from the Florisil cleanup procedures. Therefore, testing 

through Protocols E and F was not conducted. 

HED Conclusions:

Trinexapac-ethyl was evaluated using the FDA multiresidue method Protocols C and D, and its 

acid metabolite, trinexapac, was evaluated using Protocol B. These data indicate FDA multiresidue methods are not suitable for determining residues of trinexapac-ethyl and trinexapac in 

plant commodities. 

 

5.1.3 Tolerance Enforcement Methods

Referred to section 2.2.1.

5.1.4 Submittal of Analytical Reference Standards (860.1650)

The Repository (email: T. Cole 02/09/2015) has the following analytes in stock from Syngenta: 

• Trinexapac ethyl, expiration date 10/30/2017.

• Trinexapac acid, expiration date 06/30/2015.
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

Page 16 of 31

A reminder to the petitioner, supplies of analytical standards must be replenished as requested by 

the repository as long as the tolerance is published in 40 CFR180.662. The address is as follows:

USEPA

National Pesticide Standards Repository/Analytical Chemistry Branch/OPP

701 Mapes Road

Fort George G. Meade, MD 20755-5350

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

5.2 Storage Stability (860.1380)

MRIDs 47101601 and 45898903, S. Piper, D378491 11/23/2011 

Rice: The available freezer storage stability data on wheat (grain and straw) indicate that residues 

of trinexapac-ethyl and its regulated metabolite were stable when stored frozen in wheat (grain) 

for 24 months (45898903.der). The sample storage condition and intervals are summarized in 

tables 5.2A and 5.2B.

Based on the current study, pre-processing rice grain (RAC) samples were stored frozen a 

maximum of 446 days (14.7 months) from harvest to extraction, and processed samples were 

stored frozen a maximum of 250 days (8.2 months) from processing to extraction (Table 5.2A).

Samples were analyzed within 2-4 days of extraction. Processing took place within 184-197 days 

(6.1-6.5 months) of harvest. Therefore, the available storage stability data are adequate to support 

the storage conditions and durations for rice grain (RAC) samples as well as for the processed 

commodities of rice for the current petition.

Table 5.2A. Summary of Storage Conditions.

Matrix Storage Temperature 

(°C)

Actual Storage 

Duration

(days/months)

Interval of Demonstrated Storage 

Stability

Rice grain 

(RAC)

Maintained frozen at 

processor (≤-12 C), 

preparation facility 

(<-10 C) and 

analytical laboratory 

(≤-20 C)

432-446 (14.2-

14.7) Residues of trinexapac acid were 

stable when stored frozen in wheat 

grain for up to 24 months.

Polished rice 246-248(8.1-8.2)

Hulls 246-248 (8.1-8.2)

Bran 248-250 (8.2)

Conclusions: Since the residues of trinexapac ethyl and its metabolite are stable up to 24 months 

in wide varieties of crops when stored at ≤-20oC, demonstrates that residues are also stable under 

the conditions and duration for rice. Therefore, HED concludes that the residues of trinexapac 

ethyl and its regulated metabolite are stable in rice up to 24 months when stored at ≤-20oC.
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

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5.3 Residue Data

5.3.1 Crop Field Trials (860.1500)

DER Reference

Rice: Syngenta Crop Protection, LLC has submitted field trial data (MRID 49282807) for 

trinexapac-ethyl on rice from 14 field trials conducted in the United States during the 2012 growing 

season in the North American Free Trade Agreement (NAFTA) Growing Zones 4 (AR; 4 trials, 

LA; 4 trials, MO; 1 trial), 5 (MO; 1 trial), 6 (TX, 2 trials) and 10 (CA; 2 trials). 

All trials, except for those listed in the table below (Table 5.3.1.), were separated by >20 miles and 

are therefore considered independent (568_Criteria for Independence of Trials 04/23/2013 (EPA 

and PMRA)). The trials separated by <20 miles have been assessed for independence as detailed 

in the table below. HED has determined that three trials in zone 4 (05, 07 and 08) should be 

considered replicate trials due to similar variety (all semi dwarf), same application dates, spray 

volume and same adjuvant. This decision is reflected in the total trial count above. The number 

and locations of field trials are not in compliance with OPPTS Guideline 860.1500. According to 

the OECD guideline, 16 independent field trials are required for rice. However, HED considers 14 

field trials for rice to be acceptable because while fewer trials are submitted from the area that 

appears to yield higher residues, use of the OECD calculator yields a recommended tolerance of 

0.4 ppm, which is significantly higher than any of the residue values from that region. 

Table 5.3.1. Independent Trial Determination1

Trial Nos. Differences Decision

01, 06, and 09 Same location

Variety: Roy J (mid-season, long grain) 

vs. CL 261 (medium grain) vs. Wells 

(short-season long-grain, large kernel 

size)

All separate due to variety, different 

application dates (1-6 days), different 

spray volume (3-6 GPA), and/or 

different adjuvant.

04, 05, 07, 08, 10 Same location (05, 07, 08, 10)

Variety: XL 729 (very early season, long 

grain, tall), CL 151 (very early season, 

long grain, semi-dwarf; 19.5K seed/lb), 

Cocodrie (very early, short season, long 

grain, semi-dwarf, 20.6K seed/lb), 

Cypress (08 and 10; early, long-grain, 

semi-dwarf, 19.1K seed/lb)

04 separate due to variety (tall vs. 

semi-dwarf);

10 separate due to different application 

date (20 days).

05, 07, 08: Replicates due to similar 

variety (all semi dwarf), same 

application dates, spray volume and 

same adjuvant.

11 and 12 Zone: 4 vs. 5 Separate due to Zone

13 and 14 Same location

Variety: Presidio (early season, long 

grain, semi-dwarf) vs. Cheniere (very 

early season, long grain, semi-dwarf, hi 

yield).

No other differences in criteria

Separates due to the varieties and 

different application date (8 days).
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

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Table 5.3.1. Independent Trial Determination1

Trial Nos. Differences Decision

15 and 16 Same location and variety

No other differences in criteria

Residues: <0.01 vs. 0.074 ppm

Separate due to different residues

1 All assessments are based on the replicate trial guidance presented in draft memo 568_Criteria for Independence of Trials 

04/23/2013 (EPA and PMRA) and have been approved by HED; since the study predates the guidance, the criteria specified in 

the guidance was not strictly adhered to. 

Each trial consisted of one untreated plot and one treated plot. Each treated plot received a single 

foliar broadcast spray application of the 2.08 lb ai/gal emulsifiable concentrate (EC) formulation 

of trinexapac-ethyl (Trinexapac-Ethyl EC, A7725M) made at BBCH 30-32 (panicle initiation or 

green ring stage) at 0.041-0.046 lb ai/A/application. Applications were made using ground 

equipment in spray volumes of 2.4-10 gal/A. A nonionic surfactant (NIS) or crop oil concentrate 

(COC) was included in the spray mixtures for all applications. Samples of rice grain and straw 

were harvested at maturity at preharvest intervals (PHIs) of 51-100 days. Rice straw is no longer 

considered a significant livestock feed item and is not further addressed herein. At two trials (AR 

trial -09 and CA trial -15), additional samples were collected to monitor residue decline 7 and14 

days before and after normal crop harvest; PHIs were 65, 72, 79, 85 and 94 days for trial -09 and 

85, 92, 99, 106 and 113 days for trial-15. 

Samples were analyzed for residues of trinexapac-ethyl determined as trinexapac acid using 

Syngenta Analytical Method GRM020.01A (with minor modifications), a high performance liquid 

chromatography method with tandem mass spectrometric detection (LC/MS/MS). The limit of 

quantitation (LOQ, determined as the lowest level of method validation, LLMV) was 0.01 ppm. 

The method does not provide for conversion of residues of trinexapac acid (CGA179500) to parent 

equivalents; therefore quantifiable residues of CGA179500 were converted to parent equivalents 

by the study reviewer using a molecular weight conversion factor of 1.125 (MW trinexapac-ethyl 

252.26/MW trinexapac acid 224.21). Acceptable method validation and concurrent recovery data 

were reported for rice grain fortified with CGA179500 at 0.01-1.0 ppm, thus validating the 

method. The fortification levels were adequate to bracket expected residue levels. 

The results from the submitted field trials are presented in Tables B.7.6.1.1-6 and B.7.6.1.1-7. 

In rice grain harvested at PHIs of 51-100 days following a single foliar broadcast application of 

the 2.08 lb ai/gal EC formulation of trinexapac-ethyl made at 0.041-0.046 lb ai/A, individual 

sample (and per-trial average) residues of trinexapac-ethyl (determined as CGA179500) were 

<0.01-0.270 ppm (<0.01-0.214 ppm).

In one residue decline trial residues were variable, with the highest residues observed at the target 

PHI. In the second residue decline trial, residues were below the LOQ in/on all samples; therefore, 

residue decline could not be determined.
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

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Table 5.3.2. Residue Data from Rice Field Trials with Trinexapac-Ethyl.

Location: City, State; 

Year2(Trial ID)

Zone Rice Variety Matrix Rate

lb ai/A

PHI3

(days)

Residues trinexapac-ethyl4(ppm) 

[Average]

Proctor, AR; 2012 

(TK0044924-01)

4 Roy J Grain 0.045 74 0.069, 0.059

[0.064]

Pollard, AR; 2012 

(TK0044924-02)

4 RiceTec XL 729 Grain 0.045 85 0.061, 0.051

[0.056]

Cheneyville, LA; 2012 

(TK0044924-03)

4 CL 111 Grain 0.046 53 0.060, 0.056

[0.058]

Ville Platte, LA; 2012 

(TK0044924-04)

4 XL 729 Grain 0.046 51 0.026, 0.025

[0.025]

Washington, LA; 2012 

(TK00044924-05)

and

Washington, LA; 2012 

(TK0044924-07)

and

Washington, LA; 2012 

(TK0044924-08)

4 CL 151

Cocodrie

Cypress

Grain 0.044

0.044

0.046

60

60

60

0.180, 0.203, 0.270, 

0.236, 0.191, 0.203

[0.214]

Proctor, AR; 2012 

(TK0044924-06)

4 CL261 Grain 0.045 68 0.024, 0.024

[0.024]

Proctor, AR; 2012 

(TK0044924-09)

4 Wells Grain 0.045 65 0.043

72 0.053

79 0.088, 0.075

[0.082]

85 0.061

94 0.070

Washington, LA; 2012 

(TK0044924-10)

4 Cypress Grain 0.046 54 0.191, 0.203

[0.197]

Fisk, MO; 2012 

(TK0044924-11)

4 RiceTec XP 753 Grain 0.045 91 0.038, 0.036

[0.037]

Fisk, MO; 2012 

(TK0044924-12)

5 Francis Grain 0.045 85 0.037, 0.041

[0.039]

East Bernard, TX; 2012 

(TK0044924-13)

6 Presidio Grain 0.044 90 0.113, 0.113

[0.113]

East Bernard, TX; 2012 

(TK0044924-14)

6 Cheniere Grain 0.041 75 0.019, 0.019

[0.019]

Porterville, CA; 2012 

(TK0044924-15)

10 Koshihikari Grain 0.045 85 ND

92 <0.01

99 <0.01, <0.01

[<0.01]

106 <0.01

113 <0.01

Porterville, CA; 2012 

(TK0044924-16)

10 Koshihikari Grain 0.046 100 0.092, 0.073

[0.083]

1 A 2.08 lb ai/gal EC formulatioin (A7725M) was used.

2 HED has determined that Trials 05, 07, and 08 are replicate trials.

3 Target PHIs are bolded for decline trials.

4 ND = Not detected (no peak) as reported by the petitioner. The method determines residues of trinexapac-ethyl as 

CGA179500. Residues of CGA179500 were converted to parent equivalents by the study reviewer using a molecular weight 

conversion factor of 1.125 (MW trinexapac-ethyl 252.26/MW trinexapac acid 224.21). Per trial averages were calculated by the 

study reviewer.
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

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Table 5.3.2. Summary of Residues from Rice Field Trials with Trinexapac-Ethyl.

Crop Matrix Total 

Application 

Rate

lb ai/A

PHI 

(days)

n

1 Residues (ppm Trinexapac-ethyl)

Min.2 Max.2 LAFT3 HAFT3 Median3 Mean3 SD3

Rice Grain 0.041-0.046 51-100 14 <0.01 0.270 <0.01 0.214 0.057 0.073 0.063

1 n = number of field trials.

2 Values based on total number of samples.

3 Values based on per-trial averages. LAFT = lowest average field trial, HAFT = highest average field trial, SD = standard 

deviation. For computation of the LAFT, HAFT, median, mean, and standard deviation, values <LOQ are assumed to be at the 

LOQ (0.01 ppm for trinexapac-ethyl as CGA179500).

Table 5.3.3. Summary of Residues of Trinexapac-Ethyl in/on straw.

Trial ID 

(State/Year)

NAFTA

Region

Rice Variety Matrix

Nominal

Total

Rate

1

(lb ai /A)

Nominal

Sampling

Event

2

Trinexapac-Ethyl Residue Levels (ppm)

3

CGA179500 Trial Mean

4

TK0044924-01

(AR/2012)

4 Roy J

Straw --- -- ND ---

Straw

Straw

0.045 Maturity 0.012

0.017 0.0145

TK0044924-02

(AR/2012)

4

RiceTec XL

729

Straw --- -- ND ---

Straw

Straw

0.045 Maturity <LOQ ND 0.0075

TK0044924-03

(LA/2012)

4 CL 111

Straw --- -- ND ---

Straw

Straw

0.046 Maturity 0.018

0.013 0.0155

TK0044924-04 

(LA/2012)

4 XL 729

Straw --- -- ND ---

Straw

Straw

0.046 Maturity ND

ND 0.005

TK0044924-05 

(LA/2012)

4 CL 151

Straw --- -- ND ---

Straw

Straw

0.044 Maturity 0.045

0.034 0.0395

TK0044924-06 

(AR/2012)

4 CL261

Straw --- -- ND --

Straw

Straw

0.045 Maturity <LOQ

ND

0.0075

TK0044924-07

(LA/2012)

4 Cocodrie

Straw --- -- ND --

Straw

Straw

0.044 Maturity 0.036

0.035 0.0355

TK0044924-08

(LA/2012)

4 Cypress

Straw --- -- ND --

Straw

Straw

0.046 Maturity 0.027

0.024 0.0255

TK0044924-09

(AR/2012)

4 Wells Straw -- -- ND --

Straw

0.045

14 PM ND --

Straw 7 PM <LOQ --

Straw

Straw

Maturity 0.013

<LOQ 0.0115

Straw 7 AM <LOQ --

Straw 14 AM <LOQ --

TK0044924-10 

(LA/2012)

4 Cypress

Straw --- -- ND ---

Straw

Straw

0.046 Maturity 0.044

0.045 0.0445

TK0044924-11

(MO/2012)

4

RiceTec XP

753

Straw --- -- ND ---

Straw

Straw

0.045 Maturity <LOQ

<LOQ 0.01
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Table 5.3.3. Summary of Residues of Trinexapac-Ethyl in/on straw.

TK0044924-12

(MO/2012)

5 Francis

Straw --- -- ND ---

Straw

Straw

0.045 Maturity 0.010

<LOQ 0.01

TK0044924-13

(TX/2012) 6 Presidio

Straw --- -- ND ---

Straw

Straw

0.044 Maturity 0.017

0.023 0.02

TK0044924-14

(TX/2012) 6 Cheniere

Straw --- -- ND ---

Straw

Straw

0.041 Maturity ND

ND

0.005

TK0044924-15

(CA/2012)

10 Koshihikari

Straw --- -- ND --

Straw

0.045

14 PM ND --

Straw 7 PM ND --

Straw

Straw

Maturity ND

ND 0.005

Straw 7 AM ND --

Straw 14 AM ND --

TK0044924-16

(CA/2012) 10 Koshihikari

Straw -- -- ND --

Straw 0.046 Maturity <LOQ

0.024 0.017

 Straw

1 Total Rate = One foliar broadcast application was made at a nominal rate of 0.045 lb ai/A

2 PM = Days prior to maturity, AM = Days after maturity, Maturity = Normal Maturity; PP = Pre-processing

3 LOQ = 0.01 ppm; ND = Not Detected.

4 For calculation of the trial mean, if residues were ND a value of 0.005 (1/2 LOQ) was used, if the value was <LOQ the value

0.01 (LOQ) was used.

Rye: The tolerances on rye was requested based on the November 25, 2009 ChemSAC decision 

that provides an allowance for extrapolating residue data for barley and wheat to additional small 

cereal grains. Since the tolerances are established for cereals (wheat, barley and oats), the 

tolerances for rye is translatable to established tolerances of small cereal grains.

Conclusions:

Rice: The rice field trials are considered scientifically acceptable and are adequate in terms of both 

geographic representation and number. The field portion of the study was adequately documented. 

An acceptable method was used for quantitation of residues in/ on rice. The data are supported by 

adequate storage stability data. In rice grain harvested at PHIs of 51-100 days following a single 

foliar broadcast application of the 2.08 lb ai/gal EC formulation of trinexapac-ethyl made at 0.041-

0.046 lb ai/A, individual sample (and per-trial average) residues of trinexapac-ethyl (determined 

as CGA179500) were <0.01-0.270 ppm (<0.01-0.214 ppm).

In one residue decline trial residues were variable, with the highest residues observed at the 

target PHI. In the second residue decline trial, residues were below the LOQ in/on all samples; 

therefore, residue decline could not be determined.

Rye: no new field trial data were submitted or are required to support the new use and tolerance 

on rye.
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5.3.2 Field Rotational Crops (860.1900)

Confined rotational crop data were submitted, however, field rotational data have not been 

provided. Since the label currently reflects a 30-day PBI for cereal grains, field rotational crop data 

are not required at this time. 

5.3.3 Processed Food and Feed (860.1520)

DER reference

Rice: Syngenta Crop Protection, LLC has submitted a processing study with trinexapac-ethyl on

rice. In two trials conducted in LA and MO during the 2012 growing season, a single foliar 

broadcast spray application of the 2.08 lb ai/gal emulsifiable concentrate (EC) formulation of 

trinexapac-ethyl (Trinexapac-Ethyl EC, A7725M) was made at the BBCH 30-32 (panicle initiation 

or green ring stage) at an exaggerated rate of 0.134-0.135 lb ai/A (~3x the field application rate). 

Applications were made using ground equipment in a spray volume of 10 gal/A. A crop oil 

concentrate (COC) or non-ionic surfactant (NIS) was added to the spray mixture for each trial. The 

study use pattern is summarized in Table 5.3.3 below. Samples of rice grain were harvested at 

maturity at preharvest intervals (PHIs) of 54-91 days and processed into polished rice, hulls, and 

bran using simulated commercial practices. Processing was conducted by GLP Technologies 

(Navasota, TX).

The processing procedure simulated commercial operations of rice production as closely as 

possible to generate the required fraction of rice grain (RAC), polished rice, hulls, and bran. A 

processing flowchart for rice, copied without alteration from MRID 49282807, is presented below 

in Figure 5.3.3.
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FIGURE 5.3.3. Processing Flowchart for Polished Rice, Hulls, and Bran.

Table. 5.3.3A Study Use Pattern.

Location: City, 

State; Year (Trial 

ID)

End-use 

Product1

Method of Application/ 

Timing of Application

Volume

(gal/A)

Rate per 

Application

(lb ai/A)

Retreatment 

Interval 

(days)

Total Rate

(lb ai/A)

Surfactant/ 

Adjuvant2

Washington, LA;

2012 

(TK0044924-10)

2.08 lb 

ai/gal EC

Foliar broadcast; BBCH 

30-32 (panicle initiation 

or green ring stage)

10 0.134 -- 0.134 COC

Fisk, MO; 2012 

(TK0044924-11)

2.08 lb 

ai/gal EC

Foliar broadcast; BBCH 

30-32 (panicle initiation 

or green ring stage)

10 0.135 -- 0.135 NIS

1 End-use product is A7725M, a 2.08 lb ai/gallon emulsifiable concentrate (EC) formulation of trinexapac-ethyl.

2 COC = crop oil concentrate. NIS = non-ionic surfactant.

Samples were shipped at ambient temperatures from the testing facility to the processing facility, 

where they were placed into frozen storage and remained frozen during shipping and storage prior 

to processing, preparation and analysis. The maximum storage interval for samples was 446 days 

(14.7 months) for pre-processing rice grain, 248 days (8.2 months) for polished rice and hulls, and 

250 days (8.2 months) for bran from harvest/processing to extraction. Samples were analyzed 

within 2-4 days of extraction. Processing took place within 185-197 days (6.1-6.5 months) of 

harvest. Storage stability data are available indicating that residues of CGA179500 were stable 

when stored frozen for up to 24 months in/on wheat grain. The available storage stability data are 
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

Page 24 of 31

adequate to support the storage conditions and durations for rice grain (RAC) samples from the 

submitted rice processing study. Storage stability data are available indicating that residues of 

CGA179500 were stable when stored frozen for up to 24 months in/on small cereal grains.

Therefore the available storage stability data are adequate to supports the storage duration and 

stability of the processed commodities of rice. 

RAC and processed commodities were analyzed using Syngenta Method GRM020.01A, which 

was discussed in enforcement analytical method Section (section 2.2.1) and has been validated as 

an acceptable data collection method.

In rice grain harvested at PHIs of 54-91 days following a single foliar broadcast application a 2.08 

lb ai/gal EC formulation of trinexapac-ethyl at an exaggerated rate of 0.134-0.135 lb ai/A (~3x the 

field application rate), residues of trinexapac-ethyl determined as trinexapac acid (CGA179500) 

were 0.11-0.63 ppm. Residues of trinexapac ethyl, converted to parent equivalents, were 0.11-1.04 

ppm in polished rice, 0.025-0.37 ppm in hulls, and 0.63-2.81 ppm in bran.

The processing data indicate that residues of trinexapac acid concentrate in polished rice (1.0-1.6x, 

median processing factor 1.3x) and bran (4.4-5.8x, median processing factor 5.1x), but do not 

concentrate in hulls (0.2-0.6x, median processing factor 0.4x).

The observed processing factors calculated in this study were less than the maximum theoretical

concentration factors of 7.7x for rice bran and 5.0x for rice hulls (based on separation of 

components; OCSPP 860.1520, Table 3).

A summary of the residues data from rice processing study is presented in the following tables.

Table. 5.3.3C. Residue Data from Rice Processing Study with Trinexapac-ethyl as CGA179500

Commodity Analyte Residues 1

(ppm)[Average]

Processing Factor2 Median Processing 

Factor3

Washington, LA; 2012 (TK0044924-10)

Rice grain (RAC) CGA179500 0.87, 0.79, 0.25 [0.63] -- --

Polished rice CGA179500 1.04 1.6x 1.3x

Hulls CGA179500 0.37 0.6x 0.4x

Bran CGA179500 2.81 4.4x 5.1x

Fisk, MO; 2012 (TK0044924-11)

Rice grain (RAC) CGA179500 0.11, 0.11, 0.11 [0.11] --

Polished rice CGA179500 0.11 1.0x

Hulls CGA179500 0.025 0.2x

Bran CGA179500 0.63 5.8x

1 The method determines residues of trinexapac-ethyl as CGA179500. Residues of CGA179500 were converted to parent 

equivalents by the study reviewer using a molecular weight conversion factor of 1.125 (MW trinexapac-ethyl 252.26/MW 

trinexapac acid 224.21).

2 Processing Factor = [Measured residue for analyte in the processed fraction] / [Measured residue for analyte in the RAC]. A 

separate processing factor is calculated for each processed commodity.

3 Median (and also mean in this case) of processing factors for both sites, determined for each matrix.

Conclusions
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

Page 25 of 31

The submitted processing data are supported by storage stability data and were generated using a 

validated enforcement method. The processing data indicate that residues of trinexapac acid

concentrate in polished rice (1.0-1.6x, median processing factor 1.3x) and bran (4.4-5.8x, median 

processing factor 5.1x), but do not concentrate in hulls (0.2-0.6x, median processing factor 0.4x).

The observed processing factors calculated in this study were less than the maximum theoretical 

concentration factors of 7.7x for rice bran and 5.0x for rice hulls (based on separation of 

components; OCSPP 860.1520, Table 3). 

5.3.4 Meat, Milk, Poultry and Eggs 

There are no livestock feed items associated with this petition; therefore a discussion of the 

magnitude of residues in livestock commodities, as well as the need for livestock tolerances and 

analytical methods is not pertinent to this discussion.

5.3.5. Food Handling (860.1460)

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

5.3.6 Water, Fish, and Irrigated Crops (860.1400)

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

5.4 Food Residue Profile

Available metabolism data shows that trinexapac-ethyl does translocate to the growing shoot when 

applied as a foliar application. Trinexapac-ethyl is used at relatively low application rates, and the 

submitted field trial studies demonstrate that when applied at post-emergence, quantifiable 

residues are seen in cereal grains treated up to 51-100 days before harvest. Also, data from the 

confined rotational crop study indicate that trinexapac-ethyl residues are detected (lettuce and 

wheat) at the 30-day plant back interval. Quantifiable residues were only seen in livestock at low 

levels in the animal feedstuff associated with this action. 

6.0 Tolerance Derivation

The Agency’s Organization for Economic Cooperation and Development (OECD) MRL calculator 

was used to determine appropriate tolerance levels for the combined residues of trinexapac ethyl 

and its alcohol metabolite (rice grain 0.4 and rice straw 0.07 ppm). The results from the spreadsheet 

calculator (appendix C) support the proposed tolerances for both rice straw and grain. The 

processing data supports the proposed tolerance for rice bran at 1.5 ppm. 

For rye, the registrant proposed tolerances by extrapolating residue data for barley. HED concurs 

that tolerances can be established by translation from other cereal grains, however, since tolerances 
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

Page 26 of 31

for wheat commodities are higher than tolerances for barley commodities, tolerances for rye 

commodities were translated from the higher wheat values.

7.0 ChemSAC Reference

Trinexapac ethyl is not a new active ingredient; therefore. ChemSAC review is not required for 

this action. 
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

Page 27 of 31

Appendix A. Field Trial Geographic Distribution

NAFTA

Growing Region

Trials Completed and

Submitted Trial No. Trial Location

4* 11*

TK0044924-01 Proctor, AR

TK0044924-02 Pollard, AR

TK0044924-03 Cheneyville, LA

TK0044924-04 Ville Platte, LA

TK0044924-05* Washington, LA

TK0044924-06 Proctor, AR

TK0044924-07* Washington, LA

TK0044924-08* Washington, LA

TK0044924-09 Proctor, AR

TK0044924-10 Washington, LA

TK0044924-11 Fisk, MO

5 1 TK0044924-12 Fisk, MO

6 2

TK0044924-13 East Bernard, TX

TK0044924-14 East Bernard, TX

10 2

TK0044924-15 Porterville, CA

TK0044924-16 Porterville, CA

Total 16

*

Even though 16 field trials were submitted from zone 4, HED determined that trial TK0044924-05, 07 and 08 are considered as replication due to same variety, 

application dates and same spray volume and same adjuvant. 
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

Page 28 of 31

Appendix B. International Residue Limits Table

Trinexapac ethyl (PC Code: 112602)

Summary of US and International Tolerances and Maximum Residue Limits 

Residue Definition:

US Canada Mexico2 Codex3

40 CFR 180. 662:

Plants: Trinexapac-ethyl, ethyl 4-

(cyclopropylhydroxymethylene)-3,5-

dioxocyclohexanecarboxylate and 

associated metabolite trinexpac, 4-

(cyclopropylhydroxymethylene)-3,5-

dioxocyclohexanecarboxylic acid. 

Commodity1 Tolerance (ppm) /Maximum Residue Limit (mg/kg)

US Canada Mexico2 Codex

Rice, grain 0.4

Rice, straw 0.07

Rice, bran 1.7

Rice, wild, grain 0.4

Rye, bran 2.5

Rye, grain 2.0

Rye, hay 0.8

Rye, straw 0.4

Completed: Completed: M. Negussie; 11/07/14

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.
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

Page 29 of 31

Appendix C. OECD MRL Calculator Rice Grain

Tolerance values were calculated by the OECD MRL Calculator using data from the field trial

residue study (MRID 49282807) for a 2.08 lb ai/A Trinexapac ethyl.

Trinexapacethyl

Rice 

Grain

NAFTA

2.08 lb 

ai/gal

Trinexapac-ethyl

Residues 

(mg/kg)

Rice Grain

0.064 NAFTA

0.056 2.08 lb ai/gal

0.058

0.025 Total number of data (n) 14

0.214 Percentage of censored data 0%

0.024 Number of non-censored data 14

0.082 Lowest residue 0.010

0.197 Highest residue 0.214

0.037 Median residue 0.057

0.039 Mean 0.073

0.113 Standard deviation (SD) 0.063

0.019 Correction factor for censoring (CF) 1.000

0.010

0.083 Proposed MRL estimate

- Highest residue 0.214

- Mean + 4 SD 0.325

- CF x 3 Mean 0.219

Unrounded MRL 0.325

Rounded MRL 0.4
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

Page 30 of 31

OECD MRL Calculator Rice Grain Rice Straw 

Tolerance values were calculated by the OECD MRL Calculator using data from the field trial

residue study (MRID 49282807) for a 2.08 lb ai/A Trinexapac ethyl.

Trinexapacethyl

Rice 

Straw

NAFTA

2.08 lb 

ai/gal

Trinexapac-ethyl

Residues 

(mg/kg)

Rice Straw

0.015 NAFTA

0.008 2.08 lb ai/gal

0.016

0.005 Total number of data (n) 14

0.034 Percentage of censored data 0%

0.008 Number of non-censored data 14

0.012 Lowest residue 0.005

0.045 Highest residue 0.045

0.010 Median residue 0.011

0.010 Mean 0.015

0.020 Standard deviation (SD) 0.012

0.005 Correction factor for censoring (CF) 1.000

0.005

0.017 Proposed MRL estimate

- Highest residue 0.045

- Mean + 4 SD 0.061

- CF x 3 Mean 0.044

Unrounded MRL 0.061

Rounded MRL 0.07
Trinexapac-Ethyl Summary of Analytical Chemistry and Residue Data DP Number: D424894

Page 31 of 31

REFERENCES

Subject: M.S., (2014). Trinexapac-Ethyl EC (A7725M) -Magnitude of the Residues in or 

on Rice.

From: Nakia Smith

Date: 10/29/08

MRIDs: 49282807

DP#: 402207

Subject: Trinexapac-ethyl: Revised Application for the Section 3 Registration Action on 

Cereal Grains and Sugarcane (PP#0F7720) and Grasses Grown for Seed 

(PP#0F7719). Summary of Analytical Chemistry and Residue Data.

From: Sheila Piper

To: Bethany Benbow/ Kathryn Montague

Date: 05/23/2012

MRIDs: 42233942

DP#: 390121

Subject: Trinexapac-ethyl; Report of the Residues of Concern Knowledgebase 

Subcommittee (ROCKS).

From: Elizabeth Holman/ Christine L. Olinger

Date: 07/12/2011

MRIDs: NA

DP#: 377921

Subject: Trinexapac-ethyl: Human Health Risk Assessment for the Section 3 

Registration Action on Cereal Grains, Sugarcane, and Grasses Grown for Seed.

From: Sheila Piper

To: Bethany Benbow/ Kathryn Montague

Date: 11/23/2011

MRIDs: NA
Trinexapac-ethyl [PC Code l 12602)/ SyngentaCrop Protection, LLC 

Processed Food/Feed-Rice 

Primary Evaluator 

-~ Date: 10-MAR-2015 

Approved by 

B.7.7 

B.7.7.1 

B.7.7.2 

8 .7.7.3 

B.7.7.3.1 

umitra Bose Biswas, Chemist 

Risk Assessment Branch VI (RAB VI) 

Health Effects Division (RED (7509P) 

Sheila Piper, Senior Chemist 

RABY[, HED (7509P) 

Date: 10-MAR-2015 

Effects of Industrial Processing and/or Household Preparation 

(Annex IIA 6.5; Annex IIIA 8.5) 

Nature of the Residue 

(Annex IIA 6.5.1; Annex IIIA 8.5.1)-Not a data requirement in North America 

Distribution of the Residue in Peel/Pulp (Annex IIA 6.5.2; Annex IHA 8.5.2)-

To be included if available. 

Magnitude of Residues on Set of Representative Processes 

(Annex IIA 6.5.3; Annex IHA 8.5.3) 

Rice 

Document ID: MRID No. 49282807 

PMRA No. Not Available 

Report: Smith, N. (2014) Trinexapac-Ethyl EC (A7725M) - Magnitude of the 

Residues in or on Rice. Final Report. OLP Study Number: TK0044924, 

North Coast Study Number: 110.046. Unpublished study prepared by 

Syngenta Crop Protection, LLC. 222 p. 

Guidelines: EPA OCSPP Harmonized Test Guideline 860.1520 Processed Food/Feed 

(August 1996) 

PMRA Regulatory Directive DIR98-02 - Residue Chemistry Guidelines, 

Section 10 - Processed Food/Feed 

OECD Guideline 508 Magnitude of the Pesticide Residues in Processed 

Commodities (October 2008) 

GLP Compliance: No deviations from regulatory requirements were reported which would 

have an impact on the validity of the study. 

Acceptability: The study is tentatively considered scientifically acceptable pending 

submission and evaluation of storage stability data for processed 

commodities. The acceptability of this study for regulatory purposes is 

addressed in the forthcoming U.S. EPA Residue Chemistry Summary 

Document, DP# 424894. 

Evaluator: Sumitra Bose Biswas 

EPA MRID #: 49282807 

PMRA # of document: Not Available Page J of8 
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Note: This Data Evaluation Record (DER) was originally prepared under contract by Versar, Inc. (6850 Versar Center, 

Springfield, VA 22151; submitted 9/22/14). The DER has been reviewed by HED and revised to reflect current Office of 

Pesticide Programs (OPP) policies.

EXECUTIVE SUMMARY

Syngenta Crop Protection, LLC has submitted a processing study with trinexapac-ethyl on rice. 

In two trials conducted in LA and MO during the 2012 growing season, a single foliar broadcast 

spray application of the 2.08 lb ai/gal emulsifiable concentrate (EC) formulation of trinexapacethyl (Trinexapac-Ethyl EC, A7725M) was made at the BBCH 30-32 (panicle initiation or green 

ring stage) at an exaggerated rate of 0.134-0.135 lb ai/A (~3x the field application rate). 

Applications were made using ground equipment in a spray volume of 10 gal/A. A crop oil 

concentrate (COC) or non-ionic surfactant (NIS) was added to the spray mixture for each trial. 

Samples of rice grain were harvested at maturity at preharvest intervals (PHIs) of 54-91 days and 

processed into polished rice, hulls, and bran using simulated commercial practices. Processing 

was conducted by GLP Technologies (Navasota, TX). Adequate descriptions were provided of the 

processing procedures including material balance summaries.

Samples were shipped at ambient temperatures from the testing facility to the processing facility, 

where they were placed into frozen storage and remained frozen during shipping and storage prior 

to processing, preparation and analysis. The maximum storage interval for samples was 446 days 

(14.7 months) for pre-processing rice grain, 248 days (8.2 months) for polished rice and hulls, and 

250 days (8.2 months) for bran from harvest/processing to extraction. Samples were analyzed 

within 2-4 days of extraction. Processing took place within 185-197 days (6.1-6.5 months) of 

harvest. Storage stability data are available indicating that residues of CGA179500 were stable 

when stored frozen for up to 24 months in/on wheat grain. No storage stability data are available 

for CGA179500 in processed commodities. The available storage stability data are adequate to 

support the storage conditions and durations for processed commodities of rice

Samples were analyzed for residues of trinexapac-ethyl determined as CGA179500 using 

Syngenta Analytical Method GRM020.01A (with minor modifications), a high performance liquid 

chromatography method with tandem mass spectrometric detection (LC/MS/MS). The limit of 

quantitation (LOQ, determined as the lowest level of method validation, LLMV) was 0.01 ppm. 

The method does not provide for conversion of residues of CGA179500 to parent equivalents; 

therefore quantifiable residues of CGA179500 were converted to parent equivalents by the study 

reviewer using a molecular weight conversion factor of 1.125 (MW trinexapac-ethyl 252.26/MW 

trinexapac acid 224.21). Acceptable concurrent recovery data were reported for rice grain (RAC) 

and polished grain samples at fortification levels of 0.01-1.5 ppm, for hulls at fortification levels 

of 0.01-0.5 ppm, and for bran at fortification levels of 0.01-3.0 ppm, thus validating the method. 

Prior to analysis of samples, the method was validated on rice grain at two fortification levels of 

CGA179500 (0.010 and 1.0 ppm). The fortification levels were adequate to bracket expected 

residue levels.
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In rice grain harvested at PHIs of 54-91 days following a single foliar broadcast application a 2.08 

lb ai/gal EC formulation of trinexapac-ethyl at an exaggerated rate of 0.134-0.135 lb ai/A (~3x the 

field application rate), residues of trinexapac-ethyl (determined as CGA179500) were 0.11-0.63 

ppm. Residues of CGA179500, converted to parent equivalents, were 0.11-1.04 ppm in polished 

rice, 0.025-0.37 ppm in hulls, and 0.63-2.81 ppm in bran.

The processing data indicate that residues of CGA179500 concentrate in polished rice (1.0-1.6x, 

median processing factor 1.3x) and bran (4.4-5.8x, median processing factor 5.1x), but do not 

concentrate in hulls (0.2-0.6x, median processing factor 0.4x).

The observed processing factors calculated in this study were less than the maximum theoretical 

concentration factors of 7.7x for rice bran and 5.0x for rice hulls (based on separation of 

components; OCSPP 860.1520, Table 3).

STUDY DEFICIENCIES

Under the conditions and parameters used in the study, the processed commodity residue data for 

TCP are tentatively classified as scientifically acceptable, pending the submission and evaluation 

of storage stability data for processed rice commodities.

I. MATERIALS AND METHODS

A. MATERIALS

Table B.7.7.3.1-1. Nomenclature for Trinexapac-ethyl and Metabolite of Interest.

Common name Trinexapac-ethyl

Identity Ethyl 4-(cyclopropylhydroxymethylene)-3,5-dioxocyclohexanecarboxylate

CAS no. 95266-40-3

Company experimental name CGA163935

Other synonyms (if applicable) Not applicable

Metabolite CGA179500

Identity 4-(cyclopropylhydroxymethylene)-3,5-dioxocyclohexanecarboxylic acid

CAS no. 104273-73-6

Company experimental name See above

Other synonyms (if applicable) Trinexapac acid
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Table B.7.7.3.1-1. Nomenclature for Trinexapac-ethyl and Metabolite of Interest.

B. Study Design

1. Test Procedure

Location and detailed use pattern for the trial is provided in Table B.7.7.3.1-2. 

Table B.7.7.3.1-2. Study Use Pattern.

Location: City, 

State; Year (Trial 

ID)

End-use 

Product1

Method of Application/ 

Timing of Application

Volume

(gal/A)

Rate per 

Application

(lb ai/A)

Retreatment 

Interval 

(days)

Total Rate

(lb ai/A)

Surfactant/ 

Adjuvant2

Washington, LA; 

2012 

(TK0044924-10)

2.08 lb 

ai/gal EC

Foliar broadcast; BBCH 

30-32 (panicle initiation 

or green ring stage)

10 0.134 -- 0.134 COC

Fisk, MO; 2012 

(TK0044924-11)

2.08 lb 

ai/gal EC

Foliar broadcast; BBCH 

30-32 (panicle initiation 

or green ring stage)

10 0.135 -- 0.135 NIS

1 End-use product is A7725M, a 2.08 lb ai/gallon emulsifiable concentrate (EC) formulation of trinexapac-ethyl.

2 COC = crop oil concentrate. NIS = non-ionic surfactant.

Bulk samples of untreated and treated rice grain were harvested at maturity and transferred to the 

processing facility for preparation of polished rice, hulls and bran. Rice was processed using 

simulated industrial practices.

Sample Handling and Preparation

Single control and treated bulk samples of rice grain (~500 lb) were collected from each plot at 

maturity 54-91 days after application. The bulk rice samples were delivered by site personnel or 

shipped at ambient temperature to the processing facility, GLP Technologies (Navasota, TX) 

within 3 days of harvest. Samples were frozen upon receipt at the processing facility, and

processed fractions were stored frozen at ≤10 °F (≤-12 C). Processing took place within 184-197

days (6.1-6.5 months) of harvest. Within 5-8 days after processing, RAC and processed fractions 

were shipped via freezer truck to Syngenta Crop Protection, Inc. (Greensboro, NC), for sample 

preparation (grinding with dry ice). At Syngenta, samples were stored in a freezer at <-10 °C from 

receipt until removal for preparation, and between preparation and shipment for analysis.

Subsamples were shipped frozen from Syngenta to North Coast Laboratories (NCL; Arcata, CA); 

the time from shipment to Syngenta to receipt at NCL was 84 days (2.8 months). Samples were 

stored frozen (≤–20 C) upon receipt at NCL prior to and after analysis.
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Sample Processing

The processing procedure simulated commercial operations of rice production as closely as 

possible to generate the required fraction of rice grain (RAC), polished rice, hulls, and bran, with 

some variations to commercial methods. Adequate descriptions of processing procedures were 

provided, including material balance summaries. A processing flowchart for rice, copied without 

alteration from MRID 49282807, is presented below in Figure B.1.

FIGURE B.1. Processing Flowchart for Polished Rice, Hulls, and Bran.

2. Description of Analytical Procedures

Samples were analyzed for residues of trinexapac-ethyl determined as CGA179500 by LC/MS/MS 

using Syngenta Analytical Method GRM020.01A “Analytical Method for the Determination of 

Residues of Trinexapac-Ethyl as CGA179500 in Crops by LC-MS/MS,” with minor 

modifications. This method was previously reviewed under DP# 378491 (S. Piper, 11/23/2011) 

in conjunction a crop field trial submission for barley grain (48043702.der).

Briefly, samples were refluxed with acetonitrile (ACN)/1 N HCl (80:20, v:v). An aliquot of the 

extract was applied to a C8 solid phase extraction (SPE) cartridge, and residues were eluted with 

0.5% formic acid:ACN (70:30 v:v). The eluate was adjusted to volume for LC/MS/MS 

3.3.2 Processing Flow Diagram

An example of the Rice processing flow and procedures used in this study is presented

below.

3.3.3 Processed Commodity Sample Handling and Shipping

Processed commodities were stored frozen until shipment to Syngenta Crop Protection, LLC,

Greensboro, NC.

3.4 Analytical Procedures

3.4.1 Reference Substances

Reference substances were used for fortification of method recovery/verification samples and

for calibration to quantify the residues in the samples. Standards were prepared as outlined

in the analytical methods and stored in the refrigerator when not in use. The reference

standard information, as required by 40 CFR Part 160.185(a)(4), as well as representative

LC-MS/MS chromatograms and typical calibration curves, can be found in the Analytical

Phase Report (Appendix 4).
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analysis. The method does not provide for conversion of residues of CGA179500 to parent 

equivalents; therefore quantifiable residues of CGA179500 were converted to parent equivalents 

by the study reviewer using a molecular weight conversion factor of 1.125 (MW trinexapac-ethyl 

252.26/MW trinexapac acid 224.21). 

The LOQ (determined as the LLMV) was 0.01 ppm for CGA179500. The limit of detection 

(LOD) was not reported.

II. RESULTS AND DISCUSSION

Method performance was evaluated during method validation and by use of concurrent recovery 

samples. For method validation, untreated samples of rice grain were fortified with CGA179500

at 0.01 and 1.0 ppm, three samples each, and individual recoveries (and overall standard deviation) 

were 97-122% (8.2%). For concurrent recovery, untreated samples of rice grain were fortified at 

0.01 and 0.10 ppm, six samples each, and individual recoveries (and overall standard deviation) 

were 78-123% (12%). For concurrent recovery of processed commodities, one sample of each 

matrix (pre-processed rice grain, polished rice, hulls and bran) was fortified with CGA179500 at 

0.01 and 0.10 ppm (as well as 1.5 ppm for pre-processed grain and polished rice, 0.5 ppm for hulls 

and 3.0 ppm for bran), and recoveries were 94-98%, 100-110%, 76-79%, and 72-98%, 

respectively, with an overall standard deviation of 12%. All recoveries were generally within the 

acceptable range of 70% to 120%.

The method was considered valid for the analysis of trinexapac-ethyl residues in rice matrices. The 

fortification levels did bracket the measured residues. Concurrent recoveries were corrected for 

apparent residues in controls.

The detector response was linear (1x weighting), with coefficient of determination, r

2 ≥0.9946

within the range of 0.0067-0.333 ppm. Representative chromatograms of control samples, 

fortified samples and treated samples were provided. The control chromatograms generally had 

no peaks of interest above the chromatographic background. The fortified sample 

chromatograms contained only the analyte of interest, and peaks were symmetrical and well 

defined. Apparent residues in controls were below the LOQ (<0.01 ppm). The reported residue 

values were not corrected for apparent residues in controls.

Table B.7.7.3.1-3. Summary of Procedural/Concurrent Recoveries of Trinexapac-ethyl from Rice Matrices.

Matrix Analyte Fortification 

Level (ppm)

Recoveries

(%)

Mean ± Std. Dev.

(%)

Not applicable

The pre-processing rice grain (RAC) samples were stored frozen a maximum of 446 days (14.7

months) from harvest to extraction, and processed samples were stored frozen a maximum of 

250 days (8.2 months) from processing to extraction (Table B.7.7.3.1-4). Samples were 

analyzed within 2-4 days of extraction. Processing took place within 184-197 days (6.1-6.5 

months) of harvest.

The available freezer storage stability data indicate that residues of trinexapac-ethyl as 

CGA179500 were stable when stored frozen in wheat (grain) for 24 months (45898903.der). 
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The available storage stability data are adequate to support the storage conditions and durations 

processed commodities of rice.

Table B.7.7.3.1-4. Summary of Storage Conditions1.

Matrix Storage Temperature (°C) Actual Storage 

Duration

(days/months)

Interval of Demonstrated Storage Stability

Rice grain (RAC) Maintained frozen at 

processor (≤-12 C), 

preparation facility (<-10 C) 

and analytical laboratory (≤-

20 C)

432-446 (14.2-14.7) Residues of CGA179500 were stable when 

stored frozen in wheat grain for up to 24 months2

Polished rice 246-248(8.1-8.2) No storage stability data are available for 

Hulls 246 CGA179500 in processed commodities. -248 (8.1-8.2)

Bran 248-250 (8.2)

1

Interval from harvest/processing to extraction. Samples were analyzed within 2-4 days of extraction.

2 DP# 378491 (S. Piper, 11/23/2011), 45898903.der.

Residues found in samples and processing factors are given in Table B.7.7.3.1-5. In rice grain 

harvested at PHIs of 54-91 days following a single foliar broadcast application a 2.08 lb ai/gal 

EC formulation of trinexapac-ethyl at an exaggerated rate of 0.134-0.135 lb ai/A (~3x the field 

application rate), residues of trinexapac-ethyl (determined as CGA179500) were 0.11-0.63 ppm. 

Residues of CGA179500, converted to parent equivalents, were 0.11-1.04 ppm in polished rice, 

0.025-0.37 ppm in hulls, and 0.63-2.81 ppm in bran.

The processing data indicate that residues of CGA179500 concentrate in polished rice (1.0-1.6x, 

median processing factor 1.3x) and bran (4.4-5.8x, median processing factor 5.1x), but do not 

concentrate in hulls (0.2-0.6x, median processing factor 0.4x).

Table B.7.7.3.1-5. Residue Data from Rice Processing Study with Trinexapac-ethyl as CGA179500

Commodity Analyte Residues 1

(ppm)[Average]

Processing Factor2 Median Processing 

Factor3

Washington, LA; 2012 (TK0044924-10)

Rice grain (RAC) CGA179500 0.87, 0.79, 0.25 [0.63] -- --

Polished rice CGA179500 1.04 1.6x 1.3x

Hulls CGA179500 0.37 0.6x 0.4x

Bran CGA179500 2.81 4.4x 5.1x

Fisk, MO; 2012 (TK0044924-11)

Rice grain (RAC) CGA179500 0.11, 0.11, 0.11 [0.11] --

Polished rice CGA179500 0.11 1.0x

Hulls CGA179500 0.025 0.2x

Bran CGA179500 0.63 5.8x

1 The method determines residues of trinexapac-ethyl as CGA179500. Residues of CGA179500 were converted to parent 

equivalents by the study reviewer using a molecular weight conversion factor of 1.125 (MW trinexapac-ethyl 252.26/MW 

trinexapac acid 224.21).

2 Processing Factor = [Measured residue for analyte in the processed fraction] / [Measured residue for analyte in the RAC]. A 

separate processing factor is calculated for each processed commodity.

3 Median (and also mean in this case) of processing factors for both sites, determined for each matrix.
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III. CONCLUSIONS

The rice processing study is tentatively considered scientifically acceptable pending submission 

and evaluation of a storage stability study for processed commodities. In rice grain harvested at 

PHIs of 54-91 days following a single foliar broadcast application a 2.08 lb ai/gal EC 

formulation of trinexapac-ethyl at an exaggerated rate of 0.134-0.135 lb ai/A (~3x the field 

application rate), residues of trinexapac-ethyl (determined as CGA179500) were 0.11-0.63 ppm. 

Residues of CGA179500, converted to parent equivalents, were 0.11-1.04 ppm in polished rice, 

0.025-0.37 ppm in hulls, and 0.63-2.81 ppm in bran.

The processing data indicate that residues of CGA179500 concentrate in polished rice (1.0-1.6x, 

median processing factor 1.3x) and bran (4.4-5.8x, median processing factor 5.1x), but do not 

concentrate in hulls (0.2-0.6x, median processing factor 0.4x).

Adequate storage stability data are available to support sample storage durations and conditions 

for processed commodities of rice for CGA179500. 

An acceptable method was used for residue quantitation.

The observed processing factors calculated in this study were less than the maximum theoretical 

concentration factors of 7.7x for rice bran and 5.0x for rice hulls (based on separation of 

components; OCSPP 860.1520, Table 3). 

REFERENCES

DP# 378491 (S. Piper, 11/23/2011); 48043702.der and 45898903.der
Trinexapac-ethyl [PC Code 112602]/Syngenta Crop Protection, LLC. 

Magnitude of Residue- Rice 

Primary Evaluator 

Approved by 

B.7.6 

B.7.6.1 

B.7.6.1.1 

Sumitra Bose Biswas, Chemist 

Risk Assessment Branch VI (RABVI) 

th Effects Division (HED 7509P) 

eila Piper, Se ·or Chemist 

RABVI, HED 7509P) 

Residues Resulting from Supervised Trials 

(Annex IIA 6.3; Annex IllA 8.3) 

Residues in Target Crops 

Rice 

Document ID: MRID No. 49282807 

PMRA No. Not Available 

Date: 10-MAR-2015 

Date: IO-MAR-2015 

Report: Smith, N. (2014) Trinexapac-Ethyl EC (A7725M) - Magnitude of the 

Residues in or on Rice. Final Report GLP Study Number: TK0044924, 

North Coast Study Number: 110.046. Unpublished study prepared by 

Syngenta Crop Protection, LLC. 222 p. 

Guidelines: EPA OCSPP Harmonized Test Guideline 860.1500 Crop Field Trials 

(August 1996) 

PMRA Regulatory Directive DIR98-02 - Residue Chemistry Guidelines, 

Section 9 - Crop Field Trials 

PMRA Regulatory Directive DIR2010-05 - Revisions to the Residue 

Chemistry Crop Field Trial Requirements 

OECD Guideline 509 Crop Field Trial (September 2009) 

GLP Compliance: No deviations from regulatory requirements were reported which would 

have an impact on the validity of the study. 

Acceptability: The study is considered scientifically acceptable. The acceptability of this 

study for regulatory purposes is addressed in the forthcoming U.S. EPA 

Residue Chemistry Summary Document, DP# 424894. 

Evaluator: Sumitra Bose Biswas 

Note: This Data Evaluation Record (DER) was originally prepared under contract by Versar, Inc. (6850 Vcrsar Center, 

Springfield, VA 2215 1; submitted 9/22/14 ). The DER has been reviewed by HED and revised to reflect current Office of 

Pesticide Programs (OPP) policies. 

EPA MRID #: 49282807 

Page I of9 

PMRA # of document: Not found 
Trinexapac-ethyl [PC Code 112602]/Syngenta Crop Protection, LLC.

Magnitude of Residue- Rice

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EPA MRID #: 49282807

PMRA # of document: Not found

Page 2 of 9

EXECUTIVE SUMMARY

Syngenta Crop Protection, LLC has submitted field trial data for trinexapac-ethyl on rice from 14

field trials conducted in the United States during the 2012 growing season in the North American 

Free Trade Agreement (NAFTA) Growing Zones 4 (AR; 4 trials, LA; 4 trials, MO; 1 trial), 5 

(MO; 1 trial), 6 (TX, 2 trials) and 10 (CA; 2 trials). HED has concluded that 3 trials conducted 

in Zone 4 should be considered replicates. This decision is reflected in the total trial count 

above. 

Each trial consisted of one untreated plot and one treated plot. Each treated plot received a 

single foliar broadcast spray application of the 2.08 lb ai/gal emulsifiable concentrate (EC) 

formulation of trinexapac-ethyl (Trinexapac-Ethyl EC, A7725M) made at BBCH 30-32 (panicle 

initiation or green ring stage) at 0.041-0.046 lb ai/A/application. Applications were made using 

ground equipment in spray volumes of 2.4-10 gal/A. A nonionic surfactant (NIS) or crop oil 

concentrate (COC) was included in the spray mixtures for all applications. Samples of rice grain 

and straw were harvested at maturity at preharvest intervals (PHIs) of 51-100 days. Rice straw is 

no longer considered a significant livestock feed item and is not further addressed herein. At two 

trials (AR trial -09 and CA trial -15), additional samples were collected to monitor residue 

decline 7 and14 days before and after normal crop harvest; PHIs were 65, 72, 79, 85 and 94 days 

for trial -09 and 85, 92, 99, 106 and 113 days for trial-15.

All samples were maintained frozen at the testing and sample preparation facilities, during 

shipment to the analytical laboratory, and remained frozen until analysis. The maximum storage 

interval for rice grain samples between harvest and extraction was 365 days (12.0 months). 

Samples were analyzed within 1-3 days of extraction. Storage stability data are available 

indicating that residues of CGA179500 were stable when stored frozen for up to 24 months in/on 

wheat grain. These data are adequate to support sample storage durations and conditions.

Samples were analyzed for residues of trinexapac-ethyl determined as CGA179500 using 

Syngenta Analytical Method GRM020.01A (with minor modifications), a high performance 

liquid chromatography method with tandem mass spectrometric detection (LC/MS/MS). The 

limit of quantitation (LOQ, determined as the lowest level of method validation, LLMV) was 

0.01 ppm. The method does not provide for conversion of residues of CGA179500 to parent 

equivalents; therefore quantifiable residues of CGA179500 were converted to parent equivalents 

by the study reviewer using a molecular weight conversion factor of 1.125 (MW trinexapac-ethyl 

252.26/MW trinexapac acid 224.21). Acceptable method validation and concurrent recovery 

data were reported for rice grain fortified with CGA179500 at 0.01-1.0 ppm, thus validating the 

method. The fortification levels were adequate to bracket expected residue levels.

In rice grain harvested at PHIs of 51-100 days following a single foliar broadcast application of 

the 2.08 lb ai/gal EC formulation of trinexapac-ethyl at 0.041-0.046 lb ai/A, individual sample 

(and per-trial average) residues of trinexapac-ethyl (determined as CGA179500) were <0.01-

0.270 ppm (<0.01-0.214 ppm).
Trinexapac-ethyl [PC Code 112602]/Syngenta Crop Protection, LLC.

Magnitude of Residue- Rice

--------------------------------------------------------------------------------------------------------------------------------------------

EPA MRID #: 49282807

PMRA # of document: Not found

Page 3 of 9

In one residue decline trial residues were variable, with the highest residues observed at the 

target PHI. In the second residue decline trial, residues were below the LOQ in/on all samples; 

therefore, residue decline could not be determined.

I. MATERIALS AND METHODS

A. MATERIALS

Table B.7.6.1.1-1. Nomenclature for Trinexapac-Ethyl and Metabolite of Interest.

Common name Trinexapac-ethyl

Identity Ethyl 4-(cyclopropylhydroxymethylene)-3,5-dioxocyclohexanecarboxylate

CAS no. 95266-40-3

Company experimental name CGA163935

Other synonyms (if applicable) Not applicable

Metabolite CGA179500

Identity 4-(cyclopropylhydroxymethylene)-3,5-dioxocyclohexanecarboxylic acid

CAS no. 104273-73-6

Company experimental name See above

Other synonyms (if applicable) Trinexapac acid

B. Study Design

1. Test Procedure

Fourteen residue trials were conducted on rice reflecting foliar application at BBCH 30-32 with a 

2.08 lb ai/gal EC formulation during the 2012 growing season (Table B.7.6.1.1-2). 

All trials, except for those listed in the table below, were separated by >20 miles and are 

therefore considered independent (568_Criteria for Independence of Trials 04/23/2013 (EPA and 

PMRA)). The trials separated by <20 miles have been assessed for independence as detailed in 

the table below. HED has determined that three trials (05, 07 and 08) should be considered 

replicate trials. It is noted that since the study predates the guidance concerning field trail 

independence, the criteria specified in the guidance was not strictly adhered to.

OH

O

O

O

O

H3C

O

O

O

HO OH
Trinexapac-ethyl [PC Code 112602]/Syngenta Crop Protection, LLC.

Magnitude of Residue- Rice

--------------------------------------------------------------------------------------------------------------------------------------------

EPA MRID #: 49282807

PMRA # of document: Not found

Page 4 of 9

Independent Trial Determination1

Trial Nos. Differences Decision

01, 06, and 09 Same location

Variety: Roy J (mid-season, long grain) vs. CL 

261 (medium grain) vs. Wells (short-season longgrain, large kernel size)

All separate due to variety, different application 

dates (1-6 days), different spray volume (3-6 

GPA), and/or different adjuvant.

04, 05, 07, 08, 10 Same location (05, 07, 08, 10)

Variety: XL 729 (very early season, long grain, 

tall), CL 151 (very early season, long grain, semidwarf; 19.5K seed/lb), Cocodrie (very early, short 

season, long grain, semi-dwarf, 20.6K seed/lb), 

Cypress (08 and 10; early, long-grain, semi-dwarf, 

19.1K seed/lb)

04 separate due to variety (tall vs. semi-dwarf);

10 separate due to different application date (20 

days).

05, 07, 08: Replicates due to similar variety (all 

semi dwarf), same application dates, spray 

volume and same adjuvant.

11 and 12 Zone: 4 vs. 5 Separate due to Zone

13 and 14 Same location

Variety: Presidio (early season, long grain, semidwarf) vs. Cheniere (very early season, long grain, 

semi-dwarf, hi yield).

No other differences in criteria

Separates due to the varieties and different 

application date (8 days).

15 and 16 Same location and variety

No other differences in criteria

Residues: <0.01 vs. 0.074 ppm

Separate due to different residues

1 All assessments are based on the replicate trial guidance presented in draft memo 568_Criteria for Independence of Trials 

04/23/2013 (EPA and PMRA) and have been approved by HED; since the study predates the guidance, the criteria specified in 

the guidance was not strictly adhered to. 

Table B.7.6.1.1-2. Trial Numbers and Geographical Locations.

Crop No. 

Trials

NAFTA Growing Zone

Total

1 2 3 4 5 6 7 8 9 10 11 12

Rice Sub. 9

2 1 2 2 14

Req.1 11/7 1/1 2/2 2/2 16/12

1 As per Table 5 of 860.1500 for rice, the second number reflects a 25% reduction in the number of field trials allowed for the 

crop as a representative commodity in support of a crop group/subgroup tolerance or when application results in no quantifiable 

residues.

2

 HED has determined that three trials conducted in Zone 4 are replicate trials.

Locations and detailed use patterns for the trials are provided in Table B.7.6.1.1-3. 

Table B.7.6.1.1-3. Study Use Pattern.

Location: City, 

State; Year (Trial 

ID)

End-use 

Product1

Method of Application/ Timing of 

Application

Volume

gal/A

Rate per 

Application

lb ai/A

Retreatment 

Interval 

(days)

Total 

Rate

lb ai/A

Surfactant/ 

Adjuvant2

Proctor, AR; 2012 

(TK0044924-01)

2.08 lb 

ai/gal 

EC

1. 1. Foliar broadcast; BBCH 30-32 3 0.045 NA 0.045 NIS

Pollard, AR; 2012 

(TK0044924-02)

2.08 lb 

ai/gal 

EC

1. 1. Foliar broadcast; BBCH 30-32 5 0.045 NA 0.045 NIS

Cheneyville, LA; 

2012 

(TK0044924-03)

2.08 lb 

ai/gal 

EC

1. Foliar broadcast; BBCH 30-32 9 0.046 NA 0.046 NIS
Trinexapac-ethyl [PC Code 112602]/Syngenta Crop Protection, LLC.

Magnitude of Residue- Rice

--------------------------------------------------------------------------------------------------------------------------------------------

EPA MRID #: 49282807

PMRA # of document: Not found

Page 5 of 9

Table B.7.6.1.1-3. Study Use Pattern.

Location: City, 

State; Year (Trial 

ID)

End-use 

Product1

Method of Application/ Timing of 

Application

Volume

gal/A

Rate per 

Application

lb ai/A

Retreatment 

Interval 

(days)

Total 

Rate

lb ai/A

Surfactant/ 

Adjuvant2

Ville Platte, LA; 

2012 

(TK0044924-04)

2.08 lb 

ai/gal 

EC

1. Foliar broadcast; BBCH 30-32 10 0.046 NA 0.046 NIS

Washington, LA; 

2012 

(TK00044924-05)

2.08 lb 

ai/gal 

EC

1. Foliar broadcast; BBCH 30-32 2.4 0.044 NA 0.044 NIS

Proctor, AR; 2012 

(TK0044924-06)

2.08 lb 

ai/gal 

EC

1. Foliar broadcast; BBCH 31-32 10 0.045 NA 0.045 NIS

Washington, LA; 

2012 

(TK0044924-07)

2.08 lb 

ai/gal 

EC

1. Foliar broadcast; BBCH 30-32 3 0.044 NA 0.044 NIS

Washington, LA; 

2012 

(TK0044924-08)

2.08 lb 

ai/gal 

EC

1. Foliar broadcast; BBCH 30-32 3 0.046 NA 0.046 NIS

Proctor, AR; 2012 

(TK0044924-09)

2.08 lb 

ai/gal 

EC

1. Foliar broadcast; BBCH 31-32) 10 0.045 NA 0.045 NIS

Washington, LA; 

2012 

(TK0044924-10)

2.08 lb 

ai/gal 

EC

1. Foliar broadcast; BBCH 30-32 10 0.046 NA 0.046 COC

Fisk, MO; 2012 

(TK0044924-11)

2.08 lb 

ai/gal 

EC

1. Foliar broadcast; BBCH 30-32 10 0.045 NA 0.045 NIS

Fisk, MO; 2012 

(TK0044924-12)

2.08 lb 

ai/gal 

EC

1. Foliar broadcast; BBCH 30-32 10 0.045 NA 0.045 NIS

East Bernard, TX; 

2012 

(TK0044924-13)

2.08 lb 

ai/gal 

EC

1. Foliar broadcast; BBCH 31-32 8 0.044 NA 0.044 COC

East Bernard, TX; 

2012 

(TK0044924-14)

2.08 lb 

ai/gal 

EC

1. Foliar broadcast; BBCH 31-32 9 0.041 NA 0.041 COC

Porterville, CA; 

2012 

(TK0044924-15)

2.08 lb 

ai/gal 

EC

1. Foliar broadcast; BBCH 30-32 9 0.045 NA 0.045 NIS

Porterville, CA; 

2012 

(TK0044924-16)

2.08 lb 

ai/gal 

EC

1. Foliar broadcast; BBCH 30-32 9 0.046 NA 0.046 NIS

1 End-use product is A7725M, a 2.08 lb ai/gallon emulsifiable concentrate (EC) formulation of trinexapac-ethyl.

2 COC= crop oil concentrate; NIS=non-ionic surfactant. 

Rice was grown and maintained according to typical agricultural practices. Irrigation was used

as needed. Rainfall and temperature data were representative of the growing season. Actual 

temperatures were within average historical values for the residue study period, and the actual 

rainfall average was within the historical rainfall average.
Trinexapac-ethyl [PC Code 112602]/Syngenta Crop Protection, LLC.

Magnitude of Residue- Rice

--------------------------------------------------------------------------------------------------------------------------------------------

EPA MRID #: 49282807

PMRA # of document: Not found

Page 6 of 9

Sample Handling and Preparation

Single control and duplicate treated samples of rice grain were collected from each site at 

maturity at PHIs of 51-100 days. At two trials, additional samples were collected to monitor 

residue decline 7 and 14 days before and after normal crop harvest; PHIs were 65, 72, 79, 85 and 

94 days for trial -09 and 85, 92, 99, 106 and 113 days for trial-15.

Samples were placed in frozen storage at the field sites after collection. All samples were 

shipped within 0-50 days by freezer truck or overnight courier (on dry ice) to Syngenta Crop 

Protection, LLC (Greensboro, NC) for sample preparation (grinding in the presence of dry ice). 

At Syngenta, samples were stored for ~94-305 days frozen (<-10 °C) from receipt until removal 

for preparation, and between preparation and shipment for analysis. Subsamples were shipped 

frozen by overnight courier from Syngenta to the analytical laboratory, North Coast Laboratories 

(NCL; Arcata, CA). Samples were stored frozen (≤–20 C) upon receipt at NCL, prior to and 

after analysis.

2. Description of Analytical Procedures

Samples were analyzed for residues of trinexapac-ethyl determined as CGA179500 by LC/MS/MS 

using Syngenta Analytical Method GRM020.01A “Analytical Method for the Determination of 

Residues of Trinexapac-Ethyl as CGA179500 in Crops by LC-MS/MS,” with minor 

modifications. This method was previously reviewed under DP# 378491 (S. Piper, 11/23/2011) 

in conjunction a crop field trial submission for barley grain (48043702.der).

Briefly, samples were refluxed with acetonitrile (ACN)/1 N HCl (80:20 v:v). An aliquot of the 

extract was applied to a C8 solid phase extraction (SPE) cartridge, and residues were eluted with 

0.5% formic acid:ACN (70:30 v:v). The eluate was adjusted to volume for LC/MS/MS analysis. 

The method does not provide for conversion of residues of CGA179500 to parent equivalents; 

therefore quantifiable residues of CGA179500 were converted to parent equivalents by the study 

reviewer using a molecular weight conversion factor of 1.125 (MW trinexapac-ethyl 252.26/MW 

trinexapac acid 224.21). 

The LOQ (determined as the LLMV) was 0.01 ppm for CGA179500. The limit of detection 

(LOD) was not reported.

II. RESULTS AND DISCUSSION

Method performance was evaluated during method verification and by use of concurrent 

recovery samples. For method validation, samples of untreated rice grain were fortified with 

CGA179500 at 0.01 and 1.0 ppm each. Individual recoveries (and overall standard deviation) 

were 97-122% (8.2%). For concurrent recovery, samples of rice grain were fortified at 0.01 and 

0.10 ppm each. Individual recoveries (and overall standard deviation) were 78-123% (12%). All 

recoveries were generally within the acceptable range of 70-120%; therefore the method was 

considered valid for the analysis of residues of trinexapac-ethyl in rice grain. The fortification 
Trinexapac-ethyl [PC Code 112602]/Syngenta Crop Protection, LLC.

Magnitude of Residue- Rice

--------------------------------------------------------------------------------------------------------------------------------------------

EPA MRID #: 49282807

PMRA # of document: Not found

Page 7 of 9

levels bracketed the measured residues. Concurrent recoveries were corrected for apparent 

residues in controls.

The detector response was linear (1/x weighting), with r

2 ≥0.9996 for rice grain calibration curve 

within the range of 0.0067-0.333 ppm. Representative chromatograms of control samples, 

fortified samples and treated samples were provided. The control chromatograms generally had 

no peaks of interest above the chromatographic background. The fortified sample 

chromatograms contained only the analyte of interest, and peaks were symmetrical and well 

defined. Apparent residues in controls were below the LOQ (<0.01 ppm). The reported residue 

values were not corrected for apparent residues in controls. 

Table B.7.6.1.1-4. Summary of Procedural/Concurrent Recoveries of Trinexapac-ethyl from Rice.

Matrix Analyte Fortification 

Level

(ppm)

Recoveries

(%)

Mean ± Std. Dev.

(%)

Not applicable. See above. (All mean recoveries were within acceptance criteria.)

The field residue samples for rice grain were stored frozen a maximum of 365 days (12.0

months) from harvest to extraction (Table B.7.6.1.1-5). The available freezer storage stability 

data indicate that residues of CGA179500 were stable when stored frozen in wheat grain for up 

to 24 months (MRID45898903). 

Table B.7.6.1.1-5. Summary of Storage Conditions.

Matrix Storage Temperature 

(°C)

Actual Storage 

Duration1

Interval of Demonstrated Storage Stability

Rice Grain Maintained frozen in 

field, preparation 

facility (<-10 C) and 

analytical laboratory 

(≤-20C)

245-365 days

(8.1-12.0 months)

Residues of CGA179500 were stable when 

stored frozen in wheat grain for up to 24 

months.

2

1

Interval from harvest to extraction. Samples were analyzed within 1-3 days of extraction. 

2 DP# 378491(S. Piper, 11/23/2011.); 45898903.der.

The results from the submitted field trials are presented in Tables B.7.6.1.1-6 and B.7.6.1.1-7. 

In rice grain harvested at PHIs of 51-100 days following a single foliar broadcast application of 

the 2.08 lb ai/gal EC formulation of trinexapac-ethyl made at 0.041-0.046 lb ai/A, individual 

sample (and per-trial average) residues of trinexapac-ethyl (determined as CGA179500) were

<0.01-0.270 ppm (<0.01-0.214 ppm).

In one residue decline trial residues were variable, with the highest residues observed at the 

target PHI. In the second residue decline trial, residues were below the LOQ in/on all samples; 

therefore, residue decline could not be determined.

Table B.7.6.1.1-6. Residue Data from Rice Field Trials with Trinexapac-Ethyl.

1

Location: City, State; 

Year2(Trial ID)

Zone Rice Variety Matrix Rate

lb ai/A

PHI3

(days)

Residues trinexapac-ethyl4(ppm) 

[Average]

Proctor, AR; 2012 

(TK0044924-01)

4 Roy J Grain 0.045 74 0.069, 0.059

[0.064]
Trinexapac-ethyl [PC Code 112602]/Syngenta Crop Protection, LLC.

Magnitude of Residue- Rice

--------------------------------------------------------------------------------------------------------------------------------------------

EPA MRID #: 49282807

PMRA # of document: Not found

Page 8 of 9

Table B.7.6.1.1-6. Residue Data from Rice Field Trials with Trinexapac-Ethyl.

1

Location: City, State; 

Year2(Trial ID)

Zone Rice Variety Matrix Rate

lb ai/A

PHI3

(days)

Residues trinexapac-ethyl4(ppm) 

[Average]

Pollard, AR; 2012 

(TK0044924-02)

4 RiceTec XL 729 Grain 0.045 85 0.061, 0.051

[0.056]

Cheneyville, LA; 2012 

(TK0044924-03)

4 CL 111 Grain 0.046 53 0.060, 0.056

[0.058]

Ville Platte, LA; 2012 

(TK0044924-04)

4 XL 729 Grain 0.046 51 0.026, 0.025

[0.025]

Washington, LA; 2012 

(TK00044924-05)

and

Washington, LA; 2012 

(TK0044924-07)

and

Washington, LA; 2012 

(TK0044924-08)

4 CL 151

Cocodrie

Cypress

Grain 0.044

0.044

0.046

60

60

60

0.180, 0.203, 0.270, 

0.236, 0.191, 0.203

[0.214]

Proctor, AR; 2012 

(TK0044924-06)

4 CL261 Grain 0.045 68 0.024, 0.024

[0.024]

Proctor, AR; 2012 

(TK0044924-09)

4 Wells Grain 0.045 65 0.043

72 0.053

79 0.088, 0.075

[0.082]

85 0.061

94 0.070

Washington, LA; 2012 

(TK0044924-10)

4 Cypress Grain 0.046 54 0.191, 0.203

[0.197]

Fisk, MO; 2012 

(TK0044924-11)

4 RiceTec XP 753 Grain 0.045 91 0.038, 0.036

[0.037]

Fisk, MO; 2012 

(TK0044924-12)

5 Francis Grain 0.045 85 0.037, 0.041

[0.039]

East Bernard, TX; 2012 

(TK0044924-13)

6 Presidio Grain 0.044 90 0.113, 0.113

[0.113]

East Bernard, TX; 2012 

(TK0044924-14)

6 Cheniere Grain 0.041 75 0.019, 0.019

[0.019]

Porterville, CA; 2012 

(TK0044924-15)

10 Koshihikari Grain 0.045 85 ND

92 <0.01

99 <0.01, <0.01

[<0.01]

106 <0.01

113 <0.01

Porterville, CA; 2012 

(TK0044924-16)

10 Koshihikari Grain 0.046 100 0.092, 0.083

[0.080]

1 A 2.08 lb ai/gal EC formulatioin (A7725M) was used.

2 HED has determined that Trials 05, 07, and 08 are replicate trials.

3 Target PHIs are bolded for decline trials.

4

 ND = Not detected (no peak) as reported by the petitioner. The method determines residues of trinexapac-ethyl as

CGA179500. Residues of CGA179500 were converted to parent equivalents by the study reviewer using a molecular weight 

conversion factor of 1.125 (MW trinexapac-ethyl 252.26/MW trinexapac acid 224.21). Per trial averages were calculated by the 

study reviewer.
Trinexapac-ethyl [PC Code 112602]/Syngenta Crop Protection, LLC.

Magnitude of Residue- Rice

--------------------------------------------------------------------------------------------------------------------------------------------

EPA MRID #: 49282807

PMRA # of document: Not found

Page 9 of 9

Table B.7.6.1.1-7. Summary of Residues from Rice Field Trials with Trinexapac-Ethyl.

Crop Matrix Total 

Application 

Rate

lb ai/A

PHI 

(days)

n

1 Residues (ppm Trinexapac-ethyl)

Min.2 Max.2 LAFT3 HAFT3 Median3 Mean3 SD3

Rice Grain 0.041-0.046 51-100 14 <0.01 0.270 <0.01 0.214 0.057 0.073 0.063

1 n = number of field trials.

2 Values based on total number of samples.

3 Values based on per-trial averages. LAFT = lowest average field trial, HAFT = highest average field trial, SD = standard 

deviation. For computation of the LAFT, HAFT, median, mean, and standard deviation, values <LOQ are assumed to be at the 

LOQ (0.01 ppm for trinexapac-ethyl as CGA179500).

III. CONCLUSIONS

The rice field trials are considered scientifically acceptable. In rice grain harvested at PHIs of 

51-100 days following a single foliar broadcast application of the 2.08 lb ai/gal EC formulation

of trinexapac-ethyl made at 0.041-0.046 lb ai/A, individual sample (and per-trial average) 

residues of trinexapac-ethyl (determined as CGA179500) were <0.01-0.270 ppm (<0.01-0.214 

ppm).

In one residue decline trial residues were variable, with the highest residues observed at the 

target PHI. In the second residue decline trial, residues were below the LOQ in/on all samples; 

therefore, residue decline could not be determined.

An acceptable method was used for residue quantitation, and adequate storage stability data are 

available to support sample storage durations and conditions for trinexapac-ethyl.

REFERENCES

DP# 378491 (S. Piper, 11/23/2011); 48043702.der and 45898903.der.