PESTICIDE RESIDUES IN FOOD - 1980
Sponsored jointly by FAO and WHO
EVALUATIONS 1980
Joint meeting of the
FAO Panel of Experts on Pesticide Residues
in Food and the Environment
and the
WHO Expert Group on Pesticide Residues
Rome, 6-15 October 1980
GUAZATINE
Explanation
Guazatine was evaluated by the FAO/WHO Joint Meeting in 1978
(FAO/WHO, 1979a) at which time it was required that, by 1980,
information be provided on the level, distribution, and fate of
guazatine residues when the material is applied to major citrus
fruit varieties in commercial practice, on the level and fate of
guazatine residues in meat and milk following the feeding of citrus
pulp containing residues of guazatine to cattle, and on an
analytical method suitable for regulatory purposes.
Information on the distribution and levels of guazatine residues in
citrus and rock melons was received from Australia and on residue
levels in citrus from Sweden. Methods of residue analysis were
received from both sources and are evaluated.
RESIDUES IN FOOD
USE PATTERN
Post-harvest treatments
Citrus. After cropping, the fruits ideally are treated immediately
on a conveyor packing line system. They are lightly scrubbed,
partially-dried, flooded (spray drenched) with 500 mg/l guazatine
solution, partially dried, coated with a thin wax film, and finally
dried. Treated fruits are then ready either for transport to market
or for cold temperature storage preceding later marketing or
export. If the fruits cannot be treated on the packing line
immediately, they are bulk dipped in 250 mg/l guazatine solution
for protection against rot while they are stored temporarily (not
more than 24 hours) at ambient temperature (Rippon, 1980).
Rock melons. At present the cropped fruits are bulk-dipped in a
guazatine-benomyl mixture: 500-500 mg/l, before being dried and
then transported to market or stored for later transport. If
conditions are favourable for rot-development the guazatine-dip
concentration is doubled (Rippon, 1980).
RESIDUES RESULTING FROM SUPERVISED TRIALS
Citrus treatments in Australia included a bulk dip for holding
purposes, a flood plus wax packing line treatment, and a combined
holding and packing line treatment. Treated citrus were subjected
to ambient (20°C) and cold (7.5°C) storage to simulate local and
export conditions). Recommended citrus treatments are a 250 mg/l
bulk dip and a 500 mg/l flood application.
Rock melon treatment consisted of dipping in guazatine alone
(250-2000 mg/l) or in combination with benomyl (250-750 mg/l). A
500 or 1000 mg/l guazatine dip in combination with 500 mg/l benomyl
is recommended, depending on seasonal conditions.
Results shown in Tables 1, 2, 3, and 7 were obtained from
preliminary citrus and rock melon trials. The data indicated
residues in whole citrus up to 1.5 mg/kg, and in whole rock melon
up to 5 mg/kg.
In subsequent rock melon trials (Tables 8 and 9), the more complete
data obtained confirmed that whole fruit residue of up to 4.5 mg/kg
could result from likely treatments, irrespective of the presence
of benomyl. The low residues found in the edible pulp (up to 0.3
mg/kg) may be due to contamination during sample preparation. The
presence of benomyl in mixed dips did not interfere in the
guazatine analysis.
In subsequent citrus trials (Tables 4-6), the more complete data
indicated higher average residues than obtained in the initial
trials, ranging from about 0.9 mg/kg for the dip, up to 2.5 mg/kg
for the flood and combined treatments. All trials indicated that
most of the citrus residue remains on the surface of the fruit
during 28 days storage after treatment, with appreciable decrease
by 56 days. This decrease could be either due to migration of
guazatine into the fruit or simply reflect strong binding of the
guazatine to the fruit surface. Pulp residues were always very
low, ranging from 0.1 to 0.4 mg/kg.
Lemon residues were always somewhat higher than for orange or
tangor. This could be due to the shape and surface characteristics
of lemon, and differences in the age and maturity of the fruits
(Australia, 1980).
Citrus Preliminary trials
Trial 1
TABLE 1. Guazatine Residues in Citrus Fruit Following Post-harvest Treatment
Guazatine Fruit Variety Storage Guazatine Residue (mg/kg) in
Treatment temp. stored fruit
0 Days 7 Days 14 Days 21 Days
Valencia orange 20°C 0.42 0.42 Not Analysed
520 mg/l Eureka lemon 20°C 0.56 0.48 " "
Bulk dip Ellendale tangor 20°C 0.43 0.48 " "
Valencia orange 20°C 0.53 0.53 Not Analysed
520 mg/l Eureka lemon 20°C 1.01 0.93 " "
Bulk dip Ellendale tangor 20°C 0.92 0.99 " "
+ Wash, Valencia orange 7.5°C 0.53 0.64 0.58 0.60
695 mg/l Eureka lemon 7.5°C 1.01 0.84 1.01 1.05
Flood/wax Ellendale tangor 7.5°C 0.92 0.50 0.45 0.30
Valencia orange 20°C 0.40 0.51 Not Analysed
695 mg/l Eureka lemon 20°C 0.42 0.91 " "
Flood/wax Ellendale tangor 20°C 0.67 0.83 " "
Valencia orange 7.5°C 0.40 0.67 0.51 0.61
Eureka lemon 7.5°C 0.42 0.76 0.89 0.72
Ellendale tangor 7.5°C o.67 1.03 0.60 0.45
TABLE 2. Guazatine Residues in Peel, Pulp and Whole Citrus Fruit after
21 days storage at 7.5°C following Post-harvest Treatment
Guazatine treatment Fruit Sample Guazatine
variety residues (mg/kg)
520 mg/l Bulk Dip, Valencia Peel 3.0
+ Wash + 695 Orange pulp 0.2
mg/l Flood/Wax Whole Fruit 0.8
Eureka Peel 1.6
Lemon pulp 0.4
Whole Fruit 0.86
Ellendale Peel 3.5
Tangor pulp 0.55
Whole Fruit 1.2
TABLE 3. Guazatine Residues in Citrus Fruit following Post-harvest Treatment
RESIDUES (mg/kg)
Guazatine Fruit Storage 0 Days 4 Days 7 Days 14 Days 28 Days
Treatment Variety Temp. Storage Storage Storage Storage Storage
250 mg/l Valencia
Orange 20°C 0.54 0.52 NA1 NA NA
Bulk Dip Eureka
Lemon 20°C 0.63 0.62 NA NA NA
Ellendale
tangor 20°C 0.63 0.63 NA NA NA
500 mg/l Valencia 20°C 0.50 NA 0.43 0.42 NA
Flood/Wax orange 7.5°C 0.50 NA 0.38 0.40 0.50
Eureka 20°C 0.63 NA 0.52 0.51 NA
lemon 7.5°C 0.63 NA 0.46 0.44 0.63
Ellendale 20°C 0.62 NA 0.63 0.60 NA
tangor 7.5°C 0.62 NA 0.46 0.42 0.38
250 mg/l Valencia 20°C 0.42 NA 0.45 0.44 NA
Bulk Dip + orange 7.5°C 0.42 NA 0.43 0.42 0.49
Wash Eureka 20°C 0.53 NA 0.65 0.64 NA
500 mg/l lemon 7.5°C 0.55 NA 0.50 0.51 0.40
Flood Wax Ellendale 20°C 0.64 NA 0.63 0.63 NA
tangor 7.5°C 0.64 NA 0.61 0.63 0.60
1 NA = not analysed
Citrus advanced trials
Trial 1
TABLE 4. Guazatine Residues in Citrus Fruit Following 250 mg/l
Post-harvest Dip
Fruit Distribution Residues (mg/kg)
Variety of Residues 0 Days1 4 Days1 Mean2
(whole fruit)
Valencia Surface 0.54 0.52 0.86
Orange Whole 0.91 0.8
Pulp 0.10 NA
Peel 2.50 NA
Eureka Surface 0.63 0.62 0.99
Lemon Whole 1.03 0.95
Pulp 0.10 NA
Peel 1.60 RA
Ellendale Surface 0.63 0.63 0.94
tangor Whole 0.94 0.94
Pulp 0.10 NA
Peel 3.60 NA
1 Each result mean of 4 replicates
2 Mean of 8 analyses
Trial 2
TABLE 5. Guazatine Residues (mg/kg) in Citrus Fruit Following 500 mg/l
Flood and Storage at either 20°C or 7.5°C
Fruit Distribution 0 Days 7 Days 14 Days 28 Days 56 Days Mean ± s.d.
Variety of Residues mg/l whole fruit
Temp. at
storage
Valencia Surface 0.50 0.43 0.42
Orange Whole Fruit 1.48 1.30 1.20
20°C Pulp 0.1 - -
Peel 4.10 - -
7.5°C Surface 0.38 0.40 0.50 0.11
Whole Fruit 1.5 1.2 1.3 1.6
Pulp - - 0.1 1.44 ± 0.251
Peel - - 4.0 -
Eureka Surface 0.63 0.52 0.51
Lemon Whole Fruit 2.1 1.83 1.70
20°C Pulp 0.1 - -
Peel 3.6 - -
7.5°C Surface 0.46 0.44 0.63 0.13
Whole Fruit 1.84 2.2 1.85 2.1
Pulp - - 0.1 1.95 ± 0.291
Peel - - 2.6
Ellendale Surface 0.62 0.63 0.60
Tangor Whole Fruit 1.75 1.4 1.5
20°C Pulp 0.3 - -
Peel 2.8 - -
7.5°C Surface 0.46 0.42 0.38 0.12
Whole Fruit 1.36 1.4 1.34 1.4
Pulp 0.3 1.45 ± 0.171
Peel 2.6
1 Mean of 28 analyses
Trial 3
TABLE 6. Guazatine Residues (mg/kg) in Citrus Fruit Following Post-harvest
Bulk Dip (250mg/l) and Flood Treatment (500 mg/l)
Fruit Distribution 0 Days 7 Days 14 Days 28 Days 56 Days Mean ± s.d.
Variety of Residues mg/l whole fruit
Temp. at
storage
Valencia Surface 0.42 0.45 0.44
Orange Whole Fruit 1.2 1.3 1.4
20°C Pulp 0.1 - -
Peel 2.4 - -
7.5°C Surface - 0.43 0.42 0.49 0.06 1.33 ± 0.261
Whole Fruit - 1.2 1.6 1.4 1.2
Pulp - - - - 0.2
Peel - - - - 2.2
Eureka Lemons Surface 0.53 0.65 0.64
20°C Whole Fruit 1.6 1.83 1.75
Pulp 0.2 - -
Peel 1.9 - -
7.5°C Surface 0.50 0.51 0.37 0.11 1.83 + 371
Whole fruit 1.8 1.8 1.8 2.2
Pulp - - 0.2
Peel - - 2.1
Ellendale Surface 0.64 0.63 0.63
Tangor Whole Fruit 1.6 1.52 1.6
20°C Pulp 0.31 - -
Peel 2.1 - -
7.5°C Surface 0.61 0.63 0.60 0.08 1.52 ± .31
Whole Fruit 1.4 1.6 1.6 1.3
Pulp 0.4
Peel 2.2
1 Mean of 28 analyses
Rock melon preliminary trial
TABLE 7. Guazatine Residues in Whole Rock Melon Following Post-harvest
Dipping
Initial Deposits
Guazatine Actual Conc. Guazatine residues (mg/kg) in
treatment (mg/l) of dip (mg/l) whole fruit except seeds
500 480 2.7
1000 1090 3.4
2000 2420 4.9
Rock melon advanced trials
TABLE 8. (Trial 1) Guazatine Residues in Rock Melon Following Post-harvest
Bulk Dipping in Guazatine and Guazatine/Benomyl Dips
Treatment Distribution Guazatine Residues (mg/kg)
(mg/l) 0 Days1 7 Days1 Mean ± s.d.2
Whole fruit
500 Pulp Nil Nil
Guazatine Peel 2.7 2.9
Whole Fruit 1.12 1.30 1.21 ± 0.27
1000 Pulp 0.29 0.15
Guazatine Peel 6.50 6.50
Whole Fruit 3.60 4.2 3.90 ± 0.52
500 Guazatine + Pulp Nil Nil
500 Benomyl Peel 2.87 3.20
Whole Fruit 2.00 1.30 1.65 ± 0.46
1000 Guazatine + Pulp 0.35 0.30
500 Benomyl Peel 5.85 6.6
Whole Fruit 3.52 4.3 3.96 ± 0.49
1 each result mean of 4 replicates
2 mean of 8 analyses
TABLE 9. (Trial 2) Guazatine Residues in Rock Melon Following
Post-harvest Bulk Dipping in Various Mixtures of Guazatine and Benomyl
Treatment Guazatine residues (mg/kg)1
(mg/l) Pulp1 Peel1 Whole Fruit1
Guazatine Nil ND ND ND
Benomyl 250
Guazatine Nil ND ND ND
Benomyl 500
Guazatine Nil ND ND ND
Benomyl 750
Guazatine 250 ND 1.2 0.6
Benomyl Nil
Guazatine 250 ND 1.3 0.6
Benomyl 250
Guazatine 250 0.3 1.6 0.9
Benomyl 500
Guazatine 250 0.3 3.0 0.6
Benomyl 750
Guazatine 500 0.3 4.45 2.7
Benomyl Nil
Guazatine 500 ND 6.2 2.4
Benomyl 250
Guazatine 500 ND 5.9 2.35
Benomyl 500
Guazatine 500 0.4 5.0 1.75
Benomyl 750
Guazatine 500 0.4 5.0 1.75
Benomyl 1000
Guazatine 1000 ND 5.2 2.4
Benomyl 250
Guazatine 1000 0.3 8.8 3.8
Benomyl 500
Guazatine 1000 0.45 7.2 3.2
Benomyl 750
1 results mean of 4 replicates
Information was received from Sweden on guazatine residue distribution
and levels in oranges, mandarins, and lemons received from Australia.
The fruit had been washed, flooded with guazatine solution (500 mg/kg)
and waxed in a laboratory packing line before being air freighted to
Sweden. The received fruit was stored at room temperature for 1 week,
then deep frozen until analysis. Results are shown in Table 10.
Maximum residues in whole fruit did not exceed 0.3, 0.5, and 0.2 mg/kg
for oranges, mandarins and lemons respectively. All residues were
found on the peel in separate analyses (Kenogard, 1980).
TABLE 10. Residue Analysis of Guanidated Amines in Citrus Fruits from
Australia 1979
Pesticide and Residue found
Sample dosage rate mg/kg
Washington navel oranges: whole fruit Panoctine 0.3
peel 500 mg/kg 3
pulp 500 mg/kg 0.05
Emperor mandarins: whole fruit 500 mg/kg 0.5
peel 500 mg/kg 2
pulp 500 mg/kg 0.05
Eureka lemons: whole fruit 500 mg/kg 0.2
peel 500 mg/kg 2
pulp 500 mg/kg 0.05
METHODS OF RESIDUES ANALYSIS
A new spectrophotometric procedure has been developed for guazatine
residues in fruit, which is sensitive to 0.02 mg/kg. A 100 g fruit
sample is chopped, then mixed with 10 g NaOH, 30 g NaCl, 50 ml
n-butanol, and 10 ml hexane in a blender for 3 min. at 4000 rpm. The
contents are then transferred to a centrifuge cup and centrifuged for
5 min. at 4000 rpm. The supernatant portion is filtered through a
glass or cotton wool plug into a separatory funnel and the solids
re-extracted with a further 30 ml butanol, centrifuged, and filtered.
The lower aqueous layer is discarded and the solvent layer mixed with
70 ml hexane and extracted with 2 × 15 ml of MH2SO4. The acid
extract is mixed with 5 g NaOH and 5 g NaCl and extracted twice with 5
ml butanol. The butanol extract is mixed with 10 ml hexane and
allowed to stand at least 2-3 hours. To remove traces of alkali the
solvent mixture is then washed with 10 ml of 0.14 MH3PO4. Five ml
of reagent (0.2 g Coomassie Brilliant Blue G250 in 100 ml ethanol; add
190 ml 85% orthophosphoric acid and 400 ml of 1% starch solution; make
to 2 l with water, allowed to stand overnight, and filter (Whatman No.
1) before using) is mixed with 1 ml of the acid extract or 1 ml
guazatine standard and the absorption measured at 585 nm against a
blank (1 cm cell, 1 nm bandwidth). Because of its selectivity and
sensitivity, the method appears very suitable for regulatory purposes
(Higginson, 1979; Ahmed et al, 1979).
EVALUATION
APPRAISAL
Residue data from post-harvest trials on citrus and rock melons were
available. Citrus fruits (orange, tangor, lemon) and rock melons were
dipped or, with citrus fruits, flooded with guazatine solutions of
500-2000 mg/l concentration. Guazatine residues in fruit were
determined up to 21 days after treatment, the treated fruit being
stored at either 20°C or 7.5°C during this period.
In no case did the guazatine residue exceed 5 mg/kg in whole fruit.
With both citrus and rock melon most of the residue was in the peel;
on average, about 10% of the residue in citrus and 4% in rock melon
were in the fruit pulps. The level of residues were always higher
than those of oranges and tangors. With rock melons the whole-fruit
guazatine residue were proportional to the concentration of guazatine
in the dip solution.
Residue data were also provided from analyses of oranges, mandarins,
and lemons treated in Australia and air freighted to Sweden. Maximum
residues did not exceed 0.5 mg/kg (whole fruit) in this experiment and
virtually all residue was located in the peel.
An analytical method for guazatine residues in fruit based on the
spectroscopic absorption of a stable blue complex formed by the
reaction of guazatine with Coomassie Brilliant Blue G250 has been
developed which is selective and sensitive to 0.02 mg/kg. It appears
very suitable for regulatory purposes.
The 1978 requirements for data on the level and distribution of
guazatine residues in citrus treated in commercial practice and for a
suitable regulatory method of analysis are satisfied. No information
was available to the Meeting on the level and fate of guazatine
residues in meat and milk following the feeding of citrus pulp
containing guazatine residues to cattle.
RECOMMENDATIONS OF RESIDUES LIMITS
The 1978 recommendation of a temporary maximum residue limit of 5
mg/kg for citrus fruits is confirmed and changed to a maximum residue
limit. The maximum residue level listed below for melons is suitable
for establishing a maximum residue limit in addition to those
previously established. The numerical values refer to the parent
compound alone.
Commodity Maximum Residue Limit, mg/kg
Citrus fruits 5
Estimated Maximum Residue Level
mg/kg
Melons 5
FURTHER WORK OR INFORMATION
Desirable
Information on the level and fate of guazatine residues in meat and
milk following feeding of citrus pulp containing guazatine residues to
cattle.
REFERENCES
Ahmad N. and Milham, P.J. A rapid and sensitive method for measuring
micro quantities of guazatine in dilute solutions. (1979)
(Unpublished) Biological and Chemical Research Institute, Rydalmere,
N.S.W., Australia.
Australia Guazatine residues in citrus fruits and rock melons
following post-harvest treatments. (1980) Private communication.
Higginson, F.R. Determination of guazatine residues in fruit.
Biological and Chemical Research Institute, New South Wales,
Department of Agriculture.
Kenogard, A.B. Residue analysis of guanidated amines in citrus fruits
from Australia, 1979, 80-AC-0184. Report submitted to 1980 JMPR.
Rippon, E. Private communication. Gosford Horticultural Post-harvest
Laboratory. Gosford, N.S.W., Australia.
See Also:
Toxicological Abbreviations
Guazatine (Pesticide residues in food: 1978 evaluations)
Guazatine (Pesticide residues in food: 1997 evaluations Part II Toxicological & Environmental)