Sponsored jointly by FAO and WHO


    Joint meeting of the
    FAO Panel of Experts on Pesticide Residues
    in Food and the Environment
    and the
    WHO Expert Group on Pesticide Residues
    Geneva, 3-12 December 1979



    Chemical Name:          Tri(cyclohexyl)-(1,2,4-Triazol-1-yl)tin or

    Synonyms:               Peropal, BUE 1452

    Structural formula:


    Other Information on Identity and Properties

    Molecular Weight:       436.2
    Appearance:             White Powder
    Melting Point:          218.8°C
    Vapor Pressure:         Less than 5 × 10-5 mbar at 25°C
    Solubility:             in water              <0.25 mg/kg
                            in cyclohexane        )
                            in isopropanol        )
                            in toluene            ) 0-0.01 g
                            in methylene chloride ) per g solvent
                            in ligroin            )

    Minimum degree of purity:  90%

    Impurities in the technical material

    Detailed information on the impurities in technical azocyclotin was
    reported to the meeting.



    Azocyclotin is an organotin acaricide effective against spider miters.
    It is recommended for the control of strains which are resistant to
    other chemical compounds.  Azocyclotin gives good control of all
    motile stages, i.e. larvae as well as adults.  Through trials on mixed
    populations, it has been established that azocyclotin has an
    ovolarvicidal effect on summer but not on winter eggs.

    Azocyclotin is a contact poison, and it is notable for its long
    residual activity.  It is used on pome and stone fruit, strawberries,
    vegetables and grapes.  When used at the recommended concentrations,
    it displays no phytotoxicity.  Azocyclotin is marketed as a 25% and
    50% wettable powder, in Argentina, Australia, Austria, Chile, Federal
    Republic of Germany, Greece, Iran, Lebanon, Morocco, New Zealand,
    Peru, South Africa, Spain and Uruguay.  It is used as a foliar spray
    on the crops as listed in Table 1.  There are no post-harvest uses.

    Table 1.  Current uses of Azocyclotin

                     Concentration       Number of       Pre-harvest
    Crop             % act. ing.         applications    interval

    Pome and stone   0.025                  1-3          14 days
    fruit            (0.3-0.5 kg/ha)

    Strawberry       0.025                  1-3          14 days
                     (0.5 kg/ha)


    Bush beans       0.025                  1-2          14 days

    Eggplants        0.025                  1-2          14 days

    Grapes           0.025                  1-2          35 days
                     (0.5 kg/ha)          (max.3-4)


    Residue studies after applications of azocyclotin (I) have been
    performed on apple, bush beans, eggplant, damson plums, strawberry and
    wine grape (Table 2).  The residue data were obtained by the use of an
    organotin method (Möllhoff, 1977a) which determines the sum of the
    parent compound, azocyclotin (I), and its two metabolites,
    tricyclohexyl tin hydroxide (or cyhexatin) (III), and dicyclohexyl tin
    oxide (IV) (cfr. Figure 1).  Compound IV always represented less than
    10% of the total residue.

    Residue data obtained by the use of a triazole method (Möllhoff,
    1977a) is presented in Table 3, from which it is noted that the
    residues of the triazole moiety were analytically non-significant or
    below detection limit (i.e. 0.1 - 0.2 mg%kg) shortly after
    application.  If not otherwise stated, therefore, the following
    residue information is obtained by the organotin method.


    After one, two or three applications of 0.3-0.65 kg azocyclotin per
    ha, the maximum residue on day 0 was 0.35 mg/kg.  Within the course of
    three weeks, the residue levels usually dropped down to or below the
    limit of determination (0.05 mg/kg).

    Bean, kidney

    Following three applications of 0.225 kg azocyclotin per ha, the
    residue levels declined within three weeks from 0.2-0.3 mg/kg to
    n.d.-0.15 mg/kg.


    Following one or two applications of azocyclotin at 0.375-0.7 kg/ha,
    the initially measured residue level was 0.1-0.45 mg/kg.  It decreased
    to a level below the limit of determination during the following 30
    days, or in several cases during only 14 days.

    Damson plums

    The maximum residue level measured after three applications of
    azocyclotin at 0.5 kg/ha was 0.8 mg/kg, while the residue levels
    measured 3 and 4 weeks after the final spray were 0.25, resp. 0.2


    Following two spray applications of azocyclotin at 0.5 kg/ha, the
    immediate residue levels were 0.6 mg/kg.  No more residues were
    detectable 14 days later.

    Wine Grape

    Following three or four spray applications of azocyclotin at 0.45-0.5
    kg/ha, the initial residue level in a series of experiments varied
    from 0.85 up to 2.1 mg/kg.  Measurements made four weeks after the
    final spray showed that the residue level was less than 1 mg/kg
    following three applications, but higher following four applications.


    A general degradation pathway for azocyclotin is shown in Figure 1,
    indicating a gradual and step-wise off-splitting of the rings bound to
    the central tin atom, starting with the 1,2,4-triazole moiety. Some
    properties of the individual metabolites are given in Table 4.

        Table 2.  Residues of Azocyclotin from Supervised Trials (Bayer AG)*

                           Application             Days after last     Residues          Country
    Crop               Rate          Frequency     Treatment           (mg/kg)
    Apple            0.3 kg/ha          1×             7              0.1 - 0.15         France
                                                     13-14            <0.05 - 0.05
                                                      21              n.d. - <O.05
                     0.3125             1/2×           0              0.15 - 0.30        Israel
                     kg/ha                             7              0.05 - 0.15
                                                      14              <0.05 - 0.05
                                                      30              n.d. - n.d.
                     0.3 - 0.375        2×            14              0.06 - 0.08        Netherlands
                     kg/ha                            21              n.d. - 0.1
                                                      28              n.d. - n.d.
                     0.5 kg/ha          3×             0              0.15 - 0.25        Germany (FRG)
                                                       7              0.1 - 0.15
                                                      14              0.05 - 0.15
                                                      21              n.d. - 0.1
                                                      28              n.d. - 0.05
                     0.625 kg/ha        1/2×           0              0.2 - 0.35         Israel
                                                       7              0.15 - 0.3
                                                      14              0.05 - 0.2
                                                      30              n.d. - <0.05

    Beans (Bush
    or Kidney)       0.225 kg/ha        3×             0              0.2 - 0.3          Germany (FRG)
                                                       7              0.15 - 0.2
                                                      14              <0.05 - 0.15
                                                      21              n.d. - 0.15
    Eggplant         0.375 kg/ha        1/2×           0              0.1 - 0.45         Israel
                                                       7              n.d. - 0.15
                                                      14              n.d. - n.d.
                                                      30              n.d. - n.d.
                     0.75 kg/ha         1/2×           0              0.1 - 0.45
                                                       7              n.d. - 0.2
                                                      14              n.d. - 0.1
                                                      30              n.d. - n.d.

    Table 2.  Continued...

                            Application            Days after last     Residues          Country
    Crop                 Rate        Frequency     Treatment           (mg/kg)

    Plum, damson     0.5 kg/ha          3×             0              0.1 - 0.8          Germany (FRG)
                                                       7              0.05 - 0.5
                                                      14              <0.05 - 0.4
                                                      21              <0.05 - 0.25
                                                      28              <0.05 - 0.2
    Strawberry       0.5 kg/ha          2×             0              0.55 - 0.6         Germany (FRG)
                                                       7              0.1 - 0.15
                                                      14              n.d. - n.d.

    Wine grape       0.3 kg/ha          1×             7              0.3                France
                                                      14              0.25
                                                      21              0.2

                     0.45-0.5           3×             0              0.85 - 2.1         Germany (FRG)
                     kg/ha                            14              0.45 - 1.75
                                                      21              0.45 - 0.8
                                                      28              0.l - 0.8
                                                      35              0.1 - 0.9
                                                      42              0.1 - 0.15
                                                      49              <0.05 - 0.15

                     0.5 kg/ha          4×             0              1.45 - 2.15
                                                       7              1.20 - 2.4
                                                      14              1.15 - 1.75
                                                      22              1.15 - 1.9
                                                      29              1.0 - 1.4
                                                      36              1.05 - 1.2

    *  Results in this table obtained by organotin method (Möllhoff, 1977a).

    Table 3.  Residues of azocyclotin determined by triazole and organotin methods

                     Application            Days after          Triazole         Organotin         Country
    Crop             rate                   treatment           Method           Method

    Apple           1 × 0.3 kg/ha               7               n.d.- n.d.        0.1 - 0.15       FRG
                                               14                   -           <0.05 - 0.05
                                               21                   -           <0.05 - <0.05

                    1 × 1 kg/ha                 0               0.4 - 0.4           -              FRG
                                                7               n.d.- <0.1          -
                                               14               n.d. - n.d.         -

                    1 × 0.37-0.75
                    kg/ha                       9                 2.32              -              New
                                                3                 1.28              -              Zealand
                                                7                 0.43              -
                                               14                 0.05              -

    Grape           1 × 0.3 kg/ha               7                 n.d.              0.3            FRG
                                               14                 n.d.              0.25
                                               21                 n.d.              0.2

    FIGURE 1

    Table 4.  Some properties of azocyclotin metabolites

                                           Metabolites (Fig.1)
                       Azocyclotin      II         III        IV

    Melting point      218.8°C         121°C      245°C      291°C

    pressure at:

    20°C)              <5 x 10-5      3 X 10-4       not measured
    30°C)in mbar       -              1 X 10-3
    40°C)              -              3 X 10-3
    50°C)              -              1 X 10-2

    Solubility in
    water (mg/kg)      <0.25          readily       <1       insoluble

    In rats

    The meeting is informed that studies on biokinetics and on metabolism
    in rats have been conducted with a mixture of
    1-tricyclohexyl-14C-stannyl-1,2,4-triazole and

    In plants

    Residue analyses on apples and grapes performed by the triazole method
    gave results close to or below the limit of determination (0.1 mg/kg)
    one week after treatment of the plants (cfr Table 3).  When the
    organotin method was used, on the other hand, residues were found for
    a longer period (Table 2), indicating that the triazole ring was the
    first ligand to be split off from the central tin atom.  By referring
    to the vapor pressure/temperature gradient of triazole (II) (cfr.
    Table 4), it has been suggested that triazole disappearance may be due
    to volatilization (Möllhoff, 1977a).  In the field studies of Möllhoff
    (1977a) it is reported that metabolite IV, dicyclohexyl tin oxide,
    occurs only in small amounts in plants material, i.e. less than 10%.

    Mass balance and metabolism studies on azocyclotin were performed in a
    laboratory ecosystem with bush (i.e. kidney) beans, enclosed in a
    quartz bell jar giving 96% light transmission (Wolff et al., 1977a).
    The azocyclotin preparation which was used was a well-defined mixture
    of 1-tricyclohexyl-14C-stannyl-1,2,4-triazole and
    1-tricyclohexyl-stannyl113-1,2,4-triazole.  Forty-four days after the
    treatment, the amounts of 14C and 113Sn radioactivity distributed
    among the different parts of the system was measured, and 95% of the
    applied radioactivity was recovered.

    In the exhaust air absorber, less than 0.01% of the applied 113Sn
    radioactivity was found as against 41.7% of the originally applied
    14C radioactivity.  Of the remaining 58.3% of the 14C radioactivity,
    43.3% was present on/in the soil, and 9.8% in the plants.  Of the
    originally applied 113Sn radioactivity, 81.7% was found on or in the
    soil and 14.5% on or in the plants.  Autoradiographs showed spray
    spots caused by 14C radioactivity on the treated leaves, as against
    uniform blackening on newly grown plant parts.  From these findings
    and from the comparison of 14C radioactivity and 113Sn radioactivity
    in different plant parts (Table 5), it is evident that a major
    proportion of the applied azocyclotin was no longer present as the
    unchanged parent compound.  There was only little translocation of the
    radioactivities in the plants.  However, a large proportion of the
    14C radioactivity volatilized and was trapped in the absorber.

    Thin-layer chromatographic separation of the plant extracts revealed
    that the individual azocyclotin metabolites were present in various
    plant parts in the following proportions: metabolite III: 47 - 71%,
    metabolite IV: 7 - 33%, metabolite V: 5-22% and inorganic Sn: 6-19%
    (cfr. Table 6).  The structures of these compounds were verified by
    comparison of their Rf values from TLC with those of reference
    substances, and by the ratios of 113Sn:14C (cfr. Table 6).

    In processing

    It will be noted from the data presented in Table 7 that when wine
    grapes were pressed, about 25% of the residue was carried into the
    must.  However, the wine made from the must did not contain any
    measurable residue amounts of azocyclotin.

    In soil

    Leaching Studies

    Whereas azocyclotin is very sparingly soluble in water, 1,2,4-triazole
    (II) displays good solubility.  This metabolite, however, is absorbed
    from water on soil particles according to soil leaching studies
    performed by Möllhoff (1977b).  From these studies performed on three
    different soils, it was found that neither azocyclotin, nor its
    metabolites II, III and IV were detectable in percolated water under
    the conditions of the experiments.  The limits of determination both
    for azocyclotin and for II, III, and IV were at 2% of the applied
    amount of parent compound.

    Also in the ecosystem planted with bush beans (Wolff et al., 1977a),
    vertical movement in the soil was minimal.  After 44 days, about 98%
    of the applied radioactivity (113Sn + 14C-azocyclotin) was retained
    in top soil between 0 and 3 cm, while soil layers below 15 cm showed
    no activity at all.

    Table 5.  Distribution of 113Sn and 14C radioactivities among
    different plant parts, soil and exhaust air from laboratory simulation
    study after 44 days. (Wolf et al., 1977a).


                                   113Sn (in %)       14C (in %)

    Bush (i.e. kidney) beans

    Old beans                          0.03               0.30
    Young beans                        0.01               0.03
    Leaves + stem                      7.92               5.11
    Fallen leaves                      6.56               4.44
    Roots                              0.10               0.03


    Total in plants                   14.62               9.91
    Soil                              81.7               43.3
    Exhaust air                       <0.01              41.7


    Recovered                         96.3%              94.9%

        Table 6.  Metabolite proportions after azocyclotin treatment and ratios of 113Sn:14C-radioactivity in
    bean plant extracts (Wolf et al, 1977a)

                                                                                                  Origin on
    Plant part          III: Tricyclohexyl Sn    IV: Dicyclohexyl Sn      V: Monocyclohexyl Sn    TLC-plate*

    Old beans                   71.7%                   17. 3%                     4.9%             6.0%
    Young beans                 47.4%                   33.6%                      9.5%             9.5%
    Leaves + stem               69.5%                    7.3%                     13.0%             9.6%
    Fallen leaves               61.6%                    8.4%                     15.9%            14.6%
    Roots                       47.6%                   10.9%                     22.1%            19.14%


    Ratios                    113Sn: 14C              113Sn:14C                 113Sn:14C         113Sn:14C


    Theoretical               1 : 0.92                1 : 0.62                  1 : 0.31          1 : 0
    Found                     1 : 0.91-1.06           1: 0.58-0.84              1: 0.27-0.38      1. 0.03-0.16

    *  Tin compounds without cyclohexyl rings.

    Table 7.  Azocyclotin residues during wine processing 
    (Bayer AG)

                    Experiment 1        Experiment 2
                            Azocyclotin (mg/kg)
    Grapes          1.05 - 1.2          <0.05 - 0.1
    Must            0.25 - 0.9          <0.05 - <0.05
    Wine            n.d.                n.d.

    Degradation in soil

    Field experiments on three different soils showed that the triazole
    component of azocyclotin was eliminated to levels below the limit of
    determination (0.1 mg/kg) within 14 days.  The organotin residues
    measured as the sum of I, III and IV, on the other hand, were degraded
    with a half-life of 50 to 90 days.  Also following two treatments at a
    one-year interval, there was found no extra build-up of soil residues.
    (cfr. Table 8).

    In studies under laboratory conditions, degradation of azocyclotin in
    two different soils indicated half-lives in the order of 250 days,
    while in another experiment under the same conditions, half-lives were
    found to be 200 days for I and metabolite III, and about one year for
    the sum of I, III, IV and V (Wolff et al., 1977b).

    Metabolism in soil

    In field experiments, azocyclotin (I) itself was measurable only for
    one week (Table 3).  During the first week, also, up to about 25%
    dicyclohexyl tin oxide (IV) formed (Möllhoff, 1977b).  Its content
    declined thereafter parallel to the disappearance of its immediate
    precursor, tricyclohexyl tin hydroxide (III).  In laboratory
    metabolism studies conducted with azocyclotin dicyclohexyl tin oxide
    was formed gradually during 30-60 days and remained thereafter on a
    plateau level corresponding to about 15% of the applied azocyclotin

    In another laboratory experiment using a larger amount of soil (500 g)
    held in a closed bottle, measurements made nine months after
    application of 50 mg azocyclotin/kg showed that 45% of the applied
    amount of tin was still present as organotin compounds in the soil. 
    At this point of time, the analytically determined components triazole
    (II) and tricyclohexyl butyl tin (i.e. metabolite III after
    butylation) were present in almost stoichiometric proportions of 23.8%
    and 25.4%, respectively.  Whether azocyclotin or a mixture of triazole
    and tricyclohexyl tin hydroxide was present, or whether there was a
    balance among I, II and III could not be decided by analysis.  From
    the fast decline of the triazole proportion in field conditions,

    however, it was concluded that triazole under open conditions would
    volatilize rapidly (Möllhoff, 1977b).

    In the above-mentioned larger-scale laboratory experiment, it was also
    found after nine months of storage that of the originally applied
    azocyclotin dose, 1O.8% was present as dicyclohexyl tin oxide (IV) and
    8.25% as cyclohexyl stannoic acid (V).  After derivatization with
    butyl lithium these two compounds were measured quantitatively by gas
    chromatography, and after separation on capillary columns, they were
    identified by mass spectrometry.  The same two metabolites (IV and V),
    were found in soil nine months after application of the metabolite
    dicyclohexyl tin oxide (IV) in amounts corresponding to 36.5% and
    11.7% respectively.  In the soil metabolism studies of Wolf et al.
    (1977b), using a mixture of 14C- and 113Sn-labelled azocyclotin, it
    was found that the proportion of 113Sn radioactivity which was
    non-extractable never exceeded 6.6% while, on the other hand, the
    proportion of non-extractable 14C radioactivity increased towards the
    end of the 200-day experiment to 24.5% (cfr Table 9).  This is
    interpreted as a sign of metabolic incorporation of 14C-carbon into
    non-extractable compounds, the identity of which, however, remained
    unknown.  The proportion of the applied tin to which three cyclohexyl
    rings were still bound, declined to a level of 50% during this

    Fate in water

    Degradation of azocyclotin in aquarium water was studied during 150
    days in closed bottles at 22 ± 2°C, with azocyclotin added at a level
    of 10 mg/kg (Möllhoff, 1977c).  The 25% w.p. formulated azocyclotin
    was used for this experiment, but despite frequent shaking, the
    formulation could not be held continuously in suspension.

    At the end of the experimental period, one-third of the applied amount
    of azocyclotin still contained all three cyclohexyl rings at the tin
    atom (Table 9), while the proportion of triazole still bound to the
    tin atom could not be determined analytically.  However, formation of
    free triazole was observed at a level which on termination of the
    experiment was estimated to be 0.41 mg/kg, equivalent to 2.6 mg/kg
    when calculated as azocyclotin.  In an open system, such free triazole
    is expected to disappear by volatilization.

    Metabolite IV, dicyclohexyl tin oxide, was determined throughout this
    experiment, although in small amounts only, i.e. no more than 0.26

    Table 8.  Azocyclotin residues in soil by triazole and organotin
    methods (Wolf, et al., 1977b)

    Application       Days after           Azocyclotin (mg/kg)
                      treatment        Triazole         Organotin
                                       Method           Method

    First year

    1 × 5 kg/ha           0            2.3 - 3.1        2.3 - 3.1
                          7            0.48 - 0.65      1.9 - 2.5
                         14            n.d. - n.d.      1.35 - 1.7
                       60 - 65                          0.3 - 1.25
                       90 - 92                          0.3 - 0.7
                      120 - 124                         0.15 - 0.3
                      150 - 155                         n.d. - 0.2

    Second year

    1 × 5 kg/ha           0               2.9              3.1
                          7               0.48             1.9
                         14               n.d.             1.35
                         59                                0.85
                         92                                0.65
                        120                                0.35
                        150                                0.3

    Table 9.  Degradation of Azocyclotin (25% w.p.) in aquarium water

    Storage       Analysis by                  Analysis by
    time          triazole meth.             organotin method
    in days                                                          
                  Azocyclotin         Tricyclohexyl     Dicyclohexyl
                  + triazole *        tin*              tin *

      0                                   8.95             0.26
      7                                   9.0              0.25
     28               7.6                 7.6              0.33
     49               7.9                 5.9              0.19
     71               5.3                 3.2              0.36
     91               5.3                 2.7              0.29
    120               5.3                 2.75             0.14
    150               5.6                 3.0              0.14

    *  All results calculated as azocyclotin (mg/kg).


    Residues of azocyclotin can be measured by two different methods
    developed by Möllhoff (1977a).

    Triazole method (parent compound + metabolite II)

    Plant, soil and water samples are extracted with isopropanol followed
    by chloroform, and cleanup of extract by precipation.  The final
    determination is a GLC procedure using thermionic N-detector (AFID)
    giving response to the triazole, and with a limit of determination of
    0.1 - 0.2 mg/kg, expressed as azocyclotin.  Azocyclotin (I) and
    1,2,4-triazole (II) cannot be distinguished by this method.

    This method determines that portion of the molecule which is split off
    first from the tin atom, i.e. the 1,2,4-triazole moiety.
    Accordingly, residues of azocyclotin measured by the triazole method
    usually drop relatively fast below limit of determination, while
    remaining organotin compounds can only be determined by method B.

    Organotin method (parent compound + metabolites III + IV)

    Plant, soil, water and laboratory animal feed samples are macerated
    with water and treated with hydrobromic acid in acetone, and
    thereafter extracted with hexane.  The hexane extracted residue in
    ethyl ether is reacted with methyl magnesium chloride and hydrolysed.
    The methylated compounds, tricyclohexyl methyl tin and dicyclohexyl
    dimethyl tin, which are formed from azocyclotin and metabolites III
    and IV are cleaned up on Florisil and gas chromatographed using a
    flame photometric detector (FPD) with a 394 nm filter.  The limits of
    determination are 0.05 - 0.1 mg/kg.

    Azocyclotin (I) and cyhexatin (III) cannot be distinguished by this
    method, but the method permits determination of the sum of these two
    compounds in parallel with determination of metabolite IV
    (dicyclohexyl tin oxide).

    The proportion of IV in the total residue measured by the organotin
    method is usually less than 10% in plants, and between 10 and 20% in
    soil, whilst metabolite V (cyclohexyl stannoic acid) is of little
    significance as residue.  This latter metabolite V could be determined
    by the organotin method if chloroform is used instead of hexane for
    the extraction.  The organotin method has multiresidue method
    characteristics as it permits the simultaneous determination of
    several chemical entities, in this case partially alkylated or
    arylated tin compounds (cfr. Steinmeyer et al., 1965, Heubert &
    Wirth, 1975, Figge et al., 1977 and Wright et al., 1979) by
    gaschromatographic separations after reaction with methyl magnesium
    chloride or with butyl lithium.  The latter alkylation agent deserves
    special attention because the alkylation seems to proceed very
    smoothly producing compounds with molecular weight of the same range.
    A more convenient isothermal GLC technique is thereby facilitated.


        National Limits and associated pre-harvest intervals which have
    been reported to the meeting are shown in Table 10.

    Table 10.  National MRLs and Safety Intervals

    Country    Crop                        MRL         Interval
                                         in mg/kg      in days

    Chile      fruits                                    15
    Cyprus     pome and stone fruits,
               citrus                                    21
    Germany    bush and runner beans                     14

    F.R.G.     pome fruit                                14
               grapes (except
               table grapes)                             35
               hops                       50.0
               pome fruits                 2.0
               wine grapes                 2.0

    Morocco    pome fruit                                28

    New        pipfruit                                  14
    Zealand    stone fruit                               14

    South      apples                      0.5            3
    Africa     pears                       0.5            3
               peaches                     0.5           21


    Azocyclotin is an organotin acaricide used against spider mites on
    fruits and vegetables, especially recommended for the control of
    strains which are resistant to other chemicals e.g.
    organophosphorous compounds.  It is formulated in wettable powders (25
    and 50%) and marketed in most continents.

    In plants, animals, soil and water, azocyclotin (I) is degraded by an
    initial off-splitting of 1,2,4-triazole (II) from tricyclohexyl tin
    hydroxide (III) identical with cyhexatin, followed by stepwise
    formation of cicyclohexyl tin oxide (IV) and monocyclohexyl stannoic
    acid (V) through the loss of the three cyclohexyl rings from the
    central Sn-atom.

    The first degradation step by splitting off of 1,2,4-triazole is a
    relatively fast process, and the 1,2,4-triazole moiety disappears to

    levels at or below the limit of determination shortly after treatment
    of plants or after application to soil or water.  The triazole
    probably disappears from plants by volatilization.

    The remaining organotin compounds, cyhexatin and its further
    metabolites, are more persistent, and dissipation of the total
    organotin residues is mainly governed by a process of growth dilution
    on most plants and vegetables after application.  But compounds III,
    IV and V are found as simultaneous residues in variable ratios, and
    with a limited amount of inorganic Sn also present.  In a single study
    with soil, inorganic Sn was found at the level of 6-19% of total

    Half-lives of organotin residues in soil varied from 50-90 days in
    field studies and from 200 days to one year under laboratory
    conditions.  Vertical movement or leaching in soils are found to be
    minimal or unlikely.

    Residues of azocyclotin (as organotin) in apples, beans, eggplants and
    strawberry are at or below limit of determination after application at
    recommended use levels and appropriate waiting periods, while
    significant residues were found in most cases on grapes.  After
    processing, up to 25% of residues in grapes was carried over to must,
    but without any measurable transfer of residues to wine.

    Two gas chromatographic methods are available for the determination of
    azocyclotin.  The one is based on determination of the 1,2,4-triazole
    moiety and it will not distinguish azocyclotin (I) from the triazole
    (II).  Residues by this method usually drop relatively rapidly to
    below the limit of determination, after which residue pattern cannot
    be distinguished from that which follows treatment with cyhexatin.

    The other method is an organotin method developed in recent years,
    which permits determination of organotin metabolites III, IV and V
    individually, while it will not distinguish azocyclotin (I) from
    metabolite III.  Metabolite V is of little significance as residue. 
    It is determined by the same method as I + III and IV, but only after
    separate extraction procedure.


    The following guideline limits for azocyclotin are recommended on the
    basis of data resulting from supervised trials.  They refer to the sum
    of organotin compounds expressed as azocyclotin.

                      Limit           Pre-harvest interval on which
    Commodity         (mg/kg)         recommendation is based

    Apples            0.1*                     21 days
    Egg plants        0.1*                     30 days
    Grapes                                     35 days
    Kidney Beans      0.2                      21 days
    Strawberry        0.1*                     14 days

    The Meeting realized that recommendations in certain cases are
    incompatible with earlier recommendations on cyhexatin from which
    azocyclotin residues will be undistinguishable shortly after
    application.  This may be due to somewhat differing use patterns for
    the two compounds, but partly also to the fact that a majority of
    earlier data derives from use of another analytical method, i.e.
    colorimetric, total Sn-determination.  Therefore, it is suggested that
    special efforts should be made at the international level to collect
    and review information on developed use patterns and residue data
    derived from new methodology for cyhexatin.

    Further work or information Required

    By 1980

    As residues from azocyclotin and cyhexatin cannot be distinguished
    shortly after application, information on use patterns and on residue
    data for both compounds, especially for cyhexatin, should be reviewed
    before residue limits for the two pesticides can be harmonized.


    Bayer, A.G.  Various reports on azocyclotin residues in fruit,
    vegetables and soil (1978), Unpublished.

    Figge, K., Koch, J., Lubba, H. - Beitrag zur gaschromatographischen
    Analyse von Organozinn-Stabilisatoren für Plyvinylchlorid. J.
    Chromatogr. 131, 317-327.

    Möllhoff, E.  Methode zur gaschromatographischen Bestimmung des
    Akarizids Peropal und seiner Metaboliten in Pflanzen, Böden, Wasser
    und Kleintierfutter. Pflanzenschutz-Nachr. Bayer 30, 249-263 (1977a).

      Abbau und Metabolismus von Peropal im Boden. Bayer AG, Report
    RA-11/77 (English version) (1977b).

      Abbau von Peropal in Aquarienwasser (geschlossenes System). Bayer
    AG; Report RA-815/77 (1977c).

    Neubert, G., Wirth, H.O. - Zur Analytik con Organozinnstabilistatoren.
    Z. Anal. Chem. 273, 19-23.

    Steinmeyer, R.D., Fentiman, A.F., Kahler, E.J., - Analysis of alkyltin
    bromides by gas liquid chromatography. Analytical Chem. 37, 520-523.

    Wolf, W., Lippert, K.D., Figge, K. - Übber das Verhalten des Akarizids
    "Tricyclohexylzinn-1,2,4-triazolid" und seiner Abbauprodukte im
    Okosystem "Buschbohnenkulture". Natec, Gesellschaft für
    naturwissenschaftlinch-technische Dienste mbH., Projekt NA 76 00 43,

      Uber das Abbauverhalten des Akarizids "Tricyclohexylzinn-1,2,4-
    triazolid"in Standardboden. Natec, Gesellschaft für naturwissen-,
    schaftlich-technische Dienste mbH., Project NA 76 00 43, (1977b).

    Wright, B.W., Lee, M.L., Booth, G.M. - Determination of
    triphenyltinhydroxide derivatives by capillary GC and Tin-selective
    FPD.  Journ. High Resolution Chrom. and Chromatography Comm. S. 189.

    See Also:
       Toxicological Abbreviations
       Azocyclotin (Pesticide residues in food: 1981 evaluations)
       Azocyclotin (Pesticide residues in food: 1983 evaluations)
       Azocyclotin (Pesticide residues in food: 1989 evaluations Part II Toxicology)
       Azocyclotin (JMPR Evaluations 2005 Part II Toxicological)