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and tyramine are sometimes found when the analyte is derivatized with DNS and FMOC.

On the other hand, OPA, which does not fluoresce by itself, can be used either pre-column and post-
column, or for on-column derivatization. OPA, generally used in pairs with active thiol compounds
such as 2-ME, 3-MP or NAC, solely reacts with histamine to form a specific fluorescent derivative.
This pre-column derivatization was applied for the analysis of histamine in tuna and grapefruit juice
[249]. The use of pre-column derivatization with OPA/2-ME was reported for the analysis of amines
such as histamine, tyramine and polyamines in wine, followed by reversed-phase column
chromatography with gradient elution and detection with ECD [250]. Post-column derivatization was
also used for the analysis of amines in dried herring, vegetables, fish and meat products, beers, malts,
and hops [251-254]. Detection limits of these samples were 0.3-1 ppm.

The use of on-column derivatization with OPA/NAC was applied to the determination of histamine and
its metabolite, 1-methylhistamine, in soy-bean products such as soy-sauce and bean paste (miso), and
fish [255], and for the simultaneous determination of histamine and polyamines with isocratic elution
[256]. These methods involve pretreatment of simultaneous deproteinization and extraction with
trichloroacetic acid, followed by clean-up with Amberlite CG-50, and formation of OPA fluorescent
derivatives using on-column derivatization, and chromatography on the reversed-phase column
(detection limit 0.5-20 ppm). On-column derivatization with OPA/NAC uses an alkaline eluent,
therefore the HPLC column should be tolerant towards alkaline, and a polymer based reversed-phase
column such as Asahipak ODP-50 was selected. Moreover, oncolumn derivatization with OPA/NAC
was applied for the analysis of amines in wine [257]. This application simplifies pretreatment procedure
using SPE (C18 or SAX) for clean-up. The detection limits were 0.1 -0.3 ppm.

Several automated on-line derivatization of amines were reported. For example, controlled by
computerized autosampler, derivatization was automatically carried out in the pre-column [258]; after
HPLC separation in the presence of ninhydrin in the mobile phase, derivatization was completed with
heating followed by VIS 546 nm detection [259]. This method might be categorized into a post-column
derivatization.

To perform on-line derivatization, HPLC instrumentation equipped with column-switching has been
developed. The reaction compounds of FMOC and amines in an autosampler syringe are introduced
into pre-column while excess reagent and co-existent materials are removed by the end-cut technique,
and then FMOC derivatives are forwarded to chromatographic separation and detection [260]; after
being purified on a cationexchange polymer pre-column, amines were backflashed from the pre-column
and labeled with OPA fluorophore in the presence of OPA/NAC in the mobile phase using on-column
derivatization, followed by chromatographic separation on a reversed-phase C18 column and detection
(Fig. 1.2.18). The method was applied for the analysis of amines in anchovy and dry sausage (Fig.
1.2.19) [261].

1.2.7.2—
Organotin

Organotin, a generic name for a tin compound whose tin and carbon are directly combined, is
represented by the chemical formula of RnSnX4-n . The value of Sn is four, and four forms of
tetra-, tri-, di- and mono compounds exist. R shows alkyl groups such as the butyl group, phenyl or allyl
groups. X reveals a halogen represented by chlorine, oxide, hydroxyl group or an anion. Organotin has
been used for fungicide, insecticide and wood preservatives, and also antifouling paints for ships and
fishing nets. During 1980 highly concentrated pollution oforganotin on cultured fish and seafoods was
revealed, and the malgrowth and malbreeding of cultured fish was feared. As for the effects on

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