EN 1528-4-1996 pdf download.Fatty food — Determination of pesticides and polychiorinated biphenyls (PCBs) — Part 4: Determination, contirmatoiy tests,miscelkrneous.
4 Determination
4.1 Gas chromatography
4.1.1 General
A suitable GC system, preferably equipped with separate heaters for injector, detector and column OVefl.s, St14)Ukl be use(L Although 11w choice of the different parts of the (X’ system is a matter for the experience of the analyst, the following general nconiinendations are fliade.
The detectors should be properly adjusted, according to the manufacturer’s instructions. ‘iriations in (Ictector sensilivity should be checked penodwally by veñfing the linearity of the calibration curves using standard solutions of pesticides.
The quantiticahofl unit of the gas chn)matographw system iweds to indude an integration system which pemiits the calculation not only of peak heights but also of iwak areas.
It has been found in practice that equivalent results can be achieved despite the adoption of (lifTerent Of conditions and (hflennt makes of instruments. On the other hand, spedtiug standard GC tanu1wters does not in any way guarantee that the quality of the results generated will be i(letlticai.
For typical Of conditions, see annex 11.
4.1.2 Columns
Either packed or capillary columns may be used. When packed colunui are to be used, then glass colunms of lengths between 1,5111 and 3 m and of internal diameter (Id.) 2 mm to 6 mm, are reconuiiencled, however, they are not statable for the separation of PCB congeners.
A robust, inert support should be used. Materials such as Gaschruin Q, Chromosorb WhIP, Anachrom Q in 125 p.m to 150 .uii (10(1 to 120 mesh), 150 p.m to 190 p.m (80 mesh to 100 mesh) or 190 p.m to 250 tm (60 to 80 mesh) ranges have been successfully employed.1)
— I 13’dflJCWtX)It Apiezon L
– Methylsiliconev DC11, DC-200, OV-l, OV-l01, SP-2100, SE-l0
Methylpltiylsihcotws: OV-17, OV-25, OV.61. SP.22F0, SE-62, SE-M;
— 1’Hfluoropnpyliuethylsilie nes: QF—I, 0V2 10, SF.2401;
PhenyIopwpyh1sAlicoiies IJB-1301, DB-1701, O225, XFA-60;
• Polyethylene glycol: Carbowax 20 M1) Stationary phases should be coated onto the suppoll with care, the ratio (lepen(ling Oil tlit’ support/phase COllthUUitiOfl chosen. Newly filled columns should be conditioned for at least 24 h at a temperature near the maximuni rvcommen(frd operating temperature with the type of stationary 1ihase used, and shouhi then 1w tested for their efficiency and selectivity at the required operating IenhIx’rature using standard mixtures of ititii1i. The end of the colunui should always be (hSCoIUiected from the detector during conditioning. Pure, dry nitrogen (oxygen-free, especially when u.sing aUl electron capture (leteetor (ECD)), or an argonJnwthane mixture (in the case of a pulsed ECD), 5110111(11w use(I as carrier gas for packed colunuis. The flow rate depezids on the size and type of cohinui used, Generally, gas flow rates shouki be eonlnlled as accurately as possible. Molecular sieve filters should be installed for all gas sIll)l)lies and regenerated regularly. Finally, GC conditions (cotunut length, stationary phase type, injector, (fricetor an(l column temperatures, gas flow rates, etc.) should 1w 511(11 that the sepaiath)fl of the pesticides and PCIIs likely to be present is as coIlij)lete as possible, Capillary GC has a sepantuon i’’- superior to that of packed colunuis. This tedinique is reeonunended especially in the case of complex extracts. Fused silica rolunms having an internal (Iuuueler of 0,20 nun to 0,5 nun and a length of between 20 rn and 6Oni have proved particularly satisfactory hecaILse of their separation effidcnc senice life and fllecharu(’al I)n)IwrtI(’s. ‘eVkk’4iore colunms having an internal (hameter of 0,5 nun to 0,8 nun may aLso be useful in sonw cases. The following stationary iilies are frequently used as coatings:
– OV 225 (equiileiit to DR-225, SIL 43-CR, SPB-2J0,
– WAX (equivalent to DH-%X, CP-WAX-52-CB, Caiiowax 20 M, etc.>
A test fur separation efficiency of eapillaiy columns, is given in 7.2 of EN 1528-1: 1906.
4.1.3 Injection techniques
U1OUS H1jC( )fl techniques are useful such as:
a) Grob splitle Injection.
b) On-column injection.
c) Progranuned 1Iniperattue Vaporization (PTV) lection.
The applicability of these teehmques depends on the a)panItus used and on special requin-nwnts. 42 Preliminary tests
Detennine the linear dynamic range of detector x)n.se lUider the actual GC conditions used by
injecting dilute standard solutions.
Inject into the gas chromatograph an apl)n)pnate voltune (between 1,0 1d and 10 1.d (lepen(hng on the s3&%teln) of the purified extracts obtained according to the analytical method utsed. The ehromatogrwn so obtained should enable both the Identity and the apj)roXuuate concelamlion of the CompoWds present in the extracts to he established.
4.3 Detennination
Make sure that all measun’nwnts are performed within the linear dynamic range of the system.
Prepue iii lea# two stan(lard solutions of the pesticides or PCB eungeners identified in the solvent to Is’ used for the final extract (usually light petroleLuu orn—hexane). Their coned it rations sh( 1111(1 efleOuIlI)aSS 11w probable concentration expected in the final extracts. Then inject equal volumes of the final extracts obtained and of the two or fliort’ Sfl(liUd solutions Into the gas chromatograph. It is essential that the injection of the purified portions of the sample
Uacts is 1)1’ led and f()th)Wed by injection of the standard solutions.
Measure (lie peak areas or pealc heights. The resulis ol)Lalned front any two njevUoris of the same stiuidard.EN 1528-4-1996 pdf download.