A simple high-pressure liquid chromatographic method for the simultaneous determination of vitamins A and E in animal feeds and foods has been developed and evaluated. After saponification and extraction the sample was run on a reversed-phase column with water-methanol as the mobile phase. The detector was an u.v.-lamp at 280 nm. The method has been tested on different types of feeds and foods containing between 2-30 pg vitamin A g-1 of sample and 5-300 pg vitamin E 8-1 of sample.The recovery of added vitamins was 86 % for retinylacetate and 91 % for cr-tocopherylacetate with a standard deviation of 3 for both. Results of the proposed procedure agreed well with those obtained by other methods.

A simple, rapid method, based on high performance liquid chromatography, h.p.l.c., is described for the determination of olaquindox in pig feeds. The drug is extracted from the feed by use of a methanol-water mixture, an aliquot is injected on to the h.p.1.c.-column and quantified by u.v.-detection. The method has been tested on feeds and premixes containing olaquindox between 1-400 mg kg-1.

A simple method for the assay of the coccidiostat clopidol by high performance liquid chromatography (h.p.1.c.) is described. After extraction the solution is neutralised and filtered and injected on the h.p.1.c.-column. It is quantified by u.v.-detection. The method has been tested on commercial feed samples. The agreement with a standard reference method is good. The precision of the proposed method has a standard deviation of 2%. The recovery of added clopidol is 101 % with a standard deviation of 2.4%. No interferences to the method have been found. Assay of the coccidiostat clopidol in animal feed by h.p.1.c.Clopidol (3,5-dichloro-2,6-dimethyl-4-pyridinol, Coyden) is a coccidiostat, used at levels of lo& 200 mg kg-1 of feed in poultry feeds.Existing methods for the assay of this chemical in feeds are tedious and involve toxic reagents. After extraction by alkaline methanol the extract is cleaned up on an alumina column and separated on an anion exchange column before being measured either by spectrophotometry or gas-liquid chromatography.1,zIn this paper the use of a high-performance liquid chromatographic h.p.1.c. method is proposed instead. The proposed method using a reversed-phase column is much simpler and faster than the existing older ones. Neither does it involve the use of toxic reagents. After extraction by ammoniacal methanol, the extract is neutralised and filtered. After injection on a reversed-phase column the absorbance of the clopidol peak is measured and the amount of clopidol present in the feed calculated. Experimental 2.1, Apparatus1. An LDC 711-74, pulse-free pump, equipped with a 10 pI high-pressure injection-loop also from LDC. 2.A 25 cm x 3.2 mm stainless steel column containing Spherisorb ODS 5 pm. AChromatonix 220 U.V. detector with a 20 pl flow cell. The detection wavelength used was 254 nm. 4.A Hitachi 165 recorder for recording the chromatograms. 5. Mobile phase. A mixture of 30% methanol and 70% water as eluent. This was degassed before use by placing in an ultrasonic bath for 5 min. The flow-rate was 20 ml h-l and the pressure drop over the column under these conditions was about 10 MPa. 6. ChemicalsAll chemicals were of analytical reagent grade. Clopidol was a gift from Dow Chemical Co. Ltd. Shaker. A shaker with wrist-type action from New Brunswick Sci. Corp. Q Present address: ARLA-Mjolkcentralen, S-10546,