Cloxacillin methods

In a comparison with microbiological methods for penicillin in milk. Moats concluded that the TLC (75) and HPLC (78) methods described for milk were comparable in sensitivity for penicillin G and far more sensitive for cloxacillin. Other reported methods vary greatly in sensitivity. The two reported HPLC methods for... 

Antisera to cloxacillin/oxacillin/dicloxacillin and cefuroxime were also produced by similar procedures and successfully utilized in methods for the detection of these antibiotics in milk (34). Unfortunately, a number of other -lactams including aminopenicillins and some cephalosporins were not amenable to this mixed anhydride procedure. Thus, a carrier protein derivatization procedure was used to allow cross-linking of cephalosporins, such as cephataxime that has an acetoxy side chain, to ovalbumin. Because acetoxy groups react readily with the heterocyclic nitrogen atoms, the latter were introduced into ovalbumin through the carbodiimide-mediated derivatization of protein carboxyl groups with amino-methylpyridine (34). 

Apart from those homemade methods, numerous commercial kits including the EZ-screen -lactam card tests (Environmental Diagnostics, Inc., Burlington, NC), the CITE probe -lactam test (IDEXX Laboratories, Inc., Westbrook, ME), the LacTek -lactam test (IDETEK, Inc., Sunnyvale, CA), and the spot test for benzylpenicillin, cephapirin, and cloxacillin (Angenics, Inc., Cambridge, MA) are also available. 

Straub et al. (76) reported a method for the identification and quantification of penicillin G, ampicillin, amoxicillin, cephapirin, cloxacillin, and ceftiofur residues in milk using perfusive-particle liquid chromatography combined with ultrasonic nebulization electrospray mass spectrometry. According to this method, a 0.5 ml milk sample is diluted with an equal volume of a solution consisting of acetonitrile/water (1 1), and ultrafiltrated in a microseparation system with a 10000 da molecular mass cut-off filter. An aliquot of the ultrafiltrate is then analyzed on a 15 cm porous II R/H LC (7-8 m) perfusion analytical column using the chromatographic conditions shown in Table 29.3. Concentrations as low as 10 ppb could be readily determined in milk by electrospray mass spectrometric detection. 

D Hurtaud, B Delepine, P Sanders. Particle-beam liquid chromatography-mass spectrometry method with negative ion chemical ionization for the confirmation of oxacillin, cloxacillin and dicloxacillin residues in bovine muscle. Analyst 119 2731-2736, 1994. 

BenzylpenicUlin (PCG), phenoxymethylpeniciUin (PCV), oxacillin (MPIPC), cloxacillin (MCIPC), nafcilUn (NFPC), and dicloxaciUin (MDIPC), all of which are representative weakly acidic penicillins, are widely used as veterinary drugs for livestock. We have reported, in our previous studies, the applicability of sample cleanup with an ion-exchange cartridge, in combination with ion-pair HPLC, for the analysis of ionizable compounds. We therefore applied the same technique to develop an analytical method for the quantitative determination of these residual penicillins in bovine muscle, kidney, and liver. " ... 

The spots were detected by spraying with 0.25% w/v fluorescein sodium salt soln. The minimum amounts detectable with the method were 3.0 fig for phenoxymethyl penicillin K and 1.0 fig for ampicillin, penicillin G, penicillin GK, penicillin G sodium salt, cloxacillin, dicloxacillin and di-cloxacillin sodium salt Ref... 

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