Preliminary to conducting a collaborative study on a method for copper in serum, methods used by a selected group of laboratories were surveyed. The responding laboratories were supplied with a Youden pair of bovine serum samples and requested to use their current method for serum copper. Results of the analyses and the methods used were evaluated; hypotheses were developed in our laboratory to explain some of the interlaboratory variation. For the AAS method chosen, each of 12 collaborating laboratories analyzed one blind duplicate and 2 Youden pair of serum samples. A commercially available external control serum with a certified level of copper and a 1000 mg copper/L standard were also submitted. The method requires the serum to be diluted 1 + 1 with distilled water and the standards to be diluted with 10% glycerin to approximate the viscosity of the diluted serum. The intralaboratory coefficients of variation (CV) ranged from 2.24 to 4.40% and the interlaboratory CV ranged from 2.56% to 6.05%. The method has been adopted official first action.
Oosporein (Fig. l), a nephrotoxic fungal metabolite, is produced by Penicillium, Acremonium, Oospora, and Chaetomium species. Unlike the mycotoxins ochratoxin and citrinin, which affect both the kidney and the liver, oosporein affects only the kidney. Oosporein has been demonstrated to cause gout and kidney nephrosis in broiler chicks and turkeys. 6,7 The recent development of a sensitive thin-layer chromatographic (TLC) screening method for oosporein in poultry rations 9 has provided a means to determine whether oosporein is present in grains and determine if it is a causative factor in renal disease in poultry.In this paper, we report on chemical ionization (CI) mass spectral investigations of oosporein for the purpose of confirming TLC tests for the presence of oosporein in samples of poultry rations. Mass spectrometry (MS) has recently become a routine tool for confirmation and identification of various toxicants encountered by Veterinary Diagnostic Laboratories (F. Ross, personal communication). Most reports 2,4 on MS in diagnostic toxicology have involved the conventional ionization technique of electron impact (EI). Only in the mycotoxin area have other ionization methods been widely studied. 1,8 In the case of oosporein, CI provides a clearly superior alternative to EI.For this study, oosporein was isolated in pure form from a culture of Chaetomium trilaterale under conditions previously described. 6 All mass spectra were obtained on a tandem mass spectrometer." The EI spectrum at 70 eV by Direct Exposure Probe (DEP) was similar to that previously reported,' verifying the purified standard. Major ions included the following: m/z (relative intensity); M+ at 306 (48), 250 (l0), 222 (38), 194 (12), 167 (18), 138 (28), and 83 (100). The positive ion CI (PCI) spectrum was obtained using methane reagent gas, with source temperature of 150 C, 70 eV ionizing voltage, and DEP introduction. Major ions included the expected (M + 1) + at 307 (100) with fragment ions of 279 (18), 222 (5), 131 (7), and 83 (9) in addition to the reagent gas adduct ions at 321 (5) {M + 15} + and 335 (10) {M + 29} + . Methane negative ion CI (NCI) yielded the most interesting results. In addition to the M-at 306 (48), (M + 2) -at 308 (100) was present. The existence of (M + 2) -is most likely due to reduction of one of the quinones to hydroquinone under the electron capture conditions of the reagent gas. Other major negative ions included 290 (3l), 274 (4), and 154 (3), in addition to the reagent gas adduct ions at 320 (10) {M + 14} -and 334 (8) {M + 28} -. The fragment ion of m/z 290 further supports the existence of a hydroquinone. TheFigure 1. The structure of oosporein, 3,3',6,6'-tetrahydroxy-2,2'-dimethyl-5,5'-bi-p-benzoquinone. m/z 290 is most likely due to the loss of H 2 O from the (M+ 2) -as opposed to the unlikely loss of 16 from the parent M-(m/z 306). Further proof of the hydroquinone was obtained from the MS/MS daughter spectra of 308 -which included 290. Tandem MS of 306 -did not show a daughter ion of 290 or 288, which c...
Eleven collaborating laboratories conducted replicate analyses on 4 blind duplicate pairs of bovine liver samples that either had naturally acquired copper levels or were spiked with one of 3 copper levels. A National Bureau of Standards Bovine Liver sample (SRM 1577, 193 ± 10 mg copper/kg) and a 1000 mg copper/L standard were also submitted to the collaborators. The method requires the tissue to be digested with concentrated HN03 at 60°C, diluted to volume with water, and analyzed by atomic absorption spectrophotometry. The intralaboratory coefficients of variation (CV„) ranged from 5.6 to 19%; the interlaboratory CVX values ranged from 7.1 to 21%. The lower limit of detection was estimated to be 1 mg copper/kg tissue. The method has been adopted official first action.
Fluoride concentration in bovine urine is determined by using a selective ion electrode. Urine is buffered and measured against known fluoride (F) standards. The method is applicable to 2 to 40 mg F/L without further dilution. Typical normal urine contains less than 10 mg F/L. Concentrations greater than 10 mg/L support a clinical diagnosis of fluorosis in cattle. Repeatability coefficient of variation (CV) ranged from 1.6 to 3.5℅ for F concentrations of 3.2-13 mg/L. Reproducibility CV ranged from 0.3 to 7.3℅ for F concentrations of 7.0-17.2 mg/L.
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