title: Determination and confirmation of malachite green and leucomalachite green residues in salmon using liquid chromatography/mass spectrometry with no-discharge atmospheric pressure chemical ionization.
abstract: A liquid chromatography/mass spectrometry (LC/MS) method was developed to quantitate and confirm residues of leucomalachite green (LMG) in salmon tissue after their conversion to chromic malachite green (MG) in the extraction process. The method uses no-discharge atmospheric pressure chemical ionization (APCI) in conjunction with an ion-trap instrument to generate product-ion spectra. In the sample preparation procedure, salmon tissue is extracted with acetonitrile/buffer, the LMG residue is partitioned into methylene chloride, the LMG is converted to MG using an organic oxidizing agent, and the MG is isolated on alumina/propylsulfonic acid solid-phase extraction cartridges. The method was validated by fortifying salmon with different levels of LMG, and then detecting the residue as MG The LC/MS conditions, including a comparison of electrospray and no-discharge APCI, were evaluated and optimized. MG was not confirmed in any of the control tissue extracts, and all fortified samples analyzed during validation met the confirmation criteria as described. In addition to providing confirmatory data, this method can provide an alternative method for quantitation of MG in salmon. The recoveries of LMG measured as MG by this LC/MS method, at fortification levels of 1-10 ng/g were very high (86-109%), with low relative standard deviation(RSD) values (6.4-13%). The results agreed very closely with those obtained for the same extracts using an LCNIS procedure, indicating that matrix suppression was not an issue. The presence of LMG in salmon tissue samples fortified at 0.25 ng/g was confirmed by this method, with an average recovery of 70.1% and an RSD of 12.0%. Sample extracts from fish exposed to MG were also analyzed.
authors.affiliation: U.S. Food and Drug Administration, Animal Drugs Research Center, P.O. Box 25087, Denver, CO 80225-0087, USA. sherri.turnipseed@fda.hhs.gov
authors.forename: Sherri B
authors.initials: SB
authors.lastname: Turnipseed
authors.forename: Wendy C
authors.initials: WC
authors.lastname: Andersen
authors.forename: José E
authors.initials: JE
authors.lastname: Roybal
mesh_terms: D000814:Aniline Compounds / Q000032:analysis*; D000818:Animals; D002853:Chromatography, Liquid / Q000379:methods* / Q000592:standards; D005396:Fish Products / Q000032:analysis*; D005504:Food Analysis / Q000379:methods; D005506:Food Contamination / Q000032:analysis; D013058:Mass Spectrometry / Q000379:methods*; D012015:Reference Standards; D015203:Reproducibility of Results; D012394:Rosaniline Dyes / Q000032:analysis*; D012474:Salmon; D012680:Sensitivity and Specificity
chemical_list: D000814:Aniline Compounds; D012394:Rosaniline Dyes; C005095:malachite green; C015320:leucomalachite green