Evaluation of the order of hierarchical structures for the calculation of method uncertainty using nested and other designs.

Several methods have been used to calculate method uncertainties using data from a previous publication. The major effort was to study the effect of changing the primary factor of the nested (hierarchical) design from concentration to matrix and then analyst. In the measurement of fluoroquinolones in honey, it was observed that when matrix was the primary factor the uncertainty values were generally slightly larger than when concentration or analyst were the primary factors.

A new approach to the analysis of nicarbazin and ionophores in eggs by HPLC/MS/MS.

An HPLC/MS/MS method has been developed and validated for the quantification and confirmation of nicarbazin and ionophores (lasalocid, monensin, salinomycin, and narasin) in eggs. Nicarbazin is determined in the negative electrospray mode with a basic mobile phase that supports creation of negative ions. Consequently, our ability to maintain instrument sensitivity over time has significantly improved.

Quantitation of fluoroquinolones in honey using tandem mass spectrometry (LC-MS/MS): nested validation with two mass spectrometers.

A number of drugs in the quinolone and fluoroquinolone families, approved for veterinary treatment of food animals by various countries, may be used to treat bee diseases and thereby contaminate honey. An LC-MS/MS method has been developed for the quantification of the quinolones: flumequine, nalidixic acid, oxolinic acid, and pipemidic acid; and the fluoroquinolones ciprofloxacin, danofloxacin, difloxacin, enrofloxacin, norfloxacin, ofloxacin, orbifloxacin, marbofloxacin, sarafloxacin, and sparfloxacin. A method-matched calibration curve is used with several internal standards, i.

Quantitation and validation of macrolide endectocides in raw milk by negative ion electrospray MS/MS.

Macrolide endectocides (abamectin, doramectin, emamectin, eprinomectin, ivermectin, and moxidectin) are used to treat animals against a variety of parasites. They are approved for use with food animals, but require long withdrawal times. Two compounds, eprinomectin and moxidectin, are approved for use with lactating cattle and have established maximum residue limit values of 20 and 40 microg/kg, respectively.

Ivermectin use and resulting milk residues on 4 Canadian dairy herds.

The Canadian gFARAD was contacted for milk withdrawal recommendations after multiple cases of topical ivermectin use in lactating dairy cows. The following 4 cases included pertinent milk residue information and illustrate the challenges faced by producers, veterinarians, and regulatory authorities when ivermectin use occurs in dairy cows.

Quantitation and validation of fluoroquinolones in eggs using liquid chromatography/tandem mass spectrometry.

Fluoroquinolone antibiotics are labeled for very limited veterinary use for treatment of some animals and pets, but they are not authorized for food animals in Canada, including egg-producing birds. Because they are approved for other animals, however, fluoroquinolones may appear in eggs through off-labeling or accidental use. This method is capable of quantitating and confirming the presence of 4 fluoroquinolones, ciprofloxacin, danofloxacin, enrofloxacin, and sarafloxacin, over the concentration range 1 to 60 microg/kg (ppb) using 2 internal standards, norfloxacin or lomefloxacin.

Positive and negative electrospray LC-MS-MS methods for quantitation of the antiparasitic endectocide drugs, abamectin, doramectin, emamectin, eprinomectin, ivermectin, moxidectin and selamectin in milk.

Avermectin endectocides are used for the treatment of cattle against a variety of nematode and arthropod parasites, and consequently may appear in milk after normal or off-label use. The compounds abamectin, doramectin, and ivermectin, contain only C, H and O and may be expected to be detected by LC-MS in negative ion mode. The others contain nitrogen in addition and would be expected to be preferentially ionized in positive mode.