Simultaneous Determination of Esafoxolaner, Eprinomectin, Praziquantel, BHT and Their Related Substances in a Topical Finished Product by a Single Reversed-Phase High-Performance Liquid Chromatography Method.

The topical product with three active pharmaceutical ingredients (APIs), namely, esafoxolaner, eprinomectin and praziquantel has demonstrated its efficacy in the treatment of cats with mixed infections with ectoparasites and nematodes and cestodes. A reversed-phase high-performance liquid chromatography (RP-HPLC) method has been developed and validated for assay and determination of related substances peaks of three APIs including the assay of antioxidant butylated hydroxytoluene (BHT) in the finished product. Analytes were separated on a short Zorbax SB-C18 column (50 × 4.6 mm I.D., 5 µm particle size, pore size: 80 Å) with gradient elution at 40 °C column temperature. Analytes were detected at 245 nm for praziquantel, esafoxolaner, eprinomectin and their degradation products. BHT and eprinomectin degradation product 8a-oxo-B1a were detected at 280 nm. All analytes of interest were adequately separated within 40 min. The assay for praziquantel, esafoxolaner, eprinomectin and BHT was conducted against their corresponding external reference standards. The related substances peaks of each API were determined by peak area and relative response factor against total peak area of their corresponding API peak in sample solution. This method has been demonstrated to be accurate, robust, specific and stability indicating.

Quantitative Analysis of Polycyclic Aromatic Hydrocarbons at Part Per Billion Levels in Fish Oil by Headspace Solid-Phase Microextraction and Gas Chromatography-Mass Spectrometry (HS-SPME-GC-MS).

Headspace solid-phase microextraction (HS-SPME) was used in combination with gas chromatography-mass spectrometry (GC-MS) for the analysis of polycyclic aromatic hydrocarbons (PAH) at part per billion levels in fish oil samples collected from menhaden fish. The method was initially developed using fish oil from capsules spiked with a standard PAH mixture. The final HS-SPME-GC-MS method presented a linear range from 3 to 1,500 ng/g, with precision for most analytes <10% relative standard deviation. The limits of detection varied from 1 to 7 ng/g depending on the analyte. Real sample analysis was done on menhaden fish oil extracted from fish collected off the coasts of New Jersey and Louisiana. Naphthalene, fluorene, fluoranthene, pyrene, anthracene were detected at low levels of 70-180 ng/g in the real samples. The concentrations of PAHs detected in the real samples were well below established levels of concern for PAHs in finfish.

"Retention projection" enables reliable use of shared gas chromatographic retention data across laboratories, instruments, and methods.

Gas chromatography/mass spectrometry (GC/MS) is a primary tool used to identify compounds in complex samples. Both mass spectra and GC retention times are matched to those of standards; however, it is often impractical to have standards on hand for every compound of interest, so we must rely on shared databases of MS data and GC retention information. Unfortunately, retention databases (e.g., linear retention index libraries) are experimentally restrictive, notoriously unreliable, and strongly instrument dependent, relegating GC retention information to a minor, often negligible role in compound identification despite its potential power. A new methodology called "retention projection" has great potential to overcome the limitations of shared chromatographic databases. In this work, we tested the reliability of the methodology in five independent laboratories. We found that, even when each lab ran nominally the same method, the methodology was 3-fold more accurate than retention indexing because it properly accounted for unintentional differences between the GC/MS systems. When the laboratories used different methods of their own choosing, retention projections were 4- to 165-fold more accurate. More importantly, the distribution of error in the retention projections was predictable across different methods and laboratories, thus enabling automatic calculation of retention time tolerance windows. Tolerance windows at 99% confidence were generally narrower than those widely used even when physical standards are on hand to measure their retention. With its high accuracy and reliability, the new retention projection methodology makes GC retention a reliable, precise tool for compound identification, even when standards are not available to the user.