Detection of incurred dihydrostreptomycin residues in milk by liquid chromatography and preliminary confirmation methods†

Abstract

An LC method for the determination of the aminoglycosides streptomycin (STR) and dihydrostreptomycin (DHS) in milk was developed/modified on the basis of published papers. Mean recoveries were 87 and 95% for STR and DHS, respectively. Recoveries are dependent on the concentration level and batch of solid-phase extraction columns used, and independent of fat content and homogenization. The relative standard deviations are 15.6 and 9.6% for STR and DHS, respectively, at a level of 100 micrograms kg-1. Limits of detection (8 and 12 micrograms kg-1, respectively) and quantification (12 and 18 micrograms kg-1, respectively) are far below the EU maximum residue limit of 200 micrograms kg-1. Lyophilized DHS samples can be used for internal control of the analysis as the DHS concentration is not influenced by the lyophilization process and subsequent storage at 6 degrees C. In incurred milk samples no false negative results of preliminary confirmation tests (Charm II Aminoglycoside test, Ridascreen Streptomycin ELISA) with respect to DHS concentrations > or = 20 micrograms kg-1 as determined by the LC method are observed. DHS concentrations of incurred samples determined by ELISA are higher than those obtained by the LC method. These differences were more pronounced with incurred than with spiked milk samples, thus leading to the conclusion that in incurred samples substances are present which co-react in the ELISA and which are not detected by the LC method.

High-performance liquid chromatographic determination of vertilmicin in rat plasma using sensitive fluorometric derivatization

“…1). The analysis of aminoglycosides are usually performed using pre-column [2][3][4][5][6][7][8] and post-column derivatization [9] methods, or other detections such as evaporative light scattering detection [10], pulsed electrochemical detection [11][12][13] and mass spectrometry [12,14,15]. Zhou et al [16] had reported an analytical method for veritlmicin in plasma and 1-fluoro-2,4-dinitrobenzene was used for derivatization.…”

Ion-pair Solid-Phase Extraction of Trace Amounts of Ionic Liquid Cations in Fresh and Seawater Samples

“…14 Additionally, salts of heptasulfonic acid were employed as IP reagents in the SPE preconcentration of dihydrostreptomycin from milk 15,16 or streptomycin from various other foodstuffs. 17 This reagent was therefore chosen for further studies in our research, such as determination of breakthrough volume, analytical performance parameters and applicability of the method.…”

On-line concentration of neomycin and screening aminoglycosides in milk by short capillary column and tandem mass spectrometry

“…An IS was prepared by dissolving tobramycin in precipitating solution to give a concentration of 10 lg/mL. Aminoglycoside-free milk samples were mixed with five different levels (1,4,8,16, and 64 lg/mL) of 1 mL neomycin aqueous solution in 10 mL volumetric flasks and added with milk to the mark to prepare the final neomycin concentrations in milk over the range of 0.1 -6.4 lg/mL for analytical calibration. Milk samples (10 lL) were added in Eppendorf vials (500 lL) and then IS solution (5 lL) was added.…”

“…Recently, several types of SPE columns have been commonly used for extraction of aminoglycosides in bio-samples, such as a strong-cation exchanger [11,12], a weak-cation exchanger [13,14], an RP C18 [15,16], and a mixed model of an ion exchanger combined with RP [17]. Using SPE column, targeting analytes could be cleaned up, purified, and concentrated easily from a complicated matrix.…”