The Use of Extraction on C18-Silica-Modified Magnetic Nanoparticles for the Determination of Ciprofloxacin and Ofloxacin in Meat Tissues

A simple, fast, and low-cost method of extraction using magnetic nanoparticles was developed for sample preparation in the determination of ciprofloxacin and ofloxacin in meat tissues with the use of capillary electrophoresis. This study is the first utilization of silica-coated magnetic nanoparticles with attached C18 chains to extract fluoroquinolones from meat tissues. This method is therefore characterized by a very simple sample preparation procedure, but on the other hand, by satisfactory precision and accuracy. Magnetic nanoparticles with an appropriately modified surface were placed in an Eppendorf tube, then conditioned with methanol, next rinsed with water and, finally, a homogenized tissue sample was added. At the neutral pH of the sample solution, these compounds do not have a charge and are able to adsorb on the modified particles. After extraction, the nanoparticles were dried and, then, desorption of analytes was conducted with the use of a mixture of 0.1 mol/L HCl and acetonitrile (1:1). This approach made it possible to purify the sample matrix and to obtain satisfactory LOQ levels for the method using the CE technique with UV-Vis detection. In this method, the LOD and LOQ values for both analytes were 0.04 nmol/g tissue and 0.15 nmol/g tissue, respectively. The calibration curves were linear in the entire concentration range, and the accuracy and the recovery of the method were at the satisfactory levels. The square value of the linear correlation coefficients (R2) for Cpx and Ofx were 0.9995 and 0.9992, respectively. The precision value of the method was within the range of 3-11% and accuracy was in the range of 93-110%.

Development of the Chromatographic Method for Simultaneous Determination of Azaperone and Azaperol in Animal Kidneys and Livers

A precise and accurate method for the simultaneous determination of azaperone and azaperol in meat tissues has been developed. This paper describes the first method to be so fast, simple, and useful, especially for many laboratories that do not have sophisticated equipment. This method is based on LC separation and UV-Vis detection. During the sample preparation, the meat tissue was homogenized in acetonitrile at a ratio of 1:4 (tissue weight:acetonitrile volume). The homogenate was centrifuged, the supernatant was evaporated in a lyophilizator, and then the evaporation residue was dissolved in 20 µL of ethanol. For deproteinization, 15 µL of perchloric acid was added, and the sample prepared in this way was injected into a chromatographic column and analyzed using reversed-phased HPLC. The mobile phase consisted of 0.05 mol/L phosphate buffer pH 3.00 (component A) and acetonitrile (component B). UV detection was conducted at 245 nm. The experimentally determined LOQs were 0.25 µg/kg for azaperone and 0.12 µg/kg for azaperol. For both analytes, the calibration curves showed linearity in the tested concentration range from 50 to 300 µg/kg of tissue. The accuracy of the presented method did not exceed 15%, and the recovery was in the range of 85-115%. A validated analytical procedure was implemented for the analysis of various animal tissues for their content of azaperone and azaperol.

Simultaneous Determination of Ciprofloxacin and Ofloxacin in Animal Tissues with the Use of Capillary Electrophoresis with Transient Pseudo-Isotachophoresis

We have developed a precise and accurate method for the determination of ciprofloxacin and ofloxacin in meat tissues. Our method utilizes capillary electrophoresis with a transient pseudo-isotachophoresis mechanism and liquid–liquid extraction during sample preparation. For our experiment, a meat tissue sample was homogenized in pH 7.00 phosphate buffer at a ratio of 1:10 (tissue mass: buffer volume; g/mL). The extraction of each sample was carried out twice for 15 min with 600 µL of a mixture of dichloromethane and acetonitrile at a 2:1 volume ratio. We then conducted the electrophoretic separation at a voltage of 16 kV and a temperature of 25 °C using a background electrolyte of 0.1 mol/L phosphate–borate (pH 8.40). We used the UV detection at 288 nm. The experimentally determined LOQs for ciprofloxacin and ofloxacin were 0.27 ppm (0.8 nmol/g tissue) and 0.11 ppm (0.3 nmol/g tissue), respectively. The calibration curves exhibited linearity over the tested concentration range of 2 to 10 nmol/g tissue for both analytes. The relative standard deviation of the determination did not exceed 15%, and the recovery was in the range of 85–115%. We used the method to analyze various meat tissues for their ciprofloxacin and ofloxacin contents.

Determination of homocysteine thiolactone in human urine by capillary zone electrophoresis and single drop microextraction

A simple, fast, sensitive and reproducible capillary zone electrophoresis (CZE) method with single drop microextraction (SDME) for determination of homocysteine thiolactone (HTL) in human urine has been developed and validated. The method is characterized by good precision, high accuracy, short analysis time and low consumption of reagents. The procedure consists only of few steps: urine sample centrifugation, dilution with phosphate buffer and methanol, chloroform addition onto the top of donor phase, on-line SDME in CE system, sample separation by CZE and ultraviolet detection of HTL at 240 nm. The background electrolyte was 0.1 M pH 4.75 phosphate buffer. Effective separation was achieved within 6.04 min under the separation voltage of 24 kV (~110 μA). The LOQ and LOD for HTL were 50 and 25 nM urine, respectively. The calibration curve in urine showed linearity in the range of 50-200 nM, with R² 0.9995. The intra- and inter-day precision and recovery were 4.0-14.5% (average 8.7% and 9.3%) and 92.7-115.5% (average 103.6% and 104.8%), respectively. The procedure was successfully applied to analysis of urine samples.