Liquid chromatography tandem mass spectrophotometry (LC-MS/MS) has been developed for simultaneous determination of four antibiotics which have coccidiicidal effects including monensin, dimetridazole, sulfadimethoxin, and sulfadimidine in feed samples. The research conducted by using mobile phase A (0.1% formic acid solution; 10 mM ammonium formate) and phase B (MeOH; 0.1% formic acid; 10 mM ammonium formate) with C18 reversed-phase chromatography column (2.1 × 1.5 mm, ID 3.5 μm) simultaneously and successfully identified these four antibiotics in a short time about 10 minutes. The method detection limits and quantification limits for all analytes were 15.0 and 45.0 µg/kg, respectively. The calibration curve of the method was in the range of 45 - 1,500 µg/L. The method was validated for high accuracy, efficiency and applied to analyze the feed samples on the Hanoi market.
Dietary supplements are currently popular because of their natural origin, especially male enhancement products. However, some of these products have been found to contain erectile dysfunction drugs that inhibit the enzyme phosphodiesterase-5 (PDE-5), leading to adverse effects on human health. In this study, capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D) was used to determine four PDE-5 inhibitors (including acetyl vardenafil, homosildenafil, hydroxy acetildenafil and mirodenafil) in dietary supplement samples. The optimum analytical conditions included electrolyte solution of 20 mM arginine (Arg)/acetic acid (Ace)/acetonitrile (ACN) 20% pH 6.5, silica capillary 50 μm inner diameter with effective length of 50 cm, separation voltage of 20kV, siphoning hydrodynamic injection at a height of 25 cm for 30 s. At the optimum analytical conditions, the limits of detection of acetyl vardenafil, homosildenafil, hydroxy acetildenafil, and mirodenafil were 2.1, 1.6, 2.3, and 1.3 mg/L, respectively. The analysis of four PDE-5 inhibitors by CE-C4D also showed good repeatability (< 5 %) and recovery (> 97 %). This method was further applied to simultaneously determine the amount of acetyl vardenafil, homosildenafil, hydroxy acetildenafil, and mirodenafil in three functional products. All four PDE-5 inhibitors were not detected in these samples. To demonstrate the utility of this method, the mixture of four PDE-5 inhibitors standard solutions was added to three samples. The recovery was between 98.8 % and 100.6%, illustrating the potential applicability of the method of determining PDE-5 inhibitors in dietary supplement samples.
Isocyanate is a common name for chemical compounds containing one or more - NCO groups. There have been many studies showing that isocyanates pose a risk to human health when exposed and can cause occupational poisoning. When absorbed into the body, the isocyanates will be converted into the corresponding amines. Therefore, the determination of these diamines in urine will contribute to the assessment of exposure to isocyanates. This article presents a study on simultaneous determination of 4,4′-methylenedianiline (MDA), hexamethylene diamine (HDA), isophoron diamine (IPDA) in urine by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The method detection limit (MDL) were 0.074, 0.059, and 0.053 ng/mL for HDA, MDA, IPDA, respectively. The method quantitation limit (MQL) were 0.243, 0.194 and 0.177 ng/mL for HDA, MDA, IPDA, respectively. The method's recovery ranged from 86.38 to 105.3% with the repeatability RSDr < 6%. The method was successfully applied to simultaneously determine the content of HDA, MDA and IPDA in 30 urine samples of workers at auto repair garages in Bac Ninh province. The results showed that HDA, MDA and IPDA were detected in these samples with different concentrations.
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