ABSTRACT
A method for rapid determination of γ-hydroxybutyric acid (GHB) in beverages (water, sodas, beer) and urine was established by direct analysis real-time mass spectrometry (DART-MS). Samples were analyzed directly after dilution with mixture of methanol and water(1:1,V/V). Instrument parameter settings were optimized to obtain the sensitive and accurate determination of GHB. At the sample introduction speed of 0.5 mm/s, high intensity of[M-H]- ions for GHB were observed in the negative ion and selection ion monitoring mode by utilization of high purity helium gas at 350℃. For different samples of water,sodas,beer and urine,the limits of detection (LODs) (S/N=3) were in the range of 1-2 μg/mL, while the limits of quantification (LOQs) (S/N=10) were in the range of 3-5 μg/mL. The linear correlation coefficients of the standard curves with different sample matrixes were between 0.9899 and 0.9980. The recoveries were in the range of 80.8%-115.2% with the relative standard deviations of 1.9%-12.8%. With its rapid analysis and simple pretreatment steps,the method is expected to have a strong advantage in the rapid screening analysis of large quantities of beverage and urine.
ABSTRACT
<p><b>OBJECTIVE</b>To determine ten B-vitamins in human milk by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS).</p><p><b>METHODS</b>The pretreated human milk samples were adequately separated and quantified within 11 min by UPLC-MS/MS with an Acquity UPLC HSS T3 column (2.1×100 mm, 1.8 µm). The mobile phase was a gradient of 2.5 mmol/L ammonium formate aqueous solution and acetonitrile at a flow rate of 0.35 mL/min. Stable isotope internal standards were used in the analysis, to correct for the method variability, including matrix and ionization effects. The homogenized human milk samples were deproteinzed using methanol, unknown contaminants were extracted with diethyl ether and hydrophobic phase was discarded. The analytes were monitored via ESI+ionization and detected in multiple reaction monitoring (MRM) with three acquisition functions.</p><p><b>RESULTS</b>Calibration curves ranged from 0.5-160 ng/mL (thiamin, riboflavin, biotin, nicotinic acid, pyridoxine, pyridoxamine, pyridoxal), and 2.5-800 ng/mL (pantothenic acid, FAD and nicotinamide) (R2=0.990-0.999). The relative recovery ranged from 80.1% to 120.2%; accuracy was determined to be 98.3% to 108.0%. Intra-day and inter-day variation were 3.4%-19.9% and 5.9%-18.1%, respectively. The limit of quantification (LOQ) for all vitamins was between 0.25 and 3 µg/L.</p><p><b>CONCLUSION</b>This method was successfully applied for simultaneous analysis of ten B-vitamins in human milk.</p>