Simultaneous determination of diquat and its two primary metabolites in rat plasma by ultraperformance liquid chromatography-tandem mass spectrometry and its application to the toxicokinetic study

PURPOSE

This study aimed to develop and validate an ultraperformance liquid chromatography-tandem mass spectrometry to simultaneously determine diquat (DQ) and its two primary metabolites in rat plasma and its application to the toxicokinetic study.

METHOD

The chromatographic separation of DQ and its two primary metabolites was performed with hydrophilic interaction chromatography column by adding formic acid and ammonium acetate in mobile phase in stepwise elution mode. DQ and its two primary metabolites were detected by liquid chromatography-tandem mass spectrometry in positive mode.

RESULTS

The lower limit of quantification ranging from 0.3 to 3.0 ng/mL for DQ and its two primary metabolites was achieved by using only 50 μL of rat plasma. The maximum concentration (C_max) was 977 ng/mL, half-life (t_1/2) was 13.1 h, and area under the plasma concentration-time curve (AUC_0-t) was 2770 h*ng/mL for DQ, C_max was 47.1 ng/mL, t_1/2 was 25.1 h, and AUC_0-t was 180 h·ng/mL for diquat monopyridone (DQ-M) and C_max was 246 ng/mL, t_1/2 was 8.2 h, and AUC_0-t was 2430 h·ng/mL for diquat dipyridone (DQ-D), respectively.

CONCLUSIONS

The validated method was shown to be suitable for simultaneous determination of diquat and its two primary metabolites in rat plasma. This study is the first to study the toxicokinetics of DQ and its two primary metabolites.

Simultaneous Quantification of 3'- and 6'-Sialyllactose in Rat Plasma Using Liquid Chromatography-Tandem Mass Spectrometry and Its Application to a Pharmacokinetic Study

Sialyllactose (SL), an acidic oligosaccharide, has immune-protective effects against pathogens and helps with the development of the immune system and intestinal microorganisms. To elucidate the pharmacokinetic characterization after oral administration to rats, the simultaneous quantification method for 3'-SL and 6'-SL in rat plasma was validated, using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in an electrospray ionization (ESI) mode. Several types of columns [C18, amide, and hydrophilic interaction liquid chromatography (HILIC) phase] were used to separate the peaks of 3'-SL and 6'-SL, which improved chromatographic selectivity. Ultimately, the HILIC phase column had a good peak shape and quick resolution, with a mobile phase comprising ammonium acetate buffer and acetonitrile obtained by gradient elution. In addition, the simultaneous quantification of 3'-SL and 6'-SL in rat plasma samples were adequately applied to pharmacokinetic study.

Development and validation of a bioanalytical method of analyzing 3'- and 6'-sialyllactose using liquid chromatography-tandem mass spectrometry in minipig plasma and its application in a pharmacokinetic study

Sialyllactose (SL) is an acidic oligosaccharide, consisting of a combination of sialic acid and lactose. It is found in human milk. It has immune-protective effects against pathogens in newborns and helps with the development of the immune system and intestinal microorganisms. We developed and validated a method by which 3'-SL and 6'-SL levels were simultaneously analyzed via liquid chromatography-tandem mass spectrometry (LC-MS/MS), and evaluated the pharmacokinetics of the materials after systemic delivery to minipigs. To improve chromatographic selectivity, several types of columns (C18, amide, and HILIC phase) were used to separate the peaks of 3'-SL and 6'-SL. Ultimately the HILIC phase column was selected, as it had a good peak shape and quick resolution. The mobile phase comprised ammonium acetate buffer and acetonitrile with gradient elution. MS was performed in the negative ion and multiple reaction monitoring modes. Plasma samples were prepared using the protein precipitation method with methanol. A surrogate matrix was used for quantification because SLs are endogenous plasma compounds. The method developed was validated according to U.S. Food and Drug Administration guidance. A pharmacokinetic study was performed with intravenous administration of 3'-SL and 6'-SL in minipigs (Sus scrofa/Yucatan). The concentrations of 3'-SL and 6'-SL were readily measurable in the plasma samples, which suggests that the method adequately determined systemic exposure in minipigs.

An Improved HILIC HPLC-MS/MS Method for the Determination of β-ODAP and Its α Isomer in Lathyrus sativus

β-N-Oxalyl-l-α,β-diaminopropionic acid (β-ODAP) is a non-protein amino acid present in Lathyrus sativus (grass pea) and other Lathyrus species, in parallel with its nontoxic isomer, α-ODAP. When consuming grass pea for several months as staple food, β-ODAP may cause neurolathyrism, a motor neuron degeneration syndrome. Therefore, the independent quantification of both ODAP isomers instead of only the total amount in grass pea allows the identification of less toxic varieties and the development of tools to support breeding for improving grass pea quality. In this work, a simple and fast HPLC-MS/MS method was developed without sample derivatization, using a hydrophilic interaction chromatography (HILIC) column and an isocratic gradient of eluents for 18 min, which allowed the determination of both α- and β-ODAP. The proposed method was fully validated and applied to the determination of α- and β-ODAP contents in a diverse collection of 107 grass pea accessions representative of the main grass pea-growing geographical regions in the world, with the prompt identification of contrasting accessions. β-ODAP content in the analyzed grass pea samples ranged from 0.45 ± 0.02 to 6.04 ± 0.45 mg g⁻¹. The moderate correlation found between α- and β-ODAP contents (0.65) in this collection reinforces the importance of the independent quantification of both ODAP isomers.

Analysis of alkaloids from Peganum harmala L. sequential extracts by liquid chromatography coupled to ion mobility spectrometry

An orthogonal two dimensional analysis method based on high performance liquid chromatography (HPLC) separation and electrospray ionization-ion mobility spectrometry (ESI-IMS) detection was developed for the analysis of alkaloid compounds from Peganum harmala L. seeds. Reverse phase (RP) and hydrophilic interaction chromatography (HILIC) were compared for the most optimal performance using three different chromatographic columns. The experimental results suggest that HILIC mode is a better option for combining with the ESI-IMS system for higher sensitivity and ease in hyphenating. Under optimized conditions, alkaloids from different extraction phases were determined by means of the established HPLC-IMS method. More compounds from Peganum harmala L. seed extracts were differentiated on the HPLC-ESI-IMS system by their retention time and drift time than by HPLC or ESI-IMS alone, and thirteen alkaloids were tentatively identified based on m/z and fragment ions using ultra-high-performance liquid chromatography tandem mass-spectrometry (UPLC-MS/MS). Hence, our results indicate that this method can be considered to be advantageous over traditional absorbance detection methods for resolving complex mixtures because of complementary separation steps, elevated peak capacity, and higher sensitivity.

Optimized ultra performance liquid chromatography tandem high resolution mass spectrometry method for the quantification of paraquat in plasma and urine

A simple, sensitive and specific ultra performance liquid chromatography coupled to electrospray tandem high resolution mass spectrometry (UPLC-ESI-HRMS/MS) method has been developed and validated for quantification of paraquat in plasma and urine. The sample preparation was carried out by one-step protein precipitation with acetonitrile. The paraquat was separated with a HILIC column in 10min. Detection was performed using Q Exactive Orbitrap mass spectrometer by Targeted-MS/MS scan mode. Methodological parameters, such as ammonium formate concentration, formic acid concentration, spray voltage, capillary temperature, heater temperature and normalized collision energy were optimized to achieve the highest sensitivity. The calibration curve was linear over the concentration range of LOQ-1000ng/mL. LOD was 0.1 and 0.3ng/mL, LOQ was 0.3 and 0.8ng/mL for urine and plasma, respectively. The intra- and inter-day precisions were <7.97% and 4.78% for plasma and urine. The accuracies were within the range 93.51-100.90%. The plasma and urine matrices had negligible relative matrix effect in this study. This method was successfully applied to determine paraquat concentration in plasma samples with hemoperfusion from 5 suspected paraquat poisoning patients.