Determination of fipronil and its metabolites in chicken egg by dispersive liquid–liquid microextraction with 19F quantitative nuclear magnetic resonance spectroscopy

A simple and efficient derivatization strategy combined with switchable solvent liquid-liquid microextraction hydroxychloroquine methyl acetate-d3 -based quadruple isotope dilution gas chromatography mass spectrometry for the determination of hydroxychloroquine sulfate in biological fluids

RATIONALE

A derivatization switchable solvent liquid-liquid microextraction quadruple isotope dilution gas chromatography mass spectrometry (D-SS-LLME-ID⁴ -GC/MS) method is presented for the determination of hydroxychloroquine sulfate in human biofluids.

METHODS

While mixing type/period and concentration of NaOH were optimized via a univariate optimization approach, a multivariate optimization approach was used to determine optimum values for relatively more important parameters such as volumes of derivatization agent (acetic anhydride), NaOH and switchable solvent.

RESULTS

Under the optimum experimental conditions, limit of detection and limit of quantification were calculated as 0.03 and 0.09 mg/kg (mass based), respectively. An isotopically labelled material (hydroxychloroquine methyl acetate-d₃ ) was firstly synthesized to be used in ID⁴ experiments which give highly accurate and precise recovery results. After the application of D-SS-LLME-ID⁴ , superior percent recovery results were recorded as 99.9 ± 1.6-101.3 ± 1.2 for human serum, 99.9 ± 1.7-99.8 ± 1.8 for urine and 99.6 ± 1.5-101.0 ± 1.1 for saliva samples.

CONCLUSIONS

The developed D-SS-LLME-ID⁴ -GC/MS method compensates the complicated matrix effects of human biofluids and provides highly accurate quantification of an analyte with precise results.

Research Progress of NMR in Natural Product Quantification

In the fields of medicine and health, traditional high-performance liquid chromatography or UV-visible spectrophotometry is generally used for substance quantification. However, over time, nuclear magnetic resonance spectroscopy (NMR) has gradually become more mature. Nuclear magnetic resonance spectroscopy has certain advantages in the quantitative analysis of substances, such as being nondestructive, having a high flux and short analysis time. Nuclear magnetic resonance spectroscopy has been included in the pharmacopoeiae of various countries. In this paper, the principle of nuclear magnetic resonance spectroscopy and the recent progress in the quantitative study of natural products by NMR are reviewed, and its application in the quantitative study of natural products is proposed. At the same time, the problems of using NMR alone to quantify natural products are summarized and corresponding suggestions are put forward.