Quantitative quadrupolar NMR (qQNMR) determination of taurine in undiluted human urine samples using 1D and 2D 33S NMR

A quantitative quadrupolar nuclear magnetic resonance (qQNMR) method based on sulfur-33 (³³S) NMR has been developed for the direct, dilution-free determination of taurine in human urine, addressing matrix challenges in biofluid analysis. The 1D³³S approach exhibited linearity (14-70 mg mL^-1; R² = 0.9993), LOD = 6.78 ± 0.66 mg mL^-1, LOQ = 10.84 ± 0.69 mg mL^-1, precision <1.1 % CV, and recoveries of 96.95-101.58 % with negligible matrix effect (-3.15 %). External calibration using ammonium sulfate yielded similar results. Critically, 2D ¹H-³³S gHMBC experiments reduced LOD/LOQ to 1.2/4.0 mg mL^-1 by leveraging ¹H sensitivity. The method enables rapid (<12 min), robust analysis without sample pretreatment, offering a practical alternative to chromatographic techniques for high-concentration urinary taurine quantification.