Determination of pyridoxal in human serum by matrix isopotential synchronous fluorescence spectrometry

Unveiling angular sweep total fluorescence Spectroscopy:A novel multidimensional technique for analysis of complex multi-fluorophoric systems

Analyzing multi-fluorophoric real systems without pre-processing is challenging, often addressed with unconventional fluorescence techniques and chemometrics. In this context, we introduce a novel addition - 'Angular Sweep Total Fluorescence Spectroscopy (ASTFS),' to the arsenal of multidimensional steady-state fluorescence spectroscopic techniques. ASTFS utilizes a series of variable angle synchronous fluorescence spectra, strategically covering the fluorescence region between the first and second-order Rayleigh scattering ridges. The plot features a minimal data matrix size, avoids Rayleigh scattering signals, and incurs no blind regions. The study delves into the instrumental configurations for spectral acquisition, highlights the enhanced spectral resolution due to the band-narrowing effect, and discusses other notable features of the ASTFS plot. Further, this technique is reported to be effective in analyzing analytes in complex systems with strong background fluorescence, such as milk. The antibiotic- Norfloxacin is quantified via minimal pre-processing in milk samples and yields excellent analytical figures of merit.

Determination of copper (II) in foodstuffs based on its quenching effect on the fluorescence of N,N'-bis(pyridoxal phosphate)-o-phenylenediamine

A Schiff base-type fluorescence probe was prepared for the detection of copper (II) in foodstuffs. The probe is N,N'-bis(pyridoxal phosphate)-o-phenylenediamine (BPPP). It was synthesized by utilizing the Schiff base condensation reaction of pyridoxal 5-phosphate with 1,2-phenylenediamine. BPPP has the properties of high fluorescence stability, good water solubility and low toxicity. Its maximum excitation wavelength and maximum fluorescence emission wavelength are at 389 and 448 nm, respectively. When BPPP coexists with copper (II), its fluorescence is dramatically quenched. Under a certain condition, the fluorescence intensity decreased proportionally to the concentration of copper (II) by the quenching effect. Based on this fact, we established a fluorescence quenching method for the determination of copper (II). Under optimal conditions a linear range was found to be 0.5-50 ng/mL with a detection limit of 0.2 ng/mL. The method has been applied to determine copper (II) in foodstuff samples and the analytical results show good agreement with that obtained from atomic absorption spectrometry method.

Application of the high-performance liquid chromatography method with coulometric detection for determination of vitamin B(6) in human plasma and serum

A reversed-phase high-performance liquid chromatography method (HPLC) with coulometric electrochemical detection has been developed and validated for the simultaneous analysis of pyridoxamine-5'-phosphate (PMP), pyridoxamine (PM), pyridoxal 5'-phosphate (PLP), pyridoxal (PL), pyridoxine (PN) and 4-pyridoxic acid (4-PA) in human plasma and serum. The isocratic separation was achieved on C(18) column (250mmx4.6mm, I.D., 5microm) with a mobile phase consisted of 35mM sodium phosphate containing 2.5mM heptanesulfonic acid, adjusted to pH 3.2 with 85% orthophosphoric acid and 12% methanol (v/v). Within-run and between-run precisions expressed by the relative standard deviations were less than 2.7% and 7.7% for all the analysed vitamins and 4-PA, respectively. The limits of detection (LOD) and quantification (LOQ) were: 0.8 and 2.6nM, 1.1 and 3.8nM, 1.5 and 4.5nM, 1.3 and 4.2nM, 1.1 and 3.7nM, 2.1 and 6.3nM for PMP, PM, PLP, PL, PN and 4-PA, respectively. The recoveries ranged from 90.4% to 98.4%. Stability of vitamins was checked under a variety of storage conditions. The developed application demonstrated acceptable sensitivity, precision, accuracy, stability, and linearity over the physiological concentration range. The major advantage of the proposed method is its great simplicity.

Simultaneous Fluorometric Resolution of Pyridoxal, Pyridoxamine and 4-Pyridoxic Acid Using Chemometric Methods

An alternatively minimizing covariant matrix error (AMCME) algorithm, newly proposed by the present authors, was applied to the simultaneous fluorometric determination of pyridoxal, pyridoxamine and 4-pyridoxic acid without loss of sensitivity. The experimental results illustrate that the profiles of spectra and concentration can be accurately resolved using the AMCME algorithm with a high sensitivity and stable repeatability. That is to say, the closely overlapping problem of the spectra could be resolved owing to the characteristic features of the AMCME algorithm.