A facile and efficient electrochemical sensing platform has been successfully exploited for the first time for the determination of lactic acid using a nickel oxide (NiO) nanoparticle-modified glassy carbon electrode (GCE). Nickel oxide nanoparticles were prepared by a chemical growth method using different quantities of arginine as a soft template. The structural and morphological properties of NiO nanoparticles were characterized by Raman spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Cyclic voltammetry (CV) was used to study the electrochemical properties of various samples. The modified electrode is highly sensitive and presents a linear response over a wide range (0.005–5 mM) of lactic acid concentrations in 0.1 M NaOH. The detection limit for the sensor was found to be 5.7 μM, and it exhibits good stability. Furthermore, the sensor shows excellent selectivity in the presence of common interfering species. The lactic acid sensor showed good viability for lactic acid analysis in real samples (milk, yogurt and red wine) and demonstrated significant advancement in sensor technology for practical applications.
A new method has been developed for precise vanadium isotope ratio measurements by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) in Amanita muscaria - a widespread toxic and hallucinogenic mushroom which is also known for its ability to bio-accumulate vanadium. Prior to isotope ratio measurements vanadium was separated from the sample matrix by anion-exchange chromatography with a single run of a sample solution through the anion-exchange column sufficient for the purification of vanadium. V-51/V-50 isotope ratio measurements were carried out in the high resolution mode of MC-ICPMS which allowed the separation of V-50(+) and V-51(+) ions from polyatomic interfering species, including sulphur-based ions. Iron was employed as an admixed internal standard and was found effective in correcting for the drift of instrumental mass bias. An important feature of the method was the use of a regression model in data reduction. The Plackett-Burman factorial design was used for ruggedness testing and showed that normalisation to the Fe-56/Fe-54 isotope ratio of the internal standard significantly improved the repeatability of the results. The combined standard uncertainties of delta V-51 values determined for samples of the mushroom ranged from 0.28 parts per thousand to 0.42 parts per thousand. delta V-51 values for the samples collected in geographically different locations varied from -0.7 parts per thousand to 1.7 parts per thousand, suggesting V-51/V-50 isotope ratio measurements as a useful tool for identifying the origin of Amanita muscaria in tasks concerned with counteracting the abuse of hallucinogenic mushrooms and in studies on the biochemistry of vanadium.
A new method was developed for precise and accurate Mo isotope ratio measurements in plant materials by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS). It is based on the use of anion-exchange chromatography to isolate Mo from concomitant matrix elements in sample digests, a desolvating Apex-Q sample inlet system as a means of Mo signal enhancement and on-line normalisation to an admixed internal standard (Pd) to correct for instrumental mass bias. Mo isotope ratios were determined in sample solutions with Mo concentrations as low as 10 ng g-1. The developed method was successfully applied to the determination of natural variations in the isotopic composition of Mo in different anatomical parts of plants. We show for the first time that Mo isotope fractionation can occur during long-distance transport of Mo in plants. Our data also show that the magnitude of Mo isotope fractionation during translocation of Mo is different for different plant species. Mo isotope ratio data obtained by MC-ICPMS can therefore be used as a sensitive probe of processes controlling transport and distribution of molybdenum in plants.