基于金属有机骨架复合气凝胶的分散固相萃取-超高效液相色谱-串联质谱法测定水中5种非甾体类抗炎药

非甾体类抗炎药(NSAIDs)能在环境水体中长期稳定存在,不仅对生物有慢性毒性还能增加病原体的耐药性,开发可靠的测定水样中痕量非甾体抗炎药的分析方法至关重要.该文制备新型金属有机骨架/壳聚糖复合气凝胶材料Co-UiO-67(bpy)/CS分散固相萃取吸附剂,将其用于环境水体中酮洛芬、萘普生、氟比洛芬、双氯芬酸、布洛芬5...     

Classical Food Quality Attributes and the Metabolic Profile of Cambuci,a Native Brazilian Atlantic Rainforest Fruit

The cambuci is a native Brazilian fruit from the Atlantic Forest biome. A soft and astringent pulp, a green color, and a sweet aroma are its main characteristics. Classical food quality attributes (fresh fruit mass, fruit height, diameters, total soluble solid, titratable acidity, and ratio) and the metabolic profile from ten accessions from three different locations were analyzed herein by analytical methods (refractometry and neutralization titration) and nuclear magnetic resonance spectroscopy. Concerning sugar content, sucrose was the predominant compound, with glucose and fructose alternating in second, depending on the accession. Citric acid was the most relevant acid, followed by shikimic and quinic acids in quite variable amounts. These three main acids vary in amounts for each accession. Ascorbic acid content emerges as an important quality attribute and makes this fruit nutritionally attractive, due to values comparable to those contained in citric fruits. The main amino acids identified in cambuci were glutamic acid individually or in comprising the tripeptide glutathione (glutamic acid, cysteine, glycine). The quality diversity of the evaluated accessions suggests the potentiality of cambuci use in future breeding programs.     

Selective determination of trace arsenic and antimony species in natural waters by gas chromatography with a photoionization detector

Traces amounts of arsenic and antimony in water samples were determined by gas chromatography with a photoionization detector after liquidnitrogen cold trapping of their hydrides. The sample solution was treated with sodium hydroborate (NaBH₄) under weak-acid conditions for arsenic(III) and antimony(III) determination, and under strong-acid conditions for arsenic(III+V) and antimony(III+V) determination. Large amounts of carbon dioxide (CO₂) and water vapor obscured determination of arsine and stibine. Better separation from interference could be achieved by removing CO₂ and water vapor in two tubes containing sodium hydroxide pellets and calcium chloride, respectively. The detection limits of this method were 1.8 ng dm^?3 for arsenic and 9.4 ng dm^?3 for antimony in the case of 100-cm³ sample volumes. Therefore, it is suitable for determination of trace arsenic and antimony in natural waters.     

Comparison of microbial activity in some Brazilian soils by microcalorimetric and respirometric methods

The microbial activity in a Rhodic eutrudox (R), a Typic eutrudox (V) and a Quartzipsamment (Q) was monitored by respirometric and calorimetric methods. CO₂ evolution was monitored for 98 days by titrimetry and conductimetry for control amended samples (A) with 25% of cattle manure (E), municipal refuse compost (L), earthworm casts (H) or 1.25 kg ha⁻¹ of trifluralin (T). Average values of all treatments through respiration at the end of the incubation period were 5.24±0.34, 6.13±0.31 and 6.50±0.33, in mg CO₂ g⁻¹ soil, for R, V and Q, respectively, by titrimetry and 8.89±0.44, 10.41±0.54 and 10.41±0.52, in mg CO₂ g⁻¹ soil, for R, V and Q, respectively, for conductimetry. Excellent correlation (r=1.00) between titrimetry and conductimetry was observed. The decreasing order for respiration was E, H, L and T. After each incubation time, the conductimetric values were higher than those for titrimetry, for all treatments of these Brazilian soils. Average values of the exothermic thermal effect were: 0.58±0.02, 0.60±0.02 and 0.67±0.01 kJ g⁻¹ soil, for R, V and Q, respectively, for 103 days. A significant correlation coefficient of 0.91 and P<0.0001 between calorimetric and respirometric values over 98 days was observed. Based on the obtained calorimetric results, it can be proposed that this technique should be as a useful analytical method for determining the microbial activity in soils.     

Spectrofluorimetric determination of carbaryl and 1-naphthol in micellar media

The interaction of 1-naphthol-N-methyl-carbamate (carbaryl) and its degradation product, 1-naphthol, with the surfactant hexadecyl-trimethylammonium bromide has been studied. The micellar medium allows the direct spectrofluorimetric determination of carbaryl, with 6.2 ng/ml as detection limit in acidic medium, or indirectly, after hydrolysis, as 1-naphthol at pH 11.0 or pH 3.0 with detection limits of 0.4 and 1.6 ng/ml, respectively. The recoveries of carbaryl and 1-naphthol from natural waters are acceptable.     

Determination of tungsten with pyrocatechol violet by first-derivative solid-phase spectrophotometry

Derivative spectrophotometry was applied to solid-phase spectrophotometry in order to enhance its sensitivity and remove the large background caused by the absorbance of the resin layer. Determination of micro-amounts of tungsten with pyrocatechol violet to form a 21 green complex in acid medium which is fixed on a dextran-type anion-exchange resin (Sephadex QAEA-25) is described as an example for the application of this technique. The absorbance of the resin packed in a 1-mm spectrophotometric cell, was measured directly. The characteristic peak amplitude of the signal at 674 nm in the first-derivative spectrum is useful for quantitative determination of tungsten (3–16 g 1^–1; RSD 5.8%) in natural and industrial water samples.     

Evaluation of Cu–Ethylenediamine Metal Ion Buffers as Calibrants for Ion‐Selective Electrode Measurement of Copper in Fresh Water Systems

An investigation was made into the accuracy of cupric ion selective electrode (ISE) measurement of Cu in solutions approximating acidic freshwaters with Cu‐ethylenediamine buffers used as the calibrants. This method overestimates the free Cu compared with calibration using Cu(NO₃)₂ standards, the standard addition method, and speciation modelling calculations. Statistical tests showed a small, but significant, difference between the intercepts of the linear Nernstian regressions of the calibration plots of Cu‐en buffer standardisation and direct calibration with Cu(NO₃)₂ standards in matrix that matches the samples. The difference in the intercepts, which corresponds with E_o values of the electrode, is not well understood, but is possibly caused by potentially interfering cations such as Fe²⁺. The results of this study showed that down to 10^?8 M Cu²⁺, where a linear Nernstian response is possible, the Cu ISE is probably better calibrated using Cu standards prepared in the same matrix as the sample solutions to avoid potential matrix effects.     

The selection of a chemical modifier for vanadium determination in various types of natural waters by electrothermal atomic absorption spectrometry

Various modifiers (ascorbic acid, NH₄NO₃, EDTA, NH₄SCN and a mixture of Pd/Mg(NO₃)₂) are compared for the accurate determination of vanadium in natural waters by electrothermal atomic absorption spectrometry. The interferences of compounds commonly present in natural waters, such as NaCl, CaCl₂, MgCl₂ and FeCl₃ are studied. Matrix interferences were effectively eliminated by ascorbic acid or ammonium nitrate. For comparison, the standard addition method was applied without a modifier which provided satisfactory results. The accuracy of the method was confirmed by analysis of certified reference materials of waters (‘Trace Metals in Drinking Water’ and SRM 1643e ‘Trace Elements in Water’) as well as by recoveries of vanadium spiked to tap water, mineral water, synthetic riverine and synthetic sea waters. The limits of detection and characteristic masses for ascorbic acid and ammonium nitrate as the modifiers were 1.71 and 1.56?µg?L^?1 and 70 and 67?pg, respectively. Recovery was in the range of 98–105% and RSD was less than 5%.     

Determination of Some Metal Ions in Aquatic Environs by Atomic Absorption Spectrometry after Concentration with Modified Silica

The uptake behavior of porous silica modified with N‐propylsalicylaldimine (IE11) for Cd(II), Cr(III), Cu(II), Mn(II) and Pb(II) metal ions were studied. The Log k_d values were found to be within the range 2.19–5.16 depending on pH and time of stirring. IE11 was used in the separation and preconcentration of Cd(II), Cr(III), Cu(II), Mn(II) and Pb(II) from some natural water samples. The data were compared with those obtained by the solvent extraction method (APDC/MIBK). The method was found to be accurate and precise and not subject to random error.     

Determination of ammonium using a microplate-based fluorometric technique

The determination of ammonium (NH₄⁺) in concentrations ranging from nanomolar to micromolar in fresh and brackish waters often loaded in high suspended particulate matter and dissolved organic acids is presented. The newly described microplate-based fluorometric technique is allowing quick automated readings of different groups of samples with different background fluorescence and matrix effects. The lowest detectable concentration was estimated to 5 nM using the average detected blank ±3S.D. and the practical detection limit (LOD) determined with successive calibration curves was 50 nM with an excellent repeatability. High loading of suspended particular matter, coloured organic acids, and salinity changes were not interfering with the accurate determination of ammonium. To illustrate its robustness and efficiency, this technique has been applied to water samples taken from rivers, saltmarshes and estuaries, spanning a large range of ammonium levels and chemical properties. Measurements of ammonium on reddish turbid waters sampled in south shore of St. Lawrence Estuary showed ammonium concentrations between 0.05 ± 0.01 and 3.89 ± 0.03 μM, indicating a significant source of ammonium from terrestrial and saltmarsh ecosystems.