Analytical Chemistry Research最新文献

This paper reports the development and optimization of micro-matrix solid-phase dispersion (micro-MSPD) of nine polychlorinated biphenyls (PCBs) in mussel samples (Mytilus galloprovincialis) by using a two-level factorial design. Four variables (amount of sample, anhydrous sodium sulphate, Florisil and solvent volume) were considered as factors in the optimization process. The results suggested that only the interaction between the amount of anhydrous sodium sulphate and the solvent volume was statistically significant for the overall recovery of a trichlorinated compound, CB 28. Generally most of the considered species exhibited a similar behaviour, the sample and Florisil amounts had a positive effect on PCBs extractions and solvent volume and sulphate amount had a negative effect. The analytical determination and confirmation of PCBs were carried out by using GC-ECD and GC-MS/MS, respectively. The method was validated having satisfactory precision and accuracy with RSD values below 6% and recoveries between 81 and 116% for all congeners. The optimized method was applied to the extraction of real mussel samples from two Galician Rías.

Trace amounts of Cr, Zn, Cd, and Pb were determined by metal furnace atomic absorption spectrometry using absorption tubes. Various absorption tubes were designed as roof- and tube-types, and fixed above the metal furnace in order to extend the light path length. Aqueous standards and samples were injected in the metal furnace and atomized in a metal atomizer with an absorption tube (6 cm length, 15.5 mm diameter). The used of an absorption tube resulted in an enhancement of the atomic absorbance. The ratios of absorbance values with and without the roof- and tube-type absorption tubes were 1.33 and 1.11 for Cr; 1.42 and 1.99 for Zn; 1.66 and 1.98 for Cd; and 1.31 and 1.16 for Pb, respectively. The use of an absorption tube was effective for Zn and Cd analysis, as the absorbance values for these low boiling point metals doubled. The proposed method was successfully applied in the determination of Zn in tap water.

An efficient and fast method based on isopropyl 2-[(isopropoxycarbothiolyl)disulfanyl] ethane thioate (IICDET) were used for the speciation and determination of trace amount of Cr(III and VI) in human biological samples by cloud point assisted dispersive ionic liquid –liquid microextraction (CP-DILLME). Cr(VI) has carcinogenic effects, so, speciation of chromium in human body such as blood cells is very important. The cloudy solution was achieved by the mixture of acetone and IL ([C₈MIM][PF₆]) in human blood samples containing Cr(III) ions that were already complexed by IICDET at pH 4.5. After reduction Cr(VI) to Cr(III) by ascorbic acid, chromium speciation was obtained based on total chromium determination by electro thermal atomic absorption spectrometry (ET-AAS) and difference between total Cr and Cr(III) content. In addition, Cr speciation in human blood cells was calculated based on IICDET/CP-DILLME and hematocrit blood test (HCT). After optimized conditions, the enrichment factor (EF), Linear range and limit of detection (LOD) was obtained 25.2, 0.02–1.75 μg L⁻¹ and 5.4 ng L⁻¹ in human biological samples respectively. The validation of methodology was achieved by certified reference material (CRM) and ICP-MS technique.

Liquid-based miniaturized techniques have received a lot of attention recently resulting in the development of the liquid phase microextraction (LPME) and dispersive liquid-liquid microextraction (DLLME) techniques each offering unique benefits over the other technique. Herein we report a combination of the two techniques for the extraction of hexestrol and atrazine from aqueous systems. The method sets off with the DLLME thereafter a hollow fibre filled with the organic solvent is introduced for the extraction of the pre-extracted analytes in the dispersed organic solvent. The method was modified further by introducing a second extracting solvent in place of the disperser solvent. Under the optimum conditions, namely, toluene in the acceptor phase, 1:1 chloroform:toluene (v/v) as a dispersed solvent, 15% NaCl, with the 15 min extraction time, the method achieved satisfactory enrichment factors (87- and 62-fold); sufficiently low detection limits of 0.018 μg/mL and 0.016 μg/mL using the flame ionization detector, while 0.072 and 0.063 ng/mL were obtained using single ion monitoring mass spectrometry detector, for atrazine and hexestrol, respectively; with sufficient linearity (R² ≥ 0.9959). Although the compounds were not detected in the river water sample, satisfactory recoveries (111–115%) were achieved indicating the method did not suffer any negative matrix effect.

The product of the NH₃- o-phthalaldehyde (OPA) -Na₂SO₃ reaction is rose red at pH more than 10.4, and its maximum absorption wavelength is 550 nm. Based on this, a novel spectrophotometric method with flow injection analysis has been established to determine ammonia nitrogen in water. Experimental parameters related to the flow injection method and the reaction were optimized throughout the experiments based on univariate experimental design. The length of coil is optimized as 1.6 m for storing up standard or sample solution. The optimal value is 8.20 mL/min for loading flow rate of coloring solution. The OPA concentration, sulfite concentration and reaction pH are chosen as 1.06 g/L, 0.050 g/L and 10.80, respectively. The reaction temperature and stop flow time affects the performances of the method. The linearity range and detection limit of the proposed method are 0.100–0.700 mmol/L and 0.007 mmol/L at the reaction temperature of 55 °C and stop flow time of 340 s, respectively. The sample throughput is more than 8 h⁻¹. Under the optimal experimental conditions, the recovery is 100.4%, 95.2%, 101.7% and 92.4% for the lake water, river water, groundwater and sewage, respectively. Two lake water samples were analyzed using both the proposed method and indophenol blue method, the results show no significant difference between these two methods. In comparison with other spectrophotometric determination method of ammonia nitrogen, the main merits of the proposed method are simplicity, reliability, reproducibility and high sample throughput.

A rapid and simple method for the separation and determination of five polycyclic aromatic hydrocarbons (PAHs) in water is described. The procedure is based on the selective extraction of the PAHs on the surface of modified magnetic nanoparticles using a solid-phase dispersion technique. The PAHs-loaded magnetic nanoparticles were separated from the aqueous phase with a magnet and then quantified by HPLC. The modified extraction method successfully replaced conventional extraction methods. The partitioning of the analyte between the sub-micron magnetic nanoparticles (solid phase) and the liquid phase occurs as the solid moves through the samples as a colloidal sol. The detection limits were in the range 0.14–0.31 ng/L, with recoveries ranging from 88% to 96%. The as-synthesized magnetic nanoparticles showed good stability and high extraction recoveries for the adsorption-desorption of PAHs, even after recycling four times. The procedure was successfully applied to PAHs determinations in real water samples.

Ethylene glycol monobutyl ether (EGBE), also known as 2-butoxyethanol (2-BE), has been identified as a contaminant in hydraulic fracturing fluids. In order to determine the presence of 2-BE in hydraulic fracturing chemical additives, a reliable method for recovering 2-BE from aqueous phases by liquid-liquid extraction combined with gas chromatography/mass spectrometry (GC/MS) was established. The liquid-liquid extraction method was applied to samples matrices containing various amounts of salt. Using methylene chloride for liquid-liquid extraction in a sample to solvent ratio of 1:3, ≥99% 2-BE recovery may be achieved with less than 5% standard error. The limit of detection was determined to be 0.957 mg L⁻¹ 2-BE. Accuracy was determined to be 2.58% and precision was determined using the coefficient of variation, which was 3.5%. The method was used to recover 2-BE in a hydraulic fracturing chemical additive called Revert Flow and to quantify the weight percent of 2-BE in the chemical additive. Weight percent of two additional components of Revert Flow, D-limonene and 1-butoxy-2-propanol, were also determined. We also used the method to determine the abiotic of 2-BE in water, which was 5.55 days. The persistence of 2-BE in hydraulic fracturing fluid was also investigated and determined that 2-BE is more persistent in this environment.

A sensitive, specific and fast method to quantify 3α-hydroxytibolone in human plasma using deuterated 3α-hydroxytibolone (d5) as internal standard is described. The analyte and the internal standard were extracted from plasma (900 μL) by liquid-liquid extraction using ethyl ether/hexane (50/50, v/v) and ammonium hydroxide (50%). The extracts were analyzed by high performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry without derivatization. Chromatography was performed isocratically on a Gemini-NX™ C₁₈ 5 μm (150 × 4.6 mm i. d.) column. The method had a chromatographic run time of 3.75 min and a linear calibration curve over the range 1–100 ng/mL. The limit of quantification validated was 1 ng/mL. This method was used to assess the bioequivalence between two different tibolone oral formulations: Livolon (1.25 mg tablet) provided by Biolab Sanus Farmacêutica (Brazil), as the test formulation, and Libiam™ (1.25 mg tablet) produced by Libbs Farmacêutica (Brazil), as the reference formulation. A single 3.75 mg dose of each formulation was administered to 46 postmenopausal female healthy volunteers. The study was conducted in an open, randomized, two-period crossover balanced design with a 2 week washout interval between the doses. The 90% confidence interval for C_max, AUC_(0-last) and AUC_(0-inf) individual test/reference ratios were 97.48–111.51, 95.35–103.20 and 96.42–103.86, respectively. It is concluded that Livolon (1.25 mg tablet) is bioequivalent to Libiam™ (1.25 mg tablet), with regards to both rate and extent of absorption.

A naphthalo-1, 8-bis[(2,4-dinitrophenyl)hydrazone] sensor (K) was synthesized and characterized using UV–vis, ¹H NMR and fluorescence spectroscopy. The sensor showed strong colorimetric and spectral response upon the molar addition of acetate or fluoride ion (AcO⁻ or F⁻) in acetonitrile. The complexed state (KF or KAcO) of the system showed significant reversibility properties, both in color and spectra, upon the addition of small traces of water. Subsequently, in addition to sensing of fluoride or acetate ions, the complexed KF or KAcO adducts can be used in colorimetric signaling of water traces in different organic mediums. In order to have more understanding of the interaction between K and the anions, the study was supplemented using density functional theory computations.