Analytical Chemistry Research最新文献

Flutamide (2-methyl-N-[4-nitro-3-(trifluoromethyl)phenyl]-propanamide) is a non-steroidal drug that has a specific anti-androgenic activity so that it is used in the treatment of prostate cancer. A simple method for extraction and detection of flutamide from pharmaceutical forms are reported using Soxhlet apparatus combined electrospray ionization tandem mass spectrometry (ESI(−)-MSⁿ, n = 1−4) in negative ion mode. Spectra show a fingerprint peaks corresponding to flutamide. Propanamide moiety plays important role in structure elucidation. The diagnostic ions produced a useful fingerprint maps to identify flutamide in unknown samples. Furthermore, the proposed ions may help in the metabolite studies of the drug. The method proposed here is easy, cheap and applicable for large quantity.

The distribution of 19 azole class pesticides in hexane/aqueous–organic mixtures systems and rapeseed oil (or oil solution in hexane)/organic solvents has been studied at 20 ± 1 °C. The distribution constants (P) and coefficients (D) between hydrocarbon and polar phase are calculated. It is found that all the studied pesticides are hydrophobic, i.e., in hexane–water system log P ≫ 0. Replacement of water by organic solvents results in sharp log P falling, and their values become negative. It is revealed that solutions of strong inorganic acids in anhydrous acetonitrile extract azole class pesticides from hexane and vegetable oils most fully and selectively. In particular, the acidification of acetonitrile causes a drop of D values in 50–2000 times for the majority of the studied pesticides. This phenomenon was used for the development of the improved technique for the quantitative analysis of a widely used azole class pesticides, which can be presented at trace levels in rapeseed oil. The proposed methodology is based on dissociation extraction (DE) of azoles using perchloric acid in anhydrous acetonitrile, with following clean-up of acetonitrile extract from organic impurities by hexane and aqueous solution of dipotassium hydrogen orthophosphate, and final GC–ECD (gas chromatography with electron capture detection) determination of azole fungicides. The values of obtained recoveries were between 85% and 115% with RSD values below 10%. The obtained limits of quantitation, ranged from 3.0 to 300 μg kg⁻¹, are below the maximum residue levels (MRLs) set by the European Union for the majority of pesticides. The developed method was successfully applied to different rapeseed oil samples.

Nitrated indolinyl photoprotecting groups are crucial tools extensively used in the study of neuronal signal transduction. Mononitrated photolabile protecting groups have been used effectively, however, recent advances in the introduction of a second nitro group have shown improvement in the photo efficiency of neurotransmitter (agonist) release, albeit, to varying extents, depending on the assessment methods employed. An unambiguous method is discussed based on Nuclear Magnetic Resonance (NMR), which is shown to be an effective technique in the relative overall rate comparison amongst varying nitrated protecting groups. Mononitrated and dinitrated photolabile protecting groups such as CDNI-Glu and MNI-Glu are used as an example to assess the relative value of adding a second nitro group in photoactive cage designs. Using this technique, it was shown that the second nitro group in CDNI systems enhances the overall relative rate of photocleavage by a factor of 5.8. This reported method can also be used to unambiguously determine relative rate of agonist photorelease.

A simple, ultra sensitive and selective method for the spectrophotometric determination of Ir³⁺ in various synthetic and environmental samples was reported. The analyte ions were collected on a membrane filter in the form of their red complex with 5-(2-benzothiazolyl-azo)8-hydroxy-quinoline (BTAHQ), and the absorption spectra of the colored membrane filters were acquired. Effects of pH value, sample volume, and amount of BTAHQ were examined in order to optimize sensitivity. The interference by common other ions was eliminated using appropriate masking agents. The absorbance is linearly related to the concentration of Ir³⁺ in the ranges from 0.1 to 0.8 μg/L, and from 1.0 to 7.0 μg/L, respectively, the correlation coefficients (R²) being 0.9996 and 0.9994. The molar absorptivities were calculated to be 4.81 × 10⁵ and 4.26 × 10⁷ L mol⁻¹ cm⁻¹ at 563 nm, whereas Sandell sensitivity was found as 0.391 and 0.004 ng cm⁻², respectively. The novelty and advantages of the proposed method is the highly sensitivity of the proposed method compared with all previously cited methods for iridium determination. Under the optimal conditions, the detection limit is 0.03 μg/L. The recoveries in case of spiked samples are between 98.7% and 101.5%, and the relative standard deviations range from 1.21% to 1.75%.

Polychlorinated biphenyls (PCBs) are persistent organic pollutants in insulating oil of a large number of transformers. A rapid and economical analytical method to detect PCB contamination is still required. To address this issue, we propose here the first microfluidic screening method for PCB contamination in insulating oil. The insulating oil was pretreated using a multilayer capillary column and a microfluidic liquid–liquid partitioning. PCBs in the pretreated oil were measured using a microfluidic kinetic exclusion assay. In order to detect PCBs with high sensitivity, conditions of the microfluidic kinetic exclusion assay were optimized. Measurements were rapidly completed (within 43 min). The measurement range was estimated to be 0.26–3.3 mg/kg defined as the relative absorbance from 20% to 80%. The screening performance (false positive and false negative rates) was tested on fifty real oil samples; results about these tests were discussed in detail, especially suitable cutoff by comparing with the data analyzed using high-resolution-gas-chromatography/high-resolution-mass-spectrometry. Finally, the screening performance was confirmed using our proposed stochastic screening model. A cutoff of 0.3 to judge as positive is suitable considering the risk of the PCB release into the environment.

A simple, sensitive and rapid liquid chromatographic method was developed and validated for the analysis of flunixin meglumine (flunixin-M) in bulk, pharmaceutical dosage forms, bovine liver and kidney. Analytical separation was performed in less than 4 min using a C₁₈ column with UV detection at 284 nm. A micellar solution composed of 0.15 M sodium dodecyl sulphate, 8% n-butanol and 0.3% triethylamine in 0.02 M phosphoric acid buffered at pH 7.0 was used as the mobile phase. The method was fully validated in accordance with the International Conference on Harmonization (ICH) guidelines. The limit of detection and the limit of quantitation were 0.02 and 0.06 μg mL⁻¹, respectively. The recoveries obtained were in range of 95.58–106.94% for bovine liver and kidney. High extraction efficiency was obtained without matrix interference in the extraction process and in the subsequent chromatographic determination. The method showed good repeatability, linearity and sensitivity according to the evaluation of the validation parameters.

In this paper, we describe a simple method for sampling, pre-concentrating, and separating volatile and semi-volatile components from two different cave atmospheres. Sampling is performed by capturing a volume of cave atmosphere in a Tedlar bag or Suma canister for sample storage and transport back to the laboratory. Loading a portion of the sample on a multi-bed sorption trap allows for sample pre-concentration prior to separation and detection of components on a comprehensive two-dimensional gas chromatograph (GC×GC). Comparison of two Texas caves reveals the power of comprehensive two-dimensional gas chromatography (GC×GC) for volatile separation and detection, and to our knowledge marks the first use of GC×GC for the analysis of cave atmospheres. Analysis of the results revealed 138 and 146 chromatographic signals over an S/N threshold of 500 and direct comparison of the two samples revealed 50 identical chromatographic signals. This study is a first step toward demonstrating the ability of GC×GC to separate the complex volatiles and semi-volatiles in the cave atmosphere as a fingerprinting tool.

A comprehensive review with 185 references for the analysis of commonly prescribed members of an important class of drugs, non-sedating antihistamines (NSAs), is presented. The review covers most of the methods described for the analysis of cetirizine (CTZ), ebastine (EBS), fexofenadine (FXD), ketotifen (KET) and loratadine (LOR) in pure forms, in different pharmaceutical dosage forms and in biological fluids. The review covers the period from 1991 till now.

A cobalt(II) porphyrin was successfully incorporated into polymer membranes for the optical sensing of imidazole and its derivatives. This research has led to a better understanding of the behavior of Co(II) porphyrin in solution and in polymeric membranes. In aprotic dichloromethane (DCM), the Co(II) tetraphenylporphyrin (CoTPP) and Co(II) octaethylporphyrin (CoOEP) show a sensitive response to imidazole due to the strong ligation of the N-3 on the imidazole ring to the Co(II) center, which induces an absorbance change to the Soret band. However, when doped in polymeric films, only the CoTPP exhibits moderate sensitivity towards aqueous imidazole, histamine and histidine. This weakened coordination ability of CoTPP towards imidazole in the polymer films may be due to the coordination of the plasticizer, the impurities from the THF and polymer matrix at the Co(II) center. The selectivity of the polymer films towards imidazole over common anions is high. Lifetime of the cobalt(II) porphyrin incorporated polymer film was relatively short.