Current Analytical Chemistry - Volume 8, Issue 3, 2012

Ionizing radiation used for sterilization of drugs may lead to drug degradation and therefore essential element of the validation process is the choice of optimal conditions for sterilization, i.e. radiation dose and radiation source. This investigation examines and compares radiostability of derivatives of 1-phenylpropan-1-ol exposed to the same effective doses of ionizing radiation but emitted from different sources: gamma radiation (60Co) and high energy electrons emitted by linear electron accelerator. The drugs used in this investigation were chloramphenicol, its ester (chloramphenicol sodium succinate) and analog (thiamphenicol). It was found that gamma radiation had a more destructive effect on drugs than high energy electrons. This was apparent from the change in the color intensity, increase in the concentration of free radicals, the number of radiolysis products and larger decrease in the drug content. The difference in the power between the two sources of ionizing radiation (1 kGy/h for 60Co and 10 kGy/s for high energy electrons) could account for that.

Introduction: Cigarette smoking causes devastating disease worldwide. Current cigarette classification is based on standardised tar mass values obtained from smoking-machines. However, their ability to predict disease is poor, and these mass values are primarily determined by larger particles. The aim of our study is to investigate in how far claimed tar values also reflect smaller tar particles in cigarette smoke. Methods: We developed a method to measure size-resolved particle distributions based on experimentally selecting conditions that revealed the least variety within different smoking regimes, puff numbers, diluted and undiluted ageing times, and filter taping. Next, we analysed three cigarettes types with different tar values. Cigarettes were smoked by a Cerulean SM-450 smoking machine, and subsequently smoke samples were diluted and collected in Tedlar® bags and measured for size-resolved particle distributions by a universal optical aerosol spectrometer. Results: Our method involved a smoking regime according to ISO 3308, the sixth puff, and no delayed ageing. We attained valid size-resolved particle distributions between 250 and 1,000 nm. The results revealed similar total particle counts across different cigarette types, though with different size-resolved particle distributions. In particular, smaller particles in lower tar cigarettes were underestimated. Conclusion: We developed a method to investigate submicron size-resolved particle distributions in cigarette smoke in order to compare cigarettes with different tar values. Our study suggests that mass-based tar values are a poor reflection of smaller particles in mainstream cigarette smoke, and hence supports the opinion that current tar values are a poor predictor of disease-risk and therefore that they are deceptive to smokers.

A micro/nanostructured composite electrode was constructed by introducing various portions of aluminum titanate nanopowder and gold nanoparticle into glassy carbon paste electrode and used for glutathione (GSH) detection. After the optimization of experimental parameters, the analytical characteristics of the developed system were investigated. Two linear ranges between 5-50 μM and 100-750 μM with the equation y = 0.0028x+0.0102 and y= 4e-5x+ 0.227 with the correlation coefficients of R2= 0.9943 and R2= 0.9878 were obtained. Relative standard deviation value was calculated for 250 μM GSH (n=6) and found as 6.66 %. The developed sensor was also applied for the detection of GSH in wine sample and human urine sample by using standard addition method. Data obtained from the sample application part showed that this novel nanocomposite response was not affected by the sample matrix and the nature without needing any laborious sample pretreatment procedures.

A method based on coprecipitation of Cr (III) with copper-violuric acid for the preconcentration/speciation of Cr (III) and Cr (VI) has been developed. While Cr (III) was quantitatively recovered, Cr (VI) was recovered under 15 % level at pH 6. Total Cr was determined with reducing of Cr (VI) to Cr (III) with concentrated sulphuric acid and ethanol. The concentration of Cr (VI) was calculated by the concentration difference between the total Cr and Cr (III). The influences of analytical parameters such as pH, amount of coprecipitant, sample volume were examined. The detection limit was obtained as 1.17 μg L-1 for Cr (III). The accuracy of presented method was checked by analyte addition and analysis of certified reference materials. The method for determination with atomic absortion spectrometry after preconcentration with coprecipitation of Cr (III), Cr (VI) and total Cr has been applied to tap water, waste water and soil samples.

A whole cell based biosensor is prepared by immobilizing Chlorella sp. microbes over glassy carbon electrode. The proposed biosensor is optimized for characteristics like; substrate concentration, pH, response time, durability, etc. The electrode responds linearly in concentration range of 10-14 M to 10-6 M for zinc, copper, cadmium, cobalt and nickel ions. Relative selectivity of the metal ions can be ordered in following sequence: Zn2+ >> Cu2+ ≈ Cd2+ > Co2+ > Ni2+. The biosensor has a life time of 14 days, after which, its analytical properties do not remain stable.

A new dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLMESFO)/ flow injection-spectrophotometry (FI) method for simultaneous separation and preconcentration of trace amounts of copper and zinc was developed. 1-(2-pyridylazo)-2-naphthol (PAN), 1-undecanol and acetonitrile were used as chelating agent, extraction solvent and disperser solvent, respectively. The factors influencing the complex formation and extraction by DLLME-SFO such as volumes of extraction and disperser solvents, pH, concentration of salt and concentration of the chelating agent were optimized. The optimal conditions were: volumes of extraction and dispersive solvents, 80 and 200 μL, respectively; concentration of the complexing agent, 4 x10x3mol L-1 and pH,7.5. Partial least squares (PLS) were applied for multivariate calibration and noise reduction by eliminating less important latent variables. The data obtained from the experiments were processed by chemometrics method of PLS. The linear dynamic range for Cu2+ and Zn2+ was 3–30 μg L-1 and 1–23 μg L-1, respectively. Detection limits were 1.5 μg L-1 and 0.25 μg L-1 for Cu and Zn, respectively. The relative standard deviations (R.S.D., n = 10) were found to be less than 4.5% for both of metal ions. The method was successfully applied to the simultaneous determination of Cu and Zn in the real water samples and satisfactory relative recoveries (92–107.5%) were achieved. The enhancement factors for Cu2+ and Zn2+ were found to be 85 and 86.3, respectively.

A sensitive kinetic-spectrophotometic method for the simultaneous determination of antibiotics in a mixture, specifically of amikacin (AMK), gentamicin (GTM) and etimicin (ETM), has been researched and developed with the use of reaction kinetics. 1,2-naphthoquinone-4-sulphonate (NQS) was used as the derivative reagent to produce colored products in a medium of pH 9.02, and their spectra were collected in order to monitor the kinetics of the reaction (at 475 nm). Calibration models for quantitative analysis of these mixtures were developed with the use of the principal component regression (PCR), partial least squares (PLS) and radial basis function-artificial neural networks (RBF-ANN) methods. Verification of these models with the use of a separate set of laboratory prepared mixtures was successful with the RBFANN calibration performing best. This method was then applied for the prediction of the antibiotics in real samples - spiked injection solutions, water and serum samples, and the results were successfully verified with the use of an HPLC method. Therefore, this method is a convenient alternative to the commonly used HPLC approach for the determination of these three antibiotics in variety of samples; it also has relatively high selectivity and low-costs.

A series of new sensors (1, 2, 3 and 4) bearing aromatic hydroxyl group shows the strongest binding ability for AcO- by UV-vis, fluorescence, 1H NMR titrations and theoretical investigation. The sensitivity for AcO- can be tuned by electron push-pull properties of the substituents on the aromatic ortho position of the sensor. Especially, sensor 4 containing nitro group shows the best sensitivity. The excellent sensitivity of 4 for AcO- is attributed to the structure match of host-guest. In addition, the interacted process of host-guest accompanies color changes and can be used as new colorimetric chemosensors. Real life experimental result indicates that sensor 4 can be used to qualitatively detect the fluoride in toothpaste.

The increasing industrial demand for lipases has lead to the identification of new sources of enzymes with unique properties and generated a great interest in applying rapid, reliable, specific, selective, and sensitive analytical methods for evaluating their catalytic activity. This work offers a professional look on the achievements and the emerging strategies for lipases activity determination, involving volumetry, spectrometry, radioactive assays, immunoassays, conductimetry, chromatography, and biosensors. The principle, the advantages, and the deficiencies of each of these methods are addressed in detail.

Evaluations of adulteration, geographical and botanical origin of bee-products are matters of great interest worldwide. These trends are principally related to the international market of food commodities. The chemometric tools appear as new analytical complements which, in recent years, were successfully used to define the geographical and botanical origin of food raw materials or to detect possible adulterations. The classification can be possible using different analysis criteria, such as minor and trace elements, as well as sugars and other items by the chemometric analysis. This review contains a survey of the current multivariate methods published between January 1999 and February 2011, used for the classification and authentication of honey and other bee-products. References are ordered in a way to allow easy reading and further search.