Current Analytical Chemistry - Volume 6, Issue 3, 2010

Several fluorescence reagents (i.e., Fmoc-Cl, DMEQ-COCl, DBD-F, PSC and DNS-Cl), which are reactive with an amino functional group, were evaluated for the labeling of the β-glycosylamine moiety in a glycoprotein. Because the β-glycosylamine is released from a glycoprotein containing asparaginyl-oligosaccharides (N-linked oligosaccharide) with glycoamidase F (PNGase F), the enzyme amount and the reaction time which affect the digestion of glycoprotein were first optimized. The FL labeling, LC separation and MS detection conditions were also optimized. The β- glycosylamines liberated from ovalbumin and fetuin were labeled with each reagent, separated by liquid chromatography and detected by TOF-MS under optimized conditions. The fluorescence reagents were evaluated by the number of identified oligosaccharides. As a result, Fmoc-Cl and DMEQ-COCl were suitable for the labeling of β-glycosylamines. Various fragment ions based on the carbohydrate units appeared on the MS/MS spectra. Among the product ions, the specific ions, i.e., m/z 443.2 and 970.4 derived from Fmoc-labeled oligosaccharides, were the most important for identifying the Nlinked oligosaccharide, while m/z 467.2 and 994.4 appeared on the spectra of the DMEQ-labeled oligosaccharides as the specific ions. The identification of N-linked oligosaccharides in glycoproteins seems to be possible by the proposed method involving the enzyme digestion of glycoprotein, FL labeling of the released β-glycosylamines, LC separations of the derivatives and Q-TOF-MS/MS detection.

Biocatalysis in nonaqueous media currently constitutes a promising research area which has already demonstrated its potential in numerous and varied applications. Several possibilities exist for the analysis of a wide range of poorly water-soluble analytes present in samples of food, pharmaceuticals, petrochemicals and cosmetic products, among others. The idea of assembling this kind of biocatalysis with flow management approaches clearly seems to be advantageous since it permits confined, precise and reliable analysis within a shorter timeframe while minimising human exposure to organic solvents and toxic effluent production. This article reviews the state-of-the-art of flowing stream systems comprising immobilized enzymes in nonaqueous media. Particular emphasis is devoted to categorising the enzymatic preparations operating in an organic environment: enzyme electrodes and enzyme reactors. The main approaches exploiting the use of immobilized enzymes in water-restricted environments using flow injection analysis for analytical purposes are presented in detail and possible future trends are discussed.

Indole-3-carboxaldehyde (In3C) molecules were deposited on the glassy carbon (GC) electrode by electrochemical methods in acetonitrile (containing 0.05 M TBATFB). Deposition of In3C was performed by cyclic voltammetry scanning from 0.0 V to 2.0 V at a scan rate of 50 mV s-1 for 10 cycles in 1 mM In3C solution. The modified surface (In3C-GC) was characterized by cyclic voltammetric response of ferrocene as a redox probe. Elemental composition of the surface was analyzed by X-ray photoelectron spectroscopy (XPS). The applicability of this modified surface was then investigated for the determination of dopamine (DA) and uric acid (UA) in the presence of ascorbic acid (AA) using differential pulse voltammetry. Detection limits were calculated as 1.70 μM for DA and 4.99 μM for UA. The linear ranges of the calibration curves were found between 10 μM -100 μM for both DA and UA in the presence of 100 μM AA. The proposed method was applied to the determination of DA and UA in pharmaceutical preparations and urine samples with satisfactory results.

The S-(-)-enantiomer of ofloxacin, a chiral fluoroquinolone antibiotic, exhibits an antibacterial activity 8-128 times higher than that of the R-(+)-isomer. A new stereospecific nano-LC method for the enantioseparation of the ofloxacin racemic mixture was developed using an achiral reversed phase column (Pinnacle II Phenyl 3 μm, 15 cm x 100 μm ID) and heptakis-(2,3-diacetyl-6-sulfo)-β-cyclodextrin (HDAS-β-CD) as a mobile phase chiral additive. Best enantioresolution was achieved using a mobile phase containing acetonitrile, 50 mM sodium acetate buffer pH 3 (30:70, v/v) and 5 mM of HDAS-β-CD. The flow rate thorough the capillary column was estimated in 620 nL/min and the wavelength for the UV detection was set at 290 nm. Good separation of the enantiomers was obtained is less than 10 min with a resolution and selectivity factor of 1.66 and 1.88, respectively. The effect of several experimental parameters on the chiral separation was also evaluated and the method was successfully validated in terms of linearity, accuracy and precision, showing the enantiorecognition capability of the employed sulfated β-CD toward the ofloxacin chiral drug.

In this work results are reported on the determination of some elements, Ni, Sn, Te and Zn, present at ultratrace levels (ng g-1) in three different samples of metallurgical lead, i.e. electrolytically refined lead, thermally refined lead and lead with added impurities, assigned to be employed as standard reference materials by BCR. The Instrumental Neutron Activation Analysis was used for its characteristics to be a primary analytical method and for reaching high sensitivity and accuracy. The γ-spectrometry measurements have been performed by means of a counter system operating in anticoincidence; for the Sn and Te measures a radiochemical separation of the main interfering radionuclides was necessary. The irradiation was performed in the central channel of the Triga Mark II reactor of the R.C.-Casaccia, ENEA, at a neutron flux of 2.68x1013 nxcm-2xs-1; the irradiation time was protracted to reach a total integrated flux of 2x1019 nxcm-2. In this way, 42.2 ng g-1 of Ni, 1.7 ng g-1 of Sn, 7.6 ng g-1 of Te and 35.5 ng g-1 of Zn in the Electrolytically Refined Lead and 24.2 ng g-1 of Ni, 5.7 ng g-1 of Sn, 8.2 ng g-1 of Te and 18.5 ng g-1 of Zn in the Thermally Refined Lead, respectively, were measured. The third sample was used as reference: it was obtained by adding impurities to a Thermally Refined Lead. In this case each element was present at μg g-1 level. It should be underlined that for some elements at ultra-trace levels (i.e. Ni, Sn and Te) only few measurements were useful in the relative certification: in particular, only using a radiochemical separation and an anti-Compton suppression a very low limit of detection was reached.

The quality assessment of water in term of organometallic compounds is one of the key tasks of modern environmental analytical chemistry. For this purpose a rapid and very sensitive method based on solid-phase microextraction (SPME) followed by gas chromatography-inductively coupled plasma-mass spectrometry (GC-ICP-MS) was developed and validated aimed at the determination of dimethyl-, dibutyl- and tributyltin in water samples. A divinylbenzene/ carboxen/polidimethylsiloxane fiber was used for the SPME sample treatment. Coupling of the ICP-MS with GC was accomplished developing an easy-to-fit in-house interface. In general optimal conditions were found by using the enhanced “hot plasma/protective ion extraction” introduction system. Validation was carried out in terms of limit of detection, limit of quantitation, linearity, precision and trueness. GC-ICPMS made possible the detection of the organotin compounds at ultratrace levels, quantitation limits ranging from 0.04 to 5 ng l-1. Linearity was established over two orders of magnitude for all the investigated compounds. Good precision was obtained both in terms of intra-day repeatability and between-day precision on two concentration levels (RSD lower than 15%). Recovery values ranging from 75±2% to 99±1.2% (n = 3) were calculated. The method was proved rapid, GC-ICPMS allowing for the separation of organotin species in less than 7 minutes. The method was used in routine analysis of environmental samples (fresh and marine water samples).

A simple, accurate and sensitive kinetic method has been developed for the determination of three cardiovascular drugs: Betaxolol, Clopidogrel, and Imidapril in pharmaceutical formulations. The method is based on the alkaline oxidation of the selected drugs with potassium manganate(VII) at room temperature (25°C) to produce a bluish-green colored product. The reaction is followed spectrophotometrically by measuring the rate of change of absorbance at 610 nm as a function of time. The fixed-time (ΔA) method is adopted for constructing the calibration curves, which were found to be linear over the concentration ranges of 0.40-2.0 μg ml-1 Betaxolol, 1.0-10.0 μg ml-1 Clopidogrel, and 6.0-16.0 μg ml-1 Imidapril. The implemented fixed times were 15 min for Betaxolol and Clopidogrel and 10 min for Imidapril. The proposed method has been successfully applied to pharmaceutical formulations of each drug. The percentage relative error and the coefficient of variation were less than 0.6 and 1.2 respectively. The lower limits of quantitation (LOQ) were 9.75x10-7 M Betaxolol, 3.62x10-6 M Clopidogrel, and 4.22x10-6 M Imidapril. The determination of the investigated drugs by the fixed-concentration and the rate-constant methods is feasible with the regression equations obtained, but the fixed-time method proves to be more applicable.

This article presents an overview of the different analytical methods available for performing pesticide degradation studies in water and environmental samples by different processes. How long the pesticide remains in the environment depends on how strongly it is bounded by other components and how readily it is degraded. It is also depends on the environmental conditions at the time of application, pH, temperature, soil and water content. The degree of mineralization achieved under advanced oxidation processes (AOP), photo-Fenton reactions [FR], and ozonation processes, and the identity of by-products of a large number of compounds belonging to the major pesticide families pirethroides, organochlorides and organophosphorus compounds are presented. Critical comments are aimed at emphasizing the lack of suitable analytical methods adequate to determine the kinetics of both the formation and disappearance of by-products and to identify their chemical structures. More specifically, the crucial role of gas chromatography and liquid chromatography in combination with mass spectrometry is described. In the following manuscript, an overview of the pesticide degradation phenomena is given, and an attempt is made to predict how factors and conditions influence the phenomena. SPME and GC/MS are sufficiently accurate methods to support the identification of pesticides in different degradation processes.

Ionic liquid has been rapidly developed as an environment-friendly acceptor phase for microextraction and sample preparation in analytical chemistry in recent years. Present microextraction with ionic liquid mainly includes liquid phase microextraction, single drop liquid phase microextraction, solid phase microextraction, dispersive liquid phase microextraction and cold induced aggregation microextraction. In general, the microextraction with ionic liquid exhibits higher extraction efficiency and enrichment factor than that with organic solvent. Hydrophobic ionic liquids are difficult to fully mix with aqueous phase due to very high interfacial tension between the ionic liquid and water, a relatively long extraction time and manual stirring process were strongly required for improving extraction efficiency of the microextraction with ionic liquid. Recently, a novel microextraction technology termed as dispersive liquid phase microextraction was developed and applied rapidly, in which the ionic liquid was dispersed completely into the aqueous phase and the analytes will more easily migrate into the ionic liquid phase because of the much large contact area, its extraction time was shorten remarkably and whole extraction can be completed within several minutes. Moreover, the combinations of many modern analytical technologies with the ionic liquid microextraction were investigated and improved, special to gas chromatography and gas chromatography mass spectrometry. These have widely been applied to determination of ultra trace metal and organic compound in water or other samples. Up to now, the microextractions with ionic liquid have increasingly become one of most important method for samples preparation in analytical chemistry.