Current Analytical Chemistry - Volume 1, Issue 2, 2005

During long-term treatment with STI-571 (Gleevec®, Glivec®, Imatinib), it is possible that tumor cells change their expression of proteins in order i.a. to reduce their exposure to STI-571. This would eventually result in reduced activity. In order to evaluate this possibility, we have developed an analytical technique to determine intrinsic cellular concentrations of STI-571 in tumor cells which have been manipulated to generate lines with differential expression of the multi drug resistance protein Pgp-170. A high-speed isocratic high-performance liquid chromatographic method coupled to tandem mass spectrometry for the quantification of the new anticancer agent STI-571 in cultured tumor cells is described. The method involves Measurement of Sediment (MESED) technology used for the first time in the quantitative isolation of cells from a cultured cell suspension. The sample mixture was centrifuged (10 min x 3600g), and the supernatant filtered through as HPLC filter (0,20 μm). The compounds of interest, STI-571 and the internal standard STI-571-d8 were eluted on a Waters Symmetry C18 column (50 x 2.1 mm ID, 3.5 μm particle size) using a 85/15 methanol/0.05% NH4-acetate (v/v) mixture. STI-571 and STI-571-d8 were detected by electrospray tandem mass spectrometry in the positive mode and monitored in the MRM transitions 494>394 and 502>394 respectively. The limit of quantitation of STI-571 was 5,0 ng/100 μL isolated cells containing 95 % tumor cells and 5 % medium. The recovery from the cultured tumor cells is comparable with that from RBC, i.e. ≥ 82%. The method proved to be rugged, allowing simultaneous quantification of STI-571 in cultured tumor cells and medium with sufficient precision, accuracy and sensitivity. The assay is of interest in cellular kinetic studies such as with STI-571 in CC-531 cells with different Pgp-170 expression.

An efficient method for the determination of formaldehyde in frozen fish by SPME-gas chromatography-ion trap tandem mass spectrometry was developed and validated. Experimental design was used to investigate the effects of temperature of extraction, time of extraction and matrix stirring. The calculated regression model was used to find the experimental conditions providing the optimal SPME extraction yield. Validation was carried out in terms of limit of detection (LOD), limit of quantitation (LOQ), linearity, precision, trueness and selectivity. LOD and LOQ values in the low ng kg-1 were achieved, whereas linearity was established over one order of magnitude. Good precision was obtained both in terms of intra-day repeatability and between-day precision on two concentration levels (RSD% lower than 9%). Recovery values of 82.3±1.8% and of 95.3±1.2% (n=3) were calculated at 100 μg kg-1 and 3 mg kg-1 level. Method selectivity was demonstrated by adding 2,3,4,5,6-pentafluorobenzyl alcohol as interfering substance. The applicability of the method to the determination of formaldehyde in a number of frozen fish samples was finally demonstrated.

Since its introduction over 60 years ago, gas chromatography (GC) has become a cornerstone technique of analytical chemistry. While the basic components of a GC instrument have not changed since its introduction by Martin and James in 1952, instrumentation refinement has answered demands for faster, more sensitive and selective separations of complex samples. This review will discuss the advances made in GC instrumentation within the past few years as found in the literature, granted patents and commercial advances. The revival of older instrumentation techniques for current applications will also be discussed. Hardware advances discussed include new injection techniques, advances in heating technology (including resistive heating and two source heating for GC ovens) , with the largest volume of work being done in the development of new detectors. A brief discussion on commercially available portable GCs is also included. Advances in the realm of column technology, such as commercialization of high temperature silica capillaries and stationary phases stable to 480°C, are also discussed. Novel GC stationary phase development has incorporated such materials as sol-gel poly(ethylene glycol), nanoparticles, ionic liquids, and co-polymers. Stationary phases are also discussed in relation to microfabricated GC, i.e. chip-based GC. The extensive work being completed in μGC is discussed herein, including column interfacial components for rapid heating, as well as sensitive and selective detection.

The basic principles, instrumental developments and applications of dual-opposite injection capillary electrophoresis (DOI-CE) technique are reviewed. Two different dual-opposite injection modes are described: electrokinetic injection and sequential hydrodynamic injection. The features of both injection principles are compared, followed by a detailed discussion on the biases of electrokinetic injection and how to reduce them. Flow injection system for automated dual-opposite injection is also briefly discussed. The approaches to the manipulation of the separation selectivity of anionic and cationic compounds in DOI-CE with indirect UV, mixed direct/indirect UV and contactless conductometric detection are highlighted. Finally, the performance of DOI-CE technique is illustrated by a number of practically relevant applications.

In this paper we review a series of water-soluble quinolinium boronic acid fluorescent probes, sensitive to halide and cyanide anions. We have intelligently combined the well-known halide, in particular chloride, bromide and iodide, sensing capability of the quinolinum nucleus with the fluoride or cyanide ion binding boronic acid moiety, to afford a range of water-soluble probes sensitive to fluoride, chloride, bromide, iodide and cyanide anions. These new probes offer the most attractive capability of sensing all important halides at physiological concentrations, coupled with a cyanide response at the lethal threshold level of about ≈ 20-30 μM. Some of the probes such as the BAQBAs show spectral shifts and intensity changes in the presence of fluoride and cyanide in a wavelength-ratiometric and colorimetric manner, enabling the detection of these anion concentrations at visible wavelengths. Although the sensing mechanism is different for fluoride and cyanide as compared to the other halides (chloride, bromide and iodide), the results reveal that these probes are in fact potential candidates towards the sensing of the all the halides and cyanide. Also we have constructed the corresponding control compounds that have no boronic acid moiety and are therefore insensitive to fluoride and cyanide but are mildly sensitive to chloride, bromide and iodide, similar to that of the boronic acid probes.

A new methodology is proposed for arsenic, phosphorus and titanium determination in crystalline lamellar phenylarsonate and phenylphosphonate samples by an ICP OES technique. Nitric acid, hydrofluoric acid and hydrogen peroxide were used to decompose mass aliquots of about 50 mg of titanium phenylphosphonate and phenylarsonate in a closed microwave oven. This method was shown to be suitable, reproducible and simple, and the elemental determinations provided the knowledge of the precise stoichiometry of the synthesized compounds. The concentration values obtained from triplicate gave 0.353 ± 0.008 and 0.113 ± 0.003 g g-1 for arsenic and titanium in titanium phenylarsonate samples with relative standard deviations (RSD) 2.3 and 2.7 %, respectively. The titanium phenylphosphonate sample gave phosphorus and metal concentrations of 0.153 ± 0.017 and 0.119 ± 0.003 g g-1 with RSD of 11.1 and 2.5 %, respectively. Based on the obtained results, the molar concentrations for the species were calculated as 4.71 and 2.36 mmol g-1 for the arsenic and titanium elements for phenylarsonate compound, while the values 4.94 and 2.48 mmol g-1 for phosphorus and metal were determined for titanium phenylphosphonate, respectively. The data obtained for these elements in aqueous insoluble inorganic lamellar materials, enable to establish a 2:1 proportion, whose value conformed to the expected and reliable minimum formula for the synthesized Ti(O3PC6H5)2 and Ti(O3AsC6H5)2 compounds.

A new droplet method has been developed for the determination of nitrogen dioxide in air. The method based on the reaction of nitrite with sulfathiazole in acidic medium and then coupled with NEDA (N naphthylethylenediamine dihydrochloride). The reaction product (azo dye) has an absorption maximum at 546 nm . The developed system describe the coupling of the sampling device behavior of the liquid droplet using a wind tunnel method. Nitrogen dioxide was used as a test gas. The feature of the droplet such as droplet flow rate, effect of time on the droplet size and the effect of droplet size has been studied. A linear calibration curve at different relative humidity (%) was obtained between: the concentration of NO2 obtained by the droplet method and NO2 in the wind tunnel. The proposed method is sensitive to measure NO2 in air at μg L-1 . Nitrogen dioxide is fixed as nitrite using 3% triethanolamine (TEA) trapping solution. The effect of outer diameter valve on droplet as well as the wind velocity is well addressed in this paper. The main advantage of the developed system is that the trapping solution was continuously pumped through the capillary by a means of pump with an efficiency flow rate controlled at 0.01ml min-1.

The detection of losses from nuclear material inventories whether by theft, leakage or other means is a problem of considerable importance. The earliest approaches to this problem were based on control chart like methods that made the assumption that the time series of material balance measurements (material balances are computed directly from analytical measurements of the amount of material present in such a manner that a zero balance means that all of the material is accounted for) was made up of observations that were statistically independent and identically normally distributed. These methods did not work well for two reasons. First, the series observations are often not independent. Second, if there are losses, they appear as outliers in the material balance series, which violates the normality assumption. The present paper reviews the literature in this area and discusses successful new chemometric methods that avoid the above two difficulties.

Over the past 30 years, tremendous efforts have been made for the development of a safe, costeffective and efficient device for nucleic acid delivery to mammalian cells. The approach has great contribution to analysis of gene expression, function and regulation and production of numerous recombinant therapeutic proteins, as well as bright prospects for human gene therapy. Of the existing techniques either based on synthetic material (lipid, peptide, polymer, inorganic crystal) or natural one (virus), calcium phosphate (CaP) precipitation is the most simplified and the least expensive and thus widely used for basic research and largescale production of recombinant proteins. In addition, implementation of CaP precipitates in gene therapy purposes has recently been started. So this the right time to discuss the current progress in understanding the growth kinetics and physico-chemical properties of CaP precipitates, as well as the strategies undertaken so far to modulate the growth profiling which seriously affects the sizes of the precipitates - a crucial factor for effective delivery of DNA or RNA to the cells through endocytosis. Among the approaches in nano-apatite technology, magnesium-inspired nano-apatite formulation appears to have the tremendous potential for transfecting mammalian cells considering the flexibility and simplicity in regulating crystal growth kinetics at the molecular level and eventual remarkable efficiency for both delivery and expression of an exogenous gene.

The purpose of this work is to present a peer revision to the last trends dealing with ultrasonication for sample treatment in Analytical Chemistry. The selective oxidation properties of sonication makes this tool a powerful help to distinguish, when present in solution, some metal organic species from the inorganic ones (organic mercury and inorganic mercury) or to differentiate in biological matrices non-toxic from toxic metal organic species (arsenobetaine from other toxic arseno-organic compounds). Moreover, with the recently developed multi-ultrasonicators sample throughput has been greatly increased. The development of glass probes has also led to avoid contamination from metals, which allows obtaining better quantification limits when working with metals such as Al. In very recent works the ultrasonication potential in conjunction with enzymes, has markedly enhanced the ability to extract metals from solid matrices with metal species preservation. This paper provides a fast approach to ultrasonication applications in Analytical Chemistry along with some useful recommendations in this field.

During recent years, arable land used for transgenic crops has undergone an exponential increase globally, and the tendency to augment not only the cultivated area but also the number of modified genetic traits is rather evident. However, public perception and confidence regarding genetically modified organisms (GMOs) have not paralleled this increase. Moreover, a general antipathy towards GMOs is nowadays detectable especially in Europe and there is an apparent lack of information for the consumer in many cases. To counterbalance the social alarm caused by the presence of GMO-derived ingredients in the commercial food chain, competent authorities have established appropriate regulations to guarantee the consumers' right to information and choice. In this regard, several countries have established a strict labelling policy for products containing or derived from GMO. In order to achieve these labelling requirements different approaches have been taken with the aim of detection and quantification of the presence of GMO traces, using either protein- or DNA-based methods. In this paper we review the different methodologies that are being applied to GMO studies. We describe the state-of-the-art instrumentation and technologies currently used, as well as the most recent advances in analytical systems for the detection, identification and quantification of GMOs. In addition to methodological considerations, important practical aspects such as the implementation of the analytical system into the food and feed chains will be considered. Finally, the importance of standardised/validated methods and future technological trends in the field are discussed.