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Analytical and Bioanalytical Chemistry (v.376, #1)

It is a far better thing...or Why are the accepted writing styles in technical publications so narrow? by J. Fetzer (pp. 1-2).

Grazing incidence small-angle X-ray scattering: an advanced scattering technique for the investigation of nanostructured polymer films by P. Müller-Buschbaum (pp. 3-10).

Hamburg workshop on the "application of synchrotron radiation in chemistry"With grazing incidence small-angle X-ray scattering (GISAXS) the limitations of conventional small-angle X-ray scattering with respect to extremely small sample volumes in the thin-film geometry are overcome. GISAXS turned out to be a powerful advanced scattering technique for the investigation of nanostructured polymer films. Similar to atomic force microscopy (AFM), a large interval of length between molecular and mesoscopic scales is detectable with a surface-sensitive scattering method. While with AFM only surface topographies are accessible, with GISAXS the buried structure is also probed. Because a larger surface area is probed, GISAXS also has a much larger statistical significance compared to AFM. Due to the high demand on collimation, GISAXS experiments are based on synchrotron radiation. Nanostructures parallel and perpendicular to the sample surface observable in thin poly(styrene-block-isoprene) diblock copolymer films are presented as an example of the possibilities of GISAXS.

Keywords: Nanostructures Surface scattering Synchrotron radiation Grazing incidence small-angle X-ray scattering (GISAXS) Atomic force microscopy (AFM)

Luminescence-based whole-cell-sensing systems for cadmium and lead using genetically engineered bacteria by Ranjit S. Shetty; Sapna K. Deo; Puja Shah; Yan Sun; Barry P. Rosen; Sylvia Daunert (pp. 11-17).

Whole-cell-based sensing systems that respond to cadmium and lead ions have been designed and developed using genetically engineered bacteria. These systems take advantage of the ability of certain bacteria to survive in environments polluted with cadmium and lead ions. The bacteria used in this investigation have been genetically engineered to produce reporter proteins in response to the toxic ions. This was achieved by modifying a strain of Escherichia coli to harbor plasmids pYSC1 and pYS2/pYSG1. In these dual-plasmid-based sensing systems, the expression of the reporters β-galactosidase and red-shifted green fluorescent protein (rs-GFP) was controlled by CadC, the regulatory protein of the cad operon. Regulation of the expression of the reporter proteins is related to the amount of cadmium and lead ions employed to induce the bacteria. The bacterial sensing systems were found to respond to cadmium, lead, and zinc ions, and had no significant response to nickel, copper, manganese, and cobalt.

Keywords: Whole-cell sensing Cadmium resistance Chemiluminescence Fluorescence

Molecularly imprinted polymers for on-line clean up and preconcentration of chloramphenicol prior to its voltammetric determination by M. L. Mena; L. Agüí; P. Martinez-Ruiz; P. Yáñez-Sedeño; A. J. Reviejo; J. M. Pingarrón (pp. 18-25).

The performance of a molecularly imprinted polymer (MIP) as a selective solid-phase extraction sorbent for the clean-up and preconcentration of the antibiotic chloramphenicol is described. The MIP was prepared using chloramphenicol as the template, (diethylamino)ethyl methacrylate as the functional monomer, and ethylene glycol dimethacrylate as the cross-linking monomer, and using tetrahydrofuran as the solvent. Detection of chloramphenicol was carried out by square-wave voltammetry at electrochemically activated carbon fiber microelectrodes. Chloramphenicol was eluted from the MIP microcolumn with methanol. Different experimental variables (sample pH, eluent volume, analyte and eluent flow rates and sample volume) associated with the rebinding/elution process were optimized. For a 250 mL sample, a nominal enrichment factor of 500 was attained, and for a chloramphenicol concentration of 3.0×10⁻⁸ mol L⁻¹ (9.7 μg L⁻¹) a recovery of 96±4% was obtained. A range of linearity for chloramphenicol between 3.0×10⁻⁸ and 1.0×10⁻⁵ mol L⁻¹ was obtained by loading 17 mL of analyte solutions of different concentration, eluting with 0.5 mL methanol, evaporating under a stream of nitrogen and dissolving the residue in phosphate buffer of pH 7.8. The MIP selectivity was evaluated by checking several substances with similar molecular structures to that of chloramphenicol. The applicability of the MIP for both clean up and preconcentration was demonstrated by determining chloramphenicol in ophthalmic solutions and spiked milk at different concentration levels.

Keywords: Molecularly imprinted polymers, MIPs Clean-up Preconcentration Solid-phase extraction Chloramphenicol

Biosorption of cadmium, copper, lead and zinc by inactive biomass of Pseudomonas Putida by Rafael Pardo; Mar Herguedas; Enrique Barrado; Marisol Vega (pp. 26-32).

The accumulation of Cd(II), Cu(II), Pb(II) and Zn(II) at mg L⁻¹ concentration levels by inactive freeze-dried biomass of Pseudomonas Putida has been investigated. These metals could be efficiently removed from diluted aqueous solutions. A contact time of 10 min was sufficient to reach equilibrium. The pH has a strong effect on metal biosorption and the optimal pH values were 6.0, 5.0–6.0, 6.0–6.5 and 7.0–7.5 for Cd(II), Cu(II), Pb(II) and Zn(II) respectively. Under these conditions there was 80% removal for all metals studied. The process of biosorption can be described by a Langmuir-type adsorption model. This model accounts for 98% of the data variance. The K _A and q _max parameters for each metal are strongly correlated (at confidence levels greater than 98%) with the metal acidity, quantified by the constant of the corresponding M(OH)⁺ complex, thus confirming previous assertions by other authors.

Keywords: Heavy metals Biosorption P. Putida Biomass

Free radical-scavenging activity of indolic compounds in aqueous and ethanolic media by Antonio Cano; Olga Alcaraz; Marino B. Arnao (pp. 33-37).

Indolic compounds are a broad family of substances present in microorganisms, plants and animals. They are mainly related with tryptophan metabolism, and present particularities that depend on their respective chemical structures. The most important members of the family are the plant hormone, indole-3-acetic acid, and the animal hormone, melatonin. An important characteristic of some indolic compounds is that they may be useful as chemical preventive agents against diseases such as cancer, oxidative stress, etc. For this reason, the possible antioxidant activities (free radical-scavenging activity) of several indoles were studied. The2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid /H₂O₂/HRP decoloration method was applied to determine both hydrophilic (in buffered media) and lipophilic (in organic media) antioxidant properties of the indolic compounds. Also, a study of the hydrophilic antioxidant activities of indoles at different pH values (between 4.5 and 8.5) was made. Finally, their possible role as diet plant antioxidants is discussed.

Keywords: 2,2'-Azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) Antioxidant activity Indolacetic acid Indolcarbinol Plant indoles

Flow injection analysis: Rayleigh light scattering technique for total protein determination by Ezequiel Vidal; Miriam E. Palomeque; Adriana G. Lista; Beatriz S. Fernández Band (pp. 38-41).

A novel flow injection analysis (FIA) method with Rayleigh light scattering (RLS) detection was developed for the determination of total protein concentrations. This method is based on the weak intensity of RLS of bromothymol blue (BB) (3′,3″-dibromothymolsulfonephthalein) which can be enhanced by the addition of protein in weakly acidic solution. A common spectrofluorimeter was used as a detector. It was proved that the application of this method to quantify the total proteins in real samples by using bovine serum albumin was possible. The RLS signal was detected at λ _ex=λ _em=572 nm. The linear range was 7.0–70.0 μg mL⁻¹, the detection limit was 3.75 μg mL⁻¹, the reproducibility was 5.5% (n=7), and the sample throughput was 26 h⁻¹.

Keywords: Rayleigh light scattering FIA Proteins

Resonance Rayleigh scattering spectra for studying the interaction of aminoglycoside antibiotics with pontamine sky blue and their analytical applications by Xiaoli L. Hu; Shaopu P. Liu; Nianbing Li (pp. 42-48).

In a weakly acid medium, some aminoglycoside antibiotics, such as kanamycin (KANA), gentamicin (GEN), tobramycin (TOB), and neomycin (NEO), or acid bisazo dye pontamine sky blue (PSB) can only produce very weak resonance Rayleigh scattering (RRS) signals. However, when the two agents react with each other to form the ion association complexes, the RRS intensity can be enhanced greatly and a new RRS spectrum and a significant enhancement of the RRS intensity in the wavelength range 350–600 nm can be observed. The maximum scattering peak is at 580 nm. There is a linear relationship between the RRS intensity and the antibiotic concentration in the range 0.01–6.0 μg mL⁻¹ at 580 nm. This RRS method has therefore been developed for the determination of trace levels of aminoglycoside antibiotics. The detection limits (3σ) of the four antibiotics, whose order of sensitivity is KANA>NEO>TOB>GEN, are 5.8–6.9 ng mL⁻¹. This method has a good selectivity and has been successfully applied to the quick determination of antibiotics not only for injections and ear drops, but clinic serum samples as well. In addition, quantum chemistry-based analysis of the reaction mechanism, the factors influencing the RRS spectra, and the reasons for the enhancement of RRS are discussed.

Keywords: Resonance Rayleigh scattering Aminoglycoside antibiotics Pontamine sky blue Determination

Preliminary characterization of a light-rare-earth-element-binding peptide of a natural perennial fern Dicranopteris dichotoma by Haiou Wang; Xiao-quan Shan; Shuzhen Zhang; Bei Wen (pp. 49-52).

A light-rare-earth-element (LREE)-binding peptide was isolated from LREE hyperaccumulator Dicranopteris dichotoma leaves and characterized in terms of molecular weight and ultraviolet absorption spectrum. The molecular weight of the LREE-binding peptide was determined to be 2208 Da by matrix-assisted laser-desorption ionization–time of flight mass spectrometry (MALDI–TOFMS). The characteristic ultraviolet absorption spectrum of the peptide was observed at 220–300 nm, suggesting that the peptide chain contained aromatic amino acids. Compared to the unique features of the phytochelatins with a low absorption at 280 nm, the LREE-binding peptide is unlikely to be a typical phytochelatin. The present study suggests that the LREE-binding peptide is probably a natural peptide in D. dichotoma, and it may play an important role in hyperaccumulation of LREEs.

Keywords: Light-rare-earth-element-binding peptides Hyperaccumulator Dicranopteris dichotoma Matrix-assisted laser-desorption ionization–time of flight mass spectrometry

One-step cleanup for PAH residue analysis in plant matrices using size-exclusion chromatography by A. Hubert; P. Popp; K.-D. Wenzel; W. Engewald; G. Schüürmann (pp. 53-60).

A new one-step cleanup procedure, based on size-exclusion chromatography (SEC), usable for the extracts from accelerated solvent extraction (ASE), Soxhlet extraction, or ultrasonic extraction (USE), is described. The method is suitable for the determination of polycyclic aromatic hydrocarbons (PAHs), especially from very complicated plant matrices (e.g. pine needles, deciduous leaves, mosses). The main improvement compared with previous conventional procedures is that analyte peaks barely overlap with matrix peaks in the chromatograms and that it is a very rapid and simple one-step procedure with clearly improved analytical performance. Essential advantages of this SEC procedure are the sharper GC–MS chromatograms for the PAH fraction at retention times between 9.2 and 12.0 min, distinctly separated substance peaks resulting in better analysis, shorter running times, and lower solvent consumption.

Keywords: Cleanup Size-exclusion chromatography PAHs Pine needle

Optimization and application of SPME for the gas chromatographic determination of endosulfan and its major metabolites in the ng L⁻¹ range in aqueous solutions by A. B. Deger; T. J. Gremm; F. H. Frimmel; L. Mendez (pp. 61-68).

In the present study an analytical method was optimized for the determination of α-endosulfan, β-endosulfan, endosulfan sulfate, endosulfan ether and endosulfan lactone in small volumes of environmental aqueous samples using solid-phase microextraction (SPME) and gas chromatography–electron capture detection (GC–ECD). A 100 µm polydimethylsiloxane (PDMS) phase was used for the extraction. The limit of detection (LOD) for the analytes varied between 0.01 and 0.03 µg L⁻¹ with a relative standard deviation of 3 to 11%. The influence of the ionic strength on the extraction efficiency was investigated for the individual compounds. α-Endosulfan, β-endosulfan, endosulfan sulfate and endosulfan ether were extracted successfully without salt addition. The extraction efficiency of endosulfan lactone was improved with 30% NaCl content. A general decrease in extraction efficiency for α-endosulfan, β-endosulfan, endosulfan sulfate and endosulfan ether with high NaCl content (20–30%) in the solution was observed due to glass surface adsorption. No effect of dissolved organic material (DOM) on the extraction efficiency was observed. The extraction coefficients changed between Log K=2.17 and 3.33. A sample from the Antarctic region was analyzed using the optimized GC–ECD/SPME method. To confirm the results obtained for the real sample a GC with a mass spectrometer (MS) was used. Endosulfan sulfate, the most toxic metabolite of endosulfan, was found in the sample at a concentration of 0.3 µg L⁻¹.

Keywords: Solid-phase microextraction (SPME) Gas chromatography Electron capture detection α-Endosulfan β-Endosulfan Endosulfan sulfate Endosulfan ether Endosulfan lactone Endosulfan metabolites

Analysis of off-flavors in the aquatic environment by stir bar sorptive extraction–thermal desorption–capillary GC/MS/olfactometry by D. Benanou; F. Acobas; M. R. de Roubin; F. David; P. Sandra (pp. 69-77).

The off-flavor compounds 2-methylisoborneol (MIB), geosmin, 2,4,6-trichloroanisole, 2,3,6-trichloroanisole, 2,3,4-trichloroanisole, and 2,4,6-tribromoanisole were analyzed in water samples by stir bar sorptive extraction (SBSE) followed by on-line thermal desorption (TD) capillary GC/MS. Quantification was performed using the MS in the single-ion-monitoring mode (SIM) with 2,4,6-trichloroanisole-D₅as internal standard. Quantification limits are 0.1–0.2 ng L⁻¹ for the haloanisoles, 0.5 ng L⁻¹ for geosmin, and 1 ng L⁻¹ for MIB. The relative standard deviations at the quantification limit ranged from 7 to 14.6%. SBSE recovery was evaluated by spiking real water samples and varied from 87 to 117%. More than twenty samples per day can be analyzed by SBSE–TD–capillary GC–MS. The same technique in combination with olfactometry was used to elucidate unknown odorous compounds in water samples.

Keywords: Off-flavors Water MIB Geosmin Haloanisoles Stir bar sorptive extraction Capillary GC–MS Olfactometry

Determination of inorganic selenium species by miniaturised isotachophoresis on a planar polymer chip by Jeff E. Prest; Sara J. Baldock; Peter R. Fielden; Nicholas J. Goddard; Bernard J. Treves Brown (pp. 78-84).

The use of miniaturised isotachophoresis to allow the simultaneous determination of two inorganic selenium species has been investigated using a poly(methyl methacrylate) chip with a 44-mm-long, 200-μm-wide, 300-μm-deep separation channel. The miniaturised device included an integrated on-column, dual-electrode conductivity detector and was used in conjunction with a hydrodynamic fluid transport system. A simple electrolyte system has been developed which allowed the separation of selenium(IV) and selenium(VI) species to be made in under 210 s. The limits of detection were calculated to be 0.52 mg L⁻¹ for selenium(IV) and 0.65 mg L⁻¹for selenium(VI). The method allowed the separation of the selenium species from a range of common anions including fluoride, nitrate, nitrite, phosphate, sulfate and sulfite.

Keywords: Isotachophoresis Miniaturisation Chip Selenium Conductivity detection

Effects of γ-sterilization on butyltin homogeneity and content in sediments: a GC–ICP–MS study by Lu Yang; Chrystelle Bancon-Montigny; Zoltán Mester; Ralph E. Sturgeon; Scott N. Willie; Victor J. Boyko (pp. 85-91).

A GC–ICP–MS method based on extraction and alkylation of butyltins with sodium tetraethylborate was used to quantitatively assess the fate of these analytes in solutions and sediments following exposure to γ-irradiation. The effects of a 2.5 Mrad sterilization dose on three butyltin species in both methanolic calibration solutions and in sediment matrices were investigated. Although significant losses of tributyltin (TBT, 90%), dibutyltin (DBT, 100%) and monobutyltin (MBT, 80%) were detected in standard solutions prepared in methanol following γ-irradiation, no species inter-conversion occurred. Some degradation of TBT (38%) and DBT (32%) but no significant change in MBT content was found using a spiked sediment CRM HISS-1. Conversion DBT to MBT in spiked HISS-1 was deduced. Much smaller degradation of TBT (16% loss) and 10% loss of DBT by conversion to MBT (14% gain) was registered using a sediment blend of PACS-2 and HISS-1 (SOPH). Despite some initial losses of TBT and DBT due to irradiation, better than 2% RSD in both TBT and DBT concentrations measured in twelve different bottles of blended sediment SOPH were obtained, indicating the material may be considered homogeneous for these analytes. Results from a long-term five-year stability study of PACS-2 show that all three butyltins are stable during storage at 4 °C followed with 2.5 Mrad minimum dose of γ-irradiation sterilization treatment.

Keywords: Irradiation Tributyltin Dibutyltin Monobutyltin Sediment GC ICP–MS

High-performance liquid chromatography with diamond ATR–FTIR detection for the determination of carbohydrates, alcohols and organic acids in red wine by Andrea Edelmann; Josef Diewok; Josefa Rodriguez Baena; Bernhard Lendl (pp. 92-97).

A horizontal diamond attenuated total reflection (ATR) element has been incorporated in a flow-through cell with low dead volume and used for on-line mid-IR detection in high-performance liquid chromatography. The chemical inertness of the ATR element permitted the use of a strongly acidic mobile phase in the isocratic separation. The hyphenation was used for the analysis of organic acids, sugars and alcohols in red wine. In the case of co-eluting analytes multivariate curve resolution–alternating least squares (MCR–ALS) was successfully employed for quantitative analysis.

Keywords: HPLC–FTIR Diamond ATR Wine analysis MCR–ALS

Determination of zearalenone and ochratoxin A in soil by Gerda Krog Mortensen; Bjarne W. Strobel; Hans Christian B. Hansen (pp. 98-101).

Mycotoxins are secondary metabolites, formed by the action of fungi on agricultural crops in the field or during storage. These metabolites are highly toxic to animals and humans and high levels have been measured in agricultural crops. In order to evaluate human risks due to ingestion of mycotoxin-contaminated food different methods have been developed for analysis of mycotoxins in cereals and maize. In this project the focus was on mycotoxins in agricultural soil and the fate of these toxins in the soil–water-plant system. Two different mycotoxins were selected in the study: zearalenone (ZON) produced by species of Fusarium or Aspergillus and ochratoxin A (OTA) produced by species of Penicillium. We developed a method for analysis of these toxins in soil. Soil samples were extracted with methanol–water (9:1) and purified by solid-phase extraction (SPE, C8-columns). The final extract was analysed using high-pressure liquid chromatography (HPLC) with fluorescence detection. A Phenyl Hexyl column was used to separate the toxins. The detection limits obtained were 0.1 and 1.0 μg kg⁻¹ dry weight (dw) for OTA and ZON, respectively. The developed method has been used for analysis of different soils in connection with growth chamber experiments. The soil types used in the growth chamber experiments were a sandy soil, a sandy clay soil, and a soil with high content of organic matter. The recovery was determined as 85.8 and 93.4% and the repeatability to 5.1 and 12.8% for OTA and ZON, respectively. The reproducibility obtained was 8.5 and 15.0% for soil samples, representing concentration levels from 0.2–30 μg kg⁻¹ dw (OTA) and from 1.0–100 μg kg⁻¹ dw (ZON).

Keywords: Mycotoxins Soil OTA ZON Method validation

Evaluation of stability of arsenic species in rice by Isabel Pizarro; Milagros Gómez; Maria Antonia Palacios; Carmen Cámara (pp. 102-109).

Although most edible vegetables do not accumulate As at a high rate, rice, carrots and certain others are exceptions. In addition to nutritional or toxicological considerations, the relatively high level and variety of As species present in rice make it a very suitable matrix for a candidate reference material representative of terrestrial biological samples.An analytical procedure was developed for As speciation in rice based on the use of a 1:1 methanol–water mixture for species extraction, an anion Hamilton PRPX-100 column (at pH 6, and phosphate mobile phase 10 mM), and a cation Hamilton PRP-X200 column (at pH 2.8 in pyridine formiate 4 mM) for species separation and final determination by HPLC–ICP–MS.The detection limits for dry flour rice expressed as As were 2 and 3 ng g⁻¹ for As(III) and AsB on the cation column and 3, 6 and 5 ng g⁻¹ for As(V), MMA and DMA, respectively, on the anion column.The methodology developed was applied to check the stability of As species in the water–methanol extract and also under different processing steps and storage time and temperature conditions.It was demonstrated that the As species in the water–methanol extracts stored at +4 °C remained stable for at least one month. Once the rice grains are ground, the MMA and As(V) species are not stable under any storage conditions probably due to microbiological activity. When ground rice is γ-irradiated species remain stable although the AsB does not appear.

Keywords: Rice As-speciation HPLC ICP–MS Stability Irradiation

Investigation of the direct hydride generation nebulizer for the determination of arsenic, antimony and selenium in inductively coupled plasma optical emission spectrometry by Illiana Rojas; Miguel Murillo; Nereida Carrión; José Chirinos (pp. 110-117).

A direct hydride generation nebulizer (DHGN) was explored for introduction of the sample in inductively coupled plasma–optical emission spectrometry (ICP–OES) using radially viewed mode. This simple hydride generation system was constructed in our laboratory and requires similar plasma operating conditions to conventional nebulizer–spray-chamber arrangements. This work was focused on the optimization of the operating conditions for hydride generation and evaluation of the main analytical figures of merit for the determination of As, Sb and Se. The excitation conditions of the ICP–OES instrument operated with the DHGN were also explored. Results showed that the analytical performance of the new system for the determination of As, Sb and Se was superior to that of conventional nebulization systems. The DHGN also enabled the determination of elements that do not form volatile hydrides, but with less sensitivity than conventional nebulization systems. Evaluation of the plasma robustness showed that gases generated in hydride generation do not significantly affects the plasma discharge. Similar to conventional hydride generation techniques, analysis with DHGN was susceptible to non-spectroscopic interferences produced by transition metals. Finally, the utility of the DHGN in practical ICP–OES studies was demonstrated in the determination of trace elements in an oyster tissue standard reference material.

Keywords: Direct hydride generation nebulizer Hydride generation Inductively coupled plasma optical emission spectrometry Arsenic Antimony Selenium

Comparison of aqua regia and HNO₃-H₂O₂ procedures for extraction of Tl and some other elements from soils by J. Pavlíčková; J. Zbíral; E. Čižmárová; V. Kubáň (pp. 118-125).

The relationship between aqua regia (ISO 11466) and HNO₃-H₂O₂ (ISO/CD 20279) extraction procedures for atomic emission spectrometric (ICP/OES and ICP/MS) determinations of Tl, P, Mn, Fe, Mg, Ca, Sr, Al, K, As, Bi, Zn, Pb, Co, Cd, Ni, V, Be, Cu and Cr was investigated. Soil samples (155) representing areas with different contents of the elements were selected for the comparison. Tl was the element of the highest interest and therefore the sampling sites were chosen to achieve as wide range of Tl contents as possible. Both extraction procedures are comparable in results (differences lower than 10% for the most of the elements) for all the tested elements. Statistically non-significant differences between the two extraction procedures were found for P, Zn, V and K (the slope was very close to 1 and the intercept included zero). Statistically significant values of intercepts were found for Fe, Al, Ca, Cd, Sr and Ni. Significantly higher results for aqua regia were found for Cu (12%), Pb (17%), Mn (11%) and lower results by aqua regia were found for Mg (4%), As (13%), Co (20%), Be (11%), Cr (4%) and Bi (6%). The results for Tl, the element of the highest interest, after HNO₃-H₂O₂ extraction procedure, were approximately 6% higher than the results after aqua regia extraction. Content of Tl in the soil samples was from 0.08 to 2.8 mg kg^-1. A highly significant linear relationship was found (R ²=0.97).

Keywords: Arable soils Inductively coupled plasma mass spectrometry Elements Tl Extraction

Spectrophotometric determination of sorbic and benzoic acids in fruit juices by a net analyte signal-based method with selection of the wavelength range to avoid non-modelled interferences by Nilda R. Marsili; María S. Sobrero; Héctor C. Goicoechea (pp. 126-133).

Sorbic (SOR) and benzoic (BEN) acids were determined in fruit juice samples by using a net analyte signal-based methodology named HLA/GO (an hybrid linear analysis presented by Goicoechea and Olivieri) applied to spectroscopic signals. The calibration set was built with several fruit juices in order to take into account the natural variability and concentrations of both analytes covering the range usually present in commercial samples. Relative errors of prediction (REP %) of 3.6 and 5.2% were calculated for SOR and BEN respectively. Several figures of merit were calculated—sensitivity, selectivity, analytical sensitivity, and limit of detection. The method is quantitative, with reasonably good recoveries and excellent precision (less than 1%). Wavelength selection was applied, based on the concept of net analyte signal regression, and it allowed us to improve the method performance in samples containing non-modelled interferences, e.g. fruit juices different to those used to build the calibration model.

Keywords: Net analyte signal-based methods Sorbic acid Benzoic acid Fruit juices

Separation of cocaine stereoisomers by capillary electrophoresis using sulfated cyclodextrins by B. Cabovska; A. B. Norman; A. M. Stalcup (pp. 134-137).

A capillary electrophoretic method for the separation of cocaine and its stereoisomers was developed. In this study, the effect of organic modifier was also investigated. The separation was achieved using 1% sulfated cyclodextrin, 10 mmol L⁻¹ phosphate buffer, 10% methanol at pH 3. The method provides good reproducibility and easy application.

Keywords: Capillary electrophoresis Sulfated cyclodextrins Cocaine stereoisomers (−)-Cocaine HCl (+)-Cocaine base (−)-Pseudococaine (+)- Pseudococaine

Applications of capillary electrophoresis with laser-induced fluorescence for analysis of dGMP–BPDE adduct by Ana Paula Formenton-Catai; Emanuel Carrilho (pp. 138-141).

DNA adducts are thought to be crucial to the initiation of mutational and carcinogenic processes. Polycyclic aromatic hydrocarbons (PAHs) have been identified as one major source of carcinogenic risk since they can bind to DNA thus forming an adduct. Quantification of this adduct is important because it may correlate to the risk for cancer development. In this study, the adduct formed between 2′-deoxyguanosine 5′-monophosphate and benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE) was analyzed by capillary electrophoresis. Both capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MECC) modes with laser-induced fluorescence detection were used for the separation and analysis of DNA adducts. The exploration of capillary electrophoresis in several modes provided different separation mechanisms in which the stereochemical forms of the adduct could be separated. The best result obtained was using a coated fused-silica capillary in Tris–TAPS buffer, which provided high sensitivity with a detection limit of 2.5×10⁻⁹ mol L⁻¹. MECC separation of the BPDE adduct, although less sensitive, provided an efficient enantioselective separation option.

Keywords: BPDE DNA adduct Capillary electrophoresis Laser-induced fluorescence detection Biomarkers Carcinogenesis

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Analytical and Bioanalytical Chemistry (v.376, #1)