Analytica Chimica Acta (v.589, #1)

Contents (v-vi).

A DNA-based surface plasmon resonance biosensor for enrofloxacin was developed. Heating denatured DNA immobilized on the gold-coated glass surface was exploited. The immobilization was performed by a layer-by-layer co-deposition with a cationic polymer. The sensor performance was tested with real biological probes. Direct and simple determination of enrofloxacin in milk samples was demonstrated. The sensor response obeys Langmuir binding isotherm being almost linear until about 20 μg mL−1. The detection limit in milk samples was estimated to be 3 μg mL−1.
Keywords: Surface plasmon resonance; Nucleic acid; Biosensor; Enrofloxacin; Fluoroquinolones; Layer-by-layer deposition;

Polypyrrole-polyvinyl sulphonate film based disposable nucleic acid biosensor by Nirmal Prabhakar; Kavita Arora; Surinder P. Singh; Manoj K. Pandey; Harpal Singh; Bansi D. Malhotra (6-13).
Double stranded calf thymus deoxyribonucleic acid entrapped polypyrrole-polyvinyl sulphonate (dsCT-DNA-PPy-PVS) films fabricated onto indium-tin-oxide (ITO) coated glass plates have been used to detect organophosphates such as chlorpyrifos and malathion. These disposable dsCT-DNA-PPy-PVS/ITO bioelectrodes have been characterized using cyclic voltammetry, Fourier-transform-infra-red (FTIR) spectroscopy and atomic force microscopy (AFM), respectively. These biosensing electrodes have a response time of 30 s, are stable for about 5 months when stored in desiccated conditions at 25 °C and can be used to amperometrically detect chlorpyrifos (0.0016–0.025 ppm) and malathion (0.17–5.0), respectively. The additive effect of these pesticides on the amperometric response of the disposable dsCT-DNA-PPy-PVS/ITO bioelectrodes has also been investigated.
Keywords: Nucleic acid biosensor; Deoxyribose nucleic acid; Polypyrrole-polyvinyl sulphonate; Electrochemical entrapment; Chlorpyrifos; Malathion;

Screen-printing technology offers the possibility to produce a large number of sensors at low cost. Thus, due to their intrinsic characteristics and reproducibility, screen-printed electrodes can be used in the development of disposable electrochemical devices.In the present work, carbon-based screen-printed electrodes (SPCEs) have been used to develop a one-shot-measure biosensor for the detection of photosynthetic inhibitors in discrete samples. The measurement was based on the electrochemical evaluation of the activity of photosystem II (PSII), a protein complex present in photosynthetic organisms and involved in the photosynthesis. The biosensor was prepared by the modification of the working electrode of a SPCE, using thylakoid membranes extracted from spinach leaves. The modified sensors were then used as one-shot system to measure the presence of PSII activity inhibitors in discrete standard solutions. The coupling of the developed biosensor with a custom-made cell made it possible to perform tests using only 50 μL of total sample volume with a measurement time of 10 min. Inhibition curves were recorded for some photosynthetic inhibitors in a concentration range of 10−6 to 10−8  mol L−1. A reproducibility (relative standard deviation, R.S.D.%) of 10% was found and the calculated limit of detections (LODs) were in the nanomolar range.The effect of storage on sensitivity and reproducibility of a biosensor prepared by direct lyophilisation of thylakoid membranes on the electrode surface was also evaluated, confirming the possible use of the modified sensor up to one week after the preparation.Measurements on real samples were also reported, comparing the results with those obtained using a fluorescence-based commercial instrument for the analysis of photosynthetic inhibitors.
Keywords: Photosystem II; Screen-printed carbon-based electrodes; Herbicides; Photosynthetic inhibitors;

A novel flow injection potentiometric graphite coated ion-selective electrode for the low level determination of uranyl ion by Mojtaba Shamsipur; Farhang Mizani; Mir Fazlollah Mousavi; Naader Alizadeh; Kamal Alizadeh; Hossein Eshghi; Hassan Karami (22-32).
Solution studies on the binding properties of uranyl ion toward four different recently synthesized benzo-substituted macrocyclic diamides L1-L4 revealed the occurrence of a 1:1 complexation of the ligands with UO2 2+ ion, with a stability order of L2 > L1 > L4 > L3. Consequently, L2 was used as a suitable neutral ionophore for the preparation of novel polymeric membrane (PME) and coated graphite (CGE) UO2 2+-selective electrodes. The electrodes exhibit a Nernstian behavior for UO2 2+ ions over wide concentration ranges (1.0 × 10−6–1.0 × 10−1  M for PME and 1.0 × 10−7–1.0 × 10−1  M for CGE) and very low limits of detection (8.0 × 10−7  M for PME and 7.3 × 10−8  M for CGE). The proposed potentiometric sensors manifest advantages of fast response and, most importantly, good selectivity with respect to many alkali, alkaline earth, transition, and heavy metal ions. The potentiometric responses of the electrodes are independent of the pH of the test solution in the pH range 2.9–3.7. The CGE was used in flow injection potentiometry and resulted in well defined peaks for uranyl ions with stable baseline, excellent reproducibility and very high sampling rate of 170 injections per hour. The proposed FIP system was used for the determination of trace uranyl ions in real and synthetic samples.
Keywords: Uranyl ion-selective electrode; Macrocyclic diamides; Poly(vinyl chloride)-membrane; Coated graphite electrode; Flow injection poetntiometry;

PVC membrane electrode based on triheptyl dodecyl ammonium iodide for the selective determination of molybdate(VI) by Jianguo Wang; Lingling Wang; Yinghui Han; Jianbo Jia; Lili Jiang; Weiwei Yang; Qiaohua Sun; Hui Lv (33-38).
Novel polyvinyl chloride (PVC) membrane electrodes based on triheptyl dodecyl ammonium iodide have been developed. In the presence of 12.5 mM H2O2, these electrodes are capable of determining molybdate(VI) ion. The electrodes exhibit near-Nernstian responses over a wide concentration range (2.0 × 10−6 to 5.0 × 10−3M). The proposed electrodes demonstrate satisfying selectivity for molybdate(VI) ion in the presence of a wide variety of anions other than iodide, and can be used in the pH range 5.0–7.0. Moreover, the electrodes show an average response time of 2–3 min and can be used over a period of 2 months without any significant deviation being observed. In the light of our results, the response mechanism of the electrode is discussed and HMoO2(O2)2 is suggested as the response ion. The proposed electrode has been used to measure molybdenum in ore samples, and the results were in agreement with those obtained by means of ICP analysis.
Keywords: Molybdate; Hydrogen peroxide; Ion-selective electrode; Polyvinyl chloride membrane;

We have investigated the immersion-angle dependence of the series resonant-frequency shift, ΔF, of the quartz crystal microbalance, QCM, in a Newtonian liquid from the point of view of the supplied electric power level. In the low electric power levels, the immersion-angle dependence and the transition phenomenon of the ΔF are observed. However, when the higher electric power levels are supplied to the QCM, the region of the transition phenomenon of the ΔF decreases rapidly with an increase in the electric power level and disappears above 1.5 dBm. That is, above 1.5 dBm, the ΔF values have only the values of 90° immersion angle in all immersion angles. We suggest that the electric power is very important factor for the ΔF in a liquid.
Keywords: QCM; Immersion angle; Electric power level;

Preparation for nitrocellulose membrane-poly (vinyl alcohol)-ionic imprinting and its application to determine trace copper by room temperature phosphorimetry by Zhi-Ming Li; Jia-Ming Liu; Zhen-Bo Liu; Qin-Ying Liu; Xuan Lin; Fei-Ming Li; Min-Lan Yang; Guo-Hui Zhu; Xiao-Mei Huang (44-50).
Nitrocellulose membrane-poly (vinyl alcohol)-ionic imprinting (NCM-PVA-I-I) was prepared using Cu2+ as template. The cavity in NCM-PVA-I-I matched Cu2+ very well and the selectivity was high. Cu2+ entered the cavity and then could form ionic association ([Cu2+]·[(Fin)2]) with the anion of fluorescein (Fin) outside the cavity by electrostatic effect. [Cu2+]·[(Fin)2] could emit strong and stable room temperature phosphorescence on NCM-PVA-I-I. Its ΔI p was proportional to the content of Cu2+. Based on the above facts, a new method for the determination of trace copper by solid substrate-room temperature phosphorimetry (NCM-PVA-I-I-SS-RTP, SS-RTP is the abbreviation of solid substrate-room temperature phosphorimetry) using NCM-PVA-I-I technique has been established. The linear range of this method was 2.00–144.00 fg Cu2+ spot−1 (sample volume: 0.40 μL spot−1, corresponding concentration: 5.00–360.00 pg mL−1), and the detection limit calculated by 3Sb/k was 0.43 fg Cu2+ spot−1 (corresponding concentration: 1.1 × 10−12  g mL−1, n  = 11). Samples containing 2.00 and 144.00 fg Cu2+spot−1 were measured, respectively, for seven times and R.S.D.s were 3.5% and 4.7%. NCM-PVA-I-I-SS-RTP could combine very well the characteristics of both the high sensitivity of SS-RTP and the high match and selectivity of NCM-PVA-I-I, and it was rapid, accurate, sensitive and with good repeatability. It has been successfully applied to determine trace copper in human hair and tea samples.
Keywords: Copper; Nitrocellulose membrane-poly (vinyl alcohol)-ionic imprinting technique; Solid substrate-room temperature phosphorimetry;

Direct screening of tetracyclines in water and bovine milk using room temperature phosphorescence detection by J.M. Traviesa-Alvarez; J.M. Costa-Fernández; R. Pereiro; A. Sanz-Medel (51-58).
A fast and simple flow-through optosensor was designed and characterized for the direct screening of four tetracycline (TCC) antibiotics (tetracycline, oxytetracycline, chlortetracycline and doxycycline) in water and bovine milk samples. The proposed optosensor provides rapid binary yes/no overall responses, being appropriate for the screening of this family of antibiotics above or below a pre-set concentration threshold.The experimental set-up is based on a flow-injection manifold coupled on-line to a phosphorescence detector. Aliquots of the samples are pretreated with Eu(III) to form room temperature phosphorescent metal chelates and injected in the flow manifold. Those chelates are then on-line retained on a conventional flow-cell (packed with polymeric Amberlite XAD-4 particles) which is placed inside the cell holder of the phosphorimeter. After the emission is registered, the antibiotic–metal complexes are eluted from the packed resin with 1 M HCl (for milk samples a second regeneration step, using methanol, should be performed). A sample throughput of about 20 samples per hour was obtained. Optimum experimental conditions include a pH 9, a Eu(III) concentration of 2 × 10−4  M and 8 mM sodium sulphite as chemical deoxygenant. The phosphorescence emitted by the europium–TCC complexes was measured at 394 and 617 nm for excitation and emission wavelengths, respectively.The unreliability region, given by the probability of false positives and false negatives, respectively (set at 5% in both cases) was in the range between 0.2 and 11.6 nМ for detection of tetracyclines in water samples (at a cut-off level of 4 nM) and in the range between 165 and 238 nM for detection of tetracyclines in milk (cut-off level fixed at the normative EU level of 200 nM). Finally, the applicability of the proposed screening optosensor was tested for the reliable control of tetracyclines in contaminated and uncontaminated water and milk samples.
Keywords: Screening; Tetracyclines; Optosensing; Room temperature phosphorescence;

This study establishes a new method to analyze the radical scavenging activity of antioxidants based on the luminol-H2O2-Co(II)/EDTA chemiluminescence and flow injection analysis. The method is based on the catalytic oxidation of hydrogen peroxide by Co(II)/EDTA complex, forming a free radical flux that can produce a stable chemiluminescence signal which is attenuated in the presence of antioxidants. A properly designed FIA manifold and the appropriate regulation of the chemiluminescence-reagent mixture enabled the establishment of a reaction-sensitive analytical procedure that minimizes oxidant-antioxidant interactions while favors the inhibition effect of antioxidants on the free radicals flux. In that manner, the uncontrolled experimental variability induced by side-reactions occurring antagonistically is reduced. The method was examined in-vitro for the continuous monitoring of the generation of oxygen-derived free radicals and antioxidants, which is closer to in-vivo conditions, with three common antioxidants (ascorbic acid, glutathione and uric acid). All three antioxidants were found to inhibit the luminescent signal with strict logarithmic linear mode, yielding calibration curves rectilinear in the range of 5 × 10−8–5 × 10−5  mol L−1 and detection limits at the 10−8  mol L−1 levels. The F-statistic was employed to assess the ability of the method to detect differences in the activity of the examined antioxidants. The results suggest that the proposed method can be used efficiently for the detection of free radical activity in real samples.
Keywords: Cobalt; Chemiluminescence; Antioxidant; Flow injection; Free radical;

Analysis of antioxidants using a capillary electrophoresis with chemiluminescence detection system by Kazuhiko Tsukagoshi; Takehito Taniguchi; Riichiro Nakajima (66-70).
We developed a capillary electrophoresis with chemiluminescence detection system using 2-methyl-6-p-methoxyphenylethynylimidazopyrazinone as a chemiluminescence reagent for determination of antioxidants of superoxide anions. 2-Methyl-6-p-methoxyphenylethynylimidazopyrazinone reacted with superoxide anions generated through the reaction of hypoxanthine and xanthine oxidase, and then emitted chemiluminescence. Suppression of the chemiluminescence in the presence of antioxidants for superoxide anions was introduced as a detection principle for antioxidants into the capillary electrophoresis with chemiluminescence detection system. After optimizing the analytical conditions, various antioxidants, such as superoxide dismutase, nitroblue tetrazolium, ascorbic acid, and catechin, were subjected to the present system. They gave negative peaks due to the quenching effect; the detection limits of superoxide dismutase, nitroblue tetrazolium, ascorbic acid, and catechin were 1, 100, 100, and 10 μM, respectively (S/N = 2). A model sample consisting of superoxide dismutase and nitroblue tetrazolium was satisfactorily separated and detected within ca. 10 min. We also applied the present system to analysis of catechin in green tea as a real sample.
Keywords: Capillary electrophoresis; Chemiluminescence; Antioxidants; Superoxide anion; Catechin;

Advantageous features (enhanced sensitivity and low baseline noise) of the multiplex measuring procedure, the Hadamard transform capillary electrophoresis (HT-CE), are experimentally demonstrated and critically discussed. To perform a perfect multiplex experiment in CE, sample species need to be dissolved in the background electrolyte medium and have very low concentration. The mismatch of electric conductivity resulting from a sample dissolved in water or in a separation buffer diluted with water will lead to sample stacking and corrupting the anticipated outcome. The multiplex measurements were carried out with benzyltriethylammonium bromide, resorcinol and 3,5-dihydroxybenzoic acid in the phosphate buffer, 511 sample/buffer injections were performed into the capillary according to the pseudorandom binary sequence. The averaged electropherogram of the single injection was calculated from the detection signal with the aid of the Fourier transform. The results illustrate the detrimental effect of sample matrix dilution with water and the effect of increased initial sample concentration on the multiplex measurement in CE. Multiplex advantage, in theory possible in the HT-CE, can be obtained at low concentration levels feasible with laser induced fluorescence and optically gated sampling. To achieve successful multiplex measurements with the UV detector, the single injection signal should be approximately at the baseline noise level.
Keywords: Multiplex measurement; Multiple sample injection; Hadamard transform capillary electrophoresis;

We synthesized a chromatographic packing material that has a non-covalently attached dihexadecyl phosphate (DHP) bilayer membrane structure on a CA08S, a nonporous-type cationic polymer bead with a diameter ranging from 11 to 14 μm. Confocal fluorescence microscopic and differential scanning calorimetric analyses of the DHP-CA08S complex revealed that the DHP bilayer membrane structures were formed on the surface of the CA08S polymer beads. When the functionality of the DHP-CA08S complex was evaluated in the ion-exchange HPLC of proteins, the retention behavior of the proteins on the DHP-CA08S complex column totally mirrored the anionic property of the DHP bilayer membrane surface, not the cationic property of the CA08S bead. Methylene blue (MB) was eluted from the DHP-CA08S complex column in the isocratic elution mode, but not at all from a CK08S column, a styrene-divinylbenzene based cation-exchange polymer. When the column temperature was elevated from 50 to 60 °C, the peak shape of MB on the DHP-CA08S complex column became fairly sharp without a change in its peak area, which mirrored the characteristic phase transition of the DHP bilayer membrane formed on the DHP-CA08S complex.
Keywords: Bilayer membrane; Immobilization; Ionic polymer; Lipid vesicle; Microbead;

Simple and rapid methods for the fabrication of polymeric and glass chips for using in analytical chemistry by Mohammad H. Sorouraddin; Mohammad Amjadi; Mohammad Safi-Shalamzari (84-88).
This paper describes simple and rapid methods for the fabrication of glass and polymeric chips for routine analytical applications. The methods are easily interfaced to the general laboratory environment and do not require special clean room facilities or expensive instruments. Glass microchips were fabricated by etching with HF solution. Microfluidic channels were designed with CAD program and transferred onto a sheet of commercial polymeric self-adhesive (PSA) film by a cutter plotter. The PSA film was used as a mask for etching process. The etching rate was about 7 μm min−1. A cover glass plate was sealed on the top of etched substrate by using polycellulose (cellophane). Polymeric microchips were fabricated by sawing with a jigsaw. Commercial polycarbonate (PC) was used as a substrate and two iron sheets were used as leader masks. While this restricts us to the fabrication of straight channels, it is however, much faster and less complicated than the other methods. The chip comprised three polymeric plates and the channels were created in the middle plate. Thermal bonding was used to bond three layers of the microfluidic chip. With this method, we could achieve simple channels with the width of about 200 μm. The channel depth depends on the polymeric plate thickness. Fabricated channels were accurate without any sinuosity or sideshow.
Keywords: Microfabrication; Wet etching; Polymeric chips; Glass chips;

An electronic nose and an UV-Vis spectrophotometer, in combination with multivariate analysis, have been used to verify the geographical origin of extra virgin olive oils. Forty-six oil samples from three different areas of Liguria were included in this analysis.Initially, the data obtained from the two instruments were analysed separately. Then, the potential of the synergy between these two technologies for testing food authenticity and quality was investigated.Application of Linear Discriminant Analysis, after feature selection, was sufficient to differentiate the three geographical denominations of Liguria (“Riviera dei Fiori”, “Riviera del Ponente Savonese” and “Riviera di Levante”), obtaining 100% success in classification and close to 100% in prediction. The models built using SIMCA as a class-modelling tool, were not so effective, but confirmed that the results improve using the synergy between different analytical techniques.This paper shows that objective instrumental data related to two important organoleptic features such as oil colour and aroma, supply complementary information.
Keywords: Electronic nose; UV-Vis spectrophotometer; Chemometrics; Olive oils; Characterisation; Synergy;

This work can be seen as an attempt to develop an analytical procedure in the context of quality control and authenticity assessment of typical food.To this aim, head-space mass spectrometry (HS-MS) coupled with multivariate data analysis, is proposed as a fast technique for furnishing a clear visualization and a suitable interpretation of the ageing process of ‘Aceto Balsamico Tradizionale di Modena’ (ABTM) and, for classifying products of different age.Considering the complexity of this food matrix, due to its traditional making procedure, the obtained instrumental data have first been analysed by parallel factor analysis (PARAFAC), an extension of principal component analysis to higher order arrays, in order to visualise the ‘natural’ grouping of vinegar samples and to inspect producers similarity/dissimilarity. On the basis of the PARAFAC results a reasonable class partition with respect to ageing was accomplished and both linear discriminant analysis (LDA) and soft independent modelling of class analogy (SIMCA) were applied as classification tools. Furthermore, it has been shown that discrimination on age basis can be improved by using feature selection in the wavelet domain through WPTER algorithm.
Keywords: Head-space mass spectrometry; Vinegar; Parallel Factor Analysis; Classification; Authentication; Wavelet transform;

Precise measurement of Fe isotopes in marine samples by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) by Jeroen de Jong; Véronique Schoemann; Jean-Louis Tison; Sylvie Becquevort; Florence Masson; Delphine Lannuzel; Jérôme Petit; Lei Chou; Dominique Weis; Nadine Mattielli (105-119).
A novel analytical technique for isotopic analysis of dissolved and particulate iron (Fe) from various marine environments is presented in this paper. It combines coprecipitation of dissolved Fe (DFe) samples with Mg(OH)2, and acid digestion of particulate Fe (PFe) samples with double pass chromatographic separation. Isotopic data were obtained using a Nu Plasma MC-ICP-MS in dry plasma mode, applying a combination of standard-sample bracketing and external normalization by Cu doping. Argon interferences were determined prior to each analysis and automatically subtracted during analysis. Sample size can be varied between 200 and 600 ng of Fe per measurement and total procedural blanks are better than 10 ng of Fe. Typical external precision of replicate analyses (1S.D.) is ±0.07‰ on δ56Fe and ±0.09‰ on δ57Fe while typical internal precision of a measurement (1S.E.) is ±0.03‰ on δ56Fe and ±0.04‰ on δ57Fe. Accuracy and precision were assured by the analysis of reference material IRMM-014, an in-house pure Fe standard, an in-house rock standard, as well as by inter-laboratory comparison using a hematite standard from ETH (Zürich). The lowest amount of Fe (200 ng) at which a reliable isotopic measurement could still be performed corresponds to a DFe or PFe concentration of ∼2 nmol L−1 for a 2 L sample size. To show the versatility of the method, results are presented from contrasting environments characterized by a wide range of Fe concentrations as well as varying salt content: the Scheldt estuary, the North Sea, and Antarctic pack ice. The range of DFe and PFe concentrations encountered in this investigation falls between 2 and 2000 nmol L−1 Fe. The distinct isotopic compositions detected in these environments cover the whole range reported in previous studies of natural Fe isotopic fractionation in the marine environment, i.e. δ56Fe varies between −3.5‰ and +1.5‰. The largest fractionations were observed in environments characterized by redox changes and/or strong Fe cycling. This demonstrates the potential use of Fe isotopes as a tool to trace marine biogeochemical processes involving Fe.
Keywords: Fe isotopes; MC-ICP-MS; Seawater; Sea ice; Scheldt estuary; North Sea; Antarctica;

Volatiles emission patterns of different plant organs and pollen of Citrus limon by Guido Flamini; Marianna Tebano; Pier Luigi Cioni (120-124).
The volatiles emitted in vivo by different plant parts of Citrus limon (Rutaceae) have been identified by mean of head space-solid phase micro extraction (HS-SPME) and gas chromatography coupled with mass spectrometry (GC–MS) analyses. In particular, the profiles of flower buds, mature flowers, petals, stamens, gynaecium, pericarp of unripe and ripe fruits, young and adult leaves and pollen have been examined. Furthermore, the essential oil obtained from expression of ripe pericarp was studied. Volatiles were produced in distinctive amounts by the different plant organs, creating an interesting contrast, particularly within the flower parts: the highest amount of limonene (62.5%) was emitted by gynaecium, followed by stamens (22.9%) and petals (3.1%). Pollen did not produce limonene at all. The same compound is contained in higher amounts in the young leaves than in old ones (65.3% versus 30.1%). A possible defensive role of limonene and other volatiles, mainly terpene aldehydes, produced by young leaves has been hypothesized.
Keywords: Citrus limon; Rutaceae; Volatiles; Head space-solid phase micro extraction; Plant organs; Pollen;

Concentrations of pharmaceuticals and personal care products (PPCPs) in natural solids remain largely unknown. Contributing to this, is a lack of methods permitting the simultaneous detection of the diverse, low-level contaminants present in these complex matrices. We have developed a microwave-assisted solvent extraction (MASE)-based method targeting seven diverse PPCPs (caffeine, 17β-estradiol, ibuprofen, ketoprofen, musk ketone, naproxen, and triclosan) and a molecular marker for fecal waste (epicoprostanol). The method consisted of optimizing the following variables: derivatization of the polar target analytes, silica gel open column clean-up, and gas chromatographic–mass spectrometric (GC–MS) analysis of sample extracts for analysis and detection of the compounds noted above. Testing of the method on spiked soil allowed for 89.6 ± 2.89% recovery of three target compounds and 25.0 ± 1.93% recovery of five of the compounds. Although the latter recoveries were low, the precision across all recoveries was high, suggesting good reproducibility in application of the method. Furthermore, we suspect that matrix effects are likely responsible for the lower recoveries. Techniques with the exclusive incorporation of organic solvents were found inapplicable in the study of a pharmaceutical salt, diphenhydramine HCl. Application of the developed method to sediment collected directly downstream of the effluent pipe of a wastewater treatment plant allowed detection of ibuprofen, naproxen, ketoprofen, and epicoprostanol at ng–μg per gram dry weight concentrations. The observation of acidic pharmaceuticals, previously believed to exhibit insignificant sorption to solid matrices, in the tested sediment samples, coupled with application of biosolids for agricultural purposes, demonstrates the need for expanded investigation of PPCP contamination of natural solid matrices.
Keywords: PPCPs; MASE; Biosolids;

Trihalogenated anisoles (THAs) that have been identified at low concentration levels (ng L−1) in drinking water are suspected of causing odor episodes, which are a frequent source of complaint by consumers. Henry's law constant (K H) is an important parameter in controlling the diffusion of organic compounds from the water to the vapor-phase, so its evaluation is of significance in the study of odor events. In this paper, the K H of a wide range of trihalogenated anisoles – in its dimensionless form K ′ H – were calculated at two temperatures, 45 and 22 °C using equilibration partitioning in a closed system and headspace microextraction (EPICS-SPME). Two methodological approaches, Ramachandran and Dewulf, were used for the assessment of the Henry's law constant. Nevertheless, to apply these methods to THAs, a relatively narrow headspace/water volume ratio range (80/1–8/1) is required. At these conditions, a linearity (r 2) using Ramachandran's theoretical relationship from 0.9276 to 0.9989 was obtained and the variability (R.S.D.%) when Dewulf's theoretical relationship was employed was lower than 20% (n  = 5).
Keywords: Air–water partitioning; Henry's constant; Mixed trihalogenated anisoles; Equilibration partitioning in a closed system; Solid-phase microextraction method;

Spectrophotometric determination of aqueous cyanide using a revised phenolphthalin method by David Cacace; Heidi Ashbaugh; Naomi Kouri; Sara Bledsoe; Sean Lancaster; Stuart Chalk (137-141).
This paper focuses on a revision of the phenolphthalin method for cyanide analysis, with the intent of producing a robust and sensitive spectrophotometric method. Limitations of the phenolphthalin chemistry were overcome by the addition of EDTA to the reagent. The revised reagent was found to have suitably fast kinetics, a linear dynamic range of 0.01–3.0 ppm cyanide, and a detection limit of 5 ppb. The method was tested for interferences and applied to the determination of cyanide in environmental waters.
Keywords: Cyanide determination; Copper(II)EDTA binuclear complex; Phenolphthalin; Environmental analysis;

Development of a competitive immunoassay for efavirenz: Hapten design and validation studies by Camille Roucairol; Stéphane Azoulay; Marie-Claire Nevers; Christophe Créminon; Jacques Grassi; Alain Burger; Danièle Duval (142-149).
The reverse transcriptase inhibitor efavirenz (EFV) is widely used in human immunodefiency virus (HIV) therapy. Knowledge of the plasma and intracellular concentrations of the drug is of prime importance to get further insight into EFV action in vivo and would be useful for therapeutic drug monitoring (TDM). The aim of this study was to develop a sensitive and specific competitive enzyme immunoassay (EIA) for EFV in biological fluids. Two haptens that differed by the position of the linker were synthesized using two different ways and coupled to BSA. Anti-EFV polyclonal antibodies (pAb) were raised in rabbits using the corresponding immunogens. By comparing results obtained with EIA study with those observed with high-performance liquid chromatography (HPLC) we have shown that the position of the linker appears to be crucial for the specificity of the pAb. EIA was then developed in microtitration plates using the most specific pAb. The assay was performed on a minimum of 30 μL of plasma. It showed good precision and efficiency as well as good cross-validation with HPLC. The lowest limit of quantification (LLOQ) was 150 pg mL−1, i.e., a value at least 10 times lower than those currently achieved using previously described techniques. This EIA should be useful in the clinical laboratory for monitoring patients during antiretroviral therapy especially young children as well as for measuring EFV in intracellular studies requiring lower amounts of biological material.
Keywords: Efavirenz immunoassay; Human immunodeficiency virus; Therapeutic drug monitoring; Hapten design;

Prediction of ozone tropospheric degradation rate constants by projection pursuit regression by Yueying Ren; Huanxiang Liu; Xiaojun Yao; Mancang Liu (150-158).
Quantitative structure–property relationship (QSPR) models were developed to predict degradation rate constants of ozone tropospheric and to study the degradation reactivity mechanism of 116 diverse compounds. DUPLEX algorithm was utilized to design the training and test sets. Seven molecular descriptors selected by the heuristic method (HM) were used as inputs to perform multiple linear regression (MLR), support vector machine (SVM) and projection pursuit regression (PPR) studies. The PPR model performs best both in the fitness and in the prediction capacity. For the test set, it gave a predictive correlation coefficient (R) of 0.955, root mean square error (RMSE) of 1.041 and absolute average relative deviation (AARD, %) of 4.663, respectively. The results proved that PPR is a useful tool that can be used to solve the nonlinear problems in QSPR. In addition, methods used in this paper are simple, practical and effective for chemists to predict the ozone degradation rate constants of compounds in troposphere.
Keywords: Quantitative structure–property relationship; Ozone tropospheric degradation rate constants; Heuristic method; Support vector machine; Projection pursuit regression;