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Analytical and Bioanalytical Chemistry (v.382, #4)

Young Swedish physicist wins first ABC Best Paper Award by Christina E. Dyllick (pp. 853-854).

Instruction in bioanalytical chemistry by C. K. Larive (pp. 855-856).

Getting the message across—writing an effective curriculum vita by John Fetzer (pp. 857-858).

Alan Cooper: Biophysical chemistry by Alfredo Sanz-Medel (pp. 859-860).

M.J. Adams: Chemometrics in Analytical Spectroscopy, 2nd edition by Jürgen W. Einax (pp. 861-862).

T. Nelis and R. Payling: Glow discharge optical-emission spectroscopy: a practical guide by Nerea Bordel (pp. 863-864).

Microreactors for drug discovery: the importance of integrating chemical synthesis with real-time analytical detection by Paul Watts (pp. 865-867).

Hyperspectral integrated computational imaging by Lisa A Cassis; Aaron Urbas; Robert A Lodder (pp. 868-872).

Chirally-functionalized monolithic materials for stereoselective capillary electrochromatography by Michael Lämmerhofer (pp. 873-877).

Miniaturisation and automation of metal fractionation schemes applied to environmental solid samples by sequential injection microcolumn extraction procedures by Manuel Miró; Elo Harald Hansen (pp. 878-880).

Chemical vapor generation: are further advances yet possible? by R. E. Sturgeon; X. Guo; Z. Mester (pp. 881-883).

Gold nanoparticle-based electrochemical biosensors by P. Yáñez-Sedeño; J. M. Pingarrón (pp. 884-886).

Plasma time-of-flight mass spectrometry as a detector for short transient signals in elemental analysis by Nicolas H. Bings (pp. 887-890).

Interactions of electric fields with fluids by Nicolas G. Green (pp. 891-893).

Enhancement of steroid receptor-mediated transcription for the development of highly responsive bioassays by Philippe Willemsen; Marie-Louise Scippo; Guy Maghuin-Rogister; Joseph A. Martial; Marc Muller (pp. 894-905).

We have previously generated several transformed human mammary cell lines for the detection of steroid receptor-mediated activities and used these cell lines to detect and characterize steroid hormone (ant)agonistic compounds. In this report, we describe the specific optimization procedures used to enhance receptor-mediated transcription through the human glucocorticoid, progesterone and androgen receptors, respectively. Sodium arsenite-induced chemical stress leads to a substantial and specific increase in the glucocorticoid receptor-mediated transcription, resulting in maximal stimulations of more than 2000-fold by the agonist dexamethasone. Similarly, a combined treatment with forskolin (an activator of adenylate cyclase) and trichostatin A (an inhibitor of histone deacetylases) leads to a synergistic enhancement of progesterone or androgen stimulation, resulting in a maximal induction of more than 200-fold or about 100-fold, respectively. The enhanced responses to specific steroids are mediated by the corresponding nuclear receptor. We show that by using these enhanced transcriptional stimulation protocols, it is possible to detect lower amounts of steroid hormones without substantially affecting the relative biological activities of various agonists. Finally, the application of these enhanced reporter cell assays to real biological samples from meat-producing animals is evaluated, and some validation parameters are presented.

Keywords: Steroid hormones; Steroid receptors; Bioassay; hsp; PKA; PKC

Within the cell: analytical techniques for subcellular analysis by Karen J. Olson; Hossein Ahmadzadeh; Edgar A. Arriaga (pp. 906-917).

This review covers recent developments in the preparation, manipulation, and analyses of subcellular environments. In particular, it highlights approaches for (1) separation and detection of individual organelles, (2) preparation of ultra-pure organelle fractions, and (3) utilization of novel labeling strategies. These approaches, based on innovative technologies such as microfluidics, immunoisolation, mass spectrometry and electrophoresis, suggest that subcellular analyses will soon become as commonplace as single cell and bulk cellular assays.

Keywords: Subcellular analysis; Organelle; Electrophoresis; Flow cytometry

Fiber-optic nanosensors for single-cell monitoring by Tuan Vo-Dinh; Paul Kasili (pp. 918-925).

This article is an overview of the fabrication, operating principles, and applications of fiber-optic nanobiosensors with the capability of in-vivo analysis at the single-cell level. Recently, the cross-disciplinary integration of nanotechnology, biology, and photonics has been revolutionizing important areas in molecular biology, especially diagnostics and therapy at the molecular and cellular level. Fiber-optic nanobiosensors are a unique class of biosensor that enable analytical measurements in individual living cells and the probing of individual chemical species in specific locations within a cell. This article provides a review of the research performed in our laboratory and discusses the usefulness and potential of this nanotechnology-based biosensor system in biological research and its applications to biomonitoring of individual cells.

Keywords: Fiber-optic nanosensor; Nanobiosensor; Nanotechnology; Biosensor; Single cells; Apoptosis

Metal-enhanced fluorescence using anisotropic silver nanostructures: critical progress to date by Kadir Aslan; Joseph R. Lakowicz; Chris D. Geddes (pp. 926-933).

In this critical and timely review, the effects of anisotropic silver nanostructures on the emission intensity and photostability of a key fluorophore that is frequently used in many biological assays is examined. The silver nanostructures consist of triangular, rod-like, and fractal-like nanoparticles of silver deposited on conventional glass substrates. The close proximity to silver nanostructures results in greater intensity and photostability of the fluorophore than for fluorophores solely deposited on glass substrates. These new anisotropic silver nanostructure-coated surfaces show much more favorable effects than silver island films or silver colloid-coated substrates. Subsequently, the use of metal-enhanced fluorescence (MEF) for biosensing applications is discussed.

Keywords: Silver nanotriangles; Silver nanorods; Anisotropic nanoparticles; Metal-enhanced fluorescence; Radiative decay engineering; Increased excitation rate

Critical review of the application of liquid chromatography/mass spectrometry to the determination of pesticide residues in biological samples by F. Hernández; J. V. Sancho; O. J. Pozo (pp. 934-946).

A critical review is made on the use of hyphenated liquid chromatography/mass spectrometry (LC–MS) for the identification and quantification of pesticides and their metabolites in human biosamples (whole blood, plasma, serum and urine). The first applications of LC–MS in this field began in the early 1990s. Since then, increasing interest has been shown in applying this powerful technique, with most applications dealing with the determination of a variety of chemically diverse metabolites in urine. The use of different LC–MS interfaces and mass spectral detection modes are discussed. Special attention is given to tandem mass spectrometry (MS/MS) due to its inherent advantages of increased sensitivity and selectivity, as well as its advantages for identification and confirmation of analytes in samples. Quantification can be severely affected by matrix effects, the most common being inhibition of the ionisation of analytes in the mass spectrometer, which leads to unacceptable errors if no correction is made. Different approaches can be employed to minimise this undesirable matrix effect, the preferred being the use of labelled internal standards (when available) in isotope dilution methods or the application of an efficient clean-up, performed off-line or automated on-line. Adequate criteria for confirming the identities of residues detected are required in order to avoid false positives. The criterion most commonly used with a triple quadrupole instrument is the monitoring of two MS/MS transitions together with the ion abundance ratio. TOF mass analysers are seldom used in pesticide residue analysis despite their improved resolution and mass accuracy characteristics, which makes them very suitable for confirmation purposes. The main reasons for the relative unpopularity of TOF MS in residue analysis are its limited sensitivity and its high acquisition cost. In this paper, we present a critical assessment on current techniques, trends and future developments, and give illustrative examples to point out the main characteristics of LC–MS for pesticide residue analysis in biological fluids.

Keywords: Pesticide residues; Metabolites; Liquid chromatography; Mass spectrometry; Review; Human urine; Serum; Blood

Optical interrogation of molecularly imprinted polymers and development of MIP sensors: a review by Olivier Y. F. Henry; David C. Cullen; Sergey A. Piletsky (pp. 947-956).

This article reviews the progress and developments achieved in the past five years (2000–2005) in the application of optical analytical techniques to the evaluation of molecularly imprinted polymer (MIP) characteristics. The MIP binding efficiency, recognition processes and selectivity have been intensively studied by optical means due to the general high sensitivity and simplicity of the utilisation of optical techniques. In addition, recent progress in the covalent linkage of MIPs to optical transducers has allowed for the realisation of highly efficient and robust optical MIP-based molecular recognition sensors. The review provides insight into the various approaches to the optical interrogation of MIPs, and is organised according to the type of optical technique employed (fluorescence, UV/Vis and infrared spectroscopy, surface plasmon resonance, chemiluminescence, refractive interference spectroscopy and Raman scattering) and the detailed strategies applied. The review also covers the recent progress achieved in the area of optical sensors based on MIPs.

Keywords: Optical; Sensors; Molecular imprinted polymer; Spectroscopy; Chemiluminescence; Surface plasmon resonance; Molecular recognition

Current mass spectrometry strategies for selenium speciation in dietary sources of high-selenium by Heidi Goenaga Infante; Ruth Hearn; Tim Catterick (pp. 957-967).

This document reviews the most relevant mass spectrometry approaches to selenium (Se) speciation in high-Se food supplements in terms of qualitative and quantitative Se speciation and Se-containing species identification, with special reference to high-Se yeast, garlic, onions and Brazil nuts. Important topics such as complexity of Se speciation in these materials and the importance of combining Se-specific detection and molecule-specific determination of the particular species of this element in parallel with chromatography, to understand their nutritional role and cancer preventive properties are critically discussed throughout. The versatility and potential of mass spectrometric detection in this field are clearly demonstrated. Although great advances have been achieved, further developments are required, especially if “speciated”certified reference materials (CRMs) are to be produced for validation of measurements of target Se-containing species in Se-food supplements.

Keywords: Selenium speciation analysis; Se-enriched food supplements; Mass spectrometry strategies; High Se-yeast; Cancer preventive properties

Semicarbazide: occurrence in food products and state-of-the-art in analytical methods used for its determination by Maria Beatriz de la Calle; Elke Anklam (pp. 968-977).

This review provides an overview of the information currently available about the presence of semicarbazide (SEM) in food. Likely sources of SEM in food matrices are summarised and discussed. Detailed information is given about the analytical methods used to determine SEM; features and drawbacks associated with them are carefully evaluated. Performance criteria characterising the analytical methods discussed are also given.

Keywords: Semicarbazide; Food; Nitrofurazone; Azodicarbonamide; HPLC-MS/MS

Effluent analysis in analytical chemistry: an overview by F. Sánchez Rojas; C. Bosch Ojeda (pp. 978-991).

This review summarizes and discusses effluent analysis, focusing on the methods and techniques that have been most frequently described in the literature since 1975. The methods are classified into four main categories: (1) physical and chemical properties; (2) inorganic metals analysis; (3) inorganic non-metallic analysis; (4) organic analysis.

Keywords: Effluent analysis; Inorganic and organic compounds; Environmental monitoring

Laser-induced fluorescence microscopic system using an optical parametric oscillator for tunable detection in microchip analysis by Momoko Kumemura; Tamao Odake; Takashi Korenaga (pp. 992-995).

A laser-induced fluorescence microscopic system based on optical parametric oscillation has been constructed as a tunable detector for microchip analysis. The detection limit of sulforhodamine B (Ex. 520 nm, Em. 570 nm) was 0.2 μmol, which was approximately eight orders of magnitude better than with a conventional fluorophotometer. The system was applied to the determination of fluorescence-labeled DNA (Ex. 494 nm, Em. 519 nm) in a microchannel and the detection limit reached a single molecule. These results showed the feasibility of this system as a highly sensitive and tunable fluorescence detector for microchip analysis.

Keywords: Optical parametric oscillation; Microchip; Laser-induced fluorescence; Microscopy; Sulforhodamine B; Tunable

Microgravimetric flow analysis of nucleic acid based on adsorption of nanoparticle-bioconjugate by Z.-H. Mo; Y.-L. Liang; H.-L. Wang; F.-W. Liu; Y.-X. Xue (pp. 996-1000).

A novel nanoparticle-bioconjugate has been prepared by specific hybridization of the target with complementary thiol-labeled and nanoparticle-labeled probes. The rapid adsorption of the nanoparticle-bioconjugate onto a gold surface via a thiol-gold reaction was monitored in real-time using a quartz crystal microbalance, and used to perform microgravimetric flow analysis of nucleic acid for the first time. This innovative assay is highly reproducible and sensitive, and shows great promise for clinical applications.

Keywords: Nanoparticle; Bioconjugate; Microgravimetry; DNA detection

ICP-MS multielemental determination of metals potentially released from dental implants and articular prostheses in human biological fluids by Alejandro Sarmiento-González; Juan Manuel Marchante-Gayón; José María Tejerina-Lobo; José Paz-Jiménez; Alfredo Sanz-Medel (pp. 1001-1009).

A sector field high-resolution (HR)-ICP-MS and an octapole reaction system (ORS)-ICP-MS have been compared for the simultaneous determination of traces of metals (Ti, V, Cr, Co, Ni, and Mo) released from dental implants and articular prostheses in human biological fluids. Optimum sample treatments were evaluated to minimize matrix effects in urine and whole blood. Urine samples were diluted tenfold with ultrapure water, whereas whole blood samples were digested with high-purity nitric acid and hydrogen peroxide and finally diluted tenfold with ultrapure water. In both matrices, internal standardization (Ga and Y) was employed to avoid potential matrix interferences and ICP-MS signal drift. Spectral interferences arising from the plasma gases or the major components of urine and whole blood were identified by (HR)-ICP-MS at 3,000 resolving power. The capabilities of (HR)-ICP-MS and (ORS)-ICP-MS for the removal of such spectral interferences were evaluated and compared. Results indicate that polyatomic interferences, which hamper the determination of such metallic elements in these biological samples, could be overcome by using a resolving power of 3,000. Using (ORS)-ICP-MS, all those elements could be quantified except Ti and V (due to the polyatomic ions ³¹P¹⁶O and ³⁵Cl¹⁶O, respectively). The accuracy of the proposed methodologies by (HR)- and (ORS)-ICP-MS was checked against two reference materials. Good agreement between the given values and the concentrations obtained for all the analytes under scrutiny was found except for Ti and V when analyzed by (ORS)-ICP-MS.

Keywords: Whole blood; Urine; High-resolution ICP-MS; Collision/reaction cell ICP-MS; Matrix interferences; Polyatomic interferences

Vascular endothelial growth factor as a biomarker for the early detection of cancer using a whole cell-based biosensor by Kimberly M. L. May; Adam Vogt; Leonidas G. Bachas; Kimberly W. Anderson (pp. 1010-1016).

Vascular endothelial growth factor (VEGF) is a cytokine and endothelial cell (EC) mitogen that has been studied for its role in angiogenesis of malignant tumors. Elevated quantities of VEGF in the serum and plasma of patients have been correlated with the presence of cancer and metastasis. Since VEGF induces hyperpermeability of EC monolayers, this protein can be detected in vitro with a whole cell-based biosensor. This biosensor consists of a confluent monolayer of human umbilical vein endothelial cells (HUVECs) attached to a cellulose triacetate (CTA) membrane of an ion-selective electrode (ISE). Previous studies regarding this biosensor have shown that when the biosensor was exposed to a model toxin, such as histamine, the response of the biosensor served as an indirect measurement of the presence of histamine. Similarly, the biosensor responds to the presence of VEGF, but is much more sensitive because VEGF is known to be 50,000-fold more potent than histamine when inducing EC hyperpermeability. The ISE response increased with increasing VEGF concentration. Since lower concentrations required more exposure time, the detection limit was established as a function of exposure time (2–10 h). The practical applicability of the biosensor was also established with cultured human melanoma cells WM793 (nonmetastatic) and 1205LU (metastatic). The resultant change in the potential values revealed significant production of VEGF from the 1205LU cells. A VEGF ELISA was performed to confirm the VEGF concentration in each sample. The biosensor closely predicted the concentrations determined through the ELISA. These results support the use of a cell-based ISE as a quick screening method for the presence of VEGF.

Keywords: Ion-selective electrodes; Biosensor; VEGF; Cancer

Mass spectrometric identification of modified urinary nucleosides used as potential biomedical markers by LC–ITMS coupling by Bernd Kammerer; Antje Frickenschmidt; Christa E. Müller; Stefan Laufer; Christoph H. Gleiter; Hartmut Liebich (pp. 1017-1026).

In diseases accompanied by strong metabolic disorders, like cancer and AIDS, modifying enzymes are up- or down-regulated. As a result, many different types of metabolic end-products, including abnormal amounts of modified nucleosides, are found in urine. These nucleosides are degradation products of an impaired ribonucleic acid (RNA) metabolism, which affects the nucleoside pattern in urine. In several basic experiments we elucidated the fragmentation pathways of 16 characteristic nucleosides and six corresponding nucleic bases that occur in urine using electrospray ionization ion trap MS⁵ (ESI-ITMS) experiments operated in positive ionization mode. For urinary nucleoside analysis, we developed an auto-LC–MS³ method based on prepurification via boronate gel affinity chromatography followed by reversed phase chromatography. For this purpose, an endcapped LiChroCART Superspher RP 18 column with a gradient of ammonium formate and a methanol–water mixture was used. This method gives a limit of detection of between 0.1 and 9.6 pmol for 15 standard nucleosides, depending on the basicity of the nucleoside. Overall, the detection of 36 nucleosides from urine was feasible. It was shown that this auto-LC–MS³ method is a valuable tool for assigning nucleosides from complex biological matrices, and it may be utilized in the diagnosis of diseases associated with disorders in RNA metabolism.

Keywords: Modified nucleosides; Ion trap mass spectrometry; Fragmentation pattern of nucleosides; Tumor markers; Urinary nucleosides

Simultaneous measurement of specific serum IgG responses to five select agents by R. E. Biagini; D. L. Sammons; J. P. Smith; B. A. MacKenzie; C. A. F. Striley; S. A. Robertson; J. E. Snawder; C. P. Quinn (pp. 1027-1034).

Select Agents are defined by CDC and the USDA Animal and Plant Health Inspection Service (APHIS) as biological agents or toxins deemed a threat to public, animal, or plant health, or to animal or plant products. They are classified on the basis of their ease of dissemination, mortality/morbidity rate, and potential for social disruption. A subset of these agents includes Bacillus anthracis, Yersinia pestis, Francisella tularensis, ricin toxin (RT), and staphylococcal enterotoxin B (SEB). Infection or intoxication with these agents has been shown to elicit an antigen-specific serum IgG response. We describe a fluorescent covalent microsphere immunoassay (FCMIA) for measurement of specific IgG antibodies to seven different antigens from five different select agents; B. anthracis [protective antigen (PA) and lethal factor (LF)], Y. pestis (F1 and V antigens), F. tularensis, RT and SEB simultaneously in human B. anthracis vaccinee sera (containing anti-PA and anti-LF IgG) which had been spiked with animal specific IgG antibodies to the other select agents. Inter-assay and intra-assay coefficients of variation were 6.5 and 13.4%, respectively (N=4). There were no significant differences (P>0.70) between assay responses when the assays were performed individually or multiplexed. When the observed versus expected interpolated concentrations were compared, highly linear relationships were observed (r² values from 0.981 to 0.999, P<0.001). Minimum detectable concentrations (MDC) ranged from 0.3 ng mL⁻¹ (Y. pestis F1) to 300 ng mL⁻¹ (RT). Finally, the curves showed responses were linear for most analytes from their MDC to 125 (SEB) to 1,300 (Y. pestis F1)×their MDC. These data indicate that multiplexed FCMIA is a sensitive and accurate method for simultaneous measurement of specific IgG in serum to CDC select agents and may be of value in screening either decontamination workers or the general population for exposure to/infection with these agents.

Keywords: Anthrax; Tularemia; Plague; Staphylococcal enterotoxin B; Ricin

Determination of prostatic androgens in 10 mg of tissue using liquid chromatography–tandem mass spectrometry with charged derivatization by Tatsuya Higashi; Akinori Yamauchi; Kazutake Shimada; Eitetsu Koh; Atsushi Mizokami; Mikio Namiki (pp. 1035-1043).

A practical liquid chromatography–tandem mass spectrometric (LC-MS-MS) method for the determination of prostatic 5α-dihydrotestosterone (DHT) and testosterone (T) has been developed. The prostatic androgens were extracted with MeOH–H₂O (3: 7, v/v), purified with an Oasis HLB cartridge, derivatized with the permanently charged reagent 2-hydrazino-1-methylpyridine (HMP), and subjected to LC–MS-MS analysis using electrospray ionization (ESI) operated in the positive ion mode. The derivatization with HMP was very effective at increasing the detectability using the positive-ESI-MS. The method allowed the reproducible and accurate quantification of ng g⁻¹ tissue levels of prostatic androgens in 10 mg of tissue. That is, the intra- and inter-assay coefficients of variation were below 8.1 and 9.3%, respectively, and the analytical recoveries of the androgens were quantitative. The limits of quantitation for DHT and T were both 1.0 ng g⁻¹ tissue. The developed method was used to determine DHT and T in the prostates of patients with benign prostatic hyperplasia and prostate cancer, and satisfactory results were obtained.

Keywords: LC-ESI-MS-MS; Charged derivatization; Human prostate; Androgens

One-step synthesis of amino-dextran-protected gold and silver nanoparticles and its application in biosensors by Ying Ma; Nan Li; Cheng Yang; Xiurong Yang (pp. 1044-1048).

A sensitive method for the detection of the lectin protein concanavalin A (Con A) was developed using amino-dextran (AD)-protected gold (AD-Au) and silver nanoparticles (AD-Ag) as sensitive optical probes. The AD-Au and AD-Ag nanoparticles were synthesized by directly applying amino-dextran as a reductive and protective reagent. The size of the nanoparticles could be altered by changing the molar ratio of AD to the metal salt. The amino-dextran bound to Con A by forming a 4:1 Au-Con A complex at neutral pH, and the nanoparticles were induced to aggregate by Con A. The absorption intensity of the nanoparticles decreased linearly with as the Con A concentration was increased from 3.85×10⁻⁸ to 6.15×10⁻⁷ M. The Au-Con A complex was dissociated by the disaccharide isomaltose, which has a higher affinities for Con A than Au; this competitive strategy could also be used to detect similar types of saccharides.

Keywords: Amino-dextran; Nanoparticles; Gold; Silver; Concanavalin A; Biosensor

Development and validation of a selective and robust LC-MS/MS method for quantifying amlodipine in human plasma by P. Massaroti; L. A. B. Moraes; M. A. M. Marchioretto; N. M. Cassiano; G. Bernasconi; S. A. Calafatti; F. A. P. Barros; E. C. Meurer; J. Pedrazzoli (pp. 1049-1054).

A liquid chromatographic–tandem mass spectrometric method (LC-MS/MS) for quantifying amlodipine in human plasma was developed and validated. Sample preparation was based on liquid–liquid extraction using NaOH and a mixture of ethyl acetate/hexane (80/20; v/v). Chromatography was performed on a C-18 analytical column and the retention times were 1.9 and 3.0 min for amlodipine and nimodipine (internal standard), respectively. The ionization was optimized using ESI(+) and enhanced selectivity was achieved using tandem mass spectrometric analysis via two MRM functions, 409→238 and 418→343 for amlodipine and nimodipine. The calibration curve ranged from 0.2 to 20.0 ng/mL. The inter-day precision and accuracy and the relative standard deviation (RSD) were <15%. The analyte was shown to be stable over the timescale of the whole procedure. The robustness of the method was demonstrated by the good reproducibility of the results obtained during the analysis of clinical samples.

Keywords: Mass spectrometry; Bioequivalence; Amlodipine

Enhancing the ratio of molecular ions to non-covalent compounds in the electrospray interface of LC-MS in quantitative analysis by A. K. Hewavitharana; P. N. Shaw (pp. 1055-1059).

A common problem encountered during the development of MS methods for the quantitation of small organic molecules by LC-MS is the formation of non-covalently bound species or adducts in the electrospray interface. Often the population of the molecular ion is insignificant compared to those of all other forms of the analyte produced in the electrospray, making it difficult to obtain the sensitivity required for accurate quantitation. We have investigated the effects of the following variables: orifice potential, nebulizer gas flow, temperature, solvent composition and the sample pH on the relative distributions of ions of the types MH⁺, MNa⁺, MNH₄⁺, and 2MNa⁺, where M represents a small organic molecule: BAY 11-7082 ((E)-3-[4-methylphenylsulfonyl]-2-propenenitrile). Orifice potential, solvent composition and the sample pH had the greatest influence on the relative distributions of these ions, making these parameters the most useful for optimizing methods for the quantitation of small molecules.

Keywords: LC-MS; Electrospray; Ionspray; Adducts; Non-covalently bound species

Simultaneous determination of arsenic and selenium in biological samples by HG-AFS by Hanwen Sun; Zhanfeng Liu; Wenjuan Wu; Liqing Li; Hongmei Shi (pp. 1060-1065).

A new method is proposed for simultaneous determination of traces of arsenic (As) and selenium (Se) in biological samples by hydride-generation double-channel non-dispersive atomic-fluorescence spectrometry (HG-AFS) from tartaric acid media. The effects of analytical conditions on fluorescence signal intensity were investigated and optimized. Interferences from coexisting ions were evaluated. Under optimum conditions linear response ranges above 20 μg L⁻¹ for As and 32 μg L⁻¹ for Se were obtained with detection limits of 0.13 and 0.12 μg L⁻¹, respectively. The precision for elevenfold determination of As at the 4 μg L⁻¹ level and of Se at the 8 μg L⁻¹ level were 2.7 and 1.9% (RSD), respectively. Recoveries of 92.5–95.5% for As and 101.2–108.4% for Se were obtained for four biological samples and two certified biological reference materials. The proposed method has the advantages of simple operation, high sensitivity, and high efficiency; it was successfully used for simultaneous determination of As and Se in biological samples.

Keywords: Simultaneous determination; Arsenic; Selenium; Biological samples; Atomic fluorescence spectrometry

Determination of antihypertensive mixtures by use of a chemometrics-assisted spectrophotometric method by Abd El-Maaboud I. Mohamed; Hesham Salem (pp. 1066-1072).

A simple multivariate calibration method for analysis of two types of hypotensive mixture is described. The mixtures are composed of chlorthalidone with atenolol or chlorthalidone with both amiloride hydrochloride and atenolol. The components of the mixtures result in substantial spectral overlap—between 87.5 and 91.0%. Resolution of the mixtures under investigation has been accomplished mainly by using CLS and PCR methods. The components in each mixture have been simultaneously determined in three commercial dosage forms with high accuracy and without interference from commonly encountered excipients and additives. Good recoveries were obtained with both synthetic mixtures and commercial tablets. The results obtained were compared with those from pharmacopeial methods and found to be in good agreement. The results obtained from CLS and PCR were also compared with those obtained from a ¹D spectrophotometric method.

Keywords: Multivariate analysis; Hypotensive mixtures; Chlorthalidone; Atenolol; Amiloride hydrochloride

Discriminating animal fats and their origins: assessing the potentials of Fourier transform infrared spectroscopy, gas chromatography, immunoassay and polymerase chain reaction techniques by Stefano Bellorini; Stefan Strathmann; Vincent Baeten; Olivier Fumière; Gilbert Berben; Salvatore Tirendi; Christoph von Holst (pp. 1073-1083).

The objective of the reported study was to assess the abilities of various methods to differentiate the sources of fats used in feedstuff formulations. The main target was the identification of tallow (ruminant fat) and its differentiation from non-ruminant fats. Four different techniques were compared in terms of their suitability for enforcing existing and upcoming legislation on animal by-products: (1) Fourier transform infrared spectroscopy (FT-IR) applied to fat samples, (2) gas chromatography coupled with mass spectrometry (GC–MS) to determine fatty acid profiles, (3) immunoassays focusing on the protein fraction included in the fat, and (4) polymerase chain reaction (PCR) for the detection of bovine-specific DNA. Samples of the different fats and oils as well as mixtures of these fats were probed using these analytical methods. FT-IR and GC–MS differentiated pure fat samples quite well but showed limited ability to identify the animal species or even the animal class the fat(s) belonged to; no single compound or spectral signal that could permit species identification could be found. However, immunoassays and PCR were both able to identify the species or groups of species that the fats originated from, and they were the only techniques able to identify low concentrations of tallow in a mixture of fats prepared by the rendering industry, even when the samples had been sterilised at temperatures >133 °C. Fats used in animal nutrition come mainly from the rendering industry, thereby confirming the suitability of PCR and immunoassays for their identification. However, neither of these latter techniques was able to detect “premier jus” tallow, representing the highest quality standard of fat with extremely low protein concentration.

Keywords: Animal fats; Species identification; FT-IR; GC–MS; Immunoassay technique; PCR; TSE

Determination of phthalate monoesters in human milk, consumer milk, and infant formula by tandem mass spectrometry (LC–MS–MS) by Gerda K. Mortensen; Katharina M. Main; Anna-Maria Andersson; Henrik Leffers; Niels E. Skakkebæk (pp. 1084-1092).

Daily exposure of humans to phthalates may be a health risk because animal experiments have shown these compounds can affect the differentiation and function of the reproductive system. Because milk is the main source of nutrition for infants, knowledge of phthalate levels is important for exposure and risk assessment. Here we describe the development and validation of a quantitative analytical procedure for determination of phthalate metabolites in human milk. The phthalate monoesters investigated were: monomethyl phthalate (mMP), monoethyl phthalate (mEP), mono-n-butyl phthalate (mBP), monobenzyl phthalate (mBzP), mono-(2-ethylhexyl) phthalate (mEHP), and monoisononyl phthalate (mNP). The method is based on liquid extraction with a mixture of ethyl acetate and cyclohexane (95:5) followed by two-step solid-phase extraction (SPE). Detection and quantification of the phthalate monoesters were accomplished by high-pressure liquid chromatography using a Betasil phenyl column (100 mm×2.1 mm×3 μm) and triple tandem mass spectrometry (LC–MS–MS). Detection limits were in the range 0.01 to 0.5 μg L⁻¹ and method variation was from 5 to 15%. Analysis of 36 milk samples showed that all these phthalates were present, albeit at different concentrations. Median values (μg L⁻¹) obtained were 0.11 (mMP), 0.95 (mEP), 3.5 (mBP), 0.8 (mBzP), 9.5 (mEHP), and 101 (mNP). We also analysed seven samples of consumer milk and ten samples of infant formula. Only mBP and mEHP were detected in these samples, in the ranges 0.6–3.9 μg L⁻¹ (mBP) and 5.6–9.9 μg L⁻¹ (mEHP).

Keywords: Phthalates; Exposure; Analysis; Human milk; Consumer milk; Infant formula

Continuous ultrasound-assisted extraction of cadmium from legumes and dried fruit samples coupled with on-line preconcentration-flame atomic absorption spectrometry by M. C. Yebra; S. Cancela (pp. 1093-1098).

Cadmium was continuously extracted with diluted nitric acid from legumes and dried fruit samples using a simple, rapid and continuous ultrasound-assisted extraction system. A minicolumn packed with a chelating resin (Chelite P, with aminomethylphosphoric acid groups) was placed between the extraction unit and the detector for cadmium preconcentration. The cadmium content in the acid extract was retained into the minicolumn, and elution was carried out with hydrochloric acid, with this trace metal continuously monitored by flame atomic absorption spectrometry. An experimental design (Plackett-Burman 2⁶×3/16) was used to optimize the continuous leaching procedure and the preconcentration step. The method allowed a total sampling frequency of 10 and 14 samples per hour for legumes and dried fruit, respectively. The procedure displayed good precision (2.0 and 2.5%, respectively, expressed as relative standard deviations) for samples containing 0.202±0.005 μg g⁻¹ Cd (broad bean) and 0.239±0.004 μg g⁻¹ Cd (peanut). Detection limits of 0.014 μg g⁻¹ Cd for 60 mg of legume samples and 0.011 μg g⁻¹ Cd for 80 mg of dried fruit samples were obtained. The method was successfully applied to the determination of trace amounts of cadmium in legumes and dried fruit samples.

Keywords: Ultrasound-assisted acid extraction; Minicolumn preconcentration; Cadmium; Flame atomic absorption spectrometry; Flow injection analysis; Legumes and dried fruit samples

Determination of copper in powdered chocolate samples by slurry-sampling flame atomic-absorption spectrometry by Walter N. L. dos Santos; Erik G. P. da Silva; Marcelo S. Fernandes; Rennan G. O. Araujo; Antônio C. S. Costa; M. G. R. Vale; Sèrgio L. C. Ferreira (pp. 1099-1102).

Chocolate is a complex sample with a high content of organic compounds and its analysis generally involves digestion procedures that might include the risk of losses and/or contamination. The determination of copper in chocolate is important because copper compounds are extensively used as fungicides in the farming of cocoa. In this paper, a slurry-sampling flame atomic-absorption spectrometric method is proposed for determination of copper in powdered chocolate samples. Optimization was carried out using univariate methodology involving the variables nature and concentration of the acid solution for slurry preparation, sonication time, and sample mass. The recommended conditions include a sample mass of 0.2 g, 2.0 mol L⁻¹ hydrochloric acid solution, and a sonication time of 15 min. The calibration curve was prepared using aqueous copper standards in 2.0 mol L⁻¹ hydrochloric acid. This method allowed determination of copper in chocolate with a detection limit of 0.4 μg g⁻¹ and precision, expressed as relative standard deviation (RSD), of 2.5% (n=10) for a copper content of approximately 30 μg g⁻¹, using a chocolate mass of 0.2 g. The accuracy was confirmed by analyzing the certified reference materials NIST SRM 1568a rice flour and NIES CRM 10-b rice flour. The proposed method was used for determination of copper in three powdered chocolate samples, the copper content of which varied between 26.6 and 31.5 μg g⁻¹. The results showed no significant differences with those obtained after complete digestion, using a t-test for comparison.

Keywords: slurry-sampling; FAAS; Copper; Chocolate

Detection and quantification of PAH in drinking water by front-face fluorimetry on a solid sorbent and PLS analysis by Manuel Algarra; Victoria Jiménez; Philippe Fornier de Violet; Michel Lamotte (pp. 1103-1110).

The direct determination in drinking water of perylene, chrysene, pyrene, benzo[a]pyrene, and benzo[k]fluoranthene, by front-face synchronous fluorimetry on a commercial SPE disk, has been evaluated. Sorbent treatment, influence of humic substances, and pH effect are discussed. In pure water the detection limits were estimated to be in the range 0.03–0.01 μg L⁻¹. A working pH in the range 10–11 was found to minimize the fluorescence quenching effect of humic substances. The proposed method combined with a partial-least-square (PLS) treatment was tested for quantitative analysis of mixtures of four PAH in a spiked drinking water.

Keywords: Solid-phase extraction; Synchronous fluorescence; Polycyclic aromatic hydrocarbons; Drinking water

Determination of hexavalent chromium by using speciated isotope-dilution mass spectrometry after microwave speciated extraction of environmental and other solid materials by G. M. Mizanur Rahman; H. M. Skip Kingston; Theodore G. Towns; Rock J. Vitale; Kyle R. Clay (pp. 1111-1120).

Precise and accurate determination of hexavalent chromium in different types of solid environmental sample is regarded as a technical challenge with significant potential error if historically accepted methods are used. Microwave-assisted alkaline extraction (0.5 mol L⁻¹ NaOH+0.28 mol L⁻¹ Na₂CO₃) followed by anion-exchange chromatographic separation and inductively coupled plasma mass spectrophotometric detection has been shown to provide accurate and precise results. To obtain a better understanding of potential species conversion during and/or after extraction steps, speciated isotope-dilution mass spectrometry (SIDMS) (EPA Method 6800) metrology has been successfully applied as a diagnostic tool with the modified accompanying extraction version of EPA Method 3060A. In our study, aggregate materials distributed over a large area of a major western US state were found to contain a high concentration of total chromium (195±13 to 709±19 μg g⁻¹) and significant amounts of Cr⁶⁺ (141±6 to 341±29 μg g⁻¹) which are at least three orders of magnitude higher than the US EPA threshold limit (0.5 μg g⁻¹). Sediment samples from a major western US state, studied independently, were found to contain less (1.77±0.34 μg g⁻¹) or no Cr⁶⁺ in the presence of significant total chromium.

Keywords: Hexavalent chromium; Cr⁶⁺Speciation; Species; SIDMS; IDMS

Silica structure in the spicules of the sponge Suberites domuncula by Gerd Holzhüter; Kamatchi Lakshminarayanan; Thomas Gerber (pp. 1121-1126).

Accumulation of silica in marine organisms such as diatoms and sponges has been widely reported. The proteins depositing silica in these organisms have been identified and its structure has also been described. The ultrastructure of silica has not been studied in detail, however. Herein we describe the structure of silica in the spicules of the sponge Suberites domuncula. Peroxide treatment was performed to remove the organic compounds, thereby enabling a better study of the silica. Methods used for the study included scanning and transmission electron microscopy. Electron diffraction enabled structural comparison with silica glass at the atomic level. Small-angle X-ray scattering (SAXS) of the spicules was also conducted and structure correlation between these methods attempted. At a lower magnification, spicule needles with a smooth outer surface were visible. Diffraction results suggested a network-like structure in the spicules. Silica particles of 3 nm diameter could be measured by SAXS.

Keywords: SpongeSuberites domunculaSpicule; Silica; Electron microscopy; SAXS

Quantitative determination of organochlorine pesticides in sewage sludges using soxtec, soxhlet and pressurized liquid extractions and ion trap mass–mass spectrometric detection by M. I. H. Helaleh; A. Al-Omair; N. Ahmed; B. Gevao (pp. 1127-1134).

A new analytical method is described for the determination of organochlorine pesticides (OCPs) in sewage sludges using GC-ion trap-MS–MS. In this work, 16 organo-chlorine pesticides (OCPs) listed by the US Environmental Protection Agency (US EPA) as priority pollutants were separated and quantified. Sludge samples from three of Kuwait’s wastewater treatment plants (WWTPs) were analyzed for organochlorine pesticides (OCPs). Spiked sludge samples were extracted with a mixture of (1:1 v/v) dichloromethane (DCM)/hexane. The extracts were cleaned on a silica/aluminum oxide column, then transferred to a gel permeation chromatography (GPC) column, before undergoing further silica/aluminum oxide clean-up; the presence of OCPs was then confirmed by GC-ion trap-MS–MS. Three extraction techniques, soxtec, soxhlet, and pressurized liquid extractions were utilized, compared and validated using the spiked sludge samples. The methods were validated in term of accuracy (recovery) and precision (RSD). The method recovery values varyied from 76.1 to 92.9% for the three extraction techniques.

Keywords: Quantitative; Organochlorine pesticides; Sewage sludges; GC-ion trap-MS–MS

Extraction of p-hydroxyacetophenone and catechin from Norway spruce needles. Comparison of different extraction solvents by Magda Vosmanská; David Sýkora; Jan Fähnrich; Marcela Kovářová; Karel Volka (pp. 1135-1140).

The phenolic compounds p-hydroxyacetophenone and catechin have been extracted from Norway spruce needles with pure methanol, 80 and 50% (v/v) aqueous methanol, pure acetonitrile, 80% (v/v) aqueous acetonitrile, and pure water. Extraction efficiency of the individual solvents was compared. Although 80% aqueous methanol is the solvent most frequently used for extraction of soluble phenolic compounds from needles, it was found that pure methanol is a more suitable extraction solvent. Surprisingly, a two-step procedure based on the extraction of crushed needles with water then re-extraction with methanol proved a good alternative to direct extraction with methanol. Extraction of uncrushed spruce needles might indicate that relatively more p-hydroxyacetophenone than catechin was located in the surface layer of the needle.

Keywords: Picea abiesPhenolic compounds; Extraction

Development of a stir-bar-sorptive extraction–liquid desorption–large-volume injection capillary gas chromatographic–mass spectrometric method for pyrethroid pesticides in water samples by P. Serôdio; J. M. F. Nogueira (pp. 1141-1151).

Stir-bar-sorptive extraction followed by liquid desorption and large-volume injection capillary gas chromatography with mass spectrometric detection (SBSE–LD–LVI-GC–MS), had been applied for the determination of ultra-traces of eight pyrethroid pesticides (acrinathrin, cypermethrin, deltamethrin, esfenvalerate, fenpropathrin, fenvalerate, and permethrin cis and trans isomers) in water samples. Instrumental calibration for selected-ion monitoring acquisition and conditions that could affect the SBSE–LD efficiency are fully discussed. By performing systematic assays on 30-mL water samples spiked at the 0.10 μg L⁻¹ level it was established that stir-bars coated with 47 μL polydimethylsiloxane, an equilibrium time of 60 min (750 rpm), 5% methanol as organic modifier, and acetonitrile as back-extraction solvent, provided the best analytical performance to monitor pyrethroid pesticides in water matrices. Good accuracy (81.8–105.0%) and remarkable reproducibility (<11.7%) were obtained, and the experimental recovery data were in good agreement with the theoretical equilibrium described by octanol–water partition coefficients (log K_O/W), with the exception of acrinathrin for which lower yields were measured. Excellent linear dynamic ranges between 25 and 400 ng L⁻¹ (r²>0.994), low quantification (3.0–7.5 ng L⁻¹) and detection (1.0–2.5 ng L⁻¹) limits were also achieved for the eight pyrethroid pesticides studied. The method was successfully used for analysis of tapwater and groundwater matrices spiked at the 0.10 μg L⁻¹, revealing the suitability of the method for determination of pyrethroid pesticides in real samples. The method was shown be reliable and sensitive and a small volume of sample was required to monitor pyrethroids at ultra-trace levels, in compliance with international regulatory directives on water quality.

Keywords: Capillary GC–MS; Large-volume injection; Stir-bar-sorptive extraction; Liquid desorption; Water samples; Pyrethroid pesticides

Direct determination of several elements in MIBK extract by high-power nitrogen-oxygen mixed gas microwave-induced plasma optical emission spectrometry by Tetsuo Maeda; Kazuaki Wagatsuma; Yukio Okamoto (pp. 1152-1158).

A nitrogen-oxygen mixed gas microwave-induced plasma with an Okamoto cavity was employed as an atomization and excitation source for emission spectrometric analysis of organic solvent samples. Nitrogen–oxygen mixed gas produces very a stable microwave-induced plasma that is highly robust to the loading of 4-methyl-2-pentanone (MIBK), possibly because the organic solvent is completely combusted in the oxygen-containing plasma. After extracting test solutions containing Al, Co, Cr(III), Cu, Fe(III), Mo(VI), Ni, Pb with MIBK, both the aqueous phase and the organic phase were aspirated into the microwave-induced plasma, yielding linear calibration curves for both the species in the aqueous phase (Al, Co, Cr, Ni, and Pb) and those in the organic phase (Fe and Mo). These results indicate that Fe and Mo can be extracted with MIBK, which is explained by the partition coefficients of these elements in MIBK.

Keywords: Microwave-induced plasma; Okamoto cavity; Optical emission spectrometry; Loading of organic solvent; MIBK extraction; Band spectrum

Development of a PVC-membrane ion-selective bulk optode, for UO₂²⁺ ion, based on tri-n-octylphosphine oxide and dibenzoylmethane by Mojtaba Shamsipur; Javad Tashkhourian; Hashem Sharghi (pp. 1159-1162).

A novel uranyl ion-selective bulk optode membrane, incorporating tri-n-octylphosphine oxide for cation recognition and a lipophilic chromoionophore dibenzoylmethane, has been prepared. The PVC membrane composition was optimized to result in the widest working concentration range. The response range of the proposed optode is 4.1×10⁻⁶ to 2.0×10⁻⁴ mol L⁻¹ UO₂²⁺. The probe works at pH 4.0. Ion interference is low and selectivity, reproducibility, and stability are good.

Keywords: UO₂²⁺-selective bulk optode; PVC membrane; Tri-n-octylphosphine oxide; Dibenzoylmethane

Ion-exchange behavior of stannic selenoiodate and stannic selenosilicate: analytical application of stannic selenoiodate by Syed Ashfaq Nabi; Amjad Mumtaz Khan (pp. 1163-1168).

Two new inorganic ion exchangers, stannic selenoiodate and stannic selenosilicate have been synthesized. The ion-exchange capacity of stannic selenoiodate and stannic selenosilicate for K⁺ was found to be 1.84 and 1.23 meq g⁻¹, respectively. pH titration studies reveal monofunctional and bifunctional behavior for stannic selenosilicate and stannic selenoiodate, respectively. Distribution coefficients of metal ions in dimethylformamide–HCl and formamide–HCl systems have been determined. Some important and analytically difficult quantitative binary and ternary separations, and selective separations of Ag⁺, Sn⁴⁺, Zr⁴⁺, Co²⁺, and Ni²⁺ have been achieved on stannic selenoiodate columns. The practical utility of the material has been demonstrated by analyzing the metal ion content of electroplating waste.

Keywords: Synthesis; Inorganic ion exchangers; Stannic selenoiodate; Stannic selenosilicate; Analytical applications

Gas sensing using edge-plane pyrolytic-graphite electrodes: electrochemical reduction of chlorine by Eleanor R. Lowe; Craig E. Banks; Richard G. Compton (pp. 1169-1174).

The voltammetric responses of chlorine in aqueous acid solutions have been explored using different carbon-based electrodes. Edge-plane pyrolytic graphite has more electrochemical reversibility than glassy carbon, basal-plane pyrolytic graphite, or boron-doped diamond electrodes. A significant reduction in the overpotential is observed on the edge-plane pyrolytic-graphite electrode in contrast with the other carbon-based electrode substrates. These results suggest that edge-plane pyrolytic graphite can be optimally used as the working electrodes in Clark-cell devices for low-potential amperometric gas sensing of Cl₂.

Keywords: Edge-plane pyrolytic graphite; Chlorine; Amperometric detection; Gas sensing

Development of cysteine-modified screen-printed electrode for the chronopotentiometric stripping analysis of cadmium(II) in wastewater and soil extracts by Mohd F. Md Noh; Rashid O. Kadara; Ibtisam E. Tothill (pp. 1175-1186).

Screen-printed carbon electrodes were fabricated with amino acid functionality by using in situ co-deposition of mercury and cysteine. The three-electrode configuration (graphite carbon working electrode, carbon counter electrode and silver/silver chloride reference electrode) incorporating a cysteine-modified working electrode exhibited good sensitivity towards cadmium(II). Several experimental variables affecting the sensor stripping response were characterised and optimised. These include cysteine and mercury concentrations, deposition time, deposition potential and stripping current. Surface analysis was also conducted using scanning electron microscopy (SEM) in order to characterize the electrode surface during cadmium analysis. The stripping chronopotentiometric response for cadmium(II) was linear in the concentration range 0.4–800 μg L⁻¹ when a deposition time of 2 min was used. A detection limit of 0.4 μg L⁻¹ was obtained using 0.025 M Tris–HCl buffer containing 0.1 M KCl (pH 7.4) as the supporting electrolyte. The analytical utility of the cysteine-modified sensor was demonstrated by applying it to cadmium analysis in various wastewater and soil samples collected from a contaminated site and extracted using acetic acid. The results obtained using the developed electrodes agreed satisfactorily with the values achieved using atomic absorption spectrometry and inductively coupled plasma mass spectrometry analysis. These results demonstrate the feasibility of using this type of sensor for cadmium analysis.

Keywords: Cadmium(II) analysis; Stripping chronopotentiometryL-Cysteine; Screen-printed electrodes; Soil extracts; Wastewaters

Electrochemical reduction and flow detection of iodate on (Bu₄N)₂Mo₆O₁₉ self-assembled monolayer by Li Chen; Xuefei Tian; Li Tian; Li Liu; Wenbo Song; Hongding Xu (pp. 1187-1195).

A stable monolayer of the inorganic–organic hybrid polyoxometalate (Bu₄N)₂Mo₆O₁₉, denoted as Mo₆O₁₉, was formed on a sodium-3-mercapto-1-propanesulfonate (MPPS)-covered gold electrode surface, interlaced with an anionic poly(dimethyldiallylammonium chloride) (PDDA) binding layer based on the electrostatic self-assembled (ESA) technique. Electrochemical characterization of the Mo₆O₁₉ self-assembled thin films on the solid surface by cyclic voltammetry and AC impedance spectroscopy revealed a stable and sensitive electrocatalytic response to the reduction of iodate. Iodate was determined amperometrically through a flow injection cell at the modified electrode in the concentration range of 1.0×10⁻⁶ to 1.0×10⁻¹ M with a detection limit of 8×10⁻⁸ M (signal-to-noise ratio = 3). Performance was improved to meet practical needs compared with previously reported analogues.

Keywords: Flow amperometry; Inorganic–organic hybrid polyoxometalate; Electrostatic self-assembly; Electrocatalysis; Iodate

Electrochemistry of sinapine and its detection in medicinal plants by Hui Zhou; Yinxi Huang; Tomonori Hoshi; Yoshitomo Kashiwagi; Jun-ichi Anzai; Genxi Li (pp. 1196-1201).

Sinapine (O-sinapoyl choline) is a crucial component, with much medicinal value, of many dietary and medicinal plants. It has been found that sinapine gives an electrochemical response at a pyrolytic graphite electrode. The electrochemical properties of sinapine have been investigated. The peak current in the cyclic voltammogram is linear in the concentration range 1.9×10⁻⁶–2.5×10⁻⁴ mol L⁻¹ and the limit of detection is 9.9×10⁻⁷ mol L⁻¹. These properties can be applied to the determination of sinapine in extracts from three kinds of medicinal plant. The electrochemical method reported here is highly selective, sensitive, and stable.

Keywords: Sinapine; Electrochemistry; Pyrolytic graphite; Detection; Medicinal plants

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Analytical and Bioanalytical Chemistry (v.382, #4)

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Analytical and Bioanalytical Chemistry (v.382, #4)