Determination of benzenic and halogenated volatile organic compounds in animal-derived food products by one-dimensional and comprehensive two-dimensional gas chromatography–mass spectrometry

Animal-derived products are particularly vulnerable to contamination by volatile organic compounds (VOCs). These lipophilic substances, which are generated by an increasing number of sources, are easily transferred to the atmosphere, water, soil, and plants. They are ingested by livestock and become trapped in the fat fraction of edible animal tissues. The aim of this work was to determine the occurrence, risk for human health and entryways of benzenic and halogenated VOCs (BHVOCs) in meat products, milks and sea foods using gas chromatography– mass spectrometry (GC–MS) techniques. In the first part, the occurrence and levels of the BHVOCs in animal products were studied. One muscle and three fat tissues were analysed by GC–Quad/MS in 16 lambs. Of 52 BHVOCs identified, 46 were found in the three fat tissues and 29 in all four tissues, confirming that VOCs are widely disseminated in the body. Twenty-six BHVOCs were quantified in fat tissues, and risk for consumer health was assessed for six of these compounds regulated by the US Environmental Protection Agency (EPA). The BHVOC content was found to be consistent with previous reports and was below the maximum contaminant levels set by the EPA. In the second part, the performance of GC×GC–TOF/MS for comprehensively detecting BHVOCs and showing their entryways in animal-derived food chains was assessed. Meat, milk and oysters were analysed by GC–Quad/MS and GC×GC–TOF/MS. For all these products, at least a 7-fold increase in the contaminants detected was achieved with the GC×GC–TOF/MS technique. The results showed that the production surroundings, through animal feeding or geographical location, were key determinants of BHVOC composition in the animal products.     

One- and two-dimensional gas chromatography–mass spectrometry and high performance liquid chromatography–diode-array detector fingerprints of complex substances: A comparison of classification performance of similar,complex Rhizoma Curcumae samples with the aid of chemometrics

Many complex natural or synthetic products are analysed either by the GC–MS (gas chromatography–mass spectrometry) or HPLC–DAD (high performance liquid chromatography–diode-array detector) technique, each of which produces a one-dimensional fingerprint for a given sample. This may be used for classification of different batches of a product. GC–MS and HPLC–DAD analyses of complex, similar substances represented by the three common types of the TCM (traditional Chinese medicine), Rhizoma Curcumae were analysed in the form of one- and two-dimensional matrices firstly with the use of PCA (Principal component analysis), which showed a reasonable separation of the samples for each technique. However, the separation patterns were rather different for each analytical method, and PCA of the combined data matrix showed improved discrimination of the three types of object; close associations between the GC–MS and HPLC–DAD variables were observed. LDA (linear discriminant analysis), BP-ANN (back propagation-artificial neural networks) and LS-SVM (least squares-support vector machine) chemometrics methods were then applied to classify the training and prediction sets. For one-dimensional matrices, all training models indicated that several samples would be misclassified; the same was observed for each prediction set. However, by comparison, in the analysis of the combined matrix, all models gave 100% classification with the training set, and the LS-SVM calibration also produced a 100% result for prediction, with the BP-ANN calibration closely behind. This has important implications for comparing complex substances such as the TCMs because clearly the one-dimensional data matrices alone produce inferior results for training and prediction as compared to the combined data matrix models. Thus, product samples may be misclassified with the use of the one-dimensional data because of insufficient information.     

High-throughput approach for analysis of multicomponent gas chromatographic–mass spectrometric signals

Hyphenated techniques such as gas chromatography–mass spectrometry (GC–MS) or high-performance liquid chromatography–mass spectrometry (LC–MS) produce a large amount of data in a form of two-way data matrix. It has been a great challenge to furthest extract the useful information from the data. In this work, a chemometric approach based on a modification of adaptive immune algorithm (AIA) was proposed for a high-throughput analysis of the multicomponent overlapping GC–MS signals. With the proposed method, the chromatographic profile of each component in an overlapping signal can be extracted independently and sequentially along the retention time. In order to show the efficiency of the method, a stimulated GC–MS data of six components with background and an experimental GC–MS data of 40 pesticides were investigated. It was found that the multicomponent overlapping GC–MS signals could be fast and accurately resolved. Furthermore, the quantitative property of the extracted information was also investigated. The correlation coefficients (r) between the peak area and the added volumes of the sample are in the range 0.9658–0.9953.     

Tutorial review on validation of liquid chromatography–mass spectrometry methods: Part I

This is the part I of a tutorial review intending to give an overview of the state of the art of method validation in liquid chromatography mass spectrometry (LC–MS) and discuss specific issues that arise with MS (and MS/MS) detection in LC (as opposed to the “conventional” detectors). The Part I briefly introduces the principles of operation of LC–MS (emphasizing the aspects important from the validation point of view, in particular the ionization process and ionization suppression/enhancement); reviews the main validation guideline documents and discusses in detail the following performance parameters: selectivity/specificity/identity, ruggedness/robustness, limit of detection, limit of quantification, decision limit and detection capability. With every method performance characteristic its essence and terminology are addressed, the current status of treating it is reviewed and recommendations are given, how to determine it, specifically in the case of LC–MS methods.     

Rapid simultaneous screening and identification of multiple pesticide residues in vegetables

A method for the rapid simultaneous screening and identification of multiple pesticide residues in vegetables was established using a novel database and gas chromatography in combination with hybrid quadrupole time-of-flight mass spectrometry (GC–QTOF MS). A total of 187 pesticides with different chemical species were measured by GC–QTOF MS to create the database, which collected the retention time and exact masses of ions from the first-stage mass spectrum (MS¹ spectrum) and second-stage mass spectrum (MS² spectrum) for each pesticide. The workflow of the created database consisted of “MS¹ screening” for possible pesticides by chemical formula match and “MS² identification” for structural confirmation of product ion by accurate mass measurement. To evaluate the applicability of the database, a spinach matrix was prepared by solid phase extraction, spiked with a mixture of 50 pesticides at seven concentrations between 0.1 and 10 ppb, and analyzed by GC–QTOF MS. It was found that all of the 50 pesticides with concentrations as low as 5 ppb were detected in the “MS¹ screening” step and accurate masses were identified with errors less than 2.5 mDa in the “MS² identification” step, indicating high sensitivity, accuracy, selectivity and specificity. Finally, to validate the applicability, the new method was applied to four fresh celery, rape, scallion and spinach vegetables from a local market. As a result, a total of 13 pesticides were found, with 11 in celery, 9 in rape, 3 in scallion and 2 in spinach. In conclusion, GC–QTOF MS combined with an exact mass database is one of the most efficient tools for the analysis of pesticide residues in vegetables.     

Pressurized liquid extraction and liquid chromatography–tandem mass spectrometry applied to determine iodinated X-ray contrast media in sewage sludge

Pressurized liquid extraction (PLE) has been successfully applied for the first time to the extraction of five iodinated X-ray contrast media from sludge. Once optimized all PLE parameters, the extract has been analyzed by liquid chromatography–tandem mass spectrometry, being the method developed sensible enough to reach limit of quantifications (LOQs) of 25 μg kg⁻¹ (d.w.). The developed method has been applied to the analysis of sludge from urban sewage treatment plants and although some compounds such as iopromide, diatrizoic acid and iopamidol have been identified, their concentrations have been lower than their LOQs.     

Determination of polyamine metabolome in plasma and urine by ultrahigh performance liquid chromatography–tandem mass spectrometry method: Application to identify potential markers for human hepatic cancer

To evaluate the potential relationship between cancer and polyamine metabolome, a UHPLC–MS/MS method has been developed and validated for simultaneous determination of polyamine precursors, polyamines, polyamine catabolite in human plasma and urine. Polyamine precursors including l-ornithine, lysine, l-arginine and S-adenosyl-l-methionine; polyamines including 1,3-diaminopropane, putrescine, cadaverine, spermidine, spermine, agmatine, N-acetylputrescine, N-acetylspermine and N-acetylspermidine; polyamine catabolite including γ-aminobutyric acid had been determined. The analytes were extracted from plasma and urine samples by protein precipitation procedure, and then separated on a Shim-pack XR-ODS column with 0.05% heptafluorobutyric acid (HFBA) in methanol and 0.05% HFBA in water. The detection was performed on UHPLC–MS/MS system with turbo ion spray source in the positive ion and multiple reaction-monitoring mode. The limits of quantitation for all analytes were within 0.125–31.25 ng mL⁻¹ in plasma and urine. The absolute recoveries of analytes from plasma and urine were all more than 50%. By means of the method developed, the plasma and urine samples from hepatic cancer patients and healthy age-matched volunteers had been successfully determined. Results showed that putrescine and spermidine in hepatic cancerous plasma were significant higher than those in healthy ones, while spermidine, spermine and N-acetylspermidine in hepatic cancerous urine were significant higher than those in healthy ones. The methods demonstrated the changes of polyamine metabolome occurring in plasma and urine from human subjects with hepatic cancer. It could be a powerful manner to indicate and treat hepatic cancer in its earliest indicative stages.     

Determination of nucleotides,nucleosides and their transformation products in Cordyceps by ion-pairing reversed-phase liquid chromatography–mass spectrometry

An ion-pairing reversed-phase liquid chromatography–mass spectrometry (IP-RP-LC–MS) was developed for the determination of nucleotides, nucleosides and their transformation products in Cordyceps. Perfluorinated carboxylic acid, namely pentadecafluorooctanoic acid (PDFOA, 0.25 mM), was used as volatile ion-paring agent and a reversed-phase column (Agilent ZORBAX SB-Aq column) was used for the separation of three nucleotides namely uridine-5′-monophosphate (UMP, 0.638–10.200 μg/mL), adenosine-5′-monophosphate (AMP, 0.24–7.80 μg/mL) and guanosine-5′-monophosphate (GMP, 0.42–13.50 μg/mL), seven nucleosides including adenosine (0.55–8.85 μg/mL), guanosine (0.42–6.75 μg/mL), uridine (0.33–10.50 μg/mL), inosine (0.21–6.60 μg/mL), cytidine (0.48–15.30 μg/mL), thymidine (0.20–6.30 μg/mL) and cordycepin (0.09–1.50 μg/mL), as well as six nucleobases, adenine (0.22–6.90 μg/mL), guanine (0.26–4.20 μg/mL), uracil (0.38–12.15 μg/mL), hypoxanthine (0.13–4.20 μg/mL), cytosine (0.39–12.45 μg/mL) and thymine (0.26–8.25 μg/mL) with 5-chlorocytosine arabinoside as the internal standard. The overall LODs and LOQs were between 0.01–0.16 μg/mL and 0.04–0.41 μg/mL for the 16 analytes, respectively. The contents of 16 investigated compounds in natural and cultured Cordyceps were also determined and compared after validation of the developed IP-RP-LC-MS method. The transformations of nucleotides and nucleosides in Cordyceps were evaluated based on the quantification of the investigated compounds in three extracts, including boiling water extraction (BWE), 24 h ambient temperature water immersion (ATWE) and 56 h ATWE extracts. Two transformation pathways including UMP → uridine → uracil and GMP → guanosine → guanine were proposed in both natural Cordyceps sinensis and cultured Cordyceps militaris. The pathway of AMP → adenosine → inosine → hypoxanthine was proposed in natural C. sinensis, while AMP → adenosine → adenine in cultured C. militaris. However, the transformation of nucleotides and nucleosides was not found in commercial cultured C. sinensis.     

A simple novel configuration for in-vial microporous membrane liquid–liquid extraction

A novel arrangement for microporous membrane liquid–liquid extraction from the aqueous donor phase to the organic acceptor phase within a micro-vial, which is compatible with the chromatograph autosampler is presented. The device consisted of a stoppered glass micro-vial containing the organic solvent where the septum of the screw stopper was replaced by a sized piece of membrane which is hermetically assembled to the volumetric flask containing the aqueous donor solution. The placement of the membrane in alternative contact with the solutions was achieved by orbital agitation. As a preliminary study, 2-ethylhexyl 4-(dimethylamino)benzoate has been determined (limit of quantification 0.11 μg L⁻¹, precision 7.4%). The small quantity of organic solvent used, the achieved sample cleanup, and the minimal handling and risk of cross-contamination are significant operational advantages.     

Isoliquiritigenin (4,2′,4′-trihydroxychalcone): A new matrix-assisted laser desorption/ionization matrix with outstanding properties for the analysis of neutral oligosaccharides

A novel matrix of isoliquiritigenin (ISL), a flavonoid with a chalcone structure (4,2′,4′-trihydroxychalcone), was demonstrated to be advantageous in the analysis of neutral oligosaccharides by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). With ISL as a matrix, adequate signal for an analyte can be obtained in much lower matrix concentrations and laser intensity compared to commonly used MALDI matrices. Four different sample preparation methods were tested, and the dried droplet method exhibited the best performance on MALDI-TOF-MS analysis of oligosaccharides with ISL as a matrix. For the analysis of carbohydrates, compared with popular matrices such as 2,5-dihydroxybenzoic acid (DHB) and 2,4,6-trihydroxyacetophenone (THAP), ISL exhibited outstanding matrix properties as follows: (1) higher homogeneity of crystallization thus allowing automatic data acquisition, (2) better spectral quality in terms of resolution and signal to noise ratio (S N⁻¹), (3) better salt tolerance, (4) higher sensitivity, and (5) enough fragmentation yield to use LIFT-TOF/TOF MS to get richer structural information. In addition, reliable quantitative analysis of oligosaccharides with a good linearity over two concentration orders (1–100 pmol μL⁻¹) and good reproducibility of the signal intensity (RSD less than 15%) were achieved using this matrix. These results give a new outlook on high-speed analysis of neutral carbohydrates by MALDI-TOF MS.     

Determination of tetrabromobisphenol-A,tetrachlorobisphenol-A and bisphenol-A in soil by ultrasonic assisted extraction and gas chromatography–mass spectrometry

In this work, an isotope dilution method for the determination, in agricultural and industrial soil samples, of tetrabromobisphenol-A, tetrachlorobisphenol-A and bisphenol-A by gas chromatography–mass spectrometry was developed. The compounds were extracted from soil by sonication assisted extraction in small columns (SAESC) with a low volume of ethyl acetate as extraction solvent. For dirty soil samples, such as industrial soils, a simultaneous clean-up on an acidified Florisil–anhydrous sodium sulfate mixture was carried out to remove interferences. After extraction, solvent was evaporated and analytes were derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and determined by isotope dilution gas chromatography with electron impact mass spectrometric detection in the selected ion monitoring mode (GC–MS–SIM), using ¹³C₁₂ labeled compounds as internal standards. Recoveries from spiked samples were between 88% and 108% and the estimated limits of detection (S/N = 3) varied from 30 pg g⁻¹ to 90 pg g⁻¹. The response obtained with this method was linear over the range assayed, 5–300 ng ml⁻¹, with correlation coefficients equal or higher than 0.999. The validated method was used to investigate the levels of these phenolic compounds in soil samples collected from different locations in Spain. Bisphenol-A was detected in all samples at concentrations from 0.7 ng g⁻¹ to 4.6 ng g⁻¹ in agricultural soils and from 1.1 ng g⁻¹ to 44.5 ng g⁻¹ in industrial soils. Tetrabromobisphenol-A was found in various soil samples at levels in the range of 3.4–32.2 ng g⁻¹ in industrial soils and at 0.3 ng g⁻¹ in one agricultural soil, whereas tetrachlorobisphenol-A was not detected.     

Electrowetting — From statics to dynamics

More than one century ago, Lippmann found that capillary forces can be effectively controlled by external electrostatic forces. As a simple example, by applying a voltage between a conducting liquid droplet and the surface it is sitting on we are able to adjust the wetting angle of the drop. Since Lippmann's findings, electrocapillary phenomena – or electrowetting – have developed into a series of tools for manipulating microdroplets on solid surfaces, or small amounts of liquids in capillaries for microfluidic applications. In this article, we briefly review some recent progress of fundamental understanding of electrowetting and address some still unsolved issues. Specifically, we focus on static and dynamic electrowetting. In static electrowetting, we discuss some basic phenomena found in DC and AC electrowetting, and some theories about the origin of contact angle saturation. In dynamic electrowetting, we introduce some studies about this rather recent area. At last, we address some other capillary phenomena governed by electrostatics and we give an outlook that might stimulate further investigations on electrowetting.     

Examination of segmental average mass spectra from liquid chromatography–tandem mass spectrometric (LC–MS/MS) data enables screening of multiple types of protein modifications

It has been observed that a modified peptide and its non-modified counterpart, when analyzed with reverse phase liquid chromatography, usually share a very similar elution property [1–3]. Inasmuch as this property is common to many different types of protein modifications, we propose an informatics-based approach, featuring the generation of segmental average mass spectra (^saMS), that is capable of locating different types of modified peptides in two-dimensional liquid chromatography–mass spectrometric (LC–MS) data collected for regular protease digests from proteins in gels or solutions. To enable the localization of these peptides in the LC–MS map, we have implemented a set of computer programs, or the ^saMS package, that perform the needed functions, including generating a complete set of segmental average mass spectra, compiling the peptide inventory from the Sequest/TurboSequest results, searching modified peptide candidates and annotating a tandem mass spectrum for final verification. Using ROCK2 as an example, our programs were applied to identify multiple types of modified peptides, such as phosphorylated and hexosylated ones, which particularly include those peptides that could have been ignored due to their peculiar fragmentation patterns and consequent low search scores. Hence, we demonstrate that, when complemented with peptide search algorithms, our approach and the entailed computer programs can add the sequence information needed for bolstering the confidence of data interpretation by the present analytical platforms and facilitate the mining of protein modification information out of complicated LC–MS/MS data.     

Fabric phase sorptive extraction: A new sorptive microextraction technique for the determination of non-steroidal anti-inflammatory drugs from environmental water samples

Fabric phase sorptive extraction (FPSE) is a new, yet very promising member of the sorbent-based sorptive microextraction family. It has simultaneously improved both the extraction sensitivity and the speed of the extraction by incorporating high volume of sol–gel hybrid inorganic–organic sorbents into permeable fabric substrates. The advantages of FPSE have been investigated for the determination of four non-steroidal anti-inflammatory drugs, ibuprofen, naproxen, ketoprofen and diclofenac, in environmental water samples in combination with gas chromatography–mass spectrometry. Initially, the significance of several parameters affecting FPSE: sorbent chemistry, matrix pH and ionic strength were investigated using a mixed level factorial design (3¹ × 2²). Then, other important parameters e.g., sample volume, extraction kinetics, desorption time and volume were also carefully studied and optimized. Due to the high sorbent loading on the FPSE substrate in the form of ultra-thin coating and the open geometry of the microextraction device, higher mass transfer of the target analytes occurs at a faster rate, leading to high enrichment factors in a relatively short period of time (equilibrium times: 45–100 min). Under optimal operational conditions, the limits of detection (S/N = 3) were found to be in the range of 0.8 ng L⁻¹ to 5 ng L⁻¹. The enrichment factors ranged from 162 to 418 with absolute extraction efficiencies varied from 27 to 70%, and a good trueness (82–116% relative recoveries) indicating that the proposed method can be readily deployed to routine environmental pollution monitoring. The proposed method was successfully applied to the analysis of target analytes in two influent and effluent samples from a wastewater treatment plant and two river water samples in Spain.     

Determination of amitraz and its transformation products in pears by ethyl acetate extraction and liquid chromatography–tandem mass spectrometry

A method has been developed for identification and quantification of the acaricide amitraz and its transformation products, 2,4-dimethylaniline (DMA), 2,4-dimethylformamidine (DMF) and N-2,4-dimethylphenyl-N-methylformamidine (DMPF) in pears. The analytes were extracted using ethyl acetate and anhydrous sodium sulphate. Analysis was performed by liquid chromatography–electrospray tandem mass spectrometry (LC–ESI-MS/MS) in the positive ion mode using a triple quadrupole (QqQ) instrument. Two precursor-product ion transitions were monitored for each compound in the selected reaction monitoring (SRM) mode. The method was validated with pears taken from the orchard before the amitraz treatment and spiked at the limit of quantification (LOQ), 10 times the LOQ and the maximum residue limit (MRL). Recoveries were between 70 and 106% and relative standard deviations were below 19% (n = 5 at each spiked level). Excellent sensitivity resulted in limits of detection (LODs) for all the compounds below 10 μg kg⁻¹. Quantification was carried out using matrix-matched standards calibration, response was a linear function of the concentration from the LOQs to, at least, three orders of magnitude. Recoveries and standard deviations were comparable to those obtained after hydrolysis of amitraz and its metabolites to DMA. Occurrence of amitraz and its metabolites in field-treated pears showed that, seven days after the treatment, DMPF and DMF are the main degradation products. This work reports for the first time the use of a conventional pesticide multiresidue method and LC–ESI-MS/MS for determining amitraz and its metabolites in pears.     

Vapor–liquid equilibria for water + acetic acid + (N,N-dimethylformamide or dimethyl sulfoxide) at 13.33 kPa

Isobaric vapor–liquid equilibrium (VLE) data of the systems acetic acid + N,N-dimethylformamide (DMF), acetic acid + dimethyl sulfoxide (DMSO), DMSO + water, water + acetic acid + DMF, and water + acetic acid + DMSO have been measured at 13.33 kPa by using an improved Rose equilibrium still. The association of acetic acid in vapor phase has been considered, and the nonideality of vapor phase was accounted for using the Hayden–O’Connell (HOC) method. The experimental binary data have been correlated by the NRTL, Wilson and van Laar models. The NRTL model parameters obtained from the binary data have been used to predict the ternary VLE data. The ternary predicted values obtained in this way agree well with the experimental values.     

Mass fragmentation study of the trimethylsilyl derivatives of arctiin,matairesinoside, arctigenin,phylligenin, matairesinol,pinoresinol and methylarctigenin: Their gas and liquid chromatographic analysis in plant extracts

The mass fragmentation patterns and the characteristic behavior of the trimethylsilyl (TMS) derivatives of the dibenzylbutyrolactone-type (arctiin, arctigenin, methylarctigenin, matairesinoside, matairesinol) and those of the diphenylperhydrofurotetrahydrofurane-type (phylligenin, pinoresinol) lignans, obtained by gas chromatography–mass spectrometry (GC–MS), were presented. It was shown that upon acidic hydrolysis the dibenzylbutyrolactone-type lignans are stable while the diphenylperhydrofurotetrahydrofurane-type ones decompose. As a novelty to the field we confirmed that the fragment species of the derivatized lignan glycosides, in the presence of excess hexamethyldisilazane, leaded to their in situ derivatization. Quantification of the selective fragment ions of the TMS derivatives by GC–MS, in respect of the ions found one by one, and concerning the selective fragment ions {SFI(s)} in total, provided acceptable reproducibilities, suitable for quantitation purposes: varying between 1.20% and 6.6% relative standard deviation percentages (RSD%). For characterization of the behavior of various type of lignans, analyses were performed with the untreated and with the trifluoroacetic acid hydrolyzed plant extracts, from the same sample, in parallel, both by GC–MS and by high performance liquid chromatography–mass spectrometry, working in the positive electron ionization mode (HPLC–ESPI-MS). The analysis of lignans in fruit and leaf extracts (obtained from the Arctium, Centaurea and Forsythia plants) was confirmed both by GC–MS and by HPLC–ESPI-MS. Our multicomponent system (including the identification and quantification of sugars, sugar alcohols, and several members of various homologous series of acids, anthraquinones and flavonoids) has been extended to the analysis of lignan glycosides and to the free lignans. Reproducibilities in the quantitation of lignans in plant matrices, as averages on GC and HPLC basis, varied between 0.9% and 11% (RSD). The distribution of the lignan constituents was presented for 5 Arctium, for 8 Centaurea and for 4 Forsythia plant extracts: the total of lignan contents varied between 0.42 and 87.9 mg/g, respectively.     

Sensitive determination of hydrazine in water by gas chromatography–mass spectrometry after derivatization with ortho-phthalaldehyde

A gas chromatography–mass spectrometric (GC–MS) method has been established for the determination of hydrazine in drinking water and surface water. This method is based on the derivatization of hydrazine with ortho-phthalaldehyde (OPA) in water. The following optimum reaction conditions were established: reagent dosage, 40 mg mL⁻¹ of OPA; pH 2; reaction for 20 min at 70 °C. The organic derivative was extracted with methylene chloride and then measured by GC–MS. Under the established condition, the detection and the quantification limits were 0.002 μg L⁻¹ and 0.007 μg L⁻¹ by using 5.0-mL of surface water or drinking water, respectively. The calibration curve showed good linearity with r² = 0.9991 (for working range of 0.05–100 μg L⁻¹) and the accuracy was in a range of 95–106%, and the precision of the assay was less than 13% in water. Hydrazine was detected in a concentration range of 0.05–0.14 μg L⁻¹ in 2 samples of 10 raw drinking water samples and in a concentration range of 0.09–0.55 μg L⁻¹ in 4 samples of 10 treated drinking water samples.     

Towards identification of traditional European and indigenous Australian paint binders using pyrolysis gas chromatography mass spectrometry

We report a pyrolysis GC–MS method capable of analysing Indigenous Australian and European binders typically used in the manufacture of culturally important painted works. Eleven different traditional European binders and ten different Indigenous Australian binders were examined. The method allows discrimination between highly complex and impure lipid, resin, polysaccharide, wax, and protein-based binders. Each was found to have characteristic pyrolysis products that were unique to the binder material, demonstrating the potential for differentiation of these binders on Australian Aboriginal artworks towards identification and conservation of cultural heritage.     

Some theoretical aspects of vibrational fine structure accompanying core ionizations in N2 and CO

Ab initio calculations have been carried out on CO and N₂ and the relevant core hole states with different basis sets to investigate differences in geometries and force constants. From these calculations vibrational band profiles of the core level ESCA spectra for these molecules have been interpreted, obviating the need to rely on data pertaining to the equivalent core species. The agreement with experimental profiles is excellent. The O_1s level of CO which has not been subjected to detailed theoretical analysis previously, is predicted to show substantial vibrational structure in excellent agreement with recently acquired experimental data. The effect of temperature on the band profiles has also been considered. Theoretically derived core binding and relaxation energies of these systems have been investigated both as a function of basis set, and of internuclear distance. Density difference contours have been computed and give a straightforward pictorial representation of the substantial electron reorganizations accompanying core ionizations. Small basis sets with valence exponents appropriate to the equivalent core species when used in hole state calculations describe bond lengths, force constants, core binding energies and relaxation energies with an accuracy comparable to that appropriate to the corresponding extended basis set calculations.