Analytica Chimica Acta (v.769, #C)

Application of data fusion techniques to direct geographical traceability indicators by Michele Silvestri; Lucia Bertacchini; Caterina Durante; Andrea Marchetti; Elisa Salvatore; Marina Cocchi (1-9).
Display Omitted► Data fusion is applied to XRPD profiles, metal contents and isotopic ratio 87Sr/86Sr data to characterize soils samples. ► Multivariate curve resolution is used as variable reduction tool for hierarchical data fusion. ► Soil samples differences and similarity were highlighted as well as the linking relations among data blocks.A hierarchical data fusion approach has been developed proposing multivariate curve resolution (MCR) as a variable reduction tool.The case study presented concerns the characterization of soil samples of the Modena District. It was performed in order to understand, at a pilot study stage, the geographical variability of the zone prior to planning a representative soils sampling to derive geographical traceability models for Lambrusco Wines. Soils samples were collected from four producers of Lambrusco Wines, located in in-plane and hill areas. Depending on the extension of the sampled fields the number of points collected varies from three to five and, for each point, five depth levels were considered.The different data blocks consisted of X-ray powder diffraction (XRDP) spectra, metals concentrations relative to thirty-four elements and the 87Sr/86Sr isotopic abundance ratio, a very promising geographical traceability marker.A multi steps data fusion strategy has been adopted. Firstly, the metals concentrations dataset was weighted and concatenated with the values of strontium isotopic ratio and compressed. The resolved components described common patterns of variation of metals content and strontium isotopic ratio. The X-ray powder spectra profiles were resolved in three main components that can be referred to calcite, quartz and clays contributions. Then, a high-level data fusion approach was applied by combining the components arising from the previous data sets.The results show interesting links among the different components arising from XRDP, the metals pattern and to which of these 87Sr/86Sr Isotopic Ratio variation is closer. The combined information allowed capturing the variability of the analyzed soil samples.
Keywords: Multivariate curve resolution; Hierarchical data fusion; X-ray powder diffraction; Soils characterization; Geographical traceability markers;

Stripping voltammetry at micro-interface arrays: A review by Grégoire Herzog; Valerio Beni (10-21).
Display Omitted► Fabrication of arrays of metallic micro-electrodes and arrays of μITIES. ► Some consideration on array design and diffusion phenomena at such interfaces. ► Applications of micro-electrode arrays and μITIES in stripping analysis. ► Some consideration on micro-electrode arrays integration and protection. ► New frontiers/challenges for μITIES.In this article, a comprehensive overview of the most recent developments in the field of stripping voltammetry at regular micro-interfaces (both solid–liquid and liquid–liquid interfaces) is presented. This review will report on the most conventional arrays of metallic micro-electrodes but also on the rapidly growing field of electrochemistry at arrays of micro-interfaces between two immiscible electrolyte solutions (μITIES). The main fabrication methods, together with some design considerations and diffusion phenomena at such interfaces are discussed. Main applications of micro-interface arrays are presented including heavy metals detection at micro-electrode arrays and detection of organic molecules (amino acids, vitamins, peptides and drugs) at the μITIES. Stripping analysis at micro-interface arrays is suitable for the detection of analytes in several real media including water, soil extracts and biological fluids (blood and saliva) with high specificity, sensitivity (detection limits of nM, ppb level) and reliability. Stripping analysis at μITIES and micro-electrode arrays are two complementary approaches that have the advantages of being cost effective, simple to use and easily adaptable to field measurement.
Keywords: Electroanalysis; Micro-electrode arrays; Heavy metal detection; Organic molecules; Interface between two immiscible electrolyte solutions (ITIES);

Display Omitted► Volatility loss of bromine from solution pipetted onto filter paper was ignorable. ► Good linearity of INAA was confirmed within a bromine content range of 10–170 μg. ► Variation of measured concentrations among samples was major source of uncertainty.Accurate measurements of bromine contents in plastic samples were made by the direct comparator instrumental neutron activation analysis (INAA). Individual factors affecting the measurements were comprehensively evaluated and compensated, including the volatility loss of bromine from standard comparators, the background bromine level in the filter papers used for preparation of the standard comparators, nuclear interference, γ-ray spectral interference and the variance among replicates of the samples. Uncertainty contributions from those factors were thoroughly evaluated and included in the uncertainty budgeting of the INAA measurement. 81Br was chosen as the target isotope, and the INAA measurements for bromine were experimentally confirmed to exhibit good linearity within a bromine content range of 10–170 μg. The established method has been applied to the analysis of eight plastic samples: four commercially available certified reference materials (CRMs) of polyethylene and polystyrene and four acrylonitrile butadiene styrene (ABS) samples prepared as the candidate reference materials (KRISS CRM 113-01-012, -013, -014 and -015). The bromine contents of the samples were calculated at three different γ-ray energies and compared, showing good agreement. The results of the four CRMs also showed good consistency with their certified values within the stated uncertainties. Finally, the bromine contents of the ABS samples were determined with expanded uncertainties (at a 95% level of confidence) between 2.5% and 5% in a bromine content range of 25–900 mg kg−1.
Keywords: Bromine; Plastics; Instrumental neutron activation analysis; Certified reference material;

Display Omitted► Omics studies generate massive data obtained from different analytical devices. ► Extracting knowledge from these multiple blocks is challenging. ► A generic methodology for Omics data fusion is proposed.Omics approaches have proven their value to provide a broad monitoring of biological systems. However, as no single analytical technique is sufficient to reveal the full biochemical content of complex biological matrices or biofluids, the fusion of information from several data sources has become a decisive issue. Omics studies generate an increasing amount of massive data obtained from different analytical devices. These data are usually high dimensional and extracting knowledge from these multiple blocks is challenging. Appropriate tools are therefore needed to handle these datasets suitably. For that purpose, a generic methodology is proposed by combining the strengths of established data analysis strategies, i.e. multiple kernel learning and OPLS-DA to offer an efficient tool for the fusion of Omics data obtained from multiple sources. Three real case studies are proposed to assess the potential of the method. A first example illustrates the fusion of mass spectrometry-based metabolomic data acquired in both negative and positive electrospray ionisation modes, from leaf samples of the model plant Arabidopsis thaliana. A second dataset involves the classification of wine grape varieties based on polyphenolic extracts analysed by two-dimensional heteronuclear magnetic resonance spectroscopy. A third case study underlines the ability of the method to combine heterogeneous data from systems biology with the analysis of publicly available data related to NCI-60 cancer cell lines from different tissue origins, which include metabolomics, transcriptomics and proteomics.The fusion of Omics data from different sources is expected to provide a more complete view of biological systems. The proposed method was demonstrated as a relevant and widely applicable alternative to handle efficiently the inherent characteristics of multiple Omics data, such as very large numbers of noisy collinear variables.
Keywords: Omics; Metabolomics; Data fusion; Multiblock; Consensus model; OPLS-DA;

Display Omitted► Studied the loading interaction of HCPT (10-hydroxy camptothecin) on graphene oxide. ► The nature of the interaction between graphene oxide, HCPT and BSA was investigated. ► Studied the HCPT–GO–BSA system with three-way fluorescence spectroscopy and chemometrics. ► A novel BSA biosensor was constructed with improved sensitivity and selectivity.The interaction of graphene oxide (GO), a medicinal drug (10-hydroxy camptothecin (HCPT)), and bovine serum albumin (BSA) was investigated with the aim of developing a method for the analysis of serum albumin proteins. It was demonstrated that HCPT could be readily loaded onto GO via the π–π stacking interaction, and the delivery of HCPT to BSA was improved in the presence of GO; this, in turn, facilitated the binding interaction of HCPT and BSA. Chemometrics methods, multivariate curve resolution-alternating least squares (MCR-ALS) and parallel factor analysis (PARAFAC), were applied to resolve spectral data, and this assisted in the elucidation of the above interaction. GO was found to enhance the fluorescence response of HCPT to BSA, and thus, a low cost fluorescence bio-sensing platform was developed for fluorescence-enhanced detection of BSA based on GO. The satisfactory analytical performance of this biosensor for BSA was attributed to the structure and electronic properties of GO.
Keywords: Graphene oxide; Nano-carrier; Serum albumin; Fluorescence enhancement; Chemometrics; Biosensor;

Display Omitted► A novel bismuth precursor, Bi-dispersed MPTMS xerogel, is proposed. ► EDS analysis showed an excellent distribution of Bi atoms in the material. ► Bi-xerogel/Nafion composite film-modified GC electrodes exhibit low LODs. ► Sensors were applied to the rapid screening of Cd(II) and Pb(II) in water samples.We report for the first time the synthesis of bismuth-modified (3-mercaptopropyl) trimethoxysilane (MPTMS) and its application for the determination of lead and cadmium by anodic stripping voltammetry. Xerogels made from bismuth-modified MPTMS and mixtures of it with tetraethoxysilane, under basic conditions (NH3·H2O), were characterized with scanning electron microscopy, energy dispersive spectroscopy, infrared spectroscopy and electrochemical methods. Bismuth-modified xerogels were mixed with 1.5% (v/v) Nafion in ethanol and applied on glassy carbon electrodes. During the electrolytic reductive deposition step, the bismuth compound on the electrode surface was reduced to metallic bismuth. The target metal cations were simultaneously reduced to the respective metals and were preconcentrated on the electrode surface by forming an alloy with bismuth. Then, an anodic voltammetric scan was applied in which the metals were oxidized and stripped back into the solution; the voltammogram was recorded and the stripping peak heights were related to the concentration of Cd(II) and Pb(II) ions in the sample. Various key parameters were investigated in detail and optimized. The effect of potential interferences was also examined. Under optimum conditions and for preconcentration period of 4 min, the 3σ limit of detection was 1.3 μg L−1 for Pb(II) and 0.37 μg L−1 for Cd(II), while the reproducibility of the method was 4.2% for lead (n  = 5, 10.36 μg L−1 Pb(II)) and 3.9% for cadmium (n  = 5, 5.62 μg L−1 Cd(II)). Finally, the sensors were applied to the determination of Cd(II) and Pb(II) ions in water samples.
Keywords: Bismuth-modified xerogel; Bismuth precursors; Determination of Cd(II) and Pb(II) ions; Stripping voltammetry;

Determination of lead and cadmium in seawater using a vibrating silver amalgam microwire electrode by Zhaoshun Bi; Pascal Salaün; Constant M.G. van den Berg (56-64).
Display Omitted► A vibrating silver amalgam microwire (SAM) is used as electrode in voltammetry. ► The SAM has sufficient sensitivity to determine Pb in uncontaminated seawater. ► The SAM is vibrated during the deposition step to increase the sensitivity. ► The new electrode and method are more sensitive than pre-existing electrodes. ► The limit of detection is 4 pM Pb and 100 pM Cd in acidified seawater.Silver amalgamated electrodes are a good substrate to determine lead (Pb) and cadmium (Cd) in seawater because they have properties similar to mercury but without the free mercury (Hg). Here a silver amalgamated microwire (SAM) electrode is optimised for the determination of Pb and Cd in coastal waters and uncontaminated ocean waters. The SAM was vibrated during the deposition step to increase the sensitivity, and electroanalytical parameters were optimised. The Hg coating required plating from a relatively concentrated (millimolar) solution, much greater (500×) than used for instance to coat glassy carbon electrodes. However, the coating on the ex situ amalgamated electrode was found to be stable and could be used for up to a week to determine trace levels of Pb in seawater of natural pH. The limit of detection square-wave ASV (50 Hz) using the pre-plated SAM electrode was 8 pM Pb using a 1-min plating time at pH 4.5. The limit of detection in pH 2 seawater was 4 pM using a 5-min plating time, and it was 12 pM using a 10-min plating time at natural pH in the presence of air, using a square-wave frequency of 700 Hz. The vibrating SAM electrode was tested on the determination of Pb in reference seawater samples from the open Atlantic (at the 20 pM level), Pacific, and used for a study of Pb in samples collected over 24 h in Liverpool Bay (Irish Sea).
Keywords: Anodic stripping voltammetry; Lead; Cadmium; Seawater; Vibrating microwire electrode; Silver amalgam electrode;

Display Omitted► Investigate the feasibility of bamboo charcoal/Fe3O4 as a novel SPME fiber coating material. ► Establish a SPME method for the enrichment and determination of PBDEs. ► The new coating could be reused for over 100 times without loss of extraction efficiency. ► The novel coating is much less costly than commercial coatings.In this paper, bamboo charcoals were modified using Fe3O4 nanosheets for the first time. The composites, as a novel solid-phase microextraction (SPME) fiber coating, were used for the extraction of seven polybrominated diphenyl ethers (PBDEs) in environmental water samples. The extraction factors (stirring rate, extraction time, and ionic strength) and desorption factors (desorption time and desorption temperature) of the fibers were systematically investigated and optimized. Under optimum conditions, the linear range was 1–1000 ng L−1. Based on the ratio of chromatographic signal to base line noise (S N−1  = 3), the limits of detection (LODs) can reach 0.25–0.62 ng L−1. The novel method was successful in the analysis of PBDEs in real environmental water samples. The results indicate that bamboo charcoal/Fe3O4 as an SPME coating material coupled with gas chromatography–negative chemical ionization-mass spectrometry is an excellent method for the routine analysis of PBDEs at trace levels in environmental water samples.
Keywords: Bamboo charcoal; Fe3O4; Polybrominated diphenyl ethers; Solid-phase microextraction; Gas chromatography–negative chemical ionization-mass spectrometry;

Display Omitted► Micro-extraction procedure was developed for rapid PAE analysis in wine samples. ► Use of the vortex plays an important role in the DLLME procedure. ► No disperser solvent was added for enhancing the phase separation. ► Extractant solvent volume was investigated in blank and real samples. ► Effects of the sale and the alcohol content were studied for optimize the protocol.An Ultrasound-Vortex-Assisted Dispersive Liquid–Liquid Micro-Extraction (USVADLLME) procedure coupled with Gas Chromatography-Flame Ionization Detector (GC-FID) or Gas Chromatography-Ion Trap Mass Spectrometry (GC-IT/MS) is proposed for rapid analysis of six phthalate esters in hydroalcoholic beverages (alcohol by volume, alc vol−1, ≤40%). Under optimal conditions, the enrichment factor of the six analytes ranges from 220- to 300-fold and the recovery from 85% to 100.5%. The limit of detection (LOD) and limit of quantification (LOQ) are ≥0.022 μg L−1 and ≥0.075 μg L−1, respectively. Intra-day and inter-day precisions expressed as relative standard deviation (RSD), are ≤8.2% and ≤7.0%, respectively. The whole proposed methodology has demonstrated to be simple, reproducible and sensible for the determination of trace phthalate esters in red and white wine samples.
Keywords: Vortex shaking; Ultrasound-assisted; Dispersive liquid–liquid micro-extraction; Phthalate esters; Wine;

Display Omitted► New derivatization method of hydrazine with ortho-phthalaldehyde in water.► A simple, rapid and sensitive method by GC–MS. ► The reaction conditions were optimized. ► Very small amount of sample and solvent is needed.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 r 2  = 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.
Keywords: Hydrazine; ortho-Phthalaldehyde derivatization; Water; Gas chromatography–mass spectrometry;

Display Omitted► We demonstrate a technique for ambient spray ionization from nonpolar solvents. ► The technique is mechanistically distinct from extractive electrospray ionization. ► Factorial design experiments, among others, elaborate mechanistic details. ► CF-EDESI expands the application base of conventional ESI.Due to their low polarities and dielectric constants, analytes in solvents such as hexane, chloroform, and ethyl acetate exhibit poor electrospray ionization (ESI) efficiency. These are deemed to be “non-ESI-friendly” solvents. Continuous flow extractive desorption electrospray ionization (CF-EDESI) is a novel ambient ionization technique that was recently developed in our group to manipulate protein charge distributions. Here we demonstrate its potential for ionizing analytes from non-ESI-friendly solvents. This feature makes CF-EDESI attractive to the general analytical community due to its apparent potential in lipidomics, normal phase separations, and hyphenation of mass spectrometry with HPLC-NMR systems. In this context, interest was subsequently initiated to discern mechanistic aspects of CF-EDESI. To achieve this, mechanistic experiments associated with a seemingly similar ambient ionization technique, extractive electrospray ionization (EESI), were emulated to compare CF-EDESI and EESI. Analysis of a series of fatty acids in multiple solvents in the negative ionization mode revealed differences between the two techniques. Whereas EESI has been previously shown to operate via extraction of analytes into the spray solvent, data presented here for CF-EDESI point toward a liquid-liquid mixing process to facilitate ionization. Further, a partial factorial design experiment was performed to evaluate the effects of different experimental variables on signal intensity. Sample flow rate was confirmed to be among the most significant factors to affect sensitivity. As a whole, the work presented provides greater insight into a new ambient ionization process, which exhibits expanded capabilities over conventional ESI; in this case, for direct analysis from non-ESI-friendly solvents.
Keywords: Ambient ionization; Electrospray; Progesterone; Mass spectrometry;

Spray nebulization for sample introduction in ion mobility spectrometry by S. Armenta; A. Gonzálvez; M. Blanco (91-99).
Display Omitted► We have developed a spray nebulization introduction system (SIS) for IMS. ► The system used a concentric nebulizer and a temperature controlled transfer line. ► Qualitative and quantitative capabilities were evaluated. ► The SIS is useful for direct analysis of drugs in biological samples.A new sample introduction system based on spray nebulization has been successfully developed to perform direct analysis of liquid samples by IMS. The system comprises a concentric nebulizer that generates a spray plume which is introduced in the ionization region of the IMS instrument through a temperature controlled transfer line. This system avoids previous problems of direct injection of liquid samples and maintains the countercurrent flow of inert gas necessary for the operation of the IMS instrument. Evaluation of the qualitative and quantitative capabilities of the methodology has been performed after a carefully study of the main variables affecting the spray nebulization and the transport of the analyte molecules through the transfer line. To demonstrate the usefulness of the new sample introduction system, direct analysis of drugs and drug metabolites in saliva or urine samples have been performed, obtaining accurate, reliable and sensitive results. Moreover, analytes with physico-chemical properties that limited the capability of thermal desorption as sample introduction method such as amino acids can be analyzed by using the spray nebulization methodology.
Keywords: Ion mobility spectrometry; Spray nebulization; Sample introduction;

Schematic representation of the proposed mechanism for indirectly detection of salbutamol using the MIP-modified carbon paste electrode.Display Omitted► Nano-sized MIP was prepared by using salbutamol–Cu2+ complex as template. ► Carbon paste electrode was modified with the MIP and used as sulbutamol sensor. ► Voltammetric signal of participant Cu2+ was utilized for salbutamol determination. ► Ultra-trace level detection limit was obtained for salbutamol determination. ► The MIP was also employed for separation of salbutamol from biological samples.Cu2+-mediated salbutamol-imprinted polymer nanoparticles, synthesized by precipitation polymerization, were mixed with graphite powder and n-eicosane in order to fabricate a modified carbon paste electrode. This electrode was then applied for indirect differential pulse voltammetry determination of salbutamol. In the presence of Cu2+ ions, the formed Cu2+–salbutamol complex was adsorbed in to the pre-designed cavities of the MIP particles, situated on the electrode surface. Since the electrochemical signal of salbutamol was intrinsically small, the oxidation peak of the participant Cu2+, after reduction step, was recorded and used as an indication of salbutamol amount, adsorbed in the electrode. Different variables influencing the sensor performance were studied and the best conditions were chosen for the determination purpose. Correlation between the sensor response to salbutamol and its concentration was linear in the range of 1.0 × 10−9–5.5 × 10−8  M. Detection limit was calculated equal to 6.0 × 10−10  M (S/N). Five replicated determination of salbutamol (1 × 10−8  M) resulted in standard error of 3.28%, meaning a satisfactory precision of the determination method. The prepared sensor was applied for real sample analysis. In order to minimize the interference effect, the synthesized polymer was successfully used as a solid phase sorbent for salbutamol extraction, before analysis of real samples by the developed sensor.
Keywords: Salbutamol; Nano-sized imprinted polymer; Cu2+; Carbon paste electrode;

Next generation planar waveguide detection of microcystins in freshwater and cyanobacterial extracts, utilising a novel lysis method for portable sample preparation and analysis by Shauna Devlin; Julie P. Meneely; Brett Greer; Charles Greef; Michael J. Lochhead; Christopher T. Elliott (108-113).
Display Omitted► Sensitive assay for the detection of the most common and toxic microcystin variants. ► Detection of free and cell bound microcystin for a true reflection of toxin content. ► Novel, highly effective lysis method enabling fast and portable disruption of cells. ► Validated to measure microcystins below 1 and 0.1 ng mL−1; free and intracellular. ► Next generation planar waveguide biosensor combining quantification and ease of use.The study details the development of a fully validated, rapid and portable sensor based method for the on-site analysis of microcystins in freshwater samples. The process employs a novel lysis method for the mechanical lysis of cyanobacterial cells, with glass beads and a handheld frother in only 10 min. The assay utilises an innovative planar waveguide device that, via an evanescent wave excites fluorescent probes, for amplification of signal in a competitive immunoassay, using an anti-microcystin monoclonal with cross-reactivity against the most common, and toxic variants. Validation of the assay showed the limit of detection (LOD) to be 0.78 ng mL−1 and the CCβ to be 1 ng mL−1. Robustness of the assay was demonstrated by intra- and inter-assay testing. Intra-assay analysis had % C.V.s between 8 and 26% and recoveries between 73 and 101%, with inter-assay analysis demonstrating % C.V.s between 5 and 14% and recoveries between 78 and 91%. Comparison with LC–MS/MS showed a high correlation (R 2  = 0.9954) between the calculated concentrations of 5 different Microcystis aeruginosa cultures for total microcystin content. Total microcystin content was ascertained by the individual measurement of free and cell-bound microcystins. Free microcystins can be measured to 1 ng mL−1, and with a 10-fold concentration step in the intracellular microcystin protocol (which brings the sample within the range of the calibration curve), intracellular pools may be determined to 0.1 ng mL−1. This allows the determination of microcystins at and below the World Health Organisation (WHO) guideline value of 1 μg L−1. This sensor represents a major advancement in portable analysis capabilities and has the potential for numerous other applications.
Keywords: Microcystin; Planar waveguide; Portable biosensor; Novel lysis; Blue-green algae; Cyanobacteria;

Preparation and application of triangular silver nanoplates/chitosan composite in surface plasmon resonance biosensing by Jia Zhang; Ying Sun; Hua Zhang; Bo Xu; Hanqi Zhang; Daqian Song (114-120).
Display Omitted► Triangular silver nanoplates were prepared and used to amplify the SPR signal. ► Triangular silver nanoplates are preserved by MPA and chitosan polymer. ► The proposed substrate immobilizes antibodies directly without modification. ► The LOQ of present method for analyte is 32 times lower than that based on Au film.This paper reports the utilization of triangular silver nanoplates (TSNPs) to enhance the sensitivity of surface plasmon resonance (SPR) biosensor. TSNPs modified with 3-mercaptopropinic acid (MPA) were simply mixed with chitosan and glutaraldehyde to form TSNPs/chitosan composite. The composite was deposited on Au film as immobilization substrate for SPR biosensor. The novel structures of TSNPs are preserved against etching by MPA and chitosan polymer. Moreover, chitosan cross-linked by glutaraldehyde enables antibody to be immobilized on fabricated substrate directly via Schiff alkali reaction. In the optimized conditions, the resulting biosensor based on TSNPs/chitosan composite shows a satisfactory response to bovine IgG in the concentration range of 0.075–40.00 μg mL−1. While the biosensor based on chitosan without TSNPs shows a response in the concentration range of 0.6–40 μg mL−1 and the biosensor based on Au film shows a response in the concentration range of 2.5–40 μg mL−1. The experiment results show that the sensitivity of SPR biosensor based on TSNPs/chitosan composite was significantly enhanced and the immobilization procedure of antibody was simplified.
Keywords: Triangular silver nanoplate; Chitosan; Surface plasmon resonance; Bovine IgG;

Display Omitted► A 2 g portion of soil sample was enough for trace analysis of OPPs at ng g−1 level. ► Despite low volatility, OPPs could be headspace extracted under mild conditions. ► Ultrasonic agitation showed to provide better results than magnetic stirring.This work describes optimization of headspace single drop micro-extraction for extraction of five organophosphorus pesticides; thionazin, sulfotep, dimethoate, disulfoton and parathion in soil. Ultrasound has also been used successfully to improve and accelerate the extraction of the analytes from the sample. The optimized extraction performance was obtained when the experimental parameters were set as follows; 3.0 μL of octanol as extraction solvent, high ionic strength (20% sodium chloride), 1:1 (w/v) sample dilution with water, extraction temperature at 60 °C for 30 min; applying ultrasound and without any pH adjustment. The optimized method was linear over the calibration range (5–200 and 10–300 for different analytes) with limits of detection of 0.1–2.0 ng g−1. The enrichment factor for OPPs was 1.4–12.7 and the method was also reproducible with the relative standard deviations (RSD%) of 2.1–6.9%.
Keywords: Gas chromatography; Nitrogen-phosphorus detector; Organophosphorus pesticide; Single drop micro-extraction; Ultrasonic assisted extraction;