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Analytica Chimica Acta (v.702, #1)

Editorial Board (pp. iii).

Ambient ionization mass spectrometry: A tutorial by Min-Zong Huang; Sy-Chi Cheng; Yi-Tzu Cho; Jentaie Shiea (pp. 1-15).

Display Omitted► Ambient ionization technique allows the direct analysis of sample surfaces with little or no sample pretreatment. ► We sort ambient ionization techniques into three main analytical strategies, direct ionization, direct desorption/ionization, and two-step ionization. ► The underlying principles of operation, ionization processes, detecting mass ranges, sensitivity, and representative applications of these techniques are described and compared.Ambient ionization is a set of mass spectrometric ionization techniques performed under ambient conditions that allows the direct analysis of sample surfaces with little or no sample pretreatment. Using combinations of different types of sample introduction systems and ionization methods, several novel techniques have been developed over the last few years with many applications (e.g., food safety screening; detection of pharmaceuticals and drug abuse; monitoring of environmental pollutants; detection of explosives for antiterrorism and forensics; characterization of biological compounds for proteomics and metabolomics; molecular imaging analysis; and monitoring chemical and biochemical reactions). Electrospray ionization and atmospheric pressure chemical ionization are the two main ionization principles most commonly used in ambient ionization mass spectrometry. This tutorial paper provides a review of the publications related to ambient ionization techniques. We describe and compare the underlying principles of operation, ionization processes, detecting mass ranges, sensitivity, and representative applications of these techniques.

Keywords: Ambient; Desorption/ionization; Two-step ionization; Electrospray ionization; Atmospheric pressure chemical ionization

Review of analytical methods for the quantification of iodine in complex matrices by C. Phillip Shelor; Purnendu K. Dasgupta (pp. 16-36).

► We focus on iodine in biological samples, notably urine and milk. ► Sample preparation and the Sandell–Kolthoff method are extensively discussed.Iodine is an essential element of human nutrition. Nearly a third of the global population has insufficient iodine intake and is at risk of developing Iodine Deficiency Disorders (IDD). Most countries have iodine supplementation and monitoring programs. Urinary iodide (UI) is the biomarker used for epidemiological studies; only a few methods are currently used routinely for analysis. These methods either require expensive instrumentation with qualified personnel (inductively coupled plasma-mass spectrometry, instrumental nuclear activation analysis) or oxidative sample digestion to remove potential interferences prior to analysis by a kinetic colorimetric method originally introduced by Sandell and Kolthoff ∼75 years ago. The Sandell–Kolthoff (S–K) method is based on the catalytic effect of iodide on the reaction between Ce⁴⁺ and As³⁺. No available technique fully fits the needs of developing countries; research into inexpensive reliable methods and instrumentation are needed. There have been multiple reviews of methods used for epidemiological studies and specific techniques. However, a general review of iodine determination on a wide-ranging set of complex matrices is not available. While this review is not comprehensive, we cover the principal developments since the original development of the S–K method.

Keywords: Iodine; Urine; Milk; Sandell; Kolthoff; ICP-MS

Comparison of theoretical and experimental models for characterizing solvent properties using reversed phase liquid chromatography by Tao Liu; Ian A. Nicholls; Tomas Öberg (pp. 37-44).

.Display Omitted• A system of nine organic solvents and three chromatographic columns was modeled. • LSER, semi-empirical and theoretical molecular models were evaluated. • The models are useful for solvent optimization and method development in RPLC.Theoretical and experimental quantitative structure–retention relationships (QSRR) models are useful for characterizing solvent properties and column selectivity in reversed phase liquid chromatography (RPLC). The chromatographic behavior of a model analyte, the herbicide atrazine, in a system derived from nine organic solvents and three chromatographic columns was used for developing QSRR models. Multiple linear regression (MLR) and partial least squares regression (PLSR) were used as statistical approaches. The similarities and differences between linear solvation energy relationships (LSER), and semi-empirical and theoretical molecular models were demonstrated. QSRR models show high predictive power, and can successfully predict retention factor (log k) for new solvents. The models are useful for solvent optimization and reducing time for method development in RPLC. The herbicide atrazine can be readily analyzed at a low level, and all three columns provided good resolution, high-performance and symmetrical peaks. The method is suitable for analysis of atrazine in water samples.

Keywords: Global LSER; PLSR; QSRR; RPLC; Atrazine

Immunoassay of C-reactive protein by hot electron induced electrochemiluminescence using integrated electrodes with hydrophobic sample confinement by T. Ylinen-Hinkka; A.J. Niskanen; S. Franssila; S. Kulmala (pp. 45-49).

Display Omitted• C-reactive protein has been determined in the concentration range 0.01–10mgL⁻¹ using an electrochemiluminescence microchip which employs integrated electrodes with hydrophobic sample confinement. • This arrangement enables very simple and fast CRP analysis amenable to point-of-care applications.C-reactive protein (CRP) was determined in the concentration range 0.01–10mgL⁻¹ using hot electron induced electrochemiluminescence (HECL) with devices combining both working and counter electrodes and sample confinement on a single chip. The sample area on the electrodes was defined by a hydrophobic ring, which enabled dispensing the reagents and the analyte directly on the electrode. Immunoassay of CRP by HECL using integrated electrodes is a good candidate for a high-sensitivity point-of-care CRP-test, because the concentration range is suitable, miniaturisation of the measurement system has been demonstrated and the assay method with integrated electrodes is easy to use. High-sensitivity CRP tests can be used to monitor the current state of cardiovascular disease and also to predict future cardiovascular problems in apparently healthy people.

Keywords: Integrated microelectrode chip; Hot electron induced electrochemiluminescence; C-reactive protein; Immunoassay

Speciation analysis of mercury in water samples using dispersive liquid–liquid microextraction combined with high-performance liquid chromatography by Zhongben Gao; Xiaoguo Ma (pp. 50-55).

Display Omitted• Dispersive liquid–liquid microextraction used for preconcentration of mercury. • 1-Hexyl-3-methylimidazolium hexafluorophosphate as extractant for chelates. • Separation and detection is performed by HPLC-DAD. • Extraction time is only 5min. • LODs are comparable with those of other methods.A novel approach for preconcentration and speciation analysis of trace amount of mercury from water samples was proposed by dispersive liquid–liquid microextraction (DLLME) coupled to high performance liquid chromatography with diode array detection (HPLC-DAD). Mercury species (Hg²⁺, methylmercury (MeHg⁺) and phenylmercury (PhHg⁺)) were complexed with dithizone (DZ) to form hydrophobic chelates and then extracted into the fine drops of extraction solvent dispersed in the aqueous sample by dispersive solvent. After extraction, the sedimented phase was analyzed by HPLC-DAD. Some important parameters affecting the DLLME such as extraction solvent and dispersive solvent type and volume, concentration of dithizone solution, sample pH, extraction time and salt effect were investigated. Ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM][PF₆]) was found to be a suitable extractant for the chelates. Under the optimized conditions (extraction solvent: 70μL of ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM][PF₆]); dispersive solvent: 0.75mL of methanol containing dithizone (0.02%, m/v); pH: 4; extraction time: 5min; and without salt addition), the limits of detection for Hg²⁺, MeHg⁺ and PhHg⁺ were 0.32, 0.96 and 1.91μgL⁻¹ (SN⁻¹=3) respectively, and the relative standard deviation (RSD) was between 4.1 and 7.3% ( n=5). Three real water samples (tap water, river water and lake water) spiked with mercury species were detected by the developed method, and the relative recoveries obtained for Hg²⁺, MeHg⁺ and PhHg⁺ were 89.6–101.3%, 85.6–102.0% and 81.3–97.6%, respectively.

Keywords: Mercury speciation; Dispersive liquid–liquid microextraction; High performance liquid chromatography; Ionic liquid

Using an on-line microdialysis/HPLC system for the simultaneous determination of melamine and cyanuric acid in non-dairy creamer by Yu-Ying Chao; Cheuch-Ting Lee; Yu-Tzu Wei; Hwang-Shang Kou; Yeou-Lih Huang (pp. 56-61).

Display Omitted• An economical on-line hollow-fiber microdialysis sampling technique for miniaturizing and simplifying the pretreatment of melamine and cyanuric acid is developed for the first time. • The method allowed the determination of melamine and cyanuric acid in non-dairy creamer at the residue level reaching limits of detection that satisfy regulatory levels. • The volume of perfusate required to extract melamine and cyanuric acid from the sample solution was only 21μL. • The total microdialysis sampling time was 2.1min.The recent revelation of melamine (MEL) contamination in foodstuffs in China has rocked the international public health community. Many food categories have been involved in this scandal, including non-dairy creamer (NDC). In this study, we investigated the use of hollow-fiber microdialysis (MD) sampling coupled on-line with high-performance liquid chromatography (HPLC) as an alternative to sample pretreatment for the direct determination of MEL and its analogue cyanuric acid (CYA) in NDC. After MD sampling, the dialysate was injected on-line into the chromatographic system for analysis of MEL and CYA with UV detection at 203nm. We monitored the effects of various parameters affecting the MD efficiency, namely the characteristics of the MD probe membrane, the flow-rate and the nature of the polarity modifier in the perfusion stream, and the addition of salt in the sample solution. The optimal enrichment efficiency for collecting MEL and CYA from aqueous NDC samples occurred with MD sampling using a hollow polysulfone MD fiber and MeOH as the perfusate at a flow rate of 10μL min⁻¹. The optimized chromatographic conditions involved using a reversed-phase phenyl column and a mobile phase of 5mM phosphate buffer in 10% (v/v) MeOH, buffered at pH 6.5. Detection was linear in the concentration range from 0.02 to 5ppm for MEL and from 2 to 100ppm for CYA, with detection limits of 1ppb for MEL and 30ppb for CYA. The volume of perfusate required to extract MEL and CYA from the NDC solution was only 21μL. The total MD sampling time was 2.1min. This method allows the sensitive, eco-friendly, and rapid determination of MEL and CYA in NDC—a risk food for economically motivated adulteration.

Keywords: Melamine; Cyanuric acid; On-line microdialysis; Liquid chromatography

Determination of eight nitrosamines in water at the ngL⁻¹ levels by liquid chromatography coupled to atmospheric pressure chemical ionization tandem mass spectrometry by Cristina Ripollés; Elena Pitarch; Juan V. Sancho; Francisco J. López; Félix Hernández (pp. 62-71).

Display Omitted• Eight N-nitrosamines in water by LC(APCI)MS/MS QqQ analysis. • Validation at two levels: 10ngL⁻¹ (LOQ) and 100ngL⁻¹ in drinking water. • Developed method applied to different types of water samples. • NDMA was the analyte more frequently detected and at the highest concentration levels.In this work, we have developed a sensitive method for detection and quantification of eight N-nitrosamines, N-nitrosodimethylamine (NDMA), N-nitrosomorpholine (NMor), N-nitrosomethylethylamine (NMEA), N-nitrosopirrolidine (NPyr), N-nitrosodiethylamine (NDEA), N-nitrosopiperidine (NPip), N-nitroso-n-dipropylamine (NDPA) and N-nitrosodi-n-butylamine (NDBA) in drinking water. The method is based on liquid chromatography coupled to tandem mass spectrometry, using atmospheric pressure chemical ionization (APCI) in positive mode with a triple quadrupole analyzer (QqQ). The simultaneous acquisition of two MS/MS transitions in selected reaction monitoring mode (SRM) for each compound, together with the evaluation of their relative intensity, allowed the simultaneous quantification and reliable identification in water at ppt levels. Empirical formula of the product ions selected was confirmed by UHPLC-(Q)TOF MS accurate mass measurements from reference standards.Prior to LC–MS/MS QqQ analysis, a preconcentration step by off-line SPE using coconut charcoal EPA 521 cartridges (by passing 500mL of water sample) was necessary to improve the sensitivity and to meet regulation requirements. For accurate quantification, two isotope labelled nitrosamines (NDMA-d₆ and NDPA-d₁₄) were added as surrogate internal standards to the samples.The optimized method was validated at two concentration levels (10 and 100ngL⁻¹) in drinking water samples, obtaining satisfactory recoveries (between 90 and 120%) and precision (RSD<20%). Limits of detection were found to be in the range of 1–8ngL⁻¹. The described methodology has been applied to different types of water samples: chlorinated from drinking water and wastewater treatment plants (DWTP and WWTP, respectively), wastewaters subjected to ozonation and tap waters.

Keywords: N-nitrosamines; N-nitrosodimethylamine; Liquid chromatography; Tandem mass spectrometry; Atmospheric pressure chemical ionization; Drinking water; Wastewater

Determination of relative rate of spectral events by novel modification of two-dimensional correlation spectroscopy by Mirosław A. Czarnecki (pp. 72-80).

Display Omitted• A new modification of 2D correlation analysis is proposed. • The method facilitates evaluation of the relative rate of spectral variations. • The rate of spectral changes is correlated with the degree of deviation from linearity. • In specific cases this method provides information not accessible from the 2D correlation analysis.Sign of two-dimensional (2D) correlation peaks provides information on sequence of spectral events. This information is related to molecular mechanism of changes in a given system. Recently, few papers addressing the problems with interpretation of the sign of 2D correlation peaks have been published. To overcome these problems, a modification of the generalized 2D correlation method has been proposed. This method compares variations in the dynamic spectrum with a linear change at a reference point. The rates of spectral responses at individual wavenumbers are proportional to magnitudes of the peaks in the slice of asynchronous spectrum at the reference point. This way, analysis of complex 2D contour plots is replaced by a simple examination of one-dimensional (1D) slice spectrum. In spite of reduced ability of the resolution enhancement, in special cases the proposed method provides information not accessible from the classical 2D correlation analysis. At first, the principles of this method are shown with the synthetic data. Next, the influence of spectral separation, band width and position changes on the slice spectrum is evaluated. Finally, the proposed approach is applied to the experimental spectra of two hydrogen-bonded systems.

Keywords: 2D correlation spectroscopy; Rate of spectral events; Simulated spectra; Hydrogen-bonded systems

A new coumarin-based fluorescence turn-on chemodosimeter for Cu²⁺ in water by Zhaojuan Zhou; Na Li; Aijun Tong (pp. 81-86).

Display Omitted• A coumarin-based fluorescence turn on chemodosimeter for Cu²⁺ is facilely synthesized by a one-step reaction. • Cu²⁺ catalyzes the hydrolysis of chemodosimeter with fluorescence signal greatly amplified. • The chemodosimeter exhibits remarkably selective fluorescence enhancement to Cu²⁺ over other metal ions. • Detection of Cu²⁺ can be performed at room temperature with high sensitivity.A highly selective and sensitive coumarin-based chemodosimeter1 for Cu²⁺ in water is reported in this work.1 was designed and facilely synthesized by a one-step reaction with coumarin as a fluorophore and 2-picolinic acid as the binding moiety, which showed very week fluorescence in buffer solution, and its fluorescence was considerably enhanced by the addition of Cu²⁺ at room temperature in 5min. Mechanism study suggested that Cu²⁺ promoted the hydrolysis of1 via the catalytic sensing cycle, generating a highly fluorescent product 7-hydroxycoumarin with fluorescence signal greatly amplified. The probe exhibited remarkably selective fluorescence enhancement to Cu²⁺ over other metal ions at 454nm, with a detection limit of 35nM Cu²⁺. Under optimal condition,1 was successfully used for the determination of Cu²⁺ in fetal equine serum and two water samples.

Keywords: Copper ion; Coumarin-based chemodosimeter; Fluorescence enhancement; Ester hydrolysis

Development of fluorescence imaging-based assay for screening cardioprotective compounds from medicinal plants by Yi Wang; Xiaoping Zhao; Xiumei Gao; Xiaojing Nie; Yingxin Yang; Xiaohui Fan (pp. 87-94).

Display Omitted• Based on cellular-fluorescence imaging technique combined with LC/MS, a rapid approach was constructed to discover active compounds from medicinal plants. • Rhodamine 123 was used as the fluorescent dye to indicate the change of mitochondrial membrane potential. • Good sensitivity and linear range in live cellular fluorescence imaging. • Cardioprotective components from Qi-Shen-Yi-Qi formula were screened and identified.Medicinal plants have been widely recognized as a renewable resource for the discovery of novel leads and drug. In this study, an approach for screening and identification compounds with cardioprotective activity from medicinal plant extracts by cellular-fluorescence imaging technique was developed. It is a cell-based assay for measuring mitochondrial membrane potential changes in H9c2 cardiac muscle cells exposed to H₂O₂ by using a fluorescence automatic microscopy screening platform. Rhodamine 123 was used as the fluorescent dye to indicate the change of mitochondrial membrane potential. The sensitivity and linear range of the proposed approach were evaluated and validated using vitamin C, an antioxidative compound. The method was applied to screen active components with potent cardioprotective effects from a traditional Chinese formula. The potential cardioprotective components were identified by liquid chromatography coupled with mass spectrometry (LC/MS). Moreover, the utility of the proposed approach was further validated by three compounds (salvianolic acid B, protocatechuic aldehyde, and tanshinone II A) identified from the formula which showed cardioprotective effects in a dose-dependent manner. These applications suggested that the proposed rapid and sensitive screening approach offers an efficient way to discover active components or compounds from medicinal plants.

Keywords: Active compounds of traditional Chinese medicine; Bio-guided assay; Live-cell Imaging; Qi-Shen-Yi-Qi formula

An optical sensor based on H-acid/layered double hydroxide composite film for the selective detection of mercury ion by Zhiyong Sun; Lan Jin; Shitong Zhang; Wenying Shi; Min Pu; Min Wei; David G. Evans; Xue Duan (pp. 95-101).

. The H-acid/LDH film used as a chemosensor for the detection of Hg²⁺ exhibits a broad linear response range, low detection limit and high selectivity.Display Omitted• A novel optical chemosensor for Hg(II) was fabricated by using the H-acid/LDH composite material. • The linear response ranges in 1.0×10⁻⁷ to 1.0×10⁻⁵molL⁻¹ with a detection limit of 6.3×10⁻⁸molL⁻¹. • The chemosensor exhibits excellent selectivity and stability for the determination of Hg(II). • The response mechanism is based on the fluorescence quenching resulting from the coordination between Hg²⁺ and H-acid.A novel optical chemosensor was fabricated based on 1-amino-8-naphthol-3,6-disulfonic acid sodium (H-acid) intercalated layered double hydroxide (LDH) film via the electrophoretic deposition (EPD) method. The film of H-acid/LDH with the thickness of 1μm possesses a well c-orientation of the LDH microcrystals confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The fluorescence detection for Hg(II) in aqueous solution was performed by using the H-acid/LDH film sensor at pH 7.0, with a linear response range in 1.0×10⁻⁷ to 1.0×10⁻⁵molL⁻¹ and a detection limit of 6.3×10⁻⁸molL⁻¹. Furthermore, it exhibits excellent selectivity for Hg(II) over a large number of competitive cations including alkali, alkaline earth, heavy metal and transitional metals. The specific fluorescence response of the optical sensor is attributed to the coordination between Hg(II) and sulfonic group in the H-acid immobilized in the LDH matrix, which was verified by NMR spectroscopy and UV–vis spectra. In addition, density functional theory (DFT) calculation further confirms that the coordination occurs between one Hg²⁺ and two O atoms in the sulfonic group, which is responsible for the significant fluorescence quenching of the H-acid/LDH film. The results indicate that the H-acid/LDH composite film can be potentially used as a chemosensor for the detection of Hg²⁺ in the environmental and biomedical field.

Keywords: H-acid; Layered double hydroxide; Intercalation; Composite film; Determination; Mercury

Development of two highly sensitive immunoassays for detection of copper ions and a suite of relevant immunochemicals by Hongwei Zhao; Tiegui Nan; Guiyu Tan; Wei Gao; Zhen Cao; Shuo Sun; Zhaohu Li; Qing X. Li; Baomin Wang (pp. 102-108).

Display Omitted• Two highly sensitive immunoassays for determination of Cu(II) at sub ppb levels. • The heterologous competitive enzyme linked immunosorbent assay for heavy metals. • Haptenated protein directly conjugated with HRP can reduce the loss of HRP activity.Availability of highly sensitive assays for metal ions can help monitor and manage the environmental and food contamination. In the present study, a monoclonal antibody against Copper(II)–ethylenediaminetetraacetic acid was used to develop two sensitive ELISAs for Cu(II) analysis. Cobalt(II)–EDTA–BSA was the coating antigen in a heterologous indirect competitive ELISA (hicELISA), whereas Co(II)–EDTA–BSA–horseradish peroxidase (HRP) was the enzyme tracer in a heterologous direct competitive ELISA (hdcELISA). Both ELISAs were validated for detecting the content of Cu(II) in environmental waters. The ELISA data agreed well with those from graphite furnace atomic absorption spectroscopy. The methods of developing the Cu(II) hicELISA and hdcELISA are potentially applicable for developing ELISAs for other metals. The chelator–protein complexes such as EDTA–BSA and EDTA–BSA–HRP can form a suite of metal complexes having the consistent hapten density, location and orientation on the conjugates except the difference of the metal core, which can be used as ideal reagents to investigate the relationship between assay sensitivity and antibody affinities for the haptens and the analytes. The strategy of conjugating a haptenated protein directly with HRP can reduce the loss of HRP activity during the conjugation reaction and thus can be applicable for the development of ELISAs for small molecules.

Keywords: Copper; Heavy metals; Monoclonal antibody; Enzyme-linked immunosorbent assay; Heterologous immunoassay

Application of 3,4,9,10-perylenetetracarboxylic diimide microfibers as a fluorescent sensing platform for biomolecular detection by Hailong Li; Xuping Sun (pp. 109-113).

Display Omitted► 3,4,9,10-Perylenetetracarboxylic diimide microfibers (PDIMs) can be prepared by sonication. ► PDIMs can serve as a fluorescent sensing platform for DNA and thrombin detection. ► The suggested method has high sensitivity and selectivity down to single-base mismatch. ► A detection limit as low as 15 nM was obtained for DNA detection.In this paper, we report on the use of 3,4,9,10-perylenetetracarboxylic diimide microfibers (PDIMs) as an effective fluorescent sensing platform for DNA detection for the first time. This sensing system exhibits a detection limit as low as 15nmolL⁻¹ and has a high selectivity down to single-base mismatch. The general concept used in this approach is based on adsorption of fluorescently labeled single-stranded DNA (ssDNA) probe by PDIM due to the strong π–π stacking between unpaired DNA bases and PDIM. As a result, the fluorophore is brought into close proximity of PDIM, leading to substantial fluorescence quenching. In the presence of the target, the specific hybridization of the probe with its complementary DNA sequence generates a double stranded DNA (dsDNA) which detaches from PDIM, leading to fluorescence recovery. Its generality of this sensing platform for protein detection is also demonstrated.

Keywords: 3,4,9,10-Perylenetetracarboxylic diimide; Microfiber; Sensing platform; Fluorescence; DNA; Thrombin

Universal optical assays based on multi-component nanoprobes for genomic deoxyribonucleic acid and proteins by Jiang Li; Ying Wan; Lihua Wang; Xinhua Zhu; Yan Su; Di Li; Yun Zhao; Qing Huang; Shiping Song; Chunhai Fan (pp. 114-119).

.Display Omitted• We develop universal optical nanoprobes for both genomic DNA and proteins. • We detect real biological samples by using the nanoprobes. • The limit of detection is less than 10pg template DNA. • 0.1nM thrombin in serum is colorimetrically detected with high specificity.In this report, we developed a universal assay method for both genomic DNA and proteins by using enzyme-based multi-component optical nanoprobes. The nanoprobes are gold nanoparticles assembled with bio-recognizing and signaling elements. We firstly demonstrated that the nanoprobes could detect unpurified asymmetric polymerase chain reaction (PCR) product from genomic DNA of Escherichia coli, with the sensitivity approximately 10 times higher than that of quantitative real-time PCR assay. The limit of detection (LOD) of our nanoprobe-based method is less than 10pg template DNA (target DNA). Using DNA aptamers as recognition elements, we also showed that as few as 0.1nM thrombin could be colorimetrically detected with high specificity. These results indicated that the enzyme-based multi-component nanoprobes have the capability to work with real biological samples, and have the potential in various biological and clinical applications.

Keywords: Multi-component; Nanoprobe; Gold nanoparticles; Assymmetric polymerase chain reaction; Aptamers

Characterization of a novel particle into liquid sampler for analysis of single fluorescent aerosol particles through capillary electrophoresis by Hao Tang; Scott Hiemstra; Jonathan E. Thompson (pp. 120-126).

Display Omitted• Sampling individual aqueous aerosol droplets into a fused silica capillary for CE analysis has been achieved. • Collection efficiencies of >80% have been observed for super-micron particles. • Separation of chemical components in particles has been achieved in 120s. • Dilution of particle material during sampling was highly variable.An approach to sample and analyze single aerosolized droplets (<10nL) of solutions containing fluorescein isothiocyanate (FITC) labeled glycine (GLY) and glutamic acid (GLU) is demonstrated. The sampling approach is based on inertial impaction in which the sample particle is accelerated through a nozzle and directly into a small drop of buffered solution (20mM borate, pH=10) suspended at the end of a coaxial tube of stainless steel and a fused silica capillary. A spherical light scattering cell and laser ( λ=532nm) is used to detect the arrival of particles at the buffered droplet. Upon dissolution and/or mixing, a portion of the sample is injected onto the fused silica capillary for subsequent chemical analysis by capillary electrophoresis (CE) and detection by laser-induced fluorescence (LIF). It was found that the inertial impaction approach sampled particles >1μm diameter with an efficiency of 80% or greater. At 15kV applied potential, the FITC conjugates of GLY and GLU could be resolved in less than 120s allowing qualitative analysis of the contents of single dispersed particles. However, the extent to which the sample is diluted into the buffer droplet varied significantly on a per-particle basis that caused >80% R.S.D. in fluorescence peak heights. This aspect of the method would necessitate the use of internal standards for quantitative analysis of materials present within the particles. It is envisaged that further improvements to the device described may ultimately lead to analysis of the contents of single particles dispersed in earth's atmosphere.

Keywords: Aerosol analysis; Single particle analysis; Particle into liquid sampling; Capillary electrophoresis

Enantioselective determination of triazole fungicide simeconazole in vegetables, fruits, and cereals using modified QuEChERS (quick, easy, cheap, effective, rugged and safe) coupled to gas chromatography/tandem mass spectrometry by Jing Li; Fengshou Dong; Jun Xu; Xingang Liu; Yuanbo Li; Weili Shan; Yongquan Zheng (pp. 127-135).

Display Omitted• Simeconazole enantiomers were baseline separated by gas chromatography. • Optical pure enantiomer was prepared and their elution order was distinguished. • Clean-up/enrichment procedure was based on the modification of QuEChERS method. • Cleanup step was further improved by solid phase extraction (SPE) technology. • Analysis of samples was accomplished by GC–MS/MS.A rapid and effective method for enantioselective determination of simeconazole enantiomers in food products (cucumber, tomato, apple, pear, wheat and rice) has been developed. The enantiomers were resolved by capillary gas chromatography (GC) using a commercial chiral column (BGB-172) and a temperature program from 150°C (held for 1min) and then raised at 10°Cmin⁻¹ to 240°C (held for 10min). This enantioselective gas chromatographic separation was combined with a clean-up/enrichment procedure based on the modification of QuEChERS (quick, easy, cheap, effective, rugged and safe) method. Co-extractives were removed with graphitized carbon black/primary secondary amine (GCB/PSA) solid-phase extraction (SPE) cartridges using acetonitrile:toluene (3:1, v/v) as eluent. Gas chromatography/ion trap mass spectrometry (GC–ITMS) with electron ionization (EI) was then used for qualitative and quantitative determination of the simeconazole enantiomers. Two precursor-to-product ion transitions ( m/ z 121–101 and 195–153) with the best signal intensity were chosen to build the multiple-reaction monitoring (MRM) acquisition method. The limits of detection for each enantiomer of simeconazole in six food products ranged between 0.4 and 0.9μgkg⁻¹, which were much lower than maximum residue levels (MRLs) established by Japan. The methodology was successfully applied for the enantioselective analysis of simeconazole enantiomers in real samples, indicating its efficacy in investigating the environmental stereochemistry of simeconazole in food matrix.

Keywords: Enantioselective gas chromatographic separation; Simeconazole; Quick, easy, cheap, effective, rugged and safe; Solid-phase extraction; Gas chromatography/ion trap mass spectrometry

High temperature–high efficiency liquid chromatography using sub-2μm coupled columns for the analysis of selected non-steroidal anti-inflammatory drugs and veterinary antibiotics in environmental samples by Heba Shaaban; Tadeusz Górecki (pp. 136-143).

Display Omitted• Three sub-2μm columns were coupled at high temperature. • Twenty-four pharmaceuticals could be separated in short analysis time with high efficiency. • The high efficiency HPLC method was applied to the analysis of real wastewater samples. • The method was validated based on linearity, precision, detection and quantification limits, selectivity and accuracy. • Good results were obtained.A high efficiency HPLC method was developed by coupling three sub-2μm columns in series and operating them at high temperature for the separation of selected non-steroidal anti-inflammatory drugs and veterinary antibiotics in environmental samples. The separation was performed at 80°C to reduce the solvent viscosity, thus reducing the column backpressure. The chromatographic performance of high temperature-extended column length HPLC method was used to determine the most widely used non-steroidal anti-inflammatory drugs and veterinary antibiotics such as sulphonamides in wastewater samples. The method could simultaneously determine 24 pharmaceuticals in short analysis time with high efficiency. The method involved pre-concentration and clean-up by solid phase extraction (SPE) using Oasis HLB extraction cartridges. It was validated based on linearity, precision, detection and quantification limits, selectivity and accuracy. Good recoveries were obtained for all analytes ranging from 72.7% to 98.2% with standard deviations not higher than 6%, except for acetaminophen and acetyl salicylic acid, for which low recovery was obtained. The detection limits of the studied pharmaceuticals ranged from 2 to 16μgL⁻¹, while limits of quantification were in the range from 7 to 54μgL⁻¹ with UV detection.

Keywords: HPLC; Environmental analysis; High temperature; Sub-2; μm columns; Non-steroidal anti-inflammatory drugs; Veterinary antibiotics

Comment on “Application of a superoxide (O₂⁻) thermal source (SOTS-1) for the determination and calibration of O₂⁻ fluxes in seawater” by Heller and Croot by Andrew L. Rose; Christopher J. Miller; Manabu Fujii; T. David Waite (pp. 144-145).

Reply to comment on “Application of a superoxide (O₂⁻) thermal sources (SOTS-1) for the determination and calibration of O₂⁻ fluxes in seawater” by Maija I. Heller; Peter L. Croot (pp. 146-147).

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Analytica Chimica Acta (v.702, #1)