Assessment of the determination of heavy metals in organic soil improvers by ICP–OES

Directive 86/278/EEC sets maximum levels of heavy metals in sewage sludge used in agriculture to regulate the risk of using these organic soil improvers. The assessment of the compliance of soil improvers with this legislation should be supported on measurements with adequately low uncertainty. This work presents a strategy for assessing the performance of the determination of aqua regia extractable Cu, Zn and Cr in organic soil improvers and urban sewage sludges following EN 13650 standard. The measurement procedure validation involves checking the adequacy of the linear weighted regression model for ICP–OES calibration, the determination of the limit of quantification, the assessment of measurement repeatability, intermediate precision and trueness, and the evaluation of the measurement uncertainty using the differential approach. Routine tests quality control, including the estimated measurement uncertainty, is checked through the analysis of control standards, equivalent to calibrators, and reference materials from proficiency tests. Since the estimated relative expanded uncertainty is smaller than the defined target value (40 %), measurements are fit for assessing compliance of the mass fraction of heavy metals in organic soil improvers with the council directive.     

Development of a miniature dielectric barrier discharge–optical emission spectrometric system for bromide and bromate screening in environmental water samples

Dielectric barrier discharge (DBD) at atmospheric pressure provides an efficient radiation source for the excitation of bromine and it is used for the first time for optical emission spectrometric (OES) detection of bromide and bromate. A portable DBD–OES system is developed for screening potential pollution from bromide and bromate in environmental waters. Bromide is on-line oxidized to bromine for in-situ generation of volatile bromine. Meanwhile, a helium stream carries bromine into the DBD micro-plasma for its excitation at a discharging voltage of 3.7 kV and optical emission spectrometric detection with a QE65000 charge-coupled device (CCD) spectrometer in the near-infrared spectral region. Similarly, the quantification of bromate is performed by its pre-reduction into bromide and then oxidized to bromine. The spectral characteristics and configuration of the DBD micro-plasma excitation source in addition to the oxidation vapor generation of bromine have been thoroughly investigated. With a sampling volume of 1 mL, a linear range of 0.05–10.0 mg L⁻¹ is obtained with a detection limit of 0.014 mg L⁻¹ by measuring the emission at 827 nm. A precision of 2.3% is achieved at 3 mg L⁻¹ bromide. The system is validated by bromine detection in certified reference material of laver (GBW10023) at mg L⁻¹ level, giving rise to satisfactory agreement. In addition, it is further demonstrated by screening trace bromide and bromate as well as spiking recoveries in a series of environmental water samples.     

Titania sol–gel-derived tyrosinase-based amperometric biosensor for determination of phenolic compounds in water samples. Examination of interference effects

For detection of phenolic compounds in environmental water samples we propose an amperometric biosensor based on tyrosinase immobilized in titania sol-gel. The analytical characteristics toward catechol, p-cresol, phenol, p-chlorophenol, and p-methylcatechol were determined. The linear range for catechol determination was 2.2 x 10(-7)-1.3 x 10(-5) mol L(-1) with a limit of detection of 9 x 10(-8) mol L(-1) and sensitivity 2.0 x 10(3) mA mol(-1) L. The influence of sample matrix components on the electrode response was studied according to Plackett-Burman experimental design. The potential interferents Mg(2+), Ca(2+), HCO3(-), SO4(2-), and Cl(-), which are usually encountered in waters, were taken into account in the examination. Cu(2+) was also taken into account, because CuSO(4) is sometimes added to a water sample, as a preservative, before determination of phenolic compounds. It was found that among the ions tested only Mg(2+) and Ca(2+) did not directly affect the electrode response. The developed biosensor was used for determination of catechol in spring and surface water samples using the standard addition method.     

Direct μ-flow injection isotope dilution ICP-MS for the determination of heavy metals in oil samples

The determination of trace elements in oil samples and their products is of high interest as their presence significantly affects refinery processes and the environment by possible impact of their combustion products. In this context, inductively coupled plasma mass spectrometry (ICP-MS) plays an important role due to its outstanding analytical properties in the quantification of trace elements. In this work, we present the accurate and precise determination of selected heavy metals in oil samples by making use of the combination of μ-flow direct injection and isotope dilution ICP-MS (ICP-IDMS). Spike solutions of ⁶²Ni, ⁹⁷Mo, ¹¹⁷Sn and ²⁰⁶Pb were prepared in an organic solvent, mixed directly with the diluted oil samples and tested to be fit for purpose for the intended ID approach. The analysis of real samples revealed strong matrix effects affecting the ICP-MS sensitivity, but not the isotope ratio measurements, so that accurate results are obtained by ICP-IDMS. Typical relative standard deviations were about 15% for peak area and peak height measurements, whereas the isotope ratios were not significantly affected (RSD < 2%). The developed method was validated by the analysis of a metallo-organic multi-element standard (SCP-21, typically applied as a calibration standard) and the standard reference material SRM1084a (wear metals in lubricating oil). The obtained results were in excellent agreement with the certified values (recoveries between 98% and 102%), so the proposed methodology of combining μ-flow direct injection and ICP-IDMS can be regarded as a new tool for the matrix-independent, multi-element and reliable determination of trace elements in oil and related organic liquids.     

Speciation of heavy metals in environmental water by ion chromatography coupled to ICP–MS

Biogenic (e.g. phytochelatins, porphyrins, DOM) as well as anthropogenic (e.g. NTA, EDTA, phosphonates) chelators affect the mobility and cycling of heavy metals in environmental waters. Since such chelators can form strongly bound anionic heavy metal complexes that are stable and highly mobile, anion-exchange chromatography coupled to ICP-MS was investigated. A narrow bore HPLC system was connected to a micro concentric nebuliser for in-line sample introduction. A new chromatographic procedure based on a synthetic hydrophilic quaternary ammonium anion exchanger in combination with nitrate as a strong eluent anion, and gradient elution, provided high separation selectivity and a large analytical window. Low detection limits (nmol L(-1)) were achieved by on-column matrix removal and sample preconcentration. This allowed the method to be successfully applied to different environmental research areas. In ecotoxicological studies of heavy metal effects on algae low concentrations of metal EDTA complexes were determined in nutrient solutions without interference from high (buffer) salt concentrations. In groundwater, infiltrated by a polluted river, mobile metal EDTA species were observed. In river water of different pollution levels beside CuEDTA other anionic Cu-complexes were found in nmol L(-1) concentrations.     

Analytical development for analysis of pharmaceuticals in water samples by SPE and GC–MS

An analytical procedure involving solid-phase extraction (SPE) and gas chromatography–mass spectrometry (GC–MS) has been developed for determination of pharmaceutical compounds (aspirin, caffeine, carbamazepine, diclofenac, ketoprofen, naproxen, ibuprofen, clofibrate, clofibric acid, and gemfibrozil) in a variety of aqueous samples (wastewater and surface water). After filtration, samples were extracted and concentrated using C₁₈ or HLB cartridges, depending on the type of compound. Sample storage conditions were checked and optimized to ensure preservation of the pharmaceutical substance, taking into consideration environmental sampling conditions. For most of the pharmaceuticals monitored, recovery was in the range 53 to 99% and the variability was below 15% for the complete procedure, with limits of detection ranging from 0.4 to 2.5 ng L⁻¹, depending on the compound. The methods were successfully applied to monitoring of pharmaceutical contamination of the Seine estuary. Concentrations varied from several dozens of nanograms per liter for surface waters to several hundreds of nanograms per liter for wastewaters.     

Determination of polybrominated diphenyl ethers in water and soil samples by cloud point extraction-ultrasound-assisted back-extraction-gas chromatography–mass spectrometry

A novel and efficient analytical methodology is proposed for extracting and preconcentrating polybrominated diphenyl ethers (PBDEs) from samples of environmental interest prior gas chromatography–mass spectrometry (GC–MS) analysis. It is based on the induction of micellar organized medium by using a non-ionic surfactant (Triton X-114) to extract the target PBDEs. To enable coupling the efficient extracting technique with GC analysis, ultrasound-assisted back-extraction (UABE) into an organic solvent was required. Several factors, including surfactant type and concentration, equilibration temperature and time, ionic strength, pH and buffers nature and concentration were studied and optimized over the extraction efficiency of the proposed technique. Under optimal experimental conditions, the target analytes were quantitatively extracted achieving an enrichment factor of 250 when 10 mL aliquot of ultrapure water spiked with PBDE-standard mixture (10 pg mL⁻¹ each PBDE) was extracted. Method detection limits (MDLs) calculated with aqueous PBDEs solutions as three times the signal-to-noise ratio (S/N), ranged from 1 to 2 pg mL⁻¹ with RSDs values ≤8.5% (n = 5). The coefficients of estimation of the calibration curves obtained following the proposed methodology were ≥0.9987 and linear range of all PBDEs was 4–150 pg mL⁻¹. The proposed methodology was validated by carrying out a recovery study by spiking the samples at two different concentration levels of PBDEs (10 and 50 pg mL⁻¹ for waters samples). Recoveries values in the range of 96–106% for water samples were obtained showing satisfactory robustness of the method for analyzing PBDEs in water samples. The proposed methodology was applied for the analysis of PBDEs: 2,2′,4,4′-tetraBDE (BDE-47), 2,2′,4,4,5-pentaBDE (BDE-99), 2,2′,4,4,6-pentaBDE (BDE-100) and 2,2,4,4′,5,5′-hexaBDE (BDE-153) in water samples, including drinking, lake, river water and soil samples. Significant quantities of PBDEs were not found in the analyzed samples.     

In-sample acetylation-non-porous membrane-assisted liquid–liquid extraction for the determination of parabens and triclosan in water samples

A procedure for the determination of seven parabens (esters of 4-hydroxybenzoic acid), including the distinction between branched and linear isomers of propyl- and butyl-parabens and triclosan in water samples, was developed and evaluated. The procedure includes in-sample acetylation-non-porous membrane-assisted liquid–liquid extraction and large volume injection–gas chromatography–ion trap–tandem mass spectrometry. Different derivatisation strategies were considered, i.e. post-extraction silylation with N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide and in situ acylation with acetic anhydride (Ac₂O) and isobutylchloroformate. Moreover, acceptor solvent and the basic catalyser of the acylation reaction were investigated. Thus, in situ derivatisation with Ac₂O and potassium hydrogenphosphate (as basic catalyser) was selected. Potassium hydrogenphosphate overcomes some drawbacks of other basic catalysers, e.g. toxicity and bubble formation, while leads to higher responses. Subsequently, other experimental variables affecting derivatisation–extraction yield such as pre-stirring time, salt addition and volume of Ac₂O were optimised by an experimental design approach. Under optimised conditions, the proposed method achieved detection limits from 0.1 to 1.4 ng L⁻¹ for a sample volume of 18 mL and extraction efficiencies, estimated by comparison with liquid–liquid extraction, between 46% (for methyl- and ethyl-parabens) and 110% (for benzylparaben). The reported sample preparation approach is free of matrix effects for parabens but affected for triclosan with a reduction of ≈ 40% when wastewater samples are analysed; therefore, both internal and external calibration can be used as quantification techniques for parabens, but internal standard calibration is mandatory for triclosan. The application of the method to real samples revealed the presence of these compounds in raw wastewater at concentrations up to 26 ng mL⁻¹, the prevalence of the linear isomer of propylparaben (n-PrP), and the coexistence of the two isomers of butylparaben (i-BuP and n-BuP) at similar levels.     

Whole-cell optical biosensor for mercury — operational conditions in saline water

The present study demonstrates the influences of chlorides, fluorides and bromides of potassium and sodium on the growth and Hg²⁺-induced bioluminescence of bioreporter Escherichia coli ARL1. In a Luria-Bertani medium (LB), cell growth was inhibited by concentrations of sodium and potassium fluorides above 0.2 mol L^?1. The addition of NaCl increased cell tolerance to the toxic effects of fluorides and bromides. Lag periods of 10 h and more were observed for cultivations in LB without NaCl and with halides (NaCl, KCl, NaBr, KBr, NaF and KF) at concentrations lower than 0.06 mol L^?1. In a phosphate buffer (PB), the bioluminescence of E. coli ARL1, induced with HgCl₂, was increased by the addition of NaCl, KCl, NaBr, KBr, NaF and KF (concentration of 0–0.25 mol L^?1). In a saline phosphate buffer (PBS), the maxima of induced bioluminescence declined to 50 %, in the case of NaF (0.12 mol L^?1), and to zero for KF. An addition of tryptone to the induction medium increased induced light emission ten-fold. Concentrated artificial sea water (ASW) (70–100 % ASW) inhibited bioluminescence induction. The new detection assay with E. coli ARL1 made possible the detection of 0.57 µL^?1 of HgCl₂ in double-diluted artificial sea water (25 % ASW).     

Direct analysis of solid samples by GFAAS – determination of trace heavy metals in barytes

Solid sampling graphite furnace atomic absorption spectroscopy (SS-GFAAS) has been used for the determination of traces of heavy metals (Cd, Pb, Cu, Cr, Ni, V and As) in barytes over a wide concentration range, e.g. Cd from 0.023 to 27.0 μg/g and Pb from 1.54 to 3509 μg/g.The necessity of determining heavy metals in commercial barytes (naturally occurring barium sulfate), a mineral important to the oil industry because of its use in drilling muds, is discussed. The problems presented by the analysis of this difficult matrix are elegantly solved by using SS-GFAAS for the direct determination of heavy metals. A high-performance graphite furnace AAS with D₂-background correction system and a transversely heated graphite atomizer was used for the investigations. The spectrometer was combined with a mechanical sampling module and an ultramicrobalance. The transfer of solid samples (sample weights 0.031–0.686 mg) into the atomizer was carried out by using an optimized graphite platform as the sample carrier. Calibration curve techniques and standard addition methods were employed using external standards (CRMs). Problems associated with signal deformations like multiple peaks, tailing or shoulders are also discussed and possibilities to solve the problems are given. The influence of the homogeneity of solid samples on the precision and accuracy are shown in a real example. The results obtained by SS-GFAAS were compared with results by other methods like X-ray fluorescence spectroscopy (XRF) and flame AAS after aqua regia microwave extraction. This study has demonstrated that SS-GFAAS is a very powerful and easy-to-use method for quick and accurate analysis of barytes. Received: 9 November 1998 / Revised: 29 January 1999 / Accepted: 2 February 1999     

Effective liquid–liquid extraction method for analysis of pyrethroid and phenylpyrazole pesticides in emulsion-prone surface water samples

The distribution of pyrethroid and phenylpyrazole pesticides in the water environment has raised public concerns because of their potential risks to ecosystem and human health. However, co-extraction of emulsifier type compounds (by liquid–liquid extraction, LLE) present in environmental samples can present a challenge for quantifying typically low concentrations of pesticides. Several methods were evaluated for breaking emulsions in problematic environmental surface water samples extracted by LLE using methylene chloride. Target pesticides included 11 typical pyrethroid and phenylpyrazole pesticides commonly used in agricultural and landscape insect pest control. The most effective method was selected for validation in fortification studies with GC-ECD analysis. The average recoveries of spiked pyrethroid and phenylpyrazole pesticides were 88.2–123.4% for water samples with moderate emulsions and 93.0–117.4% for water samples with severe emulsions. Recoveries of the pesticides ranged 81.0–126.4% (water samples with moderate emulsions) and 95.9–110.6% (water samples with severe emulsions) for lowest fortification level (5–20 ng L⁻¹), 88.2–123.4% (water samples with moderate emulsions) and 93.0–117.4% (water samples with severe emulsions) for middle fortification level (10–40 ng L⁻¹), and 90.2–119.9% (water samples with moderate emulsions) and 91.2–105.9% (water samples with severe emulsions) for highest fortification level (50–200 ng L⁻¹). Relative standard deviations of pesticide recoveries were usually <10%. Results indicate that this method is a robust and reproducible option for LLE of pyrethroid and phenylpyrazole pesticides from emulsion-prone surface water samples.     

Analysis of nitrobenzene compounds in water and soil samples by graphene composite-based solid-phase microextraction coupled with gas chromatography–mass spectrometry

In this work, solid-phase microextraction coupled with gas chromatography–mass spectrometry was developed to determine trace levels of nitrobenzene compounds in water and soil samples. Graphene was chosen as the extraction material and its composite was coated on a stainless steel wire through sol–gel technique for the solid phase microextraction. The key parameters influencing the extraction efficiency were optimized. Under the optimal conditions, the linearity for the compounds was observed in the range of 0.02–15.0 mg/L for water samples, and 0.2–60.0 mg/kg for soil samples, with the correlation coefficients（r） of 0.9966–0.9987. The limits of detection of the method were 0.0025–0.005 mg/L for water samples, and 0.02–0.04 mg/kg for soil samples. The recoveries for the spiked samples were in the range of 72.0%–113.2%, and the precision, expressed as the relative standard deviations, was less than 12.1%.     

Application of ethyl chloroformate derivatization for solid-phase microextraction–gas chromatography–mass spectrometric determination of bisphenol-A in water and milk samples

A simple and rapid analytical method based on in-matrix ethyl chloroformate (ECF) derivatization has been developed for the quantitative determination of bisphenol-A (BPA) in milk and water samples. The samples containing BPA were derivatised with ECF in the presence of pyridine for 20 s at room temperature, and the non-polar derivative thus formed was extracted using polydimethylsiloxane solid-phase microextraction (SPME) fibres with thicknesses of 100 μm followed by analysis using gas chromatography–mass spectrometry. Three alkyl chloroformates (methyl, ethyl and isobutyl chloroformate) were tested for optimum derivatisation yields, and ECF has been found to be optimum for the derivatisation of BPA. Several parameters such as amount of ECF, pyridine and reaction time as well as SPME parameters were studied and optimised in the present work. The limit of detection for BPA in milk and water samples was found to be 0.1 and 0.01 μg L⁻¹, respectively, with a signal-to-noise ratio of 3:1. The limit of quantitation for BPA in milk and water was found to be 0.38 and 0.052 μg L⁻¹, respectively, with a signal-to-noise ratio of 10:1. In conclusion, the method developed was found to be rapid, reliable and cost-effective in comparison to silylation and highly suitable for the routine analysis of BPA by various food and environmental laboratories.     

Stir-bar-sorptive extraction and ultra-high-performance liquid chromatography–tandem mass spectrometry for simultaneous analysis of UV filters and antimicrobial agents in water samples

Stir-bar-sorptive extraction (SBSE) with liquid desorption (LD) and ultra-high-performance liquid chromatography–electrospray ionization triple-quadrupole tandem mass spectrometry (UHPLC–(ESI)MS–MS) were used for analysis of six personal care products in environmental water: four UV filters (2,2-dihydroxy-4-methoxybenzophenone, benzophenone-3, octocrylene, and octyldimethyl-p-aminobenzoic acid) and two antimicrobial agents (triclocarban and triclosan). Experimental conditions that affect SBSE-LD sorption efficiency (extraction time and temperature, sample pH, and ionic strength) and desorption efficiency (solvent, temperature, and time) were optimized. The method proved to be sensitive—a 50-mL sample was used to determine these compounds in environmental waters at trace levels. The detection limits of the analytical method were 2.5 ng L⁻¹ for river water and 5–10 ng L⁻¹ for effluent and influent sewage water. In river waters, benzophenone-3 was found at levels from 6 ng L⁻¹ to 28 ng L⁻¹ and triclosan at levels <LOQ. Benzophenone-3 was found between 75 and 127 ng L⁻¹ in influent sewage, whereas concentrations of benzophenone-3 and triclosan were commonly below 25 ng L⁻¹ in effluent sewage.     

Iron analysis in atmospheric water samples by atomic absorption spectroscopy (AAS) in water–methanol

To distinguish between Fe(II) and Fe(III) species in atmospheric water samples, we have adapted an analytical procedure based on the formation of a specific complex between Fe(II) and ferrozine (FZ) on a chromatographic column. After elution of Fe(III), the Fe(II) complex is recovered with water–methanol (4:1). The possibility of trace iron measurements in this complex medium by graphite-furnace atomic-absorption spectrometry has been investigated. A simplex optimization routine was required to complete the development of the analytical method.     

Homogeneous liquid–liquid microextraction via flotation assistance for rapid and efficient determination of polycyclic aromatic hydrocarbons in water samples

In this work, a rapid, simple and efficient homogeneous liquid–liquid microextraction via flotation assistance (HLLME-FA) method was developed based on applying low density organic solvents without no centrifugation. For the first time, a special extraction cell was designed to facilitate collection of the low-density solvent extraction in the determination of four polycyclic aromatic hydrocarbons (PAHs) in water samples followed by gas chromatography-flame ionization detector (GC-FID). The effect of different variables on the extraction efficiency was studied simultaneously using experimental design. The variables of interest in the HLLME-FA were selected as extraction and homogeneous solvent volumes, ionic strength and extraction time. Response surface methodology (RSM) was applied to investigate the optimum conditions of all the variables. Using optimized variables in the extraction process, for all target PAHs, the detection limits, the precisions and the linearity of the method were found in the range of 14–41 μg L⁻¹, 3.7–10.3% (RSD, n = 3) and 50–1000 μg L⁻¹, respectively. The proposed method has been successfully applied to the analysis of four target PAHs in the water samples, and satisfactory results were obtained.     

Online solid phase extraction LC–MS/MS method for the analysis of succinate dehydrogenase inhibitor fungicides and its applicability to surface water samples

A sensitive and selective analytical method, based on online solid phase extraction coupled to LC–MS/MS, was developed and validated to determine traces of several recently introduced fungicides in surface water and wastewater. The list of target analytes included eight succinate dehydrogenase inhibitors (bixafen, boscalid, fluopyram, flutolanil, fluxapyroxad, isopyrazam, penflufen, and penthiopyrad), and two other fungicides with different modes of action, fenpyrazamine and fluopicolide. Detection and quantification limits in various matrices were in the range of 0.1 to 2 and 0.5 to 10 ng/L, respectively. Moderate signal suppression was observed in surface water (≤15 %) and wastewater (≤25 %) and was well compensated by the selected internal standard. The intra- and inter-day precisions were generally <10 and <20 %, respectively. The applicability of the method was demonstrated in a study on the occurrence of fungicides in the river Glatt, Switzerland, that drains a catchment area of 419 km² with a substantial proportion of agricultural land. Of the studied compounds, only boscalid and fluopicolide were detected in flow-proportional weekly composite samples, generally at low concentrations up to 15 and 5 ng/L, respectively. While fluopicolide was detected in only 30 % of the samples above the LOD of 0.5 ng/L, boscalid was detected in all samples analyzed between March and October 2012. Graphical Abstract

Concentration of the fungicides boscalid and fluopicolide in flow-proportional weekly-composite watersamples from River Glatt, Switzerland in 2012     

Accurate mass screening of pharmaceuticals and fungicides in water by U-HPLC–Exactive Orbitrap MS

The use of pharmaceuticals in livestock production is a potential source of surface water, groundwater and soil contamination. Possible impacts of antibiotics on the environment include toxicity and the emergence of antibiotic resistance. Monitoring programs are required to record the presence of these substances in the environment. A rapid, versatile and selective multi-method was developed and validated for screening 43 pharmaceutical and fungicides compounds, in surface and groundwater, in one single full-scan MS method, using benchtop U-HPLC-Exactive Orbitrap MS at 50,000 (FWHM) resolution. Detection was based on calculated exact masses and on retention time. Sample volume, pH conditions and solid-phase extraction (SPE) sample clean-up conditions were optimized. In the final method, 74 % of the compounds had recoveries higher than 80 %, 15 % of the compounds had recoveries between 60 % and 80 %, and 7 % of the compounds had recoveries between 40 % and 50 %. One of the compounds (itraconazole) had a recovery lower than 10 % and nystatin was not detected. The level of detection was 10 ng L(-1) for 61 % of the compounds, 50 ng L(-1) for 32 % and 100 ng L(-1) for 5%. In-house validation, based on EU guidelines, proves that the detection capability CCβ is lower than 10 ng L(-1) (for β error 5 %) for 37 % of the compounds, lower than 50 ng L(-1) for 35 % of the compounds and lower than 100 ng L(-1) for 14 % of compounds. This study demonstrates that the ultra-high resolution and reliable mass accuracy of Exactive Orbitrap MS permits the detection of pharmaceutical residues in a concentration range of 10-100 ng L(-1), applying a post target screening approach, in the multi-method conditions.