Qualitative aspects and validation of a screening method for pesticides in vegetables and fruits based on liquid chromatography coupled to full scan high resolution (Orbitrap) mass spectrometry

The analytical capabilities of liquid chromatography with single-stage high-resolution mass spectrometry have been investigated with emphasis on qualitative aspects related to selective detection during screening and to identification. The study involved 21 different vegetable and fruit commodities, a screening database of 556 pesticides for evaluation of false positives, and a test set of 130 pesticides spiked to the commodities at 0.01, 0.05, and 0.20 mg/kg for evaluation of false negatives. The final method involved a QuEChERS-based sample preparation (without dSPE clean up) and full scan acquisition using alternating scan events without/with fragmentation, at a resolving power of 50,000. Analyte detection was based on extraction of the exact mass (±5 ppm) of the major adduct ion at the database retention time ±30 s and the presence of a second diagnostic ion. Various options for the additional ion were investigated and compared (other adduct ions, M + 1 or M + 2 isotopes, fragments). The two-ion approach for selective detection of the pesticides in the full scan data was compared with two alternative approaches based on response thresholds. Using the two-ion approach, the number of false positives out of 11,676 pesticide/commodity combinations targeted was 36 (0.3 %). The percentage of false negatives, assessed for 2,730 pesticide/commodity combinations, was 13 %, 3 %, and 1 % at the 0.01-, 0.05-, and 0.20-mg/kg level, respectively (slightly higher with fully automated detection). Following the SANCO/12495/2011 protocol for validation of screening methods, the screening detection limit was determined for 130 pesticides and found to be 0.01, 0.05, and ≥0.20 mg/kg for 86, 30, and 14 pesticides, respectively. For the detected pesticides in the spiked samples, the ability for unambiguous identification according to EU criteria was evaluated. A proposal for adaption of the criteria was made

Trace analysis of environmental matrices by large-volume injection and liquid chromatography-mass spectrometry

The time-honored convention of concentrating aqueous samples by solid-phase extraction (SPE) is being challenged by the increasingly widespread use of large-volume injection (LVI) liquid chromatography–mass spectrometry (LC–MS) for the determination of traces of polar organic contaminants in environmental samples. Although different LVI approaches have been proposed over the last 40 years, the simplest and most popular way of performing LVI is known as single-column LVI (SC-LVI), in which a large-volume of an aqueous sample is directly injected into an analytical column. For the purposes of this critical review, LVI is defined as an injected sample volume that is ≥10% of the void volume of the analytical column. Compared with other techniques, SC-LVI is easier to set up, because it requires only small hardware modifications to existing autosamplers and, thus, it will be the main focus of this review. Although not new, SC-LVI is gaining acceptance and the approach is emerging as a technique that will render SPE nearly obsolete for many environmental applications.In this review, we discuss: the history and development of various forms of LVI; the critical factors that must be considered when creating and optimizing SC-LVI methods; and typical applications that demonstrate the range of environmental matrices to which LVI is applicable, for example drinking water, groundwater, and surface water including seawater and wastewater. Furthermore, we indicate direction and areas that must be addressed to fully delineate the limits of SC-LVI

[Investigation into the utility of electrospray ionization-mass spectrometry for the determination of the molecular mass of small proteins.]

Abstract niet beschikbaarThis report describes the results of an investigation into the utility of electrospray ionization - mass spectrometry (ESI-MS) for the determination of the molecular mass of small proteins (up to 17 kDa). The molecular mass of four pure proteins, was determined by ESI-MS. From the known molecular mass of the proteins, the accuracy of the method can be estimated. Two methods were applied to calculate the molecular mass from the acquired ESI mass spectra. In terms of accuracy and precision of the measured molecular mass, the two methods were almost equal. The results of this investigation show that an accuracy of about 0.01% and precision of 0.006% can be achieved. The acquisition of the ESI mass spectro required 10 pmol of protein.RIV

[Determination of the appearance of mixed halogenated dibenzo-p-dioxins and furans in the stack gas of an industrial process.]

Abstract niet beschikbaarThis report describes the results of the analysis of brominated and mixed halogenated (Br/Cl) dibenzo-p-dioxins and furans (DD/Fs) in the stack gas of an industrial process in which significant amounts of flame retardants are being used. Stack gas samples have been collected prior and following the after burner gas cleaning facility. PCDD/F levels, expressed in 2,3,7,8 TCDD toxic equivalents (TEQ), as analysed by TNO were 0.20 ng TEQ/m3 ind (before) and 0.05 ng TEQ/m3 ind (after), respectively. Using both negative chemical ionization (NCI) and electron impact (EI)-mass spectrometry, several brominated compounds were found and tentatively identified as bromobiphenyls (BrBs) and bromochloropolyaromatic hydrocarbons (Br/Cl-PAHs). In addition, some 28 monobromo-polychlorinated (Br/Cln, n=3-7) DD/Fs could be demonstrated in low concentrations in both samples. Determination of their isomeric structure failed due to low sample sizes. Estimation of their TEQ value was performed on the basis of the response ratio for monobroom-heptachloor DD/Fs (Br-Cl7-DD/F) and quantified polychloro analogues (Cl8D/F). Assuming a random distribution of the Bratom, and an estimated relative occurrence of Br to Cl of 1:1000 per substituent, the additional BrCln-DD/F TEQ value was estimated to be not greater than approximately 1% of the corresponding PSDD/F-TEQ value.DGM/

Comparison on the analysis of mineral oil in sediment by gas chromatography and infrared spectrometry

Vergelijkend onderzoek is verricht naar de bepaling van minerale olien in sediment en water met behulp van infraroodspectrometrie (IR) en gaschromatografie (GC) conform de NEN-voorschriften 5733 en 6675. Daarnaast zijn modificaties ter verbetering van deze methoden bestudeerd. In een toepassing op sedimentmonsters met een gehalte van circa 0.5-1 g/kg ds, gaf de GC-bepaling gemiddeld een 20 % hoger resultaat (range 6-32%) dan IR. Oorzaken hiervoor zijn niet gevonden. Veranderingen van de bestaande NEN voorschriften zijn uitgevoerd met betrekking tot (1) verwijdering van dissolved organic carbon (DOC) macromoleculaire co-extractanten ; (2) gebruik van pentaan ter vervanging van gehalogeneerde koowaterstoffen als extractiemiddel ; (3) verwijdering van laag tot medium moleculaire polaire stoffen uit extracten door middel van terug-extractie in een verdunde loogoplossing. Geen van de modificaties resulteerde in een significant ander resultaat dan behaald met de normmethode. Op grond hiervan wordt geconcludeerd dat: (1) de huidige voorschriften voorzien in een betrouwbare analyse van minerale olie in sediment en water ; (2) de IR en de GC methode tot goed vergelijkbare resultaten leiden vanaf gehalten >0.2-0.5 mg/kg ; (3) verbetering van de methoden gericht op verlaging van het risico op vals positieve resultaten niet met eenvoudige middelen kan worden bereikt ; (4) pentaan als alternatief extractiemiddel kan worden gebruikt na een eventueel verbod op het gebruik van Freon-113 en ander gehalogeneerde koolwaterstoffen.A comparitive study has been carried out on the analysis of mineral oil in sediment and water samples by gas chromatography (GC) and infrared spectrometry (IR) according to the current standard methods NEN 5733 and 6675. In an application to sediment samples, results obtained with GC analysis were found to be about 20% higher compared to the IR method (range +6 to +32%). Causes for these differences were not found. Additionally, modifications to improve the performance of the NEN-procedures were investigated. Changes comprised (1) repeated removal of co-extracted dissolved organic carbon (DOC) ; (2) the use of pentaine instead of Freon-113 as extraction solvent and (3) alkaline aqueous washing (back-extraction) of extracts to remove small to medium size acidic co-extractants. However, results obtained were not essentially different from those obtained with the standard method. Based on that, the following conclusions were drawn: (1) the present standard procedures can be considered as reliable methods for the analysis of mineral oil in water en sediment samples, (2) the performance of the GC and IR method is comparable in applications above the determination limit of the latter (0.2-.5 mg/kg) ; (3) improvement of the current standards cannot be achieved with relative simple means; (4) pentane is an acceptable alternative for Freon-113 and other halogenated hydrocarbons in case these solvents are banned for analytical use.HIM

Comparison on the analysis of mineral oil in sediment by gas chromatography and infrared spectrometry

A comparitive study has been carried out on the analysis of mineral oil in sediment and water samples by gas chromatography (GC) and infrared spectrometry (IR) according to the current standard methods NEN 5733 and 6675. In an application to sediment samples, results obtained with GC analysis were found to be about 20% higher compared to the IR method (range +6 to +32%). Causes for these differences were not found. Additionally, modifications to improve the performance of the NEN-procedures were investigated. Changes comprised (1) repeated removal of co-extracted dissolved organic carbon (DOC) ; (2) the use of pentaine instead of Freon-113 as extraction solvent and (3) alkaline aqueous washing (back-extraction) of extracts to remove small to medium size acidic co-extractants. However, results obtained were not essentially different from those obtained with the standard method. Based on that, the following conclusions were drawn: (1) the present standard procedures can be considered as reliable methods for the analysis of mineral oil in water en sediment samples, (2) the performance of the GC and IR method is comparable in applications above the determination limit of the latter (0.2-.5 mg/kg) ; (3) improvement of the current standards cannot be achieved with relative simple means; (4) pentane is an acceptable alternative for Freon-113 and other halogenated hydrocarbons in case these solvents are banned for analytical use.Vergelijkend onderzoek is verricht naar de bepaling van minerale olien in sediment en water met behulp van infraroodspectrometrie (IR) en gaschromatografie (GC) conform de NEN-voorschriften 5733 en 6675. Daarnaast zijn modificaties ter verbetering van deze methoden bestudeerd. In een toepassing op sedimentmonsters met een gehalte van circa 0.5-1 g/kg ds, gaf de GC-bepaling gemiddeld een 20 % hoger resultaat (range 6-32%) dan IR. Oorzaken hiervoor zijn niet gevonden. Veranderingen van de bestaande NEN voorschriften zijn uitgevoerd met betrekking tot (1) verwijdering van dissolved organic carbon (DOC) macromoleculaire co-extractanten ; (2) gebruik van pentaan ter vervanging van gehalogeneerde koowaterstoffen als extractiemiddel ; (3) verwijdering van laag tot medium moleculaire polaire stoffen uit extracten door middel van terug-extractie in een verdunde loogoplossing. Geen van de modificaties resulteerde in een significant ander resultaat dan behaald met de normmethode. Op grond hiervan wordt geconcludeerd dat: (1) de huidige voorschriften voorzien in een betrouwbare analyse van minerale olie in sediment en water ; (2) de IR en de GC methode tot goed vergelijkbare resultaten leiden vanaf gehalten >0.2-0.5 mg/kg ; (3) verbetering van de methoden gericht op verlaging van het risico op vals positieve resultaten niet met eenvoudige middelen kan worden bereikt ; (4) pentaan als alternatief extractiemiddel kan worden gebruikt na een eventueel verbod op het gebruik van Freon-113 en ander gehalogeneerde koolwaterstoffen

Electrospray ionization mass spectrometry. Exploration of the applicability

The results of a study into the applicability of electrospray ionization mass spectrometry (ESI-MS) have been described. The potential of the technique for protein and peptide analysis, for structure elucidation of polynuclear aromatic hydrocarbons and for the detection of polar pesticides and macrolide antibiotics, was investigated. ESI-MS was employed with continuous infusion of solutions of peptides and proteins and combined with HPLC for the analysis of low-molecular-weight compounds. Molecular weight determinations of 17 - 66 kDa proteins and 5 kDa peptides were achieved with high accuracy. Pesticides and macrolide antibiotics were determined at low concentration levels by HPLC-ESI-MS. The identification of a metabolite of naphthalene showed the potential of ESI-MS for structure elucidation.Betreft de resultaten van een studie naar de toepasbaarheid van electrospray ionisatie massaspectrometrie (ESI-MS). Er werd onderzoek verricht op het gebied van de eitwit- en peptide-analyse en de bepaling van polaire bestrijdingsmiddelen, macrolide antibiotica en metabolieten van polycyclische aromatische koolwaterstoffen. De techniek werd zowel met continue infusie van peptide- en eiwitoplossingen toegepast als in combinatie met HPLC voor de bepaling van laag-moleculaire verbindingen. De molecuulmassa van enkele eiwitten (17 - 66 kDa) en peptiden (5 kDa) kon met grote nauwkeurigheid bepaald worden. Bestrijdingsmiddelen en macrolide antibiotica werden op laag concentratieniveau bepaald met behulp van HPLC-ESI-MS. De identificatie van een naftaleenmetaboliet gaf de mogelijkheden van ESI-MS aan bij de structuuropheldering

Investigation to the occurrence of biominated or mixed bromo/chloro dibenzodioxins and furans in cow's milk in the deposition area of a waste incinerator

Abstract niet beschikbaarThis report describes the results of a preliminary investigation on the occurrence of polybrominated and mixed bromo/chloro dibenzodioxins and furans in cow's milk in the deposition area of the waste incinerator "Afvalverwerking Rijnmond" (AVR). The investigation was carried out in a large pooled cow's milk sample containing polychlorodibenzodioxins and furans (PCDD/F) at a level of 8.14 pg toxic equivalents (TEQ/g) milk fat. The sample was considered to be representative for a two months milk production of five dairy farms in the Lickebaert area North of the incinerators. Analyses were performed by gas chromatography/negative ion chemical ionization mass spectrometry (GC/NCI-MS) as an initial screening method to the presence of any brominated or chlorinated compounds, followed by structure analysis using electron impact GCMS. Four compounds could be identified of which the structures resembled with polybromodibenzofurans and were tentatively identified as: two isomers of tribromodibenzofuran, one isomer of tetrabromodibenzofuran and one pentabromodibenzofuran, respectively. From comparison with authentic standards it follwed that none of the identified compounds had the 2,3,7,8-substitution pattern and consequently may be considered as not extremely toxic. On the basis of these findings, it is expected that none of the tentatively identified compounds may not significantly contribute to the increased TEQ values in cow's milk due to the presence of PCDD/Fs. Parallel to the milk sample a pooled seafood sample was investigated. Two compounds could be identified as positional isomers of the tetrabromodibenzodioxin and tetrabromodibenzofuran congener groups, respectively, both not having a 2,3,7,8-substitution pattern.HIMH HIGB VV

Electrospray ionization mass spectrometry. Exploration of the applicability

Betreft de resultaten van een studie naar de toepasbaarheid van electrospray ionisatie massaspectrometrie (ESI-MS). Er werd onderzoek verricht op het gebied van de eitwit- en peptide-analyse en de bepaling van polaire bestrijdingsmiddelen, macrolide antibiotica en metabolieten van polycyclische aromatische koolwaterstoffen. De techniek werd zowel met continue infusie van peptide- en eiwitoplossingen toegepast als in combinatie met HPLC voor de bepaling van laag-moleculaire verbindingen. De molecuulmassa van enkele eiwitten (17 - 66 kDa) en peptiden (5 kDa) kon met grote nauwkeurigheid bepaald worden. Bestrijdingsmiddelen en macrolide antibiotica werden op laag concentratieniveau bepaald met behulp van HPLC-ESI-MS. De identificatie van een naftaleenmetaboliet gaf de mogelijkheden van ESI-MS aan bij de structuuropheldering.The results of a study into the applicability of electrospray ionization mass spectrometry (ESI-MS) have been described. The potential of the technique for protein and peptide analysis, for structure elucidation of polynuclear aromatic hydrocarbons and for the detection of polar pesticides and macrolide antibiotics, was investigated. ESI-MS was employed with continuous infusion of solutions of peptides and proteins and combined with HPLC for the analysis of low-molecular-weight compounds. Molecular weight determinations of 17 - 66 kDa proteins and 5 kDa peptides were achieved with high accuracy. Pesticides and macrolide antibiotics were determined at low concentration levels by HPLC-ESI-MS. The identification of a metabolite of naphthalene showed the potential of ESI-MS for structure elucidation.RIV