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

Identity, presence and signification of chlorination products of humuc acid in aqueous medium.

During chlorination of cyanoethanoic acid at pH=10 a number of compounds is formed. The compounds were confirmed with synthetic standards with GC and mass-spectrometry (MSD). The endproducts of the reaction at pH=10 were dichloroacetic acid, dichloromalonic acid and a small amount of trichloroacetic acid. Intermediates were dichloroacetonitrile (DCAN) and N-chloroacetamides. These N-chloroacetamides were previously errorneously identified as hydroxamoyl chlorides. Mutagenicity tests showed that only DCAN is mutagenic. The total of the mutagenicity of the chlorination mixture can be declared by this compound. In samples drinking water derived from plants where chlorine is used DCAN is detected (0.04-1.05 mug/L). At this concentration level the health risks are very small. The strong bacterial mutagen 'MX' is detected in chlorinated river water (Rhine and Meuse). In these samples the accounted contribution of MX on the measured mutagenic activity (Salmonella typhimurium TA 100) is appr. 20%. In samples drinking water no MX is detected. By chlorination with a higher dose than used for postdesinfection the compound can be formed. It seems to be that the most important mutagens will be organic acids isolated at low pH. The application of chlorine during the production of drinking water has to be limited for emergencies to maintain the bacteriologic quality.DGM/DWB-D Trouwborst

The chlorination of cyanoethanoic acid in aqueous medium

Bij de chlorering van aminozuren, aanwezig in humuszuren, in waterig milieu ontstaan cyaanalkaanzuren. Vooral cyaanazijnzuur reageert snel met chloor ; bij pH 10 werden naast zuren meerdere intermediairen gevormd, deze werden als amides en hydroxamoylchlorides geidentificeerd. In een vooronderzoek bleek de mutageniteit van het reactiemengsel aanzienlijk te zijn. In dit onderzoek zijn de verschillende verbindingen gesynthetiseerd om de identificatie te bevestigen en de mutageniteit van de afzonderlijke stoffen te testen. Bij de reactie van cyaanazijnzuur met chloor in waterig milieu bij verschillende pH waarden werden dichloorazijnzuur, dichloormalonzuur en in mindere mate trichloorazijnzuur gevormd als eindprodukt. Bij pH 4 en 7 werd alleen dichlooracetonitril als intermediair gedetecteerd, terwijl bij pH 10 ook nog N-chloor dichlooraceetamide, N-chloor trichlooraceetamide en N-chloor dichloormalonmonoamide werden aangetoond. Door een ongebruikelijke reactie van N-chlooramides met diazomethaan waarbij imidaten werden gevormd zijn deze ten onrechte als gemethyleerde amides en hydroxamoylchlorides geidentificeerd. De mutageniteit van het reactiemengsel kon worden verklaard door de hoeveelheid dichloroacetonitril die werd aangetroffen.DGM/DWB-D /Trouwborst

Determination of halo-acetic acids, chlorite and chlorate in drinking water.

A method was developed to determine halo-acetic acids with a detection limit of 0.1 mug/L. Halo-acetic acids were determined in samples drinking water derived from surface- and bankfiltrated water however, not in drinking water derived from groundwater. Halo-acetic acids were found in chlorinated and non-chlorinated drinking waters. The total acetic-acid concentrations were in the range of 0.1-14.7 mug/L. In chlorinated drinking water the total amount of these acids was always higher than in non-chlorinated drinking water. Brominated acetic-acids accounted for 65% of the total acid concentration showing that brominated compounds form a large part of the halogenated products. In a few samples river water and drinking water chlorite and chlorate were analysed. These compounds were found in river water and in drinking water derived from bank filtrated water. The results of the analyses have to be confirmed. The chlorate in the drinking water samples can be originated in the raw water source and/or as a pollution in sodium-hypochlorite solution used for chlorination. More research has has to be done to examine this phenomenon into more detail.DGM/DWB-

Investigation of the mutagenic action of chlorination products of cyanoethanoic acid in watery environment

Door de reactie van humuszuur met chloor in water worden cyaanalkaanzuren gevormd. Van deze zuren reageert vooral cyaanazijnzuur snel met chloor. Het blijkt dat de reactieprodukten mutageen zijn voor Klebsiella pneumoniae (fluctuatietest) doch niet of nauwelijks voor Salmonella typhimurium TA100 (Ames test) in afwezigheid van metabolische activering. De volgende stoffen werden op mutageniteit onderzocht: aceetamide, chlooraceetamide, dichlooraceetamide, trichlooraceetamide, N-chloor-dichlooraceetamide, N-chloor-trichlooraceetamide, broomaceetamide, dichlooracetonitril, aceetaladoxim, dichlooraceto-hydroxamoylchloride, trichlooracetohydroxamoylchloride, dichloorazijnzuur en trichloorazijnzuur. In de fluctuatietest werd alleen een mutagene werking van chlooraceetamide, dichlooraceetamide, trichlooracetonitril, aceetaldoxim en vermoedelijk van broomaceetamide op Klebsiella pneumoniae gevonden. In de Ames-test werd alleen een mutagene werking met trichlooraceetamide dichlooracetonitril op de Salmonella typhimurium stammen TA100 en TA98 gevonden. Aceetaldoxim was alleen mutageen voor stam TA100. Op geleide van de resultaten van het mutageniteitsonderzoek en de analytische chemie werd een herzien reactieschema opgesteld. De mutagene werking van het mengsel van reactieprodukten wordt door dichlooracetonitril veroorzaakt.DGM/DWB-

A gradient search and column generation approach for the build-pack planning problem with approved vendor matrices and stochastic demand

10.1080/00207540903049381International Journal of Production Research48195783-5807IJPR

Nanoparticle tracking analysis of gold nanoparticles in aqueous media through an inter-laboratory comparison

In the field of nanotechnology, analytical characterization plays a vital role in understanding the behavior and toxicity of nanomaterials (NMs). Characterization needs to be thorough and the technique chosen should be well-suited to the property to be determined, the material being analyzed and the medium in which it is present. Furthermore, the instrument operation and methodology need to be well-developed and clearly understood by the user to avoid data collection errors. Any discrepancies in the applied method or procedure can lead to differences and poor reproducibility of obtained data. This paper aims to clarify the method to measure the hydrodynamic diameter of gold nanoparticles by means of Nanoparticle Tracking Analysis (NTA). This study was carried out as an inter-laboratory comparison (ILC) amongst seven different laboratories to validate the standard operating procedure’s performance and reproducibility. The results obtained from this ILC study reveal the importance and benefits of detailed standard operating procedures (SOPs), best practice updates, user knowledge, and measurement automation