Search results for "Waste"
showing 10 items of 2580 documents
Exploring hand-portable nano-liquid chromatography for in place water analysis: Determination of trimethylxanthines as a use case.
2020
Abstract Analytical performance and optimization of figures of merit of a portable nano liquid chromatograph (NanoLC) with UV detection at 255 nm have been established for in place analysis. Methylxanthines: caffeine, theophylline and theobromine were selected as target analytes. A fast lab method based on IT-SPME coupled on line with capillary liquid chromatograph (CapLC) with diode array detection (DAD) was employed for comparative studies. IT-SPME and solid phase extraction were coupled off-line to NanoLC for improving instrumental parameters, mainly detection capacity and selectivity. IT-SPME or SPE/portable NanoLC based methods were superior in terms of chromatographic resolution and o…
Improvement of the atomic fluorescence determination of mercury by using multicommutation
2002
Atomic fluorescence spectrometry (AFS) determination of Hg has been improved by exploiting the possibilities of the multicommutation approach in order to outline a fully mechanised system which supplies the same sensitivity as the use of continuous measurements, reducing drastically the reagents consumed and waste generation. The use of multicommutation with a simultaneous reduction of the liquid–gas separator volume and the insertion point modification of argon transport gas provides a sensitivity of the AFS measurements of 300 mV ng−1 ml (using a full scale of 1000 mV), a limit of detection (3 s) of 1.3 ng l−1 and relative standard deviation values below 0.1% for 10 independent measuremen…
Determination of Concentration Profiles of Methyl Mercury Compounds in Surface Waters of Polar and other Remote Oceans by GC-AFD
1998
Abstract The concentration of monomethyl mercury (MeHg+) and dimethyl mercury (Me2Hg) was determined in surface sea-water samples of the Antarctic and Arctic Ocean as well as of other remote areas (South Atlantic and South Pacific) during expeditions of the German research vessel “Polarstern”. A purge and trap/gas chromatographic system, equipped with an atomic fluorescence detector (AFD), was used. For the analysis of MeHg+ conversion into the volatile methylethyl mercury by reaction with tetraethyloborate prior to the purging process was carried out. The detection limit for both methylated mercury compounds was 5 pg Hg/L, which allowed their determination in most ocean water samples even …
Resin and fatty-acid analysis by solid-phase extraction coupled to atmospheric pressure chemical ionization–mass spectrometry
2007
Using gas-chromatographic analysis, the suitability of liquid–liquid extraction and solid-phase extraction (SPE) methods was studied for the rapid separation of resin and fatty-acid fractions from papermaking process waters. In the second phase of this study, a novel procedure (correlation coefficient >0.99 and repeatability RSD <8%) for on-line monitoring of selected individual acid components (limits of detection 11–78 µg L−1) by SPE combined with atmospheric pressure chemical ionization–mass spectrometry was developed. The suitability of this technique for quality control of papermaking process waters was tested by means of industrial samples. The method was also found suitable for the a…
Simultaneous detection of three antiviral and four antibiotic compounds in source-separated urine with liquid chromatography
2013
An analytical method for the simultaneous screening of three antiviral agents (nevirapine, zidovudine, lamivudine), four antibiotics (sulfamethoxazole, trimethoprim, ciprofloxacin, rifampicin) and one reference compound (carbamazepine) in human urine was developed. Separation was achieved with a Kinetex XB-C18 (75 × 4.6 mm, 2.6 μm) column after the extraction of pharmaceuticals from urine with SPE. Gradient elution with a mobile phase consisting of acetonitrile and 10 mM KH2 PO4 (pH 2.5), and diode array detection with monitoring at 210 and 264 nm was applied. The developed method was validated in terms of selectivity, linearity, stability and sensitivity. Repeatability (n = 3) and between-…
A clean method for flow injection spectrophotometric determination of cyclamate in table sweeteners
2005
Abstract A flow system based on the multicommutation is proposed for fast and clean determination of cyclamate. The procedure exploits the reaction of cyclamate with nitrite in acidic medium and the spectrophotometric determination of the excess of nitrite by iodometry. The flow system was designed with a set of solenoid micro-pumps to minimize reagent consumption and waste generation. The detection limit was estimated as 30 μmol L −1 (99.7% confidence level) with linear response ranging up to 3.0 mmol L −1 . The coefficient of variation was estimated as 1.7% for a solution containing 2.0 mmol L −1 cyclamate ( n = 20). About 60 samples can be analyzed per hour, consuming only 3 mg KI and 1…
Matrix effects on solid-phase microextraction of organophosphorus pesticides from water
1997
Abstract This study develops a method for solid-phase microextraction (SPME) of eight organophosphorus pesticides, diazinon, fenthion, fenitrothion (sumithion), methyl-parathion, parathion, methyl-trithion, ethion and triazophos, from water. Determination is carried out by gas chromatography with nitrogen-phosphorus detection. To perform the SPME, poly(dimethylsiloxane) and polyacrylate fibers were initially compared on the basis of their absorption capacities for the selected pesticides, and polyacrylate was selected to accomplish the rest of assays. The main factors affecting the SPME process such as memory effect, stirring rate, extraction temperature and absorption-time profile were stu…
Minimizing the impact of sample preparation on analytical results: In-tube solid-phase microextraction coupled on-line to nano-liquid chromatography …
2020
The degradation kinetics and residual levels of the sulfonylurea herbicide tribenuron-methyl (TBM) in different environmental waters were studied using in tube-solid phase microextraction (IT-SPME) coupled on-line to nano-liquid chromatography (nanoLC) and UV diode array detection (DAD). This approach combines the high extraction efficiency of IT-SPME using polymeric coatings reinforced with metal oxide nanoparticles and the high sensitivity attainable by nanoLC, making possible the determination of TBM at low ppb levels (limit of detection, 0.25 ppb) without altering the sample matrix. The present study demonstrated that the preservation of the sample properties is essential to ensure accu…
Analysis of Polycyclic Aromatic Hydrocarbons and Their Oxygen-Containing Derivatives and Metabolites in Soils
2010
Although polycyclic aromatic hydrocarbons (PAHs) have been extensively studied, the knowledge of their oxygen-containing derivatives and metabolites (OPAHs) in soils is limited. We modified and tested an existing analytical protocol involving pressurized liquid extraction of soil followed by fractionation of target compounds into PAHs and OPAHs on a silica gel column and gas chromatography/ mass spectrometry-based separation and quantification. Polycyclic aromatic hydrocarbons and carbonyl-OPAHs were quantified directly after separation on silica gel columns, and hydroxyl/carboxyl-OPAHs were quantified after silylation with N,O-bis(trimethylsilyl)trifluoroacetamide. Recoveries between 78 an…
Zinc removal in anaerobic sulphate-reducing liquid substrate process
2002
Abstract Zinc and sulphate removal from synthetic wastewater was investigated by using four laboratory parallel upflow-mode reactors (referred as R1 to R4; R1 contained carriers to retain biomass, whereas R2–R4 were operated as suspended reactors). All reactors were inoculated with anaerobically digested cow manure. R1 and R2 were first fed with glucose- and sulphate-containing feed for 48 days after which all four reactors were fed with wastewater containing 50 mg l−1 of zinc in R1–R3 and 200 mg l−1 in R4 and operated for 96 days. In all reactors, hydraulic retention time, organic loading rate, and sulphate load were 5–6 d, 0.2–0.4 kg COD m−3 d−1 and 3.3–3.8 g SO4 l−1 d−1, respectively, wh…