Search results for "Gradation"
showing 10 items of 1275 documents
A Fully Automated Assembly Using Solenoid Valves for the Photodegradation and Chemiluminometric Determination of the Herbicide Chlorsulfuron
2005
Abstract This paper presents a new photochemiluminescent system for the determination of chlorsulfuron in water samples. The light from a low‐pressure mercury lamp is used as a clean, reproducible, and inexpensive “reagent” for the derivation of the pesticide, performed in glycine buffer at pH 9.5. Then, the photo‐products from irradiation are oxidized by permanganate in sulfuric acid solution. The oxidation reaction was favored by using high temperatures. A comparative study and discussion about the use of polyphosphoric acid instead of sulfuric acid in the oxidation reaction is also presented. The use of solenoid valves allows for the easy, complete automation of the process with low samp…
FI-on line photochemical reaction for direct chemiluminescence determination of photodegradated chloramphenicol.
2002
Abstract A new, simple, clean and selective flow injection strategy based on the tandem photochemical reaction-chemiluminescence detection was applied to the determination of chloramphenicol. The determination is based on the on-line photodegradation of the drug in a glycine buffer at pH 8.8 by using a photoreactor consisting of 697 cm×0.5 mm PTFE tubing helically coiled around an 8 W low-pressure mercury lamp. Photodegradated chloramphenicol is detected by direct chemiluminescence of resulting photo-fragments and their subsequent reaction with potassium permanganate in sulfuric acid medium as oxidant. The method allows the chemiluminescence determination of compounds which do not exhibit n…
Chemiluminometric photo-induced determination of Strychnine in a Multicommutation flow assembly
2007
This paper deals on the determination of Strychnine, a potent and dangerous pesticide and the analytical procedure is based on the photo-induced chemiluminescence of the pesticide by means of the Multicommutation continuous-flow methodology. Small segments of the pesticide solution were sequentially alternated with segments of the solution for adjusting the suitable medium for the photodegradation. The required time of UV irradiation was obtained by stopped-flow during 150 s; then, the resulting solution formed alternated segments with the oxidizing solution containing 5 × 10−3 mol l−1 Ce(IV) in 0.6 mol l−1 nitric acid. The calibration range, from 2 μg l−1 to 50 mg l−1, resulted in a linear…
Enhanced flow-injection–chemiluminometric determination of sulphonamides by on-line photochemical reaction
2003
Abstract The viability of the tandem photochemical reaction-chemiluminescence detection has been studied for an heterogeneous group of sulphonamides (sulphamethoxazole, sulphadiazine, sulphamerazine, sulphamethoxypyridazine, sulphacetamide, sulphadimidine, sulphanilamide, sulphathiazole and sulphaguanidine) using sulphamethoxazole (whose chemiluminescent behaviour has not been previously reported) as a test substance. The ‘on-line’ photochemical-reaction of sulphonamides provides an enhancing influence on the chemiluminometric response of the drugs during their oxidation by potassium permanganate in sulphuric acid medium (sulphamethoxazole, sulphacetamide, sulphadimidine and sulphanilamide …
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…
Flow injection biamperometric determination of chloramphenicol and related nitro compounds by on-line chemical photodegradation
2000
Abstract An unsegmented continuous-flow assembly for the determination of chloramphenicol is proposed. The determination is based on the on-line photodegradation of the drug in an NH4+/NH3 buffer at pH 10.4 by using a photoreactor consisting of a 697 cm long × 0.8 mm ID piece of PTFE tubing coiled around an 8 W low-pressure mercury lamp. Photodegraded chloramphenicol is detected by photolytic cleavage of nitrite from the parent compound as well as by organic oxidizing photofragments, and their subsequent reaction with iodide ion, which is monitored biamperometrically. Triiodide thus formed is detected in excess iodide solution by polarizing two platinum electrodes at 100 mV. The calibration…
Photo-induced chemiluminescence-based determination of diphenamid by using a multicommuted flow system
2007
This manuscript deals with the application of molecular connectivity calculations to predict the photo-induced chemiluminescent behaviour of the family of herbicides grouped as amides. Several compounds of this group were theoretically studied by means of a general discriminant equation formerly obtained, being 18 of them (plus eight from the chloroacetanilide sub-group) predicted with a high probability as photo-induced chemiluminescent. Empirical confirmation of the chemiluminometric behaviour was performed with some few commercially available amide herbicides. On the basis of these results, a new multicommutation-photo-chemiluminescent method is proposed for the determination of the diph…
Diagnosis of pregnancy-associated venous thromboembolism - position paper of the Working Group in Women’s Health of the Society of Thrombosis and Hae…
2016
Venous thromboembolism (VTE) is a major cause of maternal morbidity during pregnancy and the postpartum period. However, because there is a lack of adequate study data, management strategies for pregnancy-associated VTE must be deduced from observational stu-dies and extrapolated from recommendations for non-pregnant patients. In this review, the members of the Working Group in Women's Health of the Society of Thrombosis and Haemostasis (GTH) have summarised the evidence that is currently available in the literature to provide a practical approach for treating pregnancy-associated VTE. Because heparins do not cross the placenta, weight-adjusted therapeutic-dose low molecular weight heparin …
XRF analysis to identify historical photographic processes: The case of some Interguglielmi Jr.’s images from the Palermo Municipal Archive
2017
Abstract In the early period, even though professional photographers worked with similar techniques and products, their artistic and commercial aims determined different choices and led them to follow different, often personal, recipes. For this reason, identification of the techniques through date and name of the photographer or through some visual features like colour, tonality and surface of the image layer, often needs further investigation to be proved. Chemical characterization, carried out in a non or micro destructive way, can be crucial to provide useful information about the original composition, degradation process, realization technique, in obtaining an indirect dating of the ph…
Efficient Nucleophilic Degradation of an Organophosphorus Pesticide “Diazinon” Mediated by Green Solvents and Microwave Heating
2019
An efficient strategy for the degradation of organophosphate pesticide Diazinon was investigated. In this work, ionic liquids, bio-based solvents, and two conventional organic solvents were used as reaction media. Kinetics studies by means of half-life (t1/2,h) were followed by 31P NMR and the products analyzed by GC-MS, HPLC-MS and NMR techniques. These results have shown that t1/2 values in ionic liquids were the lowest and also they were able to activate two electrophilic centers in Diazinon, whilst degradation in bio-based solvents occurred slowly by only an aromatic pathway. In addition, a study to estimate the influence of green activation techniques was carried out by using Ultrasoun…