Preparative sample collection vessel

The aliquot of digested sample placed in the electrochemical vessel is purged for 15-20 minutes with N2, then it is rapidly transferred and screwed under the cell head of the electrochemical device where the Hg film electrode has already been prepared, tested and rinsed. The electrolytic pre-concentration step during the analytical measurement is carried out by constant potential electrolysis. The deposition potential is set at -0.95 V for Cd and Pb and at -0.85 V for Cu. The deposition time depends on the metal concentration, a time of 20 min normally being sufficient to determine Cd and Pb concentration in samples collected in... 

A similar microwave digestion preparation procedure was used to determine the uranium content and its isotopic composition in soil samples collected in the vicinity of the Tokai-Mura plant in Japan after the criticality accident in 1999. The samples were oven-dried at 80°C to a constant weight and then powdered. Samples were placed in sealed Teflon pressure decomposition vessels with HNO3, HF, and HCIO4 and digested in a microwave oven, then evaporated to dryness and dissolved in 2% HNO3 prior to ICPMS analysis (Yoshida et al. 2001). This analytical method did not require separation on chromatographic columns. 

The coupling of supercritical fluid extraction (SEE) with gas chromatography (SEE-GC) provides an excellent example of the application of multidimensional chromatography principles to a sample preparation method. In SEE, the analytical matrix is packed into an extraction vessel and a supercritical fluid, usually carbon dioxide, is passed through it. The analyte matrix may be viewed as the stationary phase, while the supercritical fluid can be viewed as the mobile phase. In order to obtain an effective extraction, the solubility of the analyte in the supercritical fluid mobile phase must be considered, along with its affinity to the matrix stationary phase. The effluent from the extraction is then collected and transferred to a gas chromatograph. In his comprehensive text, Taylor provides an excellent description of the principles and applications of SEE (44), while Pawliszyn presents a description of the supercritical fluid as the mobile phase in his development of a kinetic model for the extraction process (45). 

In the last several years, on-line extraction systems have become a popular way to deal with the analysis of large numbers of water samples. Vacuum manifolds and computerized SPE stations were all considered to be off-line systems, i.e., the tubes had to be placed in the system rack and the sample eluate collected in a test-tube or other appropriate vessel. Then, the eluted sample had to be collected and the extract concentrated and eventually transferred to an autosampler vial for instrumental analyses. Robotics systems were designed to aid in these steps of sample preparation, but some manual sample manipulation was still required. Operation and programming of the robotic system could be cumbersome and time consuming when changing methods. 

So far the discussion has revolved around completely automated dissolution. Meaning that media is prepared, dispensed into the vessels, tablets dropped, sampled, filtered, collected or read, and lines and vessels washed. This series of events must be reproduced multiple times without human intervention after it has been initiated (Fig. 3). 

Test Preparation Place 40.0 g of sample in a glass-stoppered, round-bottom flask, add 10 mL of water, and cautiously add 30 mL of 5 A potassium hydroxide. Connect a condenser to the flask, and steam-distill, collecting the distillate in a suitable 100-mL graduated vessel containing 10 mL of alcohol. Continue the distillation until the volume in the receiver reaches approximately 95 mL, and dilute the distillate to 100.0 mL with water. 

Experiment 41. — Construct a chlorine generator and prepare chlorine as directed in Exp. 57. Pass the gas into a deep vessel of water until a sample of the liquid smells strongly of chlorine. The delivery tube should reach to the bottom of the vessel of water. Completely fill a flask with a slender neck with this saturated solution of chlorine, cork tightly, and stand in the sunlight. After several hours a small quantity of gas will collect at the top. Test the gas with a glowing match. Repeat the experiment, if the result is not satisfactory. 

Sediment sampling of the seven stations using the CS equipment was carried out by running transects with the survey vessel parallel to, and as close as possible to, the marker buoys. The CS underwater seafloor sediment sampler was pulled at a speed of three knots and, when abreast of each buoy, the sediment collected was recorded as being from that station. The sediment wafers prepared aboard ship from the collected slurries were immediately analyzed by XRF for three elements (Mn, Fe, and Ti) and were stored for further land-based analyses of other elements. A comparison of the elemental content of the sediments collected from the seven stations by box coring and with the use of the CS equipment constituted the basis for ground-truth evaluation of the CS system. 

It also minimizes sample handling, provides fairly clean extracts, expedites sample preparation, and reduces the use of environmentally toxic sol vents.SFE has been applied to the extraction of carcinogenic AAs from soil and sand. The paper studies the possibilities of using MAE and SFE in determination of AAs by HPLC after reduction of the azo colorants. Two SFE pieces of equipment differing in the trapping step (solid-phase trap or solvent collection) were utilized for the extractions. The MAE experiments were then performed with a vessel system with temperature and pressure control. 

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