Figure 3. Correspondence of results obtained with the column RIA procedure and the dextran-coated charcoal method patients on digitoxin therapy is immunologically indistinguishable from the digitoxin in the standards. In other words, the antibody recognizes the digitoxin in clinical specimens and standards as identical. As shown in Table II, acceptable results were obtained in a parallelism study over a sixfold range of dilution. These data indicate that various components in the serum, including potentially cross reacting materials, do not interfere in the test.
A differential pulse polarographic method for the determination of nitrate and nitrite was based upon the enhancement of the ytterbium peak current by both nitrate and nitrite. A detection limit of 14 ppb nitrate or nitrite nitrogen was achieved under ideal conditions. The method was adapted to the analysis of soils and natural waters following interference removal. A relative precision of less than 4% was routinely achieved for analysis of soil samples containing 10 ppm or more nitrate nitrogen. Simultaneous determination of both nitrate and nitrite was possible under certain conditions. Results obtained by this method were compared to results obtained by the nitrate ion-selective electrode method and the phenoldisulfonic acid spectrophotometric method.
15 431 448 20 431 431 acetic acid-chloroform mixture.In almost all cases, 5 ml. of the solvents tested were miscible with 20 ml. of acetic acid-chloroform.Recovery of peroxide was quantitative when as little as 20% by volume of acetic acidchloroform was present in the solvent mixture. It should therefore be possible to determine peroxide groups on polymers and other organic solids if the solution of the material is compatible with the minimum amount of acetic acid-chloroform required for the reaction of the peroxide with iodide.Attempts to determine di-ferf-butyl peroxide by using HC1 to increase the acidity were unsuccessful. Ten milligrams of this peroxide gave a pale yellow 2 hours after solution in 1 to 1 HC1 and the addition of KI.
results, large fluctuations in room temperature should be avoided. When the ultraviolet lamp is on for long periods, the instrument may heat up and require resetting of the reflector. This has been minimized by operating in a temperature-controlled room.Fatigue.The instruments have shown a fatigue of less than 2% when operated for over an hour with a continuous photocurrent of 10 yua. As a measurement involves only a few seconds' exposure of the photomultiplier tube, little difficulty would be expected from occasional samples giving readings of 10 µ&. or more.The rotary sample holder acts as a shutter to prevent long exposures of the photomultiplier to fluorescent light.The monitor photomultiplier tube decreases the dynode voltage if the ultraviolet light in the optical compartment increases so that the maximum anode current is 0.1 µ&. If high level samples are to be run, it is possible to adjust the reflector so that the sensitivity of the photomultiplier is decreased. For
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