Drying samples, liquid

In the direct insertion technique, the sample (liquid or powder) is inserted into the plasma in a graphite, tantalum, or tungsten probe. If the sample is a liquid, the probe is raised to a location just below the bottom of the plasma, until it is dry. Then the probe is moved upward into the plasma. Emission intensities must be measured with time resolution because the signal is transient and its time dependence is element dependent, due to selective volatilization of the sample. The intensity-time behavior depends on the sample, probe material, and the shape and location of the probe. The main limitations of this technique are a time-dependent background and sample heterogeneity-limited precision. Currently, no commercial instruments using direct sample insertion are available, although both manual and h ly automated systems have been described. ... 

The particle size analyzer, based on laser light diffraction, consists of a laser source, beam expander, collector lens, and detector (Fig. ] 3.45). The detector contains light diodes arranged to form a radial diode-array detector. The particle sample to be measured can be blown across the laser beam (dry sample), or it can be circulated via a measurement cell in a liquid suspension. In the latter case, the beam is direaed through the transparent cell. 

The confirmatory procedure should be developed for the same tissues for which the determinative procedure was developed, preferably using the same extraction procedure as used for the determinative portion of the method. Storage and stability data are necessary for dried or liquid sample extracts if MS analyses of the confirmatory samples are to be conducted in a laboratory other than the laboratory of sample preparation. Analytes present in sample extracts must be stable long enough for the samples to be shipped to the MS laboratory and analyzed. 

At the end of the experiment, the stirrer and heaters were switched off and the autoclave allowed to cool to room temperature. The autoclave was opened and the liquid contents were removed by suction. The basket was detached and the catalyst removed into a beaker which was placed in an ultrasonic bath. 10 cm of dichloroethane was added to the beaker which was agitated in the ultrasonic bath for 15 mins. The solvent was removed by suction filtration, the catalyst was washed with portions of acetone until the washings were colourless and the catalyst was air dried. The liquid product was transferred into a glass jar which was sealed under nitrogen and kept in a refrigerator until required. In order to have a sufficient amount of catalyst for a duplicate experiment on the five contacts and to allow a sample of catalyst to be... 

From all these results dinophysistoxin-3 was assigned to 7-0-acyl dinophysistoxin-1 (III). Dinophysistoxin-3 was extremely vulnerable to acid, alkali and exposure to air. Leaving a dried sample, even at low temperature, easily resulted in the loss of toxicity and production of multiple spots on TLC. The presnece of this component in the mussel and two species of the short-necked clams was evidenced by liquid chromatographic analysis of intact toxin and by gas chromatographic analysis of dinophysistoxin-1 and fatty acids in the hydrolyzates. 

All sample types, except for dried blood and bile spots (which can be sent at room temperature), should be kept frozen until analysis. Reliable results, particularly for short-chain acylcarnitine species, for any sample, liquid or dried on filter paper, can not be achieved following long-term storage at ambient temperatures [55]. 

However, care must be exercised in using molecular sieves for drying organic liquids. Appreciable amounts of impurities were formed when samples of acetone, 1,1,1-trichloroethane and methyl-r-butyl ether were dried in the liquid phase by contact with molecular sieves 4A (Connett Lab.Practice 21 545 1972). Other, less reactive types of sieves may be more suitable but, in general, it seems desirable to make a preliminary test to establish that no unwanted reaction takes place. For the principles of synthesis and identification see R. Szostak Molecular Sieves, Chapman Hall, London 1988, and for structure, synthesis and properties see R.Szostak Handbook of Molecular Sieves, Chapman Hall 1992. 

Liquid Samples. Liquid samples such as plasma or milk are shell-frozen in the lyophilizer flasks using a mixture of crushed dry ice and 2-propanol. They are then dehydrated in the same way as the solid samples. The resulting material, which is brittle and spongy and easily broken up, is then pressed into cans and sealed. No preservative is added to the dried materials they can be stored indefinitely at room temperature. Approximately 2 liters of fresh milk can be dried and compressed into one can. 

In contrast, as shown in Figure 4.5, the Si/Ti ratio of the samples synthesized by the method A drastically increased during the period of crystal growth the solid samples in the induction period were obtained directly by drying the liquid at 100 °C... 

Currently, high-performance liquid chromatography (HPLC) combined with atmospheric pressure ionization (API) triple-quadrupole mass spectrometry (MS) is the predominate quantitative technique used in modem pharmaceutical bioanalysis. The key technological achievement in API-MS was the efficient ionization in a liquid stream and transference of ions from atmosphere to vacuum. Of the API approaches developed, electrospray ionization (ESI) is the most commonly used. ESI provides an efficient means of soft ionization amenable to most molecules encountered in a dmg discovery setting. An alternative soft ionization approach is the use of desorption ionization (DI) techniques. The major distinguishing feature of DI techniques is that ions are typically produced from dried samples. 

The method of analysis involves extraction of 1 L of aqueous sample (liquid-liquid extraction) or 25 g of soil (sonication or Soxhlett extraction or supercritical fluid extraction) or an appropriate amount of the sample with methylene chloride. The extract is dried, concentrated to a volume of 1 mL, and injected into a capillary GC column for separation and detection by FID. For quantitation, the area or height response of all peaks eluting between C-10 and C-28 are summed and compared against the chromatographic response of the same peaks in a 2 Fuel or Diesel Oil standard. A 10-component n-alkanes mixture containing even numbered alkanes ranging between 10 and 28 C atoms has been recommended as an alternative calibration standard. These alkanes occur in all types of diesel oils, and each compound constitutes approximately a 1% total mass of diesel fuel, i.e., 1 g of diesel fuel contains about 10 mg each of any of the above alkanes. Therefore, when using the latter as a calibration standard, the result must be multiplied appropriately by 100. 

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