Aspiration technique

Figure 1 Diagram of the micropipette aspiration technique (modified from Lim et al., 2006). L is the length of extension into the pipette, Rc the inner radius of the pipette and AP the suction pressure.

Gaseous samples are typically taken by means of isolation techniques (using gas pipettes, ampoules, plastic bags, or canisters with walls lined with an inactive polymer) or aspiration techniques (absorption on solid sorbents or in appropriate... 

Atomization of the sample is usually facilitated by the same flame aspiration technique that is used in flame emission spectrometry, and thus most flame atomic absorption spectrometers also have the capability to perform emission analysis. The previous discussion of flame chemistry with regard to emission spectroscopy applies to absorption spectroscopy as well. Flames present problems for the analysis of several elements due to the formation of refractory oxides within the flame, which lead to nonlinearity and low limits of detection. Such problems occur in the determination of calcium, aluminum, vanadium, molybdenum, and others. A high-temperature acetylene/nitrous oxide flame is useful in atomizing these elements. A few elements, such as phosphorous, boron, uranium, and zirconium, are quite refractory even at high temperatures and are best determined by nonflame techniques (Table 2). 

Fig. 106. Aspiration technique With circling movements the I/A handpiece is gently conducted along the edge of the capsulorhexis or the pupil crossing the four quadrants in the anterior chamber...

A basic apparatus similar to the one shown in Figure 16.1 may be used for microscale vacuum distillations. As is the case for simple distillation, this apparatus uses the Hickman head as a means to reduce the length of the vapor path. The major difference to be found when comparing this assembly to one for simple distillation (Technique 14, Figure 14.8) is that the opening to the atmosphere has been replaced by a connection to a vacuum source (top right-hand side). The usual sources of vacuum are the aspirator (Technique 8, Section 8.5), a mechanical vacuum pump, or a "house" vacuum line (one piped directly to the laboratory bench). The aspirator is probably the simplest of these sources and the vacuum source most likely to be available. However, if pressures below 10-20 mm Hg are required, a vacuum pump must be used. 

Geiger S, Jager-Lezer N, Tokgoz S, Seiller M, Grossiord JL. 1999. Characterization of the mechanical properties of a water/oil/water multiple emulsion oily membrane by a micropipette aspiration technique. Colloids Surf A 157 325-332. 

The mechanical properties of the oil membrane in W/O/W emulsions were characterized by an aspiration technique (Geiger et al., 1999). The deform-ability was determined of an individual globule during total or partial flow into a cylindrical glass tube, which was calibrated under well-controlled conditions of aspiration. An analysis of the behavior of the multiple emulsion by a migration of the lipophilic surfactant to the interface between the oily and the external aqueous phases was done. It was shown that the elastic shear modulus and the interfacial tension of the oily membrane increased with the lipophilic surfactant concentration. 

Highly sensitive iastmmental techniques, such as x-ray fluorescence, atomic absorption spectrometry, and iaductively coupled plasma optical emission spectrometry, have wide appHcation for the analysis of silver ia a multitude of materials. In order to minimize the effects of various matrices ia which silver may exist, samples are treated with perchloric or nitric acid. Direct-aspiration atomic absorption (25) and iaductively coupled plasma (26) have silver detection limits of 10 and 7 l-lg/L, respectively. The use of a graphic furnace ia an atomic absorption spectrograph lowers the silver detection limit to 0.2 l-ig/L. 

Fig. 4. Schematic of the Closed Container Sampling technique used in the Baxter PARAMAX analy2er showing (a) the collection tube with bar-coded label being brought into sampling position under the caimula (b) the tube raised so that the caimula has penetrated the stopper (c) the sample sensing probe coming through the caimula to aspirate the exact volume required for each assay and (d) after sampling, where the tube is lowered away from the cannula.

Autologous hematopoietic stem cells are obtained (or harvested ) from bone marrow or peripheral blood. The technique for harvesting autologous hematopoietic cells depends on the anatomic source (i.e., bone marrow or peripheral blood). A surgical procedure is necessary for obtaining bone marrow. Multiple aspirations of marrow are obtained from the anterior and posterior iliac crests until a volume with a sufficient number of hematopoietic cells is collected (i.e., 600-1200 mL of bone marrow). The bone marrow then is processed to remove fat or marrow emboli and usually is infused intravenously into the patient like a blood transfusion. 

Kulkarni M, Desai S, Ajit D, et al. Utility of the thromboplastin-plasma cell-block technique for fine-needle aspiration and serous effusions. Diagn. Cytopathol. 2009 37 86-90. 

Nga ME, Lim G-L, Barbro N, et al. Successful retrieval of fine-needle aspiration biopsy material from previously stained smears for immunocytochemistry a novel technique applied to three soft tissue tumors. Mod. Pathol. 2005 18 728-732. 

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