Nanoliter

J. B. Knight, A. Vishwanath, J. P. Brody, R. H. Austin. Hydrodynamic focussing on a silicon chip mixing nanoliters in microseconds. Phys Rev Lett 50 3863-3866, 1998. 

L. A. Holland and J. W. Jorgenson, Separ ation of nanoliter samples of biological amines by a comprehensive two-dimensional microcolumn liquid chr omatography system . Awn/. Chem. 67 3275-3283 (1995). 

For these reasons, the plastic tip, or the siliconed glass tip have been used for micro measurements. With a plastic tip, there is no limit to the size of the specimen which may be sanq>led. For example, it is possible to sample amounts of the order of nanoliters, provided one resorted to a micromanipulator. While the clinical chemist has not availed himself generally of this technique, the physiologist, has for many years, been measuring samples from within a single cell, or from perhaps, a renal tubule, so that the sample can then be subsequently analyzed. It awaits only an intelligent manufacturer to adapt the micromanipulator as a routine tool in the Pediatric... 

Laboratory. This will eventually come about because this is the practical solution to the sampling of minute specimens. The micromanipulator, may be adapted to a sampler-diluter where amounts of the order of a few nanoliters are being sampled followed through the same tip by a diluting solution of several microliters. 

Figure 21, Ultramicro instrument for Na and K estimation. Nanoliter specimen is placed on wire (inset) and is then vaporized in the glow discharge with helium (American Instrument Co,),...

Extracolumn dispersion is a major problem for the packed fused silica capillary columns with internal diameters less than 0.35 mm. Peak standeunl deviations will be in the submicroliter range and extensive equipment modification is required for operation under optimum conditions. A reasonable compromise is to esploy injection voluMs of a few hundred nanoliters or less with detector volumes of a similar or preferably smaller size. This demands considerable ingenuity on behalf of the analyst since, as... 

D.L. Olson, T. L. Peck, A. G. Webb, R. L. Magin, J. V. Sweedler 1995, (High resolution microcoil H-NMR for mass limited nanoliter-volume samples), Science 270, 1967... 

Another approach has been to immobilize proteins within arrays of microfabricated polyacrylamide gel pads (Arenkov et al., 2000). Nanoliters of protein solutions are transferred to 100 x 100 x 20-pM gel pads and assayed with antibodies that are labeled with a fluorescent tag. Antigen imbedded in the gel pads can be detected with high sensitivity and specificity (Arenkov et al., 2000). Furthermore, enzymes such as alkaline phosphatase can be immobilized in the gel pads and enzymatic activity is readily detected upon the addition of an indicator substrate. The main advantage of the use of the threedimensional gel pad for fixation of proteins is the large capacity for immobilized molecules. In addition, the pads in the array are separated from one another by a hydrophobic surface. Thus, each pad behaves as a small test tube for assay of protein-protein interactions and enzymatic reactions (Arenkov et al., 2000). The disadvantage of the method is the need to microfabricate the array of gel pads in that microfabrication is... 

NaCl or KC1 (Peng et al., 2003 Ballif et al., 2004 Beausoleil et al., 2004 Wilmarth et al., 2004 DeSouza et al., 2005 Vitali et al., 2005) may be used for the SCX fractionation, in spite of the incompatibility of these salts with mass spectrometers. When using KC1, for example, the sample must be desalted off-line (Ballif et al., 2004 Beausoleil et al., 2004), on the RP column before MS/MS acquisition (DeSouza et al., 2005 Vitali et al., 2005), with a vented column (Peng et al., 2003), or with a RP-trap (Vollmer et al., 2004 Wilmarth et al., 2004). The configuration with a RP-trap is shown in Fig. 11.1, and in this case, a flow splitter is used to reduce the flow rate from hundreds of microliters per minute to hundreds of nanoliters per minute. However, HPLC pumps of lower flow rate are now available and could eliminate the need for a flow splitter. 

FIGURE 16.5 Schematic of instrumental setup for 2D micro-RPLC-CZE. A split injection/ flow system is used to deliver a nanoliter per second flow rate to the micro-RP-HPLC column from the gradient LC pump. The HPLC microcolumn has 50 pm i.d. and 76 cm length, and the electrophoresis capillary has 17 pm i.d., L — 25 cm, and/= 15 cm. The valve is air-actuated and controls the flow of flush buffer (reprinted with permission from Analytical Chemistry). 

In contrast to high density arrays low density arrays are made by deposition of pre-synthesized oligonucleotides or proteins on activated surfaces. There are several printing techniques for fabricating microarrays Non-contact biochip arrayers, commonly based on the piezoelectric effect, can apply controlled sub-nanoliter probe volumes to pre-specified locations on the chip surface. Due to the fact that the dispenser does not touch the surface, a non-contact arrayer provides low risk of contamination and is most suitable for printing on soft materials such as hydrogels. 

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