Nanogram

The available sensitivity depends strongly on the equipment as well as the sample. H is the nucleus of choice for most experiments. 1 mg of a sample of a medium-sized molecule is adequate for almost all types of H-only spectra, and with specialized equipment one can work with nanogram quantities. At this lower level, the... 

Nanograms of solute per gram of solution for aqueous solutions the units are often expressed as micrograms of solute per liter of solution (ppb). 

X f0 ppb Sb was added, anodic stripping voltammetry is repeated, giving a peak current of f.i4 pA. How many nanograms of Sb is collected from the individual s hand ... 

Report the concentration of heptachlor epoxide residue (in nanograms per gram) on the oranges. 

Biomolecule Separations. Advances in chemical separation techniques such as capillary zone electrophoresis (cze) and sedimentation field flow fractionation (sfff) allow for the isolation of nanogram quantities of amino acids and proteins, as weU as the characterization of large biomolecules (63—68) (see Biopolymers, analytical techniques). The two aforementioned techniques, as weU as chromatography and centrifugation, ate all based upon the differential migration of materials. Trends in the area of separations are toward the manipulation of smaller sample volumes, more rapid purification and analysis of materials, higher resolution of complex mixtures, milder conditions, and higher recovery (69). 

Another analysis handled effectively by use of gc/ir/ms is essential oil characterization which is of interest to the foods, flavors, and fragrances industries (see Oils essential). Even very minor components in these complex mixtures can affect taste and aroma. Figure 4 shows the TRC and TIC for Russian corriander oil which is used extensively in seasonings and perfumes (15). The ir and ms are serially configured. Spectra can be obtained from even the very minor gc peaks representing nanogram quantities in the it flow cell. 

Other methods of sensitive detection of radiotracers have been developed more recently. Eourier transform nmr can be used to detect (nuclear spin 1/2), which has an efficiency of detection - 20% greater than that of H. This technique is useful for ascertaining the position and distribution of tritium in the labeled compound (14). Eield-desorption mass spectrometry (fdms) and other mass spectral techniques can be appHed to detection of nanogram quantities of radiolabeled tracers, and are weU suited for determining the specific activity of these compounds (15). 

Nevertheless, quantification is possible, a good example being the evaluation of the composition of chromatographic separations adsorbed onto glass, alumina, polyethylene, or paper. When compared with known standards, the presence of only a few nanograms of a strong fluorophore may be quantified to better than 10%. 

The detection limits for benzodiazepines, aminobenzophenones and sulfonamides lie in the lower nanogram range. 

The detection limit for amines and sulfonamides lies in the low nanogram range. 

Note The full fluorescence intensity usually only develops about 30 min after the dipping process it then remains stable for several days if the chromatograms are stored in the dark (1, 5]. Fluorescein sodium can be employed in the reagent in place of 2, 7 -dichlorofluorescein [5]. The detection limits lie in the lower nanogram to picogram range [1, 5]. 

Note The color development depends on the temperature and duration of heating [1]. The detection limit for sterols and morphine alkaloids is in the lower nanogram range [1,2]. 

Detection and result The developed chromatogram was dried in a stream of cold air, immersed in the reagent solution for 1 s and heated to 80 °C for 20 — 30 min (until optimal color development occurred). Yellow to brown-colored zones were produced on a pale yellow-colored background these were suitable for quantitative analysis. The detection limits for cholesterol hRf 20 — 25) and coprostanol 25 — 30) were a few nanograms per chromatogram zone. 

Note For some of the substances the intensities of coloration are only stable for ca. 2 h in the case of phenols the coloration intensifies during this time [2], The detection limits for indole derivatives lie in the lower nanogram range. 

In situ quantitation The fluorimetric analysis was carried out under long-wavelength UV light (/lexc = 365 nm, > 430 nm Fig. 1). The detection limit was several nanograms substance per chromatogram zone. 

In the case of carbohydrates blue chromatogram zones are produced on a yellow background that slowly fades [2]. Steroids, vitamins, antioxidants, phenols and aromatic amines yield, sometimes even at room temperature, variously colored chromatogram zones [5]. -Blockers and laxatives also acquire various colors [7, 10]. The detection hmits are in the nanogram to microgram range [5]. 

Note The reagent can be employed on sihca gel, kieselguhr. Si 50 000 and RP layers. Hydrochloric or sulfuric acid can be employed in place of phosphoric acid (q.v.). The detection limits for steroids and digitahs glycosides are several nanograms per chromatogram zone. 

K. K. Vemia, A. J. H. Louter, A. Jain, E. Pocumll, J. J. Vreuls and U. A. Th Brinkman, On-line solid-phase exti action-gas chromatography-ion cap tandem mass spectro-metiic detection for the nanogram per litre analysis of trace pollutants in aqueous samples , Chromatogmphia44 372-380 (1997). 

Amplification based methods can be used with as little as nanograms of total RNA (corresponding to <1000 cells) whereas the dendromer-based methods need at least one microgram of total RNA. 

Low NOx emission burners also are available, typically maintaining NOx to below 20 to 60 ppm CO (corrected to 3% 02), equivalent to under 20 nanogram (ng) NOx,/J output. 

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