Concentration detection limits

Electrothermal vaporization can be used for 5-100 )iL sample solution volumes or for small amounts of some solids. A graphite furnace similar to those used for graphite-furnace atomic absorption spectrometry can be used to vaporize the sample. Other devices including boats, ribbons, rods, and filaments, also can be used. The chosen device is heated in a series of steps to temperatures as high as 3000 K to produce a dry vapor and an aerosol, which are transported into the center of the plasma. A transient signal is produced due to matrix and element-dependent volatilization, so the detection system must be capable of time resolution better than 0.25 s. Concentration detection limits are typically 1-2 orders of magnitude better than those obtained via nebulization. Mass detection limits are typically in the range of tens of pg to ng, with a precision of 10% to 15%. 

Another way in which to gain structural information concerning the N-terminal residue of glycophorins A" and A is to study the N-terminal, mono[ C]methyl derivatives these are produced by using limited amounts of [ C]formaldehyde. There are distinct differences between the N, N -di[ C]methylamino and N -mono[ C]methylamino species (i) a significant, chemical-shift difference exists between the N-terminal dimethyl and monomethyl species (43 and 34 p.p.m.) (li) all of the C resonances of the N-terminal dimethyl species move upheld as the pH is increased (if they move at all), whereas all of the C resonances of the N-terminal, monomethyl species move downfield as the pH is increased and (in) A for the N-terminal monomethyl species tends to be much larger than that for the N-terminal dimethyl species. Point (in) would tend to indicate that it may be more advantageous to study the N-terminal monomethyl species. However, because of allowable protein concentrations, detection limits on available instruments, and technical difficulties, it has thus far... 

Sturgeon et al. [59] have described a hydride generation atomic absorption spectrometry method for the determination of antimony in seawater. The method uses formation of stibene using sodium borohydride. Stibine gas was trapped on the surface of a pyrolytic graphite coated tube at 250 °C and antimony determined by atomic absorption spectrometry. An absolute detection limit of 0.2 ng was obtained and a concentration detection limit of 0.04 pg/1 obtained for 5 ml sample volumes. 

Method3 Mass detection limit (moles) Concentration detection limit (molar)b Characteristics... 

Eligh analyte concentration detection limits (typically 5-50 /xM for both UV and MS detection systems due to the low sample capacity... 

Spike recovery and detection limit. Species of arsenic found in drinking water include AsO (arsenite), AsO - (arsenate), (CH3)2As02 (dimethylarsinate), and (CH3)AsO (methylarsonate). Pure water containing no arsenic was spiked with 0.40 pg arsen-ate/L. Seven replicate determinations gave 0.39, 0.40, 0.38, 0.41, 0.36, 0.35, and 0.39 pg/L.12 Find the mean percent recovery of the spike and the concentration detection limit (pg/L). 

The current resulting from a chemical reduction is directly proportional to concentration and typically can be measured with a relative precision of 0.2% and an absolute accuracy of better than 1%. For typical conditions and electrodes of conventional size, the change in current per change in concentration is on the order of 70 nanoamperes per micromolar. Detection limits in the worst case are about 1 micromolar and are typically 0.1 micromolar in favorable cases, nanomolar concentration detection limits can be achieved. The linear range, over which signal is proportional to concentration, is typically a factor of 104 to 106, for example 10 nanomolar to 1 micromolar. 

The low levels of selenium involved are well beyond the analytical range of conventional flame AA spectroscopy, which has a detection limit of about 0.5 xg/ml in solution when an air-hydrogen flame is used [59]. Although deficiency levels are slightly above the best reported concentration detection limits obtained with the carbon furnace atomisation technique [60], the matrix interference problems to be overcome appear formidable for this element [61,62]. 

METHOD MASS DETECTION limit (moles) CONCENTRATION DETECTION limit (molar) advantages/ disadvantages... 

MECC-TOAD also provides high sensitivity. A typical performance of this instrument under the conditions described above is shown in Figure 2. The detection limits calculated from Fig.2 range from 0.5 to 1.7 pM, which is equivalent to 1.4 to 4.6 fmol listed in Table I. In contrast, the HPLC-UV analyzers had about 1 pmol of mass detection limit and 2 iM concentration detection limit, provided that the injection volume was 50 pL [24]. Unfortunately, the volume mismatch between MECC-TOAD and available sequencers have limited the use of this reproducible and high sensitive technology. Therefore, miniaturization of the protein sequencer is essential. 

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