Improving detection limit

GDMS is slowly replacing SSMS because of its increased quantitative accuracy and improved detection limits. Like SNMS and SALI, GDMS is semiquantitative without standards ( a factor of 3) and quantitative with standards ( 20%) because sputtering and ionizadon are decoupled. GDMS is often used to measure impuri-des in metals and other materials which are eventually used to form thin films in other materials applications. [Pg.530]

Since then, TXRE has become the standard tool for surface and subsurface microanalysis [4.7-4.11]. In 1983 Becker reported the angular dependence of X-ray fluorescence intensities in the range of total reflection [4.12]. Recent demands have set the pace of further development in the field of TXRE - improved detection limits [4.13] in combination with subtle surface preparation techniques [4.14, 4.15], analyte concentrations extended even to ultratraces (pg) of light elements, e. g. A1 [4.16], spe-dation of different chemical states [4.17], and novel optical arrangements [4.18] and X-ray sources [4.19, 4.20]. [Pg.181]

Another major change was the shift from extensive use of field laboratory exploration techniques to the laboratory techniques hke ICP-AES and INAA. These produce a higher quality data than had resulted from the dc arc and other field techniques, with respect to both repeatability of measurement and improved detection limits. The metrology laboratory certifications for As and Hg in soils and sediments as key environmental toxins provided strong support to mineral exploration programs. [Pg.226]

Evaporative LC-FTIR is rapidly gaining industrial acceptance as a useful tool in low-MW additive analysis. HPLC has also been coupled with various element-selective detectors. There is significant demand for speciation information for many elements, and the separation ability of chromatography coupled to ICP-MS offers the analyst a versatile tool for such studies. It is apparent that ICP-MS is increasingly being employed for chromatographic detection. Several modes of GC, SFC, LC and CE have been hyphenated with ICP-MS for improved detection limits compared to other traditional methods of detection such as UV-VIS spectroscopy. Inorganic speciation deserves more attention. [Pg.736]

The background concentrations at which metals occur in seawater are extremely low, and much work has been done on preconcentration procedures in attempts to improve detection limits for these metals. Various preconcentra-... [Pg.128]

Amino acids labeled with DNS-C1 were determined using the Ru(bpy)32+ CL reaction after HPLC separation with a reversed-phase column [104, 105], DNS derivatives are expected to produce intense CL owing to their secondary and tertiary amino groups. The detection limit for DNS-Glu was 0.1 pM (2 pmol/ injection). Although underivatized amino acids could be detected by Ru(bpy)32+ CL, the DNS derivatives showed improved detection limits by three orders of magnitude [105], An approach to convert primary amines to tertiary amines was also reported [106], In this method, divinyl sulfone (DVS) was used for a cycloaddition reaction of primary amines (Fig. 19). The DVS derivatives after HPLC separation were sensitively detected (e.g., detection limits for propylamine and 3-aminopentane were 30 and 1 pmol, respectively). [Pg.420]

The signals from masses 292 and 326 characteristic of tetra- and pentachlorobiphenyl are shown in Fig. 1.6 (b,c). The specific detection mode of the ion-trap detector can be used to improve detection limits. This detector can monitor specific masses that are characteristic of compounds of interest. The detector records the signal for only those masses and ignores all others. Interference from other compounds is virtually eliminated with the Finnigan MAT 700 detector—up to 16 different groups of masses can be monitored or a mass range of up to 40 masses can be handled. With this flexibility it is possible to monitor only the masses of interest and to improve detection limits. [Pg.76]

The FIA-APCI-MS data showed improved detection limits, reproducibility and correlation of standards over the HPLC-LSD results. However, extension of the FIA-MS method to other systems yielded erroneous quantitative data, attributed to signal response discrimination through competitive ionisation effects, and as such incorporation of online HPLC separation methods was determined to be the preferred API-MS method for quantitative analyses [29]. [Pg.246]

The spot size of MALDI preparations and thus the amount of sample necessary to yield a useful layer can be further reduced by so-called anchor targets (Bruker Daltonik). Anchor targets exhibit small hydrophilic spots on a hydrophobic surface. As a result, the evaporating drop of matrix-analyte solution is anchored to such a point where it shrinks until the onset of crystallization exactly within this hydrophilic area. [110] The resulting preparation covers an about lOOfold smaller surface than obtained from a freely spreading drop. In addition to improved detection limits, this technique simplifies automated spot finding due to their precisely defined location on the target. [Pg.422]

Concentrations of neuroactive steroids that are present in brain and plasma are normally very low. Therefore, several prepurification steps are generally required before analyzing these samples. It is necessary to improve detection limits and to introduce new methods of analyzing these samples directly from solution, without these labor-intensive and time-consuming prepurification procedures. Now, most neurosteroid analyses are performed by RIA or by GC/MS. The most sensitive GC/MS reported so far is GC/EC-NCI/MS, wherein MS in performed in the SIM mode. Neurosteroid sulfates can be directly analyzed by MS, without derivatization, by using soft ionization methods such as FAB and ESI. These methods are currently undergoing further refinement and development. [Pg.189]

The high surface areas of these electrodes make them ideal for electroanalytical applications where the high surface area is exploited to improve detection limits and/or detection range. Evans et al. [61] have demonstrated the production of platinum mesoporous electrodes and their application into the detection of H2O2. [Pg.21]

A major contributing factor to the increased sensitivity of the improved HPLC system over that originally described (5 ) is the detector. The original method utilized a fluorescence spectrophotometer adapted for HPLC detection by use of a fabricated 40 ul flow cell. The present system utilizes a highly sensitive HPLC fluorescence detector and this contributes greatly to the improved detection limits. [Pg.204]

Miniaturizing the column i.d. is of great benefit to the sensitivity of ESl-MS, which behaves as a concentration-sensitive detection principle, because the concentration of equally abundant components in the LC mobile phase is proportional to the square of the column internal diameter. Column diameters from 150 to 15 jm with flow rates 20-200nL improve detection limits of peptides 1-2 orders magnitude over microliter flow rates. Several references referred to in other sections of this chapter discuss the use of LC-ESI MS to characterize separation products. and a sample chromatogram from Ito and coworkers. is seen in Figure 3.8. Table 3.4 provides additional and references that have used this technique. [Pg.88]

Analytical techniques such as adsorptive stripping voltammetry rely on complex formation to improve detection limits of metals such as V(IV) and V(V) [51]. An example is in the use of cupferron and KBr03 as additives to acidic aqueous solutions, which result in the adsorption of the V(V)-cupferron complex to the electrode surface that catalyzes the reduction of the Br03 ion in solution. This technique has good selectivity over Cu, Pb, Cd, Fe, and Ti, but the response is dependent on pH. [Pg.367]

Under isocratic development, if the early peaks of the mixture are adequately separated, then the late peaks are often broad, and consequently, at concentrations so low that they are hardly detectable. Conversely, if the late peaks are eluted at a sufficiently low k values to improve detection limits, the early peaks become bunched together and are not resolved. This problem is obviated considerably by employing gradient elution, but if there are a large number of individual solutes present in the sample,then the same problems will arise. These difficulties are caused by the column having a limited peak capacity and it is, therefore, important to determine how to calculate peak capacity and how to control it. From the Plate Theory, the peak width at the base is given by -... [Pg.67]

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