Limits of detection spectrometries

Lindane Application of gas chromatography-mass spectrometry. Limit of detection 0.1 xg/kg [170]... 

High-resolution gas chromatography-mass spectrometry, limit of detection low ppb High-performance liquid chromatography [457]... 

Bandy, Tucher, and Moroulis" used Carbosive B. In combination with mass spectrometry, limits of detection at the ppt level were achieved. 

The liquid chromatography - tandem mass spectrometry (LC/MS/MS) technique was proposed for the determination of corticosteroids in plasma and cerebrospinal fluid (CSF, liquor) of children with leucosis. Preliminai y sample prepai ation included the sedimentation of proteins, spinning and solid-phase extraction. MS detection was performed by scanning selected ions, with three chai acteristic ions for every corticosteroids. The limit of detection was found 80 pg/ml of plasma. 

In general the limit of detection of the fluorescence technique is of the order of 103 times lower than that for UV absorption spectrometry. 

GC/MS has been employed by Demeter et al. (1978) to quantitatively detect low-ppb levels of a- and P-endosulfan in human serum, urine, and liver. This technique could not separate a- and P-isomers, and limited sensitivity confined its use to toxicological analysis following exposures to high levels of endosulfan. More recently, Le Bel and Williams (1986) and Williams et al. (1988) employed GC/MS to confirm qualitatively the presence of a-endosulfan in adipose tissue previously analyzed quantitatively by GC/ECD. These studies indicate that GC/MS is not as sensitive as GC/ECD. Mariani et al. (1995) have used GC in conjunction with negative ion chemical ionization mass spectrometry to determine alpha- and beta-endosulfan in plasma and brain samples with limits of detection reported to be 5 ppb in each matrix. Details of commonly used analytical methods for several types of biological media are presented in Table 6-1. 

Liquid chromatography/mass spectrometry Lower limit of detection Limit of detection Limit of quantitation Florseshoe crab hemocyanin Liquid scintillation counting Matrix-assisted laser desorption/ ionization mass spectrometry m -Maleimidobenzoy 1-A -Hydroxysuccinimide 1 -Cyclohexyl-3-(2-Morptiolino-ethyl)carbodiimide rnetlio-/ -Toluenesulfonate (same as CDI)... 

Table 8.76 shows the main characteristics of voltammetry. Trace-element analysis by electrochemical methods is attractive due to the low limits of detection that can be achieved at relatively low cost. The advantage of using standard addition as a means of calibration and quantification is that matrix effects in the sample are taken into consideration. Analytical responses in voltammetry sometimes lack the predictability of techniques such as optical spectrometry, mostly because interactions at electrode/solution interfaces can be extremely complex. The role of the electrolyte and additional solutions in voltammetry are crucial. Many determinations are pH dependent, and the electrolyte can increase both the conductivity and selectivity of the solution. Voltammetry offers some advantages over atomic absorption. It allows the determination of an element under different oxidation states (e.g. Fe2+/Fe3+). 

Liquid Chromatography Mass Spectrometry Coupling Limit of Detection... 

Winefordner JD, Vickers TJ (1964) Calculation of limit of detectability in atomic absorption flame spectrometry. Anal Chem 36 1947... 

Gagnon [203] has described a rapid and sensitive AAS method developed from the work of Crisp et al. [200] for the determination of anionic detergents at the ppb level in natural waters. The method is based on determination by atomic absorption spectrometry using the bis(ethylene-diamine) copper (II) ion. The method is suitable for detergent concentrations up to 50 ig/l but it can be extended up to 15 mg/1. The limit of detection is 0.31 ig/1. 

PDMS = polydimethylsiloxane. PA = polyacrylate. CW = Carbowax. DVB = divinylbenzene. FID = flame ionization detection. NPD = nitrogen-phosphorus detection. TSD = thermionic-specific detection. LOQ = limit of quantitation. LOD = limit of detection. TCA = trichloroacetic acid. PICI-MS = positive ion chemical mass spectrometry. SIM = selected ion monitoring. 

Figure 2.5 Schematic comparison of limits of detection in solution (log ppb) for various absorption and emission spectrometries. For each technique, the solid box encompasses the majority of elements reported. A few relevant elements have been marked specifically at the upper and lower end of the range for each technique. (From Pollard et al., 2007 Fig. 3-4, by permission of Cambridge University Press.)...

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