Lanthanides detection limit

A variation on the theme of conventional assay uses both lanthanide-labeled and biotin-labeled single strands to form split probes for sequence of target strands (Figure 12).120 When both of these bind to DNA, the complex binds (via the biotin residue) to a surface functionalized with streptavidin, immobilizing the europium and allowing assay to be carried out. This approach is already very sensitive to DNA sequence, since both sequences must match to permit immobilization of the lanthanide, but can be made even more sensitive by using PCR (the polymerase chain reaction) to enhance the concentration of DNA strands. In this way, initial concentrations corresponding to as few as four million molecules can be detected. This compares very favorably with radioimmunoassay detection limits. 

Detection limits for the determination of lanthanides and actinides as determined by TRES... 

Determination of lanthanide ions with a fairly low detection limit of 10-5-10-6 wt% is achieved with Ln111 /i-diketonates. Relying on this fact new, rapid, selective, and highly sensitive analytical methods essentially based on the luminescence properties of these complexes have been developed. After a preliminary work on Smm and Eum chelates (Topilova et al.,... 

The decay times and detection limits of some lanthanides measured with time resolved fluorometry using different enhancement systems are given in Table 12.33. 

Trace and ultratrace impurities (Ti, Zn, Ga, Nb, Sn, Sb, Te, several lanthanides, Ta, Ir, Pt, Pb, Bi and U) in the xgg range and below in wet digested steel samples (with aqua regia in a microwave oven) have been determined by ICP-ToFMS. For Ca determination in steel, an analytical procedure was introduced with microwave assisted digestion and matrix separation by flow injection ICP-MS to solve the interference problem ( C 02 and Si °0 on analyte ion " " Ca+) after treatment with H2SO4 and HF, and a detection limit of 0.6(xgg was obtained. The determination of trace and ultratrace impurities in high purity (4N) copper samples, after digestion... 

Complex formation is useful for metal speciation and also for the separation of diverse metal ions. Among a variety of complexing reagents [20-22] cyanide is probably the most important. IPC separation of metal ions as metallocyanide complexes with a suitable cationic IPR is a reliable technique [23]. Complexation of trace level lanthanides with a-hydroxy isobutyric acid and separation under IPC condition shortened analysis time from days to minutes [24]. Flow injection was successfully coupled to IPC to simplify batch precomplexation detection limits were at sub-microgram per liter levels [2]. 

Sensitized luminescence in inorganic analysis will be discussed below in the section on lanthanides. Fluorescence, phosphorescence and sensitized luminescence processes are independent of the electronic structure of the organic reagent and the metal ion alone. Of importance are the composition of the complex, the nature, strength, and spatial orientation of metal-ligand bonds, and conditions under which the luminescence reaction proceeds (such as pH and the nature of solvent). All these factors significantly influence the detection limit, sensitivity and selectivity of determination. 

Hirano and Suzuki (1996) have summarized detection limits of the various ions in the lanthanide series for four analytical methods. The most sensitive method for analysis of lanthanides is inductively coupled plasma-mass spectrometry (ICP-MS), where detection limits for the series of ions range from 0.002 to 0.009 Jg L with the exception of Sm (limit of 1.5 Detection limits for lanthanides using ICP-atomic emission spectrometry (ICP-AES) range from 0.02 to 30 jg L h The sensitivity... 

The separation of yttrium from the lanthanides is performed by selective oxidation, reduction, fractionated crystallization, or precipitation, ion-exchange and liquid-liquid extraction. Methods for determination include arc spectrography, flame photometry and atomic absorption spectrometry with the nitrous oxide acetylene flame. The latter method improved the detection limits of yttrium in the air, rocks and other components of the natural environment (Deuber and Heim 1991 Welz and Sperling 1999).Other analytical methods useful for sensitive monitoring of trace amounts of yttrium are X-ray emission spectroscopy, mass spectrometry and neutron activation analysis (NAA) the latter method utilizes the large thermal neutron cross-section of yttrium. For high-sensitivity analysis of yttrium, inductively coupled plasma atomic emission spectroscopy (ICP-AES) is especially recommended for solid samples, and inductively coupled plasma mass spectroscopy (ICP-MS) for liquid samples (Reiman and Caritat 1998). 

McLaren et al. (1995) analyzed water samples for production of standard reference materials and determine 16 elements with detection limits in the subng/g range. Garbe-Schoenberg (1993), Guo and Lichte (1995) and Guenther et al. (1997) determine a number of elements in aerosols, soils and rock standard reference materials. Detection limits for lanthanides reached 0.002 p,g/g and were 0.01 p.g/g for the rest of the elements. 

Since the mid 1970 s many different structures and classes of lanthanide chelates have been synthesised (Rgure 5). For high sensitivity assays the dissociation enhanced system is currently the best approach, however for screening assays where the sensitivity or detection limitation is not an issue the fluorescent chelates can be used to simplify the assay. Some of these chelates can be even used to develop homogeneous and non-separation assays. This assay format is essential for the measurement of a reaction where the components have only a weak binding affinity thus cannot withstand a wash or separation step. 

The instrumental detection limits for more than 60 elements including carbide forming elements and lanthanides, are between 0.03 and 0.3 1 (p.p.b.) (Table 34). Instrumental detection limits for halogens, phosphorus, and sulfur lie between 0.001 and 1 mgl (p.p.m.). 

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