Analysis detection limits

Few well characterized, validated methods are available for the determination of w-hexane in blood. A purge-and-trap method for volatiles has been developed and validated by researchers at the Centers for Disease Control and Prevention (CDC) (Ashley et al. 1992, 1994). Extension of the method to include /7-hexane should be possible. Current analytical methods utilize capillary GC columns and MS detection to provide the sensitivity and selectivity required for the analysis. Detection limits are in the low ppb range (Brugnone et al. 1991 Schuberth 1994). Headspace extraction followed by GC analysis has also been utilized for the determination of /7-hexanc in blood (Brugnone et al. 1991 Michael et al. 1980 Schuberth 1994) however, very little performance data are available. 

Determination of mandelic acid in urine has been recommended as a biomaiker of exposure to ethylbenzene. Several methods can be used to determine mandelic acid in urine samples. These include derivatization of the acid and GC analysis (detection limit, 1.0 mg/L) isotachophoresis (detection limit, 0.04 mmol/L) and high-performance liquid chromatography (detection limit, 0.01 mmol/L) (WHO, 1996a). 

TSK-Gel LS-160 Sodium perchlorate - potassium dihydrogen phosphate - Sodium chlo- ride. UV Applicable in urine and blood analysis. Detection limit 30 ng. 

Physical and chemical interferences elevate the XRF analysis detection limits for certain soil types, the actual detection limits may exceed these for an interference-free matrix shown in Table 3.10. The XFR detection limits are always higher than the detection limits for other elemental analysis techniques. The high detection limits may not be appropriate for some types of DQOs and are the greatest limitation of XRF screening. 

Acetylcholineesterase, urease, glucose oxidase and butyryl chloinesterase. Immobilized enzyme on to the sensor chip by corsslinking with glutaraldehyde and BSA. Conductivity changes, produced by the enzyme-catalyzed hydrolysis of ACh were measured for the analysis. Detection limits for ACh was 0.07 mM with corresponding sensitivity of 5.6 0.2 pS/mM. The device could be also used for apparent Michaelis constant determination. [85]... 

Quantification. Gas Chromatography. In blood head-space analysis, detection limit 18 ng/ml, FID—J. M. Christensen et al, Clinica chim. Acta, 1981,116, 389-395. 

Gas Chromatography. In plasma or urine trichloroethanol, ECD—D. J. Berry, Chromat., 1975,107, 107-114. In blood or urine chloral hydrate, trichloroethanol and trichloroacetic acid, head-space analysis, detection limit 500 ng/ml for chloral hydrate and trichloroethanol, ECD—D. D. Breimer et al., J. Chromat., 1974,88, 55-63. 

Quantification. Gas Chromatography. In blood using head-space analysis, FID—F. N. Prior, Anaesthesia, 1972, 27, 379-389. In blo or urine trichloroethanol and trichloroacetic acid, using headspace analysis, detection limit 500 ng/ml for trichlo-... 

The AA analyses were used as a guide for selecting the elements to be analyzed with the Philips XRF system (Table II). Major elements not usually of environmental concern were analyzed as well as trace elements because of their effect on the X-ray absorption of the heavier elements. Elements below the XRF analysis detection limits, such as Hg and Cd, were not analyzed. Samples prefixed with the letter F were mechanically separated so as to bias the fine-particle size. This procedure indicated to what degree the shipboard centrifugal cone separator, used to select the finer sediment particles, influenced the elemental composition. 

Analysis Detection Limit Standard Analysis Detection Limit Standai... 

SIMS Is more sensitive than the other common surface or Interface analysis techniques of Auger X-ray Photoelectron Spectroscopy Rutherford BackscatterIng Spectroscopy or Energy Dispersive X-ray Analysis. Detection limits and background signal levels for a large number of semiconductor materials have been reported under typical operating conditions (Ji). Table I lists the detection limits for a number of dopants used In semiconductors obtained under optimized conditions. 

The very low odor threshold limits of 4-EG and 4-EP in wine need sensitive analytical methods, including prior concentration steps. By using GC/MS analysis, detection limits of a few microgram per liter and wide linearity range can be achieved (Pollnitz et al., 2000 Martorell et al, 2002). Several methods of sample preparation were proposed liquid-liquid extraction (Chatonnet et al., 1992 Versini, 1985 Chatonnet et al., 1995 Pollnitz et al, 2000 Chatonnet and Boidron, 1988 Rocha et al., 2004) SPE (Aznar et al., 2001 Dominguez et al., 2002 Lopez et al., 2002) SPME and HS-SPME (Martorell et al., 2002 Ferreira et al., 1996 1998 Monje et al., 2002 Castro Mejias et al., 2003) and stir bar sorptive extraction (SBSE) (Dfez et al., 2004). 

Screening tests for the trichothecene mycotoxins are generally simple and rapid but, with the exception of the immunochemical methods, are nonspecific. A number of bioassay systems have been used for the identification of trichothecene mycotoxins.73 Although most of these systems are very simple, they are not specific, their sensitivity is generally relatively low compared to other methods, and they require that the laboratory maintain vertebrates, invertebrates, plants, or cell cultures. Thin-layer chromatography (TLC) is one of the simplest and earliest analytical methods developed for myco-toxin analysis. Detection limits for trichothecene mycotoxins by TLC is 0.2 to 5 ppm (0.2 to 5 pg/ mL). Therefore, extracts from biomedical samples would have to be concentrated 10- to 1,000-fold to screen for trichothecene mycotoxins. 

SPLS is very sensitive and selective for organic trace analysis. Detection limits of a nanogram or even a picogram can be obtained. The methodology is simple, inexpensive, relatively precise (2-20%), relatively rapid, can handle small samples, and can be very selective in mixture analysis when solid-phase fluorescence (SPF) and solid-phase phosphorescence (SPP) are combined or when using derivative, synchronous, or time-resolved SPLS. Additionally, SPLS is well suited to being combined directly with both thin-layer and paper planar chromatography. 

AAS is a useful technique for the determination of traces of metals in polymers. In general, the polymer is ashed at a maximnm temperature of 450 C 0.1 hour from start heat to 200 °C 1-3 hours from start hold at 200 "C 3-5 hours from start heat to 450 °C 5-8 hours from start hold at 450 °C. Ash is digested with warm nitric acid before spectrometric analysis. Detection limits for metals in polymers achievable by this procedure range from 0.02 ppm (zinc) to 0.57 ppm (iron). 

Static SiMS Static Secondary ion Mass Spectroscopy Surface Ion beam (0.5-20 keV) Secondary ions, analysis with mass spectrometer 0.1-0.5 nm 10 im Elemental analysis of surface layers molecular analysis detection limits ppb-ppm 4... 

LIMS Laser Ionization Mass Spectroscopy Surlace, bulk U.V. laser (ns pulses) Ionized species analyzed with mass spectrometer 50-150 nm 5 (in-1 mm Elemental (micro)analysis detection limits 1-100 ppm 8... 

GDMS Glow Discharge Mass Spectroscopy Sample forms Ihe cathode for a D C. glow discharge Sputtered atoms ioni in plasma Ions - analy in mass spectrometer 0.1-100 pm 4 lull (Bulk) trace element analysis detection limit sub-ppb 9,10... 

Uhler and Miller [39] developed a GC multiple headspace extraction technique for the determination of volatile hydrocarbons in butter [39]. In a related procedure to determine styrene and its dimer in milk, acetone was used to precipitate proteins and extract fat and the residues from the packaging material. Using direct injection of these extracts for GC analysis, detection limits were 0.16 mg/kg for styrene and 0.28 mg/kg for the dimer [40]. 

Jg is the background intensity, t the measuring time and S the sensitivity (cps ppm or cps ng i). Either increasing the sensitivity or reducing the background leads to a reduction of detection limits. Therefore, special techniques of XRF, mainly EDXRF techniques, are applied, like TXRF, MXRF or SRXRF, as methods for trace element analysis. Detection limits range from ng to fg or pg g i to pg g... 

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