Lower limit of detection

In hplc, detection and quantitation have been limited by availabiHty of detectors. Using a uv detector set at 254 nm, the lower limit of detection is 3.5 X 10 g/mL for a compound such as phenanthrene. A fluorescence detector can increase the detectabiHty to 8 x 10 g/mL. The same order of detectabiHty can be achieved using amperometric, electron-capture, or photoioni2ation detectors. 

The near-ir spectmm of ethylene oxide shows two peaks between 1600—1700 nm, which are characteristic of an epoxide. Near-ir analyzers have been used for verification of ethylene oxide ia railcars. Photoionization detectors are used for the deterrnination of ethylene oxide ia air (229—232). These analyzers are extremely sensitive (lower limits of detection are - 0.1 ppm) and can compute 8-h time-weighted averages (TWAg). 

The lower limit of detection is 1 p.g/dm for sodium hexadecyl sulfonate, 2.5 p.g/dm for sodium dodecyl benzenesulfonate and 10 p.g/diW for sodium dodecyl sulfonate with sample volume of O.ldiW. The method proposed is highly sensitive, simple, rapid and guarantees environmental safety of analysis. 

The analysis was performed by SRXRF at the XRF beam-line of VEPP-3, Institute of Nuclear Physics, Novosibirsk, Russia. For accuracy control the International Certified Reference Materials were used. There were obtained all metrological characteristics, namely precision, accuracy and lower limits of detections. 

The System described in the previous section has been extended with a sulfur chemiluminescence detector (SCO) for the detection of Sulfur compounds (32). The separated fractions were thiols + sulfides + thiophenes (as one group), benzothio-phenes, dibenzothiophenes and benzonaphtho-thiophenes. These four groups have been subsequently injected on-line into and separated by the GC unit. Again, no overlap between these groups has been detected, as can be seen from Figure 14.20, in which the total sulfur compounds are shown and from Figure 14.21 in which the separated dibenzothiophenes fraction is presented. The lower limit of detection of this method proved to be 1 ppm (mg kg ) sulfur per compound. 

With the increasingly lower limits of detection being achieved in various types of instrumental analysis, there is an ever growing demand for reagents of... 

A number of ion-selective electrodes are available from laboratory supply houses whilst not intended to be an exhaustive list, Table 15.3 serves to indicate the variety of determinations for which electrodes are available. An indication is also given of the lower limit of detection of the electrodes this figure may vary somewhat according to the source of the electrode but full details are furnished by the manufacturer of the effective range of use of each electrode and of likely interferences. 

Ion Lower limit of detection, pX Ion Lower limit of detection, pX ... 

Routine use for control purposes has shown the method to be reliable and interlaboratory agreement on data has been good. The method as presented has consistently detected < 1 ppm of sultone in a 38% alkenesulfonate solution. By concentrating the solution of the neutral oil and using silica gel column chromatography, 0.1 ppm of sultone can readily be detected. Further changes in GC conditions and sensitivity can give even lower limits of detection. 

No dioxin residues were detected at a level of 0.05 ppm TCDD, the lower limit of detection for most pesticides in tissue samples run by the Patuxent Wildlife Research Center. The non-detection of dioxin residues can imply several things ... 

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)... 

Assay sensitivity is defined here as the concentration of analyte that inhibits the observed absorbance by 50% or the IC50. The lower limit of detection (LLD) is the lowest analyte concentration that elicits a detector response significantly different from the detector response in the absence of analyte. In some cases, the LLD is defined as three standard deviations from the mean of the zero analyte control. In other cases, the LLD is defined empirically by determining the lowest concentration of analyte that can be measured with a given degree of accuracy. Readers are referred to Grotjan and Keel for a simplified explanation and to Rodbard for the complete mathematics on the determination of LLD. 

The detection limits, accuracy, and precision of any analytical methodology, as well as the composition of the sample medium, are important parameters in determining the appropriateness of a method to quantify a specific analyte at the desired level of sensitivity within a particular matrix. The lower limit of detection (LLD) has been adopted to refer to the intrinsic detection capability of a measurement procedure (sampling... 

NRC. 1984. Nuclear Regulatory Commission. Lower limit of detection definition and elaboration of a purposed position for radiological effluent and environmental measurements. U.S. Report NUREG/CR-4007. 

ELCD Good lower limit of detection Good selectivity Inexpensive Several critical parameters Difficult to use [42]... 

Table 4.22 Lower limits of detection (LLD) of some GC detectors...

R. Schuster and H. Schulenberg-Schell, A New Approach to Lower Limits of Detection and Easy Spectral Analysis, Agilent Technologies Application Primer No. 

Stamey, T. A. Lower limits of detection, biological detection limits, functional sensitivity, or residual cancer detection limit/sensitivity reports on prostate-specific antigen assays mislead clinicians. Clin. Chem. 42, 849-850 (1996). 

After the end of the 4-day exposure, the detectors were returned to EML for analysis. The amount of radon adsorbed on the carbon device was determined by counting the gamma rays of radon progeny in equilibrium with radon. The concentrations of radon in the buildings were determined from the radioactivity in the device and the calibration factor, obtained in a radon chamber, that takes into consideration the length of exposure and a correction for the amount of water vapor adsorbed during the exposure. The lower limit of detection with this technique is 0.2 pCi/1 for a measurement period of 4 days when the test sample is counted for 10 min, 4 days after the end of exposure. More than 90% of the radon monitoring devices were analyzed successfully. Most of the unsuccessful measurements were due to delays or losses caused by the participants. 

Brown and Bellinger [123] have proposed an ultraviolet technique that is applicable to both polluted and unpolluted fresh and some estuarine waters. Humic acid and other organics are removed on an ion exchange resin. Bromide interference in seawater samples can be minimised by suitable dilution of the sample but this raises the lower limit of detection such that only on relatively rich (0.5 mg/1 NO3N) estuarine and inshore waters could the method be used. Chloride at concentrations in excess of 10 000 mg/1 do not interfere. 

The lower limit of detection of this method is 0.2mg/l for calcium and magnesium. 

Sometimes orthogonal offline SPE steps were used prior to online SPE LC/MS/MS. These preparation steps were used to remove interference and concentrate samples. In an application to measure urinary N7-(benzo[a]pyren-6-yl)guanine (BP-6-N7Gua), a biomarker for exposure to polyaromatic hydrocarbons (PAHs), a two-step offline SPE was first performed using Sep-Pak C8 (Waters, Milford, Massachusetts) and Strata SCX (Phenomenex, Torrance, California) cartridges to obtain high sensitivity (Chen et al. 2005). The extracts were applied to an online reversed phase SPE LC/MS system. The lower limit of detection was 2.5 fmol/mL when 10 mL of urine was used. 

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