Limits of Linearity and Detection for Some Drugs of Abuse*

Abstract

The limits of linearity (LOL) and detection (LOD) are important factors in establishing the reliability of an analytical procedure for accurately assaying drug concentrations in urine specimens. Multiple analyses of analyte over an extended range of concentrations provide a measure of the ability of the analytical procedure to correctly identify known quantities of drug in a biofluid matrix. Each of the seven drugs of abuse gives linear analytical responses from concentrations at or near their LOD to concentrations several-fold higher than those generally encountered in the drug screening laboratory. The upper LOL exceeds the Department of Navy (DON) cutoff values by factors of approximately 2 to 160. The LOD varies from 0.4 to 5.0% of the DON cutoff value for each drug. The limit of quantitation (LOQ) is calculated as the LOD + 7 SD. The range for LOL is greater for drugs analyzed with deuterated internal standards compared with those using conventional internal standards. For THC acid, cocaine, PCP, and morphine, LOLs are 8 to 160-fold greater than the defined cutoff concentrations. For the other drugs, the LOL's are only 2 to 4-fold greater than the defined cutoff concentrations.

Limit of Detection and Limit of Quantification Determination in Gas Chromatography

“…The linear calibration line, with its upper and lower confidence limits. y c is the decision limit and x D the detection limit [33].…”

“…This approach is considered a fairly accurate way to determining method detection limits [23]. This approach is similar in some aspects to the so-called empirical method [24,33], where increasingly lower concentrations of the analyte are analyzed until the measurement do not satisfy a predetermined criteria.…”

Electrochemical Determination of Anesthetic Drug Ropivacaine in Pharmaceutical Formulations by Differential Pulse Cathodic Adsorptive Stripping Voltammetry

“…The LOD is the smallest concentration or amount that can be detected with reasonable certainty for a given analytical procedure. The detection limit was calculated by the equation 27 .…”

Determining the limits and confounders for the 2-pentyl furan breath test by gas chromatography/mass spectrometry

“…It has previously been reported that the statistical method is not sensitive enough as it measure the average noise level of the procedure and defines only the ability to measure nothing rather than a very low concentration of analyte [18]. Armbruster et al [17] also reported the statistically determined LOD and LOQ values underestimated the LOD because of the large imprecision associated with blank measurements and the inability of blank samples to meet typical GC-MS acceptance criteria.…”