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Jeanmichel Mermet - One of the best experts on this subject based on the ideXlab platform.
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A logical way through the Limits of Quantitation in inductively coupled plasma spectrochemistry
Spectrochimica Acta Part B: Atomic Spectroscopy, 2012Co-Authors: Jeanmichel Mermet, G. Granier, P. FichetAbstract:Abstract The Limit of Quantitation (LOQ) is a crucial parameter in quantitative analysis. Besides the classical “10 s B approach”, other concepts have been previously described based on the Limitation resulting from the calibration procedure, namely from the prediction bands and the uncertainty calibration. Because of the difficulty of obtaining a reliable value of the blank standard deviation, this approach was replaced by the study of the %RSD of the net signal as a function of the concentration. Recently described, the so-called accuracy profile method, accuracy being the contribution of both the trueness and the precision, allows the analyst to define a validity domain, the lowest point acting as a Limit of Quantitation. The aim of this work was to determine these various Limits of Quantitation, including that from the accuracy profile, to compare them, and to study the parameters that can influence their values. It was concluded that the LOQ deduced from the accuracy profile is a realistic one. Its value is mainly influenced by the calibration procedure, particularly when a weighting procedure is used. A 1/ y weighting factor, y being the analyte line intensity, seems to be an efficient compromise for calibration.
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Limit of Quantitation in atomic spectrometry an unambiguous concept
Spectrochimica Acta Part B: Atomic Spectroscopy, 2008Co-Authors: Jeanmichel MermetAbstract:Abstract This document presents a tutorial description of several concepts and definitions of Limits of Quantitation, such as the so-called 10 s, the RSDnet, the method Limit, the lower Limit of the calibration graph and the uncertainty approaches. Use, advantages, Limitations and complexity of the various approaches are illustrated with some examples taken from atomic spectrometry, using ICP-AES, ICP-MS and LIBS. Information that can be deduced from the calibration graph is emphasized.
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a study of the relation between the Limit of detection and the Limit of Quantitation in inductively coupled plasma spectrochemistry
Spectrochimica Acta Part B: Atomic Spectroscopy, 1997Co-Authors: M Carre, S Excoffier, Jeanmichel MermetAbstract:The Limit of Quantitation based on a repeatability threshold concept is compared with the Limit of detection in induction coupled plasma atomic emission spectrometry (ICP-AES) and induction coupled plasma mass spectrometry (ICP-MS). A 5%-based Limit of Quantitation would normally correspond to 10 times the 3-σ based Limit of detection. However, because of a possible lack of linearity of the calibration graph at low concentrations, some additional noise not taken into consideration and the possible use of time-correlated multichannel detection, this ratio of 10 cannot be used in every case. It is suggested that a suitable way of determining the Limit of Quantitation is to establish the plot of the percentage relative standard deviation (RSD) of the net signal as a function of the concentration in a range from the Limit of detection to 50 times this Limit.
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simultaneous measurements of signal and background in inductively coupled plasma atomic emission spectrometry effects on precision Limit of detection and Limit of Quantitation
Spectrochimica Acta Part B: Atomic Spectroscopy, 1996Co-Authors: Emmanuelle Poussel, Jeanmichel MermetAbstract:Abstract Use of simultaneous measurements of the line intensity and the off-peak background intensity results in a significant improvement of repeatability at low concentrations, the Limit of detection and the Limit of Quantitation in inductively coupled plasma atomic emission spectrometry. Simultaneous measurements have been performed using an echellebased dispersive system equipped with a custom segmented-array charge coupled device detector. Correlation between background signals, and shape of the curve of the RSD of the net signal as a function of the concentration is studied from both a theoretical and practical aspect. Concepts of Limit of detection and Limit of Quantitation are discussed both in terms of RSD of the net signal and correlation. Results have been obtained using the Ba II 455 nm line in the visible region and the Ni II 231 nm line in the UV region. Improvements in the Limit of detection and Limit of Quantitation are up to a factor of 10 and are in good agreement with theoretical values. The main Limitation of the procedure is related to the accuracy of the background correction.
Stanley Lech - One of the best experts on this subject based on the ideXlab platform.
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A stability-indicating HPLC method for the determination of glucosamine in pharmaceutical formulations
Journal of Pharmaceutical and Biomedical Analysis, 2004Co-Authors: Yu Shao, Rama Alluri, Mike Mummert, Uwe Koetter, Stanley LechAbstract:A stability-indicating high performance liquid chromatographic (HPLC) method was developed for the assay of glucosamine in bulk forms and solid dosage formulations. The HPLC separation was achieved on a Phenomenex Luna amino column (150 mm??4.6 mm, i.d., 5 ??m particle size) using a mobile phase of acetonitrile-phosphate buffer (75:25, v/v, pH 7.50) at a flow rate of 1.5 ml min-1 and UV detection at 195 nm. The method was validated for specificity, linearity, solution stability, accuracy, precision, Limit of detection, and Limit of Quantitation. The detector response for glucosamine hydrochloride was linear over the selected concentration range from 1.88 to 5.62 mg ml-1 with a correlation coefficient 0.9998. The accuracy was between 98.9 and 100.5%. The precision (R.S.D.) amongst six sample preparations was 1.1%. The Limit of detection and the Limit of Quantitation are 0.037 and 0.149 mg ml-1, respectively. The sample and standard solutions were stable for 1 week. The method was successfully used for analysis of active-excipient compatibility samples used for development of a solid dosage formulation in our laboratory and subsequent stability studies. The method was also used for the analysis of glucosamine in several commercially available solid dosage forms. ?? 2004 Elsevier B.V. All rights reserved.
Yu Shao - One of the best experts on this subject based on the ideXlab platform.
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A stability-indicating HPLC method for the determination of glucosamine in pharmaceutical formulations
Journal of Pharmaceutical and Biomedical Analysis, 2004Co-Authors: Yu Shao, Rama Alluri, Mike Mummert, Uwe Koetter, Stanley LechAbstract:A stability-indicating high performance liquid chromatographic (HPLC) method was developed for the assay of glucosamine in bulk forms and solid dosage formulations. The HPLC separation was achieved on a Phenomenex Luna amino column (150 mm??4.6 mm, i.d., 5 ??m particle size) using a mobile phase of acetonitrile-phosphate buffer (75:25, v/v, pH 7.50) at a flow rate of 1.5 ml min-1 and UV detection at 195 nm. The method was validated for specificity, linearity, solution stability, accuracy, precision, Limit of detection, and Limit of Quantitation. The detector response for glucosamine hydrochloride was linear over the selected concentration range from 1.88 to 5.62 mg ml-1 with a correlation coefficient 0.9998. The accuracy was between 98.9 and 100.5%. The precision (R.S.D.) amongst six sample preparations was 1.1%. The Limit of detection and the Limit of Quantitation are 0.037 and 0.149 mg ml-1, respectively. The sample and standard solutions were stable for 1 week. The method was successfully used for analysis of active-excipient compatibility samples used for development of a solid dosage formulation in our laboratory and subsequent stability studies. The method was also used for the analysis of glucosamine in several commercially available solid dosage forms. ?? 2004 Elsevier B.V. All rights reserved.
R. J. Bertz - One of the best experts on this subject based on the ideXlab platform.
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Statistical estimation of the minimum drug concentration at the steady state when the assay result is below the lower Limit of Quantitation
Clinical Pharmacology & Therapeutics, 2004Co-Authors: Y. Chiu, D. Burt, B. Hosmane, R. J. BertzAbstract:In clinical studies it is common to assess the minimum drug concentration (Cmin) in blood at the steady state. However it is not uncommon to have a small number of assay results that are below the lower Limit of Quantitation (LLOQ). While the 0
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statistical estimation of the minimum drug concentration at the steady state when the assay result is below the lower Limit of Quantitation
Clinical Pharmacology & Therapeutics, 2004Co-Authors: Y. Chiu, D. Burt, B. Hosmane, R. J. BertzAbstract:In clinical studies it is common to assess the minimum drug concentration (Cmin) in blood at the steady state. However it is not uncommon to have a small number of assay results that are below the lower Limit of Quantitation (LLOQ). While the 0
of Cmin for statistical analysis and calculation of geometric mean. Using LLOQ for imputation results in over-estimation. In either case the magnitude of bias was unknown. Other methods proposed included imputation with a small quantity (e.g. 12 LLOQ), exclusion of observations of the tail probability distribution to impute a magnitude below LLOQ. Estimation based on each of the two methods is provided using a real data set. In this case, the estimated Cmin is approximately 60% and 75% of LLOQ using mean and median methods, respectively. Monte Carlo simulation is used to assess the performance of the proposed methods. Clinical Pharmacology & Therapeutics (2004) 75, P42–P42; doi: 10.1016/j.clpt.2003.11.157
David A Armbruster - One of the best experts on this subject based on the ideXlab platform.
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Limit of blank Limit of detection and Limit of Quantitation
The Clinical biochemist. Reviews Australian Association of Clinical Biochemists, 2008Co-Authors: David A ArmbrusterAbstract:Limit of Blank (LoB), Limit of Detection (LoD), and Limit of Quantitation (LoQ) are terms used to describe the smallest concentration of a measurand that can be reliably measured by an analytical procedure. LoB is the highest apparent analyte concentration expected to be found when replicates of a blank sample containing no analyte are tested. LoB = meanblank + 1.645(SDblank) LoD is the lowest analyte concentration likely to be reliably distinguished from the LoB and at which detection is feasible. LoD is determined by utilising both the measured LoB and test replicates of a sample known to contain a low concentration of analyte. LoD = LoB + 1.645(SD low concentration sample) LoQ is the lowest concentration at which the analyte can not only be reliably detected but at which some predefined goals for bias and imprecision are met. The LoQ may be equivalent to the LoD or it could be at a much higher concentration. Introduction Sensitivity, Analytical Sensitivity, Functional Sensitivity, Lower Limit of Detection, LoB, LoD, and LoQ are terms used to describe the smallest concentration of a measurand that can be reliably measured by an analytical procedure. There has often been a lack of agreement within the clinical laboratory field as to the terminology best suited to describe this parameter. Likewise, there have been various methods for estimating it. Clinical laboratorians have perhaps been lax in dealing with this analytical issue because, in many cases, the ability of a laboratory test to detect a very small amount of measurand is not clinically significant. For example, the medical decision levels for glucose and cholesterol are so far above the lower analytical Limits of these tests that it is highly unlikely that clinical action will depend on measurements of these analytes at such low concentration. Nevertheless, it is important to fully characterise the analytical performance of every clinical laboratory test in order to understand its capability and Limitations, and to ensure that it is “fit for purpose.” Moreover, defining the Limits of an assay at low concentration is directly related to its dynamic range, or analytical measurement range. To provide a standard method for determining LoB, LoD and LoQ, Clinical and Laboratory Standards Institute (CLSI) has published the guideline EP17, Protocols for Determination of Limits of Detection and Limits of Quantitation.1 The Figure taken from their document illustrates the distinction of LoB, LoD and LoQ values. Typically, LoQ will be found at a higher concentration than LoD, but how much higher depends on the specifications for bias and imprecision used to define it. ‘Analytical sensitivity’ defined as the slope of the calibration curve is sometimes used as a synonym for LoD. However, because LoD may well reside at some concentration below the linear range of an assay, where the calibration curve is no longer valid, this usage should be avoided. Figure Relationship between LoB, LoD and LoQ. The solid line defines the LoB and represents the distribution of results for a blank specimen. As modern analysers seldom report results of less than zero, the frequency of “zero” results is artificially ... All of these parameters are related but have distinct definitions and should not be confused. The intent is to define the smallest concentration of analyte that can be detected with no guarantee about the bias or imprecision of the result by an assay, the concentration at which Quantitation as defined by bias and precision goals is feasible, and finally the concentration at which the analyte can be quantitated with a linear response.
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Limit of blank, Limit of detection and Limit of Quantitation.
The Clinical biochemist. Reviews Australian Association of Clinical Biochemists, 2008Co-Authors: David A Armbruster, Terry PryAbstract:* Limit of Blank (LoB), Limit of Detection (LoD), and Limit of Quantitation (LoQ) are terms used to describe the smallest concentration of a measurand that can be reliably measured by an analytical procedure. * LoB is the highest apparent analyte concentration expected to be found when replicates of a blank sample containing no analyte are tested. LoB = mean(blank) + 1.645(SD(blank)). * LoD is the lowest analyte concentration likely to be reliably distinguished from the LoB and at which detection is feasible. LoD is determined by utilising both the measured LoB and test replicates of a sample known to contain a low concentration of analyte. * LoD = LoB + 1.645(SD (low concentration sample)). * LoQ is the lowest concentration at which the analyte can not only be reliably detected but at which some predefined goals for bias and imprecision are met. The LoQ may be equivalent to the LoD or it could be at a much higher concentration.
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Limit of detection lqd Limit of Quantitation loq comparison of the empirical and the statistical methods exemplified with gc ms assays of abused drugs
Clinical Chemistry, 1994Co-Authors: David A Armbruster, M D Tillman, L M HubbsAbstract:The Limit of detection (LOD) for any analytical procedure, the point at which analysis is just feasible, may be determined by a statistical approach based on measuring replicate blank (negative) samples or by an empirical approach, consisting of measuring progressively more dilute concentrations of analyte. The Limit of Quantitation (LOQ), or concentration at which quantitative results can be reported with a high degree of confidence, may likewise be determined by either approach. We used both methods to determine LOD and LOQ for forensic gas chromatographic-mass spectrometric (GC-MS) analyses of abused drugs. The statistically determined LOD and LOQ values for these assays 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. The empirical method provided much more realistic LOD values, supported by reasonable experimental data, and are 0.5-0.03 the magnitude of the corresponding statistical LODs. The empirical LODs and LOQs are identical for these GC-MS assays. The observations made here about the LOD/LOQ for specific forensic GC-MS procedures are generally applicable to any type of analysis.