Internal standard versus external standard calibration: an uncertainty case study of a liquid chromatography analysis

Oliveira, Elcio Cruz de; Müller, Edson I.; Abad, Fernanda; Dallarosa, Juliana Braga; Adriano, Cristine

doi:10.1590/s0100-40422010000400041

Cited by 35 publications

(21 citation statements)

References 5 publications

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“…All linear equations met the minimum qualification of R 2 value of 0.98. Subsequent determination of concentration was determined by obtaining the area under the curve directly from the GC-FID and solving for x in the linear equation of each chemical [ 66 – 68 ].…”

Section: Methodsmentioning

confidence: 99%

Evaluating putative repellent ‘push’ and attractive ‘pull’ components for manipulating the odour orientation of host-seeking malaria vectors in the peri-domestic space

et al. 2021

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Background Novel malaria vector control approaches aim to combine tools for maximum protection. This study aimed to evaluate novel and re-evaluate existing putative repellent ‘push’ and attractive ‘pull’ components for manipulating the odour orientation of malaria vectors in the peri-domestic space. Methods Anopheles arabiensis outdoor human landing catches and trap comparisons were implemented in large semi-field systems to (i) test the efficacy of Citriodiol® or transfluthrin-treated fabric strips positioned in house eave gaps as push components for preventing bites; (ii) understand the efficacy of MB5-baited Suna-traps in attracting vectors in the presence of a human being; (iii) assess 2-butanone as a CO2 replacement for trapping; (iv) determine the protection provided by a full push-pull set up. The air concentrations of the chemical constituents of the push–pull set-up were quantified. Results Microencapsulated Citriodiol® eave strips did not provide outdoor protection against host-seeking An. arabiensis. Transfluthrin-treated strips reduced the odds of a mosquito landing on the human volunteer (OR 0.17; 95% CI 0.12–0.23). This impact was lower (OR 0.59; 95% CI 0.52–0.66) during the push-pull experiment, which was associated with low nighttime temperatures likely affecting the transfluthrin vaporisation. The MB5-baited Suna trap supplemented with CO2 attracted only a third of the released mosquitoes in the absence of a human being; however, with a human volunteer in the same system, the trap caught < 1% of all released mosquitoes. The volunteer consistently attracted over two-thirds of all mosquitoes released. This was the case in the absence (‘pull’ only) and in the presence of a spatial repellent (‘push-pull’), indicating that in its current configuration the tested ‘pull’ does not provide a valuable addition to a spatial repellent. The chemical 2-butanone was ineffective in replacing CO2. Transfluthrin was detectable in the air space but with a strong linear reduction in concentrations over 5 m from release. The MB5 constituent chemicals were only irregularly detected, potentially suggesting insufficient release and concentration in the air for attraction. Conclusion This step-by-step evaluation of the selected ‘push’ and ‘pull’ components led to a better understanding of their ability to affect host-seeking behaviours of the malaria vector An. arabiensis in the peri-domestic space and helps to gauge the impact such tools would have when used in the field for monitoring or control.

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Section: Methodsmentioning

confidence: 99%

Evaluating putative repellent ‘push’ and attractive ‘pull’ components for manipulating the odour orientation of host-seeking malaria vectors in the peri-domestic space

et al. 2021

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“…External standards do not correct for losses that may occur during preparation of the sample. Using IS is usually more effective due to lower measurement uncertainty and therefore is more common in analytical chemistry [12].…”

Section: Internal Standard (Is)mentioning

confidence: 99%

Linearity of Calibration Curves for Analytical Methods: A Review of Criteria for Assessment of Method Reliability

Moosavi¹,

Ghassabian²

2018

Calibration and Validation of Analytical Methods - A Sampling of Current Approaches

104

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Calibration curve is a regression model used to predict the unknown concentrations of analytes of interest based on the response of the instrument to the known standards. Some statistical analyses are required to choose the best model fitting to the experimental data and also evaluate the linearity and homoscedasticity of the calibration curve. Using an internal standard corrects for the loss of analyte during sample preparation and analysis provided that it is selected appropriately. After the best regression model is selected, the analytical method needs to be validated using quality control (QC) samples prepared and stored in the same temperature as intended for the study samples. Most of the international guidelines require that the parameters, including linearity, specificity, selectivity, accuracy, precision, lower limit of quantification (LLOQ), matrix effect and stability, be assessed during validation. Despite the highly regulated area, some challenges still exist regarding the validation of some analytical methods including methods when no analyte-free matrix is available.

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“…This procedure is employed in voltammetry when the separation of peaks is not possible by varying SWV parameters, pH values, working electrode materials or supporting electrolytes. In such a case, this procedure is very attractive, once there is no need of reagent addition and electrode pretreatment, enabling a simpler and costless determination and can be easily automated .…”

Section: Introductionmentioning

confidence: 99%

Simple Strategy for Selective Determination of Levamisole in Seized Cocaine and Pharmaceutical Samples Using Disposable Screen‐printed Electrodes

et al. 2018

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Levamisole is the most common adulterant found in cocaine samples and its electrochemical determination in cocaine seized samples is a challenge due to peak overlapping with cocaine. Herein, we propose a deconvolution procedure for levamisole determination in seized cocaine samples using screen‐printed carbon electrodes (SPE). Square‐wave voltammetry in 0.04 mol L−1 Britton Robinson buffered solution (pH 8.0) was selected in combination with optimized SWV parameters (f=8 s−1, a=10 mV and ΔEs=1 mV) to result in the best peak resolution to apply the deconvolution procedure. Deconvoluted responses of levamisole in the presence of cocaine were similar to untreated signals of standard levamisole solutions in absence of cocaine. A linear response was obtained in the range of 20–100 μmol L−1 (r=0.995). The results obtained for the analysis of a seized cocaine sample was statistically similar to that obtained by gas chromatography. Other adulterants found in cocaine street samples (paracetamol, glucose, phenacetin, caffeine, boric acid and lidocaine) did not affect the treated of voltammetric responses of levamisole. A pharmaceutical sample containing levamisole was also analyzed on SPEs and a recovery of 93±2 % was obtained (no deconvolution required for this sample), showing great applicability of SPEs for forensic and pharmaceutical analyses.

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Internal standard versus external standard calibration: an uncertainty case study of a liquid chromatography analysis

Cited by 35 publications

References 5 publications

Evaluating putative repellent ‘push’ and attractive ‘pull’ components for manipulating the odour orientation of host-seeking malaria vectors in the peri-domestic space

Evaluating putative repellent ‘push’ and attractive ‘pull’ components for manipulating the odour orientation of host-seeking malaria vectors in the peri-domestic space

Linearity of Calibration Curves for Analytical Methods: A Review of Criteria for Assessment of Method Reliability

Simple Strategy for Selective Determination of Levamisole in Seized Cocaine and Pharmaceutical Samples Using Disposable Screen‐printed Electrodes

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