Evaluation of Uncertainty in the Determination of Pesticide Residues in Tea using GC-ECD

2017 ◽  
Vol 19 (1) ◽  
pp. 18-24
Author(s):  
Yohanes Susanto Ridwan ◽  
Andreas Andreas ◽  
Dyah Styarini ◽  
Retno Yusiasih
Keyword(s):  
Pesticide Residues ◽  
Calibration Method ◽  
Standard Uncertainty ◽  
Uncertainty Component ◽  
Method Performance ◽  
Total Uncertainty ◽  
Key Indicator ◽  
Relative Standard ◽  
Calibration Solution ◽  
Pesticides Residue

Key indicator of quality in test results is the uncertainty value, which could be evaluated using several common approach. Uncertainty evaluation in a-endosulfan and bifenthrin in Oolong tea, and cypermethrin in green tea using bottom-up approach showed that uncertainty component arising from GC-ECD instrument calibration, method performance i.e. repeatability and recovery were the main contributors to total uncertainty. Uncertainty component arising from weighing, dilution factor, stock standard solution, calibration solution, and moisture correction had no significant effect to total uncertainty, hence they could be neglected. Relative standard uncertainty obtained for all of pesticides residue were 18.23, 10.44, dan 14.98% for a-endosulfan, bifenthrin, and cypermethrin, respectively. Comparison with 2/3 CV Horwitz of 17.33, 10.62, and 12.44% respectively for all pesticide residues indicated that the evaluation of uncertainties were realistic

scholarly journals Estimation of the Measurement Uncertainty of the High-Performance Anion-Exchange Chromatographic Determination of Carbohydrates in Soluble (Instant) Coffee

2004 ◽  
Vol 87 (3) ◽  
pp. 647-656 ◽  
Author(s):  
Paul Stöber ◽  
Véronique Giller ◽  
Lionel Spack ◽  
Jacques Prodolliet
Keyword(s):  
Measurement Uncertainty ◽  
Anion Exchange ◽  
High Performance ◽  
Standard Uncertainty ◽  
Calibration Model ◽  
Linear Calibration ◽  
Total Uncertainty ◽  
Instant Coffee ◽  
Relative Standard

Abstract The measurement uncertainty of the determination of free and total carbohydrates in soluble (instant) coffee using high-performance anion exchange chromatography with pulsed amperometric detection according to AOAC Method 995.13 and ISO standard 11292 was calculated. This method is important with regard to monitoring several carbohydrate concentrations and is used to assess the authenticity of soluble coffee. We followed the recommendations of the ISO, Eurachem, and Valid Analytical Measurement (VAM) guides: individual uncertainty contributions u(x) were identified, quantified, and expressed as relative standard deviations related to each specific source u(x)/x or RSD(x). Eventually, they were combined to yield the standard uncertainty and the relative standard uncertainty of a given carbohydrate concentration, c, that is respectively u(c) and u(c)/c. As a result of our study, we could demonstrate that the overall repeatability of the carbohydrate determination in duplicate, RSD(r); the repeatability of the integration of the peak area of the carbohydrate standards, RSD(rarea(ST)); and the uncertainty of the linear calibration model used in our laboratory, RSD (linST), are the most significant contributions to the total uncertainty. The u(c)/c values thus determined differ for each carbohydrate and depend on their concentrations. The least standard uncertainties that can be achieved are about 2.5%. The question of trueness in the total carbohydrate assay (determination of monosaccharides obtained upon hydrolysis of coffee oligo- and polysaccharides) was addressed. For this purpose, we analyzed the data of 2 different collaborative trials in which our laboratory took part.

scholarly journals Reducing the uncertainty of strain gauge amplifier calibration

ACTA IMEKO ◽  
2017 ◽  
Vol 6 (4) ◽  
pp. 69 ◽  
Author(s):  
Miha Hiti
Keyword(s):  
Strain Gauge ◽  
Low Voltage ◽  
Reference Value ◽  
Calibration Method ◽  
Standard Uncertainty ◽  
Relative Standard Uncertainty ◽  
Voltage Ratio ◽  
Relative Standard ◽  
Lower Uncertainty

<p class="Abstract">The article presents a method for calibration of strain gauge bridge amplifiers with improved uncertainty in low voltage ratio range. The procedure is based on combining traditional calibration of the amplifier at one point and linearity determination of the rest of the range. Traditional calibration is performed by a calibrated strain gauge bridge simulator at a reference value where measurement uncertainty is adequate, and the linearity is determined by a combinatorial calibration method with lower uncertainty, employing a special resistance circuit. Uncertainty in the lower part of the amplifier range can be significantly improved, resulting in a combined relative standard uncertainty below 2.5x10<sup>-5</sup> for the range from 0.04 mV/V to 2.5 mV/V.</p>

scholarly journals The Development and Validation of a Novel Designer Benzodiazepines Panel by LC–MS-MS

2021 ◽  
Author(s):  
Rebecca A Mastrovito ◽  
Donna M Papsun ◽  
Barry K Logan
Keyword(s):  
Illicit Drug ◽  
Liquid Extraction ◽  
Electrospray Tandem Mass Spectrometry ◽  
Method Performance ◽  
Internal Standards ◽  
Liquid Liquid Extraction ◽  
Relative Standard ◽  
Development And Validation ◽  
Positive Ion ◽  
Designer Benzodiazepines

Abstract Novel illicit benzodiazepines are among the most active areas of new illicit drug manufacture and use. We describe a method for the detection and quantification of etizolam and its metabolite α-hydroxyetizolam, flubromazolam, clonazolam, diclazepam, delorazepam, bromazepam, flubromazepam, phenazepam, flualprazolam, flunitrazolam, and nitrazolam in human whole blood. After addition of internal standards, samples are buffered and extracted using a liquid–liquid extraction. Analysis is performed using positive-ion electrospray tandem mass spectrometry for detection and quantitation. Calibration ranges were established based on the method performance and differed from compound to compound. Replicates at the lowest calibration point for each compound performed within 5% of CV (Coefficient of Variation). The correlation coefficient was &gt;0.990 for all compounds. Relative standard deviation for all compounds was ≤10% of CV and accuracy was  ±10% for both within- and between-run experiments. The maximum average intra- and inter-run imprecision were 5.7%. The maximum average intra- and inter-run imprecision was −8.7%. As part of evaluating the scope for relevancy, samples testing positive in immunoassay but confirmed to be negative in traditional benzodiazepine confirmation method were re-analyzed using this method. The presence of at least one novel benzodiazepine was identified in 70% of these samples. The appearance of these novel “designer” benzodiazepines demonstrates the challenge for toxicology testing and the need for continually updated confirmation methods.

scholarly journals Indirect and Direct Determination of the Casein Content of Milk by Kjeldahl Nitrogen Analysis: Collaborative Study

1998 ◽  
Vol 81 (4) ◽  
pp. 763-774 ◽  
Author(s):  
Joanna M Lynch ◽  
David M Barbano ◽  
J Richard Fleming
Keyword(s):  
Standard Deviation ◽  
Nitrogen Content ◽  
Relative Standard Deviation ◽  
Collaborative Study ◽  
Direct Determination ◽  
Raw Milk ◽  
Method Performance ◽  
Relative Standard ◽  
Milk Casein

Abstract The classic method for determination of milk casein is based on precipitation of casein at pH 4.6. Precipitated milk casein is removed by filtration and the nitrogen content of either the precipitate (direct casein method) or filtrate (noncasein nitrogen; NCN) is determined by Kjeldahl analysis. For the indirect casein method, milk total nitrogen (TN; Method 991.20) is also determined and casein is calculated as TN minus NCN. Ten laboratories tested 9 pairs of blind duplicate raw milk materials with a casein range of 2.42- 3.05℅ by both the direct and indirect casein methods. Statistical performance expressed in protein equivalents (nitrogen ⨯ 6.38) with invalid and outlier data removed was as follows: NCN method (wt%), mean = 0.762, sr = 0.010, SR = 0.016, repeatability relative standard deviation (RSDr) = 1.287℅, reproducibility relative standard deviation (RSDR) = 2.146%; indirect casein method (wt℅), mean = 2.585, repeatability = 0.015, reproducibility = 0.022, RSDr = 0.560℅, RSDR = 0.841; direct casein method (wt℅), mean = 2.575, sr = 0.015, sR = 0.025, RSDr = 0.597℅, RSDR = 0.988℅. Method performance was acceptable and comparable to similar Kjeldahl methods for determining nitrogen content of milk (Methods 991.20, 991.21,991.22, 991.23). The direct casein, indirect casein, and noncasein nitrogen methods have been adopted by AOAC INTERNATIONAL.

UHPLC/ESI-MS/MS Determination of 187 Pesticides in Wine

2016 ◽  
Vol 99 (2) ◽  
pp. 539-557 ◽  
Author(s):  
Jian Wang ◽  
Wendy Cheung
Keyword(s):  
Measurement Uncertainty ◽  
Electrospray Ionization ◽  
Pesticide Residues ◽  
Red Wine ◽  
White Wine ◽  
Tandem Ms ◽  
Fast Method ◽  
Intermediate Precision ◽  
Method Performance ◽  
Standard Calibration

Abstract This paper presents an ultra HPLC/electrospray ionization-tandem MS method to determine pesticides in wine. We adopted the quick, easy, cheap, effective, rugged, and safe (QuEChERs) method for extraction and used core-shell column to achieve ultra-HPLC to develop and validate a simple and fast method to analyze 187 pesticide residues in red and white wine samples. Pesticide residues were extracted from wine samples using QuEChERS. Ultra HPLC/electrospray ionization-tandem MS quantification was achieved using matrix-matched standard calibration curves with isotopically labeled standards or a chemical analogue as internal standards with an analytical range from 5.0 to 500.0 μg/L. The method performance characteristics that included overall recovery, intermediate precision, and measurement uncertainty were evaluated according to a nested experimental design. Generally, 98.4% (in red wine) and 96.8% (in white wine) of the pesticides had recoveries between 71 and 120%; 98.9% (in red wine) and 99.5% (in white wine) of the pesticides had the intermediate precision ≤20%; and 99.5% (in red wine) and 98.4% (in white wine) of the pesticides had measurement uncertainty ≤50%.

scholarly journals The NIST Johnson Noise Thermometry System for the Determination of the Boltzmann Constant

2017 ◽  
Vol 122 ◽  
Author(s):  
Nathan E. Flowers-Jacobs ◽  
Alessio Pollarolo ◽  
Kevin J. Coakley ◽  
Adam C. Weis ◽  
Anna E. Fox ◽  
...  
Keyword(s):  
International System ◽  
Standard Uncertainty ◽  
Boltzmann Constant ◽  
Correlated Noise ◽  
Johnson Noise ◽  
Noise Thermometry ◽  
Relative Standard ◽  
System Of Units ◽  
Johnson Noise Thermometry

In preparation for the redefinition of the International System of Units (SI), five different electronic measurements of the Boltzmann constant have been performed using different Johnson noise thermometry (JNT) systems over the past seven years. In this paper, we describe in detail the JNT system and uncertainty components associated with the most recent National Institute of Standards and Technology (NIST) determination of the Boltzmann constant: k = 1.380642 9(69) × 10−23 J/K, with a relative standard uncertainty of 5.0 × 10−6 and relative offset of −4.05 × 10−6 from the Committee on Data for Science and Technology (CODATA) 2014 recommended value. We discuss the input circuits and the approach we used to match the frequency response of two noise sources. We present new measurements of the correlated noise of the 4 K on-chip resistors in the quantum-accurate, pseudorandom, voltage-noise source, which we used to estimate the correlated, frequency-dependent, nonthermal noise in our system. Finally, we contrast our system with those used in other measurements and speculate on future improvements.

scholarly journals Validation of a PTB force-balanced piston gauge primary pressure standard

ACTA IMEKO ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 271
Author(s):  
Ahmed Salama Hashad ◽  
Wladimir Sabuga ◽  
Sven Ehlers ◽  
Thomas Bock
Keyword(s):  
Gas Flow ◽  
Rarefied Gas ◽  
Operation Mode ◽  
Experimental Methods ◽  
Effective Area ◽  
Standard Uncertainty ◽  
Operating Pressure ◽  
Pressure Balance ◽  
Piston Gauge ◽  
Relative Standard

Experimental methods using different pressure standards were applied to verify theoretical results obtained for the effective area of the piston-cylinder assembly (PCA) and for pressures measured with a force-balanced piston gauge (FPG). The theoretical effective area was based on the PCA’s dimensional properties defined via diameter, straightness and roundness measurements of the piston and cylinder, derived by gas-flow modelling using principles of the rarefied gas dynamics, and presented as two values: one obtained for absolute and the other for gauge pressure operation mode. Both values have a relative standard uncertainty of 5×10<sup>-6</sup>. The experimental methods chosen were designed to cover the entire operating pressure range of the FPG from 3 Pa to 15 kPa. Comparisons of the FPG with three different PTB pressure standards operated in different pressure ranges – a pressure balance, a mercury manometer and a static expansion system – were performed using the cross-float method and by a direct comparison of the generated pressures. For the theoretical and experimental effective area, as well as for pressures generated by the FPG and the reference standards, all the results demonstrated full agreement within the expanded uncertainties of the standards.

Inter-Laboratory Validation of 4-(Dimethylamino) Cinnamaldehyde (DMAC) Assay Using Cranberry Proanthocyanidin Standard for Quantification of Soluble Proanthocyanidins in Cranberry Foods and Dietary Supplements, First Action Official MethodSM: 2019.06

2020 ◽  
Author(s):  
Andrew D Birmingham ◽  
Daniel Esquivel-Alvarado ◽  
Michael Maranan ◽  
Christian G Krueger ◽  
Jess D Reed
Keyword(s):  
Dietary Supplements ◽  
Colorimetric Assay ◽  
Reference Standard ◽  
Limit Of Quantification ◽  
Method Performance ◽  
Performance Requirements ◽  
Relative Standard ◽  
Plate Reader ◽  
Acceptance Range ◽  
Accurate Quantification

Abstract Background Proanthocyanidins (PAC) are oligomers and polymers of flavan-3-ols with putative health benefits. PAC are prevalent in a wide variety of natural products and dietary supplements. Objective An inter-laboratory study was conducted to validate the 4-(dimethylamino)cinnamaldehyde (DMAC) colorimetric assay using a 96-well plate spectrophotometer for the accurate quantification of PAC in cranberry products and to evaluate the comparison of the procyanidin A2 (ProA2) dimer and cranberry PAC (c-PAC) reference standards. Methods Four test materials analyzed in this study included cranberry fiber powder, cranberry extract powder, concentrated cranberry juice, and a solution of cranberry PAC (30%, w/v). The samples were homogenized, extracted, sonicated, centrifuged, and analyzed using a 96-well plate spectrophotometer. Results Linearity for both the ProA2 and c-PAC standards was determined from 4.053 to 50.666 µg/mL and from 13.520 to 135.95 µg/mL, respectively. The relative standard deviation of repeatability (RSDr) values for the four materials analyzed, using both ProA2 and c-PAC standards, met the Standard Method Performance Requirements (SMPR®). Inter-laboratory precision using Horwitz ratio (HorRat) values for the four materials analyzed, using both ProA2 and c-PAC standards, satisfies the acceptance range in Appendix K of the Official Methods of Analysis (2003): Guidelines for Dietary Supplements and Botanicals. The limit of quantification (LOQ) was estimated to be 3.16 µg/mL. Conclusions The results produced from this study demonstrate the utility of the c-PAC standard over the ProA2 standard and the advantages of using a 96-well plate spectrophotometer for the accurate quantification of PAC. Highlights The use of a 96-well plate reader and c-PAC reference standard in the DMAC method improves accuracy and percision for quantification of soluble proanthocyanidins in cranberry foods and dietary supplements.

scholarly journals Determination of Low-Level Agricultural Residues in Soft Drinks and Sports Drinks by Liquid Chromatography/Tandem Mass Spectrometry: Single-Laboratory Validation

2007 ◽  
Vol 90 (2) ◽  
pp. 521-533 ◽  
Author(s):  
Nathan Paske ◽  
Bryan Berry ◽  
John Schmitz ◽  
Darryl Sullivan
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
Tandem Mass Spectrometry ◽  
Pesticide Residues ◽  
Agricultural Residues ◽  
Soft Drinks ◽  
Coefficient Of Determination ◽  
Tandem Mass ◽  
Sports Drinks ◽  
Relative Standard

Abstract In this study, sponsored by PepsiCo Inc., a method was validated for measurement of 11 pesticide residues in soft drinks and sports drinks. The pesticide residues determined in this validation were alachlor, atrazine, butachlor, isoproturon, malaoxon, monocrotophos, paraoxon-methyl, phorate, phorate sulfone, phorate sulfoxide, and 2,4-dichlorophenoxyacetic acid (2,4-D) when spiked at 0.100 g/L (1.00 g/L for phorate). Samples were filtered (if particulate matter was present), degassed (if carbonated), and analyzed using liquid chromatography with tandem mass spectrometry. Quantitation was performed with matrix-matched external standard calibration solutions. The standard curve range for this assay was 0.0750 to 10.0 g/L. The calibration curves for all agricultural residues had coefficient of determination (r2) values greater than or equal to 0.9900 with the exception of 2 values that were 0.9285 and 0.8514. Fortification spikes at 0.100 g/L (1.00 g/L for phorate) over the course of 2 days (n = 8 each day) for 3 matrixes (7UP, Gatorade, and Diet Pepsi) yielded average percent recoveries (and percent relative standard deviations) as follows (n = 48): 94.4 (15.2) for alachlor, 98.2 (13.5) for atrazine, 83.1 (41.6) for butachlor, 89.6 (24.5) for isoproturon, 87.9 (24.4) for malaoxon, 96.1 (9.26) for monocrotophos, 101 (25.7) for paraoxon-methyl, 86.6 (20.4) for phorate, 101 (16.5) for phorate sulfone, 93.6 (25.5) for phorate sulfoxide, and 98.2 (6.02) for 2,4-D.

scholarly journals Extrinsic LiDAR/Ground Calibration Method Using 3D Geometrical Plane-Based Estimation

Sensors ◽  
2020 ◽  
Vol 20 (10) ◽  
pp. 2841
Author(s):  
Mohammad Ali Zaiter ◽  
Régis Lherbier ◽  
Ghaleb Faour ◽  
Oussama Bazzi ◽  
Jean-Charles Noyer
Keyword(s):  
Ground Plane ◽  
Ground Surface ◽  
Real Data ◽  
Calibration Method ◽  
Parameters Estimation ◽  
Parameters Optimization ◽  
Method Performance ◽  
Extrinsic Calibration ◽  
Extrinsic Parameters ◽  
The Stability

This paper details a new extrinsic calibration method for scanning laser rangefinder that is precisely focused on the geometrical ground plane-based estimation. This method is also efficient in the challenging experimental configuration of a high angle of inclination of the LiDAR. In this configuration, the calibration of the LiDAR sensor is a key problem that can be be found in various domains and in particular to guarantee the efficiency of ground surface object detection. The proposed extrinsic calibration method can be summarized by the following procedure steps: fitting ground plane, extrinsic parameters estimation (3D orientation angles and altitude), and extrinsic parameters optimization. Finally, the results are presented in terms of precision and robustness against the variation of LiDAR’s orientation and range accuracy, respectively, showing the stability and the accuracy of the proposed extrinsic calibration method, which was validated through numerical simulation and real data to prove the method performance.

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