Journal of Chemical Metrology

A scientific open access journal in the field of analytical chemistry and accreditation
Editor-in-Chief: Mustafa Özyürek
Book Review and Review Article Editor: John Warren

LATEST ARTICLES

Original Article

Uncertainty of small enthalpy effects measured by isothermal calorimetric titration

J. Chem. Metrol. (2021) in press ; 1 - 13
by Astrid Darnell , Lauri Sikk , Ly Porosk and Ivo Leito

Combination of low concentration, low binding affinity and small solution volume is increasingly more common in calorimetric studies of host-guest interaction, but it leads to very small enthalpy and entropy effects, which are difficult to measure accurately. The aim of this study was to evaluate the reliability of enthalpy determination under such conditions using isothermal titration calorimetry (ITC) with a small-volume microcalorimeter and to evaluate the expected accuracy (expressed as measurement uncertainty) on the example of a simple 1:1 binding reaction of 18-crown-6-ether with K+ cation. The investigation focused on whether or not it is possible to get meaningful results from experiments on such a system with low binding constant,  low concentration (logK ≈ 2), low Wiseman “c” parameter values (c < 1) and low total heat released in the studied system. A thorough estimation of measurement uncertainty was performed using the component-by-component (the “classical” GUM) approach to estimate the uncertainties of experimentally determined heat effects at individual titration points and applying those uncertainties to data fitting to obtain the K and ΔH values for the studied reaction. We found that it was possible to determine the reaction enthalpy ΔH of -26.6 kJ/mol with standard uncertainty of 1.1 kJ/mol. If we assume similar uncertainties for the other authors, the ΔH value found in this work is in good agreement with the majority of the literature ΔH values and those are in general in agreement with each other.

DOI
http://doi.org/10.25135/jcm.57.21.03.1994
(DOI number will be activated after the manuscript has been available in an issue.)
Keywords
Isothermal titration calorimetry Wiseman c parameter measurement uncertainty studying the binding of low-affinity systems
Available online: April 01, 2021
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Original Article

IInvestigation of aflatoxin and metal concentrations in animal feeds and feed ingredients from Turkey

J. Chem. Metrol. (2021) in press ; 1 - 13
by Yasemin Bakircioglu Kurtulus , Dilek Bakircioglu , Muhammet Kuscu , Nukte Topraksever and Orhan Destanoglu

The contents of aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin G1 (AFG1) aflatoxin G2 (AFG2), aluminium (Al), arsenic (As), barium (Ba), calcium (Ca), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), nickel (Ni), phosphorus (P), lead (Pb), selenium (Se), tin (Sn) and zinc (Zn) in animal feed samples in Turkey were screened. Eighty animal feeds and feed ingredients were collected from different cities in Turkey. Aflatoxins were determined using the HPLC instrument after pre-separation using immunoaffinity column, and also the instrument of ICP-MS was used for metal determinations. All types of animal feed samples have led concentrations lower than the maximum EU and Turkey regulation limit, while 1.25% and 11.8 of mixed and feed additive samples had AFB1 and Hg concentrations higher than the maximum limits, respectively. A single correlation analysis was used to determine the relationship between AFB1 and total AFs and metal contents in mixed animal feed samples (p<0.05). A strong positive correlation was found between As and AFB1 and total AFs contents; whereas Cr was correlated negatively to AFB1 and total AFs, using single correlation analyses.

DOI
http://doi.org/10.25135/jcm.56.21.01.1937
(DOI number will be activated after the manuscript has been available in an issue.)
Keywords
Animal feed; aflatoxins; metals; HPLC, ICP-MS; correlation analyses. © 2021ACG Publications. All rights reserved. aflatoxins metals HPLC ICP-MS correlation analyses
Available online: March 09, 2021
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Original Article

Simultaneous quantification of teneligliptin hydrobromide and metformin hydrochloride: An improved HPTLC method with implementation of Plackett-Burman design

J. Chem. Metrol. (2021) in press ; 1 - 11
by Mehul Patel , Divya Patel , Umang Shah and Hetaben M. Kachhiya

Simple, rapid, sensitive, robust, and validated high-performance thin-layer chromatography was developed for the simultaneous determination of anti-diabetic drugs Teneligliptin hydrobromide (TH) and Metformin hydrochloride (MH) in bulk and pharmaceutical formulation. HPTLC system equipped Camag Linomat V, TLC Scanner IV, Twin Trough chamber, Dual-wavelength UV Cabinet, and win CATS software V1.4.7 were used during the study. Separation of analytes were achieved using a pre-coated silica gel G60 F254 aluminum Sheets 10×10 cm2, with the thickness of 0.2 mm as stationary phase and a mobile phase comprising of Methanol: Ammonium sulfate (0.5 %w/v): Triethylamine (9: 2.7: 0.5 v/v/v). The detection wavelength was set at 237 nm. The Rf value of the TH and MH was 0.63 and 0.19, respectively. The method was validated using a dynamic linear range of  4-28 ng/band and 100-700 ng/band for TH and MH, respectively. The developed method was validated as per the ICHQ2 (R1) guideline. The statistical analysis proved that the method is accurate with 98.80–99.38 % w/v and 99.66–99.96 % w/v for TH and MH, respectively, and precise with less than 2 % RSD. The Plackett-Burman design was applied to check the robustness of the developed method. Finally, the method is termed as linear, precise, accurate, and robust. It can be implemented successfully for the routine analysis of pharmaceutical dosage forms comprising TH and MH and is appropriate for regulatory submission under regulatory flexibility.

DOI
http://doi.org/10.25135/jcm.55.20.11.1893
(DOI number will be activated after the manuscript has been available in an issue.)
Keywords
: Teneligliptin hydrobromide metformin hydrochloride high-performance thin-layer chromatography ICH guidelines simultaneous estimation quality by design
Available online: January 22, 2021
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Original Article

Measurement uncertainty evaluation for titrimetric determination of benzoic acid purity

J. Chem. Metrol. (2021) in press ; 1 - 14
by Lokman Liv

The uncertainty budget for the determination of benzoic acid purity by potentiometric titrimetry was proposed. For this purpose alcoholic potassium hydroxide solution was standardized with benzoic acid supplied from National Institute of Standards and Technology (NIST) (SRM 39j), then the purity of the benzoic acid sample was determined by the same way. Measurement uncertainty evaluation of the method was exhaustively evaluated according to the EURACHEM/CITAC Guide CG 4, JCGM 100: 2008 and EUROLAB Technical Report No.1/2007, based on the bottom-up approach. Moreover, these results were compared with the results based on the top-down approach according to the EUROLAB Technical Report No.1/2007 and NORDTEST: NT TR 537. The measurement uncertainty was separately evaluated for the factor determination and the purity determination of one and six samples of benzoic acid for the bottom-up approach. The uncertainty sources for the purity determination of benzoic acid were carbon dioxide mole fraction, nominal concentration of benzoic acid, factor of alcoholic potassium hydroxide, amount of titrant consumption, the molar mass of benzoic acid and sample amount, respectively. Among these, the highest contributions to the uncertainty budget were found to be the factor of alcoholic KOH solution and the amount of titrant consumption for one and six samples, respectively. The expanded uncertainties for one and six measurements based on the bottom-up approach were found as 0.508% and 0.509%, and the expanded uncertainty for six measurements based on the top-down approach was found as 0.114%.

DOI
http://doi.org/10.25135/jcm.54.20.11.1881
(DOI number will be activated after the manuscript has been available in an issue.)
Keywords
Benzoic acid traceability electrochemistry measurement uncertainty bottom-up approach top-down approach
Available online: January 11, 2021
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