scholarly journals Validation of an LC-MS/MS Method for the Quantification of Caffeine and Theobromine Using Non-Matched Matrix Calibration Curve

Molecules ◽  
2019 ◽  
Vol 24 (16) ◽  
pp. 2863 ◽  
Author(s):  
Vera M. Mendes ◽  
Margarida Coelho ◽  
Angelo R. Tomé ◽  
Rodrigo A. Cunha ◽  
Bruno Manadas
Keyword(s):  
Human Plasma ◽  
Calibration Curve ◽  
Considerable Effort ◽  
Caffeine Consumption ◽  
Internal Standards ◽  
Beneficial Effects ◽  
Calibration Curves ◽  
Accuracy And Precision ◽  
Precise Quantification ◽  
Surrogate Matrix

Caffeine is one of the most widely consumed psycho-stimulants. The study of the beneficial effects of caffeine consumption to decrease the risk of developing several neuropsychiatric pathologies is receiving increasing attention. Thus, accurate and sensitive methods have been developed, mainly by LC-MS/MS, in order to quantify caffeine and its metabolites. These quantifications of caffeine and its metabolites by LC-MS/MS require a considerable effort to select or find a surrogate matrix, without the compounds of interest, to be used in the calibration curves. Thus, we evaluated the possibility of using calibration curves prepared in solvent instead of calibration curves prepared in human plasma. Results show that the calibration curves prepared in solvent and in human plasma were similar by comparing their slopes and interceptions, and the accuracy and precision were within the limits of acceptance for both calibration curves. This work demonstrates that, by using internal standards, it is possible to use a calibration curve in solvent instead of a calibration curve in plasma to perform an accurate and precise quantification of caffeine and theobromine.

scholarly journals Simultaneous LC-MS/MS Determination of Sacubitril, Valsartan and LBQ657 in Human Plasma and Its Application to Clinical Study

2021 ◽  
Author(s):  
Yufeng Ni ◽  
Yujia Zhang ◽  
Chong Zou ◽  
Li Ding
Keyword(s):  
Human Plasma ◽  
Multiple Reaction Monitoring ◽  
Gradient Elution ◽  
Ionization Source ◽  
Internal Standards ◽  
Accuracy And Precision ◽  
Liquid Chromatography Tandem Mass ◽  
Multiple Reaction Monitoring Mode ◽  
Positive Ion

A rapid and reproducible liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated to simultaneously determine sacubitril, valsartan and a metabolite of sacubitril (LBQ657) in human plasma using sacubitril-d4 and valsartan-d3 as the internal standards. Following protein precipitation, the analytes were operated on an Ultimate® XB-C18 column (2.1 × 50 mm, 3.5 μm, Welch) with a gradient elution with acetonitrile, and 5 mM ammonium acetate and 0.1% formic acid in water as the mobile phase. The detection was performed on a Triple Quad™ 4000 mass spectrometer coupled with an electrospray ionization source (ESI) under positive-ion multiple reaction monitoring mode. The linearities are 2.00-4000, 5.00-10000 and 5.00-10000 ng mL-1 for sacubitril, valsartan and LBQ657, respectively. The accuracy and precision of intra- and inter-day, dilution accuracy, recovery and stability of the method were all within the acceptable limits and no matrix effect or carryover was observed. The suitability of the method was successfully demonstrated in terms of the quantification of sacubitril, valsartan and LBQ657 in plasma samples collected from healthy Chinese volunteers in a clinical trial.

Bioanalytical method development and validation of simultaneous analysis of telmisartan and hydrochlorthiazide in human plasma using LC-MS/MS

2016 ◽  
Vol 5 (03) ◽  
pp. 4862 ◽  
Author(s):  
Mathew George* ◽  
Lincy Joseph ◽  
Arpit Kumar Jain ◽  
Anju V.
Keyword(s):  
Human Plasma ◽  
Retention Time ◽  
High Performance ◽  
Method Development ◽  
Matrix Effects ◽  
Solid Phase ◽  
Internal Standard ◽  
Assay Method ◽  
Buffer System ◽  
Internal Standards

A simple, sensitive, rapid and economic high performance thin layer chromatographic method and a mass spectroscopic assay method has been developed for the quantification of telmisartan and hydrochlorthiazide combination in human plasma. The internal standards and analytes were extracted from human plasma by solid-phase extraction with HLB Oasis1cc (30mg) catridges. The scanning and optimization for the samples are done using methanol: water (50:50). The samples were chromatographed using reverse phase chromatography with C-18 column of different manufacturers like Ascentis C18 (150×4. 6, 5µ) using the buffer system Acetonitrile: Buffer (80:20%v/v) which consist of 2±0. 1Mm ammonium format at a flow rate of 0. 7ml/min at a column oven temperature 35±10c. The internal standard used was hydrochlorthiazide13c1, d2 and telmisartand3. The extraction techniques include conditioning, loading, washing and elution, drying followed by reconstitution of the dried samples. The volume injected was 10µl with the retention time of 3-4 min for telmisartan, 1-2 min for hydrochlorthiazide and for the internal standards the retention time was 3-4 min for telmisartand3 and 1-2 min for hydrochlorthiazide c13d2. The rinsing solution was Acetonitrile: HPLC grade water in the ratio (50:50). The above developed method was validated using various parameters like selectivity and sensitivity, accuracy and precision, matrix effects, % recovery and various stability studies. The method was proved to be sensitive, accurate, precise and reproducible. The preparation showed high recovery for the quantitative determination of telmisartan and hydrochlorthiazide in human plasma.

In-house Calibration of the International Sensitivity Index or Calibration Curve for Determination of the International Normalized Ratio

2004 ◽  
Vol 128 (3) ◽  
pp. 308-312
Author(s):  
William F. Brien ◽  
Linda Crawford ◽  
Anne Raby ◽  
Harold Richardson
Keyword(s):  
Calibration Curve ◽  
Oral Anticoagulants ◽  
International Normalized Ratio ◽  
Sensitivity Index ◽  
Improve Performance ◽  
Accuracy And Precision ◽  
The Stability ◽  
Method Of Assessment ◽  
International Sensitivity Index

Abstract Context.—The international normalized ratio (INR) has been used since 1983 to standardize prothrombin time results for patients on oral anticoagulants. However, significant interlaboratory variations have been noted. Attempts have been made to address these differences with the use of instrument-specific International Sensitivity Index (ISI) values and in-house calibration of ISI values. Objective.—To assess the performance of laboratories using a calibration curve for INR testing. Design.—Attempts to improve performance of the INR include the use of instrument-specific ISI values, model-specific ISI values, in-house calibration of ISI values, and more recently, the preparation of a calibration curve. Several studies have shown an improvement in performance using these procedures. In this study of licensed laboratories performing routine coagulation testing in the Province of Ontario, Canada, the determination of the INR by a calibration curve was compared with the laboratories' usual method of assessment. These methods were subsequently analyzed by comparing the results to instrument-specific ISI, model-specific ISI, and in-house calibrators. International normalized ratios derived by both methods were analyzed for accuracy and precision. The stability of a calibration curve was also investigated. Results.—Performance of INR testing has improved with use of a calibration curve or in-house calibrators. Conclusion.—The results confirm that either in-house calibrators or the calibration curve improve performance of INR testing. The calibration curve may be easier to use and appears stable up to 4 months.

A sensitive liquid-chromatographic method for determination of 3'-azido-3'-deoxythymidine (AZT) in plasma and urine.

1988 ◽  
Vol 34 (8) ◽  
pp. 1565-1568 ◽  
Author(s):  
M A Hedaya ◽  
R J Sawchuk
Keyword(s):  
Human Plasma ◽  
Prescription Drugs ◽  
Chromatographic Method ◽  
Internal Standard ◽  
Infectious Complications ◽  
Over The Counter ◽  
Internal Standards ◽  
Liquid Chromatographic Method ◽  
Liquid Chromatographic

Abstract We describe a liquid-chromatographic assay for AZT in human plasma and urine. This assay involves the use of two internal standards, allowing reference of AZT peaks to the appropriate internal standard, the choice depending on the range of concentrations encountered. This method is isocratic, specific, sensitive enough to allow quantification of AZT in concentrations observed clinically, and requires only 13 min of chromatographic time. We saw no interference from various over-the-counter and prescription drugs often used in treating the infectious complications of AIDS.

scholarly journals Radiocarbon Variations from Tasmanian Conifers: Results from Three Early Holocene Logs

Radiocarbon ◽  
1995 ◽  
Vol 37 (2) ◽  
pp. 361-369 ◽  
Author(s):  
Mike Barbetti ◽  
Trevor Bird ◽  
George Dolezal ◽  
Gillian Taylor ◽  
Roger Francey ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Calibration Curve ◽  
The Other ◽  
Early Holocene ◽  
Conifer Species ◽  
Middle Holocene ◽  
Calibration Curves ◽  
Lagarostrobos Franklinii ◽  
Floodplain Sediments ◽  
Good Coverage

Dendrochronological studies are being carried out on two conifer species in the Stanley River area of western Tasmania. The chronology for Huon pine (Lagarostrobos franklinii), with living trees up to 1400 yr old, extends back to 571 bc. Living celery-top pine (Phyllocladus aspleniifolius) trees are up to 500 yr old. Apart from living or recently felled trees, sections have been taken from 350 subfossil logs preserved in floodplain sediments. They range in age from >38 ka to modern, with good coverage for the periods 9–3.5 ka and from 2.5 ka to the present. We report here on 14C measurements of decadal samples from three early Holocene logs, between 10 and 9 ka bp, providing short (ca. 300-yr) records of atmospheric 14C variations when plotted against ring numbers. The southern hemisphere data from Tasmania can be compared and wiggle-matched with published 14C calibration curves from German oak and pine. One set of measurements covers the period, ca. 9280–8990 cal bp, overlapping the link between the Hohenheim “Main 9” and middle Holocene master oak chronologies. The other sets of measurements from Tasmania coincide; they span the period, ca. 9840–9480 cal bp, overlapping the end of the German Preboreal pine and the beginning of the oak chronologies. Our measurements confirm that this part of the calibration curve is a gently sloping 14C-age plateau (ca. 8900–8700 bp, between 10,000 and 9500 cal bp), and suggest interhemispheric 14C differences close to zero.

scholarly journals Analysis for Alpha-Pyrrolidinovalerophenone and Its 2-Oxo-PVP Metabolite in Plasma by Liquid Chromatography–Tandem Mass Spectrometry

2019 ◽  
Author(s):  
David M Andrenyak ◽  
David E Moody ◽  
Jonathan M Crites ◽  
Michael H Baumann
Keyword(s):  
Room Temperature ◽  
Rat Plasma ◽  
Sample Volume ◽  
Internal Standards ◽  
Accuracy And Precision ◽  
Assay Performance ◽  
Liquid Chromatography Tandem Mass ◽  
Assay Precision ◽  
Recreational Use ◽  
Positive Ion

Abstract Alpha-pyrrolidinovalerophenone (alpha-PVP), a novel psychoactive substance, has widespread recreational use. This with interest in its pharmacological effects creates a need for methods that measure alpha-PVP concentrations. We therefore developed a LC-MS/MS method that can quantitate alpha-PVP and 2-oxo-PVP in rat plasma using a 0.1-mL sample volume. Addition of internal standards (2.5 ng/mL alpha-PVP-d8/2-oxo-PVP-d6) was followed by liquid–liquid extraction with 1-chlorobutane:acetonitrile (4:1), evaporation and reconstitution with 0.1% formic acid. Extracts were analyzed by LC-MS/MS using an Agilent 1100 HPLC and a Thermo Scientific TSQ Quantum Access MS/MS, with a YMC ODS-AQ, 50 mm × 2 mm, 3 μm column. The mobile phase was 0.1% formic acid:acetonitrile gradient at a 0.2-mL/minute flow rate with positive ion electrospray. SRM was used for the analysis with transitions: alpha-PVP, 232 → 91; alpha-PVP-d8, 240 → 91; 2-oxo-PVP, 246 → 91; 2-oxo-PVP-d6, 252 → 91. Alpha-PVP and 2-oxo-PVP eluted at 6.4 and 8.9 min. Calibrators range from 0.25 to 500 ng/mL. Accuracy and precision evaluated quality control samples prepared at 0.75, 10 and 400 ng/mL. The intra-assay evaluation also included the 0.25-ng/mL LOQs prepared in six different blank plasma sources. The intra-assay accuracy ranged from 88.9 to 117.8% of the target, and the intra-assay precision ranged from 0.9 to 16.0%. The inter-assay accuracy ranged from 98.7 to 110.7% of the target, and the inter-assay precision ranged from 4.5 to 12.0%. Extraction recovery was at least 52% for alpha-PVP and 67% for 2-oxo-PVP. Ionization recoveries were at least 64% for alpha-PVP and 82% for 2-oxo-PVP. These losses did not adversely affect assay performance. Alpha-PVP and 2-oxo-PVP controls were stable at room temperature for up to 24 h and frozen for at least 36 days. Alpha-PVP and 2-oxo-PVP were also stable in processed samples (extracts) stored at room temperature for at least 24 days. The procedure was used to analyze rat plasma samples from a pharmacokinetic study.

scholarly journals Selection and Treatment of Data for Radiocarbon Calibration: An Update to the International Calibration (IntCal) Criteria

Radiocarbon ◽  
2013 ◽  
Vol 55 (4) ◽  
pp. 1923-1945 ◽  
Author(s):  
Paula J Reimer ◽  
Edouard Bard ◽  
Alex Bayliss ◽  
J Warren Beck ◽  
Paul G Blackwell ◽  
...  
Keyword(s):  
Calibration Curve ◽  
Quality Data ◽  
Calibration Data ◽  
High Quality ◽  
High Quality Data ◽  
Surface Ocean ◽  
Basic Assumptions ◽  
Calibration Curves ◽  
Curve Model ◽  
Radiocarbon Calibration

High-quality data from appropriate archives are needed for the continuing improvement of radiocarbon calibration curves. We discuss here the basic assumptions behind 14C dating that necessitate calibration and the relative strengths and weaknesses of archives from which calibration data are obtained. We also highlight the procedures, problems, and uncertainties involved in determining atmospheric and surface ocean 14C/12C in these archives, including a discussion of the various methods used to derive an independent absolute timescale and uncertainty. The types of data required for the current IntCal database and calibration curve model are tabulated with examples.

Importance of probe design for bioanalysis of oligonucleotides using hybridization-based LC-fluorescence assays

Bioanalysis ◽  
2019 ◽  
Vol 11 (21) ◽  
pp. 1917-1925 ◽  
Author(s):  
Yuhuan Ji ◽  
Yijiang Liu ◽  
Wanhong Xia ◽  
Alexander Behling ◽  
Min Meng ◽  
...  
Keyword(s):  
Quantitative Determination ◽  
Human Plasma ◽  
Peptide Nucleic Acid ◽  
Dynamic Range ◽  
Sample Volume ◽  
Probe Design ◽  
Assay Sensitivity ◽  
Accuracy And Precision ◽  
Fluorescence Assays

Aim: The importance of the length and/or structure of fluorescently labeled PNA (peptide nucleic acid) probes for quantitative determination of oligodeoxynucleotides (ODNs) is demonstrated in human plasma using hybridization-based LC-fluorescence assays. The length of the PNA probes impacts the peak shape and chromatographic separation of the resulting PNA/ODN hybridization complexes and affects assay sensitivity, dynamic range and carryover. Methods: For quantitative determination of an 18-mer phosphodiester ODN (DNL1818) in human plasma, an assay utilizing an Atto dye-labeled 12-mer PNA probe provided a linear quantitation range of 0.1–50 ng/ml with excellent accuracy and precision (within -5.3–7.73%). Conclusion: This method provides a convenient method for sensitive and specific quantification of ODNs in biological matrix with limited sample volume and no special extraction.

scholarly journals The analysis of acetaminophen (paracetamol) and seven metabolites in rat, pig and human plasma by U(H)PLC–MS

Bioanalysis ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 485-500
Author(s):  
Rebecca Dargue ◽  
Isobelle Grant ◽  
Leanne C Nye ◽  
Andy Nicholls ◽  
Theo Dare ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Sample Preparation ◽  
Oral Administration ◽  
Human Plasma ◽  
Wistar Rats ◽  
Rat Plasma ◽  
Mouse Serum ◽  
Internal Standards ◽  
Minimal Sample

A U(H)PLC–MS/MS method is described for the analysis of acetaminophen and its sulphate, glucuronide, glutathione, cysteinyl and N-acetylcysteinyl metabolites in plasma using stable isotope-labeled internal standards. P-Aminophenol glucuronide and 3-methoxyacetaminophen were monitored and semi-quantified using external standards. The assay takes 7.5 min/sample, requires only 5 μl of plasma and involves minimal sample preparation. The method was validated for rat plasma and cross validated for human and pig plasma and mouse serum. LOQ in plasma for these analytes were 0.44 μg/ml (APAP-C), 0.58 μg/ml (APAP-SG), 0.84 μg/ml (APAP-NAC), 2.75 μg/ml (APAP-S), 3.00 μg/ml (APAP-G) and 16 μg/ml (APAP). Application of the method is illustrated by the analysis of plasma following oral administration of APAP to male Han Wistar rats.

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