Reduction of carry-over in column-switching HPLC/MS system with automated system washing procedure for highly sensitive direct analysis of donepezil in dog plasma

2007 ◽  
Vol 43 (2) ◽  
pp. 683-690 ◽  
Author(s):  
Yoshiki Asakawa ◽  
Chinami Ozawa ◽  
Katsunobu Osada ◽  
Shoji Kaneko ◽  
Naoki Asakawa
Keyword(s):  
Direct Analysis ◽  
Column Switching ◽  
Automated System ◽  
Dog Plasma ◽  
Highly Sensitive ◽  
Carry Over

scholarly journals An automated system for selective and continuous measurements of vertical Thoron profiles for the determination of transport times near the ground

2013 ◽  
Vol 6 (1) ◽  
pp. 867-910
Author(s):  
D. Plake ◽  
I. Trebs
Keyword(s):  
Measurement System ◽  
Automated System ◽  
Transport Time ◽  
Reliable Determination ◽  
Plant Canopies ◽  
Highly Sensitive ◽  
Resistance Approach ◽  
Reactive Trace Gases ◽  
The Individual

Abstract. The quantification of in-canopy transport times is of a~major importance for the investigation of sources, sinks and net fluxes of reactive trace gases within plant canopies. The Damköhler number, which compares timescales of chemical reactions with transport times, is a widely applied measure to evaluate flux divergences. In this study, we present and evaluate a novel automated measurement system for selective vertical Thoron (Tn) profiles near the earth's surface and demonstrate its suitability for the direct and reliable determination of transport times within a natural grassland canopy. For the first time, we perform a rigorous determination of systematic and random uncertainties of Tn (and Rn) concentrations under field conditions for this type of measurement system. The obtained median precisions for three concentration classes (> 100 Bq m−3, 100–15 Bq m−3 < 15 Bq m−3) were 8.8%, 23.2% and 132.1% for Tn (and 16.6%, 25.0%, 99.2% for Rn). We calculate in-canopy transport times (τ) and propagate it's uncertainty from the individual errors of the Tn concentration measurements. A quality assessment of τ for the field experiment revealed a good data quality with 44% of the relative uncertainties below 50%. The occurrence of transport time uncertainties higher than 100% was caused by absolute Tn gradients lower than 70 Bq m−3, which was found for 22% of all determined transport times. In addition, the method was found to be highly sensitive to the Tn concentrations at the upper of two inlet heights (zu). Low values of CTnzu result in high absolute uncertainties of the transport time. A comparison of the measured τ with empirical parameterizations revealed the lowest scatter for the measured τ values. We found an excellent agreement of τ with transport times obtained by the in-canopy resistance approach used, e.g. in the SURFATM model during daytime, while the SURFATM model significantly overestimated transport times during nighttime.

scholarly journals Endocannabinoid levels in patients with Parkinson’s disease with and without levodopa-induced dyskinesias

2020 ◽  
Author(s):  
Camila Marchioni ◽  
Bruno Lopes Santos-Lobato ◽  
Maria Eugênia Costa Queiroz ◽  
José Alexandre S. Crippa ◽  
Vitor Tumas
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Endocannabinoid System ◽  
Column Switching ◽  
Healthy Controls ◽  
Highly Sensitive ◽  
Liquid Chromatography Tandem Mass ◽  
Csf Levels ◽  
Ultrahigh Performance Liquid Chromatography ◽  
Arachidonoyl Glycerol

AbstractBackgroundLevodopa-induced dyskinesias (LID) in Parkinson’s disease (PD) are frequent complications, and the endocannabinoid system has a role on its pathophysiology.ObjectiveTo test the hypothesis that the functioning of the endocannabinoid system would be altered in PD and in LID by measuring plasma and CSF levels of α-N-arachidonoylethanolamine (AEA) and 2-arachidonoyl-glycerol (2-AG) in patients with PD with and without LID and in healthy controls.MethodsBlood and CSF samples were collected from 20 healthy controls, 23 patients with PD without LID, and 24 patients with PD with LID. The levels of AEA and 2-AG were measured using a highly sensitive column switching ultrahigh-performance liquid chromatography-tandem mass spectrometry method.ResultsWhen pooled together, patients with PD had lower plasma and CSF levels of 2-AG and higher CSF levels of AEA compared to healthy controls (Mann-Whitney statistics = 303.0, p = 0.02). Patients with PD without LID had lower CSF levels of 2-AG (Kruskal-Wallis statistics = 7.76, p = 0.02) and higher CSF levels of AEA levels than healthy controls (Kruskal-Wallis statistics = 8.81, p = 0.01).ConclusionsThe findings suggest that the endocannabinoid system participates in the pathophysiology of PD symptoms, but its role in the pathophysiology of LID is still unclear.

scholarly journals An automated system for selective and continuous measurements of vertical thoron profiles for the determination of transport times near the ground

2013 ◽  
Vol 6 (4) ◽  
pp. 1017-1030 ◽  
Author(s):  
D. Plake ◽  
I. Trebs
Keyword(s):  
Measurement System ◽  
Automated System ◽  
Transport Time ◽  
Reliable Determination ◽  
Plant Canopies ◽  
Highly Sensitive ◽  
Resistance Approach ◽  
Reactive Trace Gases ◽  
The Individual

Abstract. The quantification of in-canopy transport times is of major importance for the investigation of sources, sinks and net fluxes of reactive trace gases within plant canopies. The Damköhler number, which compares timescales of chemical reactions with transport times, is a widely applied measure to evaluate flux divergences. In this study we present and evaluate a novel automated measurement system for selective vertical thoron (Tn) profiles near the Earth's surface and demonstrate its suitability for the direct and reliable determination of transport times within a natural grassland canopy. For the first time, we perform a rigorous determination of systematic and random uncertainties of Tn (and Rn) concentrations under field conditions for this type of measurement system. The obtained median precisions for three concentration classes (> 100 Bq m−3, 100–15 Bq m−3, < 15 Bq m−3) were 8.8%, 23.2% and 132.1% for Tn (and 16.6%, 25.0%, 99.2% for Rn). We calculate in-canopy transport times (τ) and propagate their uncertainty from the individual errors of the Tn concentration measurements. A quality assessment of τ for the field experiment during a period of 51 days revealed good data quality with 44% of the relative uncertainties below 50%. The occurrence of transport time uncertainties higher than 100% was caused by absolute Tn gradients lower than 70 Bq m−3 m−1, which was found for 22% of all determined transport times. In addition, the method was found to be highly sensitive to the Tn concentrations at the upper of the two inlet heights (zu). Low values of CTnzu result in high absolute uncertainties of the transport time. A comparison with empirical parameterizations revealed a much lower scatter for the τ values determined from our measurements. We found an excellent agreement with τ values obtained by the in-canopy resistance approach used, e.g., in the SURFATM model during daytime, while the SURFATM model significantly overestimated transport times during nighttime.

Sensitive LC-MS/MS Method for the Simultaneous Determination of Bendamustine and its Active Metabolite, γ-Hydroxybendamustine in Small Volume Mice and Dog Plasma and its Application to a Pharmacokinetic Study in Mice and Dogs

Drug Research ◽  
2017 ◽  
Vol 67 (09) ◽  
pp. 497-508 ◽  
Author(s):  
Devaraj Chandrashekar ◽  
Ponnayyan Suresh ◽  
Rajnish Kumar ◽  
Ravi Bhamidipati ◽  
Ramesh Mullangi ◽  
...  
Keyword(s):  
Pharmacokinetic Study ◽  
Small Volume ◽  
Internal Standard ◽  
Simultaneous Quantification ◽  
Liquid Liquid Extraction ◽  
Dog Plasma ◽  
Highly Sensitive ◽  
Regulatory Guidelines ◽  
Novel Method

AbstractA highly sensitive, specific and rapid LC-ESI-MS/MS method has been developed and validated for the simultaneous quantification of bendamustine (BM) and γ-hydroxybendamustine (HBM) in small volume (20 µL) mice and dog plasma using phenacetin as an internal standard (IS) as per regulatory guidelines. Both the analytes and IS were extracted from mice and dog plasma using a liquid-liquid extraction method. Chromatography was achieved on Atlantis dC18 column using an isocratic mobile phase (0.2% formic acid:acetonitrile, 25:75) at a flow rate of 0.40 mL/min. The total chromatographic run time was 3.0 min and the elution of BM, HBM and IS occurred at ~1.2, 1.2 and 2.0 min, respectively. A linear response function was established 0.11–518 ng/mL for both the analytes in mice and dog plasma. The intra- and inter-day accuracy and precisions were in the range of 3.46–12.9 and 3.63–8.23%; 1.15–9.00 and 7.86–9.49% for BM and HBM, respectively in mice plasma and 2.15–6.49 and 1.73–13.1%; 4.35–13.9 and 4.33–10.5% for BM and HBM, respectively in dog plasma. This novel method has been applied to a pharmacokinetic study in mice and dogs.

Analysis of Cholesterol in All Lipoprotein Classes by Single Vertical Ultracentrifugation of Fingerstick Blood and Controlled-Dispersion Flow Analysis

1992 ◽  
Vol 38 (9) ◽  
pp. 1898-1905 ◽  
Author(s):  
K R Kulkarni ◽  
D W Garber ◽  
C F Schmidt ◽  
S M Marcovina ◽  
M H Ho ◽  
...  
Keyword(s):  
Total Cholesterol ◽  
Low Density Lipoprotein ◽  
Flow Analysis ◽  
Density Lipoprotein ◽  
Direct Analysis ◽  
Lipoprotein Cholesterol ◽  
Air Bubbles ◽  
Highly Sensitive ◽  
Analytical System ◽  
Absorbance Curve

Abstract This new, highly sensitive analytical system, based on controlled dispersion of the flowing sample, gives a rapid, continuous, and direct analysis for cholesterol in all lipoprotein classes, separated by single vertical-spin density-gradient ultracentrifugation. In this Vertical Auto Profile-II fingerstick system, designated VAP-IIfs, a narrow-bore Teflon coil serves as the reactor with no segmentation of the analytical stream by air bubbles, in contrast to the Technicon AutoAnalyzer used in the VAP-I method. Concentrations of high-, low-, intermediate-, and very-low-density lipoprotein cholesterol and lipoprotein(a) cholesterol are determined by decomposing the spectrophotometric absorbance curve for the continuous analysis of the centrifuged sample, with use of software developed in this laboratory. Total cholesterol is determined from the total area under the absorbance curve. For assaying total cholesterol, the CV between aliquots within a rotor ranged from 1.35% to 3.15%; the CV between rotors was 2.45%. Because only 18 microL of sample is required, VAP-IIfs can be readily adapted to analysis for lipoprotein cholesterol profiles in capillary blood samples. Total cholesterol values by VAP-IIfs for fingerstick and venous samples from 23 subjects agreed well: slope = 1.01 (SD 0.03), intercept = -21 (SD 51) mg/L, Sy/x = 50 mg/L, and r = 0.992. Results by VAP-IIfs also correlated highly with results for duplicate samples analyzed at the Northwest Lipid Research Laboratories.

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