Determination of asymmetric Nα-acetyldimethylarginine in humans: A phase II metabolite of asymmetric dimethylarginine

2014 ◽  
Vol 452 ◽  
pp. 25-30 ◽  
Author(s):  
Jens Martens-Lobenhoffer ◽  
Roman N. Rodionov ◽  
Stefanie M. Bode-Böger
Keyword(s):  
Phase Ii ◽  
Asymmetric Dimethylarginine ◽  
Phase Ii Metabolite

Gas Chromatographic Determination of Poly chlorinated Biphenyls (as Aroclor 1254) in Serum: Collaborative Study

1989 ◽  
Vol 72 (4) ◽  
pp. 649-659
Author(s):  
Virlyn W Burse ◽  
Margaret P Korver ◽  
Larry L Needham ◽  
Chester R Lapeza ◽  
Elizabeth L Chester R ◽  
...  
Keyword(s):  
Phase I ◽  
Silica Gel ◽  
Phase Ii ◽  
Collaborative Study ◽  
Chlorinated Hydrocarbons ◽  
Aroclor 1254 ◽  
Relative Standard

Abstract A gas chromatographic-electron capture detection method for determining the concentration of polychlorinated biphenyls (PCBs) as Aroclor 1254 (AR 1254) in serum was evaluated through a 2-phase collaborative study. In Phase I, each collaborator's lot of Woelm silica gel (70-150 mesh) was evaluated for elution and recovery of AR 1254, which had been added in vitro at 25 ng/mL to a serum extract. In Phase II, each collaborator analyzed a series of bovine serum samples that contained the following: (1) in vitro-spiked AR 1254; (2) in vivo AR 1254 and 8 in vitro-spiked chlorinated hydrocarbons; (3) in vivo AR 1254 only; (4) 8 in vitro-spiked chlorinated hydrocarbons only; and (5) neither AR 1254 nor chlorinated hydrocarbons above the detection limit of the method. In Phase I, the average recovery of AR 1254 from silica gel for the 6 collaborators was 87.9 ± 15.44% (mean ± 1 SD; N = 18; range = 52.3-105.8%). In Phase II, the analysis of in vitro spikes of AR 1254 in serum at 8.58,16.8, 41.8, and 84.3 ppb gave mean (X) interlaboratory recoveries of 89.0, 83.3, 79.4, and 76.9%, respectively, with within-laboratory (repeatability) relative standard deviations (RSDr) of 18.8, 20.5, 10.2, and 14.1%, respectively, and among-laboratory (reproducibility) relative standard deviations (RSDR) of 21.5, 21.1, 14.6, and 20.8%, respectively. The determination of in vivo AR 1254 in samples containing approximately 10, 25, 50, and 100 ng/mL of AR 1254 resulted in interlaboratory means of 10,22,39, and 79 ng/mL, respectively, with RSDr = 6.7,9.7,6.4, and 5.8%, respectively, and RSDR = 20.6,16.0, 10.9, and 10.3%, respectively. The precision of the method for incurred AR 1254 showed a maximum RSDr of less than 10% and a maximum RSDR of less than 21% for a concentration range of 10-100 ng/mL. The accuracy of the method as demonstrated by the mean recovery of in vitro-spiked AR 1254 over a concentration range of 8.58-84.3 ng/mL was 82.2%. The method has been approved interim official first action.

Fast and reproducible chemical synthesis of zearalenone-14-β,D-glucuronide

2012 ◽  
Vol 5 (3) ◽  
pp. 289-296 ◽  
Author(s):  
H. Mikula ◽  
C. Hametner ◽  
F. Berthiller ◽  
B. Warth ◽  
R. Krska ◽  
...  
Keyword(s):  
Chemical Synthesis ◽  
Phase Ii ◽  
Enzymatic Synthesis ◽  
Direct Determination ◽  
Cost Effective ◽  
Reference Substance ◽  
Standard Equipment ◽  
Fusarium Mycotoxin ◽  
Acid Esters

The Fusarium mycotoxin zearalenone (ZEA) is mainly converted to the conjugate zearalenone-14-β,D-glucuronide (ZEA-14-GlcA) during phase II detoxification in humans and animals. This metabolite - previously described as zearalenone-4-O-β,D-glucuronide - is excreted via urine and could therefore serve as possible biomarker for ZEA exposure to estimate its intake. Direct determination of this substance is limited by the availability of a reference substance. So far, only the production of small amounts by enzymatic synthesis has been described. In this work, a fast and reproducible protocol for the chemical synthesis of ZEA-14-GlcA was developed, using substituted β-resorcylic acid esters as mycotoxin mimics and different glucuronyl donors for optimising the glycosylation (Königs-Knorr, trifluoroacetimidate method) and the deprotection step. This cost-effective procedure should be easily reproducible in other labs using standard equipment and common reagents.

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