Liquid chromatography dilution assays

Jansen, E. E. W., Gibson, K. M., Shigematsu, Y., Jakobs, C., and Verhoeven, N. M. (2006). A novel, quantitative assay for homocamosine in cerebrospinal fluid using stable-isotope dilution liquid chromatography-tandem mass spectrometry. J. Chromatogr. B Arnlyt. Technol. Biomed. Life Sci. 830,196-200. 

In a high-pressure liquid chromatography assay of aspirin tablets, 10 extracts are made and the extracts are diluted with mobile phase solution, which consists of acetonitrile/0.1 M sodium acetate buffer pH 4.5 (10 90) and analysed sequentially. If the rate constant for the degradation of aspirin in the mobile phase is O.OfOl h " at room temperature how long can the andyst store the solutions at room temperature before the degradation of the analyte is greater than 0.5% ... 

Freisleben, A., Sehieberle, P, Ryehlik, M. (2003 May). Specific and sensitive quantification of folate vitamers in foods by stable isotope dilution assays using high-performance liquid chromatography-tandem mass speetrometry. Anal. Bioanal. Chem., 376 2), 149-156. 

MTHF was initially measured by microbiological and radioisotope dilution assay [12, 13], and later by high-pressure liquid chromatography (HPLC) using electrochemical (EC), ultraviolet, or fluorescence detection [14-16]. Compared to other methods, EC detection is more sensitive. 

Preferably, high pressure liquid chromatography (hplc) is used to separate the active pre- and cis-isomers of vitamin D3 from other isomers and allows theic analysis by comparison with the chromatograph of a sample of pure reference j-vitamin D3, which is equilibrated to a mixture of pre- and cis-isomers (82,84,85). This method is more sensitive and provides information on isomer distribution as well as the active pre- and cis-isomer content of a vitamin D sample. It is applicable to most forms of vitamin D, including the more dilute formulations, ie, multivitamin preparations containing at least 1 lU/g (AOAC Methods 979.24 980.26 981.17 982.29 985.27) (82). The practical problem of isolation of the vitamin material from interfering and extraneous components is the limiting factor in the assay of low level formulations. 

Lindenmeier, M., Schieberle, P. and Rychlik, M. (2004) Quantification of ochratoxin A in foods by a stable isotope dilution assay using high-performance liquid chromatography-tandem mass spectrometry,/. Chromatogr. A, 1023 (1), 57-66. 

A stable isotope dilution assay using mass spectrometry to measure insulin, proinsulin, and C-peptide has been developed. The difference in mass among the three analytes allows specific measurement of each protein. Comparison of patient samples revealed that most, but not all, results were higher by immunoassay than mass spectrometry. Thus immunoassays may overestimate insulin, particularly at low concentrations. The high protein concentration in the serum requires extraction of proteins (e.g., by immunoaffinity) and purification by high-performance liquid chromatography (HPLC) before quantification by mass spectrometry. This method is not suitable for routine laboratory analysis. 

G Singh, V Arora, PT Fenn, B Mets, IA Blair. A validated stable isotope dilution liquid chromatography tandem mass spectrometry assay for trace analysis of cocaine and its major metabolites in plasma. Anal Chem 71 2021—2027, 1999. 

Ravanat, J.L., Duretz, B., Guiller, A., Douki, T., and Cadet, J. (1998) Isotope dilution high-performance liquid chromatography-electrospray tandem mass spectrometry assay for the measurement of 8-oxo-7,8-dihydro-2 -deoxyguanosine in biological samples. 

RychUk, M. 2008. Quantification of free coumarin and its liberation from glucosylated precursors by stable isotope dilution assays based on liquid chromatography-tandem mass sp>ec-trometiic detection. /. Agric. Food Chem. 56(3) 796-801. 

Sample Handling. Enzymes Immobilized Enzymes Enzyme-Based Assays. Fluorescence Clinical and Drug Applications. Gas Chromatography Mass Spectrometry. Infrared Spectroscopy Near-Infrared. Isotope Dilution Analysis. Liquid Chromatography Column Technology Instrumentation. Sensors Overview. 

See also Activation Anaiysis Neutron Activation. Atomic Emission Spectrometry Principies and Instrumentation. Bleaches and Sterilants. Chiroptical Analysis. Chromatography Principles. Conductimetry and Oscillometry. Coulometry. Fire Assay. Food and Nutritional Analysis Overview. Gas Chromatography Principles. Gravimetry. Indicators Redox. Infrared Spectroscopy Overview. Ion Exchange Oven/iew. Isotope Dilution Analysis. Lipids Fatty Acids. Liquid Chromatography Size-Exclusion. Radiochemical... 

The use of solid-phase extraction cartridges is now well established in the analysis of clinical specimens. However, although this method provides efficient purification of the sample, it may lead to a loss of protein-bound vitamins. Direct injection of plasma samples into liquid chromatography (LC) columns is possible in some applications. Dilute filtered or centrifuged urine can be injected in certain LC applications, as is the case in urinary riboflavin assay. 

Maunsell, Z. Wrighf D.J. Rainbow, SJ. Routine isotope-dilution liquid chromatography tandem mass spectrometry assay for simultaneous measurement of the 25-hydroxy metabolites of vitamins D2 and D3. CHn. Chem. 2005, 51 (9), 1683-1690. 

Crnogorac, G., Schwack, W. (2007) Determination of dithiocarbamate fungicide residues by liquid chromatography-mass spectrometry and stable isotope dilution assay. Rapid Communications in Mass Spectrometry, 21,4009-4016. 

A 96-well microtitre plate assay with microcomputer analysis has simplified the microbiological assay making it less laborious, less time-consuming and more reproducible. Recently, an automated 96-well plate isotope-dilution tandem mass spectrometry method and an ultra-performance liquid chromatography-tandem mass spectrometry method have been developed and validated for the quantification of synthetic folic add in folate-fortified breads (Fazili and Pfeiffer 2004 Chandra-Hioe et al. 2011). 

Rychlik, M., Netzel, M., Pfannebecker, I., Frank, T., and Bitsch, I., 2003. Application of stable isotope dilution assays based on liquid chromatography-tandem mass spectrometry for the assessment of folate bioavailability. Journal of Chromatography B. 792 167-176. 

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