Organic acids analysis using

Many laboratories use quantitative urinary organic acid analysis as an alternative to a qualitative approach and may not use stable isotope dilution as a more rigorous means of quantitation. The results from EQA schemes in the area reflect this variability of practice and the lack of internationally agreed standardisation. 

Some important assays commonly used in biochemical genetics laboratories do not provide quantitative data (e.g. MPS-EP, qualitative urinary organic acid analysis, AA-TLC). In addition, all successful investigations depend heavily upon selection of the correct analytes to measure and the appropriate interpretation of the quantitative or qualitative results in their clinical context. These challenges suggest a requirement for external quality assessment or proficiency testing schemes that can inform participants about their performance in these areas when compared with other centres. 

In the absence of tandem mass spectrometry equipment, almost equally reliable estimations of the PA concentrations can be made using gas chromatography-mass spectrometry (GC-MS). A standard quadrupole instrument, such as the one used for organic acid analysis, will be sufficient. Depending on the derivative, a choice between positive and negative ionization will have to be made. In general, a more extensive prepurification of the biological samples, will have to be realized. 

Standard GC-MS used for organic acid analysis (see Chap. 3.1). Data regarding calibration and quality control in this procedure can be found in Chap. 3.1 of this book. 

Urinary organic acid analysis is useful for differentiating isolated carboxylase deficiencies from the biotin-responsive multiple carboxylase deficiencies. P-Hydroxyisovalerate is the most common urinary metabolite observed in isolated P-methylcrotonyl-CoA carboxylase deficiency, biotinidase deficiency, biotin holo-carboxylase synthetase deficiency, and acquired biotin deficiency. In addition to P-hydroxy-isovalerate, elevated concentrations of urinary lactate, methylcitrate, and P-hydroxypropionate are indicative of multiple carboxylase deficiency. 

The organic acid analysis in the urine of this child was consistent with biotin deficiency or multiple carboxylase deficiency. Biotin deficiency usually can be excluded unless there is a history of dietary indiscretion, such as consuming a diet containing raw eggs or few biotin-containing foods, or there is a history of prolonged parenteral hyperalimentation without biotin supplementation. Low serum biotin concentrations can be useful in differentiating... 

Analytical determination of organic acids is important for quality assurance purposes, as well as for consumer protection or even consumer interest. Limited chromatographic reports are available on the simultaneous determination of benzoic acid, sorbic acid, and the parabens, especially in food items. However, there is an increasing trend in using combinations of preservatives in the food industry, as well as in pharmaceutical formulations and cosmetic products, and such a method may become an essential tool in organic acid analysis (Saad et al., 2005). 

Complex matrices such as soil solutions or landfill leachates usually require clean up where interfering compounds are removed prior to organic acid analysis. Procedures used include removal of humin-like substance by passing through special cartridges or precipitation after... 

Overall, AEC is a well-developed separation technique which is widely applied for organic acid analysis. Some of the current trends include the implementation of eluent generators " development of and increased accessibility to ion chromatograph/MS systems which are now commercially available " miniamrization of complete ion chromatographic systems and the development of monolithic columns which have been used for fast analysis of inorganic... 

An abundance of information is also available on the analysis of fatty acids in biological matrices by HPLG, but only a few methods use HPLG for short-chain organic acid analysis in environmental matrices (Table 13.7). 

The extraction of intracellular metabolites was performed according to the method of Ruijter and Visser [13]. The samples for phosphorylated carbohydrate and organic acid analysis were concentrated using solid phase extraction (SPE) and vacuum evaporation, respectively, and stored at -70 °C before assays. The SPE was performed according to the method of Smits et al. [14]. 

Monofluoroacetate, a toxin from the poison leaf plant Dichapetalum cymosum, was isolated and analyzed on a specialty organic acid analysis column (2 = 210nm) using an aqueous 20 mM H3PO4 mobile phase [1580]. This compound waS well separated from formic, acetic, and propionic acids. Peak shapes were excellent and elution was complete in 35 min. Linearity was achieved over the range 25-... 

A difficulty in finding inborn errors of pyrimidine metabolism by metabolite screening procedures is the absence of a typical end-product, like uric acid is in the purine metabolism. Moreover, pyrimidine metabolism is not easily accessible for simple chromatographic screening techniques. Nevertheless, with more complicated methods we are able to evaluate patterns of urinary pyrimidine bases and nucleosides. With routine gas-liquid chromatography (GLC) as is used for urinary organic acid analysis strongly increased uracil and thymine concentrations can be discovered. 

With our routine GLC-system for iirinary organic acid analysis in use for the screening for inborn errors of metabolism we detected persistent uraciluria in a few children. One of these patients will be described briefly here. Another patient showed a persistent excretion of thymine and uracil both. This child has been studied more in detail the results will be given in the present paper. 

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