Acid concentration analysis organic acids

Metabolites are small molecules that participate as substrates or products in metabolic reactions essential for the normal function of a cell. This molecular class comprises a wide range of compounds, from amino acids to lipids, organic acids, and nucleotides (11). The wide range of concentration and different chemical properties make the analysis of these compounds a challenging task. Usually, high-resolution mass spectrometers and chemical derivatization strategies are necessary to resolve isobaric interferences, increase ionization efficiency, and overcome chemical background effects from the matrix-assisted laser desorption/ionization (MALDI) matrix or the tissue matrix itself (12). 

Amino acids. Sugars and Organic Acids were analysed as previously described (4). Total Volatiles determination. Volatiles composition and concentration in the samples of melon flesh were determined using a headspace sampler (HP 19393) coupled to a gas chromatograph (HP 5890). Approximately 5g of flesh was obtained by using a cork borer to remove a number of cores from around the equator of the fhiit. This was immediately sealed in a headspace vial, placed in the headspace sampler at a bath temperature of 100 C, equilibrated for 15min before analysis on an HP 5890 GC equipped with an FID detector and fitted with a 30m x 0.32mm i.d. OVl fused silica colunm. 

Some crude oils contain significant concentrations of organic acids, mainly napthenic acids, which are corrosive to carbon steel at temperatures above about 400 F (200°C), and may require the use of molybdeniun-containing austenitic stainless steels (i.e., AISI316 and 317). Determination of when to use alloys is done by analysis of the crude oil for acid content using ASTM D 974, Test Method for Acid and... 

Description of Method. Creatine is an organic acid found in muscle tissue that supplies energy for muscle contractions. One of its metabolic products is creatinine, which is excreted in urine. Because the concentration of creatinine in urine and serum is an important indication of renal function, rapid methods for its analysis are clinically important. In this method the rate of reaction between creatinine and picrate in an alkaline medium is used to determine the concentration of creatinine in urine. Under the conditions of the analysis, the reaction is first-order in picrate, creatinine, and hydroxide. 

The concentration of acid impurities is an important indication of the quality of petroleum products and the purity of organic solvents, plasticizers, mineral oils, food fats, and polymers. Methods are used to detect organic acids in such compounds have many disadvantages the alkalimetry - low sensitivity, especially in the determination of weak acids, the extraction-photometric method is laborious, instmmental methods are expensive. In addition, most of methods are commonly unsuitable for direct analysis. 

Investigated is the influence of the purity degree and concentration of sulfuric acid used for samples dissolution, on the analysis precision. Chosen are optimum conditions of sample preparation for the analysis excluding loss of Ce(IV) due to its interaction with organic impurities-reducers present in sulfuric acid. The photometric technique for Ce(IV) 0.002 - 0.1 % determination in alkaline and rare-earth borates is worked out. The technique based on o-tolidine oxidation by Ce(IV). The relative standard deviation is 0.02-0.1. 

A feed concentration of 15 g glucose and 15 g xylose per litre was used over a feed rate of 20-200 ml/hr. Samples were taken at successive points along the reactor length, and the usual analysis for glucose and xylose consumption, organic acid production and cell density were done. A kinetic model for the growth and fermentation of P. acidipropionici was obtained from these data. 

When comparing the dust-borne concentrations of butyric acid and p-cresol with the odour thresholds it seems that the concentrations are too small to be relevant for an odour nuisance. However, if the dust is removed from the gas phase of the air from animal houses the odour disappears (39), (40), (14). This supports the opinion of HAMMOND et al. (40) that the odor is concentrated on the dust particles. The authors conclude from their data that the concentration of the two odorants butyric acid and p-cresol is about 4TO7 greater on an aerosol particle than it is in an equal volume of air. Thus, an aerosol particle deposited on the olfactory organ carries odour equivalent to a much greater volume of air (40). These considerations indicate that dust from animal houses should be taken into account in connection with odour emission/immission measurements not only by chemical analysis but by sensory evaluations using olfactometers without dustfilters, as well. 

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. 

A volume equivalent to 0.25 mg of creatinine from 500 mL of urine of a healthy adult donor is analyzed as described above. The collection is then spiked with up to ten organic acids (1 mg/ml stock solutions), selected from those with an active calibration curve by GC-MS TIC, to mimic a concentration of 100 pg acid/mg creatinine. The spiked collection is aliquoted into screw-cap vials during continued mixing, then stored frozen. For GC-MS SIM analysis, all compounds listed in Table 3.1.5 are included in the abnormal control, at a concentration matching the fourth point of the calibration curve (1 1 molar ratio to the labeled internal standard, see Table 3.1.5). 

Acylcarnitine analysis was first performed in urine specimens in the evaluation of patients with organic acidemias. However, because it was found that acylcarnitine analysis of plasma is more informative for the diagnosis of FAO disorders than analysis of urine specimens, plasma has become the preferred specimen [17]. It is only recently that it was shown that urine acylcarnitine analysis still has a role in the diagnostic evaluation of patients with organic acidurias but uninformative or borderline abnormal results of plasma acylcarnitine and urine organic acid analysis [18-21]. In our laboratory, sample preparation and analysis is identical to that of plasma once a urine aliquot has been prepared that is based on the creatinine concentration. 

With regard to AADC, vanillactic acid (a metabolite of 3-MD) appears in the urine and can be detected by organic acid analysis. As predicted, an increase in urinary vanillactic acid has also been reported in PNPO deficiency. The PLP concentration in CSF, which can be determined by HPLC, is also reported to be decreased in PNPO deficiency. Mutation analysis can also now confirm or refute a suggestion of PNPO deficiency. 

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