Organic acid ‘analyser

Checking the Purification. The purity of the dry re-crystallised material must now be determined, as it is possible that repeated recrystallisation may be necessary to obtain the pure material. The purity is therefore checked by a melting-point determination, and the recrystallisation must be repeated until a sharp melting-point is obtained. Should the compound have no well-defined melting-point e.g.y the salt of an organic acid or base), it must be analysed for one suitable component element, until its analysis agrees closely with that theoretically required. 

Fig. 12.5 Determination of carbon-bonded sulphur, ester sulphate and total organic sulphurfrom analyses of total sulphur, hydriodic acid reduction, extractable inorganic sulphate, HCI digestion and Zn-HCI reduction.

Chen et al. (1997a) analysed sodium saccharin in soft drinks, orange juice and lemon tea after filtration by injection into an ion-exclusion column with detection at 202 nm. Recoveries of 98-104% were obtained. They reported that common organic acids like citric and malic and other sweeteners did not interfere. Qu et al. (1999) determined aspartame in fruit juices, after degassing and dilution in water, by IC-PAD. The decomposition products of aspartame, aspartic acid and phenylanaline were separated and other sweeteners did not interfere. The recoveries of added aspartame were 77-94%. Chen et al. (1997b) separated and determined four artificial sweeteners and citric acid. 

An extractive spectrophotometric procedure based on the complexation of reduced Iron(II) with 5-Chloro-7-iodo-8-hydroxyquinoline (CIHQ) for the estimation of micro amounts of vitamin C. The resulting brown colored complex was extracted into chloroform to give a reddish brown extract which shows an absorption band at 485 nm. This chelate was formed immediately and the apparent molar absorptivity and Sandell s sensitivity for vitamin C was found to be 8.5 x 105 dm3 mol"1 cm 1 and 2.072xl0 4g cm 2. Linear relationship between absorbance and concentration of ascorbic acid is observed up to 0.8 pg ml"1. Interference studies of different substances including sugars, vitamins and amino acids, metal ions and organic acids were carried out. The utility of the method was tested by analysing some of the marketed products of vitamin C... 

Surface-modified silica gels are used for a variety of separations, but organic polymer-based stationary phase materials are more useful for long-term operations, such as for an amino acid analyser and size-exclusion liquid chromatography. 

Hydrogen oxidation Iron reduction H2 Organic acids N03- Fe - (oxyhydroxides) OO2 Organic acids Identified from molecular analyses Mesophilic bacteria and hyperthermophilic archaea... 

Fig. 3.1.6 GC-MS TIC organic acid profile of a patient with methylmalonic acidemia, a sample volume corresponding to 0.25 mg creatinine (standard procedure), b 10 x dilution (0.025 mg creatinine). Peak legend 1 methylmalonic acid (note the characteristic broad shape and spike, 2 urea, 3 citric acid, 4 2-methylcitric acid (two peaks). There was a fourfold difference in the measurement of methylmalonic acid excretion between the two analyses, with a substantial underestimation in the undiluted specimen...

Organic carbon analyses were made in duplicate by a combustion train method in the Microanalytical Laboratory, School of Chemistry, University of Minnesota, and Kjeldahl nitrogen analyses were done in triplicate in the Minnesota State Board of Health Laboratory. Averages of the readings are used here (Table III and VI) and are rounded off to the second decimal. Carbonate was removed from the samples by treatment with 0.5N hydrochloric acid prior to the carbon analyses. 

We thank L. R. Mattick for organic acid, methyl anthranilate, and anthocyanin analyses W. B. Robinson for advice and technical assistance and R. F. Belscher for must and wine analyses. 

---