HPLC, ascorbate determination

Magnesium ascorbyl phosphate (6) was used as reference compound for the RP-HPLC-UVD determination of sodium risedronate (68) in pharmaceutical preparations . Co(II) reacts with 2,2 -bipyridylketone-2-picolylimine in the presence of Na L-ascorbate in a weakly alkaline solution to form a blue water-soluble complex with the absorption maximum at ca 580 nm. The absorbance at 580 nm is proportional to the concentration of Co(II) in the range 0.05-2.5 mg L , with RSD = 0.46%. Ni(II) and Cu(II) were tolerated up to 20 and 10 mg L , respectively, in the presence of Na citrate . 

Nonvolatile Nitrosamines In Tobacco. A method which we developed several years ago for the analysis of tobacco-specific nitrosamines (TSNA 31) involves extraction of tobacco with buffered ascorbic acid TpH 4.5) followed by partition with ethyl acetate, chromatographic clean-up on silica gel, and analysis by HPLC-TEA (Figure 9). Results obtained with this method for a large spectrum of tobacco products (Table IV), strongly support the concept that the levels of nitrate and alkaloids, and especially the methods for curing and fermentation, determine the yields of TSNA in tobacco products. Recent and as yet preliminary data from snuff analyses indicate that aerobic bacteria play a role in the formation of TSNA during air curing and fermentation. 

HPLC on a Cosmosil 5 Cis column, using a perchloric acid-acetonitrile eluent (pH 7.6), followed by CLD in the presence of hydrogen peroxide and bis(2,4,6-trichlorophenyl) oxalate (42), was applied to the determination of 1-aminopyrene (43a) and various diaminopyrenes (43b-d). Ascorbic acid was added to avoid oxidative degradation of the aminopyrenes in the presence of metals LOD in the sub-fmol range (SNR 3)147. A fast (less than 10 min) HPLC-ELCD method was proposed for determination of dopamine (19b) and its metabolites in microdialysates, using packed fused silica capillary columns LOD 0.05 Xg/L of dopamine in a 2 XL sample, RSD 3% (n = 10)148. 

More recently [635], a unique extraction step in supplemented foods, by using hot water and a precipitation solution, following by HPLC-ELD/UV analysis has been performed for the simultaneous determination of pyridoxine, thiamine, riboflavin, niacin, pantothenic acid, folic acid, cyanoco-balamin, and ascorbic acid. The mobile phase consisting of phosphate buffer and methanol has been modified in order to perform ion-liquid chromatography by adding l-octanesulfonic acid sodium salt. Furthermore, triethylamine has been also added to improve peak symmetry. 

S Zapata, J-P Dufour. Ascorbic, dehydroascorbic and isoascorbic acid. Simultaneous determinations by reverse phase ion interaction HPLC. J Food Sci 57 506 -511, 1992. 

JM Irache, I Ezpeleta, FA Vega. HPLC determination of antioxidant synergists and ascorbic acid in some fatty pharmaceuticals, cosmetics and food. Chromatographia 35 232-236,1993. 

JT Vanderslice, DJ Higgs. Quantitative determination of ascorbic, dehydroascorbic, isoascorbic, and dehydroisoascorbic acids by HPLC in foods and other matrices. J Nutr Biochem 4 184-190, 1993. 

V. Kmetec, Simultonous determination of acetylsalicylic, salicylic ascorbic and dehydroascorbic acid by HPLC, J. Pharm. Biomed. Anal., 70 1073 (1992). 

Studies were undertaken to determine how rHbl. 1 was modified by the oxygen mediated degradation of ascorbate. In the presence of ascorbate and 150ppm of oxygen the reverse phase HPLC profile of the hemoglobin was not significantly different from the control oxy-rHb without ascorbate (see Fig. 1)... 

The CFF-mediated conversion of salicylate to 2,5- and 2,3-DHBA and catechol was used as a semi-quantitative assay to determine the levels of redox-active Fe/Cu, as follows in 100 pi reaction mixture, containing 50 pi CFFs and salicylate and ascorbate (1 mM, each) in KH buffer was incubated for Ih at 37 C. To terminate the incubation, ice-cold TCA (3% final concentration) was added, and the suspensions were centrifuged at 12,000g for 1 min. The supernatant was analyzed for 2,5- and 2,3-DHBA and catechol by HPLC coupled to an electrochemical detector (HPLC-ECD), as previously described [10]. 

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