High-performance liquid chromatography of bile pigments: separation and characterization of the urobilinoids

The detailed analysis of faecal bile pigments by high-performance liquid chromatography is described. Non-aqueous reversed-phase systems with acetonitrile-dimethyl sulphoxide or acetonitrile-dimethyl sulphoxide-methanol as the mobile phase on C1, C8 or C18-bonded silica are used for the group separation of verdinoids, violinoids and urobilinoids. A silica column, with acetonitrile-water-tetraethylene-pentamine as mobile phase, separates the laevorotatory stercobilin (C33H46N4O6) and half-stercobilin (C33H44N4O6) from the optically inactive urobilin (C33H42N4O6). The diastereoisomers are resolved by converting the urobilinoids into their dimethyl esters before chromatography on a silica column with n-heptane-methyl acetate-methanol containing 1% of diethylamine as the solvent system.

Determination of delta-aminolaevulinic acid synthase activity in human bone marrow using high performance liquid chromatography

A high performance liquid chromatographic (HPLC) method is described for the rapid and specific determination of the activity of the enzyme delta-aminolaevulinic acid synthase (ALA-S) in mitochondria prepared by sonication of human bone marrow cells. After incubation with 14C-alpha-ketoglutarate the 14C-delta-aminolaevulinic acid (ALA) formed is converted to a pyrrole derivative, 2-methyl-3-carbethoxy-4-(3-propionic acid) pyrrole. This is isolated by reversed-phase ion-pair chromatography on a Hypersil-SAS column with methanol-water (45:155, v/v) in the presence of 0.005 mol/l 1-heptanesulphonic acid (PIC B-7) as the mobile phase. The radioactivity of the isolated pyrrole is determined by scintillation counting. The optimal substrate concentration and pH were 0.17 mmol/l alpha-ketoglutarate and pH 7.4, with an optimal period of sonication of 18s. Under these conditions ALA production was proportional to the concentrations of erythroblasts in the initial sample and was linear with time up to 60 min. The addition of pyridoxal phosphate (PLP) did not affect ALA-S activity in normal subjects. The mean ALA-S activity in 10 haematologically normal control subjects was found to be 318.8 pmol.10-6 erythroblasts.h-1 (S.D. 125.8, range 193-444.6).

Corrosion of mild and stainless steel by four tropical Desulfovibrio desulfuricans strains

The corrosion potential of four tropical Desulfovibrio desulfuricans isolates was determined using a semicontinuous batch culture technique in a 56-day test incubated at 37 degrees C. The corrosion potentials for mild and stainless steel of marine or brackish water isolates (0.55 and 0.0026 mg cm-2 day-1) were observed to be approximately twice those of freshwater isolates (0.23 and 0.0014 mg cm-2 day-1). Under comparable experimental conditions of severe anaerobic corrosion, stainless steel was found to be over 200 times more resistant than mild steel.

High-performance liquid chromatography of bile pigments: application to the determination of unconjugated bilirubin in serum

A rapid, sensitive and specific method for the determination of unconjugated bilirubin in serum is described. Reversed-phase chromatography on short-chain alkylsilica (C2) or octadecylsilica (C18) with acetonitrile--dimethylsulphoxide--water as eluent is used for the separation of bilirubin. The method is applied to the analysis of bilirubin in patients with disorders associated with jaundice.

Determination of 5-aminolaevulinic acid and porphobilinogen by high-performance liquid chromatography

A strong anion-exchange column coupled to a strong cation-exchange column with acetate buffer as eluent or reversed-phase ion-pair chromatography on octadecylsilica with methanol-water containing 1-heptanesulphonic acid as the mobile phase is described for the simultaneous separation of 5-aminolaevulinic acid and porphobilinogen. The separation is applied to the development of a fast and simple method for determining the activity of the enzyme aminolaevulinic acid dehydrase in human erythrocytes. 5-Aminolaevulinic acid is used as the enzyme substrate and the enzyme activity is expressed as micromoles of porphobilinogen formed per ml of erythrocytes in 1 h at 38 degrees. 5-Aminolaevulinic acid and porphobilinogen can also be separated from the urine of prophyric patients but the UV detector has insufficient sensitivity for the determination of 5-aminolaevulinic acid.

Specific method for determining uric acid in serum using high-performance liquid chromatography and gas chromatography-mass spectropmetry

A method using a combination of high-performance liquid chromatography and stable-isotope dilution-mass spectrometry is described for the specific quantitation of uric acid in serum. The procedure involves addition of a known amount of [1,3,9-15n]uric acid, as intenral standard, to the serum sample followed by equilibration with the endogenous analyte. After separation from serum proteins, cationic and neutral compounds by anion-exchange chromatography, the purified uric acid is converted into its tetraethyl derivatives. High-performance liquid chromatography is used to isolate the three major isomeric derivatives for measurement of the isotope ratio m/e 280 to m/e 283. This ratio gives the relative abundances of the molecular ions of natural and of labelled tetraethyluric acid, and from it the amount of uric acid in the original serum specimen is determined. Effective separation of tetraethyluric acid isomers can be achieved by adsorption or reversed-phase high-performance liquid chromatography using n-heptane-isopropanol (80:1, v/v) and methanol-water (3:2, v/v), respectively, as solvent systems.

Towards a definitive assay of creatinine in serum and in urine: separation by high-performance liquid chromatography

A fast and sensitive method for the separation of serum and urinary creatinine is described. For the preliminary purification of serum and urine, a cation-exchange column is used to remove protein, anions and neutral compounds prior to isolation of creatinine by high-performance liquid chromatography. A reversed-phase system with 0.01 M ammonium acetate solution as the mobile phase can separate creatinine in 7.5 min at a flow-rate of 1 ml/min. The purity of the separated creatinine is proved by derivatization using trifluoracetic anhydride, followed by gas chromatography and mass spectrometry. Although this method of purification was designed for incorporation into a definitive assay, the ease and speed of analysis makes is very attractive for routine clinical use.

The differentiation of the porphyrias by means of high pressure liquid chromatography

The analysis of faecal and urinary porphyrins by high pressure liquid chromatography (H.P.L.C.) provides characteristic profiles and facilitates rapid diagnosis of variegate (porphyria cutanea tarda hereditaria), symptomatic porphyria (porphyria cutanea tarda symptomatica), hereditary coproporphyria, acute intermittent porphyria, erythro-hepatic protoporphyria and congenital porphyria (erythropoietic porphyria).