Total phosphorus determination in human bile. Comparison between two spectrometric methods

Quantitation of major choline fractions in milk and dietary supplements using a phospholipase d bioreactor coupled to a choline amperometric biosensor

Current analytical methods lack the capacity of simultaneous determination of the content of free choline and phosphatidyl-bound choline, mainly phosphatidyl choline, in raw milk. Quantitative determination of total, free, and phosphatidyl-bound choline in milk and a dietary supplement is described using a phospholipase D packed bioreactor coupled to a choline oxidase-based amperometric biosensor. The response for choline and phosphatidyl choline was linear up to 0.5 mM and 1 mM, respectively, and the detection limits were 0.02 and 0.03 mM, respectively. The conversion efficiency of phosphatidyl choline to choline was 50% at 0.2 mL min(-1). The within days coefficient of variation for choline and phosphatidyl choline determination in milk samples was 2.8% and 3.2%, respectively. With the addition of an acid hydrolysis step, the method can quantify the concentrations of total, free, phosphatidyl-bound, and non-phosphatidyl-bound choline esters, thus permitting determination of major choline fractions in a complex matrix.

Determination of choline containing phospholipids in serum, bile and amniotic fluids by the derivative enzymatic–spectrophotometric method

A comparison was performed of the analytical results obtained by applying a well-known enzymatic-spectrophotometric method for the determination of choline containing phospholipids in biological human fluids (sera, bile and amniotic fluids) following the standard procedure method, or else using the first or second derivative methods. In terms of result reproducibility the comparison was extended to include also a biosensor-based method developed in recent years by the present authors. Some advantages are associated with using the first derivative method in the case of serum samples containing blood traces, especially via the 'Gran's plot' method.

Determination of lecithin drug specialties and diet integrators; by means of first or second derivative enzymatic-spectrophotometric analysis

The possibility has been investigated of applying derivative analysis to a classical enzymatic-spectrophotometric method for lecithin determination for the purpose of developing an analytical direct method that does not require long pretreatment of the test sample even in the case of turbid samples. Several samples of drugs and food integrators containing lecithin were thus tested using both the standard and the derivative method and then comparing the results obtained. The RSD% values of measurements on real (food or drugs) samples were always <2.5. Using a first derivative spectrophotometric method, average recovery was always between 102 and 105%.

Analysis of lecithin in pharmaceutical products and diet integrators using a new biosensor operating directly in non aqueous solvent

One of the first examples of a bienzymatic organic phase enzyme electrode (OPEE) is described. It was obtained using two enzymes (phospholipase D and choline oxidase), both immobilised in kappa-Carrageenan gel and, as electrochemical transducer, an amperometric gas diffusion electrode for oxygen. The response of the biosensor was recorded and its sensitivity, linearity range, response time evaluated. Lastly drugs and diet products containing lecithin were analysed using the new biosensor device working in an organic mixture.

Determination of inorganic phosphate in drug formulations and biological fluids using a plant tissue electrode

A suitable biosensor for the analysis of inorganic phosphate was developed by coupling the enzyme glucose oxidase to a slice of potato (Solanum tuberosum) containing the acid phosphatase, and using an amperometric Clark electrode as an indicating sensor. Phosphate concentration can be determined from its inhibition on the acid phosphatase activity. Measurements were carried out at steady-state conditions and the available concentration range of phosphate, repeatability and accuracy, on phosphate standard solutions, were experimentally determined. Finally the sensor was used in pharmaceutical and biological matrices. The results were compared with those ones obtained by Bartlett's spectrometric method.

Chemometric study and analytical enzymatic methods for diagnosis of cholesterol gallstones

The lithogenic index (IL) provides an estimate of cholesterol saturation in gallbladder bile and is of possible value for prediction of gallstone formation. A package for pattern recognition of analytical chemical data, known as "Parvus", was used to study the different values of IL obtained experimentally using common enzymic methods for cholesterol and bile salts and other analytical techniques for phospholipids. Ten patients were investigated and some interesting conclusions were drawn, both on the equivalence of various analytical methods for the determination of phospholipids and on the contribution of pattern recognition analysis to the diagnosis of gallstones.

Determination of choline-containing phospholipids in human bile and serum by a new enzyme sensor

A simple method for direct determination both of choline and lecithin (phosphatidylcholine) in human bile and blood sera was developed. An enzyme electrode, based on immobilized choline oxidase on nylon net and an oxygen Clark electrode was assembled. Phosphatidylcholine can be determined by use of phospholipase D as hydrolyzing agent. Reliable results were obtained in the case of determination of lecithin and choline in bile samples.