Determination of 2-ethylhexyl 4-(dimethylamino) benzoate using membrane-assisted liquid-liquid extraction and gas chromatography-mass spectrometric detection.

A flow-cell for micro-porous membrane liquid-liquid extraction with a sheet membrane was used to extract 2-ethylhexyl 4-(dimethylamino) benzoate (EDB) from urine of solar-cream users and spiked wine samples. The cell enabled the target analyte to be extracted from 7.9 mL of donor solution into 200 microL of acceptor solution (decane). After extraction, the acceptor solution was transferred to a micro-vial for GC-MS analysis without derivation. In this work, variables affecting the enrichment factor were also studied, such as organic solvent, extraction time, recirculation flow of the donor solution through the donor chamber, presence of potassium chloride and ethanol in the donor solution and pH. The method has been evaluated in terms of linearity, sensitivity, precision, limits of detection and quantification and extraction efficiency. Limits of quantification were 1 and 3 microg L(-1) EDB for urine and wine, respectively. Quantitative analysis has been carried out by applying the method of standard additions. Within- and between-day relative standard deviations were lower than 12% and 20%, respectively. EDB was found in the urine of users of cream containing EDB in the concentration interval 1.2-7.2 microg L(-1). Therefore, this provides evidence of EDB dermal absorption and subsequent excretion through the urinary tract. EDB was not found in the analysed wine samples.

SEM-FTIR spectroscopic evaluation of deterioration in an historic coffered ceiling.

Microorganisms generally degrade wood when moisture, oxygen and other environmental factors provide favorable growing conditions. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to study the development and transformation of the products formed during the biomineralization process that follows the deterioration of wood from an historical coffered ceiling (Cloister of St Francesc (XIV century), Palma de Mallorca, Spain). After fungi colonization, cellulose and lignin disappear and inorganic salts are formed. Thus, the secretion of numerous acids (initially oxalic acid) by fungal hyphae also leads to the precipitation of authigenic salts. Damaged cells or tissues enhance the formation and growth of crystals, which is strongly favored by fungi that function as calcification nuclei. Finally, the presence of dihydrated calcium sulfate reveals the contribution of environmental factors to the weathering of wood.

Earth pigments in painting: characterisation and differentiation by means of FTIR spectroscopy and SEM-EDS microanalysis.

Analytical characterisation of natural earths (ochres, siennas, umbers and green earths) has been carried out using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) coupled to an energy dispersive X-Ray spectrometer (EDS). The study of these pigments, which are found in works of art, is very important since it can shed light on their source or the pictorial technique used. FTIR spectroscopy is suitable for the identification and differentiation of ochres and siennas. According to the matrix of the sample, FTIR allows the classification of ochres into ochres containing kaolinite and ochres containing sulphate. One of the goals of this research has been to establish a relationship between the matrix and the source of the samples tested. SEM-EDS is probably a better technique than FTIR for characterising umbers and green earths since they do not exhibit significant differences when FTIR studies are performed.

Vitamin A and urolithiasis.

The effects of vitamin A deficiency on urolithiasis were investigated in male rats. A vitamin A-deficient diet caused important changes in the composition of the urine of the treated rats when compared with controls. One of the main effects was a decrease in the concentration of urinary glycosaminoglycans and zinc in the rats receiving the vitamin A-deficient diet. Significant differences were also found in plasma vitamin E and in the relation of vit E/vit A between treated and control groups but, in general, with no important differences in vitamin A. Nevertheless, significant differences in kidney content of vitamin A were observed between both groups. On the other hand, lesions of the cuboidal epithelium that covers the papillae in rats treated with the vitamin A-deficient diet were severe when compared with controls. The vitamin A and E plasma levels in urolithiasic humans were also investigated and compared with those found in a control group. No significant differences were observed in plasma vitamin A levels; nevertheless a significant increase in vitamin E and in the vit E/vit A ratio was clearly observed. These results could be related to a possible deficit of vitamin A in kidneys of stone formers, this being one of the diverse factors that can contribute to urolith development. Moreover, the deficit of important urinary crystallization inhibitors normally found in stone-formers, such as pyrophosphate and phytate, can also be related to the presence of low levels of renal vitamin A which prevents the enzymatic degradation of such inhibitors.

Epidemiology of urinary stone disease in the Balearic Islands Community.

In a survey conducted on 1500 individuals, an overall prevalence of 14.3% for the year 1990 was found for urinary stone disease in the Balearic Islands. The prevalence showed higher figures for people living in rural areas than for those living in cities, and this could be correlated with traditional living habits such as traditional Balearic diet. Finally, a surprising fact is that only 54% had consulted a urologist as outpatients and the rare occasion at which the calculi were analyzed (15.1%).

Crystallization of organic crystals with "tailor-made" inhibitors. Determination of L-lysine using L-glutamic acid as substrate.

A very simple turbidimetric procedure is used for determination of L-lysine, based on its inhibitory action on the crystallization of L-glutamic acid. The obtention of supersaturated solutions of L-glutamic acid was accomplished by means of the change in the solvent composition. Thus, the addition of ethanol to stable aqueous solutions of this amino acid allows the obtainment of unstable supersaturated solutions. The method suffers from very few interferences and permits the development of an analytical procedure to determine L-lysine in the presence of D-lysine. The method was also applied to the determination of L-lysine in pharmaceutical products.

Inhibitors of calcium oxalate crystallization and urolithiasis.

In urolithogenic processes both, promoters and deficit of inhibitors, play an important role. The inhibitory action of added inhibitors (magnesium, citrate, pyrophosphate and chondroitin sulphate) was investigated using the urine of 72 patients with calcium urolithiasis. It was concluded that the deficit of inhibitors seems to be an important cause of stone formation in idiopathic oxalocalcic urolithiasis. Nevertheless, when that specific heterogeneous nucleation takes place it becomes an important factor and the inhibitor plays a complementary role in calcium oxalate urolithiasis.

A potentiometric technique for kinetic determination of citrate, based on inhibition of crystalline growth of lead carbonate seed crystals.

The growth of lead carbonate seed crystals is strongly inhibited by the presence of citric acid. The kinetics of crystal growth were followed potentiometrically with a lead ion-selective electrode. The study of different variables on such a process was carried out with the aim of developing kinetic procedures to determine citrate (0.5-2.0 mug/ml). The selectivity and sensitivity of these processes allow the application of his crystallization reaction to direct determination of citrate in drinks and in a pharmaceutical product.

The role of hyperoxaluria in the formation of calcium oxalate urinary calculi, and its association with other biochemical measurements.

The part played by hyperoxaluria in the formation of calcium oxalate urinary calculi was studied in 153 patients who had each been diagnosed as having calcium oxalate urinary calculi on one or more occasions. Seventy-seven of the patients excreted normal amounts of calcium (less than 6.2 mmol/d), and 76 had hypercalciuria (excretion greater than or equal to 6.2 mmol/d); each group was divided into a further two groups depending on whether the oxalate concentration was above or below 0.16 mmol/l. Pure calcium oxalate stones were more common in patients whose calcium excretion was normal, and mixed calcium oxalate and phosphate stones were more common among hypercalciuric patients. Urinary concentrations/day of magnesium, citrate, and phosphorus were significantly lower in the two groups in which the oxalate concentrations were below 0.16 mmol/l than in a normal control group, and magnesium and phosphorus were significantly lower in the two groups in which oxalate concentrations were less than 0.16 mmol/l than in the two in which they were above that value. The concentration of citrate was also lower, but not significantly so. In addition, the pH of the urine in patients with mixed stones was significantly higher in all groups than when the stones were composed of pure calcium oxalate.

Relation between calcium oxalate hydrate form found in renal calculi and some urinary parameters.

In calcium oxalate urolithiasis, the monohydrate and dihydrate forms can be found. The aim of this paper is to examine a group of patients with calcium oxalate calculi to determine the calcium oxalate form and the possible relationship with calcium and other urinary biochemical parameters. It was found that calcium oxalate monohydrate is more frequent in the normocalciuric group and also is associated with a lack of inhibitory capacity, while a mixed calculus of calcium oxalate and phosphate or calcium oxalate dihydrate can be related with hypercalciuria.

Inhibitory effect of pyrophosphate, citrate, magnesium and chondroitin sulphate in calcium oxalate urolithiasis.

The inhibitory capacity of pyrophosphate, citrate, magnesium and chondroitin sulphate was investigated, using the urine of 21 calcium oxalate stone-forming patients without metabolic alterations. The inhibitory effect of these substances was assessed by a combination of nephelometry (light scattering) and optical microscopy. The results showed that citrate and magnesium had an inhibitory effect in a significant number of cases. Pyrophosphate and chondroitin sulphate had a less marked effect. The main urinary lithogenic biochemical parameters of the patients were also studied to see if there was a relationship between them and the inhibitory capacity of the compounds.

The relation between orthophosphate and pyrophosphate in normal subjects and in patients with urolithiasis.

In calcium lithiasis, inhibitors have a significant effect in reducing the crystallization process. This work evaluated orthophosphate in a group of patients with calcium oxalate lithiasis, and in a control group. The study of orthophosphate and pyrophosphate, showed differences between stone formers and the control group. These results could be attributed to a failure in the renal transformation of orthophosphate into pyrophosphate.

Uric acid and its relationship with glycosaminoglycans in normal and stone-former subjects.

Uric acid is implicated in calcium oxalate kidney stone formation. Conspicuously so far, two hypotheses have been proposed: direct induction of calcium oxalate precipitation by uric acid, and uric acid as anti-inhibitor by binding urinary glycosaminoglycans (GAGS). The aim of this work is to evaluate uric acid and the relationship with GAGS in a group of patients with calcium oxalate lithiasis, and in a control group for detecting possible differences between the two groups. It was found that the lower concentration of GAGS in stone formers could impede their inhibitory activity on the heterogeneous nucleation of uric acid in calcium stone formation.

Investigation of GAGS on 24-hour and 2-hour urines from calcium oxalate stone formers and healthy subjects.

The role of urinary glycosaminoglycans (GAGS) in calcium oxalate lithiasis is of great interest in urologic research. It has been claimed that GAGS are important inhibitors of calcium oxalate crystal growth and aggregation. The aim of this paper is to evaluate GAGS excretion and concentration in two groups of patients, calcium stone formers (with or without metabolic alteration) and a control group, to detect possible differences. The findings of this study show that significant differences exist not only in the 24-hour average excretion between stone formers without alteration and healthy subjects but also in the mean concentration values between the stone former and control groups. The same results are obtained from the 2-hour urine analysis. It is concluded that 2-h urine analyses of GAGS have the same or more practical value than a 24-h urine analysis and that the results must be expressed in terms of concentration.

Variations in the activity of urinary inhibitors in calcium oxalate urolithiasis.

Opinions vary on the effects produced by urinary inhibitors of crystallisation. We describe a simple method for studying inhibitory effects in urine based on nephelometry and optical microscopy. It was concluded that the inhibitory effect of a given substance on calcium oxalate crystallisation depends on the particular sample of urine being examined and that the most effective inhibitor can be determined only by studying the urine of each patient individually.

Spectrofluorimetric determination of desoxycholic acid in the presence of cholic and chenodesoxycholic acids by use of Ce(IV) and concentrated sulphuric acid.

A method for the quantitative estimation of desoxycholic acid (200-700 micrograms/ml) in the presence of cholic and chenodesoxycholic acids is described. The method is based on the transformation of desoxycholic acid in fluorescent products (lambda ex = 350 nm, lambda em = 458 nm) by the action of concentrated sulphuric acid, this being enhanced by the presence of Ce(IV). The sample is mixed with a solution of Ce(IV) and concentrated sulphuric acid under standard conditions. Fluorescence is measured in relation to a reference containing the same components except Ce(IV). Cholic and chenodesoxycholic acids do not produce a reaction under adequate conditions. Synthetic samples of bile acids were tested for validation of the method.