Simultaneous gas-chromatographic analysis of lower fatty acids, phenols and indoles in faeces and saliva using a fused silica glass capillary column

Simultaneous Determination of Phenol and Mononitrophenol Isomers Using PLS Regression and Conventional and Derivative Spectrophotometry

The partial least squares regression method (PLS) was tested as a calibration procedure for the simultaneous determination of phenol, o-nitrophenol, m-nitrophenol and p-nitrophenol by both conventional and first derivative UV/Vis spectrophotometry. The experiments were conducted in the acidic, neutral and basic media. The results obtained by the application of the PLS procedure on the conventional and first derivative spectra in two solvent media were compared. It was found that the results obtained in the basic medium have better performance characteristics than those obtained in the acidic or neutral media. Comparable results were obtained in the case of both conventional and first derivative absorbance data. The proposed method was applied to the determination of the four phenol derivatives in natural spiked water samples at concentration levels between 1.0 and 10.0 microg ml(-1) with average recoveries in the range 96% - 99%.

Occupational Exposure to Aromatic Hydrocarbons at a Coke Plant: Part I. Identification of Hydrocarbons in Air and their Metabolites in Urine by a Gas Chromatography‐Mass Spectrometry Method

A method for the qualitative analysis of aromatic hydrocarbons in air and their various urinary metabolites is presented. The air was sampled in charcoal tubes and extracted with carbon disulfide. The hydrocarbons were identified as being aliphatic hydrocarbons (C(9)-C(19)), aromatic hydrocarbons and heterocyclic compounds. The urinary metabolites after enzymatic hydrolysis were analyzed by solid-phase extraction with a styrene-divinylbenzene resin, silylation with N,O-bis(trimethylsilyl)acetamide and GC/MS for separation and detection. Satisfactory separation of all compounds investigated was achieved without interference due to matrix peaks. The following compounds were identified in the urine of workers: dimethylphenol isomers, 4-ethyl-1,3-benzenediol, 2-ethoxybenzoic acid and methoxyphenols. Trimethylsilyl derivatives of aromatic hydroxyacids and hydroxymethoxyacids were found in the urine of occupationally exposed workers by means of a silylation procedure.

Simultaneous determination of phenol, cresol, xylenol isomers and naphthols in urine by capillary gas chromatography

An attempt was made to establish a method for the simultaneous determination of urinary concentrations of phenol, o-, p- and m-cresols, 1- and 2-naphthol and xylenol isomers by capillary gas chromatography. Urine samples were extracted after acid hydrolysis of glucuronides and sulfates by solid-phase extraction. The ten substances were separated gas chromatographically using a capillary column (Ultra 2) of cross-linked 5% phenylmethyl silicone. Calibration graphs were linear for 5-100 micrograms/ml of all the phenols determined. The corresponding detection limits for phenolic compounds varied from 0.1 to 0.2 microgram/ml. The relative standard deviations for samples in urine were in the range 2.6 - 16.6% and the accuracy was in the range 1.4-25%. Recoveries were generally over 80%.

A newly designed deodorant pad for urinary incontinence

The authors designed a new pad for urinary incontinence. It is composed of a cloth of acrylonitrile copper sulfide and another cloth of iron-phthalocyanine. In vitro experiments showed that acrylonitrile copper sulfide cloth inhibited the growth of most bacteria causing urinary tract infection, and that iron-phthalocyanine cloth effectively eliminated bad-smelling gases. The use of this pad relieved diaper-dermatitis and diminished offensive smells from feces and urine. This pad was well received by nurses and helpers taking care of incontinent elderly people.

Occurrence, absorption and metabolism of short chain fatty acids in the digestive tract of mammals

Short chain fatty acids (SCFA) also named volatile fatty acids, mainly acetate, propionate and butyrate, are the major end-products of the microbial digestion of carbohydrates in the alimentary canal. The highest concentrations are observed in the forestomach of the ruminants and in the large intestine (caecum and colon) of all the mammals. Butyrate and caproate released by action of gastric lipase on bovine milk triacylglycerols ingested by preruminants or infants are of nutritional importance too. Both squamous stratified mucosa of rumen and columnar simple epithelium of intestine absorb readily SCFA. The mechanisms of SCFA absorption are incompletely known. Passive diffusion of the unionized form across the cell membrane is currently admitted. In the lumen, the necessary protonation of SCFA anions could come first from the hydration of CO2. The ubiquitous cell membrane process of Na+-H+ exchange can also supply luminal protons. Evidence for an acid microclimate (pH = 5.8-6.8) suitable for SCFA-protonation on the surface of the intestinal lining has been provided recently. This microclimate would be generated by an epithelial secretion of H+ ions and would be protected by the mucus coating from the variable pH of luminal contents. Part of the absorbed SCFA does not reach plasma because it is metabolized in the gastrointestinal wall. Acetate incorporation in mucosal higher lipids is well-known. However, the preponderant metabolic pathway for all the SCFA is catabolism to CO2 except in the rumen wall where about 80% of butyrate is converted to ketone bodies which afterwards flow into bloodstream. Thus, SCFA are an important energy source for the gut mucosa itself.

Gas chromatographic-mass spectrometric analysis of volatile constituents in saliva

Present methods for the development of metabolic profiles are limited to the use of headspace techniques and solvent extraction methods. A new method for the development of saliva profiles which provides information complementary to existing analyses has been developed. The results of the developed methodology provide a reliable, reproducible method for metabolic profiling. Gas chromatographic-mass spectrometric analysis of the volatile constituents provided positive identification of 39 compounds. Application of the developed protocol toward the investigation of saliva as a vehicle for the non-invasive detection of certain pathological states, specifically diabetes mellitus and liver disorders, may be possible.