Increase of acetone emitted by urine in relation to ovulation.

Background: Selected ion flow tube mass spectrometry allows trace gas quantification in exhaled breath and in the air/vapor above liquids (headspace) down to the 10 parts-per-billion level. During selected ion flow tube mass spectrometry investigation of the volatile compounds emitted by urine, high acetone levels were incidentally identified in the headspace of urine from healthy female volunteers around their mid-cycle. Hence, this study was designed to measure urine headspace acetone levels throughout the menstrual cycle.

Influence of convection on the diffusive transport and sieving of water and small solutes across the peritoneal membrane.

The three-pore model of peritoneal membrane physiology predicts sieving of small solutes as a result of the presence of a water-exclusive pathway. The purpose of this study was to measure the diffusive and convective components of small solute transport, including water, under differing convection. Triplicate studies were performed in eight stable individuals using 2-L exchanges of bicarbonate buffered 1.

Measuring transport of water across the peritoneal membrane.

Introduction: Mechanisms of water flow across the peritoneal membrane include diffusion, convection, and reabsorption.

Objectives: To understand these processes more clearly we have developed a method to measure transport of water across the peritoneal membrane.

Methods: An artificial gradient of deuterated water (HDO) between blood and dialysate compartments was created in five subjects who took 0.

Increase of acetone and ammonia in urine headspace and breath during ovulation quantified using selected ion flow tube mass spectrometry.

Selected ion flow tube mass spectrometry (SIFT-MS) has been used for a detailed study of the daily variations in the acetone and ammonia content of the headspace above urine from a healthy female subject over the course of three separate menstrual cycles. Midstream urine samples were taken every morning prior to any food intake and the headspace subsequently analysed for a number of metabolites. Concurrent with the time of ovulation, a 3-to- 12-fold increase in the level of acetone in the urine headspace was observed.

Time variation of ammonia, acetone, isoprene and ethanol in breath: a quantitative SIFT-MS study over 30 days.

A study of the concentrations of the common breath metabolites ammonia, acetone, isoprene, ethanol and acetaldehyde in the breath of five subjects over a period of 30 days has been carried out. Breath samples were taken and analysed in the early morning on arrival at the laboratory. The real time analyses of three consecutive breath exhalations were carried out using selected ion flow tube mass spectrometry (SIFT-MS) on line to the instrument.

Comparative measurements of total body water in healthy volunteers by online breath deuterium measurement and other near-subject methods.

Background: We developed a new near-subject approach, using flowing afterglow-mass spectrometry (FA-MS) and deuterium dilution, which enables the immediate measurement of total body water (TBW) from single exhalations.

Objectives: The objectives were to show the efficacy of the new FA-MS method in measuring TBW in healthy subjects and to compare these measurements with values derived from multifrequency bioelectrical impedance analysis, skinfold-thickness (SFT) measurements, and both recent and historical published regression equations.

Design: After baseline measurement of breath deuterium abundance, 24 healthy subjects ingested 0.

Quantification of volatile compounds in the headspace of aqueous liquids using selected ion flow tube mass spectrometry.

We describe a method by which the concentrations of volatile compounds in the headspace of their dilute aqueous solutions in sealed containers can be determined using on-line selected ion flow tube mass spectrometry (SIFT-MS). Thus, the changing number density of the molecules of the volatile compound in the carrier gas of the SIFT-MS instrument is described in terms of its changing flow rate as the pressure in the sealed container decreases during the sampling procedure. It is shown that the best analytical procedure is to determine the mean concentration of the trace gas in the liquid headspace over a given sampling time and relate this to the required concentration, which is the initial equilibrium concentration established before the pressure in the sealed container reduces significantly.