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PubMed2002

A method for determining crystalline silica in bulk samples by Fourier transform infrared spectrophotometry.

A method for determining crystalline silica (alpha-quartz) in bulk samples has been developed. This procedure requires the bulk sample to be homogenized and sieved down to particle sizes <10 micro m in diameter. The obtained fraction is analysed by Fourier transform infrared spectrophotometry. Method validation was carried out using 55 real-world bulk samples, containing between 1 and 75% (w/w) alpha-quartz. The method is capable of quantifying alpha-quartz down to 1% (w/w) in routine analysis. However, the method is unlikely to allow routine quantification at 0.1% (w/w) as currently mandated by regulations.

Particle Size↗
PubMed1999

The use of infrared spectrophotometry for measuring body water spaces.

BACKGROUND: The conventional method of measuring total body water by the deuterium isotope dilution method uses gas isotope ratio mass spectrometry (IRMS), which is both expensive and time-consuming. We investigated an alternative method, using Fourier transform infrared spectrophotometry (FTIR), which uses less expensive instrumentation and requires little sample preparation. METHOD: Total body water measurements in human subjects were made by obtaining plasma, saliva, and urine samples before and after oral dosing with 1.5 mol of deuterium oxide. The enrichments of the body fluids were determined from the FTIR spectra in the range 1800-2800 cm-1, using a novel algorithm for estimation of instrumental response, and by IRMS for comparison. RESULTS: The CV (n = 5) for repeat determinations of deuterium oxide in biological fluids and calibrator solutions (400-1000 micromol/mol) was found to be in the range 0.1-0.9%. The use of the novel algorithm instead of the integration routines supplied with the instrument gave at least a threefold increase in precision, and there was no significant difference between the results obtained with FTIR and those obtained with IRMS. CONCLUSION: This improved infrared method for measuring deuterium enrichment in plasma and saliva requires no sample preparation, is rapid, and has potential value to the clinician.

Body Water↗
PubMedDate not supplied

Determination of biphenyl residues in citrus fruit by derivative infrared spectrophotometry.

A method for determination of biphenyl residues in whole citrus fruit is described. The mascerated fruit was distilled in an acid medium, the distillate was extracted with cyclohexane, and biphenyl was determined in the extract using various measures obtained by first and second derivative infrared (IR) spectrophotometry. Calculations were performed by PE680 and SNGLE programs on data obtained using a Perkin-Elmer Model 3600 data station. The relative precision of the determinations at 70 ppm was 1.8 to 2.0%; the detection limit was 5 ppm in all measurements, and recovery of spiking concentrations of 20 to 80 ppm ranged from 90.2 +/- 5.5% (for the amplitude of the 739 cm-1 peak of the first derivative) to 97.5 +/- 2.0% (for the trough-to-peak difference from the 737 cm-1 minimum to the 743 cm-1 maximum of the second derivative.

Biphenyl Compounds↗
PubMed1992

Near-infrared spectrophotometry: a new dimension in clinical chemistry.

The near-infrared (NIR) spectral region (700-2500 nm) is a fertile source of chemical information in the form of overtone and combination bands of the fundamental infrared absorptions and low-energy electronic transitions. This region was initially perceived as being too complex for interpretation and consequently was poorly utilized. Advances in chemometric techniques that can extract massive amounts of chemical information from the highly overlapped, complex spectra have led to extensive use of NIR spectrophotometry (NIRS) in the food, agriculture, pharmaceutical, chemical, and polymer industries. The application of NIRS in clinical laboratory measurements is still in its infancy. NIRS is a simple, quick, nondestructive technique capable of providing clinically relevant analyses of biological samples with precision and accuracy comparable with the method used to derive the NIRS models. Analyses can be performed with little or no sample preparation and no reagents. The success of NIRS in any particular case is determined by the complexity of the sample matrix, relative NIR absorptivities of the constituents, and the wavelengths and regression technique chosen. We describe the general approach to data acquisition, calibration, and analysis, using serum proteins, triglycerides, and glucose as examples.

Algorithms↗
PubMed1995

Cerebral oxygenation and hemodynamics during induction of extracorporeal membrane oxygenation as investigated by near infrared spectrophotometry.

OBJECTIVE: To investigate cerebral oxygenation and hemodynamics in relation to changes in some relevant physiologic variables during induction of extracorporeal membrane oxygenation (ECMO) in newborn infants. METHODS: Twenty-four newborn infants requiring ECMO were studied from cannulation until 60 minutes after starting ECMO. Concentration changes of oxyhemoglobin (cO2Hb), deoxyhemoglobin (cHHb), total hemoglobin (ctHb), and (oxidized-reduced) cytochrome aa3 (cCyt.aa3) in cerebral tissue were measured continuously by near infrared spectrophotometry. Heart rate (HR), transcutaneous partial pressures of oxygen and carbon dioxide (tcPO2 and tcPCO2), arterial O2 saturation (saO2), and mean arterial blood pressure (MABP) were measured simultaneously. Intravascular hemoglobin concentration (cHb) was measured before and after starting ECMO. In 18 of the 24 infants, mean blood flow velocity (MBFV) and pulsatility index (PI) in the internal carotid and middle cerebral arteries were also measured before and after starting ECMO using pulsed Doppler ultrasound. RESULTS: After carotid ligation, cO2Hb decreased whereas cHHb increased. After jugular ligation, no changes in cerebral oxygenation were found. At 60 minutes after starting ECMO, the values of cO2Hb, saO2, tcPO2, and MABP were significantly higher than the precannulation values, whereas the value of cHHb was lower. There were no changes in cCyt.aa3, tcPCO2, and HR, whereas cHb decreased. The MBFV was significantly increased in the major cerebral arteries except the right middle cerebral artery, whereas PI was decreased in all measured arteries. Cerebral blood volume, calculated from changes in ctHb and cHb, was increased in 20 of 24 infants after starting ECMO. Using multivariate regression models, a positive correlation of delta ctHb (representative of changes in cerebral blood volume) with delta MABP and a negative correlation with delta tcPO2 were found. CONCLUSIONS: The alterations in cerebral oxygenation after carotid artery ligation might reflect increased O2 extraction. Despite increase of the cerebral O2 supply after starting ECMO, no changes in intracellular O2 availability were found, probably because of sufficient preservation of intracellular cerebral oxygenation in the pre-ECMO period despite prolonged hypoxemia. The increase in cerebral blood volume and cerebral MBFV may result from the following: (1) reactive hyperperfusion, (2) loss of autoregulation because of prolonged hypoxemia before ECMO and/or decreased arterial pulsatility, or (3) compensation for hemodilution related to the ECMO procedure.

Brain↗
PubMed1982

Multicomponent analysis of meat products by infrared spectrophotometry: collaborative study.

A new method for rapid multicomponent analysis of meat products based on infrared transmission was tested in a collaborative study with 4 laboratories. A series consisting of 31 samples of different meats, cooked sausage, liver sausage, and fermented sausage was distributed and analyzed at all laboratories for protein, fat, and water by the present method and by well established reference methods. There was no significant difference between the infrared method and reference methods at the 95% confidence level for determination of protein, fat, and water in meat products.

Animals↗
PubMed1988

Composition of biliary microcalculi studied with infrared spectrophotometry.

The chemical composition of biliary microcalculi obtained at 20 consecutive cholecystectomies was investigated with infrared spectroscopy. This method permits qualitative and quantitative analysis also of substances such as bilirubin which often remain in amorphous states. A PYE UNICAM spectrophotometer was used, with KBr pellet technique. A bile sample from each patient was taken for bacteriologic examination. The study confirmed previously observed high incidence of pigment microcalculi (60%). Calcium palmitate was more common (in 15% of all the studied microliths and 25% of the pigment type) than in reports in the literature concerning larger gallstones. Calcium carbonate was present in only 10%. These findings suggested pathogenetic peculiarities of microlithiasis, as did the high incidence of positive bacteriologic tests.

Aged↗
PubMed1988

Quantitative analysis of hemoglobin oxygenation state of rat brain in situ by near-infrared spectrophotometry.

The light in the near-infrared region (700-900 nm) was illuminated on the rat head, and absorption spectra were measured with the transmitted light under various conditions. The absorbance changes less than 780 nm were attributable to hemoglobin in the brain tissue, whereas those greater than 780 nm were associated with both hemoglobin and cytochrome oxidase. The changes of oxy- and total (oxy- plus deoxy-) hemoglobin content in the rat head could be monitored quantitatively by expressions of delta A700--1.20 delta A730 and delta A700--1.52 delta A730, respectively. The oxyhemoglobin content in the tissue was decreased as the O2 tension in inspired gas was lowered. At 10% O2 approximately 50% of hemoglobin was deoxygenated. The total hemoglobin content was increased under anoxic conditions. Inhalation of 5% CO2 and intravenous injection of a Ca2+ blocker nicardipine increased the O2 saturation of hemoglobin in the brain. These conclusions were confirmed by measuring the difference absorption spectra in the near-infrared region.

Animals↗
PubMed1991

REM sleep-associated hemoglobin oxygenation in the monkey forebrain studied using near-infrared spectrophotometry.

The oxygenation state of hemoglobin (Hb) in the monkey forebrain was monitored continuously throughout nocturnal sleep using a near-infrared spectrophotometric technique. During rapid eye movement (REM) sleep, an increase in oxygenated Hb occurred concomitantly with a decrease in deoxygenated Hb, while no significant changes in Hb oxygenation were observed during slow wave sleep (SWS). A gradual increase in total Hb content was also observed to occur during each REM sleep episode but not during SWS.

Animals↗
PubMedDate not supplied

[Gas-liquid chromatography with Fourier-transform infrared spectrophotometry. Application in the analysis of drugs. 2: Benzodiazepines].

High working temperatures were used during the separation of benzodiazepines by capillary gas chromatography with Fourier transform infrared detection (FTIR). Spectral identification of these drugs give very good results with 10 micrograms of drug injected. On the contrary, the precision of the quantitative determination is poor.

Benzodiazepines↗
PubMedDate not supplied

[Analysis of the composition of 2700 urinary calculi examined by infrared spectrophotometry, 1979-1989].

Two thousand seven hundred samples, received as urinary calculi, in a Turin based laboratory, in the period between March 1979 and February 1989, were examined by infrared spectroscopy to identify components even of difficult characterization: a special procedure was used and it is described. Knowing the composition of each calculus, a comparison was made between the incidence of each compound in the first 1500 samples (1979-1984) and in the remaining 1200 ones (1984-1989). Besides an increase in calcium oxalate as main component, a marked reduction in incidence of struvite was found in the calculi belonging to the second period of observation. The possible interference in calculi composition by various therapy for renal infection is discussed.

Calcium Oxalate↗
PubMed1998

Detection of formaldehyde-induced crosslinking in soft elastic gelatin capsules using near-infrared spectrophotometry.

The purpose of this research was to monitor the migration of formaldehyde from a polyethylene glycol (PEG) fill into the gelatin shell of a soft elastic gelatin capsule (SEGC) using near-infrared (NIR) spectrophotometry. SEGCs were filled with five solutions of aqueous formaldehyde in PEG (0, 0.05, 0.10, 0.20, and 0.40 v/v%), stored at ambient conditions for 48 hr, emptied, and scanned in NIR spectrophotometer. Principal component regression (PCR) was employed to analyze the spectra of the empty capsules. Good correlation was established (r2 = 0.988) when actual concentrations of formaldehyde in the PEG fill of the capsules were regressed against the principal component (PC) values from NIR spectra of the emptied and washed capsules. The loadings of the first PC describe a baseline shift in the spectra that arises from a change in water concentration. Lower PC loadings reveal the presence of signals at 1780 and 2200 nm that are not due to water absorbance, confirming the hypothesis that chemical bonds are formed during the formaldehyde-induced crosslinking of the gelatin in SEGCs. Gelatin crosslinking, initiated by formaldehyde migration from the PEG fill into the shell of an SEGC, was detected by NIR spectrophotometry. When NIR was coupled to principal component analysis, a linear relationship was found between the NIR spectra of empty SEGCs and the amount of crosslinking induced by concentrations of formaldehyde in the original fill material.

Capsules↗