Biomedical subjects

P D Whitter

Publications and source records attributed to P D Whitter.

4 recordsLinked to original sources

PubMed1985

Evaluation and comparison of a radiative energy attenuation method for determining cholesterol in serum.

Determination of cholesterol by a radiative energy attenuation (REA) technique was evaluated and compared with results obtained by the Boehringer Mannheim High Performance Cholesterol Assay and the Du Pont aca. Within-assay and between-assay CVs for the REA method, for two sets of controls, were both less than 5%. We observed no interference with lipemic samples. Analytical recovery averaged 102.8%. We used all three methods for parallel determinations of 217 patients' samples containing a wide range of cholesterol concentrations. Linear regression analysis of the REA results vs those of the comparison methods were as follows: REA = 1.03 Boehringer - 0.072 (r = 0.993) and REA = 1.02 aca - 0.048 (r = 0.995). We also discuss bilirubin interference with the REA method for cholesterol.

Adolescent↗

PubMed1984

Abbott radiative energy attenuation method for quantifying ethanol evaluated and compared with gas-liquid chromatography and the Du Pont aca.

Quantification of ethanol by a radiative energy attenuation (REA) technique was evaluated and compared with results by gas-liquid chromatography (GLC) and by the Du Pont aca. Within-assay CVs were less than 5.5%. Between-assay CVs ranged from 1.9% to 6.0% for serum and blood controls at concentrations of 0.5, 1.0, and 2.5 g/L. We observed no cross reactivity with methanol, isopropanol, or acetone, and analytical recovery of ethanol from serum averaged 101%. For the three-method comparison we performed parallel determinations of 156 blood, 92 serum, and 54 urine samples containing a wide range of ethanol concentrations. Linear regression analysis of the REA results vs those of GLC or aca yielded the following: for serum, REA = 1.03 GLC -0.03 (r = 0.998), REA = 1.13 aca -0.04 (r = 0.999); for blood, REA = 0.97 GLC + 0.05 (r = 0.994), REA = 0.99 aca + 0.06 (r = 0.996); and for urine, REA = 1.01 GLC -0.03 (r = 0.998). We also discuss the clinical and forensic use of the REA method for ethanol.

Alcohol Dehydrogenase↗

PubMedDate not supplied

A rapid method for the identification of acidic, neutral, and basic drugs in postmortem liver specimens by Toxi-Lab.

A rapid, qualitative method for the identification of drugs and drug metabolites in postmortem liver specimens has been developed using the Toxi-Lab drug screening system. A single-step liquid-liquid extraction, using heptane/dichloromethane, was employed for acidic/neutral drugs. Basic/neutral drugs were extracted with 1-chlorobutane and subjected to back-extraction and lipid clean-up. Chromatographic separation and drug identification required no further modifications of the Toxi-Lab procedure. The method, including tissue preparation, requires approximately 2 hr, is compatible with GLC analysis, and utilizes minimal sample size. The assay allows detection of 5 to 20 micrograms of drug/g of tissue. The use of this assay in forensic analyses is discussed.

Chromatography, Gas↗

PubMedDate not supplied

Automated extraction for the analysis of 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid (THCCOOH) in urine using a six-head probe Hamilton Microlab 2200 system and gas chromatography-mass spectrometry.

An automated extraction scheme for the analysis of 11 -nor-delta9-tetrahydrocannabinol-9-carboxylic acid using the Hamilton Microlab 2200, which was modified for gravity-flow solid-phase extraction, has been evaluated. The Hamilton was fitted with a six-head probe, a modular valve positioner, and a peristaltic pump. The automated method significantly increased sample throughput, improved assay consistency, and reduced the time spent performing the extraction. Extraction recovery for the automated method was > 90%. The limit of detection, limit of quantitation, and upper limit of linearity were equivalent to the manual method: 1.5, 3.0, and 300 ng/mL, respectively. Precision at the 15-ng/mL cut-off was as follows: mean = 14.4, standard deviation = 0.5, coefficient of variation = 3.5%. Comparison of 38 patient samples, extracted by the manual and automated extraction methods, demonstrated the following correlation statistics: r = .991, slope 1.029, and y-intercept -2.895. Carryover was < 0.3% at 1000 ng/mL. Aliquoting/extraction time for the automated method (48 urine samples) was 50 min, and the manual procedure required approximately 2.5 h. The automated aliquoting/extraction method on the Hamilton Microlab 2200 and its use in forensic applications are reviewed.

Automation↗