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Biomedical subjects

J S Fritz

Publications and source records attributed to J S Fritz.

28 records · Page 2Linked to original sources
PubMed1997

Semi-micro solid-phase extraction of organic compounds from aqueous and biological samples.

A technique is described for performing solid-phase extractions on a semi-micro scale. Thin membrane disks 4 mm in diameter containing lightly sulfonated polystyrene or Silicalite particles are placed in the hub of a syringe needle. Aqueous samples (1-6 ml) are passed through the membrane disks and extracted compounds are subsequently eluted with 20-50 microliters of an organic solvent. Unlike solid-phase micro extraction (SPME) which uses a coated fiber, the present method is essentially a total extraction technique. Recoveries > 90% were generally obtained for a wide variety of test compounds. The same test compounds in human urine, albumin and human serum samples can be extracted without any pretreatment other than addition of a suitable surfactant. A "double-pass" technique was developed for convenient field sampling.

Acetates↗
PubMed1978

Determination of trace organic impurities in water using thermal desorption from XAD resin.

A small water sample (20 to 250 ml) is passed through a small tube containing XAD-4 resin; this effectively retains the organic impurities present in the water. This tube is connected to the permanent apparatus and the sorbed organics are thermally transferred to a small Tenex pre-column while the water vapor is vented. The pre-column is closed off, preheated to 275--280 degrees C, and then a valve is opened to plug-inject the vaporized sample into a gas chromatography. The procedure works well for a variety of model organic compounds added to the water and can be used for the analysis of actual water samples.

Adsorption↗
PubMed1977

Selective concentration of amines from aqueous solutions by a gas purging technique.

Amines are removed from heated, basic solutions saturated with salt by inert gas stripping and selectively trapped as coordination complexes on columns containing copper(II) salts coated on an inert support. An estimate of the amine concentrations at ppm levels can be made by measuring the length of the trapping column colored by the complexes. Concentrations of amines in ppb can be determined by eluting this column with potassium hydroxide and determining the amines in the effluent directly by gas chromatography. The procedure allows amines to be concentrated by a factor of 200 and removes potentially interfering substances from the sample.

Amines↗
PubMed1975

Analysis of various Iowa waters for selected pesticides: atrazine, DDE, and dieldrin-1974.

Atrazine, DDE, and dieldrin were extracted and concentrated from various surface, subsurface, and finished waters using the macroreticular resin method. Organic components in the concentrates from these waters were separated by gas chromatography; the amounts of the three pesticides in the waters ranged from 0.5 to 42,000 parts per trillion by weight. Every major watershed in the State of Iowa revealed some degree of pesticide contamination and seasonal variations were consistent with agricultural runoff models. Atrazine concentrations were highest of the three pesticides, a symptom of its widespread use in the corn belt. DDE also appeared in substantial quantities, providing further evidence of the persistence of DDT and its metabolites. Water from several shallow wells and finished water from many water treatment plants were also contaminated. Current treatment processes do not effectively remove these pesticides.

Atrazine↗