Simple and precise method for liquid chromatographic determination of chloramphenicol in serum using a phase separation extraction.

A high-performance liquid chromatographic method for the determination of chloramphenicol using an alkaline salt-induced phase separation extraction is described. The extraction procedure is as simple as miscible organic solvent deproteinization methods, yet produces extracts that have negligible protein and minimal interference from acidic compounds. The use of 2,4-dinitroacetanilide as an internal standard and of microprocessor-stored standard relative response factors results in a more precise assay without need for daily routine standardization. Serum is mixed with an equal volume of acetonitrile containing the internal standard, and then solid sodium chloride containing 20% of sodium phosphate by weight is added and mixed. The resulting upper phase is chromatographed on a C-18 reversed-phase column and monitored at 278 nm. Between-day precision is excellent. Comparison with an alternate method and with drug-monitoring proficiency samples showed the method to have excellent accuracy. The possible use of this phase separation extraction in other assays in which miscible solvent extraction is used is discussed.

A total and direct bilirubin determination using an SDS procedure on the Abbott Bichromatic Analyser.

A procedure to measure total and direct bilirubin using the Abbott Bichromatic Analyser is described. The method is an adaptation of a sodium dodecyl sulfate method. Reaction products are measured at an acid pH in a buffered matrix using a 600-650 filter wheel. The method has very little spectral interference from either hemolysis or lipemia and correlates well with the manual Jendrassik-Grof method.

New diagnostic use of bone marrow acid and alkaline phosphatase.

Prostatic acid phosphatase and alkaline phosphatase values in bone marrow were correlated with skeletal surveys and diagnoses during a six-month study. In cases of biopsy-proven adenocarcinoma of the prostate, bone marrow prostatic acid phosphatase was the most consistently abnormal value. Diagnoses other than prostatic cancer involving the bone marrow, e.g., myeloma and leukemias, were associated with elevated prostatic acid phosphatase and alkaline phosphatase values. In cases in which the bone marrow was not involved by metastasis, these values were normal. Bone marrow prostatic acid phosphatase assay was found to be a very good tool for detecting early osseous metastases from any site, including prostatic adenocarcinoma.

Stability and precision of a new ampuled quality-control system for pH and blood-gas measurements.

We describe an evaluation of the in-use stability and short-term precision of a three-level ampuled quality-control system for monitoring pH, pCO2, and pO2 measurements on clinical blood-gas analyzers. In three hospital laboratories, 324 such ampuls were opened and allowed to stand with their contents exposed to atmospheric conditions for accurately timed intervals up to 240 s. Contents were then analyzed for pH, pCO2, and pO2. Student's t-test was used to evaluate the significance of differences observed in recoveries after time exposure. At a signifcance level of P less than or equal to 0.05, the only significant changes observed throughout the first minute of exposure were average pO2 increases of 180 Pa (1.4 mmHg) (+ 1.4%) and 230 Pa (1.7 mmHg) (+ 2.9%) at levels of 13.4 and 7.7 kPa kPa (101 and 58 mmHg), respectively. The ampuled system was found to be stable precise convenient, and suitable for use in the routine laboratory.