Homogeneous sample preparation of raw shrimp using dry ice.

Sample homogeneity is critical to accurate and reproducible analysis of trace residues in foods. A method of uniform sample preparation using dry ice is described for shrimp. Other sample preparation techniques for raw shrimp produce nonhomogeneous samples. Sample homogeneity was determined through analysis of chloramphenicol added to intact tiger or white shrimp prior to sample preparation. Simulated chloramphenicol residue levels were 50, 15, 10, and 5 ppb. No significant differences were noted when analyses of shrimp inoculated with chlor-amphenicol prior to sample preparation with dry ice were compared with analyses of shrimp spiked after grinding with dry ice. Grinding shrimp with dry ice produced samples with homogeneous chloramphenicol residues. This technique should be applicable to other tissues and vegetable products.

Liquid chromatographic determination and identification tests for dexamethasone in bulk drugs and elixirs: collaborative study.

A normal phase liquid chromatographic method for the determination of dexamethasone in bulk drugs and elixirs was collaboratively studied by 6 laboratories. The method uses a silica column, water-modified acetic acid-methanol-methylene chloride mobile phase, cortisone internal standard, and photometric detection at 254 nm. Collaborators were supplied blind duplicate samples of 3 bulk drugs, 2 commercial elixirs, and 1 authentic elixir. Dexamethasone elixir dosage level is 0.5 mg/5 mL. Mean recovery of dexamethasone from the authentic elixir formulated to contain 0.471 mg/5 mL was 94.5%. (Authentic elixirs were found to stabilize about 6% below the theoretical concentration.) Mean recovery for the bulk drugs was between 97.1 and 100.1%. Mean coefficients of variation for bulk drug and elixir samples were less than 0.8% and 3.6%, respectively. Identification tests for dexamethasone by thin-layer chromatography, infrared spectroscopy, and relative LC retention times, as well as the gas chromatographic determination of alcohol in the elixirs were also collaboratively studied. Mean recovery of alcohol from the synthetic elixir was 98.6%. The mean coefficient of variation for alcohol for all samples analyzed was less than 1.4%. The LC method for dexamethasone in drug substance and elixirs, the identification tests, and the GC method for alcohol in dexamethasone elixirs have been adopted official first action.

Spectrophotometric determination of aminacrine hydrochloride in creams, jellies, and suppositories: interlaboratory study.

A previously reported visible spectrophotometric method for the analysis of aminacrine hydrochloride in creams, jellies, and suppositories was studied collaboratively by 8 laboratories. Aminacrine hydrochloride was extracted into acidic ethanol and its visible spectrum recorded. The amount present was calculated by determining the net absorbance between the absorbance maximum at about 402 nm and one-half the sum of the absorbance of the minima at about 389 and 412 nm. Each collaborator received 4 creams (0.2%), 1 jel (0.2%), 1 molded suppository (6 mg/3.198 g), and 2 gelatin-encapsulated suppository samples (12 mg/6.661 g and 14 mg/6.863 g). The cream samples included blind duplicates prepared to contain 0.212% aminacrine hydrochloride, 15% sulfanilamide, and 2% allantoin. Mean recovery for the authentic cream was 104.7% with a coefficient of variation (CV) of 9.22%. The commercial products contained these respective amounts (CVs): creams, 100.0% (2.48%) and 101.5% (2.16%); jel, 118.0% (9.58%); molded suppository, 102.7% (1.88%); and gelatin encapsulated suppositories, 93.1% (1.0%) and 94.3% (1.60%). Standard aminacrine hydrochloride provided for the study was 99.6% pure by nonaqueous titration. Thin layer chromatographic identification of aminacrine hydrochloride was also tested collaboratively. The method was not adopted by AOAC.

Evaluation of fluorometric determination-thin layer chromatographic identification of aminacrine hydrochloride in drug preparations.

Utilizing the fluorescent property of aminacrine hydrochloride and a filter fluorometer, a fluorometric method for aminacrine hydrochloride in drug combinations was developed, collaboratively studied, and adopted as official first action in the 11th edition of Official Methods of Analysis. Identity was confirmed by thin layer chromatography (TLC). Additional analytical work was undertaken with a grating fluorometer to support a change in the method status to official final action. The grating instrument recorded the aminacrine hydrochloride spectrum as opposed to the total fluorescence emission measured by the filter instrument. The spectrum of aminacrine hydrochloride showed that the molecule was exhibiting self-absorption of the emitted radiation even at concentrations of 10(-6)M and that the ratio of the 2 peaks in the emission spectrum varied with concentration. Additional analyses of an authentic cream preparation that also contained sulfanilamide gave an average recovery of 86.0% for aminacrine hydrochloride in 10 replicate portions. Because of these observations, the current Associate Referee's recommendation to delete the fluorometric procedure from the 13th edition of Official Methods of Analysis was adopted. A recommended deletion of the TLC identification test was also adopted.

Spectrophotometric determination of aminacrine hydrochloride in creams, jellies, and suppositories.

A visible spectrophotometric method has been developed for the quantitation of aminacrine hydrochloride in creams, jellies, and suppositories. Aminacrine hydrochloride was extracted into acidic ethanol and its visible spectrum was recorded. The amount present was calculated by determining the net absorbance between the absorbance maximum at about 402 nm and one-half the sum of the absorbances of the minima at about 389 and 412 nm. Aminacrine and a trace contaminant, 9(10H)-acridone, were independently identified by different thin layer chromatographic systems.

Semiautomated method for analysis of enteric-coated and plain coated diethylstilbestrol tablets.

A semiautomated fluorometric method for the analysis of enteric-coated and plain coated diethylstilbestrol tablets is presented. To eliminate interferences from tablet excipients, diethylstilbestrol is extracted into an organic solvent and then into a basic aqueous solution. After UV irradiation, a product of diethylstilbestsrol is formed from which a fluorophore is produced chemically. The fluorescence is measured at an excitation wavelength of 335 nm and an emission wavelength of 410 nm. The coefficient of variation measured for the semiautomated procedure was 0.59%. Assay results agreed well with the USP procedure for tablets containing greater than 1 mg of diethylstilbestrol. Tablet dyes and excipients interfered in the USP procedure, which yielded low results for tablets containing less than 1 mg of diethylstilbestrol. Standard recovery data and assays of tablet composites showed that dyes and other excipients do not interfere with semiautomated procedure.