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Context.—Closed sample tubes are needed for stored as well as in-process samples because evaporation significantly changes analyte concentrations. In modern laboratories, it is essential that the procedures for ordering tests on stored serum samples be simple and time-efficient. Therefore, recapping and reopening of tubes should be readily possible in laboratories to save resources and time. Objective.—To evaluate the recapping system MagCap, in comparison to established snap caps and unsealed tubes. Design.—Specific balls, with an iron core, fit tightly by their specific weight into openings of primary and secondary tubes as well as microtiter plates. Recapping of the tubes can be performed individually by a single dispenser or rackwise by a multidispenser. Balls can be removed individually by a pencillike magnet or rackwise. Balls can be reused after cleaning in a glassware washer or used as disposables. Results.—Balls seal the sample tubes as effectively as snap caps and decrease evaporation significantly in comparison to unsealed tubes. Evaporation effects of up to 13% were detected in unsealed tubes (0.5 mL) within 24 hours, whereas resealing of the tubes diminished the concentration effect to less than 1%. Open samples (0.5 mL) showed a concentration effect in the refrigerator within 7 days of up to 25%. The evaporation effect of the sealed tubes was less than 3%. Multiple reopenening and recapping procedures are easily possible using magnetic forces. Conclusions.—The MagCap recapping system seals primary and secondary containers securely and cost-effectively with the ball cap and thus facilitates a necessary advance in sample quality.

The antitumor activity of alkyl lysophospholipids has raised some questions concerning the degradation of O-alkyl bonds in naturally occurring ether lipids. In this report, we describe the first continuous assay for O-alkylglycerol monooxygenase (AGMO), the only enzyme known to cleave the O-alkyl bond in saturated ether lipids and ether phospholipids. AGMO activity was monitored at 340 nm by coupling the NADH redox reaction to the tetrahydropteridine cofactor of the rat liver microsomal enzyme. Turnover rates as low as 0.6 nmol/min could be measured. Using radiolabeled substrates, the products were identified with a TLC-Linear-Analyzer. The only interference with this assay can arise from other reducing agents, e.g. dithiothreitol. The assay was used to develop protocols for the solubilization of AGMO from membrane preparations in the presence of detergents.