Analytical grade hexane

Analytical grade hexane, acetone, dichloromethane, petroleum ether, and acetonitrile were purchased from Merck (Germany). They were distilled over a 0.5-m packed column (reflux ratio approximately 1:25).10 Solvent purity was tested by gas chromatographic analyses. Anhydrous granulated sodium sulfate and silica gel 100–200 mesh (Merck, Germany) were cleaned with pure n-hexane by distillation. The external and internal standard were purchased from Restek (USA) and constituted of 1000 μg/ml of the following PCB congeners: #8, #18, #28, #44, #52, #60, #77, #81, #101, #105, #114, #118, #123, #126, #128, #138, #153, #156, #157, #167, #169, #170, #180, #185, #189, #195, and #206.

The Aloe vera freeze-dried gel powder used to prepare the intramammary formulations was purchased from America Inc. (District Court, Scottsdale, AZ, USA). The cloxacillin and ceftiofur standards were of 99% purity and sourced from Dr. Ehrenstorfer^® (Augsburg, Germany). As for aloin A and aloin B standards, these were of 87 and 92.9% purity, respectively and were manufactured by ChromaDex Inc. (Irvine, CA, USA).
Other reagents, such as high performance liquid chromatography (HPLC)-grade methanol, analytical-grade acetic acid, analytical-grade ethyl acetate, analytical-grade ethanol, analytical-grade acetonitrile, analytical-grade hexane, analytical-grade acetic acid, analytical-grade sodium chloride, and analytical-grade sodium sulfate were sourced from Merck (Darmstadt, Germany).