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the present study, three vitamins (vitamin B 12 at 0.035 percent, folic acid at 0.117 percent, and vitamin D 3 at 0.189 percent) and two minerals (chromium chloride at 0.144 percent and zinc oxide at 0.692 percent) were cho- sen for testing. Methods Equipment. Blending uniformity studies of the MVM tablet formulation were conducted in a 5-cubic-foot Patterson-Kelly V-type blender (Hebeler, Tonawanda, NY). The final blend was compressed using a 36-station tablet press (Libra from Kikusui, Lakewood, NJ) operat- ing at 30 rpm and equipped with oval tooling of 0.625 by 0.356 inch. Batches and batch size. Three pilot batches of the same formula were made. The formula contained calcium carbonate (55.556 percent), ascorbic acid (4.630 per- cent), selenium yeast (3.472 percent), vitamin E (2.249 percent), ferrous fumarate (1.744 percent), thiamine mononitrate (0.848 percent), zinc oxide (0.692 percent), calcium pantothenate (0.619 percent), riboflavin (0.585 percent), niacinamide (0.397 percent), vitamin A acetate (0.343 percent), biotin (0.320 percent), pyridoxine hydrochloride (0.294 percent), vitamin K 1 (0.292 per- cent), vitamin D 3 (0.189 percent), chromium chloride (0.144 percent), folic acid (0.117 percent), vitamin B 12 (0.035 percent), microcrystalline cellulose (26.696 per- cent), and magnesium stearate (0.778 percent). Each batch weighed 50.000 kilograms. Blending, sampling, and analysis. As a pre-blending step, we added vitamin B 12 , riboflavin, folic acid, chromium chloride, vitamin K 1 , pyridoxine hydrochlo- ride, thiamine mononitrate, biotin, niacinamide, calcium pantothenate, vitamin D 3 , and vitamin A acetate into a clean polyethylene bag. We blended the ingredients by tumbling the bag for 3 minutes by hand. We then passed the pre-blend and the remaining ingredients—except the magnesium stearate—through a 12-mesh screen, into the blender and blended for 15 minutes. Next, we passed the magnesium stearate through the 12-mesh screen into the blender and blended for 3 minutes. We collected two samples each from the bottom, mid- dle, and top of the blender's discharge stream. Each sam- ple weighed approximately 300 grams. For each sample, vitamin B 12 , folic acid, and vitamin D 3 were analyzed using a high-performance liquid chromatography instru- ment (Alliance HPLC from Waters, Milford, MA). Chromium and zinc were analyzed by using an induc- tively coupled plasma instrument (Optima 5300DV from Perkin Elmer, Waltham, MA) according to Pharmavite's standard methods. Tabletting, sampling, and analysis. The final blend was compressed into 0.900-gram tablets, and we col- lected a composite sample from each lot and then ran- domly chose 10 tablets from the sample for testing. Vitamin B 12 , folic acid, and vitamin D 3 were analyzed using the same test equipment and methods we used on the blending samples. Chromium and zinc were analyzed using the same test equipment and methods we used on the blending samples. Physical testing. We measured each tablet's weight, thickness, hardness, and disintegration time. Results and discussion Test results for the vitamin B 12 , folic acid, vitamin D 3 , chromium, and zinc were all in the range of 90.0 to 110.0 percent of their respective specified amounts. Table 1 summarizes the RSDs of the uniformity data of the final blend samples. According to the FDA's 1999 draft Guidance, an RSD of 5.0 percent or less indicates that an ingredient is uni- formly distributed in the final blend [2]. Folic acid, chromium, and zinc were homogenous in all three lots, while vitamin B 12 was uniform in one lot and non-uniform in two lots. Likewise, vitamin D 3 was uniform in one lot and non-uniform in two lots. The higher RSDs for uniformity in vitamin B 12 and vit- amin D 3 may have been caused by sampling errors during the lab analysis. Specifically, the errors could have arisen because we used a stainless steel spatula in weighing pow- der samples of about 900 mg. That method could easily have produced different errors for some of the lower-con- tent ingredients due to the effect of an electrostatic charge [1]. In fact, the effect of the charge on the unifor- mity of the vitamin B 12 and vitamin D 3 would likely have been greater than on the folic acid, chromium chloride, and zinc oxide because vitamin B 12 and vitamin D 3 are Tablets & Capsules October 2017 23 Table 1 RSD percentages of final blend samples (n = 6)* Lot 1 Lot 2 Lot 3 Vitamin B 12 5.97 3.74 5.85 Folic acid 0.86 0.99 2.03 Vitamin D 3 6.23 2.28 7.17 Chromium 5.03 3.43 3.47 Zinc 3.83 3.45 2.22 *FDA limit: ≤ 5.0% Table 2 Content uniformity of MVM tablets (n = 10)* Lot 1 Lot 2 Lot 3 Vitamin B 12 3.6 0.4 0.5 Folic acid 6.7 12.6 12.9 Vitamin D 3 11.0 0.5 0.4 Chromium 0.8 9.7 9.1 Zinc 6.7 3.6 6.8 *USP limit: ≤ 15.0 If the lower-content active ingredients are uniform in the blend and tablet, are all actives in the tablet likewise homogenous?