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Selection of Grinding Vials for Sample Processing

In order to thoroughly homogenize a sample, the nature of the sample and its mass (size) must be matched with both a suitable vessel (vial, plate, tube) and the appropriate grinding media. Bead beating can be done in a variety of vessels, including disruption tubes, grinding vials and microwell plates. Vials made of polycarbonate are the best option for bead beating because polycarbonate is durable, clear and impact resistant, even at cryogenic temperatures. Unlike conical vials, all OPS Diagnostics' grinding vials, available in volumes of 4 ml, 15 ml and 50 ml, are self-standing and have a re-enforced flat bottom to prevent cracking of the base during homogenization (Table 1).

The size (mass and volume) and type of sample (sample resiliency) must be matched with a homogenization vessel of an appropriate volume as well as grinding media that can effectively homogenize the sample. Grinding media must be able to move freely to impact the sample; therefore, homogenization vessels must not be overfilled with a combination of sample, beads and/or buffer. Generally, the samples should take up no more than a sixth of the volume of the vessel, and grinding media should take up no more than a third of the volume of the vessel. As well as overfilling vessels, processing very small samples in larger grinding vials can also lead to inefficient homogenization and damage to the grinding vessel.

The type of grinding vessel (vial, plate, tube) must also correlate with the type of bead beater that is used to shake and disrupt the sample (Table 1). In choosing a bead beater, the number of samples processed simultaneously should be taken into consideration, especially for laboratories processing hundreds of samples daily (Table 1). Multitube bead beaters can process small tissue samples in 2 ml disruption tubes. All high throughput homogenizers can process disruption tubes, 4 and 15 ml grinding vials and deep well plates. The 1600 MiniG™ and 2010 GenoGrinder® have the capability to process tall grinding vials, including the 50 ml polycarbonate vials and conical centrifuge tubes. The HT Homogenizer™ is equipped to process disruption tubes and 4 and 15 ml grinding vials.

Table 1. Homogenization vessel characteristics and homogenizer capacities.

Disruption Tube 4 ml Grinding Vial 15 ml Grinding Vial 50 ml Grinding Vial
Dimensions (in) 0.4 x 1.7 0.5 x 2 1.125 x 1.667 1.125 x 3.5
Grinding Load¹ 0.5-0.8 ml 0.5-2 ml 2-8 ml 9-16 ml
Autoclavable Yes Yes Yes Yes
Cryogenic Capability No Yes Yes Yes
Grinding Media Vary 1 x 3/8" ball 2 x 7/16" balls 2 x 7/16" balls
2 x 9/16" balls
HT Mini™ 3 (non-skirted) - - -
HT 24™ 24 - - -
HT Homogenizer™ 24 24 5 -
1600 MiniG™ 50 48 10 5
2010 GenoGrinder® 100 96 20 10

The key to effectively homogenizing samples is to find a balance between sample mass, vessel volume and grinding media size. Samples including plant tissue, seeds and animal tissue can be effectively processed by selecting homogenization vessels according to the parameters listed below in Table 2.

Table 2. Recommended homogenization parameters for sample types and size with various homogenization vessels.

Disruption Tube 4 ml Grinding Vial 15 ml Grinding Vial 50 ml Grinding Vial
Plant Tissue
Sample Mass Up to 100 mg 100-200 mg Up to 1 gm 1-3 gm
Buffer Volume³ 600 µl 2 ml 6 ml 12 ml
Grinding Balls 8 x 2.8 mm 1 x 3/8" 2 x 7/16" 2 x 7/16"
Bead Beater Speed High High High High
Sample Size - ≤ 500 mg (1 kernel) ≤ 4 gm (10 kernels) 4-8 gm (≈22 kernels)
Grinding Balls - 1 x 3/8" 2 x 7/16" 2 x 9/16"
Bead Beater Speed - High High ≤1500 rpm
Animal Tissue
Sample Size Up to 100 mg 100-200 mg Up to 2 gm 2-4 gm
Buffer Volume³ 600 µl 1 ml 6 ml 12 ml
Grinding Balls 8 x 2.8 mm 1 x 3/8" 2 x 7/16" 2 x 7/16"
Bead Beater Speed high high high high

¹ Processing grinding vials with less than the recommended grinding load or empty can result in damage to the vial.

²The 9/16” grinding balls should only be used when processing large quantities of seeds in the 50 ml grinding vials. These balls provide an extreme amount of force to the sample as well as the grinding vessel. Therefore, an empty or under-filled vial will crack.

³Omit buffer when dry grinding plant tissue or cryogenic grinding plant and animal tissues.