Does anybody have experience or good ideas as to the best way to determine the dry mass of soft tissue samples? Supposedly dry freezing is the way to go. However, are there ways for those of us without a lyophilizer or convenient access to one to dry soft tissue samples? Intuitively, I was going to put the samples in a vacuum oven at 37 C and weight it intermittently until weight doesn't change anymore? A colleague also suggested adding a desiccant to the oven? Any other suggestions? Insights? Thanks a ton!
Drying at 105 C is the most common procedure. Why not use that? The sample will not be eatable anyway. You might want to use it for further investigations and then another drying procedure might be more appropriate.
Dry weights are determined by placing sample aliquots in 10 mL, pre-weighed, clean, dry beakers. Beakers are pre-dried in an oven at 105ºC and cooled in a desiccator. Once the beakers have cooled for a minimum of 30 minutes, the weight of the empty beaker is recorded to the nearest 1 mg. Approximately 1 to 2 g of thawed, thoroughly homogenized sample is placed into a labeled beaker using a solvent rinsed stainless steel spatula. The weight of the beaker plus wet sample is recorded to 1 mg. Tissue samples are dried in a 105ºC oven for at least 24 hours followed by cooling in a desiccator for at least 30 minutes prior to weighing. Samples and beakers are weighed to the nearest 1 mg. Samples are placed back into the oven and dried for another 24 hours at 105°C, cooled in a desiccator and weighed. This cycle is repeated until successive weight differences are less than 4%
https://www.tdi-bi.com/analytical_services/environmental/NOAA_methods/Tissue%20Dry%20Weigt%20Determination.pdf
An alternative - as you have a vacuum oven - is to work at 70°C. there is no risk of burning and only needs a few hours for completion.
A-Generalidades: El método se basa en la perdida en masa que experimenta la muestra al ser calentada a una temperatura de 100°C ± 5°C, hasta peso constante.
B- Materiales
a- Estufa de secado, de tiraje natural o forzado, de temperatura regulable para 100°C ± 5C.
b- Placa de Petri de vidrio, de 100 mm de diámetro y no más de 30mm de profundidad c- Desecador con piedras de silicagel
d- Balanza Analítica
C-Procedimiento
a- Pesar 10 gramos de muestra húmeda homogeneizada (*), en una placa limpia, seca y previamente pesada.
b- Secar en estufa durante 24 horas, a 100°C ± 5°C
c- Sacar muestra de estufa, enfriar en un desecador a temperatura ambiente (45 minutos). Y pesar la muestra seca.
d- Verificar que el peso permanezca constante, secando 15 minutos adicionales. D-Cálculos
H %= (m – m1 x 100 )*m
ST%= 100 – H H: humedad,
% m: masa de la muestra inicial, gr.
m1: masa de la muestra seca o residuo, gr.
ST: sólidos totales (incluidas las grasas), en %
usar una gasa fina dentro de la capsula donde se pondra la muestra. La gasa y la capsula deben estar a peso constante. Después usar cualquier método de los propuestos
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