If the sample temperature is not being removed in a freeze dryer, there may be several possible causes. Here are some troubleshooting steps you can follow:

Check the vacuum level: The primary mechanism for removing moisture during freeze drying is creating a vacuum. Make sure the vacuum pump is functioning properly and that the vacuum level is within the recommended range. If the vacuum level is low, it may not be sufficient to remove the moisture effectively.

Inspect the condenser: The condenser is responsible for cooling the sample to freeze it and collecting the vaporized moisture during the drying process. Check if the condenser is clean and free from any ice buildup or obstructions. Ice accumulation can prevent proper heat transfer, leading to inadequate cooling and inefficient drying.

Verify the temperature settings: Ensure that the temperature settings on the freeze dryer are correctly configured. The freezing temperature should be set low enough to freeze the sample completely. The drying temperature should be set above the freezing point but below the sublimation temperature of the sample.

Consider the sample composition: Some samples may have properties that make them difficult to freeze dry efficiently. For example, samples with high fat or oil content can form a layer that inhibits heat transfer. In such cases, pre-treating the sample or adjusting the drying parameters might be necessary.

Examine the sample preparation: Improper sample preparation can affect freeze drying efficiency. Ensure that the sample is spread out evenly on the tray or vials, allowing for maximum surface area exposure. If the sample is too thick or unevenly distributed, it may hinder the heat transfer and delay the drying process.

Consult the manufacturer or manual: If none of the above steps resolve the issue, consult the manufacturer's guidelines or the freeze dryer manual for troubleshooting specific to your equipment. They may provide additional insights or recommend further steps.

If the problem persists or if you are unsure about performing any troubleshooting steps, it's best to contact the manufacturer's customer support or an expert in freeze drying equipment to assist you in diagnosing and resolving the issue.