be done vs have been done vs had been done

Question: Hi Ian, What's the difference between "something be done" and "something have been done". For example, "This compound was finished last Friday." & "This compound had been finished last Friday."

Answer: These are all examples of statements in the passive voice (被动语态). They are just using different tenses of the passive voice:

• sth is done (present simple tense)
• sth was done (past simple tense)
• sth has been done (present perfect tense)
• sth had been done (past perfect tense)
  

The key to choosing the right one is to think about the time or time period you are referring to in your sentence:

1. is/are done (present simple tense) – for things carried out regularly (e.g., every day, once a week, on a monthly basis) or things that are always true regardless of time (i.e., things that will be true in the past, present and future).

• The compounds are dispatched from our BDA site to our clients every Friday afternoon.
  

2. was/were done (past simple tense) – for things that happened in the past and are over or finished already (often used with time phrases like "yesterday", "last Friday", "in 2012")

• This compound was submitted last Friday.
  

3. have/has been done (present perfect tense) – used when the time period you are referring to starts in the past and continues up to now (often used with time phrases such as "since…", "so far, …", "up to now")

• A total of 100 compounds have been submitted by our team since the start of the project.
• So far, a purity of 92% has been achieved, but we believe we can improve it through further optimization.
  

4. had been done (past perfect tense) – for talking about "the past of the past" – it's used to refer to something that happened in the past, but emphasizing that it happened before another time in the past (it's most commonly used with phrases such as "by last Thursday", "before 2020")

• Actually, Jim and I had been friends for several years before we joined Pharmaron.
• We discovered that the compound hadn't been approved by the QA team before it was delivered. I apologize for this oversight.
  

Notice how both these examples have one part of the sentence in the past simple tense ("joined Pharmaron"; "was delivered") and one part in the past perfect tense ("had been friends"; "hadn't been approved"). Both events are in the past, but the one using the past perfect tense happened before the one using the past simple tense.

So, going back to your example, both choices are possible depending on the situation:

• Example 1: This compound was completed last Friday. (past simple tense)
  

This sentence is the best choice if you are emphasizing when it was completed (last Friday), since last Friday is in the past and has no other relation to any time period.

• Example 2: This compound had been competed by last Friday. (past perfect tense)
  

This sentence implies that the completion happened before the Friday deadline. The Friday deadline is already in the past and the completion happened before then (i.e., "the past of the past").

Here are some other examples that emphasize this "past of the past" relationship:

• Since the compound had been completed by last Friday, it was dispatched with last week's shipment.
  

It's quite commonly used in the negative too:

• This compound hadn't been completed by last Friday, so we were unable to ship it to you in last week's delivery.
  

Hope that answers your question. Feel free to make some examples of your own or ask follow-up questions in the comments below.