Learn Italian: L'infermiere riempie la provetta in un solo minuto. - The nurse fills the test tube in just one minute.

In Italian, in is used to express how long it takes to complete an action. The nurse spends one minute actively filling the tube. If the sentence said tra un solo minuto, it would change the meaning to say that the nurse will start the action of filling the tube one minute from now.

Could I say solo un minuto instead of un solo minuto?

Yes, both are perfectly fine. However, using the adjective form and placing it directly between the article and the noun (un solo minuto) translates closer to 'a single minute'. It makes the speed of the action sound slightly more emphatic than saying solo un minuto (only one minute).

How is the verb riempire conjugated here to get riempie?

Riempire is conjugated like a regular non-isc -ire verb, but because its stem ends in the vowel i (riempi-), that vowel is retained in the conjugation. This gives us forms like io riempio, tu riempi, and lui/lei riempie.

Does l'infermiere refer to a male or female nurse?

L'infermiere specifically refers to a male nurse, as indicated by the -ere ending. A female nurse would be l'infermiera.