for+ to

Snazzy

只记得表目的用to. why is 'for' used here?

567.    Originally developed for detecting air pollutants, a technique called proton-induced x-ray emission, which can quickly analyze the chemical elements in almost any substance without destroying it, is finding uses in medicine, archaeology, and criminology.(A) Originally developed for detecting air pollutants, a technique called proton-induced x-ray emission, which can quickly analyze the chemical elements in almost any substance without destroying it,
(B) Originally developed for detecting air pollutants, having the ability to analyze the chemical elements in almost any substance without destroying it, a technique called proton induced x-ray emission
(C) A technique originally developed for detecting air pollutants, called proton-induced x-ray emission, which can quickly analyze the chemical elements in almost any substance without destroying it,
(D) A technique originally developed for detecting air pollutants, called proton-induced x-ray emission, which has the ability to analyze the chemical elements in almost any substance quickly and without destroying it,
(E) A technique that was originally developed for detecting air pollutants and has the ability to analyze the chemical elements in almost any substance quickly and without destroying the substance, called proton-induced x-ray emission,

ecsniffer

for同样可以表目的的呀
longman:
for:
used to say what the purpose of an object, action etc is
for doing something
a knife for cutting bread
What did you do that for? I've bought him a watch for his birthday. the documents prepared for his defence

Snazzy

agreed, ecsniffer.
here is an example: OG 42
... worried about ... to increase as a result of deep cuts in the value of the dollar, has formed a group to study ways to sharpen our competitiveness.

there are a lot of such examples

my question is : when do we use 'for', and when 'to'? thanks

2love2live

I will say they are 99.9999999999999999999% same - my humble opinion.

but taste the slight difference:

they developed a new device to detect chemical weapons - 感觉这句主要讲他们要去发现化武
they developed a new device for detecting chemical weapons, - 感觉这句主要讲他们发明了新东东

个人见解，胡说八道也不一定，chew it with caution