Please read this article.

http://link.springer.com/article/10.1007/s12601-012-0006-6#page-1

Most "true" laboratory equipment is totally overpriced, especially when you consider that most time the electronic inside is a mass product used also in much cheaper equipment for the non-science market. Try this ones (sorry in German): https://www.conrad.de/de/voltcraft-pht-01-atc-ph-messstick-einpunkt-0-a-14-ph-101121.html?gclid=CKy74PTn5s0CFUgq0wodoScApQ&insert_kz=VQ&hk=SEM&WT.srch=1&WT.mc_id=google_pla&s_kwcid=AL!222!3!97483726737!!!g!!&ef_id=V4EnnQAABHDbwFBU:20160709163437:s

https://www.conrad.de/de/Search.html?gclid=CPGbvZzo5s0CFUQcGwodVk4GKA&search=o2+sensor&insert_kz=NA&hk=SEM&WT.srch=1&log=sea&s_kwcid=AL!222!3!109763511441!b!!g!!o2%20sensor&ef_id=V4EnnQAABHDbwFBU:20160709163558:s

Hi there,

I think it is import to read some guidelines in terms of sampling in the field before you decide which instrument should be used in your study.

I suggest a book as below.

Douglas, D., & McConchie, D. (1994). Analytical sedimentology. London, UK: Chapman and Hall.

Hope it helps.

Cheers

Xiaoguang

Thank you all for your kind responses and my apologies for the much delayed response.