I have just begun Real World Research by Colin Robson.
Its definition in the glossary of Purposive Sampling is 'choice of sample of participants based on the requirements of the research questions or theoretical considerations. generalisation of findings must be based on non-statistical bases'.
From my reading its all depends on the research questions what type of sample you use. If the particular data collection method is a survey for which you will be having quantitative responses I don't think purposive sampling is correct. It is used where there is qualitative data collected. i.e. those in word form, observation, interviews rather than survey. unless the responses in your survey will be of qualitative form which then would suggest purposive sampling is a correct term to describe your data collection sample.
Hope this helps.
Kitten