摘要:
A capillary absorption spectrometer (CAS) (100) and process are described that provide sensitive, stable, and accurate absorption measurements of analytes in a sample gas including isotopologues of carbon and oxygen obtained from gas and biological samples. The CAS (100) comprises a continuous-wave excitation laser (4), a modulation device (2), an optical isolation device (18) and a detection device (54). The optical isolation device preferably comrises a turbulence generator (20) which generates turbulences in a medium (24). Optical feedback to the laser (4) can be eliminated. The CAS (100) further targets naturally occurring variations in carbon and oxygen isotopes to avoid the need for isotopically-labeled mixtures, which allows study of samples taken from the field without modification. The CAS (100) permits sampling in vivo permitting real¬ time ambient studies of microbial communities and provides isotopic images of microbial communities allowing tracking of nutrients at the single cell level.