Department of Chemistry and Biochemistry, James Madison University, MSC 4501, Harrisonburg, Virginia 22807, USA.
Anal Chem. 2010 Oct 1;82(19):7935-42. doi: 10.1021/ac101366e.
We benchmark the performance of a photoacoustic spectrometer with a calculable cell constant in applications related to climate change measurements. As presently implemented, this spectrometer has a detection limit of 3.1 × 10(-9) W cm(-1) Hz(-1/2) for absorption by a gas and 1.5 × 10(-8) W cm(-1) Hz(-1/2) for soot particles. Nonstatistical uncertainty limited the accuracy of the instrument to ∼1%, and measurements of the concentration of CO(2) in laboratory air agreed with measurements made using a cavity ring-down spectrometer, to within 1%. Measurements of the enhanced absorption resulting from ultrathin (<5 nm), nonabsorbing coatings on nanoscale soot particles demonstrate the sensitivity of this instrument. Together, these measurements show the instrument's ability to quantitatively measure the absorption coefficient for species of interest to the climate and atmospheric science communities. Because the system constant is known, in most applications the acoustic response of this instrument need not be calibrated against a sample of known optical density, a decided advantage in field applications. Routine enhancements, such as improved processing of the photoacoustic signal and higher laser beam power, should further increase the instrument's precision and sensitivity.
我们在与气候变化测量相关的应用中，对具有可计算池常数的光声光谱仪的性能进行了基准测试。就目前的实现情况而言，该光谱仪对气体的吸收检测限为 3.1×10(-9) W cm(-1) Hz(-1/2)，对烟尘颗粒的检测限为 1.5×10(-8) W cm(-1) Hz(-1/2)。非统计不确定性将仪器的精度限制在约 1%，并且实验室空气中 CO(2)浓度的测量结果与使用腔衰荡光谱仪进行的测量结果一致，误差在 1%以内。对厚度小于 5nm（非吸收性）纳米级烟尘颗粒上的超薄涂层导致的增强吸收的测量，证明了该仪器的灵敏度。这些测量共同表明，该仪器能够定量测量对气候和大气科学界感兴趣的物质的吸收系数。由于系统常数是已知的，因此在大多数应用中，无需使用已知光密度的样品对该仪器的声响应进行校准，这在现场应用中具有明显优势。常规的改进，如对光声信号的更好处理和更高的激光束功率，应进一步提高仪器的精度和灵敏度。
