What sampling method is used for mercury analysis directly?

The sampling method used for the direct analysis of mercury is typically associated with specific techniques that enable the identification and quantification of mercury in samples without significant preparation or intervention. One of the common methods for direct analysis of mercury is through the use of UV spectroscopy techniques. This method can measure the absorbance of mercury at specific wavelengths, allowing for its direct quantification in various matrices.

In contrast, charcoal with iodine is used in the collection of volatile mercury for later analysis rather than a direct analysis method. It typically serves to capture mercury vapors from the air, making it a preparatory sampling method rather than a direct analytical technique.

Chemiluminescence is generally used for the detection of specific gaseous compounds and might not be directly related to the quantitative analysis of mercury in environmental samples.

Phase contrast microscopy is primarily utilized for visualizing biological specimens or particulates and is not a suitable method for the direct analysis of mercury.

Therefore, the sampling method for direct mercury analysis is best represented by UV techniques, as they allow for immediate measurement of mercury without the need for sample manipulation or collection.