Live injection

The MicroSAM has a two-stage injection system. Using a micro injection valve, a defined quantity of sample is first brought up to the carrier gas pressure. This eliminates the pressure-dependent error in the dosing quantity present with conventional systems. In the second stage, the sample is transferred to the column by a valveless micro injection system (live dosing). The result is an "active" injection.

The injection volume can be varied time-controlled, and exactly matched to the column requirements.

Valveless live column switching

Because of the high dead volume of conventional valves, only the valveless version can be considered for a miniaturized system. In this case, the generation of differences in flow using several electronic pressure regulators at appropriate positions of the column setup causes a change in the flow directions. (The system operates according to the Wheatstone principle, but pneumatically.) The functions "Cut" and "Backflushing" can then be implemented free of dead volume.

The column system

The column system consists of two or three capillary columns connected in sequence. Micro TCDs or micro live circuits are installed in sequence ("inline") upstream and downstream of the individual columns. Three electronic pressure regulators supply the columns with carrier gas and carry out the switching functions (injection, backflushing and cut).

By using narrow-bore capillary columns, the separation at high resolution is carried out within a much shorter time, approx. factor 2 to 3 compared to standard capillary columns.

Electronic pressure regulators

A high pressure stability together with rapid changing rates in the hPa range are required for precise and fast switching. This is achieved in the electronic pressure regulators by means of a piezo actuator.

Detector

The micro TCDs (based on silicon wafer technology) work on the principle of continuous measurement of the different thermal conductivities of the carrier gas and the components to be measured.

The measurement can be carried out without falsification by avoiding catalytic effects on the heating wires and maintaining a constant flow velocity. This permits consistent in-line detection, i.e. without qualitative or quantitative losses of substances.

Application modules

The application modules contain live injection and live switching. The modules D06, D08 and D11 have one separating column less than the modules D01, D02 and D09. The modules D06, D08 and D11 have one detector less than the modules D01 and D02. The application modules are suitable for separation of the components described below. However, when defining the suitable application module for an actual, customer-specific measuring task, technical evaluation by our Support Team is required.

D01, D02 and D08:
These modules contain separating columns that can be impaired in their separating performance by humidity in the carrier gas. For this reason, a carrier gas dry filter (filter set: Article No. A5E00400116) integrated on support bracket of the MicroSAM or supplied as a separate part.

The application modules are suitable for separation of the components described below.

Application modules D01, D02 and D09

Application modules D06, D08 and D11

Application

Various solution concepts are available:

• Adjustment without method development (on request)
  • Run-out ex factory
    The application modules are standardized. The functionality of the MicroSAM is proven with a specified carrier gas, exact setting of the oven temperature and the carrier gas inlet pressures, and with a standard calibration gas. The measured components and switching functions (live injection, backflushing, cut) are saved.
  • Commissioning on site
    All application modules are standardized, i.e. the analytical hardware is defined and cannot be changed. The specific settings are carried out on site during commissioning.
• Adjustment with method development
  Non-standardized applications require specific method development:
  An optimum solution is elaborated on the basis of an existing specification and a selected calibration gas or with application of a customer sample.