{"id":43889,"date":"2025-04-17T22:12:33","date_gmt":"2025-04-17T22:12:33","guid":{"rendered":"https:\/\/www.alicat.com\/?p=43889"},"modified":"2025-12-12T18:52:10","modified_gmt":"2025-12-12T18:52:10","slug":"gaschromatographie-durchfluss-und-druck","status":"publish","type":"post","link":"https:\/\/www.alicat.com\/de\/articles\/gas-chromatography-flow-and-pressure\/","title":{"rendered":"Massendurchfluss- und Druckregelung f\u00fcr die Gaschromatographie"},"content":{"rendered":"

[et_pb_section fb_built=”1″ _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_row _builder_version=”4.27.4″ _module_preset=”default” custom_padding=”2em||0px||false|false” locked=”off” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”4_4″ _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_heading title=”Flow and Pressure Control for Gas Chromatography” _builder_version=”4.27.4″ _module_preset=”default” custom_css_free_form=”selector h1 {|| text-wrap: pretty;||}” global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_heading][et_pb_heading title=”How to control flow and pressure of gases to achieve better process insights and decrease process variability” _builder_version=”4.27.4″ _module_preset=”default” title_level=”h2″ custom_css_free_form=”selector h2 {|| text-wrap: pretty;||}” global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_heading][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”]By Mike Zecchino<\/span>[\/et_pb_text][et_pb_divider color=”#2A3B47″ divider_weight=”2.5px” _builder_version=”4.27.4″ _module_preset=”default” height=”0px” custom_margin=”3rem||3rem||true|false” global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_divider][\/et_pb_column][\/et_pb_row][et_pb_row _builder_version=”4.27.4″ _module_preset=”default” custom_padding=”0px||0px||true|false” locked=”off” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”4_4″ _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” custom_margin=”||2rem||false|false” global_colors_info=”{}” theme_builder_area=”post_content”]Accurate gas chromatography (GC) analysis depends upon the consistent flow\/pressure of the sample and carrier gases through the apparatus. Alicat instruments have numerous applications to ensure accurate measurement and control of flow and pressure in GC systems, for improved performance and simplicity. For more on gas chromatography applications, see our page on verifying and optimizing gas chromatography processes<\/a>.[\/et_pb_text][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” max_width=”66%” max_width_tablet=”100%” max_width_phone=”” max_width_last_edited=”on|phone” module_alignment=”center” custom_margin=”||0px||false|false” custom_padding=”||2rem|2rem|false|false” custom_padding_tablet=”|||2rem|false|false” custom_padding_phone=”|||0rem|false|false” custom_padding_last_edited=”on|phone” custom_css_free_form=”selector figure {|| display: table;|| margin-left: auto;|| margin-right: auto;|| text-align: center;||}||||selector figcaption {|| caption-side: bottom;|| display: table-caption;||}||||selector img {|| margin-bottom: 1rem;||}” global_colors_info=”{}” custom_css_main_element_tablet=”float: right;” custom_css_main_element_phone=”float: none;” custom_css_main_element_last_edited=”on|desktop” theme_builder_area=”post_content”]<\/p>\n

\"A<\/p>
Figure 1.<\/strong> A gas chromatography system.<\/figcaption><\/figure>\n

[\/et_pb_text][et_pb_heading title=”Flow and Pressure Control in a GC” _builder_version=”4.27.4″ _module_preset=”default” title_level=”h3″ global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_heading][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” custom_margin=”||2rem||false|false” global_colors_info=”{}” theme_builder_area=”post_content”]Gas chromatography systems vary in design. In general, however, most GC systems consist of the components shown in Figure 2. Typical applications for flow control devices are also shown, and each is described in the following text.[\/et_pb_text][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” module_alignment=”center” custom_margin=”||0px||false|false” custom_padding=”||2rem||false|false” custom_padding_last_edited=”off|desktop” custom_css_free_form=”selector figure {|| display: table;|| margin-left: auto;|| margin-right: auto;|| text-align: center;||}||||selector figcaption {|| caption-side: bottom;|| display: table-caption;||}||||selector img {|| margin-bottom: 1rem;||}” locked=”off” global_colors_info=”{}” custom_css_main_element_last_edited=”on|phone” theme_builder_area=”post_content”]<\/p>\n

\"Applications
Figure 2.<\/strong> Applications for Alicat meters and controllers in a gas chromatography system.<\/figcaption><\/figure>\n

[\/et_pb_text][et_pb_heading title=”Upstream Flow Control” _builder_version=”4.27.4″ _module_preset=”default” title_level=”h3″ global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_heading][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” custom_margin=”||2rem||false|false” global_colors_info=”{}” theme_builder_area=”post_content”]A GC system is calibrated for specific pressure and temperature conditions, gas types, and column length. To achieve accurate results, the gas flow rate or gas velocity through the GC must be precisely controlled.<\/p>\n

An Alicat MC mass flow controller<\/a> upstream of the GC (Figure 2 A) can regulate the process gas or batch a specific amount of gas volume on the sample line. Automatic batch dispensing can improve repeatability and simplify the analysis process.<\/p>\n

The controller\u2019s totalizer function<\/a> can continuously log gas usage over time, both for record keeping and as valuable diagnostic data to interpret anomalies or unexpected results.<\/p>\n

In an explosive environment, an intrinsically safe IS\u2011Max controller<\/a> can maintain consistent flow control. Using a single device for metering and control simplifies the GC system design and improves safety by eliminating additional sensors, wiring, and valves.[\/et_pb_text][et_pb_heading title=”Carrier Gas” _builder_version=”4.27.4″ _module_preset=”default” title_level=”h3″ global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_heading][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” custom_margin=”||2rem||false|false” global_colors_info=”{}” theme_builder_area=”post_content”]As with the sample gas, the carrier gas flow and pressure must be precisely controlled for accurate GC readings. Alicat instruments (Figure 2 B) can control carrier gas flow with an accuracy of ± 0.5% of reading or ± 0.1% of full scale (whichever is greater), providing repeatable and verifiable results. The instruments can also improve calibration certainty.<\/p>\n

The totalizer function on Alicat instruments records carrier gas usage, even for custom calibration mixes. The totalizer function can also retain flow history, which can be useful both for record keeping and for diagnosing process anomalies.[\/et_pb_text][et_pb_heading title=”Downstream Flow Control” _builder_version=”4.27.4″ _module_preset=”default” title_level=”h3″ global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_heading][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” custom_margin=”||2rem||false|false” global_colors_info=”{}” theme_builder_area=”post_content”]A mass flow meter<\/a> located after the GC sensor can monitor the quantity of vented gas (Figure 2 C), to provide a constant validation of the GC. With a response rate of under 10 milliseconds, Alicat flow meters can detect sudden changes in vented gas that may indicate a problem with the setup or an unintended reaction, such as condensation.[\/et_pb_text][et_pb_heading title=”Absolute and Gauge Pressure Control” _builder_version=”4.27.4″ _module_preset=”default” title_level=”h3″ global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_heading][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” custom_margin=”||2rem||false|false” global_colors_info=”{}” theme_builder_area=”post_content”]An Alicat pressure controller<\/a> downstream of the GC oven can control absolute back pressure on the column. Control based on absolute pressure eliminates the variability associated with the pressure and temperature measurements required for gauge pressure control. It provides a simple reference point for GC calculations that is not affected by changes in atmospheric pressure during the run.<\/p>\n

The ability to switch between gauge pressure and absolute pressure makes Alicat instruments much more flexible than other metering and control options.[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row column_structure=”1_2,1_2″ use_custom_gutter=”on” gutter_width=”2″ make_equal=”on” _builder_version=”4.27.4″ _module_preset=”default” custom_padding=”0px||0px||true|false” custom_css_free_form=”@media all and (min-width: 768px) and (max-width: 980px) {|| selector .et_pb_column {|| width: 50%;|| }||}||” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”1_2″ _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” module_alignment=”center” custom_margin=”||0px||false|false” custom_padding_tablet=”||||false|false” custom_padding_phone=”|0rem|2rem||false|false” custom_padding_last_edited=”on|phone” custom_css_free_form=”selector figure {|| display: table;|| margin-left: auto;|| margin-right: auto;|| text-align: center;||}||||selector figcaption {|| caption-side: bottom;|| display: table-caption;||}||||selector img {|| margin-bottom: 1rem;|| max-height: 300px;|| object-fit: contain;||}” locked=”off” global_colors_info=”{}” custom_css_main_element_last_edited=”on|phone” theme_builder_area=”post_content”]<\/p>\n

\"Alicat<\/p>
Figure 3.<\/strong> Alicat MC 50 SCCM mass flow controller<\/figcaption><\/figure>\n

[\/et_pb_text][\/et_pb_column][et_pb_column type=”1_2″ _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” max_width_tablet=”” max_width_phone=”” max_width_last_edited=”on|desktop” module_alignment=”center” custom_margin=”||0px||false|false” custom_padding_tablet=”” custom_padding_phone=”” custom_padding_last_edited=”on|phone” custom_css_free_form=”selector figure {|| display: table;|| margin-left: auto;|| margin-right: auto;|| text-align: center;||}||||selector figcaption {|| caption-side: bottom;|| display: table-caption;||}||||selector img {|| margin-bottom: 1rem;|| max-height: 300px;|| object-fit: contain;||}” locked=”off” global_colors_info=”{}” custom_css_main_element_last_edited=”on|phone” theme_builder_area=”post_content”]<\/p>\n

\"Alicat
Figure 4.<\/strong> Alicat IS-Max 1 SLPM intrinsically safe mass flow controller<\/figcaption><\/figure>\n

[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”4_4″ _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_heading title=”Humidity” _builder_version=”4.27.4″ _module_preset=”default” title_level=”h3″ locked=”off” global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_heading][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” max_width=”55%” max_width_tablet=”55%” max_width_phone=”100%” max_width_last_edited=”on|phone” module_alignment=”center” custom_margin=”||0px||false|false” custom_padding=”||2rem|3rem|false|false” custom_padding_tablet=”||2rem|2rem|false|false” custom_padding_phone=”|||0rem|false|false” custom_padding_last_edited=”on|phone” custom_css_main_element=”float: right;” custom_css_free_form=”selector figure {|| display: table;|| margin-left: auto;|| margin-right: auto;|| text-align: center;||}||||selector figcaption {|| caption-side: bottom;|| display: table-caption;||}||||selector img {|| margin-bottom: 1rem;||}” locked=”off” global_colors_info=”{}” custom_css_main_element_tablet=”float: right;” custom_css_main_element_phone=”float: none;” custom_css_main_element_last_edited=”on|phone” theme_builder_area=”post_content”]<\/p>\n

\"Gas<\/p>
GC system in a laboratory environment.<\/figcaption><\/figure>\n

[\/et_pb_text][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” custom_margin=”||2rem||false|false” locked=”off” global_colors_info=”{}” theme_builder_area=”post_content”]In some GC applications, the amount of humidity is an important consideration for verifying the makeup of the sample gas. Alicat meters and controllers can include an optional, relative humidity sensor with an accuracy of \u00b1\u00a01.8% RH at + 23 \u00b0C. The internal sensor provides an in\u2011process check, simplifying the setup while accounting for humidity in flow calculations.<\/p>\n

Gas chromatography results can be affected by any changes in operating conditions, etc. Alicat instruments can control mass flow or volumetric flow while also monitoring temperature, absolute pressure, gauge pressure, humidity, and other variables. The instruments can be configured using the built\u2011in display<\/a> or using a variety of industrial communication protocols<\/a>. By providing accurate data and combining metering and control, Alicat instruments simplify GC setups while improving their accuracy, calibration, and safety.[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row custom_padding_last_edited=”on|phone” _builder_version=”4.27.4″ _module_preset=”default” width_tablet=”80%” width_phone=”90%” width_last_edited=”on|phone” custom_padding=”0px|5vw|0px|5vw|true|true” custom_padding_tablet=”|0rem||0rem|false|true” custom_padding_phone=”|0rem||0rem|false|true” locked=”off” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”4_4″ _builder_version=”4.27.4″ _module_preset=”default” background_color=”#F6F6F6″ custom_padding=”3rem|3rem|2rem|3rem|false|true” border_radii=”on|15px|15px|15px|15px” border_width_all=”3px” border_color_all=”#2A3B47″ global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_heading title=”Summary” _builder_version=”4.27.4″ _module_preset=”default” title_level=”h3″ title_text_color=”#2A3B47″ global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_heading][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” text_text_color=”#2A3B47″ text_font_size=”15px” custom_margin=”||2rem||false|false” global_colors_info=”{}” theme_builder_area=”post_content”]<\/p>\n