Gas syringe

Figure 1.3. Phase-modulation blood gas instrumentation based on a laser diode light source. Blood gas catheter (lop) direct reading blood gas syringe (bottom).

Many manufacturers now offer other sample injection systems compatible with the vacuum lock used for the solids probe. These include small (e.g., 75-ml) heatable batch inlet systems, usually accessible via syringe (gas syringe or GC microliter syringe for liquids), which can be particularly useful as inlets for mass reference compounds. Other probes are designed as flexible, easily removed connections to a gas chromatograph via some form of interface. 

DA, MEK, methyl vinyl ketone (MVK), propionaldehyde (PrH), and acetaldehyde (AcH) were analysed by on-line gas chromatography using a Varian 3400 GC equipped with a thermal conductivity detector and a 2m column containing 25% w/w B.B -oxydipropionitrile on Chromosorb W (80-100 mesh) operated at 60°C He was used as the carrier gas. Acetic acid (AcOH) was collected in 2ml of water from the effluent stream over a period of 1 hour and later analysed on a Porapak QS column at 150°C. CO2 was tested by removal of 2ml samples from the exit of the reactor with a gas syringe and injecting them onto a Porapak QS column operated at 60°C. 

Collect the hydrogen and obtain data on the volume evolved against time. The apparatus used could be a flask with delivery tube and a gas syringe or burette. A length of magnesium ribbon is suspended above excess acid and is allowed to fall into the acid as the timing starts. 

Altering the temperature using ice-water or hot water will change the position of equilibrium and illustrate its dependence on the exothermic or endothermic nature of the reaction. Similarly, changing the pressure by compressing a sample of the equilibrium mixture in a gas syringe will also move the position of equilibrium. 

Extractant phase None Direct aqueous injection (DAI) Static headspace with gas syringe (SHS) Dynamic headspace/ purge trap (P T)... 

She heats a 0.010 mo sample of each carbonate using the blue flame of the same Bunsen burner. She measures the time it takes for 100 cm3 of gas to be collected in the gas syringe. The following table shows her results. 

This exercise is based on an important practical technique of gas collection using a gas syringe. Following through the exercise should help develop your skills in presenting experimental data and calculating results from it. You will also be asked how the experiment could be modified to provide further data. 

The gas syringe method has been significantly improved [27. 28] by placing a heatable sampling column... 

Figure 6. Instantaneous sampling and product storage with a gas syringe and heatable sampling columns, after [28].

Mass of empty syringe Mass of gas + syringe Mass of gas (m)... 

Calibration Standards Prepare four HQ calibration standards as follows Add 0.50, 1.00, 2.00, and 3.00 mL of HQ Stock Solution into separate 10-mL volumetric flasks, then add 2.00 mL of Methyl Benzoate Stock Solution (internal standard) to each, dilute to volume with pyridine, and mix. In the same manner, prepare four DTBHQ Stock Solution calibration standards. Prepare the trimethylsilyl derivative of each standard as follows Add 9 drops of calibration standard to a 2-mL serum vial, cap the vial, evacuate with a 50-mL gas syringe, add 250 p,L of A.O-bistrimethylsilylacetamide, and heat at about 80° for 10 min. 

The liquid or solid sample is placed in a vial, which is sealed with a septum and heated to a predetermined temperature for a period of time. Equilibrium between the sample and vapor phase is then established and a portion of the volatiles in the gas phase (headspace) is subsequently injected onto the column. Several different methods have been used to transfer headspace volatiles into the GC, from manual withdrawal that uses a gas syringe, to sophisticated automatic sampling that involves transfer lines, and valves that lead directly onto the column. 

At the end of the sampling period, the valve is re-opened and the normal carrier gas flow resumed. In this way, the sample is introduced onto the column without using a gas syringe, thus avoiding fractionation due to pressure changes in the syringe. Since the system is closed, no headspace is lost during the transfer. The equipment requires no multiport valves, which reduces the number of components that come into contact with delicate samples. 

Dienes with K Co(CN)dH. An aqueous solution of K Co(CN)d (200 ml., 0.15M cobalt) was prepared in a hydrogen atmosphere, 260 ml. hydrogen being absorbed. A total of 35 ml. gaseous butadiene was injected in 5-ml. increments with a gas syringe. The isomeric butenes formed at cyanide to cobalt ratios of 5.1 and 7.0 are listed in Tables II and III under excess CoH. ... 

Because citrate, oxalate, and EDTA bind calcium and significantly reduce free calcium, heparin is the only acceptable anticoagulant for free calcium determinations. However, heparin, a polyanion, significantly lowers free calcium at the concentrations (30 to 100 U/mL or more) found in many conventional blood gas syringes (Table 49.3).8 - 02,495,496,56 addition, the use of hquid heparin should be avoided it can result in errors in free calcium because of dilution, as well as high and variable concentrations of heparin. 

Swanson JR, Heeter C, Limbocker M, SuUivan M. Bias of ionized calcium results from blood gas syringes. Clin Chem 1994 40 669-70. 

The evolution of carbon dioxide was monitored by gas chromatograph (Hewlett-Packard model 5890) equipped with an HP thermal-conductivity detector and a Hayesep 100-120-mesh packed column (10 m X 3.2 mm). Helium was the carrier gas, and its flow rate was 28 mL/min. In each run, 0.5 mL of the gas mixture in the headspace was withdrawn from the test tube by using a pressure-lock gas syringe and injected into the GC column. The calibration curve was made by acidifying a known amount of potassium bicarbonate in the reaction tube under conditions similar to those of the corresponding experimental conditions. Standard carbon dioxide gas (Supelco) was used to confirm the formation of carbon dioxide. 

NOTE Bake out the syringe between samples. It is easy to contaminate a gas syringe. Place it in the oven and bake it while the sample is heating. Handle it with gloves, so you won t get burned when you take it out. 

Gas volume method. If a gas is produced in the reaction, its volume can be measured at intervals of time. The gas can be collected in a horizontal gas syringe or by bubbling it into an inverted measuring cylinder filled with water. 

The gas s>Tinge method can be used to flnd the molar mass of a liquid with a low boiling point. A small weighed quantity of liquid is injected into a gas syringe. The volume of vapour formed is measured, and its temperature and pressure are noted. From the values of mass and volume, the molar mass can be calculated. 

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