Fixed volume sampling

Fig. 2.6 Centrifugal fixed volume sampling and transfer in the GeMSAEC automatic colorimeter.

Fig. 2.7 The GeMSAEC automatic colorimeter siphon method of fixed volume sampling and transfer. Reproduced with permission of Anderson [12],...

Be sure samples are consistent. For fixed volume sample loop, use 2-3 times loop volume to ensure loop is completely filled. Be sure automatic sampler vials contain sufficient sample. Check syringe-type injectors for air. In systems with wash or flushing step, be sure wash solution does not precipitate sample components. 

A MINICAMS is an automatic, near-real-time continuous air monitoring system using gas chromatography and sample collection with a solid-adsorbent preconcentrator or fixed-volume sample loop. The MINICAMS... 

The majority of injection systems are only capable of delivering a fixed-volume sample plug into the analysis channel and are limited in... 

Traditionally, the design of the injection channel has always been in the form of a cross. A limitation of this configuration is that it is only capable of providing discrete, fixed-volume samples. However, some applications require the delivery of different sample volumes to the detection and separation processes. The unique multi-T configuration injection system [3] has the ability to simulate the functions of the cross, double-T, and triple-T systems through appropriate manipulations of the electric field within its various channels. Figure 7 shows the experimental and numerical simulation results of the proposed multi-T form injection system. 

Fixed-volume sampling is more accurate when the water is subsampled into calibrated reaction bottles as, e.g., for oxygen, and excess sample water is then displaced by reagent addition. This procedure considerably reduces the contamination risk and generally improves the determination of ammonia. 

The majority of injection systems are only capable of delivering a fixed-volume sample plug into the analysis channel and are limited in function by their configuration. Fu and his co-workers have proposed the multifunction injection system and a variable-volume-injection system within the microfluidic chip as described below. 

FIGURE 5.1 Plumbing arrangement for introduction of gaseous samples into the ICP, using either a fixed-volume sample loop or syringe. 

Any curved line indicates the fixed volume sample loop is too large. A smaller loop size should replace the fixed volume loop and 6.1.1 through 6.1.4 should be repeated (see Fig. 9). 

A2.1.2 The m or component of interest (methane for natural gas) is charged to the chromatograph by means of the fixed-size sample loop at partial pressure of 100 to 700 mm of Hg in increments of 100 mm. The peak area of the methane is plotted versus partial pressure. Any deviation from linearity indicates the fixed volume sample loop is too large. The sample size should be reduced until the pure m or component is linear over the concentration range expected in the samples. 

Wang and Taha described an interesting application of potentiometry called batch injection. As shown in the following figure, an ion-selective electrode is placed in an inverted position in a large-volume tank, and a fixed volume of a sample or standard solution is injected toward the electrode s surface using a micropipet. 

Quantitative Calculations Quantitative analyses are often easier to conduct with HPLC than GC because injections are made with a fixed-volume injection loop instead of a syringe. As a result, variations in the amount of injected sample are minimized, and quantitative measurements can be made using external standards and a normal calibration curve. 

The procedure can be readily extended to multicomponent systems by applying the test to each component in turn. In real systems, it is generally convenient to take samples of fixed volume or mass rather than fixed number of particles. In such cases, the expected variance can be computed using (see Refs. 19 and 20)... 

Both procedures measure the time for a fixed volume of the sample to flow though a calibrated tube at a controlled temperature. 

The ideal gas law offers a simple approach to the experimental determination of the molar mass of a gas. Indeed, this approach can be applied to volatile liquids like acetone (Example 5.4). All you need to know is the mass of a sample confined to a container of fixed volume at a particular temperature and pressure. 

The introduction of the sample into the adsorbent layer is a critical process in HPTLC. For most quantitative work a platinum-iridium capillary of fixed volume (100 or 200 nL), sealed into a glass support capillary of larger bore, provides a convenient spotting device. The capillary tip is polished to provide a smooth, planar surface of small area (ca 0.05 mm2), which when used with a mechanical applicator minimises damage to the surface of the plate spotting by manual procedures invariably damages the surface. 

A similar expression summarizes the linear variation in pressure of a sample of gas when it is heated in a container of fixed volume. The pressure is found experimentally to extrapolate to zero pressure at —273.15°C (Fig. 4.12). Therefore, an alternative version of Charles s law is... 

However, some undetermined factor produces a negative bias, particularly in samples nos. 3, 6, 9, and 10 this points to either improper handling of the fixed-volume dispenser, or clogging. The reduction of the within-group variance from VVV to VWV is, to a major part, due to the elimination of... 

For most quantitative work in TLC the sample is applied to the layer using a fixed-volume dosimeter comprising a platinua-iridium capillary of 100 or 200 nl volume, sealed into a glass. . support capillary of larger bore [6]. The capillary tip is... 

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