Sample peak height

Perfluoroalkane-225 (PGR, Gainesville, FL) was admitted through a glass inlet system to provide reference peaks. Analytical and reference peaks for the nitrosamines studied are shown in Table I. Sample and reference peaks were scanned alternately at a repetition rate of approximately 1 sec and were monitored on an oscilloscope. When the nitrosamine peak appeared, the oscillographic recorder chart drive was engaged and remained on until the peak disappeared. Nitrosamine quantities were estimated by comparing the sum of sample peak heights measured from the chart (usually 10 to 20 values) with values derived from injection of standard solutions. 

The sample peak height or area was below that obtained for a 0.1-pg/mL standard solution. 

Sample peak area (a) and sample peak height (h )... 

Tabulate the peak height measurements in chart divisions obtained from the digestate and digestate plus standard additions. Subtract the peak height obtained on the blank solution from the sample peak heights. 

First, following the initial conditions, 4% Pharmalyte (pH 3-10), and 0.2 mg/mL sample concentration were tested for this sample. Under the conditions, as shown in the trace 1 of Figure 19.3, the sample peak height is detected at 0.1 Abs. In the next run, the sample concentration was increased to 0.6 mg/mL. The focusing time was 6 min at 600 V/cm with a 1 min prefocusing at 300 V/cm. Two pi markers were spiked into the sample for pi calibration. The results show good reproducibility in peak pattern (traces 2 and 3 in Figure 19.3). Since the separation resolution under these conditions was satisfactory, no further method development was pursued to enhance the resolution. 

To one of the concentrates (EX-1, Figure 118) was added 5 ml of hexane followed by 0.5 ml of lithium aluminium hydride solution. After 2-3 min, the mixture was diluted with hexane, about 0.5 ml of water carefully added, the phases were mixed, and the hexane phase was analyzed by EC-GLC for Ph3SnH,Ph2SnH2, and PhSnH. A standard curve was prepared for each of the hydrides with the ng/yl hexane standard solutions, generally in the 0.2 - to 2.0-ng range. Quantitation was done by comparison of sample peak heights to the standard curve. 

To the third dichlorome thane concentrate (EX-3) was added 1 ml of hexane, the contents were concentrated under nitrogen to about 0.1 ml, and then diluted back to 1.0 ml with hexane. The sample was transferred to a Florisil micro-column (prepared by packing a disposable Pasteur pipet with 0.35 g of 60/100 mesh Florosil held with a small glass wool plug and rinsing with two 5-ml portions of hexane before use) and eluted with hexane. The first 2.5 ml of eluate was collected, concentrated to 0.1-0.5 ml, and analyzed by FID-GLC for tetraphenyltin. Quantitation was accomplished by comparison of sample peak heights to the tetraphenyltin standard curve in the 10-50 ng range. 

Sample Peak heights of molecular ions ( i/z) Peak height ratio of mass 18 to 44 (H2O/CO2)... 

With conventional nonspectroscopic detectors, other methods must be used to identify the solutes. One approach is to spike the sample by adding an aliquot of a suspected analyte and looking for an increase in peak height. Retention times also can be compared with values measured for standards, provided that the operating conditions are identical. Because of the difficulty of exactly matching such conditions, tables of retention times are of limited utility. 

After adding a 10.00-mL portion of the internal standard, the solution was filtered. Analysis of the sample gave a peak height ratio of 23.2 for ASA and 17.9 for CAE. 

The analysis of N03 in aquarium water was carried out by CZE using 104 as an internal standard. A standard solution of 15.0-ppm N03 and 10.0-ppm 104 gives peak heights (arbitrary units) of 95.0 and 100.1, respectively. A sample of water from an aquarium is diluted 1 100, and sufficient internal standard added to make its concentration 10.0 ppm. Analysis gives signals of 29.2 and 105.8 for N03 and 104 , respectively. Report the parts per million of N03 in the sample of aquarium water. 

Of the six parameters shown in Figure 13.18, the most important are peak height and return time. The peak height is related, directly or indirectly, to the analyte s concentration and is used for quantitative work. The sensitivity of the method, therefore, is also determined by the peak height. The return time determines the frequency with which samples maybe injected. Figure 13.19 shows that when a second sample is injected at a time T after injecting the first sample. 

Most flow injection analyses use peak height as the analytical signal. When there is insufficient time for reagents to merge with the sample, the result is a split-peak, or doublet, due to reaction at the sample s leading and trailing edges. This experiment describes how the difference between the peak times can be used for quantitative work. 

Transitions. Samples containing 50 mol % tetrafluoroethylene with ca 92% alternation were quenched in ice water or cooled slowly from the melt to minimise or maximize crystallinity, respectively (19). Internal motions were studied by dynamic mechanical and dielectric measurements, and by nuclear magnetic resonance. The dynamic mechanical behavior showed that the CC relaxation occurs at 110°C in the quenched sample in the slowly cooled sample it is shifted to 135°C. The P relaxation appears near —25°C. The y relaxation at — 120°C in the quenched sample is reduced in peak height in the slowly cooled sample and shifted to a slightly higher temperature. The CC and y relaxations reflect motions in the amorphous regions, whereas the P relaxation occurs in the crystalline regions. The y relaxation at — 120°C in dynamic mechanical measurements at 1 H2 appears at —35°C in dielectric measurements at 10 H2. The temperature of the CC relaxation varies from 145°C at 100 H2 to 170°C at 10 H2. In the mechanical measurement, it is 110°C. There is no evidence for relaxation in the dielectric data. 

The solvent used was 5 %v/v ethyl acetate in n-hexane at a flow rate of 0.5 ml/min. Each solute was dissolved in the mobile phase at a concentration appropriate to its extinction coefficient. Each determination was carried out in triplicate and, if any individual measurement differed by more than 3% from either or both replicates, then further replicate samples were injected. All peaks were symmetrical (i.e., the asymmetry ratio was less than 1.1). The efficiency of each solute peak was taken as four times the square of the ratio of the retention time in seconds to the peak width in seconds measured at 0.6065 of the peak height. The diffusivities obtained for 69 different solutes are included with other physical and chromatographic properties in table 1. The diffusivity values are included here as they can be useful in many theoretical studies and there is a dearth of such data available in the literature (particularly for the type of solutes and solvents commonly used in LC separations). 

To demonstrate the effect in more detail a series of experiments was carried out similar to that of volume overload, but in this case, the sample mass was increased in small increments. The retention distance of the front and the back of each peak was measured at the nominal points of inflection (0.6065 of the peak height) and the curves relating the retention data produced to the mass of sample added are shown in Figure 7. In Figure 7 the change in retention time with sample load is more obvious the maximum effect was to reduce the retention time of anthracene and the minimum effect was to the overloaded solute itself, benzene. Despite the reduction in retention time, the band width of anthracene is still little effected by the overloaded benzene. There is, however, a significant increase in the width of the naphthalene peak which... 

The quantitative determination of a component in gas chromatography using differential-type detectors of the type previously described is based upon meas urement of the recorded peak area or peak height the latter is more suitable in the case of small peaks, or peaks with narrow band width. In order that these quantities may be related to the amount of solute in the sample two conditions must prevail ... 

Start the vapour generator cycle so that the absorption cell is flushed with argon gas and the pre-set volume of NaBH4 (1 mL) is pumped into the sample vessel. After the pre-selected reaction time (0.5 minute), AsH3 vapour is flushed into the absorption tube. Record the value of each arsenic signal as a peak height measurement. Read off the arsenic concentration of the sample, which is displayed on the instrument video screen. 

Quantitative estimates of the mass of a particular solute present in a sample are obtained from either peak height or peak area measurements. The values obtained are then compared with the peak height or area of a reference solute present in the sample at a known concentration or mass. In this chapter quantitative analysis by LC will be discussed but the procedures described should not be considered as entirely appropriate for other types of chromatographic analysis. Those interested in general quantitative chromatographic analysis including GC and TLC are referred to the book by Katz (4). 

There are two basic methods used in quantitative analysis one uses a reference standard with which the peak areas (peak heights) of the other solutes in the sample are compared the other is a normalization procedure where the area (height) of any one peak is expressed as a percentage of the total area (heights) of all the peaks. There are certain circumstances where each method is advantageous, and providing they are used carefully and appropriately all give approximately the same accuracy and precision. 

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