Volatile calibration curves

Optical counters allow relatively rapid measurements of the size distribution and, unlike some of the other methods of size fractionation, include volatile particles in the measurement. However, some care must be taken in interpreting the detailed shape of the size distribution spectrum because of some anomalies that have been observed for example, around the l-/xm region, interference from light that is reflected or refracted from the front and back of the particle gives a knee in many calibration curves of number of particles versus their diameter (LBL, 1979). 

Each solvent investigated is quantified in the same manner using their respective calibration curve and formula. Because an absolute calibration is used, sample analysis and calibration must be performed on the same day. Standards more than one day old should be scrutinized for variations in concentration due to volatilization of solvent from the carbon disulfide into the head space. 

Calculate the area(s) under the peak for each volatile organic compound, and convert it to milligrams per kilograms of gamma-Cyclodextrin using the response factor for 8-cyclo-hexadecen-l-one. The response factor is determined from a calibration curve using 8-cyclohexadecen-l-one concentrations of 0.1 to 6 mg/100 mL of hexane. 

The quantification is based on multi level response factors covering both differences in extraction behaviour, volatility and GC/MS response of the compounds and of the deuterated internal standards. 1 Utre pentane washed water is spiked with 50 pg deuterated internal standards and normally 1,5,25 and 100 pg of the different target compounds. Calibration curves are automatically calculated and stored on the disk, and quantification is based on area of ion chromatogram of one specific mass for each compoimd. 

Many qualitative and comparative studies of volatiles in wines by HS-SPME were preformed (Favretto et al., 1998 Marengo et al., 2001 Vas et al., 1998 Begala et al., 2002 Demyttenaere et al., 2003 Rocha et al.,2006).The calibration curves of the common volatiles in wines can be calculated because of standards that are commercially available and the method is suitable for quantitative analyses. Alternatively, quantitative GC/MS can be performed by using deuterated standards, for... 

Recoveries also depend on the wine matrix white and red wines differ for volatiles and polyphenols, and contents of alcohol and sugars. For quantitative analysis, internal standards have to be spiked to the sample in suitable concentration, such as dimethyl sulfide-d6 (d6-DMS) 25 pg/L, dipropyl disulfide (DPDS) 25 pg/L, 4-methylthiazole (MT) lOpg/L, and 3-(methylthio)-l-hexanol (MTH) 50pg/L. A white wine matrix can be used [e.g., 10% v/v ethanol, sugar content <4g/L, and a polyphenolic content of 115mg/L expressed as (+)-catechin] for preparation of standard solutions to calculate the calibration curve for analytes, containing total S02 corrected to 100 g/L and previously treated twice with charcoal 3 g/L to remove sulfur and less polar volatile compounds (higher alcohols are not removed). 

Free yeast cells were introduced into the flow system together with glucose and the volatile products carbon dioxide and ethanol were analyzed. In this way a linear calibration curve... 

When the calibration curves were compared, several compounds at the low end of the calibrated concentration range were affected by components already present in the diesel/oil extract. For example, low-levels of some PNAs and phthalates, present naturally in these refined petroleum products, were detected in the unspiked diesel/oil extract. Also, some of the phenols in this dirty matrix were reactive in the injection liner indeed, the matrix itself can passivate the liner for some target compounds. Passivation in this sense means that the liner surface becomes coated with non-volatile components, forming a barrier between the analyte and the bare, more reactive glass surface. While this issue is not related to ion trap mass spectrometry per se, it will be present in any analytical GC/MS system. As illustrated in the example below, calibration curve linearity (as represented by relative percent standard deviation, or RSDs, of the relative response factor at each calibration concentration level) and correlation coefficients for most compounds in the pure solvent were identical statistically to those prepared in the 3000 ppm diesel/oil matrix spikes, as are shown in Figures 15.36 and 15.37. 

A simple method was employed to prepare a base wine for constructing a calibration curve for the quantification of the reductive sulfur compounds. Deodourisation of the base wine was carried out in order to remove the volatile sulfur compounds as much as possible, along with other volatile compwimds, while retaining further components of the wine to obtain a matrix effect similar to that of a wine sample. 

Fig. 135 shows the calibration curves of various highly volatile halo-... 

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