Injection standard

In a quantitative flow injection analysis a calibration curve is determined by injecting standard samples containing known concentrations of analyte. The format of the caK-bration curve, such as absorbance versus concentration, is determined by the method of detection. CaKbration curves for standard spectroscopic and electrochemical methods were discussed in Chapters 10 and 11 and are not considered further in this chapter. 

Fig. 10. Response of an ammonium ion-selective electrode which was made from nonactin dissolved in a PVC membrane mounted in a Phillips electrode body (ISE-561, Glasblaserie Mitller, Zurich) referenced against an SCE to a spHt-stream EIA system, (a) EIA response to injected standards containing both glutamine and ammonium chloride lines A—E contain both glutamine and ammonium chloride E—G contain only glutamine, (b) Strip-chart...

FIGURE 7.13 Preparative separation of various proteins on Fractogel EMD BioSEC (S). The length of the column was 1000 mm and the inner diameter 100 mm. The flow rate was 6.2 ml/min with 20 sodium phosphate buffer (pH 7.2) containing 0.3 M NaCI as the eluent. The injected standard proteins can be used to create a calibration curve. 

An equation representing area versus concentration was determined using a standard linear regression analysis applied to the injection standards, yielding a slope m and an intercept b. The following equation was then used to calculate the concentration of the sample injected from the area measured ... 

No correction for molecular weights was necessary for the derivatized compounds since the injection standards were derivatized simultaneously with the analytes and all weights were based on the underivatized acids. 

The injection standards of carfentrazone-ethyl must be in acetonitrile. Other solvents (e.g., ethyl acetate) lead to poor chromatography following injection of matrix samples. This can lead to apparent enhanced recoveries of analyte in the fortified samples. 

No correction for molecular weights was necessary for derivatized HMS, because the injection standards were derivatized simultaneously with the samples. However, a correction factor was needed for calculating the recovered amount of SCA since the SCA was quantitated as DMS. The correction factor (molecular weight ratio) between SCA and DMS was 1.12 (417/373 417 = molecular weight of SCA and 373 = molecular weight of DMS). To calculate the amount of SCA, use the above equation, which will yield DMS (ng), then multiply that value by 1.12 to convert to nanograms of SCA. 

Optimizing the GC instrument is crucial for the quantitation of sulfentrazone and its metabolites. Before actual analysis, the temperatures, gas flow rates, and the glass insert liner should be optimized. The injection standards must have a low relative standard deviation (<15%) and the calibration standards must have a correlation coefficient of at least 0.99. Before injection of the analysis set, the column should be conditioned with a sample matrix. This can be done by injecting a matrix sample extract several times before the standard, repeating this conditioning until the injection standard gives a reproducible response and provides adequate sensitivity. 

Quantitation is performed by the calibration technique. Construct a new calibration curve with thenylchlor standard solutions for each set of analyses. The thenylchlor peak usually appears at a retention time around 4.5 min. Plot the peak area against the injected amount of thenylchlor. The injection volume (2 pL) should be kept constant as the peak area varies with the injection volume with NPD. Before injecting the sample solutions, check the stability of sensitivity of the GC system by injecting more than one standard solution containing ca 0.05-2 ng of thenylchlor. Recommendation inject standard solutions and sample solutions alternately rather than constructing the calibration curve in advance. 

Recommendation Inject standard solutions (0.2, 0.4, 0.6, 0.8 and 1.0 igmL in acetone) and sample solutions alternately rather than constructing the calibration curve in advance. 

Injection Production Sample Injection Standard Solution ... 

Regarding relevance, the spectral miscibility of the data obtained from these two different sources can be readily observed by doing a PCA analysis of the combined spectral data. The scatter plot of the first two PC scores obtained from PCA of such a data set for one of the process analytes is shown in Figure 12.31a. Note that there is considerable common space for the two data sources in the PC1/PC2 space, and there are some regions of this space where only samples from the old calibration strategy lie. A similar pattern is observed in the later PCs of this model. This result indicates that the on-line spectra contain some unique information, but that the on-line and injected-standard spectra are generally quite similar. 

Inject standard sterol mixture (see Reagents and Standards ) to confirm the retention times of the various sterols. 

Inject standard sterol mixture (see Reagents and Standards ). 

An external standardisation method is employed to perform quantitative analysis. In the cited study, calibration curves for each compound are obtained by injecting amounts ranging from 0.08 to 10 nmol. The amount of injected standards is logarithmically proportional to the peak area. 

Inject standard solutions (usually 25 pi) and analyze using mobile phase at a flow rate of 1.5 ml/min for normal phase or 1.0 ml/min for reversed phase. 

Inject standards in duplicate, record peak shapes for each acid component, and integrate results. 

Steam sterilization is the method mostly used to sterilize freeze-dryers. High-quality, ultra-pure steam (water for injection standard USP XXII or PhEur equivalent) is used to achieve a minimum exposure of 121 °C for 30 min or the equivalent temperature-time combination for effective sterilization (Table 2.4.1). This method is easy to validate and is recommended by regulatory authorities as being reliable. The definition of sterilization is a validated process used to render a product surface free of all forms of viable micro-organisms (EN 556-1 2001). According to the authorities, a product or surface is only sterile when a validated sterilization process has been applied (EN 550, EN 552, EN 554, EN ISO 14160 and EN ISO 14937). 

Repeat standards run. Increase recorder speed to 2cm/min. Inject standards solution. Record the four-peak chromatogram. 

A standard calibration curve is constructed by injecting standards or samples of known molecular weight (most likely molecular weight at a peak retention volume), as shown in Figure 7.13a. 

An example of a calibration curve for Cd with a Zeeman electrothermal atomization atomic absorption spectrometry (ET-AAS) is presented in Figure 6.1. A simple linear regression model is fitted through the data points. The response of the ET-AAS is placed on the ordinate and the concentration of the injected standard solutions on the abscissa. The concentration of the unknown samples can be calculated back as X = (Yt — a)/b. 

A method which circumvents the problem of total elution is to have an absolute measure of an injected standard or of one product and use this for the quantitative estimation of the other products and undecomposed reactants. For instance, in the HCl-catalysed decomposition of di-terr.-butyl peroxide , involving the reactions... 

Always inject standards at the beginning of a run to ensure that the column has equilibrated with the mobile-phase. (This will also check that you have made up the mobile-phase correctly.)... 

Figure 2. Capillary GC-ECD traces of FL and HU fractions of samples NB(0-3) and NB(29-31). Peak a is pentachlorophenol (as methyl ether derivative) the remaining peaks are PCB s. STD -co-injection standard, decachloroblphenyl. Approximate elution ranges of di- through decachloroblphenyl are delineated.

Figure 3. Capillary GC-FID traces of saturated hydrocarbons in FL and HU fractions of sample LA. STD - co-injection standard, perdeuterated tetracosane IS - Internal standard, -terphenyl UCM - unresolved complex mixture. Chain lengths of odd-numbered n-alkanes are denoted.

Another approach to measuring protein concentration in the solution phase is the use of chromatographic methods, such as size exclusion or reverse phase HPLC. The peak area of a given injected volume of a protein solution is converted to protein amount using a standard curve that is generated by plotting peak area versus amount of injected standard. This approach is necessary in the rare event that a protein has few aromatic residues that are required for the 280 nm absorbance signal. Protein concentration in solution could also be determined... 

I.P.A. Moraes, M.R.S. Souto, A.O.S.S. Rangel, Sequential injection standard addition system with a mixing chamber determination of orthophosphate in waters, J. Flow Injection Anal. 20 (2003) 187. 

Gradient dilution [275, 338], which was first described and used in 1982 [264, 338], is based on the selection of a suitable element of the dispersed sample zone to become the source of the analytical readout. This is done by selecting a time delay (e.g., 10, 12, 14, 16, or 18 s), elapsed from the point of injection 5, as illustrated in Fig. 2.18, right. Since the selected elements of the dispersed sample zone have different dispersion coefficients (Di, D2, I>3,. . . , Fig. 2.18, left), which yield, for a series of injected standard solutions, a sequence of corresponding calibration curves with decreasing slopes, the sensitivity of measurement can be... 

Figure 2.20. The principle of gradient calibration, showing on the left-hand side a conventional calibration run where standards covering 25%, 50%, 75%, and 100% of the range were injected each in triplicate, and on the right-hand side a single injection of the 100% standard, which was recorded at a high chart speed. Via a conventional calibration line (r = 1000), delay times t, t2, ts, and t4 are then identified, corresponding to known levels of originally injected standards.

Figure 4.73. The pH responses of the optosensor furnished with the following immobilized indicators Universal (Merck 9535), Spezial (Merck 9547), and Spezial (Merck 9543), recorded by injecting standard buffer solutions into a 5 x 10" M HCl carrier stream and monitoring the reflectance as increased absorbance (Ar) at 610 nm. The arrow at the far right indicates the pH range investigated for clinical applications.

Figure 6.3. (a) FIA manifold for spectrophotometric determination of phosphate. The two reagents are premixed in the first coil, whereupon sample is injected (30 ixL). All tubes are 0.5 mm ID. (b) Left record obtained by injecting standards in quadruplicate, containing 5-40 ppm P-PO4 the record to the right shows a scan where the time scale is expanded to show the peak shape when injecting 20 and 40 ppm solutions. Note that it takes only 15 s between sample injection 5 and peak maximum readout / , and another 15 s until the next sample (52) can be injected. Hence, the signal will be below the 1% level before the next readout will be taken, and therefore there is no carryover even at a rate of 120 samples/h. 

There are three approaches for process control applications utilizing peak height (or vertical readout) as the source of information. They are based on sample injection, standard injection, and reagent injection. 

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