Chromatographic calibration

Guillemin, C. L., Calibrating chromatographs on-line. Deferred standard method, Instrum. Technol., 22(4), 43, 1975. 

Table 4.45 shows the main features of SEC. This technique has become an indispensable tool for polymer characterisation. SEC has some advantages over other LC methods, such as the predictability of the end of a chromatographic run and of the retention times in a calibrated chromatographic system. SEC is an attractive technique for prefractionation or sample clean-up prior to a more sensitive RPLC technique. This intermediate step is especially interesting for experimental purposes whenever polymer matrix interference cannot be separated from the peak of interest [647]. Disadvantages are that the whole separation must be eluted within the... 

Figure 9 shows MRD profiles for acetone protons in calibrated chromatographic porous glasses (65). The field dependence consists of two logarithmic... 

Calibration Chromatograph successive 2- to 5-p.L portions of the Standard Preparation until the relative response factor, F, is constant (i.e., within a range of approximately 2%)... 

Calibration Chromatograph successive 2- to 5-p.L portions of each Standard Preparation until the relative response factor, F, for each is constant (i.e., within a range of approximately 2%) for three consecutive injections. If using graphic integration, adjust the instrument to obtain at least 70% maximum recorder response for the hexadecyl hexadecanoate peak. Measure the areas under the first (a-tocopheryl propionate) and second (hexadecyl hexadecanoate) major peaks (excluding the solvent peak), and record the values as and Ah respectively. Calculate F for each concentration of Standard Preparation by the formula... 

The 2D experiment yielded separation with respect to functionality and molar mass, and FTD and MMD could be determined quantitatively. For calculating FTD, the relative concentration of each functionality fraction must be determined. These concentrations are equivalent to the volume of each peak in the contour plot. With the appropriate software this can be done easily. Determination of the MMD for each fraction was possible after calibrating chromatograph... 

Both preparative and analytical GPC were employed to analyze a standard (NBS 706) polystyrene sample. Fractions were collected from the preparative column, the solvent was evaporated away, and the weight of each polymer fraction was obtained. The molecular weights of each fraction were obtained usmg an analytical gel permeation chromatograph calibrated in terms of both and M. The following data were obtained ... 

Quantitative mass spectrometry, also used for pharmaceutical appHcations, involves the use of isotopicaHy labeled internal standards for method calibration and the calculation of percent recoveries (9). Maximum sensitivity is obtained when the mass spectrometer is set to monitor only a few ions, which are characteristic of the target compounds to be quantified, a procedure known as the selected ion monitoring mode (sim). When chlorinated species are to be detected, then two ions from the isotopic envelope can be monitored, and confirmation of the target compound can be based not only on the gc retention time and the mass, but on the ratio of the two ion abundances being close to the theoretically expected value. The spectrometer cycles through the ions in the shortest possible time. This avoids compromising the chromatographic resolution of the gc, because even after extraction the sample contains many compounds in addition to the analyte. To increase sensitivity, some methods use sample concentration techniques. 

The highest purity (>99.99%) oxygen is obtained through further refinement. At 99.99% the impurities total only 100 ppm. This grade of oxygen is used in the manufacture of electronic components, fiber optics (qv), etc, or for gas chromatograph calibration or research appHcations. 

The main problem of determination of molecular weight distribution (MWD) of dextrans (polysachaiides which ai e used as active substances for infusion medicines) is low robustness of the existing method. It means that obtained results are strongly dependent on controlled and uncontrolled pai ameters of chromatographic system standai d substances for calibration loading on columns etc. It has been shoved on practical examples. 

Methods which ai e described in Phamiacopoeias (American, British, and European) ai e based on using narrow standai ds for calibration and broad standai d for system suitability test. Prescribed limits of system suitability ar e broad and therefore it may cause large uncertainty of results. But on the other side results ar e strongly influenced by par ameters of chromatographic system. 

The preliminary precipitation of proteins from milk is realized through the addition of solutions of acetic acid (1,7 mol/1) and sodium acetate (lmol/1) at t = 40-45°C before chromatographic isolation of OxTC. The precipitated proteins are separated by filtration. OxTC is detenuined in filtrate after its isolation on chromatographic column. Contents of OxTC was determined on calibration curve which is linear within concentration range 0,01-1,0 p.g/ml. 

The following polyvitamin prepai ations were analyzed Kal tsid (OAO Comfort Plus , Russia), Asvitol (OAO INC Marbiofarm , Russia), Pikovit (KRKA, d.d. The New Place, Slovenia), Yeast with vitamin C (000 EKKO Plus , Russia). Chromatographic experiment has been carried out using Silufol UV-254 (Kavalier, Czech Republic) and acetone - ethyl acetate - acetic acid - ethanol (3 5 1 1) - CTAB (2T0 M) as a mobile phase mixture. The linearity calibration plot, built in coordinate S = f (IgqAC), is valid in the interval 5-25 p.g. Correctness of the determination has been checked by photometry. The obtained results for the ascorbic acid determination are presented below. 

Provide for calibration without using calibration gas. It is surprising how few people realize that a process chromatograph can be calibrated using only the process stream itself. In fact, this method can even prove to be more accurate than using a calibration gas. The chromatograph must have two features to use the method ... 

Avoid chromatographs requiring mixed carrier gas. Mixed carrier gas can introduce as many inherent accuracy problems as calibration gas, maybe more. There is almost always a way to avoid using mixed carrier gas. Find a way even if it is more expensive. 

This, on the one hand, reduces the detection limit so that less sample has to be applied and, thus, the amounts of interfering substanees are reduced. On the other hand, the linearity of the calibration curves can also be increased and, hence, fewer standards need to be applied and scanned in routine quantitative investigations so that more tracks are made available for sample separations. However, the introduction of a large molecular group can lead to the equalization of the chromatographic properties. 

Eigure 3.3 shows the calibration plots for Zorbax PSM columns. (The calibration plots for silanized and unsilanized columns are comparable.) These calibration plots allow the chromatographer to select the appropriate columns for samples. Eor example, the Zorbax PSM 60 column provides resolution of... 

The range of pore sizes in which TSK-GEL PW and TSK-GEL PWxi columns are available permits a wide spectrum of water-soluble substances to be analyzed. Calibration curves for polyethylene glycols chromatographed on... 

All packing materials produced at PSS are tested for all relevant properties. This includes physical tests (e.g., pressure stability, temperature stability, permeability, particle size distribution, porosity) as well as chromatographic tests using packed columns (plate count, resolution, peak symmetry, calibration curves). PSS uses inverse SEC methodology (26,27) to determine chromatographic-active sorbent properties such as surface area, pore volume, average pore size, and pore size distribution. Table 9.10 shows details on inverse SEC tests on PSS SDV sorbent as an example. Pig. 9.10 shows the dependence... 

Microlitre syringe pipettes are available with capacities ranging from 10 to 250 ph and with the body of the pipette calibrated. When fitted with a needle tip they are particularly useful for introducing liquids into gas chromatographs (Chapter 9). 

The procedure comprises the addition of a constant amount of internal standard to a fixed volume of several synthetic mixtures which contain varying known amounts of the component to be determined. The resulting mixtures are chromatographed and a calibration curve is constructed of the percentage of component in the mixtures against the ratio of component peak area/standard peak area. The analysis of the unknown mixture is carried out by addition of the same amount of internal standard to the specified volume of the mixture from the observed ratio of peak areas the solute concentration is read off using the calibration curve. 

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