Detection charged aerosol

The CAD detection principle has some commonality with atmospheric-pressure chemical ionization (APCI) in mass spectrometry. However, CAD 

Charged aerosol detection is nonlinear as the amount of analyte being measured depends on the charge that can be placed on the surface of the particle. 

in turn, is dependent upon the volume of the particle being formed. The relationship between particle surface area and volume is not linear. This is observed experimentally as the response curves for the Corona charged aerosol detector are typically expressed as the second-order polynomial function over a range of up to four orders of magnitude. However, over a narrow concentration range, good linearity of the CAD response is observed with sufficient accuracy. The application of power function can now correct for this physical characteristic and deliver a more linear response over a larger dynamic 

The use of a large PFV can give the appearance of linearity over a wide dynamic range, but it is always important to understand how each point is weighted over the entire range. It should be pointed out that with any curve over two orders of magnitude, the points at the top of the curve will have a 

Like ELSD, CAD has been applied for the analysis of nonvolatile neutral, acidic, basic, and zwitterionic compounds, both polar and nonpolar. Compound classes include amino acids, fatty acids, carbohydrates, lipids, proteins, steroids, surfactants, and other compounds with weak or no chromophores used in the pharmaceutical, food, chemical, and consumer products industries. Some applications involving ionic and polar species are described below. 

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Figure 15.5 Instrument schematic of the CAD (charged aerosol detection). (Reproduced...

Tadeusz G, Frederic L, Roman S, Pat S. 2006. Universal response in liquid chromatography using charged aerosol detection. Anal. Chem. 78 3186-3192. 

The physical quality of samples is assessed via analytical methods. Liquid chromatography with mass spectrometry (LC-MS) is the most common instrumentation used to determine sample presence and purity (Kerns et al., 2005). Chemiluminescent nitrogen detection (CLND), charged aerosol detection (CAD) and other techniques have also been used to determine concentration (Popa-Burke et al., 2004 Gamache et al., 2003). 

Gamache, P.H. et al. 2003. HPLC analysis of nonvolatile analytes using charged aerosol detection. LC/GC N. Am. 23, 150-155. 

Additional detection techniques that can be employed to help solve mass balance issues with RP-HPLC are MS [30], chemiluminescent nitrogen-specihc detector [31], evaporative light-scattering detector, ELSD [32], and corona charged aerosol detection [CAD] [33],... 

Figure 23-4 Simultaneous separation of anions and cations on a ZIC-HILIC zwitterionic stationary phase with charged aerosol detection. The 150 X 4.6-mm column with S-jim-diameter stationary phase was eluted with a gradient of 20-70% B over 26 min at a flow rate of 0.5 mL/min at 30°C. Solvent A 15 vol% 100 mM ammonium acetate (pH 4.68) in water, 5% methanol, 20% 2-propanol, 60% acetonitrile.

Detection methods applied in ion chromatography are divided into electrochemical, spectrometric, nebulization, and others. Conductometric, amperometric, and charge detection are electrochemical methods, while the spectrometric methods include UV/Vis, fluorescence, and refractive index detection. In addition, there are various application forms of these detection methods. Nebulization methods include evaporative light scattering (ELS) and charged aerosol detection (CAD). All of these methods are described in detail in this chapter. 

Figure 8.71 Illustration of the power transformation of a polynomial calibration function to a linear one for charged aerosol detection.

Figure 8.73 Signal increase in gradient mode with charged aerosol detection. Separator column Acclaim PA2,2.2 pm column dimensions 50 mm X 2.1 mm i.d. column temperature 45 °C eluent (A) 98 2 (v/v) MeCN/20 mmol/L ammonium acetate (pH 45)...

Figure 8.74 Solvent compensation without a second delay column in an inverse gradient setup for charged aerosol detection.

In addition to formulation analysis, CAD can also be used for other types of ion analysis. Zhang et al. developed a method for the simultaneous determination of 25 inorganic and organic anions and cations that are commonly used as coimterions, using Acclaim Trinity PI (3 pm) and charged aerosol detection [141]. The method is capable of determining the content of sodium, chloride, and fumarate in different drug substances. Limits of detection between 5 ng on coliunn for sodiimi and 400 ng on column for lactate were achieved. 

Figure 8.78 Separation of aii gentamicin sui-fate congeners and reiated substances on a 2.2 pm Acclaim PA2 coiumn with charged aerosol detection. Column dimensions ...

Figure 8.79 Separation of streptomycin suifate 20 mmoi/L pentafiuoropropionic acid/acetone and various impurities on a 3 pm YMC-Pack flow rate O mtymin detection Corona CAD Pro C18 with charged aerosol detection. Coi- injection voiume lOpL sampie 5mg/mL umn dimensions 250mmx4.6mm i.d. coi- streptomycin suifate peaks (1-16) impurities, umn temperature 40 °C eluent 99 1 (v/v) (17) streptomycin, and (18-22) impurities.

Jia et al. employed charged aerosol detection for the analysis of antidiabetic drugs such as glipizide, gliclazide, glibenclamide, and glimepiride that are commonly used in the treatment of tj pe II diabetes [155],... 

A 5 pm GraceSmart C18 column (250 mm x 4.6 mm i.d.) was used for the iso-cratic separation of these drugs with an eluent consisting of 38 62 (v/v) formic acid in water/acetonitrile. Among the tested additives, 0.1% formic acid yielded the best peak shapes. The analysis of the four antidiabetic drugs could be conducted in less than 8 min. In their study, Jia et al. [155] also compared charged aerosol detection with UV and ELSD in order to evaluate performance parameters such as linearity, accuracy, precision, and limit of detection. As a result. 

Figure 8.80 Separation of underivatized amino acids on a 2.2 pm Acclaim PA2 with charged aerosol detection. Column dimensions 250 mm x 2.2 mm i.d. column temperature 20 °C eluent (A) 0.4% heptafluorobutyric acid -1-0.02% TFA in water and (B) 0.1% TFA in MeCN 1% B for 1 min isocratic, to 5% B in 2 min, and then to 40% B in 7 min flow rate ...

In recent years, charged aerosol detection is increasingly used for the detection of carbohydrates if the high sensitivity of IPAD in combination with anion-exchange chromatography using high pH mobile phases is not required (see Section 3.10). With... 

Hydrophilic interaction liquid chromatography in gradient mode with charged aerosol detection can also be used for separating oligosaccharides. As an example, Figure 8.83 shows the separation of maltose oligomers up to DP7 on... 

Figure 8.82 Carbohydrate analysis in apple juice using charged aerosol detection. Column Shodex Asaipak NH2P-50 4E, 3 pm column dimensions 250 mm x 3 mm i.d. column temperature 60°C eluent MeCN/water (92 8 v/v) flow rate 0.8 mL/min detection charge...

Figure 8.83 Separation of oligosaccharides using gradient HILIC and charged aerosol detection. Column Shodex Asaipak NH2P-5O 4E, 5 (im column dimensions 250 mm x 4.6 mm i.d. column temperature 35 °C eluent (A) MeCN and (B) water gradient 70% A to...

A in 40 min flow rate 1 mL/min detection charged aerosol detection injection volume lOpL peaks 200ng glucose (1), maltose (2), maltotriose (3), maltotetraose (4), malto-pentaose (5), maltohexaose (6), and maltohep-taose (7). 

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