Liquid chromatography sampling methods

Lab method using glass-fibre/Tenax tube sampling and high performance liquid chromatography Field method using acid hydrolysis, diazotization, coupling and spectrophotometry... 

Improved high-pressure liquid chromatography (HPLC) methods have been developed for the analysis of quaternary salt type corrosion inhibitors in brine waters [400]. However, these methods are not suitable for imidazolines and amido-amines. A method based on fluorescence detection has been described for the quantitative analysis of the imidazoline- and amido-amine-type corrosion inhibitors in both oil field water and crude oil samples by HPLC [1174]. 

Raman often is evaluated as an alternative to an existing high performance liquid chromatography (HPLC) method because of its potential to be noninvasive, fast, simple to perform, and solvent-free. Raman was compared to HPLC for the determination of ticlopidine-hydrochloride (TCL) [43], risperidone [44] in film-coated tablets, and medroxyprogesterone acetate (MPA) in 150-mg/mL suspensions (DepoProvera, Pfizer) [45] it was found to have numerous advantages and performance suitable to replace HPLC. In an off-line laboratory study, the relative standard deviation of the measurement of the composition of powder mixtures of two sulfonamides, sulfathiazole and sulfanilamide, was reduced from 10-20% to less than 4% by employing a reusable, easily prepared rotating sample cell [46]. 

Cinnamyl anthranilate can be assayed by a method based on ester hydrolysis. Bulk samples of food-grade cinnamyl anthranilate have been analysed for purity by thin-layer chromatography and high-performance liquid chromatography. A method has been described for determining the content of this compound in food products by steam distillation followed by paper chromatography and examination under ultraviolet light it has a limit of detection of 1 pg (lARC, 1983). 

Currently, high-performance liquid chromatography (HPLC) methods have been widely used in the analysis of tocopherols and tocotrienols in food and nutrition areas. Each form of tocopherol and tocotrienol can be separated and quantified individually using HPLC with either a UV or fluorescence detector. The interferences are largely reduced after separation by HPLC. Therefore, the sensitivity and specificity of HPLC methods are much higher than those obtained with the colorimetric, polarimetric, and GC methods. Also, sample preparation in the HPLC methods is simpler and more efficiently duplicated than in the older methods. Many HPLC methods for the quantification of tocopherols and tocotrienols in various foods and biological samples have been reported. Method number 992.03 of the AOAC International Official Methods of Analysis provides an HPLC method to determine vitamin E in milk-based infant formula. It could probably be said that HPLC methods have become dominant in the analysis of tocopherols and tocotrienols. Therefore, the analytical protocols for tocopherols and tocotrienols in this unit are focused on HPLC methods. Normal and reversed-phase HPLC methods are discussed in the separation and quantification of tocopherols and tocotrienols (see Basic Protocol). Sample... 

Development of fast, accurate, and reproducible high-performance liquid chromatography (HPLC) methods has offset the use of traditional open-column and TLC methods in modern chlorophyll separation and analysis. A number of normal and reversed-phase methods have been developed for analysis of chlorophyll derivatives in food samples (unit F4.4), with octadecyl-bonded stationary phase (C]8) techniques predominating in the literature (Schwartz and Lorenzo, 1990). Inclusion of buffer salts such as ammonium acetate in the mobile phase is often useful, as this provides a proton equilibrium suitable for ionizable chlorophyllides and pheophorbides (Almela et al., 2000). 

The sample preparation of endohedral metallofullerenes was done by Shino-hara and details are described in the review article [16]. The soot containing M C2 (M=Sc and La) was produced in direct-current (300-400 A) spark mode under He flow at 50 torr and collected under totally anaerobic conditions. The target fullerenes were separated and isolated from the various hollow fullerenes (C60-C110) and other metallofullerenes by the two-stage high-performance liquid chromatography (HPLC) method by using two complementary types of HPLC columns. The purity of the metallofullerenes used for structure analysis relative to other fullerenes was always more than 99.9%. 

Some methods for fast chromatographic separation and detection of PolyPs in food, biological samples or water have been proposed (Halliwell et al., 1996 Baluyot and Hartford, 1996 Svoboda and Schmidt, 1997 Bewsler et al., 2001). A single-column chromatographic system with indirect UV detection was elaborated, and the dependencies of PolyP retention on the concentrations of pyromellitic acid and ethylenediaminetetraacetic acid (EDTA) in the mobile phase and on the pH of the eluent were determined (Svoboda and Schmidt, 1997). A high performance liquid chromatography (HPLC) method has also been used for the separation of PolyPs (Lorenz and Schroder, 1999). 

Developing an elution separation method to be used for the analysis of numerous samples requires more than obtaining the minimal resolution of the solutes of interest. A successful method should not only achieve the desired separation but should also do so in a cost-effective and robust manner. High-performance liquid chromatography (HPLC) method development has its own, extensive literature, reflecting the importance of HPLC as an analytical technique. 

The CCC technique is well suited for the separation of peptides and related compounds because it eliminates sample loss and denaturation caused by the solid support used in conventional liquid chromatography. The method separates multigram quantities of peptide samples using pH zone-refining CCC. 

Degradation samples are analyzed at the initial phases of high-performance liquid chromatography (HPLC) method development using... 

HPLC High Pressure Liquid Chromatography. Analysis method for samples in liquid state. Used for Analysis of heavy crude oil fractions. 

ASTM D 5524 Standard Test Method for Determination of Phenolic Antioxidants in High-Density Polyethylene Using Liquid Chromatography The method technically is very similar to that described in ASTM D 1996, except HDPE samples are analyzed, and extraction is performed with cyclohexane. As the standard notes, besides Irganox 1010, Irganox 1076, and Isonox 129, the test method should be applicable for the determination of other antioxidants such as Cyanox 425, Cyanox 1790, Cyanox 2246, Ultranox 236, and Ultranox 246, but the applicability of this test method has not been investigated for these antioxidants. Precision of the procedure is slightly poorer compared to that of ASTM D 1996 6-13% for within-laboratory tests and 9-19% for between-laboratory tests with concentrations of antioxidants in HDPE from approximately 0.02 to 0.08%. 

A rapid, reversed-phase high-performance liquid chromatography (HPLC) method (38) is described for the determination of clonidine in tablets. Individual tablets or composite samples were sonicated in water, diluted with methanol and filtered. Clonidine formulated at 0.1 or 0.2 rag/tablet was chromatographed on trimethylsilyl-bonded, 5 to 6-pm spherical silica with 65% methanol in pH 7.9 phosphate buffer as mobile phase detection at 254 nm. Mean recovery from 6 synthetic tablet samples was 99.7% (at 0.1 mg/tablet level) with relative standard deviation of 1.55%. 

Zhao G, Wang C, Wu Q, Wang Z. Determination of carbamate pesticides in water and fruit samples using carbon nanotube reinforced hollow fiber liquid-phase microextraction followed by high performance liquid chromatography. Anal Methods 2011 3 1410-1417. 

---