Water for HPLC

Tetrabutylammonium bromide (TBABr), recrystallize from ethyl acetate Ultrapure water for HPLC analysis... 

Reagents. Organic solvents for HPLC separations—methylene chloride, methanol, isopropyl alcohol, hexane, and acetonitrile—were obtained as HPLC grade from Fisher Scientific. Type I water for HPLC and for the preparation of other aqueous solutions was purified as described previously (7). All HPLC solvents were filtered through a 0.45-/zm Millipore membrane filter (Millipore Corporation) and degassed... 

Ultrapure water for HPLC should be freshly prepared by a purification train or by distillation. Water extracts impurities from polyethylene or glass after storage for a few hours. 

Fig. 12.2 Time dependencies of sonophotocatalytic reaction products from pure water. As powdered photocatalyst, Ti02-A (200mg, Soekawa, Commercial Reagent, rutile-rich type and specific surface area 1.9 m2/g) was used without further treatment. Liquid water (150 cm3, Wake, Distilled water for HPLC was used as reactant and was purged with argon, a Pyrex glass bulb (250-300 cm3) was used as a reactor and was placed m a temperature-controlled bath (EYELA NTT-1200 and ECS-0) all time. After the glass bulb was sealed, the irradiation was carried out under argon atmosphere at 35°C. Photo and ultrasonic irradiations were performed from one side with a 500 W xenon lamp (Ushio, UXL500D-O) and from the bottom with an ultrasonic generator (Kaijo. TA-4021-4611, 20C kHz 200 W), respectively.

Water for HPLC is, unfortunately, not free as it must be specially purified. Ion exchange water is generally not of sufficient purity and double distillation stills may even increase the content of organics. It is best either to purchase HPLC grade water or to use water which is produced by a multiple-stage purification system. Sterile water is obtained by filtration through a 0.2 pm filter. 

In order to determine the enantiomeric excess of the product, the Boc protective group must be removed prior to HPLC analysis. The sample is prepared by dissolving 23 mg of N-Boc allylglycine in 1 mL of tetrahydrofuran and adding 2 mL of a 3 M aqueous hydrochloric acid solution. The mixture is allowed to stir at 23°C for 1 hr and then is concentrated under reduced pressure to provide a solid residue. The solid is dissolved in water for HPLC analysis. The product is determined to be >99% ee by analysis on a Crownpak CR(+) column (Notes 22 and 27). 

For APCI (if matrix effects become a problem in ESI), the mobile phase consisted of (A) 9 1 methanol-water containing 50 mM ammonium acetate and (B) water containing 50 mM ammonium acetate-methanol (9 1). The gradient was held at 50% A-50% B for 10 min and was then changed to 90% A-10% B in 22 min (held for 3 min). The HPLC column was a Zorbax RX-C8, 4.6-mm i.d. x 250 mm, 5 pm particle size, with a flow rate of l.OmLmin and a 50-pL injection. Table 8 shows the ion transitions (parent to product ions) that were monitored for HPLC/ESI-MS/MS. For single-stage HPLC/ESI-MS, Table 9 shows the ions that were monitored. 

After extracting fluthiacet-methyl from the soil extract with n-hexane, pass the residual aqueous layer through a dual cartridge of Sep-Pak Plus NH2 and Sep-Pak Plus C18 to adsorb the free form of fluthiacet-methyl on Sep-Pak Plus Gig. Remove the Sep-Pak Plus C18, wash it with 0.5% acetic acid and acetonitrile-water-acetic acid (20 80 0.5, v/v/v), elute with acetonitrile-water-acetic acid (50 50 0.5, v/v/v) and quantify the free form by HPLC. The operating conditions for HPLC are the same as those for fluthiacet-methyl, except that the mobile phase is acetonitrile-water-acetic acid (50 50 0.5, v/v/v) (retention time 8.8 min). 

Methanol, ethanol, acetonitrile, benzene, trifluoroacetic anhydride, triethylamine, distilled water reagent grade (Wako Pure Chemical Industries, Ltd, Japan) Methanol, distilled water specially prepared reagent for HPLC (Wako Pure Chemical Industries, Ltd, Japan)... 

Boundaries in chromatography and extraction are blurring, as evident from the relation between GC, SFC and HPLC, the use of superheated/subcritical water for extraction and chromatography, and the role of enhanced fluidity solvents and pressurised fluid extractions [2]. Extraction is an extreme form of chromatography. Separation science recognises that there is unity in the... 

He et al. (2002) used an off-line HPLC/CE method to map cancer cell extracts. Frozen ovarian cancer cells (containing 107 cells) were reconstituted in 300 pL of deionized water and placed in an ultrasonic bath to lyse the cells. Then the suspension was centrifuged and the solubilized proteins were collected for HPLC fractionation. The HPLC separation was carried out on an instrument equipped with a RP C-4 column, 250 mm x 4.6 mm, packed with 5-pm spherical silica particles. Extracted proteins were dissolved in 300 pL of DI water, and lOOpL was injected onto the column at a flow rate of 1 mL/min. Buffer A was 0.1% TEA in water and buffer B was 0.1% TFA in acetonitrile. A two-step gradient, 15-30% B in 15 min followed by 30-70% B in 105 min, was used. The column effluent was sampled every minute into a 96-well microtiter plate with the aid of an automatic fraction collector. After collection, the fractions were dried at room temperature under vacuum. The sample in each well was reconstituted before the CE analysis with 10 pL deionized water. The... 

A six-port valve was used in both manual and semi-automated SPME interfaces and PEEK tubing used to connect the HPLC system to the SPME probe. A Cohesive HTLC 2300 with dual pumps along with a Sciex API 3000 mass spectrometer was used for LC/MS/MS and a Symmetry Shield RP-18 (5 ji, 50 x 2.1 mm) for HPLC. A quaternary pump with flow switching was used for desorption chamber flushing along with MS make-up flow and a binary pump for LC/MS/MS. Acetoni-trile/0.1% acetic acid in water (90 10, solvent B) and 10 90 acetonitrile/0.1% aqueous acetic acid (solvent A) were used, with 10% B for 0.5 min ramped to 90% B in 2 min and held at this concentration for 1.5 min before returning to 10% B for 1 min at a flow rate of 0.5 mL/min. 

A novel development for HPLC is something called bonded reversed-phase columns, where the stationary phase is a nonpolar hydrocarbon, chemically bonded to a solid support. You can use these with aqueous eluents, usually alcohol-water mixtures. So you have a polar eluent and a nonpolar stationary phase, something that does not usually occur for ordinary wet-column chromatography. One advantage is that you don t need to use anhydrous eluents (very small amounts of water can change the character of normal phase columns) with reversed-phase columns. 

Krzyszowska AJ, Vance GF. Solid-phase extraction of dicamba and picloram from water and soil samples for HPLC analysis. J. Agric. Food Chem. 1994 42 1693-1696. 

---