345 Results for: "Mobile phases and phase modifiers"

Supplier: Merck

The Ascentis® Express PCS-C18 columns are designed for effective separation of basic, acidic, or neutral compounds using low ionic strength (formic acid) mobile phase conditions.

Supplier: Merck

Silica based SUPELCOSIL™ LC-NH₂ columns separate monosaccharides, disaccharides, and some trisaccharides, with elution generally in order of increasing molecular weight. Retention decreases as the proportion of water:acetonitrile in the mobile phase is increased.

Supplier: Merck

Our NH₂, CN- and DIOL-modified silica sorbents are less polar then conventional silica phases, making them ideal for separating hydrophilic or charged substances. Our moderately polar cyano- and diol-modified silica plates can be used for both normal phase and reversed phase systems. An alternative to PEI cellulose, amino-modified NH₂ plates provide weak basic ion exchange characteristics with special selectivity for charged compounds.

Supplier: Merck

Chromolith® DIOL columns are useful as an intermediate polarity media between C18 and silica. Diol functionalised media is less polar and can have different selectivity. Chromolith® DIOL can be used with a wide range of solvents in both normal and reverse phases. In normal phase mode, the diol phase provides an alternative selectivity compared to silica whilst additionally demonstrating longer retention times that help to obtain separation. In reverse phase mode, compounds such as water-soluble vitamins, sugars or amino acids are easily baseline separated using simple mobile phases. Chromolith® DIOL columns have long lifetimes within pH range of 2,5 to 7,5, high matrix tolerance and speed of analysis.

Supplier: Merck

Fast method development of complex samples across the pH range from 1,5 to 10,5 with different mobile phases and temperature conditions.
Purospher® STAR RP-18 endcapped HPLC columns are designed for universal use. Basic, neutral and metal-chelating compounds can easily be separated with simple mobile phases – naturally without peak tailing. Thanks to its outstanding performance and stability, Purospher® STAR RP-18 endcapped offers maximum flexibility in method development. Robust methods can be developed over the entire pH range from 1,5 to 10,5. High pH-stability allows the separation of strongly basic compounds with alkaline eluents. The combination of high purity silica, best all-round retention characteristics, outstanding pH stability up to pH 10,5, and suitability for up to 100% aqueous mobile phases, make Purospher® STAR RP-18 endcapped an all-round top performance column, almost universal in its range of applications.

Supplier: Merck

These PTFE white hydrophilic membrane compatible with all commonly used HPLC solvents. The membrane undergoes a special treatment process to remove any residual extractables, to provide clearer analysis results. They are widely used for HPLC mobile phase filtration, clarifying acids, bases and dilute protein solutions and isolation of RNA.

Supplier: Merck

CN- and DIOL-modified silica plates are moderately polar that are suitable for both normal and reversed phase systems. The amino modified NH₂ plate provides weak basic ion exchange characteristics with special selectivity for charged compounds offering an alternative to PEI cellulose.

Supplier: Merck

Monolinuron CRM may also be used as given below: Determination of 252 pesticides extracted from surface water samples by solid-phase extraction (SPE) using liquid chromatography quadrupole-orbitrap high-resolution tandem mass spectrometry. Extraction of 13 pesticides from four groundwater and three river water samples using silica-based MSU-1 mesoporous solid as a sorbent for their solid-phase extraction (SPE) followed by ultra-performance liquid chromatography-triple quadrupole-mass spectrometric (UHPLC- QqQ-MS/MS) determination. Development and validation of a UHPLC-diode array detection (DAD) method for simultaneous determination of urea and tebuthiuron herbicides in four fresh vegetable samples. Multi-residue analysis of 50 herbicides in 51 grain samples of soybean corn and wheat by ultra-performance liquid chromatography-electrospray ionisation-mass spectrometry (UPLC-ESI-MS). Extraction of 109 pesticide residues from different chemical classes from 345 tomato samples by modified QuEChERS method and their determination using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Simultaneous analysis of 238 pesticides and 78 veterinary drugs in 80 bovine milk samples using ultra-fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS).

Supplier: Merck

Simazine CRM may also be used as given below: Development and validation of an ultrasonic-assisted dispersive liquid-liquid microextraction (UA-DLLME) method for sample extraction followed by gas chromatography-mass spectrometry based determination of endocrine-disrupting herbicides in the river and seawater samples. Determination of triazine pesticide residues in samples of apples pears carrots potatoes tomatoes avocado cucumber spinach bananas and oranges by modified QuEChERS and solid-phase extraction (SPE) procedures followed by liquid chromatography-photodiode array (LC-DAD) analysis. Multi-residue analysis of 67 pesticides in olive oil olives and avocado samples by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to evaluate various clean-up sorbents. Quantitation of 20 pesticides in eel and shrimp samples by a scheduled multiple reaction monitoring (sMRM) method and QuEChERS with EDTA for sample extraction and purification. Analysis of 35 micropollutants including pesticides in water samples by liquid chromatography-tandem mass spectrometry (LC-MS/MS) after their solid-phase extraction. Simultaneous quantification of 58 pharmaceuticals and personal care products (PPCPs) and pesticides in water samples by solvent-based de-emulsification dispersive liquid-liquid microextraction (SD-DLLME) combined with liquid chromatography-tandem mass spectrometry (LCMS/MS).

Supplier: Merck

Purospher® RP-18 is designed for the separation of problematic basic compounds with simple neutral eluents. In addition Purospher® RP-18 allows the separation of hydrophilic compounds with aqueous mobile phase. Purospher® RP-18 is based upon a high purity, metal-free silica. The multi-step chemical modification and deactivation of the surface, and the polar endcapping, enables a peak-tailing-free elution of basic and chelating compounds. Purospher® RP-18 is not suitable for the separation of acidic compounds. The good chemical stability of Purospher® RP-18 enables the use of mobile phase conditions at pH 8 for a long period of time.

Supplier: Merck

HPTLC LiChrospher® plates are based on spherical-shaped silica 60 with a particle size of 7 µm, and narrow particle size distribution similar to the phases used in HPLC. LiChrospher® HPTLC plates possess a selectivity that is comparable to respective HPTLC plates, however, plate height and separation numbers are further improved resulting in shorter analysis times.

Supplier: Merck

RP-2, RP-8 and RP-18 are based on silica gel 60 modified with aliphatic hydrocarbons. The chain length, in combination with the degree of modification, defines the ability to tolerate water in the solvent system and strongly affects retention. Migration time increases in the order RP-2, RP-8 and RP-18 using the same solvent composition. RP-8 and RP-18 can be run with up to 60% water in the solvent system.

Supplier: Merck

Unmodified and modified cellulose plates for the analysis of polar substances.

Supplier: Merck

PLC (Preparative Layer Chromatography) plates are based on the same proven Merck silica-binder technology as analytical TLC plates. Plates are available with layers of unmodified silica gel or RP-18 modified silica gel in several layer thicknesses, ranging from 500 to 2000 µm, with or without fluorescent indicator.

Supplier: Merck

Coupling TLC plates to mass spectrometry is a new field of high interest, which will contribute strongly to the progress of planar chromatography. The MS-grade plates are much cleaner than standard TLC/HPTLC plates providing higher sensitivity and reduced background signals. This allows trace analysis with mass spectrometry detection in lower nanogram range.

Supplier: Merck

TLC plates, unmodified silica gel 60
This range of plates uses Merck silica gel 60 with a unique polymeric binder that results in a uniform, hard surface that will not easily crack or blister. The smooth, extremely dense plate coating ensures narrow bands and maximum separation efficiency with the lowest background noise. Layer thickness 200 μm and, particle size of 10 to 12 µm. Flexible aluminium plates that can easily be cut to match individual separation requirements. Two inorganic fluorescent indicators for UV detection of colourless substances. Samples which absorb shortwave UV at 254 nm are detected due to fluorescence quenching.

Supplier: Merck

TLC plates, unmodified silica gel 60
Merck silica gel 60 has a unique polymeric binder that results in a uniform, hard surface that will not easily crack or blister. This smooth, extremely dense plate coating ensures narrow bands and maximum separation efficiency with the lowest background noise. Layer thickness 250 μm and particle size of 10 to 12 µm. Two inorganic fluorescent indicators for UV detection of colourless substances.

Supplier: Merck

Solid phase extraction disks provides faster flow rates and exhibits less clogging than PTFE discs for the extraction of organic contaminants from drinking water samples.

Supplier: Merck

The LC-NH2-NP is an amino phase dedicated to normal phase chromatography suitable for separation of wate insoluble analytes like fat soluble vitamins.

Supplier: Merck

Aluminium oxide, γ-phase

Supplier: Merck

Polydimethylsiloxane + Polydiphenylsiloxane, ~500 mPa.s (25 °C) (1:1) DC-710 stationary phase for GC, Supelco®

Supplier: Merck

HPLC Standard, Reversed Phase Test Mix 2, TraceCERT®, Supelco®, in acetonitrile: water (varied conc.) solution, Certified reference material, Pk Info: ampule of 1 mL

Supplier: Merck

These SUPELCOSIL LC-DB phases are specially deactivated for basic compounds. These columns provide less retention, better peak shape, and higher efficiency for organic bases than can be obtained on conventional reversed-phase columns.

Supplier: Merck

HPLC Standard, Reversed Phase Test Mix, in methanol: water (3:2) (varied conc.), TraceCERT®, Supelco®, Certified reference material, Pk Info: ampule of 1 mL

Supplier: Merck

4-Hydroxy-4-methyl-2-pentanone may be used as an internal standard in the analysis of volatile odor-active compounds present in wine using solid phase extraction with gas chromatography (SPE-GC).

Supplier: Merck

These screw cap valve (SCV) bags are suitable for calibration mixes - gas phase standards/gas mixtures.

Supplier: Merck

Promecarb may be used as a reference standard for the determination of promecarb in water by solid-phase extraction and liquid chromatography coupled with ionspray mass spectrometry.

Supplier: Merck

Brockmann aluminum oxides are suitable for column chromatography and adsorptive filtration. Aluminum oxides are generally used as solid support phases in solid phase extraction (SPE)-based clean-up procedures employed in chromatographic methods

Supplier: Merck

Ascentis® Silica HPLC columns for the classic use in normal phase HPLC.

Supplier: Merck

Tetrabutylammonium hydroxide (TBAOH) is a quaternary ammonium salt,mainly used as a strong base and phase-transfer catalyst.