Based-deactivated columns

Bogusz, M. Erkens, M. Maier, R.D. Schroder, I. Applicability of reversed-phase base-deactivated columns for systematic toxicological analysis. J.Liq.Chromatogr., 1992,15,127-150 [simultaneousbral-lobarbital, diphenhydramine, fluphenazine, imipramine, pentobarbital, salicylamide, secobarbital, thiopental, thioridazine]... 

Most pharmacopoeias specify that ethambutol hydrochloride contains not less than 98.0% and not more than 100.5% of C10H24N2O2 2HCI, calculated on the dried basis. Pharmaceutical products such as tablets must contain not less than 95.0% and not more than 105.0% of the labeled amount.As for pyrazinamide, the main pharmacopoeia assay method for ethambutol is a titration method. However, an HPLC method is used for the assay of ethambutol HCl in tablets.This method requires that a liquid chromatograph equipped with a 200-nm detector and a 4.6 mm X 15 cm base-deactivated column that contains 5 p,m porous silica particles, 3-10 p,m in diameter, with chemically bonded nitrile groups (CN, LIO) is used. The mobile phase is a mixture of 1.0 ml of triethylamine and 1 L of water, adjusted with phosphoric acid to a pH of 7.0. The flow rate is about 1.0 ml/min. Separately inject equal volumes (about 50 p.1) of standard preparations and the assay preparations into the chromatograph, record the chromatograms, and measure the responses for the major peaks and calculate the quantity, in mg, of ethambutol hydrochloride present in the tablets from the peak responses obtained from the assay preparation and the standard preparation, respectively. The tailing factor must not be more than 2.0, and the relative standard deviation for replicate injections not more than 2.0%. 

Despite their structural similarity, atropine ( hyoscyamine) and homatropine cannot be assayed in the same way as hyoscine (6,7-epoxyatropine) as the former compounds are very strongly retained on unmodified silica. Reversed-phase methods usually suffer from analyte peak tailing and, although some success with base deactivated columns has been achieved, it has not proved possible to develop... 

Chepkwony, H., Vanderriest, I., Nguyo, ]., Roets, E., and Hoogmartens, J., Separation of erythromycin and related substances on base-deactivated re-versed-phase silica gel columns, /. Chromatogr. A, 870 (1 2), 227, 2000. 

Imazalil, OPP, and TBZ residues were determined using an HPLC system, consisting of a ternary HPLC pump attached to 250 X 4.6-mm-ID Hichrom RPB 5-/tm column with a 10 X 3.2-mm-ID guard cartridge column. The packing material of both columns was base-deactivated silica, fully endcapped with a bonded phase of Cg/C]8. The mobile phase was methanol/water at a flow rate of 1 ml/min at ambient temperature. Imazalil in the eluate was detected with UV detector at 204 nm a fluorescence detector was used to monitor OPP (excitation 285 nm, emission 350 nm) and TBZ (excitation 296 nm, emission 350 nm) (47). 

Chromatographic system (see Chromatography, in the general procedure (621) The liquid chromatography is equipped with a 305-nm detector and a 4.6 mm x 15-cm column that contains 5-/tm base-deactivated packing L7. The flow-rate is about 1.2 ml/min. The chromatograph is programmed as follows ... 

Organic bases Pyridine Separated on a base-deactivated C-18 or C-8 reverse phase column and detected by UV at 254 nm... 

Chromatographic column a stainless steel column, 0.25 m long and 4.6 mm internal diameter, packed with base-deactivated octadecylsilyl silica for chromatography R (5 pm particles). The column is maintained at a temperature of 40°C. 

Adsorption or chemisorption on column packing or on different hardware components. Increase mobile phase strength add competing base (for basic compounds) or use base-deactivated packing ensure no reactive groups are present use inert tubing and flow-path components, e.g., PEEK. 

The standard method for analyzing paraquat is by ion-exchange cleanup followed by reduction to the radical cation, which is colored and read spect rophotometrically(5). The labor requirements and somewhat limited detectability of this method led us to develop a GC method based upon reduction with sodium borohydride to a mixture of the monoene and diene tertiary amines - both of which are amenable to GC on a deactivated column using an N-selective detector( ). The chromatogram shows both peaks (ratios may vary somewhat) which provides built-in confirmation of paraquat because of this dual response pattern. But the reduction-GC method is still a laborious one with a throughput of perhaps 8-10 samples/day under good conditions. It took nearly one man-year to develop and fully Validate. 

The gas chromatography was carried out at a column temperature of 250°C for morphine base. When decreasing amounts of morphine were.chromatographed on a commercial OV-1 column and on the proposed deactivated column, and graphs showing the relationship between peak hight and amounts of morphine were constructed, it was found that the commercial OV-1 column had a cutoff point at 0.4 ug morphine, whereas the proposed deactivated column had a cut-off point at 0.8 ng. Hence, the proposed column showed an improvement in detection limit of the order of 1000-fold. 

Guard column 20 mm long C18 base-deactivated siUca (BDS) (Keystone)... 

Column 250 x 4.6 5 pm Zorbax Rx-C8 base deactivated octylsilane (Mac-Mod Analsdiical) Mobile phase MeCN 10 mM KH2PO4 adjusted to pH 4.0 with 1 M KOH 23 77 Flow rate 1... 

Very recently, Stobo et al. proposed a multiple LC-MS method that allows the detection of YTX together with most of the DSP toxins. The method was set up on a triple quadrupole spectrometer. Chromatographic separation of multiple lipophilic toxins was achieved by using a base deactivated silica C8 column eluted with a 5 mM ammonium acetate-acetonitrile mobile phase under gradient conditions. The method was applied to the analysis of sheUflsh and was validated for the quantitative detection of OA, YTX, PTX-2, and Azaspiracid-1 (AZA-1). 

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