Pre-column clean-up and liquid chromatographic determination of residues of N-methylcarbamate pesticides in extracts of total diet

Goewie, C.E.; Hogendoorn, E.A.

doi:10.1016/s0021-9673(01)86876-x

Cited by 31 publications

(7 citation statements)

References 7 publications

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“…14 Pre-column switching has recently become a widespread means of improving the sample throughput, separation efficiency and, if the precolumn is used for concentration purposes, also the loadability of liquid chromatographic systems. 15,16 In this study we investigated a comparison of drug release and bioavailability from different oral controlled-release and conventional oral formulations containing levodopa and carbidopa. We monitored the plasma profiles and evaluated the pharmacokinetics and availability of these drugs in biological fluids, using reliable multi-dimensional column chromatography employing amperometric detection with a carbon fibre microelectrode procedure.…”

Section: Introductionmentioning

confidence: 99%

Bioavailability studies of oral dosage forms containing levodopa and carbidopa using column-switching chromatography followed by electrochemical detection

Sagar

Smyth

2000

Analyst

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A reliable multi-dimensional column chromatographic method employing amperometric detection using a carbon fibre microelectrode procedure was used for monitoring the plasma profiles and to evaluate the pharmacokinetics and bioavailability of levodopa (L-dopa) and carbidopa (C-dopa), after ingestion of oral formulations containing these drugs. The peak currents obtained for the different analytes were directly proportional to the analyte over the concentration range 0.02-4 micrograms ml-1. Using this method, the minimum detectable concentration was estimated to be 5 and 8 ng ml-1 for L-dopa and C-dopa, respectively. Recovery studies ranged from 93.83 to 89.76%, with a relative standard deviation of less than 7%. The study was carried out in two separate weeks on five healthy non-patient fasted male/female volunteers in the age range 20-37 years and weighing between 60 kg and 78 kg. The pharmacokinetic profile of two controlled-release products containing both L-dopa and C-dopa (Sinemet CR3 and CR4) was compared on the one hand and Sinemet conventional tablets on the other. The pharmacokinetic parameters, peak concentration (Cmax), the time taken to obtain this level (Tmax), elimination half-time T1/2, elimination rate constant (Kel), plasma level ratio, fluctuation index (FI) and the area under the time-concentration curve (AUC0-8), were investigated for each individual formulation. A comparison of the uptake of L-dopa from the conventional formulation showed that L-dopa entered the plasma and achieved peak levels higher than that of the controlled release formulations. However, it showed a much higher fluctuation index and the plasma concentrations were more stable with the controlled release formulations. The data also indicated a very low accumulation of both levodopa and carbidopa following repeated administration of the drugs, which was consistent with their relatively short half-lives (less than 2 h). In contrast, the half-life for the metabolite 3-orthomethyl dopa (3-OMD) is in the order of 13 h. As a result, there was an extensive accumulation of 3-OMD and its levels were significantly higher than those of levodopa or carbidopa upon repeated administration. Urine recoveries of the three analytes over one 8 h dosing interval showed that the majority of the excreted levodopa and carbidopa was recovered during the first 4 h, and there is proportionally greater excretion of the carbidopa dose than the levodopa dose.

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Section: Introductionmentioning

confidence: 99%

Bioavailability studies of oral dosage forms containing levodopa and carbidopa using column-switching chromatography followed by electrochemical detection

Sagar

Smyth

2000

Analyst

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“…For the determination of N-methylcarbamates we had good results for the tr -automated clean-up of total diet extracts using RP-18 pre columns of this type [14] However, the silica column of this type was not able to give enough separation between the early and later eluting OCP's A 100 X 3 mm ChromSep column (Lichrosorb Si-60,7 pm) resulted in rather large retention volumes for dieldrin (approx 50 ml) and s o it was excluded for further use as a precolumn A more suitable column was a 4 6 mmi d stainless steel column packed with 10 pm Lichrosorb S1-60 The length of this column was 60 mm being the minimum length for a normal bore column with Valco nuts On this column dieldrin elutes after 20 minutes and separation is such that a column-switch can be made at 3 8 minutes, in this way, all compounds eluting before p,p'-TDE are sent to the second column for further separation An example of the separation capabilities of this (pre)column is shown in Figure 2 It must be noted that the separation is strongly influenced by the inlection of 45 ing fat Hence, for analyzing samples with a low fat content the dimensions of the first separation column should be reconsidered In some cases it can even be omitted if one accepts relatively large retention times for dieldrin…”

Section: Resultsmentioning

confidence: 99%

Automated sample clean‐up and fractionation of organochlorine pesticides and polychlorinated biphenyls in human milk using NP‐HPLC with column‐switching

Hogendoorn

Hoff

Zoonen

1989

J. High Resol. Chromatogr.

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SummaryA method has been developed forthe automated sample pretreatment of organochlorine pesticides (OCP's) and polychlorinated biphenyls (PCB's) in extracts of human milk.This workwas part of a regular monitoring program presently carried out at our institute.In this program several hundreds of human milk samples have to be analyzed for the occurrence of PCB's and OCP's.With a normal bore straight phase HPLC system, utilizing column switching we are able to separate the fat from the compounds of interest and, moreover, complete separation of the PCB fraction from the OCP's can be achieved. Under the conditions used to separate the PCB fraction from interfering OCP's column-switching is essential since the retention times for the OCP's vary from 4 minutes for hexachlorobenzene (HCB) to more than 2 hours for dieldrin.1 ml of an extract containing 45 mg of fat is injected on the first (pre)column, the fat is retained on this column and the early eluting HCB, the PCB fraction, and the DDT complex are transferred to the second (analytical) column.Compounds eluting later than p,p'-DDT are collected directly from the precolumn. Meanwhile, the PCB fraction is separated from the rest of the OCP's on the analytical column.Contrary to conventional gravity-controlled chromatography or solid phase extraction the clean-up process can be monitored on-line by UV-detection, thus rendering a fast and reliable optimization of the system.The OCP-fractions collected from the LC are pooled before they are transferred to a high resolution gas chromatograph equipped with a large volume option. The PCBfraction is injected directly in a HRGC equipped with a concurrent solvent evaporation injection device.

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“…Nonselective reversed-phase, carbon and porous polymer packings are generally used [301][302][303][304], although recently more selective sorbents, such as metal-loaded ion exchangers for the selective isolation of herbicides containing an ethnyl group from water [3 05-307] and a silver(1)thiol stationary phase for preconcentration of the AIDS drug AZT from plasma [307,308] have been used. When sample dilution prevents detection, trace enrichment is required.…”

Section: Multidimensional Liquid Chromatographymentioning

confidence: 99%

Sample Preparation for Chromatographic Analysis

Poole

1991

Chromatography Today

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Pre-column clean-up and liquid chromatographic determination of residues of N-methylcarbamate pesticides in extracts of total diet

Cited by 31 publications

References 7 publications

Bioavailability studies of oral dosage forms containing levodopa and carbidopa using column-switching chromatography followed by electrochemical detection

Bioavailability studies of oral dosage forms containing levodopa and carbidopa using column-switching chromatography followed by electrochemical detection

Automated sample clean‐up and fractionation of organochlorine pesticides and polychlorinated biphenyls in human milk using NP‐HPLC with column‐switching

Sample Preparation for Chromatographic Analysis

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