Sample preparation pharmaceutical residues

See alsa Chromatography Multidimensional Techniques. Environmental Analysis. Extraction Solid-Phase Extraction. Food and Nutritional Analysis Sample Preparation Contaminants Pesticide Residues. Forensic Sciences Drug Screening in Sport Illicit Drugs. Herbicides. Liquid Chromatography Instrumentation Clinical Applications Food Applications. Mass Spectrometry Peptides and Proteins. Pesticides. Pharmaceutical Analysis Sample Preparation. Proteomics. Sample Handling Automated Sample Preparation. Water Analysis Organic Compounds. 

Examples of the application of headspace extraction are flavors in food products, volatile organic compounds in soils, and residual solvents in pharmaceutical products [33, 34]. The main advantages of headspace extraction are minimal sample preparation and the possibility for direct introduction of headspace gas into the gas chromatograph. 

In contrast to more established spectroscopic techniques, SS-NMR spectra are virtually independent of the physical properties of the sample, such as particle size, homogeneity, or residual water content. Therefore, pharmaceutical solids can be studied by NMR without a need for special sample preparations. Samples viable for SS-NMR analysis include a whole range of pharmaceutical formulations such as tablets, lyophilized powders, capsules, suspensions, and ointments. SS-NMR does not suffer from a preferred orientation restriction, which often leads to an incorrect identification of polymorphs when using XRPD. In addition, SS-NMR is a nondestructive technique that allows other analyses to be performed on the same sample after the NMR spectrum is acquired. 

The preferred sample preparation method for residual solvent analysis of pharmaceuticals is direct injection of the dissolved sample (11,60). With this technique, the recovery is most reliable because there is no opportunity for recovery loss due to adsorption or entrapment. The other techniques involve a separation of the volatiles before the GC injection and there is a risk that the volatile will be trapped. Typical solvents for this analysis are water, dimethyl sulfoxide, benzyl alcohol, and dimethylformamide (11,12,61). The three latter solvents are chosen because they are higher-boiling than commonly used pharmaceutical solvents and thus elute after them and do not interfere with the analysis. Water offers the advantage that it contributes little interference with a flame ionization detector. 

Bicchi and Bertolino [193] analyzed a variety of pharmaceuticals for residual solvents. Samples were equilibrated directly or dissolved in a suitable solvent with a boiling point higher than that of the residual solvent to be determined. Equilibration conditions were 90 or 100°C for 20 min. A Perkin-Elmer HS-6 headspace sampler was used. The chromatographic phase chosen was a 6 x Vs in. column packed with Carbopack coated with 0.1% SP 1000. Residual ethanol in phenobarbital sodium was determined by a direct desorption method. An internal standard, /-butanol, was used. Typically, 0.44% of ethanol was detected (compared to a detection limit of 0.02 ppm). The standard deviation of six determinations was 0.026. Pharmaceutical preparations which were analyzed by the solution method included lidocaine hydrochloride, calcium pantothenate, methyl nicotinate, sodium ascorbate, nicotinamide, and phenylbutazone. Acetone, ethanol, and isopropanol were determined with typical concentrations ranging from 14 ppm for ethanol to 0.27% for acetone. Detection limits were as low as 0.03 ppm (methanol in methyl nicotinate). 

The QuEChERS method was invented and described for the first time in 2003 by Anastassiades et al. [98] as a fast, simple, inexpensive, and convenient preparation procedure for fruit and vegetable samples used for pesticide multiresidue analysis. Currently, this methodology is used for determinations of pesticides, pesticide residues, and other compounds of environmental concern such as phenol derivatives, perfluorinated compounds, and chlorinated hydrocarbons pharmaceutical compounds in food and agricultural matrices and environmental samples such as soil, sediments, and water (see for example [99-102]). 

Sulphonamides in pharmaceutical preparations and urine were determined indirectly using flame AAS by continuous precipitation with copper or silver, as proposed by Montero et al.[22]. The copper method exhibited a better selectivity, and only this was used for determinations in urine. The precipitate, formed by injecting one of the cations into a carrier containing the sample, was collected on an on-line filter, and the peak absorbance of the residual metal in the stream passing through the filter was measured. The decrease in peak height compared to a blank was then related to the sulphonamide... 

Moniero et al.[24] developed an indirect AAS method for the determination of local anaesthetics (lidocaine. tetracaine and procaine hydrochlorides) in pharmaceutical preparations using FI on-line precipitation-dissolution. A cobalt solution is injected into a carrier stream containing the sample, and the precipitate formed is retained on an online stainless steel filter. The determinations were made by measuring the residual cobalt concentration in a similar way as for the indirect determination of sulphonamides (cf. Sec. 9.4.2). A sampling frequency of 100 h was achieved with a precision of 0.6% r.s.d.. 

Palladium chloride detects phosmethylan (55) with 0.5 pg/spot sensitivity. This reaction was used for quinalphos (7), phosphamide (8), and methamidophos in food samples (154) as well. Malathion residues were studied in pharmaceutical preparations by dipping plates into a 0.1 % solution of palladium chloride in hydrochloric acid, yielding yellow spots that could be quantitatively determined by scanning at 400 nm (159). 

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