Solid-phase extraction: method development, sorbents, and coupling with liquid chromatography

Solid-phase extraction using cartridge and disc devices is a widely used sample-preparation technique for isolation, concentration, clean-up and medium exchange. To meet the varied needs of contemporary applications, there is available an ever-increasing range of sorbent chemistries based on inorganic oxides, low-specificity (chemically bonded, porous polymer and carbon) and compound and group-selective (ion exchange, mixed mode, macrocyclic, restricted access, immunoaffinity and molecularly imprinted polymer) materials. Advanced device formats facilitate processing of problem samples combined with a high level of automation. Approaches to computer-aided method development promise to replace tedious trial-and-error procedures with fast simulations based on suitable kinetic and retention models.

New trends in solid-phase extraction

Environmental mass spectrometry: emerging contaminants and current issues.

https://link.springer.com/content/pdf/10.1016%2FS1044-0305%2803%2900574-9.pdf

Matrix effect in bio-analysis of illicit drugs with LC-MS/MS: influence of ionization type, sample preparation, and biofluid.

Stir bar sorptive extraction for trace analysis

Reversed phase LC is coupled to capillary GC by means of an on-line extraction of the LC eluent. The extract is transferred to a loop-type LC-GC interface equipped with an early vapor exit. Using a phase switch from an aqueous reversed-phase (RP)LC solvent to an organic solvent facilitates the introduction of the analyte in the GC system, since organic solvents such as hexane, pentane, and dichloromethane are more appropriate for the GC-injection technique used in this study. As the partition coefficient of an organic solvent/aqueous system is correlated to the retention mechanism of reversed phase LC, the method has a general potential in LC/GC interfacing, viz. the extractability a component from the LC mobile phase eluting above a certain capacity factor from a RPLC column can be expected to be efficient. The method is applied to the determination of residues of the fungicide fenpropimorph in barley, oats, rye, and wheat. Another application of the interface which is feasible is the on-line extraction of aqueous samples prior to large volume injection on GC-NPD. The potential of the interface for the determination of residues nitrogen containing herbicides is estimated.

Reversed‐phase LC‐GC with a nitrogen‐phosphorus detector using a loop‐type interface combined with a sandwich‐type phase separator

Deactivation of precolumns with an ultra thin film of OV-1701 provided inertness at least equal to silylation, but better resistance to water Dynamic coating of the raw fused silica capillary is, furthermore, much faster than the hydrothermal treatment/silylation procedure

Deactivation of precolumns for capillary GC by a thin layer of OV‐1701

In a previous work, coupled-column LC (LC/LC) with direct large-volume sample injection for the analysis of β 2 -agonists in bovine urine was investigated, in view of its combination with thermospray (TSP) tandem mass spectrometric (MS/MS) detection In this work, the potential of both conventional LC and LC/LC coupled to TSP-MS/MS for the rapid determination of β 2 -agonists in bovine urine was evaluated It was first established that, in order to avoid disturbances in TSP-MS/MS detection due to changes in pressure and flow rate of the mobile phase, LC/LC is preferable to conventional LC Then, selecting clenbuterol and salbutamol as model compounds for the class of β 2 -agonists, two single-residue LC/LC/TSP-MS/MS methods were developed, permitting the determination of the analytes in bovine urine samples with a limit of quantification of at least 01 ng, ml -1 , with a sample throughput of 4 h -1  The methods were validated by analysing both spiked urine samples and samples containing clenbuterol or salbutamol residues Mean recoveries from urine samples spiked with clenbuterol at levels of 5 and 022 ng ml -1 were 107% (n = 9, RSD = 74%) and 102% (n = 6, RSD = 14%), respectively A bovine urine sample containing 128 ng ml -1 clenbuterol residue (previously quantified by GC/MS) was re-analysed by LC/LC/TSP-MS/MS on four different days (n = 3, each day) and yielded a mean concentration of 131 ng ml -1 , with a reproducibility of 84% Bovine urine samples spiked with salbutamol at levels of 108 and 055 ng ml -1 yielded mean recoveries of 101% (n = 3, RSD = 1%) and 89% (n = 3, RSD = 13%), respectively In bovine urine samples containing salbutamol residues, the concentrations of unconjugated salbutamol were found to be in the range 8-57 ng ml -1

Hyphenation of Coupled-column Liquid Chromatography and Thermospray Tandem Mass Spectrometry for the Rapid Determination ofβ2-Agonist Residues in Bovine Urine UsingDirect Large-volume Sample Injection.Set-up of Single-residue Methods for Clenbuterol and Salbutamol

Multi- and univariate interpretation of the interlaboratory validation of PrEN 12673; GC determination of chlorophenols in water

A method has been developed for the sample clean-up of organophosphorus pesticides (OPPs) in mussels prior to gas chromatography analysis. The system applied uses a HPLC pump and a silicagel column A diode array detector is used to monitor, on line, the elution of the fat present in the mussel soft tissue that was extracted with acetonitrile :acetone and redissolved in hexane. Polar and moderately polar pesticides were fractionated and separated from fats using hexane :ethyl acetate 95/5, v/v as mobile phase. The most polar pesticides (chlorfenvinphos, phosmet and dimethoate) were eluted from the column using ethyl acetate. For the elution of non polar pesticides (chlorpyrifos, phorate and fonofos) in fat free fractions it was necessary to use hexane as mobile phase switching on to hexane:ethyl acetate 99/1 (v/v) (4 ml) after 4 min of elution. Quantitative measurement of fat content in collected fractions from LC system was carried out by colorimetry in order to know the efficiency of the clean-up and the amount of fat injected in the GC system. Fat free fractions containing pesticides obtained after LC clean-up can be injected directly, without further clean-up steps or solvent exchange, in the GC system. The limits of detection for the organophosphorus pesticides investigated varied between I and 40 ng/g using mass selective detector and between 0.1 and 2 ng/g using nitrogen-phosphorus selective detector. Recoveries of the overall procedure, including extraction and clean-up, were obtained at 400 and 4() ng/g levels and they varied between 89 ± 9% and 105 ± 4%.

Piet van Zoonen

Papers

Reversed‐phase LC‐GC with a nitrogen‐phosphorus detector using a loop‐type interface combined with a sandwich‐type phase separator

Deactivation of precolumns for capillary GC by a thin layer of OV‐1701

Hyphenation of Coupled-column Liquid Chromatography and Thermospray Tandem Mass Spectrometry for the Rapid Determination ofβ2-Agonist Residues in Bovine Urine UsingDirect Large-volume Sample Injection.Set-up of Single-residue Methods for Clenbuterol and Salbutamol

Multi- and univariate interpretation of the interlaboratory validation of PrEN 12673; GC determination of chlorophenols in water

Sample clean-up and fractionation of organophosphorus pesticide residues in mussels using normal-phase LC