Guidelines for method choice
Henk Lingeman, Free University, Free University, NetherlandsLevelBasic
Guidelines for method choice in analytical chemistry
Choosing the necessary sampling and SP steps for the determination of analytes in a complex and dirty matrices is one of the most troublesome to perform, and therefore, the degree of SP depends on quite a number of parameters. The most important ones are the:
- Concentration of the analyte;
- Composition of the matrix;
- Number of samples to be analyzed;
- Chosen separation / detection system.
This paragraph presents general guidelines for separation method selection. To simplify the tables only organic molecules with a MW of less than 1 kD are taken into account. This means that some of the separation techniques mentioned earlier e.g. SEC are not taken into consideration. (HP)TLC means that in case quantitative or semi-quantitative results should be obtained high-performance TLC (HPTLC) should be used instead of classic TLC. The abbreviations used are explained in the 'List of abbreviations and glossary of symbols'.
Tables: Guidelines for method choice in analytical chemistry.
| Questions to be answered: | Possible techniques: | |
| Aggregation phase: | Gas | GC, SFC |
| Liquid / solid | CE, GC, IEC, LC, OPTLC, (HP)TLC, SFC | |
| Charge: | Not present | GC, LC, MECC, OPTLC, (HP)TLC, SFC |
| Present | CE, IEC, LC (IP, IS) | |
| Functional groups: | Not present | Almost no derivatization possibilities |
| Present | Derivatization potential | |
| Polarity: | Low | Non-polar sorbents in chromatography |
| High | Polar sorbents in chromatography | |
| Saturations (aromaticy): | Aliphatic | AMP, CL, CON, ECD, FID, FS, IR, NMR, NPD, PID, POL, RI, SIM, |
| Conjugated / aromatic | AMP, CIF, CL, CON, ECD, FID, FS, IR, LIF, NMR, NPD, PID, POL, RI, SIM, UV-VIS | |
| Solubility: | Polar solvents | CE, IEC, LC, OPTLC, (HP) TLC |
| Non-polar solvents | GC, LC, OPTLC, (HP)TLC, SFC | |
| Volatility: | Low | CE, IEC, LC, OPTLC, (HP)TLC, SFC |
| High | GC, LC, SFC |
| Complexity of the matrix: | Degree of automation, amount of effort: | |
| Analyte - matrix binding: | None | No special precautions |
| Yes | Denaturation procedures should be used in case of drug -protein binding or other analyte - matrix disrupting techniques | |
| Minimum detectable concentration(s): | 1 - 1000 μg/mL | CE, GC, LC, OPTLC, (HP)TLC, SFC, AMP, CIF, CON, ECD, FID, IR, NMR, NPD, PID, POL, RI, SIM, UV-VIS |
| 1 - 1000 ng/mL | CE, GC, LC, OPTLC, HPTLC, SFC AMP, CIF, CL, ECD, LIF, NPD, PID, SIM, UV-VIS | |
| 1 - 1000 pg/mL | CE, GC, LC, SFC, AMP, CIF, CL, ECD, LIF, SIM | |
| 1 - 1000 fg/ml | CE, LC, (SFC), CL, LIF | |
| Stability: | Bad | Stabilizing procedures |
| Good | No stabilizing procedures needed |
| Availability equipment: | Determines choice of SP / ST, separation / detection system | |
| Available expertise: | Determines choice of system components and the degree of automation | |
| Number of solutes to be determined | < 10 | CE, GC, LC, OPTLC, SFC |
| > 10 | CE, GC, LC | |
| Number of samples to be analyzed in each series: | Degree of automation | |
| Number of sample series to be analyzed | Degree of automation | |
| Profiling of analytes: | Yes | CL-MS/(MS), GC-MS/(MS), LC-FTIR, LC, NMR, LC-DAD |
| No | No restriction in separation / detection mode | |
| Rationale for analysis | Qualitative | CE, GC, LC, OPTLC, SFC, TLC |
| Semi-quantitative | CE, GC, LC, OPTLC, SFC, TLC | |
| Quantitative | CE, GC, LC, SFC | |
| Reason for analysis: | Legal | Reliability most important parameter |
| Toxicological | Speed most important parameter | |
| TDM | Throughput important parameter | |
| Drug development | Screening and identification of metabolites important parameters | |
| Ruggedness of the method | High | CE-DAD, GC-ECD, GC-FID, GC-NPD, LC-CIF, LC-DAD, automated reaction / detection systems |
| Low | No restrictions | |
