In the present study, the short guard column was used for theonline extraction of sulfonamide residues from honey sample asshown in Fig. 2. Considering the short length of column we strictly control the chromatographic conditions like column temperature,mobile phase composition and flow rate by Chem Station software.The flow rate for short column was 0.30 mL/min while mobile phasewas identical to the one used for long analytical column. The tem-perature for short column and long analytical column was 28◦C.Initially, we performed some experiments to optimize flow rateand mobile phase composition by connecting the short column directly to the fluorescence detector without long analytical col-umn (Fig. 2(d)) for the separation of blank honey sample, matrix based mixed sulfonamide and sulfonamide standard. The results separation obtained by short column, as shown in Fig. 2(c), was usedto switch the valve from position A: (1–4) to B: (1–2), accordingly listed in Table 1. After optimization of the online extraction param-eters for a short C-18 column, the honey sample was injected whenthe HPLC–FLD system was at valve position A: (1–4) (Fig. 2(a)).After 1 min, the valve was switched. The time to switch the valvewas decided earlier from a chromatogram (Fig. 2(c)) obtained byconnecting short column to fluorescence detector (Fig. 2(d)). Afterswitching the valve, the entire sample goes to long analytical col-umn. Fig. 2(e) represents a typical chromatogram obtained by theonline extraction of fifteen sulfonamide residues from honey sam-ple when the HPLC–FLD system was at valve position B: (1–2)(Fig. 2(b)).