# Hunting Molecules in Complex Matrices with SPME Arrows: A Review
## 3 SPME Arrow Accommodations  
End users may not purchase a SPME Arrow and begin using it as direct replacement for the traditional SPME fiber. There are several things an analyst will need to modify/replace in order to accommodate the SPME Arrows' larger external diameters, including: 1. the injection tool (both manual and robotic); 2. the GC inlet; and 3. the GC inlet liner. First, the manual tool may need modification or replacement (see Figure 2). For example, the traditional SPME fiber holder [19] does not accommodate SPME Arrows. Despite the SPME Arrows sharing a similar length and the same dimensions on the color-coded hubs, the Supelco manual holder tip diameter is too small. Some users have worked around this problem by drilling out the manual holder with a 3/64\" metal compatible drill bit. Alternatively, other users have purchased the Restek PAL manual injection kit (Restek Corporation, Bellefonte, PA, USA), which accommodates both traditional SPME fibers and SPME Arrows without modification. In terms of robotic platforms, CTC Analytics AG does not support the use of SPME Arrows on their second generation PAL systems (e.g., PAL/PAL-xt). Therefore, users with these systems will need to modify their existing SPME holder or acquire an appropriate SPME Arrow holder from Chromtech (Bad Camberg, Germany). Newer generations of robotic arms, such as PAL3 systems (e.g., RTC and RSI), fully support the SPME Arrow as long as users acquire the appropriate tool from \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Analytes**} & **Molecular Weight** & **Stationary Phase** & **Thickness (\(\upmu\)m)** & \begin{tabular}{c} **Needle Diameter** \\ (mm) \\ \end{tabular} \\  & **\(\bullet\)** & **Polydimethylsiloxane** & **100** & **1.1 and 1.5 \(\bullet\)** \\ \multirow{2}{*}{\begin{tabular}{} \end{tabular} } & 60–275 & PDMS & 250 & 1.5 \\ \cline{1-1}  & & & & \\ \hline \multirow{2}{*}{\begin{tabular}{} \end{tabular} } & 60–275 & PDMS & 250 & 1.5 \\ \cline{1-1}  & 80–300 & Polyacrylate & 100 & **1.1** \\ \hline \multirow{2}{*}{\begin{tabular}{} \end{tabular} } & 30–225 & Carbon Wide & 120 & 1.1 and 1.5 \(\bullet\) \\ \cline{1-1}  & & Range (WR)/PDMS & & \\ \hline \multirow{2}{*}{\
\begin{tabular}{} \end{tabular} } & 60–300 & Divinylbenzene & 120 & **1.1 and 1.5 \(\bullet\)** \\ \cline{1-1}  & & (DVB)/PDMS & & \\ \hline \multirow{2}{*}{
\begin{tabular}{} \end{tabular} } & \multirow{2}{*}{40–275} & DVB/Carbon & 120 & **1.1 and 1.5 \(\bullet\)** \\ \cline{1-1}  & & WR/PDMS & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Current SPME Arrow phase configurations. CTC Analytics AG. In the case of rail systems commercialized by other vendors such as Agilent (Santa Clara, CA, USA), Gerstel (Linthicum Heights, MD, USA), Shimadzu (Kyoto, Kyoto Prefecture, Japan), and Thermo (Waltham, MA, USA), users need to contact the manufacturer to acquire the appropriate tool for their robotic system. Furthermore, the fiber conditioner found on second and third generation PAL systems does not accommodate the SPME Arrow diameters. Therefore, users need to directly condition the SPME devices in the GC inlet or acquire an SPME Arrow-specific conditioner module from the appropriate manufacturer. In terms of the GC system, the inlets that are currently installed on the instruments made by major manufacturers (e.g., Agilent, Shimadzu, and Thermo) do not accommodate SPME Arrows. However, factory-modified GC inlets are commercially available for those manufacturers. Alternatively, users can modify their existing GC inlets by drilling out the excess of metal with a 3/64\" metal drill bit. Likewise, traditional SPME fibers require the use of 0.75 mm inlet liners or greater. With the smallest outer needle diameter of 1.1 mm, SPME Arrows require the use of lager inlet liners. Several commercial vendors provide straight-walled inlet liners capable of accommodating SPME Arrows. For example, a 1.8 mm ID straight/inlet liner can accommodate both the 1.1 and 1.5 mm SPME Arrows.