Laser ablation cells with fast washout characteristics, like the former M50/M50A cells and the latest S155 cell, can sometimes respond too rapidly to a changing ablation signal. This is most notable for analysis at low laser repetition rates, which for Laurin Technic cells is typically 7Hz and below. A smoothing device is then required to smooth out signal fluctuations, and ideally it should retain a fast rise time and washout or some of the advantage of the two-volume cell is lost. The literature shows that many signal smoothing devices, usually just a container the carrier gas passes through, introduce memory effects and dramatically extended washout times.
To overcome these difficulties, Laurin Technic developed “The Squid,” in effect a distributed delay line that physically spreads each pulse of sample. This novel approach to signal smoothing achieves just the right amount of smoothing for low-repetition rate LA-ICP-MS while extending washout for signals above background by only 4 seconds.
The combination of a fast washout cell from Laurin Technic, paired with the squid smoothing device, provides the ultimate in signal smoothing flexibility. The time constant of the standard squid is approximately 2.5 seconds FWHM, although the time constant can be shortened or extended if requested at ordering. Connections are made with contamination-free plastic or stainless steel push-in fittings.
The squid is constructed from PEEK and a special grade of nylon tubing selected with the assistance of customer sites. To achieve perfect washout down to background it is essential to have perfectly smooth transitions between the tubing and the connectors. Connections are made with contamination-free plastic or stainless steel push-in fittings.
The squid is not normally a source of contamination, but after extended ablation of samples such as lithium borate glasses, or samples containing large concentrations of volatiles such as mercury and arsenic, the tubing may absorb the volatiles and need to be cleaned. Some customers purchase two squids and use one in combination with a second set of carrier gas tubing for contaminating samples. Cleaning by rinsing the squid with dilute Citranox followed by a water rinse and drying has been shown to successfully eliminate contamination.