Dif­fe­ren­ces bet­ween DART and SICRIT® in Mass Spec­tro­me­try

When labs look for an am­bi­ent ion source for di­rect mass spec­tro­me­try, they ine­vi­ta­b­ly come across DART and SICRIT®. The key ques­ti­on then is: What are the dif­fe­ren­ces bet­ween DART and SICRIT®? – and most labs are loo­king for prac­ti­cal ans­wers, not just theo­ry. Both ion sources were de­ve­lo­ped to make di­rect mass spec­tro­me­try (Di­rect-MS) pos­si­ble, en­ab­ling fast, chro­ma­to­gra­phy-free ana­ly­sis of so­lids, li­quids, and ga­ses. But their de­sign and usa­bi­li­ty dif­fer in ways that stron­gly af­fect speed, re­pro­du­ci­bi­li­ty, and in­te­gra­ti­on.

This ar­tic­le ex­plains the core dif­fe­ren­ces bet­ween both am­bi­ent io­niza­ti­on so­lu­ti­ons, high­light­ing whe­re each fits into mo­dern lab work­flows, and why SICRIT® has be­co­me the more fle­xi­ble, re­pro­du­ci­b­le, and fu­ture-re­a­dy so­lu­ti­on for many ap­pli­ca­ti­ons.

What is DART?

DART, or Di­rect Ana­ly­sis in Real Time, is one of the ear­liest and most wi­de­ly ad­opted am­bi­ent io­niza­ti­on me­thods. It ge­ne­ra­tes me­tasta­ble spe­ci­es from a car­ri­er gas such as he­li­um or ni­tro­gen, which io­ni­ze ana­lytes po­si­tio­ned in the open air bet­ween the source and the mass spec­tro­me­ter. DART en­ables ra­pid, non-cont­act me­a­su­re­ments of so­lids, li­quids, or ga­ses di­rect­ly at at­mo­sphe­ric pres­su­re.

Key cha­rac­te­ristics of DART:

  • Uses no­ble ga­ses, ty­pi­cal­ly he­li­um at 3–5 L/min.
  • Open-gap geo­me­try re­qui­res the sam­ple to be po­si­tio­ned bet­ween the source and MS in­let.
  • Ele­va­ted tem­pe­ra­tures pro­mo­te de­sorp­ti­on and io­niza­ti­on.
  • Quan­ti­ta­ti­ve ana­ly­sis ge­ne­ral­ly re­li­es on in­ter­nal stan­dards

Ap­pli­ca­ti­ons in­clude fast scree­ning in fo­ren­sics, phar­maceu­ti­cal qua­li­ty con­trol, and food safe­ty.

Sche­ma­tic Dia­gram Of A DART Ion Source
Cre­dits: Rb­co­dy, CC BY-SA 4.0, via Wi­ki­me­dia Com­mons

What is SICRIT®?

SICRIT®, or Soft Io­niza­ti­on by Che­mi­cal Re­ac­tion in Trans­fer, is a mo­dern ion source tech­no­lo­gy ba­sed on dielec­tric bar­ri­er di­schar­ge io­niza­ti­on wi­thin a flow-th­rough ca­pil­la­ry. The source is moun­ted di­rect­ly at the mass spec­tro­me­ter in­let, whe­re vo­la­ti­le or va­po­ri­zed ana­lytes are drawn in by the va­cu­um and io­ni­zed on their way into the sys­tem by me­ans of a ring-shaped cold plas­ma. This in­di­rect io­niza­ti­on pro­cess en­su­res soft io­niza­ti­on, and an ef­fi­ci­ent ion trans­fer. The uni­que geo­me­try en­ables a wide ran­ge of ap­pli­ca­ti­ons on top of di­rect MS.

Key cha­rac­te­ristics of SICRIT®:

  • Ope­ra­tes with va­rious ga­ses, in­clu­ding am­bi­ent air, wi­t­hout con­su­ma­bles.
  • Flow-th­rough geo­me­try sup­ports re­pro­du­ci­b­le ion trans­fer.
  • Gas-tight con­fi­gu­ra­ti­on en­ables con­trol­led sam­ple in­tro­duc­tion.
  • Com­pa­ti­ble with LC, GC, SFC, au­to­sam­plers, ro­bo­tic plat­forms, and MS ima­ging.
  • Mo­du­lar set­up al­lows ana­ly­sis of so­lids, li­quids, and ga­ses via di­rect de­sorp­ti­on or con­nec­ted mo­du­les.
  • Low power con­sump­ti­on (~5 W) and com­pact de­sign enable por­ta­ble or in­line use.
Sche­ma­tic of the SICRIT® Ion Source

Ap­pli­ca­ti­ons ran­ge from en­vi­ron­men­tal mo­ni­to­ring to cli­ni­cal dia­gno­stics, pro­cess con­trol, and ad­van­ced re­se­arch stu­dies.

Key Dif­fe­ren­ces Bet­ween DART and SICRIT®

Pa­ra­me­ter DART SICRIT®
Io­niza­ti­on Prin­ci­ple Open-air io­niza­ti­on via me­tasta­ble helium/nitrogen spe­ci­es Dielec­tric bar­ri­er di­schar­ge via ring-shaped cold plas­ma io­niza­ti­on
Car­ri­er Gas Re­qui­re­ment He­li­um (3–5 L/min) or Ni­tro­gen Any car­ri­er gas, in­clu­ding am­bi­ent air; no con­su­ma­bles
Sam­ple Geo­me­try Open gap; Sam­ple must fit bet­ween source and MS No size rest­ric­tions; re­mo­te sam­pling pos­si­ble
Quan­ti­ta­ti­on Re­qui­res in­ter­nal stan­dards Head­space, SPME, and di­rect quan­ti­ta­ti­on (de­di­ca­ted mo­du­les re­qui­red)
In­te­gra­ti­on No LC/GC/SFC in­te­gra­ti­on Com­pa­ti­ble with LC, GC, SFC, au­to­sam­plers, ima­ging set­ups (de­di­ca­ted mo­du­les re­qui­red)
Mass Spec com­pa­ti­bi­li­ty Bru­ker Sys­tems only Ven­dor in­de­pen­dent
Mo­bi­li­ty & Foot­print Re­qui­res gas cy­lin­ders; high power; li­mi­t­ed por­ta­bi­li­ty Small foot­print; ~5 W power; sui­ta­ble for por­ta­ble or in­line use

When to Choo­se DART

DART re­mains a prac­ti­cal op­ti­on for straight­for­ward, open-air ana­ly­ses whe­re mi­ni­mal set­up and im­me­dia­te re­sults are prio­ri­ties. It fits well in ap­pli­ca­ti­ons such as fo­ren­sic scree­ning, coun­ter­feit drug de­tec­tion, or sur­face ana­ly­sis, whe­re qua­li­ta­ti­ve in­for­ma­ti­on is suf­fi­ci­ent and quan­ti­ta­ti­on is not re­qui­red. La­bo­ra­to­ries with exis­ting Bru­ker sys­tems are able to use the DART ion source ef­fec­tively for ra­pid, point-of-use checks or quick sam­ple com­pa­ri­sons wi­t­hout ex­ten­si­ve in­te­gra­ti­on needs.

When to Choo­se SICRIT®

SICRIT® is the pre­fer­red choice when work­flows de­mand high re­pro­du­ci­bi­li­ty, quan­ti­ta­ti­ve ca­pa­bi­li­ty, and in­te­gra­ti­on with com­ple­men­ta­ry ana­ly­ti­cal sys­tems. It is par­ti­cu­lar­ly sui­ted for la­bo­ra­to­ries per­forming con­ti­nuous or au­to­ma­ted me­a­su­re­ments, such as en­vi­ron­men­tal mo­ni­to­ring, cli­ni­cal scree­ning, or pro­cess con­trol, whe­re sta­ble ope­ra­ti­on and low main­ten­an­ce are es­sen­ti­al. Re­se­arch and de­ve­lo­p­ment labs be­ne­fit from its com­pa­ti­bi­li­ty with LC, SFC, GC, and MS ima­ging, al­lo­wing fle­xi­ble swit­ching bet­ween ana­ly­ti­cal mo­des wi­t­hout re­con­fi­gu­ra­ti­on. SICRIT® also of­fers ad­van­ta­ges in high-th­rough­put test­ing, vo­la­ti­le com­pound ana­ly­sis, and set­ups re­qui­ring por­ta­ble or in­line ion sources, whe­re gas in­de­pen­dence and com­pact de­sign im­pro­ve ef­fi­ci­en­cy and re­lia­bi­li­ty.

Con­clu­si­on

DART re­mains a well-es­tab­lished so­lu­ti­on for ra­pid, di­rect ana­ly­sis in open-air scree­ning. SICRIT®, ho­we­ver, pro­vi­des a more ver­sa­ti­le and fu­ture-ori­en­ted ap­proach, com­bi­ning broad sys­tem com­pa­ti­bi­li­ty, quan­ti­ta­ti­ve per­for­mance, and re­pro­du­ci­b­le re­sults. Its ad­ap­ta­bi­li­ty to au­to­ma­ted, in­te­gra­ted, and high-th­rough­put en­vi­ron­ments makes it the more prac­ti­cal choice for la­bo­ra­to­ries ai­ming to meet mo­dern ana­ly­ti­cal de­mands.