LA-ICP-MSh

Analytica Chimica Acta 635 (2009) 6–21 Contents lists available at ScienceDirect Analytica Chimica Acta journa l homepage: www.e lsev ier .com/ locate /aca Review Role of laser ablation–inductively coupled plasma–mass spectrometry in cultural heritage research: A review Barbara Dipartimento a r t i c Article history Received 25 A Received in re Accepted 22 D Available onl Keywords: Laser ablation plasma–mass Cultural heritage Elemental analysis Archaeology Archaeometr Trace elemen these requirements exhibiting comparably strong analytical performance in trace element determination. This review intends to show through the applications found in the literature how valuable is the contri- Contents 1. Intro 2. Lase 3. Obsi 4. Glass 5. Cera 6. Hum 7. Writ 8. Meta 9. Misc 9.1. 9.2. 9.3. 10. Fina Refe ∗ Correspo E-mail ad 0003-2670/$ doi:10.1016/j y ts bution of LA–ICP–MS in the investigation of ancient materials such as obsidian, glass, pottery, human remains, written heritage, metal objects and miscellaneous stone materials. Themain issues related to cultural heritage investigation are introduced, followed by a brief description of the features of this technique. An overview of the exploitation of LA–ICP–MS is then presented. Finally, advantages and drawbacks of this technique are critically discussed: the fit for purpose and prospects of the use of LA–ICP–MS are presented. © 2008 Elsevier B.V. All rights reserved. duction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 r ablation–ICP–MS: a short overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 dian . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 artifacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 mics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 an remains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 ten heritage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 ls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 ellaneous materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Stone materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Pigments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Stuccoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 l considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 rences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 nding author. Tel.: +39 031 2386424; fax: +39 031 2386449. dress: barbara.giussani@uninsubria.it (B. Giussani). – see front matter © 2008 Elsevier B.V. All rights reserved. .aca.2008.12.040 Giussani ∗, Damiano Monticelli, Laura Rampazzi di Scienze Chimiche e Ambientali, Università degli Studi dell’Insubria, via Valleggio 11, 22100 Como, Italy l e i n f o : ugust 2008 vised form 18 December 2008 ecember 2008 ine 31 December 2008 –inductively coupled spectrometry a b s t r a c t Cultural heritage represents a bridge between the contemporary society and the past populations, and a strong collaboration between archaeologists, art historians and analysts may lead to the decryption of the information hidden in an ancient object. Quantitative elemental compositional data play a key role in solving questions concerning dating, provenance, technology, use and the relationship of ancient cultures with the environment. Neverthe- less, the scientific investigation of an artifact should be carried out complying with some important constraints: above all the analyses should be as little destructive as possible and performed directly on the object to preserve its integrity. Laser ablation sampling coupled to inductively coupled plasma–mass spectrometry (LA–ICP–MS) fulfils B. Giussani et al. / Analytica Chimica Acta 635 (2009) 6–21 7 1. Introduction Cultural heritage is of outstanding interest in the studyof human civilization. Artifacts are a precious inheritance from past genera- tions as the cultural bac they potent torians to u Themod interdiscipl formedby t artifacts top studied obj such as dati tion, use, or humans wit thediet, nut differently. Among o vide inform Much effor destructive unique and the damage faced when The tota archaeomet fragments b contaminat sis. Themea sample (pos In some surements sub-sampli measureme Cultural rials. A suita quantitative nitude in di Moreove (typically te position cou clay and tem Several a actually app of cultural h spectroscop [2], electron beam analy sion and pr neutronact for the cha amounts (s enhance an led to the in tively coupl of cultural h In the LA–ICP–MS ing its adva This tech logical mat archaeologi written her A brief i critical feat chema ation ent hara iscus cient and tion give er ab useo lasm sic id high le fo ue h inves inst rted sed eam win 0�m ed (a er p men ccor r tim obs ting t criti nd tr section. The reader is remanded to other publications for a l discussion of inductively coupled plasma–mass spectrom- ee, e.g. [12]). The reader is also addressed to review papers ted to LA–ICP–MS for a more detailed discussion [13–16]. cerning the wavelengths, the fourth and fifth harmonic Nd–YAG laser were applied to the investigation of cul- eritage objects. Thesewavelengths are obtained quadrupling m) and quintupling (213nm) the fundamental Nd–YAG ngth (1064nm). The great majority of the researches pre- in this review used the 266nm wavelength, while the fifth nic, 213nm laser was used in less than ten papers. eneral, lasers with even lower wavelength were employed pling devices for ICP–MS, like the so-called excimer lasers: on–fluorine operating at 193nm and the fluorine at 157nm. orted that shorter wavelengths (especially 213 and 193nm) y convey information about the historical, social and kground in which they were created. In several cases ially represent the only way for archaeologists and his- nderstand past populations. ern approach to the studyof cultural heritage is strongly inary. At its most basic, stylistic examinations are per- hearchaeologist orhistorianof art inorder to classify the ologically or stylistically by comparison with already ects (e.g. published collections). However, enquiries ng, provenance of raw materials, technology of produc- also questions concerning the relationship of ancient h the environment (which provide information on, e.g. rition, health, andpathologyof people) need to be faced thers, elemental quantitative compositional data pro- ation that greatly contributes to address these issues. t has been done in the last decades towards non- facilities, as the heritage that survives from the past is irreplaceable. It should be highlighted that minimizing to the investigated sample is not the only issue to be dealing with precious ancient objects. l sample amount is a major concern in the field of ry for reasons of sample preservation. Small sample eing difficult to handle potentially increase influence of ion and therefore compromise the quality of the analy- surement shouldbenon-destructive, allowing the same sibly very small) to be analyzed by other techniques. cases (e.g. for authentication purposes) the mea- should be done directly on the object without any ng, so investigators have to find a way to perform in situ nts. heritage objects could be constituted of different mate- ble analytical technique should allow the simultaneous determination of elements in different order of mag- fferent matrices to ensure a high throughput. r a good spatial resolution, laterally and in-depth ns of microns in both cases), is required since the com- ld be inhomogeneous (e.g. pottery fragments in which per particles are present). nalytical techniques meet such requirements and were lied to the investigation of the elemental composition eritage objects. In particular, laser induced breakdown y (LIBS [1]), secondary ion mass spectrometry (SIMS probe X-ray microanalysis (EPXMA see, e.g. [3]) ion tical techniques (IBA) like proton induced X-ray emis- oton induced gamma-ray emission (PIXE and PIGE [4]), ivation analysis (NAAmethods [5–7])were all employed racterization of both major, minor and trace element ee also [8,9]). Around 15 years ago, the endeavor to alytical performances in trace element determination troduction of laser ablation sampling coupled to induc- ed plasma–mass spectrometry (LA–ICP–MS) in the field eritage characterization (see [10]). present paper an overview of the exploitation of in the field of cultural heritage is presented, highlight- ntages and drawbacks as an analytical probe. nique has been used for the investigation of archaeo- erials such as bones and teeth, obsidians and glasses, cal ceramic, semiprecious stones, metal objects and itage. ntroduction on the technique is given, reviewing the ures, their effect on analytical performances and the Fig. 1. S laser abl instrum itage c then d ian, an objects applica itage is 2. Las The pled p Theba ble of availab techniq direct The is repo in a clo laser b parent and 10 remov The las the ele sured a field o sample for set The cells a of this genera etry (s dedica Con of the tural h (266n wavele sented harmo In g as sam the arg It is rep tic representation of the instrumental setup commonly employed for coupling to ICP–MS. al modifications introduced in the field of cultural her- cterization. The researches published in this field are sed divided according to the investigatedmatrix: obsid- glass, pottery, human remains, written heritage, metal miscellaneous materials. A critical overview of the of LA–ICP–MS in the characterization of cultural her- n in the closing of the paper. lation–ICP–MS: a short overview f laser ablationasa samplingdevice for inductively cou- a–mass spectrometry was first introduced by Gray [11]. ea is to combine adirect solid introduction systemcapa- spatial resolution with the highest sensitivity detector r inorganic analysis. Not surprisingly, this hyphenated as developed into an exceptional instrument for the tigation of the elemental composition of solid samples. rumental configuration which is most often employed in Fig. 1. Basically, the sample to be analyzed is placed chamber (called the ablation chamber or cell) and the is focused onto the sample surface through a trans- dow (typical diameter of the focused beam between 10 ). A flow of argon or helium transports the material blated) by the laser out of the cell to the plasma torch. roduced particles are then decomposed in the plasma, ts ionized and the generated ions separated and mea- ding to the mass analyzer used, i.e. quadrupole, sector e of flight. The cell is usually x, y, z moveable and the erved by a microscope through the transparent window he ablation position. cal features of LA–ICP–MS, i.e. the type of laser, ablation ansfer line, will be briefly addressed in the following 8 B. Giussani et al. / Analytica Chimica Acta 635 (2009) 6–21 lead to enhanced sensitivity and precision due to the production of smaller particles (see [17–21] for a comparison between laser wavelengths). A solid state 193nm laser was also introduced and is now commercially available [22,23]. All of these lasers have pulse duration in millijoule, l GWcm−2. N tion has a m ([24–26]). I order of 10 particles di atomized in some hund Moreover, f ric samplin matched ca [30,31]. Sur of cultural h lasers are n tion for lase The me parameters summarize Thepref gle spot ont when comp The abla analytical p antee the c the particle designed an cell to be us mogeneitie are investig of the parti low analysi desirable fo opments in that can be larly intere enable the sampling. N cells is rare silverware a ablate both latter case, line as in th membrane ing instrum andWanne tem for aut system, wh mentations beam, so th shape of the The aero torch by a fl ferred, altho shortwavel the length shapes regi registered [ tigation of and Robert type spray and stabiliz spray chamber prior to the ICP torch for stabilizing the signals. It is claimed that such a modification could remove larger parti- cles that are responsible for plasma instability. If this is the case, such an apparatus could lead to biased results as the aerosol com- n is . aero plasm etri to r esen fun e res ve g to t prese ascri nspo and libra wit le. B ndar rnal ecisi anda y far ICP–M l her d th lasse sults als. idia idian (volc al ch to gr .g. [5 ir ha conc r pre che nt ar of th for re tory g to ected sam gme ] or r gth ally ant a nted der [ ned b mpl rform mma uent . It sh ce co the range of nanoseconds, energies per pulse up to some eading to typical fluencies of some J cm−2 and power of evertheless, it was demonstrated that the pulse dura- uch stronger influence on the beam—solid interaction n particular, ultra short pulse duration, typically in the 0 fs, leads to the production of ultra-fine aerosols with ameter of a few tens of nanometers which can be easily the plasma. These lasers have typical pulse energies of reds of microjoule and power in the order of MWcm−2. emtosecond ablation was shown to lead to stoichiomet- g [27–29] and recent studies suggest that non-matrix libration is feasible with femtosecond laser ablation prisingly, this setup has never been applied in the field eritage characterization, possibly because femtosecond ot yet featured in commercially available instrumenta- r ablation–ICP–MS. rits and drawbacks of the different lasers and laser on the investigation of different kinds ofmaterialswere d in a recent paper by Koch and Günther [32]. erred ablation pattern consists of drilling a hole on a sin- o the surface, even though line scans are also performed ositional changes across layers are investigated. tion cell also plays an important role in defining the erformances of the system. In particular, it should guar- omplete (and for some application, fast) transport of s out of the cell. Several different ablation cells were d tested (see [33] and references therein). The kind of ed depends on whether the investigation of fine inho- s is sought or, on the other hand, homogenous samples ated. In the former case, a cell ensuring a fast removal cles is required to warrant high spatial resolution with s time, whereas a certain degree of mixing could be r homogenous samples (see [34–39] for recent devel- cell design). In particular, open cell designs, i.e. cells directly placed onto the sample surface, are particu- sting for the investigation of cultural heritages as they analysis of samples up to several decimeters without otwithstanding this important feature, the use of open ly reported: Devos et al. [40] used it to directly analyze nd Smith et al. [41] developed an open cell to directly pigments and support mediums in paintings. In the the ablated material was either directly analyzed on- e standard configuration of Fig. 1, or collected onto a which was subsequently analyzed. A further interest- ental development was fostered by Devos et al. [40] r et al. [42]. The authors independently developed a sys- omatically focusing the sample surface. Such autofocus ich was subsequently featured in commercial instru- , enables to automatically focus the image and the laser e focusing is reliably performed independently of the sample and the operator. sol is transferred from the ablation cell to the plasma ux of argon or helium, with helium being greatly pre- ugh its use may lead to substantial benefits only when engths (e.g. 213nm) are used [43–45]. It is reported that and diameter of the transfer line influence the peak stered in the ICP–MS but no losses of material were 34]. Modifications in the transport line for the inves- cultural heritage are reported by Habicht-Mauche [46] son et al. [47]. The former inserted a modified Scott- chamber to homogenize the laser-produced aerosols e the signal. Robertson et al. placed a bead-impact positio [27,28] The in the microm leading ions pr Two reliabl sentati relates not re and is the tra plasma The ca dealing availab the sta an inte and pr solid st being b in LA– cultura rials an NIST g rate re materi 3. Obs Obs flows materi green (see, e The tured ( rock fo The differe source tance the his huntin be coll The ing fra [52–56 ical len margin import bemou ple hol shorte A co waspe ing fro constit before and tra size dependent at least in the case of brass and glass sol is then atomized and the generated atoms ionized a. This process may be incomplete, meaning that big, c particles may not be entirely ionized in the plasma educed sensitivity and/or preferential generation of the t in the small particle fraction (see, e.g. [48,49]). damental issues undermine the possibility of achieving ults in LA–ICP–MS determination, namely the repre- eneration of ions and the quantification step. The first he possibility that the ions formed in the plasma are ntative of the elemental composition of the sample bed to processes taking place during the ablation step, rt of the aerosol or the vaporization–ionization in the is usually referred to with the term ‘fracti