Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

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extended to include minke whales from the beginning

of the 1982–83 pelagic and 1983 coastal seasons.

0008 In the fishery of small cetaceans, harpoons, rifles,

nets, and driving methods are used. In the drive fish-

ery in the Faroe Islands, entire schools are driven into

an authorized whaling bay and killed by severing the

jugulars and arteries supporting the brain with special

knives. All stages in this organized hunt are regulated

by law. It is worth mentioning that there are no

professional whalers or whaleboats involved in this

whale drive, and the shares are distributed free to all

local inhabitants. No factory processing of the catch

occurs. For indepth descriptions of the various stages

of driving, beaching, killing, and butchering, see

Further Reading.

0009 The size of the driven schools varies and it can be

seen from the statistics that pilot whales occur in

Faroese waters with a cyclic periodicity of about

120 years. In the period from 1709 to 1999, the

school size was on average 139.8 whales (range

1–1200), with an average of 7.1 schools beached a

year (range 0–23), giving an annual average catch of

850 whales (range 0–4448).

0010 Regulations state that pilot whales must be

butchered and the shares removed within 1 h after

the shares have been allotted. According to the regu-

lations, the shares are given to the participants in the

drive and to local households in the district.

0011 The whales are butchered on the quay by those

receiving shares. The section of the whale which is

used is cut behind the head to the anus. First the

blubber is peeled off in transversal strips and placed

on the quay with the skin down so as not to soil the

blubber side. After that, the meat is removed and

placed on top of the blubber, and when the whole

whale has been butchered in this way, the shares are

then divided between those who have a share in the

same whale.

Food Uses and Products: Significance in

National Diets

0012 The different parts of the whale used for human

consumption in different parts of the world are listed

in Table 1. In general, the meat is used by all the

whaling countries, either raw or, more commonly,

prepared in some way. Some of these countries,

where edible fat has been in short supply, have also

developed national dishes using the blubber in differ-

ent ways. Finally, especially in Japan, national dishes

have been developed for nearly all parts of the whales,

except the backbone.

0013 In the Faroes both the meat and blubber of pilot

whales are utilized for human consumption. On aver-

age, 54% in weight of the animals is used, with the

amount of meat and blubber used being nearly equal.

On the beach, kidneys are taken, free, as anyone’s

share. The kidney is boiled fresh in salted water and

eaten at once. The share of meat and blubber is pre-

pared in different ways in the home. The traditional

and still the most common method for conserving the

household share is by salting or wind-drying. In the

last 25 years this method has been supplemented by

deep-freezing the products fresh or after some wind-

drying. Normally, however, very little of the meat and

blubber is frozen fresh, partly owing to limited freezer

space, and partly because the traditional methods are

thought to provide the most delicious result.

0014The different methods used to prepare the whale

products are discussed in the following two sections.

tbl0001Table 1 Preparation methods of the various parts of whales

used today for human consumption

Preparationmethod Part of whale Country

Raw Meat Japan

Gum meat Japan

Lung Japan

Skin with blubber Greenland

Boiled or fried in oil or water Meat Worldwide use

Blubber Japan, Faroe

Islands

Greenland

Tongue Japan

Ventral groove Japan

Kidney Faroe

Islands

Internal organs Japan

Lung Japan

Smoked Ventral groove Japan

Meat Japan

Salted dry or pickled Meat Japan, Faroe

Islands

Blubber Faroe Islands

Fin Japan

Ventral groove Japan

Dried by sun/wind Meat Japan, Faroe

Islands

Lactic acid Meat Iceland

Ventral groove Iceland

Wine-preserved Cartilage Japan

Data from Small-Type Coastal Whaling in Japan (1988) Report of

an International Workshop. Occasional publication number 27. Alberta,

Canada: Japan Social Sciences Association of Canada Fund to Promote

International Educational Exchange and Boreal Institute for

Northern Studies.

Data from Hansen C (1963) Nerissagssiornermik ilitsers

tit kalatdlit-nunnut

ngatitat. Den Grønlandske Handel. (Greenlandic cooking book.)

Nakitertitai.

Data from Skaale and Johannesen (1974) and Henriksen (1987): Skaale O

and Johannesen M (1974) Matur og Matgerð. Grønalı

ð.To

rshavn. (Faroese

cookbook.). Henriksen J (1987) G

ðar

ð.Go

ðaRa

ð. Klaksvı

k. (Faroese

cookbook.).

Data from Kristja

nson (1986) Kristja

nsson L (1986) N

ting Hvalafangs.In:

slenskir Sj

varhIttir, vol. 5, pp.70–79. Reykjavı

k: Bo

kau

tga

Menningarsjo

ðs.

3734 MARINE FOODS/Marine Mammals as Meat Sources

Whale Meat

0015 In general, most of the whale meat is eaten fresh

(worldwide), salted, wind-dried (Faroe Islands), or

sun-dried after being thinly sliced (Japan). In Iceland,

the ventral grooves and meat of baleen whales were

conserved in containers with lactic acid. (See Drying:

Drying Using Natural Radiation.)

0016 In the salting process, pieces of meat or blubber are

placed in dark containers, pressed together, and

covered in a brine of boiled water with a salt solution

in which a potato can float. After salting for at least

1 month, the meat is washed in water for 24–48 h

before being boiled in water, and the blubber is eaten

boiled or raw, unwashed (Iceland and the Faroe

Islands).

0017 When drying, whale meat undergoes a process of

fermentation combined with drying (the Faroe

Islands). The pieces of meat are sprinkled with salt

(12–24 h) after being cut into thinner pieces of about

50 cm in length and 10 cm in diameter. The surface is

smoothed, resulting in a quick stiffening of the sur-

face in the wind which prevents flies from laying eggs.

The pieces are hung up outside on the northern side of

the house, and are ready for boiling in salted water

after 3–4 weeks. Alternatively, when dried quite hard

after about 3 months it is eaten raw in thin slices. (See

Preservation of Food.)

0018 The above-mentioned means of food preservation

is only possible in the north Atlantic where the

climatic conditions are cold and windy. Moreover,

in the Faroes it is a means still commonly used for

preserving local sheep, fish, and geese.

0019 Whale meat and blubber are also smoked in both

Iceland and Japan.

Blubber

0020Very little blubber is frozen fresh. Nearly everything is

salted, either dry or in brine, as described above (the

Faroe Islands, Iceland) or wind-dried (Iceland). After

lying in salt for at least 1 month, preferably up to 3

months, the blubber is edible and conserved for years.

The skin and outermost layer of blubber is eaten raw

(Greenland), and elsewhere the blubber is boiled or

fried (Japan, the Faroe Islands, Greenland).

Significance in National Diet

0021For many years, pilot whaling has been essential to

the survival of the Faroese community. In modern

Faroese society an annual catch of approximately

2500 whales still represents 50% of the Faroese

meat production (equal to sheep and cow production)

and 25% of the Faroese meat consumption.

0022In former times, and still today, salted whale meat

and blubber has been used as food on board ships,

especially on smaller boats without freezers (the

Faroe Islands, Japan).

0023Furthermore, marine mammals are virtually the

only reserve for some Inuit communities in the

Arctic.

Chemical Composition and Nutritional

Value

0024Whale meat and blubber, most commonly used for

human consumption (Table 1), have a very high

nutritional value. The meat is an excellent source of

protein (Table 2), with a low fat content. Thus it

agrees well with western health recommendations.

(Refer to individual nutrients.)

tbl0002 Table 2 The chemical composition of whale meat, expressed per 100 g of meat

Component

n (number of samples) Meanvalue Standarddeviation Species

Protein (g) 20 25.0 0.7 Pilot whale

Fat (g) 20 1.0 1.4 Pilot whale

Carbohydrate (g) 20 0.5 0.6 Pilot whale

Sodium (g) 10 330 160 Pilot whale

Potassium (mg) 10 1630 350 Pilot whale

Calcium (mg) 10 10 0 Pilot whale

Magnesium (mg) 10 110 40 Pilot whale

Phosphorus (mg) 10 930 100 Pilot whale

Iron (mg) 10 51.9 19.4 Pilot whale

Zinc (mg) 10 6.7 1.0 Pilot whale

Copper (mg) 10 0.14 0.05 Pilot whale

Selenium (mg) 3 0.19 0.06 Pilot whale

Vitamin B

, thiamin (mg) 200 Narwhal

Vitamin B

, riboflavin (mg) 300 Narwhal

Vitamin A, retinol (mg) 100 Narwhal

Vitamin C, ascorbic acid (mg) 1 Narwhal

Data for protein-selenium from Poulsen (1995). Data for vitamins B and C from Jepsen (1983): Jepsen O (1983) Kostvurderinger over nlandske

devarer. FDB’s centrallaboratorium. Copenhagen: Forenede Danske Brugsbutikker’s Centrallab.

MARINE FOODS/Marine Mammals as Meat Sources 3735

Whale Meat

0025 Compared with other mammals and various fish

species, whale meat has a very high content of prac-

tically all types of macro- and microminerals. Of

particular note is the high content of selenium and

iron (Table 2). Selenium has an important role be-

cause it seems to prevent carcinogenic reactions, and

iron is required to meet the needs for growth, main-

tenance, and repair of tissues. The estimated safe and

adequate daily dietary intake of selenium for adults is

0.05–0.2 mg, and the recommended dietary allow-

ances (RDA) for iron for adults is 18 mg. Thus 100 g

of pilot whale meat a day will provide enough of these

two minerals. (See Fish Oils: Dietary Importance;

Fish: Dietary Importance of Fish and Shellfish;

Meat: Nutritional Value; Offal: Types of Offal.)

0026 Little information is available about the content of

different vitamins in pilot whales, but the meat from

narwhals is a good source of vitamins B

, and A.

Blubber

0027 Blubber is composed of practically pure fat (70–80%)

and water. However, the fatty acid composition is

very good (Table 3). Blubber has a high ratio of

polyunsaturated to saturated fatty acids (P:S value),

and the amount of eicosapentaenoic acid (EPA) and

docosahexaenoic acid (DHA) is high, compared with

various fish species, which are the main natural

sources of these fatty acids. EPA and DHA are prob-

ably the most important fatty acids in preventing

coronary heart disease. (See Fatty Acids: Dietary Im-

portance.)

Chemical and Microbiological Hazards

0028Despite the fact that whales are of extremely high

nutritional value, there are reasons for caution. The

meat can contain large amounts of heavy metals, such

as mercury and cadmium, and the blubber can be

contaminated with persistent, lipid-soluble synthetic

compounds such as pesticides and polychlorinated

biphenyls (PCBs) and halogenated aromatic hydro-

carbons in general. It is sometimes found that indi-

viduals carry a muscle mercury concentration of

6mgkg

1

. The normal level is however one-third

of this – about 2 mg kg

1

(Table 4). The proportion

of the total mercury which is present as the most

potent toxic species methylmercury is highly

variable among the individuals in the school, varying

from 24% to 86% in one school in 1978; the average

methylmercury component in samples from two

schools were however approximately 50%. Also cad-

mium may pose a threat to both individual whales

and also to consumers of pilot-whale livers and

kidneys. The concentration of the metals in the liver

are severalfold higher than in the muscle where in

individual instances concentrations approaching

250 mg kg

1

of cadmium and 600 mg kg

1

of mer-

cury have been detected. The content of mercury in

different parts of the pilot whale (Table 4) and exam-

inations of Faroe Islanders indicate that the estimated

long-term intake of mercury and cadmium from

eating whales may reach or exceed the recognized

critical level for negative or toxic effects in humans.

(See Cadmium: Toxicology; Mercury: Toxicology.)

0029Inspecting the mean values of total dichlorodi-

phenyltrichloroethane (DDT) and PCB in blubber

from pilot whale schools in the Faroes in 1987

and 1997 (Table 5) reveals the frequently observed

tbl0003 Table 3 Fatty acid composition in blubber from long-finned

pilot whales off the Faroe Islands

Fattyacid content (%)

Saturated fatty acids (S)

16.34

Monounsaturated fatty acids 60.45

Polyunsaturated fatty acids (P)

14.90

Polyunsaturated fatty acid fraction

Eicosapentaenoic acid (EPA) 1.20

Docosahexaenoic acid (DHA) 5.41

P/S is 0.91.

Data from Poulsen (1995): Poulsen M (1995) Froyskar

ðslutalvur

(Faroese Food Composition Tables.) Heilsufr ðiliga Starvstovan, pp.1–

25. Tœrshavn: Food and Environmental Agency.

tbl0004 Table 4 The total mercury concentration in various tissues of long-finned pilot whales off the Faroe Islands

Yearof sampling Tissue Number of samples Mean value (mg kg

1

) Standard deviation Reference (see Further Reading)

1977 Meat 20 2.1 1.2 Bloch et al. (1987)

1987 Meat 31 1.35 1.78 Caurant et al. (1993)

1997 Meat 28

1.7 Food and Environmental Agency (1976, 1978)

1987 Kidney 31 4.91 3.81 Caurant et al. (1993)

1987 Liver 40 84.1 92 Caurant et al. (1993)

1978 Blubber 20 0.69 Food and Environmental Agency (1976, 1978)

Three (in one instance four) pools from nine schools representing samples from a total of 417 individuals were analyzed. The mean values have been

adjusted to represent an ‘average’ school with respect to number of females and males, juveniles and adults.

3736 MARINE FOODS/Marine Mammals as Meat Sources

feature of mature females to excrete persistent or-

ganic pollutants and thus carry a lower body burden

than immature whales and mature males. A recent

study of the group of polybrominated diethylethers

(PBDE), also known as flame retardants, in blubber

samples revealed a widespread distribution of these

compounds also in pilot whales, and the same pattern

of elevated concentrations in the young as is seen with

PCBs and pesticides in general. The concentrations of

PBDE as well as PCBs, both the nonortho congeners

which are also known as the coplanar ones, as well as

the bulk of PCBs, are high (Table 6). In addition, the

concentration of polychlorinated dibenzo-p-dioxines

and -p-furanes, often referred to simply as dioxins,

are given for the adult whales sampled in Vestmanna

in 1996. Due to the scarcity of data, the distribution

of contaminants between the groups of adults in this

particular school should not be considered as typical.

What can cause changes in the relative distribution is

that the adult males are more transient members of

the school, and the males and females need therefore

not have common history regarding food and for-

aging area, which are both important parameters in

determining pollutant body burden. What may be

compared, regardless of the uncertainty between the

sexes, is the distribution of pollutants within the

groups. We note that the common PCBs, although

each one less toxic than the coplanar ones and the

dioxins in general, are still responsible for the highest

toxic load, expressed in toxic equivalents, and this is

due to the much higher concentrations. The toxic

equivalents are defined with reference to the most

toxic dioxin compound, 2,3,7,8-TCDD. It is apparent

that although this seveso-dioxin is assigned a toxic

equivalent value of 1, the 2,3,7,8-TCDD is only

accounting for less than 10% of the toxic effect

tbl0005 Table 5 Organochlorine concentrations in the blubber of long-finned pilot whales off the Faroe Islands

Ye a r o f

sampling

Sex Bodylength

(cm)

Standard

deviation

n whales n pods tDDT

mg/kg lipid

PCB as Aroclor

1254:1260 or1260

(mg kg

1

lipid)

CB153

(mg kg

1

lipid)

Mean Standard

deviation:

range

Mean Standard

deviation:

range

Mean Range

1987 im ,, 304 50 44 NA 37.2 26.9 47.8 29.5

1987 im << 362 68 15 NA 49.1 32.5 61.4 27.3

1987 ad ,, 431 28 113 NA 9.2 9.1 15.5 12.4

1987 ad << 546 48 11 NA 50.9 20.7 57.4 24.6

1997 im <<,, 356 85 173 10 15.9 10.6–23.5 35.1 18.4–45.0 3.7 2.0–4.7

1997 ad ,, 430 22 193 9 6.3 3.3–11.7 16.0 11.0–29.0 1.8 1.2–3.1

1997 ad << 547 25 54 9 17.7 10.6–25.4 38.2 24.5–52.0 4.1 2.6–5.7

tDDt ¼ p,p

-DDT þ p,p

-DDE þ p,p

-DDD þ o,p

-DDT.

Polychlorinated biphenyls (PCB) are given with reference to the commercial product; the 1987 data were quantified with a 1:1 mixture of Aroclor 1254 and

1260. The 1997 data were quantified as single congeners; however, for

reasons of comparision with the 1987 data, these were expressed as Aroclor

1260 units. The calculation of Aroclor 1260 units is based on regression

analysis in human samples which had been analyzed for PCBs both with an

Aroclor standard and with a single congener standard. For reasons of

tbl0006Table 6 Concentrations of polybrominated diethylethers (BDE),

polychlorinated biphenyls (PCB), also of the non-ortho congeners,

polychlorodibenzo-para-dioxin (PCDD), and polychlorodibenzo-

para-furanes (PBDF) in pilot whale blubber

ad ,, ad <<

Lipid % 79 % 83 %

(ngg

1

lipid) (ng g

1

lipid)

Te-BDE #47 529 862

Pe-BDE #99 209 292

Sum BDE

1.048 1.610

CB 153 1.500 2.700

Sum PCB

10.672 21.785

(pgg

1

lipid) (pg g

1

lipid)

PCB 77 770 420

PCB 126 340 310

PCB 169 620 530

TEQ sum coplanar PCB

40.6 36.5

TEQ sum PCB

180 390

TEQ sum PCDD/PCDF 12.9 10.0

TEQ, 2,3,7,8-TCDD 0.86 0.58

Sum BDE is the sum of 19 individual tetra, penta and hexa

bromodiethylethers.

Sum PCB is the sum of 61 congeners quantified using single congener

standards.

Sum of the three nonortho-substituted PCB congeners CB 77, 126, and

169.

The samples were taken in Vestmanna 27 June 1996; the analyses were

done on pooled samples of adult females (ad ,,) and males (ad <<), each

representing 19 and 8 animals respectively. The results are given in units

of ng g

1

lipid and pg g

1

lipid, depending on the range of concentrations

detected. The chlorinated compounds are also presented in toxic

equivalents (TEQs), using the conversion factors of the World Health

Organization.

MARINE FOODS/Marine Mammals as Meat Sources 3737

of the dioxins. (See Heavy Metal Toxicology; Pesti-

cides and Herbicides: Toxicology.)

0030 Based on different research work and the recom-

mended acceptable daily intake, Faroese health au-

thorities issued the following recommended intake

levels for the Faroese population in 1989:

0031 On average, adults should eat no more than 150–

200 g of whale meat per week. Pregnant women

should eat much less or, preferably, not eat whale

meat at all.

0032 Adults should eat no more than 100–200 g of

blubber per month.

0033 People should not eat entrails (liver, kidney, etc.)

from pilot whales.

0034 In 1998 the dietary advice was revised according to

new data on toxicity and contamination load and the

recommendations given were:

Diet Recommendation Concerning Pilot Whale

Meat and Blubber – Faroe Islands August 1998

0035 Blubber High PCBs contents in blubber lead us to

recommend that adults eat pilot whale blubber at

most once to twice a month.

0036 However, the best way to protect fetuses against

the potential harmful effects of PCBs is for pregnant

women not to eat blubber until they have given birth.

0037 Meat The mercury content of pilot whale meat is

high and is one of our main mercury sources. There-

fore we recommend that adults eat no more than one

to two pilot whale meals a month.

0038 Women who plan to become pregnant within 3

months, pregnant women, and nursing women

should abstain from eating pilot whale meat.

0039 Organs Pilot whale liver and kidneys should not be

eaten at all.

0040 The above recommendations are considered the

most advisable for the present. When new informa-

tion is acquired, this diet recommendation will be

revised accordingly.

0041 This recommendation is given by the following

Faroese authorities: Food and Environmental Agency,

Department of Occupational and Public Health, and

Chief Medical Officer.

0042 After the killing and before the butchering of the

carcasses, it is important that the beach is clean and

away from sewer outlets or the like. This is important

to avoid contamination by pathogenic bacteria. Most

often the meat is heated before eating, except for

wind-dried meat which is eaten raw (see above).

When eaten raw it is of utmost importance that

the meat does not contain pathogenic bacteria. The

drying circumstances must be suitable to avoid

the growth of such bacteria. (See Spoilage: Bacterial

Spoilage.)

Waste Product Utilization

0043According to Faroese law, all remains after a whale

drive must be removed within 24 h after the killing,

and the quay cleaned again. The remaining 46% of

pilot whales in the Faroes not used for consumption

consists of the skeleton, head, tail, and intestines.

Before the introduction of electric lighting in homes,

the heads were boiled down for lamp oil, and the

bones were used as fertilizer in the fields, a method

which is still used in Japan. In the Faroe Islands today,

the intestines are used by some as bait in line fishery,

and production of fertilizer from whale remains is

being considered.

See also: Cadmium: Toxicology; Drying: Drying Using

Natural Radiation; Fatty Acids: Dietary Importance; Fish:

Dietary Importance of Fish and Shellfish; Fish Oils:

Dietary Importance; Heavy Metal Toxicology; Meat:

Nutritional Value; Mercury: Toxicology; Offal: Types of

Offal; Pesticides and Herbicides: Toxicology;

Preservation of Food; Spoilage: Bacterial Spoilage

Further Reading

Bloch D, Hanusardo

ttir M, Davidsen A

and Kraul I (1987)

The Contamination of Mercury and Persistent Organo-

chlorines in the Marine Environment of the Faroe

Islands.Torshavn: IWC document SC/39/O 26.

Bloch D, Desportes G, Hoydal K and Jean P (1990) Pilot

whaling in the Faroe Islands July 1986–July 1988. North

Atlantic Studies 2: 36–44.

Borrell A and Aguilar A (1993) DDT and PCB pollution in

blubber and muscle of long-finned pilot whales from the

Faroe Islands. Report of the International Whaling

Commission (special issue)14: 351–358.

Caurant F, Amiard-Triquet C and Amiard J-C (1993)

Factors influencing the accumulation of metals in pilot

whales (Globicephala melas) off the Faroe Islands.

Report of the International Whaling Commission

(special issue) 14: 369–390.

Food and Environmental Agency (1976) Yearly Report.

Faroe Islands: To

rshavn.

Food and Environmental Agency (1978) Yearly Report.

Faroe Islands: To

rshavn.

Hansen C (1963) Nerissagssiornermik ilitsersu

tit kalatdlit-

nuna¨nut tu

ngatitat. Den Grønlandske Handel. (Green-

landic cooking book.) Nakitertitai.

Henriksen J (1987) Go

ðara

ð.Go

ðaRa

ð. Klaksvı

k. (Faro-

ese cookbook.)

Jepsen O (1983) Kostvurderinger over Grønlandske fødevarer.

FDB’s centrallaboratorium. Copenhagen: Forenede Danske

Brugsbutikker’s Centrallab.

Kristja

nsson L (1986) Ny

ting Hvalafangs. In: l

slenskir

Sja

varhættir, vol. 5, pp. 70–79. Reykjavı

´k:

kau

tga

Menningarsjo

ðs.

3738 MARINE FOODS/Marine Mammals as Meat Sources

Poulsen M (1995) Føroyskar Føðslutalvur (Faroese Food

Composition Tables.) Heilsufrøðiliga Starvstovan, pp.

1–25. To

rshavn: Food and Environmental Agency.

Skaale O

and Johannesen M (1974) Matur og Matgerð.

Grønalı

ð.To

rshavn. (Faroese cookbook.)

Small-Type Coastal Whaling in Japan (1988) Report of

an International Workshop. Occasional publication

number 27. Alberta, Canada: Japan Social Sciences

Association of Canada Fund to Promote International

Educational Exchange and Boreal Institute for

Northern Studies.

Market Research See Food Acceptability: Affective Methods; Market Research Methods

MASS SPECTROMETRY

Contents

Principles and Instrumentation

Applications

Principles and Instrumentation

F A Mellon, AFRC Institute of Food Research,

Norwich, UK

Principles

0001 Mass spectrometry is an extremely sensitive and spe-

cific analytical technique, capable of providing quali-

tative and quantitative analytical data on nanomolar

to attomolar amounts of analyte. It has been applied

successfully to a very wide range of analytical prob-

lems in the food and nutrition sciences. Mass spec-

trometers have become far more accessible, cheaper

to purchase and operate, and easier to use, especially

over the last decade. This is mainly a consequence of

the advent of compact, bench-top instruments, usu-

ally coupled to gas or liquid chromatographs. The

following article describes the basic theory of mass

spectrometry and the principal types of mass spectro-

metric equipment relevant to food and nutrition

analysis and research. Applications of mass spectrom-

etry and techniques of combined chromatography

mass spectrometry are covered in separate articles.

Mass Spectrometer

0002 All mass spectrometers comprise four main compon-

ents. First, an ion source, where sample molecules

may be ionized by a variety of means, second, a

mass analyzer that separates ions according to

their mass-to-charge ratio, m/z, third, a detector that

measures the abundances of the separated ions as an

electrical signal, and fourth, a recording device that

converts the detector signal into a form suitable for

further study and processing.

Ionization Techniques – Organic Mass

Spectrometry

0003Ionization of organic molecules may be accomplished

by a variety of techniques. The most common prac-

tical methods are described below.

Formation of Ions

0004Organic mass spectrometry

Electron ionization (EI) The analyte is vaporized

into the EI source and bombarded with 70-eV elec-

trons. The ion source chamber is maintained at a

vacuum of 10

3

Pa. A proportion of the energy of the

electron beam is transferred to the molecule, ejecting an

electron to generate a molecular ion (M



), the most

important ion in the mass spectrum (eqn (1)).

M þ e



! M

þ

þ 2e: ð1Þ

0005Excess electronic energy is also transferred to the

molecule during the ionization process and is rapidly

converted to internal vibrational energy. This energy

may be sufficient to induce bond cleavage in some

ions, generating fragment ions that may also decom-

pose. This is shown in the sequence of decompos-

itions of a hypothetical molecule ABCD (eqn (2)).

ABCD

þ

! ABC

þ D



! AB

þ C ! A

þ B:

ð2Þ

0006Rearrangement processes may also occur (eqn (3)).

ABCD

þ

! AD

þ

þ CB: ð3Þ

MASS SPECTROMETRY/Principles and Instrumentation 3739

0007 Most ions formed by EI have a single positive

charge (z ¼ 1), and m/z is then equivalent to the

mass of the ion. The way in which a molecule frag-

ment is determined by a number of factors that will

not be discussed here. Semiempirical rules for predict-

ing or rationalizing bond cleavages and rearrange-

ments can be found in several textbooks. The most

important consequence of the fragmentation process

is that it generates a characteristic, reproducible mass

spectrum that serves as a spectrometric ‘fingerprint’

of the analyte.

0008 Mass spectra are generally recorded in the form of

a line diagram (bar graph). Ion intensities are normal-

ized so that the largest peak in the mass spectrum, the

base peak, has an intensity of 100 units, and all other

ion abundances are expressed as a percentage of this

value. The low-resolution mass spectrum of caffeine

is shown in Figure 1.

0009 A molecular ion can be seen at m/z 194, and a

number of abundant fragment ions are also present.

In this example, the molecular ion is also the base

peak, although this is not always the case; strongly

favored fragmentations may yield abundant fragment

ions that are more intense than the molecular ion.

0010 Some molecules are difficult to analyze by EI mass

spectrometry for either or both of two main reasons.

They may fragment very readily, so that the molecular

ion is of very low abundance and therefore (in the

case of an unknown) difficult to assign. Alternatively,

the molecules may be involatile or thermally labile

and difficult or impossible to vaporize without

inducing thermolytic decomposition. Several ‘soft’

ionization methods are available for analyzing mol-

ecules that fall into this category. These techniques

are used to transfer analytes from the liquid or solid

phase to the gas phase and ionize them by mechan-

isms that impart minimal amounts of energy.

0011Chemical ionization (CI) CI is based on the reac-

tions of gaseous analyte molecules with an excess of

ions formed by electron bombardment of a reagent

gas. These reactions take place at high (relative to EI)

ion source pressures, typically in the range 10–150 Pa.

Typical reagent gases include methane and ammonia:

these generate CH

and NH

ions, respectively under

CI conditions. The reagent ions are present in large

excess (10

:1) relative to analyte molecules. The re-

agent ions generally react with analyte molecules M

by protonation (eqn (4)),

M þ NH

! MH

þ NH

: ð4Þ

Negative ion chemical ionization is also possi-

ble. Negative ion reagent gases include water. This

generates OH



ions and reacts by proton abstraction

(eqn (5)),

M þ OH



!½M  H



þ H

O: ð5Þ

A special case of negative ionization, electron capture

negative chemical ionization (ECNCI) is not strictly

CI. It is an electron capture process where low-energy

electrons generate radical anions (eqn (6)),

M þ eðthermalÞ!M



: ð6Þ

40 80

Relative intensity (%)

100

109

194

120

m/z ratio

160

165

200

fig0001 Figure 1 Low-resolution electron ionization mass spectrum of caffeine in bar graph format.

3740 MASS SPECTROMETRY/Principles and Instrumentation

In this case, the ‘reagent’ gas acts as a moderator,

slowing the electrons to the thermal energies where

the electron capture process become efficient. ECNCI

is particularly useful for determining analytes with

strong electron capturing properties, for example,

halogenated molecules such as dioxins. ECNCI can

yield much greater sensitivities and lower detection

limits in these cases.

0012 Positive and negative reagent ions may also react in

other ways. A range of gases are available for specific

applications. CI spectra usually contain intense pro-

tonated or negatively charged molecules and fewer

fragment ions than EI.

0013 Desorption EI and CI In conventional EI and CI,

analyte molecules are typically introduced into the

ion source via a heated probe or GC inlet. Desorp-

tion EI and desorption CI provide techniques for

obtaining mass spectra of less volatile, thermally

labile molecules by rapid heating whilst the samples

are very close to the electron beam or are immersed in

the CI plasma. These techniques are still used occa-

sionally but have largely been superseded by more

robust and efficient methods for analyzing involatile

molecules, as described below.

0014 Fast atom bombardment (FAB) and liquid secondary

ionization mass spectrometry FAB and liquid

secondary ionization mass spectrometry essentially

describe the same technique, and the terms can be

used interchangeably. FAB was the first ionization

technique to enjoy widespread success in analyzing

polar, labile, and large molecules, including peptides

and polysaccharides. The analyte in a viscous, low-

boiling liquid matrix, typically glycerol that is bom-

barded with a stream of atoms or ions, typically Xe

atoms or Cs

ions that have average translational

energies in the keV range. Abundant protonated

or cationized molecules, for example [M þH]

[M þNa]

and deprotonated ions, [M H]



, are

formed and detected in positive and negative

ion modes, respectively. Characteristic fragment ions

may also be formed.

0015 FAB enjoyed great and deserved popularity in the

1980s and helped to establish mass spectrometry very

strongly in the biological sciences. However, it has

generally been superseded by the more powerful, ver-

satile techniques of electrospray and matrix-assisted

laser desorption ionization.

0016 Electrospray ionization (ESI) and atmospheric pres-

sure chemical ionization (APCI) In ESI, the analyte

is dissolved in a suitable solvent, for example a 50:50

mixture of acetonitrile and water, and is pumped

through a narrow diameter stainless steel capillary

tube that is maintained at a voltage in the range of 1–

4 kV. This process generates a plume of charged liquid

droplets in atmosphere (the Taylor cone). A heated

(usually nitrogen) gas aids evaporation of the charged

droplets and helps break up clusters of analyte and

solvent ions. Analyte ions are generated from the

charged droplets by an evaporation mechanism. The

ions are conducted into the mass spectrometer vacuum

via a pumped nozzle-skimmer system (Figure 2).

0017A curtain of nitrogen gas, which also aids evapor-

ation of the charged droplets, prevents cluster ion

formation. The ions are sampled through an orifice

and enter the mass analyzer. ESI has revolutionized

mass spectrometry by enabling mass spectra to be

obtained routinely on polar, involatile molecules.

Even high-molecular-weight biomolecules can be

analyzed by ESI. Proteins, for example, yield a series

of multiply charged ions well within the mass range of

conventional mass spectrometers such as quadrupoles

or magnetic sector instruments. These signals can be

transformed mathematically to yield the molecular

weight of the sample (Figure 3).

0018APCI is closely related to ESI and often employs an

almost identical ion source. The only changes are the

addition of a discharge electrode and replacement of

the ESI spray probe with an APCI probe. In APCI,

flowing liquid, typically an HPLC eluent, that con-

tains the dissolved analyte(s) is conducted to a pneu-

matic nebulizer, where it forms a spray. As with ESI,

the spray is generated in atmosphere and is directed

towards a discharge electrode that is maintained at

1–4 kV. This is placed close to a small-diameter orifice

that leads to the high-vacuum mass analyzer region. A

pumped nozzle and skimmer arrangement removes

excess solvent molecules, and desolvated ions are

admitted to the mass analyzer, in a similar manner

to an ESI source. Reagent ions are generated from

solvent molecules in the electrical discharge near the

corona pin. These react with analyte molecules to

generate protonated or deprotonated molecules

([M þH]

or [MH]



), in a similar manner to con-

ventional CI.

0019APCI is more robust (being less prone to solvent or

solvent modifier effects) than ESI but is usually too

vigorous and energetic to yield useful data on fragile

biomolecules. However, it is very useful for determin-

ing molecules of low to intermediate polarity and is

capable of producing useful data on some quite polar

molecules, for example monoglycosides.

0020Matrix-assisted laser desorption Ionization

(MALDI) MALDI is one of the best techniques for

obtaining analytical data, including molecular

weight information, on medium and large biomole-

cules. The sample, in low concentration, is mixed

MASS SPECTROMETRY/Principles and Instrumentation 3741

with a concentrated solution of, for example, sinapi-

nic acid, on a metal target. The solution is dried, and

the target is introduced into the mass spectrometer

ion source vacuum. The sample plus matrix is irradi-

ated with a pulsed laser (typically a 327-nm nitrogen

laser). The matrix chosen should be sublimable and

be able to absorb and transfer energy at the laser

wavelength. The mechanism of desorption and ion-

ization is complex. It is thought that the matrix then

transfers sufficient transverse vibrational energy to

the sample molecules to desorb some of them with

very little excess energy for fragmentation. The tech-

nique is particularly useful for mass measuring large

and medium-sized biomolecules, especially peptides,

proteins, and DNA fragments, and generates

[MþH]

,[MH]



or adduct ions, [MþNa]

0021 Other ionization methods Several other methods

have been used to ionize organic molecules in the

past. For example, field ionization, field desorption,

and

252

Cf plasma desorption were once popular tech-

niques for analyzing otherwise intractable molecules,

such as biopolymers. These techniques are now

mainly of historical interest and have generally been

superseded by more practical, reliable and robust

methods, particularly ESI and MALDI.

0022 Inductively coupled plasma ion source (ICP-

MS) Inorganic mass spectrometry has increased in

importance in food and nutrition science through

applications in authentication, nutrient mineral me-

tabolism and toxicology. One of the principle tech-

niques of inorganic mass spectrometry, ICP-MS, is

based on the production of ions in a high-temperature

(6000–8000 K) atmospheric-pressure argon plasma

formed by a self-sustaining electrical discharge that

is induced by a high-frequency induction coil. This

plasma is capable of ionizing most elements in the

periodic table very efficiently. Samples are introduced

into the ion source in nebulized solutions flowing at

rates of 0.1 –1 ml min

1

. They are then ionized effi-

ciently by the high-temperature plasma. Alternative

sample introduction techniques, including electro-

thermal vaporization, laser desorption, hydride

generation, electrospray, and combined chromatog-

raphy/mass spectrometry, are also available.

0023The ionization efficiency is generally very high for

most nutrient and toxic elements. The plasma forms a

supersonic jet in the differentially pumped region

behind the sampling cone. Ions are introduced into

the vacuum of the mass analyzer via a series of differ-

entially pumped stages. A schematic diagram of an

ICP-MS ion source is shown in Figure 4.

0024Most ICP-MS instruments are based on quadru-

pole mass analyzers. However, high-resolution mag-

netic sector instruments are also available. These are

capable of resolving polyatomic interferences gener-

ated in the argon plasma that may have the same mass

To rotary pump

Skimmer

Nozzle

Ions to mass analyzer

High vacuum region

N2 drying gas

Atmospheric pressure region

LC or Syringe pump flow

3.5 kV

Spray

fig0002 Figure 2 Schematic diagram of an electrospray ionization source.

3742 MASS SPECTROMETRY/Principles and Instrumentation

as isotopes of interest, for example

and

. High-precision isotope ratio measurements

may also be conducted if multicollector magnetic

sector mass analyzers are employed.

0025 A major step forward has been the introduction of

collision cell technology to eliminate polyatomic

interference ions. These cells have been used with

quadrupole and magnetic sector instruments. The

important nutritional element selenium suffers from

an abundant interference peak from

in the

mass channel. This interference can be attenuated

considerably by charge exchange with H

in the colli-

sion cell.

0026ICP-MS is a rapid and useful multielement analysis

technique that is also capable of determining isotope

ratios in studies of trace element metabolism in

humans.

0027Thermal ionization mass spectrometry (TIMS) TIMS

is a well-established technique in inorganic mass

16860

100

16880 16900 16920 16940 16960 16980 17000 17020 17040 17060 17080 17100 17120 17140

Mass

650

693.6

706.9

737.7

771.3

808.2

848.6

893.2

942.9

998.2

1060.5

1131.3

1211.8

1305.0

100

700 750 800 850 900 950 1000

16951.8

1050 1100 1150 1200 1250 1300 1350 14501400

m/z

fig0003 Figure 3 Electrospray mass spectrum of horse heart myoglobin, showing the raw, multiply charged data (upper trace) and the

transformed spectrum (lower trace) showing the measured molecular weight of the sample.

MASS SPECTROMETRY/Principles and Instrumentation 3743